全文获取类型
收费全文 | 3994篇 |
免费 | 182篇 |
国内免费 | 48篇 |
专业分类
化学 | 2356篇 |
晶体学 | 22篇 |
力学 | 79篇 |
数学 | 480篇 |
物理学 | 752篇 |
无线电 | 535篇 |
出版年
2023年 | 53篇 |
2022年 | 60篇 |
2021年 | 82篇 |
2020年 | 94篇 |
2019年 | 105篇 |
2018年 | 92篇 |
2017年 | 83篇 |
2016年 | 146篇 |
2015年 | 89篇 |
2014年 | 128篇 |
2013年 | 212篇 |
2012年 | 265篇 |
2011年 | 279篇 |
2010年 | 185篇 |
2009年 | 146篇 |
2008年 | 217篇 |
2007年 | 256篇 |
2006年 | 255篇 |
2005年 | 194篇 |
2004年 | 158篇 |
2003年 | 120篇 |
2002年 | 90篇 |
2001年 | 57篇 |
2000年 | 53篇 |
1999年 | 59篇 |
1998年 | 46篇 |
1997年 | 52篇 |
1996年 | 39篇 |
1995年 | 30篇 |
1994年 | 25篇 |
1993年 | 32篇 |
1992年 | 34篇 |
1991年 | 27篇 |
1990年 | 17篇 |
1989年 | 22篇 |
1988年 | 30篇 |
1987年 | 15篇 |
1985年 | 26篇 |
1984年 | 21篇 |
1983年 | 16篇 |
1982年 | 16篇 |
1981年 | 26篇 |
1980年 | 21篇 |
1979年 | 21篇 |
1978年 | 22篇 |
1977年 | 20篇 |
1976年 | 13篇 |
1975年 | 14篇 |
1974年 | 11篇 |
1972年 | 10篇 |
排序方式: 共有4224条查询结果,搜索用时 21 毫秒
1.
2.
3.
4.
Hyun‐Cheol Kim Charalampos Z. Patrikakis Nikos Minogiannis Pantelis N. Karamolegkos Alex Lambiris Kyuheon Kim 《ETRI Journal》2006,28(4):411-424
This paper presents a multimedia streaming platform for efficiently transmitting MPEG‐4 content over IP networks. The platform includes an MPEG‐4 compliant streaming server and client, supporting object‐based representation of multimedia scenes, interactivity, and advanced encoding profiles defined by the ISO standard. For scalability purposes, we employ an application‐layer multicast scheme for media transmission using overlay networks. The overlay network, governed by the central entity of the network distribution manager, is dynamically deployed according to a set of pre‐defined criteria. The overlay network supports both broadcast delivery and video‐on‐demand content. The multimedia streaming platform is standards‐compliant and utilizes widespread multimedia protocols such as MPEG‐4, real‐time transport protocol, real‐time transport control protocol, and real‐time streaming protocol. The design of the overlay network was architected with the goal of transparency to both the streaming server and the client. As a result, many commercial implementations that use industry‐standard protocols can be plugged into the architecture relatively painlessly and can enjoy the benefits of the platform. 相似文献
5.
Ku T.K. Chen S.H. Yang C.D. She N.J. Wang C.C. Chen C.F. Hsieh I.J. Cheng H.C. 《Electron Device Letters, IEEE》1996,17(5):208-210
Undoped and phosphorus (P)-doped diamond-clad Si field emitter arrays have been successfully fabricated using microwave plasma chemical vapor deposition (MPCVD) technology. The electron emission from the blunt diamond-clad microtips are much higher than those for the pure Si tips with sharp curvature due to a lower work function. Furthermore, the characteristics of emission current against applied voltage for the P-doped diamond-clad tips show superior emission at lower field to the undoped ones. After the examination of Auger electron spectroscopy (AES) and electrical characteristics of as-grown diamond, such a significant enhancement of the electron emission from the P-doped diamond-clad tips is attributed to a higher electron conductivity and defect densities 相似文献
6.
7.
Alex Hellsten 《Archive for Mathematical Logic》2006,45(6):705-714
We extract some properties of Mahlo’s operation and show that some other very natural operations share these properties. The weakly compact sets form a similar hierarchy as the stationary sets. The height of this hierarchy is a large cardinal property connected to saturation properties of the weakly compact ideal. 相似文献
8.
Yiming Huai Mahendra PakalaZhitao Diao Dmytro ApalkovYunfei Ding Alex Panchula 《Journal of magnetism and magnetic materials》2006
Spin-transfer driven switching was observed in MgO based magnetic tunnelling junctions (MTJ) with tunnelling magnetoresistance ratio of up to 160% and the average intrinsic switching current density (Jc0) down to 2 MA/cm2, which are the best known results reported in spin-transfer switched MTJ nanostructures. Based on a comparison of results both from MgO and AlOx MTJs, further switching current decrease via MgO dual structures with two pinned layers is discussed. 相似文献
9.
The stannous chloride dihydrate-mediated deprotection-bicyclisation of a range of amides possessing a pendant acetal group is reported. These mild reaction conditions have been used to prepare a number of ring-fused heterocyclic compounds, some in enantiomerically pure form, which should be of interest both in their own right and as building blocks for the production of more complex target molecules. 相似文献
10.
We study property (T) and the fixed-point property for actions on L
p
and other Banach spaces. We show that property (T) holds when L
2 is replaced by L
p
(and even a subspace/quotient of L
p
), and that in fact it is independent of 1≤p<∞. We show that the fixed-point property for L
p
follows from property (T) when 1<p< 2+ε. For simple Lie groups and their lattices, we prove that the fixed-point property for L
p
holds for any 1< p<∞ if and only if the rank is at least two. Finally, we obtain a superrigidity result for actions of irreducible lattices
in products of general groups on superreflexive spaces.
Bader partially supported by ISF grant 100146; Furman partially supported by NSF grants DMS-0094245 and DMS-0604611; Gelander
partially supported by NSF grant DMS-0404557 and BSF grant 2004010; Monod partially supported by FNS (CH) and NSF (US). 相似文献