全文获取类型
收费全文 | 10612篇 |
免费 | 1971篇 |
国内免费 | 1250篇 |
专业分类
化学 | 7716篇 |
晶体学 | 65篇 |
力学 | 656篇 |
综合类 | 77篇 |
数学 | 1065篇 |
物理学 | 4254篇 |
出版年
2024年 | 43篇 |
2023年 | 277篇 |
2022年 | 384篇 |
2021年 | 429篇 |
2020年 | 483篇 |
2019年 | 427篇 |
2018年 | 353篇 |
2017年 | 300篇 |
2016年 | 524篇 |
2015年 | 465篇 |
2014年 | 563篇 |
2013年 | 802篇 |
2012年 | 986篇 |
2011年 | 971篇 |
2010年 | 639篇 |
2009年 | 631篇 |
2008年 | 707篇 |
2007年 | 620篇 |
2006年 | 545篇 |
2005年 | 475篇 |
2004年 | 364篇 |
2003年 | 325篇 |
2002年 | 272篇 |
2001年 | 214篇 |
2000年 | 213篇 |
1999年 | 253篇 |
1998年 | 213篇 |
1997年 | 191篇 |
1996年 | 205篇 |
1995年 | 175篇 |
1994年 | 142篇 |
1993年 | 124篇 |
1992年 | 102篇 |
1991年 | 74篇 |
1990年 | 84篇 |
1989年 | 56篇 |
1988年 | 48篇 |
1987年 | 44篇 |
1986年 | 29篇 |
1985年 | 28篇 |
1984年 | 14篇 |
1983年 | 9篇 |
1982年 | 13篇 |
1981年 | 8篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1957年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
971.
Jinming LiuXiaoru Zhao Libing DuanMengmeng Cao Huinan SunJifeng Shao Shuai ChenHaiyan Xie Xiao ChangChangle Chen 《Applied Surface Science》2011,257(23):10156-10160
Nb-doped TiO2 (TNO) thin films were prepared by sol-gel dip-coating method with Nb content in a wide range of 0-20 at.%. The prepared films were preheated at 400 °C and then undertaken by two different post-annealing processes: (a) three times vacuum annealing and (b) multi-round annealing. The designed multi-round annealing was shown to be an effective way to improve the conductive properties of the films, compared to the traditional vacuum annealing process. The minimum resistivity reached approximately 0.5 Ω cm with Nb doping concentration around 12 at.%, and the carrier density increased with Nb-doping concentration until the critical point of 12 at.%, which might be the optimal doping content for our TNO films prepared by sol-gel method. 相似文献
972.
Q. Wang Y. Xie Y. P. Zhao Q. S. Zhu M. Z. Mo D. W. Yang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,55(1):243-247
To raise the utilization ratio of the energy power, and
meanwhile, guarantee the waveform of the main discharge current to obtain
X-ray laser, our capillary discharged Ne-like Ar soft X-ray laser system
adopts Blumleim transmission line (BTL) and a 300 kV-Marx generator; and by
using our self-developed intrinsic-prepulse elimination device and
extrinsic-prepulse generator, we successfully removed the intrinsic prepulse
of BTL, and thus eliminated its deteriorative effect towards Z-pinch plasma.
By this means, we obtained stable X-ray laser output; and the voltage
transmission rate of our system nearly reaches 122%, which provides a
guarantee for the miniaturization of the power source and the whole system. 相似文献
973.
A series of four novel hydrazine-modified diamine conjugates (7a-b, 8a-b) were synthesized and evaluated for cytotoxicity against Melanoma B 16, α-difluoromethylornithine (DFMO)-treated B 16, spermidine (SPD)-treated B 16, Mouse leukemia L 1210 and Hela cell lines. Both the DFMO-B 16 and SPD-B 16 experiments indicated that conjugates 7a-b and 8a-b could recognize the polyamine transporter (PAT) and enter the cells in part or in whole via PAT, although they were not as efficient as the reference, 9- anthracenemethyl homospermidine (1). 2007 Chao Jie Wang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. 相似文献
974.
Guo‐Xu Zhang Ying Xie Hai‐Tao Yu Hong‐Gang Fu 《Journal of computational chemistry》2009,30(12):1785-1798
The structural and electronic properties of five terminations of cubic lead titanate (PbTiO3) (110) polar surface were investigated by first‐principles total‐energy calculations using a periodic slab model. On the PbTiO termination, an anomalous filling of conduction band was observed, whereas on the O2 termination, two surface oxygen atoms formed a peroxo group, demonstrating that the electronic structures of the two stoichiometric terminations undergo significant changes with respect to bulk materials. However, for the three nonstoichiometric TiO‐, Pb‐, and O‐terminated surfaces, their electronic structures are very similar to bulk. Charge redistribution results for the five terminations confirmed that electronic structure and surface composition changes are responsible for their polarity compensation. However, which mechanism actually dominates the stabilization process depends upon energetic considerations. A thermodynamic stability diagram suggested that the two stoichiometric terminations are unstable; however, the three nonstoichiometric terminations can be stabilized in some given regions. Furthermore, this study indicates that the very different stabilities and surface states filling behaviors of the PbTiO3 (110) polar surface with respect to SrTiO3 and BaTiO3 ones seem to originate from the partially covalent characteristics of Pb O pairs. © 2008 Wiley Periodicals, Inc. J Comput Chem 2009 相似文献
975.
976.
In this paper, we present an extended ghost fluid method (GFM) for computations of inviscid compressible multifluids in Lagrangian coordinate. That is, we capture the appropriate interface conditions by defining a fluid that has the velocity and the pressure of the real fluid at each point, but the entropy or the internal energy of some other fluid. Meanwhile, a single-fluid solver, CWENO-type central-upwind scheme, is developed in Lagrangian coordinate. The high resolution and the non-oscillatory quality of the scheme can be verified by solving several numerical experiments. 相似文献
977.
978.
David M. Black Roman Davis Brian D. Doan Tom C. Lovelace Alan Millar Jennifer F. Toczko Shiping Xie 《Tetrahedron: Asymmetry》2008,19(17):2015-2019
An efficient highly diastereo- and enantioselective synthesis of the bis-tetrahydrofuran (bis-THF) alcohol of several HIV protease inhibitors, including Brecanavir and Darunavir, has been achieved utilizing an Evans Mukaiyama aldol reaction of (benzyloxy)acetaldehyde and a silyl ketene acetal. The lactone alcohol intermediate from the catalytic aldol reaction was reduced to a lactol. Palladium catalyzed hydrogenolysis removed the benzyl protection and promoted an in situ cyclization to form the epimer of the bis-THF alcohol in a 98:2 diastereomeric ratio and 97:3 enantiomeric ratio. The alcohol epimer was readily converted to the target in two steps by oxidation to a ketone followed by highly selective reduction to the bis-THF alcohol. 相似文献
979.
980.
模压复制是形成全息产品的最后一道工序,它类似凸版印刷,因而可以实现机械化大规模生产。本文介绍了平压、滚压工艺过程及所用的原材料及设备,同时还介绍了将模压全息图应用到别的载体材料上的热冲压转印技术。 相似文献