全文获取类型
收费全文 | 22020篇 |
免费 | 2661篇 |
国内免费 | 2700篇 |
专业分类
化学 | 16655篇 |
晶体学 | 387篇 |
力学 | 906篇 |
综合类 | 191篇 |
数学 | 2731篇 |
物理学 | 6511篇 |
出版年
2023年 | 268篇 |
2022年 | 487篇 |
2021年 | 640篇 |
2020年 | 764篇 |
2019年 | 803篇 |
2018年 | 644篇 |
2017年 | 646篇 |
2016年 | 909篇 |
2015年 | 979篇 |
2014年 | 1153篇 |
2013年 | 1644篇 |
2012年 | 1760篇 |
2011年 | 1894篇 |
2010年 | 1414篇 |
2009年 | 1369篇 |
2008年 | 1615篇 |
2007年 | 1360篇 |
2006年 | 1266篇 |
2005年 | 1088篇 |
2004年 | 858篇 |
2003年 | 761篇 |
2002年 | 834篇 |
2001年 | 635篇 |
2000年 | 450篇 |
1999年 | 371篇 |
1998年 | 259篇 |
1997年 | 175篇 |
1996年 | 197篇 |
1995年 | 154篇 |
1994年 | 173篇 |
1993年 | 151篇 |
1992年 | 147篇 |
1991年 | 153篇 |
1990年 | 104篇 |
1989年 | 94篇 |
1988年 | 64篇 |
1987年 | 74篇 |
1986年 | 64篇 |
1985年 | 89篇 |
1984年 | 75篇 |
1983年 | 45篇 |
1982年 | 68篇 |
1981年 | 59篇 |
1980年 | 61篇 |
1979年 | 56篇 |
1978年 | 63篇 |
1977年 | 57篇 |
1976年 | 51篇 |
1975年 | 39篇 |
1973年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
61.
62.
Outline imaging by THz time domain spectroscopy is proposed. Spectroscopic splitting at interface is reported, The principle of outline imaging is put forward. Experimental results demonstrate the feasibility of outline imaging by spectroscopic splitting, It is shown that clear out:line image of sample interface could be achieved easily by this technique. The spatial resolution is about 0.6mm. The THz-beam focus, the scanning step and the THz pulse width are the critical foctors affecting the imaging resolution. The signal-to-noise ratio of this technique could be improved greatly compared to the conventional transsion imaging. 相似文献
63.
64.
磁控溅射技术制备ZnO透光薄膜 总被引:1,自引:0,他引:1
采用RF磁控溅射方法,在玻璃衬底上制备了择优取向的ZnO薄膜;通过台阶仪、X射线衍射技术、原子力显微镜和分光光度计分别测量了不同溅射功率条件下淀积的ZnO薄膜厚度(淀积速率)、结晶质量、表面形貌与粗糙度、透光光谱,报道了该薄膜结晶质量、薄膜粗糙度与其在可见光区透光率的关系. 相似文献
65.
Sang Kyu Lee Min Ju Cho Jung‐Il Jin Dong Hoon Choi 《Journal of polymer science. Part A, Polymer chemistry》2007,45(3):531-542
New photocrosslinkable maleimide copolymers have been synthesized by the attachment of a tricyanopyrrolidene‐based chromophore. The 2‐(3‐cyano‐4‐(2‐{4‐[hexyl‐(6‐hydroxy‐hexyl)‐amino]‐phenyl}‐vinyl)‐5‐oxo‐1‐{4‐[4‐(3‐oxo‐3‐phenyl‐propenyl)‐ phenoxy]‐butyl}‐1,5‐dihydro‐pyrrol‐2‐ylidene)‐malononitrile chromophore exhibits nonlinear optical activity and contains a chalcone moiety that is sensitive to UV light (λ = 330–360 nm) for crosslink formation. The maleimide monomers have also been functionalized with chalcone moieties. The resultant copolymers exhibit great processability, and one of them shows a maximum electrooptic coefficient of 90 pm/V at 1300 nm. We could control the thermal stability of the electrooptic coefficient with the newly synthesized photoreactive copolymers successfully. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 531–542, 2007 相似文献
66.
In this paper we propose a general integration scheme for a Multi-Criteria Decision Making model of the Multi-Attribute Utility
Theory in Constraint Programming. We introduce the Choquet integral as a general aggregation function for multi-criteria optimization
problems and define the Choquet global constraint that propagates this function during the Branch-and-Bound search. Finally the benefits of the propagation
of the Choquet constraint are evaluated on the examination timetabling problem. 相似文献
67.
CHEN Yue WANG Xuan-jun CONG Xian-ling ZHANG Pei-yin WU Xiu-li WEI Hong-fei WANG Li WAN Min WANG Li-ying YU Yong-li 《高等学校化学研究》2006,22(6):712-716
IntroductionClassical swine fever(CSF), included in the listA of the Office International des Epizooties(OIE), is ahighly contagious disease of domestic pigs and is con-sidered as the mostharmful disease occurring in pigs allover the world[1]. Outbreaks o… 相似文献
68.
The rutile TiO2(1 1 0) surface is a highly anisotropic surface exhibiting “channels” delimited by oxygen rows. In previous experimental and theoretical DFT works we could identify the molybdenum adsorption sites. They are located inside the channels. Moreover, experimental studies have shown that during subsequent annealing after deposition, special molybdenum nano structures can be formed, especially two monolayer high pyramidal chains of atoms.In order to better understand the dynamics of nano structure formation, we present a kinetic Monte Carlo study on diffusion and adsorption of molybdenum atoms on a TiO2(1 1 0) surface. A quasi one-dimensional lattice gas model has been used which describes the possible adsorption sites of a Mo atom in a single channel of the surface. The atomic positions of a 1.5 monolayer thick Mo film formed of pyramidal chains define the lattice sites of the model. Thereby the formation of three-dimensional clusters could be studied. Here we have studied the cluster formation as a function of parameters that can be controlled in a growth experiment by physical vapor deposition: deposition and annealing temperature, flux and total amount of deposited Mo. Good qualitative agreement with recent experiments is obtained. 相似文献
69.
70.