Can't Take Anything with You

"Reese: Nothing dead will go. Cop: Why not? Reese: I don't know! I didn't invent the thing!"

- Terminator

Time Travelers are often prevented from bringing along any modern technology when they go back in time. When they arrive in the past, they have to rely on the things available during that time period.

The reasons for this vary. Sometimes the time travelers simply want to avoid changing the timeline too much, and they realize that, say, leaving a modern gun behind in the middle ages could create all sorts of problems. Other times it's due to a limitation of the Applied Phlebotinum used to travel through time. In the latter case, the time traveler often arrives naked and has to find clothing somewhere. In other cases, the time travel may simply have been a surprise and they weren't prepared.

Sometimes the inverse is seen, where it's not possible to take anything from the past back to the future. (Sometimes this is justified by the claim that, for the object, the future doesn't exist yet.) Since it's otherwise not much of a dramatic limitation, this version usually only comes up in stories where a time-traveler is trying to save something (or someone) from being destroyed in the past.

See also Alien Non-Interference Clause.

Anime and Manga

 * of Mahou Sensei Negima solves this by improvising with what she has in the current timeline. She still ends up being a genius inventor.

Film

 * Biggles adventures in time has the 'time twin' travelling with whatever (including people) they were touch, resulting in the main character arriving in a french nunnery in only a towel.
 * Terminator is probably the most famous example of the "arrives naked" version. However, the titular killer robots are able to travel back in time because they're covered in living tissue. Presumably, the liquid metal that more advanced models use is able to mimic living tissue closely enough to work.
 * Averted in the third movie, where the T-X has an energy weapon built under her skin.
 * In the pilot episode of The Sarah Connor Chronicles, the human resistance gets around this by sending an engineer back to the 1960s, where he builds a plasma rifle and time machine and stashes them in a bank vault.
 * And one of the Dark Horse series of Terminator comics had a group of T-800s sent back to the past accompanied by a very unfortunate human in whose abdomen they'd surgically implanted future weapons prior to coming back. They ripped him open upon arrival and were good to go, rayguns-wise. Why Skynet doesn't do this more often (or just wrap the weapons in synthetic flesh, the same way it does the T-800 exoskeletons) is unexplained.
 * 12 Monkeys
 * In the movie Timeline, the time travelers make sure not to bring anything modern back. In the original book, they bring translator earpieces along, but no other modern technology.
 * In the third Teenage Mutant Ninja Turtles movie, the magic scepter that was causing the time travel caused the people on each end of the time warp to switch places, with all their possessions staying in their own time. Michelangelo notices this when the Japanese nobleman appears in April's clothes, and makes a point of donning some trunks before he and the other turtles go back in time to retrieve April so that the person he switches with doesn't arrive naked.

Literature

 * Henry in The Time Traveler's Wife, who has a disease that causes him to spontaneously time travel. He cannot bring anything that is not part of him, like clothes, money or even dental implants.
 * In The Pendragon Adventure, the Travelers never bring anything from one territory to another, in fear of destabilizing the territories.
 * Doomsday Book and To Say Nothing of the Dog, by Connie Willis use the reversed version: time travelers can bring things from the future to the past, but not the other way round.
 * And, of course, a cat, because
 * In the Discworld book Night Watch, it's physically impossible for time travelers to take anything with them that doesn't belong in the destination time. Thus, a character who's changed his clothes while back in time will return to the future naked, it's a good idea to eat when you get back because the food you ate then stays there, et cetera. (This is not, in fact, always true—one of the time travelers brought his armor with him—but it's a very useful lie. The question seems to be one of power source.)
 * In Spider Robinson's Time Pressure, the time traveler arrives naked (except for her computer headband thing) and bald because of the limitations of the time machine. Time travel in some of the author's other books has similar limitations, such as an inability to bring living and nonliving things at the same time.
 * Wouldn't that also mean she returns without fingernails?
 * In Alastair Reynolds' novel Century Rain a force-field prevents travelers to the alternate-1950s earth from bringing through any complex technology at all - a big problem since it opens underground. They manage to get a jackhammer through by disassembling it and reassembling it on the other side, and running a hose through the field to an air compressor.
 * The first Doom novel has this, not when time-travelling, but when teleporting. The characters worry about whether it includes things like intestinal flora.
 * In a spin on this, the Old Kingdom of Garth Nix's Abhorsen trilogy is hostile to modern technology. Things that work in Ancelstierre, like telephones, machine guns and cars, cease to function once they get north of the border—or even just close to the border, if the wind is blowing from the north. Things made by machines also tend to fall apart. As a result, travelers to the Old Kingdom have to be prepared to bring only things made by hand, and the border guard know how to use swords and bows as well as firearms.
 * A similar version happens in Vernor Vinge's A Fire Upon the Deep. All sorts of amazing technology works when you're in the outer parts of the Milky Way galaxy, but as you travel inwards they will begin to fail in order of most advanced, as well as faster than light engines working less and less efficiently until failing entirely as well. Eventually, as you get close to the center, even higher brain functions begin to fail.
 * The Company Novels by Kage Baker use the reversed version: time travel is only possible into the past, and things of the past can't be carried back to the present (their future). The Company gets around this using a very, very elaborate Write Back to the Future system.
 * Though it involves dimensional travel instead of time travel, in The Great Game series by Dave Duncan, Strangers can't take anything with them to other worlds. This includes not only their clothes, but dental fillings, prosthetics, and possibly the contents of their stomachs.
 * Normally averted in Time Warp Trio. However, when they go back to the time of the cavemen with the intention of bringing back modern tech, they're left with nothing but their glasses, hat, and a straw.
 * This is because they tried to take too much back. Also, another book mentions trying to take too much knowledge from the future to the present can be bad.
 * Subverted in Robert Charles Wilson's The Chronoliths, where people don't travel in time, but a future leader sends back giant monuments to his victories from the future. These monuments are also extremely destructive weapons ("city killers") when they arrive.
 * Time travel is a major part of the plot in the sixth Artemis Fowl book. Due to the extremely unstable nature of the time stream, and the fact that the demon sending them back in time (No. 1) is a novice, he recommends that Artemis and Holly strip down, lest your clothing fuse to your skin. They are both understandably embarrassed, but manage to strip down to their underwear (Artemis is wearing red Armani boxers and Holly is wearing a standard issue LEPrecon one-piece).
 * Their embarrassment forms part of the Unresolved Sexual Tension between the two in this book.
 * In Dinoverse no one can take anything with them. Including their bodies. Instead the bodies of these intrepid time travelers fall into comas and their minds go back and possess the bodies of large, complex vertebrates - as the series' title suggests, everyone who time travels in the series ends up in a dinosaur. When they get to go home, each character again can't take anything with them, although in one case when a human and an allied dinosaur died in the same instant at the same place having the same kind of self-sacrificial goal, both their minds ended up sharing the human's body. Sadly, this is never fully explored.
 * The Dinosaur Cove series is like this. The kids can't bring anything back to the present with them. They can take their info gadgets back in time with them, though.

