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   50928篇
  免费   3080篇
  国内免费   2163篇
化学   29634篇
晶体学   830篇
力学   2365篇
综合类   165篇
数学   5185篇
物理学   17992篇
  2023年   377篇
  2022年   787篇
  2021年   861篇
  2020年   985篇
  2019年   1055篇
  2018年   1049篇
  2017年   887篇
  2016年   1481篇
  2015年   1209篇
  2014年   1591篇
  2013年   2637篇
  2012年   2798篇
  2011年   3094篇
  2010年   2253篇
  2009年   2180篇
  2008年   2473篇
  2007年   2350篇
  2006年   2107篇
  2005年   1861篇
  2004年   1707篇
  2003年   1561篇
  2002年   1624篇
  2001年   1955篇
  2000年   1342篇
  1999年   1127篇
  1998年   798篇
  1997年   744篇
  1996年   645篇
  1995年   598篇
  1994年   524篇
  1993年   461篇
  1992年   546篇
  1991年   555篇
  1990年   533篇
  1989年   461篇
  1988年   478篇
  1987年   450篇
  1986年   400篇
  1985年   463篇
  1984年   488篇
  1983年   350篇
  1982年   388篇
  1981年   376篇
  1979年   402篇
  1978年   378篇
  1977年   394篇
  1976年   391篇
  1975年   342篇
  1974年   322篇
  1973年   339篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
We study the full counting statistics of transport electrons through a semiconductor two-level quantum dot with Rashba spin–orbit (SO) coupling, which acts as a nonabelian gauge field and thus induces the electron transition between two levels along with the spin flip. By means of the quantum master equation approach, shot noise and skewness are obtained at finite temperature with two-body Coulomb interaction. We particularly demonstrate the crucial effect of SO coupling on the super-Poissonian fluctuation of transport electrons, in terms of which the SO coupling can be probed by the zero-frequency cumulants. While the charge currents are not sensitive to the SO coupling.  相似文献   
2.
3.
By tuning the length and rigidity of the spacer of bis(biurea) ligands L, three structural motifs of the A2L3 complexes (A represents anion, here orthophosphate PO43?), namely helicate, mesocate, and mono‐bridged motif, have been assembled by coordination of the ligand to phosphate anion. Crystal structure analysis indicated that in the three complexes, each of the phosphate ions is coordinated by twelve hydrogen bonds from six surrounding urea groups. The anion coordination properties in solution have also been studied. The results further demonstrate the coordination behavior of phosphate ion, which shows strong tendency for coordination saturation and geometrical preference, thus allowing for the assembly of novel anion coordination‐based structures as in transition‐metal complexes.  相似文献   
4.
In order to investigate the characteristics of force chains in a granular flow system, a parallel plate shear cell is constructed to simulate the shear movement of an infinite parallel plate and observe variations in relevant parameters. The shear dilatancy process is divided into three stages, namely, plastic strain, macroscopic failure, and granular recombination. The stickslip phenomenon is highly connected with the evolution of force chains during the shear dilatancy process. The load–distribution rate curves and patterns of the force chains are utilized to describe the load-carrying behaviors and morphologic changes of force chains separately. Force chains, namely, “diagonal gridding,” “tadpole-shaped,” and “pinnate” are defined according to the form of the force chains in the corresponding three stages.  相似文献   
5.
6.
7.
This study is concerned with a new,explicit approach by means of which forms of the large strain elastic potential for multiaxial rubberlike elasticity may be obtained based on data for a single deformation mode.As a departure from usual studies,here for the first time errors may be estimated and rendered minimal for all possible deformation modes and,furthermore,failure behavior may be incorporated.Numerical examples presented are in accurate agreement with Treloar's well-known data.  相似文献   
8.
Russian Journal of Organic Chemistry - Methyl (Z)-3-[(2R,3R,4S,5S)-5-(2-methoxy-2-oxoethyl)-3,4-(isopropylidenedioxy)tetrahydrofuran-2-yl]-prop-2-enoate was synthesized, and its intramolecular...  相似文献   
9.
A new A, D-seco limonoid, named 12-acetyloxyperforatin (1), along with three known ones, were isolated from the leaves of Harrisonia perforata. Their structures were elucidated on the basis of spectroscopic analysis, including extensive NMR techniques and computational modelling. These compounds showed no inhibitory activity against the 11β-HSD1 enzyme.  相似文献   
10.
Saleh  Z. M.  Nasser  H.  Özkol  E.  Günöven  M.  Abak  K.  Canli  S.  Bek  A.  Turan  R. 《Journal of nanoparticle research》2015,17(10):1-12
Journal of Nanoparticle Research - Plasmonic interfaces consisting of silver nanoparticles of different sizes (50–100&;nbsp;nm) have been processed by the self-assembled dewetting...  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