首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   304254篇
  免费   1786篇
  国内免费   647篇
化学   146022篇
晶体学   4345篇
力学   15081篇
综合类   6篇
数学   46481篇
物理学   94752篇
  2020年   1970篇
  2019年   2264篇
  2018年   10952篇
  2017年   11674篇
  2016年   7996篇
  2015年   3110篇
  2014年   3930篇
  2013年   9369篇
  2012年   10875篇
  2011年   19879篇
  2010年   12514篇
  2009年   12559篇
  2008年   17832篇
  2007年   21219篇
  2006年   7819篇
  2005年   12974篇
  2004年   9268篇
  2003年   8885篇
  2002年   6852篇
  2001年   6097篇
  2000年   4995篇
  1999年   3508篇
  1998年   3054篇
  1997年   3052篇
  1996年   2992篇
  1995年   2426篇
  1994年   2503篇
  1993年   2531篇
  1992年   2666篇
  1991年   2730篇
  1990年   2634篇
  1989年   2617篇
  1988年   2557篇
  1987年   2524篇
  1986年   2436篇
  1985年   3121篇
  1984年   3298篇
  1983年   2652篇
  1982年   2920篇
  1981年   2796篇
  1980年   2592篇
  1979年   2826篇
  1978年   2954篇
  1977年   2864篇
  1976年   2865篇
  1975年   2714篇
  1974年   2686篇
  1973年   2877篇
  1972年   1887篇
  1967年   1868篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
Journal of Structural Chemistry - An analysis is presented for the results obtained in the studies initiated by A. E. Shvelashivili, Corresponding Member, Academy of Sciences of Georgia, and...  相似文献   
122.
123.
A first example of an Et2Zn mediated silylation of 1-aklynes is reported. A series of functional groups are tolerated in this reaction. Mechanistic studies support Zn alkynilides as intermediates in the reaction. This reaction protocol provides a practical method for the preparation of alkynylsilanes and expands the application of organometallic zinc in organic synthesis.  相似文献   
124.
The structure, chemical composition, and magnetic properties of electrochemically deposited nanocrystalline Co-Ni-Fe films were investigated using a number of techniques. A high saturation magnetic induction up to B s = 21 kG was attained. An enhancement of the saturation magnetization compared to the ideal anticipated one was revealed, which correlated with the nonlinear behavior of the structural phase composition and lattice parameters with the change of the composition. The text was submitted by the authors in English.  相似文献   
125.
Methods for phase stabilization of ammonium nitrate were sought for in order to considerably expand the application area of this oxidizing agent in various-purpose self-combustible formulations, including that in a new generation of gas-generating formulations for automobile air bags. New methods for stabilization of ammonium nitrate were studied and, in particular, a search was made for organic compounds that can stabilize ammonium nitrate even at their low content. The mechanism of phase state stabilization of ammonium nitrate by compounds of this kind was examined.  相似文献   
126.
Kinetic, sorption and selectivity properties of commercial adsorbents are improved by adding petroleum residues (tar asphaltene concentrates) 13% of whole mass. Obtained adsorbents can be used for selective extraction of nobel metals from multicomponent polymetallic solutions of heavy metals and fro sewages purification for removing arsenic.  相似文献   
127.
Using the simplest (sinusoidal) corrugation profile in the approximation of absence of losses in the material as an example, we study the regimes of complete transformation of an incident wave to the diffraction lobe by a corrugated metal surface or a corrugated interface of two dielectric media. A numerical-intuitive pattern of appearance and evolution of such regimes with increasing corrugation amplitude is revealed. It is shown that the regimes of complete transformation of an incident wave to the diffraction lobe are possible in both the case of autocollimation and the case of a considerable deviation from it. The examination is based on a numerical method of solving the integral equation by means of a specially created interactive processing system in Visual Fortran.  相似文献   
128.
All 3-dimensional convex polytopes are known to be rigid. Still their Minkowski differences (virtual polytopes) can be flexible with any finite freedom degree. We derive some sufficient rigidity conditions for virtual polytopes and present some examples of flexible ones. For example, Bricard's first and second flexible octahedra can be supplied by the structure of a virtual polytope.  相似文献   
129.
130.
In this paper, integration of interference phenomenon into femtosecond laser micromachining was reported as the femtosecond laser pulses were reshaped spatially to perform ablation. The generation of circular interference pattern was demonstrated by overlapping infrared femtosecond laser pulses. The interference pattern was subsequently focused on a copper substrate to ablate microstructures of concentric circular rings. The present technique is expected to open up new applications in the areas of rapid fabrication of micro-Fresnel lenses, hybrid microlenses and lens arrays.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号