Live Action TV

 * The early Red Dwarf episode "Stasis Leak" had an inversion where the crew could take things to the past fine, but couldn't bring anything back with them. (A bar of soap used to try it out crumbled to dust; the implication was that—at least using the stasis leak method—anything brought Xty years into the future instantly aged Xty years.) When Rimmer says he wants to bring his past self back, the Cat agrees for once. (Rimmer takes a few moments to figure this out.)
 * Sam in Quantum Leap is never able to take anything with him during his leaps for a damn good reason: He Body Surfs through time instead of physically going back.

Tabletop Games

 * In the Forgotten Realms, items being sent back in time won't make it if they are more technologically advanced than the destination time period. The same goes for spells. It's also impossible to take anything from the past back to the future with you.

Video Games

 * In the text adventure game Time Zone, any object taken back to a time before it was invented vanishes from existence.
 * In Day of the Tentacle, the damaged time machine cannot send living creatures and larger objects, so the player has to find ways around this problem, such as putting a hamster in a freezer and then microwaving it in the future, and putting a sweater in the dryer with 200 years' worth of quarters (which shrinks to doll-size).
 * In Pokémon Gold and Silver games, you can only trade first gen Pokemon with attacks that debuted in RBY when you get the time machine trader to work.
 * Braid probably qualifies for this; you literally can't take anything with you that isn't made immune to fluctuations in the time-stream, and this also applies to any creature (including yourself) that isn't insulated against the time-stream. While convenient in some ways  it's also rather awkward in others
 * The Styx Time Gate in the Star Ocean series prevents anyone from taking modern technology (or indeed, anything more than clothes) into the past. It's never explained why this is the case, or what happens if you try.
 * The Japanese guide books explain that it is not technology per se that is blocked, but rather metallic objects. The Time Gate is an electromagnetic phenomenon, and metal or electronic objects would interfere with its operation much like when a person wears metal jewelery during an MRI scan. Carry metal or electronics with you, and at best you'll arrive in a different time and place from where you intended. At worst you'll be dead.
 * The cardinal rules of time travel in The Journeyman Project, besides not interacting with anyone not from one's own time, is not taking any important items or leaving any items in different time periods. Stealing bolt cutters from the 3000s to use in the 2000s is OK, though. Just don't leave them there.
 * Even the temporal terrorist  adheres to this rule, although for pragmatic reasons rather than a desire to preserve history (which would run counter to his goals): his three robots are all designed to self-destruct in the event they are disabled and presumably captured. For the most part, however, this rule is adhered to only as a matter of coincidence and is frequently ignored, especially in the second game.
 * Invoked by in the main scenario of Half Minute Hero. If you decide to replay a level, you can't equip any items that you've earned from later levels (the Time Goddess will tell you that doing so would create a Temporal Paradox). If you attempt to equip an item that's been struck out in the equipment menu, you'll start the level with nothing in that equipment slot.

Web Original

 * The time traveling boat SCP does not allow anything to be taken out of its time. If you try, it will change it to something that fits the time its in.

Western Animation

 * Vandal Savage's time machine in Justice League works with a sort of inversion: You can't go back to a time where you already exist, but you can send any objects through that you want. Being an immortal caveman, Savage can't go back himself, so he sends a laptop to himself during World War II in order to win the war for Germany.
 * In a later episode, Superman gets blasted into the future. It turns out Vandal Savage had some grand master scheme that went awry, killing everyone except himself (Immortal Magnificent Bastard caveman Nazi, remember). Savage regretted ruining the world, and he and Superman got another time machine he had working; since Superman was gone, he could travel back in time long enough to foil Savage's plot.
 * In Teenage Mutant Ninja Turtles: Fast Forward, the turtles and Master Splinter are abruptly zapped to the future. Their weapons and cloth—er, accessories get left behind. No explanation is given, and it doesn't happen on the return journey, though they voluntarily leave future technology where it belongs.