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   43109篇
  免费   7088篇
  国内免费   5734篇
化学   30679篇
晶体学   531篇
力学   2578篇
综合类   415篇
数学   4896篇
物理学   16832篇
  2024年   154篇
  2023年   867篇
  2022年   1678篇
  2021年   1689篇
  2020年   1726篇
  2019年   1681篇
  2018年   1544篇
  2017年   1536篇
  2016年   2147篇
  2015年   2177篇
  2014年   2613篇
  2013年   3395篇
  2012年   4001篇
  2011年   4071篇
  2010年   2849篇
  2009年   2687篇
  2008年   2933篇
  2007年   2552篇
  2006年   2341篇
  2005年   1883篇
  2004年   1381篇
  2003年   1089篇
  2002年   1071篇
  2001年   930篇
  2000年   805篇
  1999年   896篇
  1998年   683篇
  1997年   655篇
  1996年   583篇
  1995年   558篇
  1994年   453篇
  1993年   421篇
  1992年   336篇
  1991年   290篇
  1990年   264篇
  1989年   223篇
  1988年   163篇
  1987年   146篇
  1986年   115篇
  1985年   105篇
  1984年   68篇
  1983年   54篇
  1982年   56篇
  1981年   25篇
  1980年   14篇
  1979年   5篇
  1976年   2篇
  1959年   3篇
  1957年   10篇
  1936年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Zhou  Jiuru 《Archiv der Mathematik》2021,116(6):693-706

In this paper, we study vanishing and splitting results on a complete smooth metric measure space \((M^n,g,\mathrm {e}^{-f}\mathrm {d}v)\) with various negative m-Bakry-Émery Ricci curvature lower bounds in terms of the first eigenvalue \(\lambda _1(\Delta _f)\) of the weighted Laplacian \(\Delta _f\), i.e., \(\mathrm {Ric}_{m,n}\ge -a\lambda _1(\Delta _f)-b\) for \(0<a\le \dfrac{m}{m-1}, b\ge 0\). In particular, we consider three main cases for different a and b with or without conditions on \(\lambda _1(\Delta _f)\). These results are extensions of Dung and Vieira, and weighted generalizations of Li-Wang, Dung-Sung, and Vieira.

  相似文献   
2.
3.
Journal of Sol-Gel Science and Technology - A novel gas sensing material, La–Y co-doped TiO2 nanoparticles, was synthesized by sol–gel method and applied to detect organic pollutants...  相似文献   
4.
5.
JPC – Journal of Planar Chromatography – Modern TLC - A new high-performance thin-layer chromatographic (HPTLC) method has been developed for the simultaneous estimation of...  相似文献   
6.
Terahertz(THz) wave emission from argon atom in a two-color laser pulses is studied numerically by solving the one-dimensional(1D) time-dependent Schr ¨odinger equation. The THz spectra we obtained include both discontinuous and continuum ones. By using the special basis functions that we previously proposed, our analysis points out that the discontinuous and continuum parts are contributed by bound–bound and continuum–continuum transition of atomic energy levels. Although the atomic wave function is strongly dressed during the interaction with laser fields, our identification for the discontinuous part of the THz wave shows that the transition between highly excited bound states can still be well described by the field-free basis function in the tunneling ionization regime.  相似文献   
7.
8.
9.
A new approach has been developed to improve SO2 sorption by cyano‐containing ionic liquids (ILs) through tuning the basicity of ILs and cyano–sulfur interaction. Several kinds of cyano‐containing ILs with different basicity were designed, prepared, and used for SO2 capture. The interaction between these cyano‐containing ILs and SO2 was investigated by FTIR and NMR methods. Spectroscopic investigations and quantum chemical calculations showed that dramatic effects on SO2 capacity originate from the basicity of the ILs and enhanced cyano–sulfur interaction. Furthermore, the captured SO2 was easy to release by heating or bubbling N2 through the ILs. This efficient and reversible process, achieved by tuning the basicity of ILs, is an excellent alternative to current technologies for SO2 capture.  相似文献   
10.
Ni–Co alloys have a wide range of applications in various fields owning to their excellent physical, chemical, and mechanical properties. In this paper, we prepare Ni–Co alloy coatings on 316L stain steel surfaces by electroplating. We present a novel approach utilizing a nanosecond laser to induce microtextures on Ni–Co alloy coatings. We study experimentally the effects of laser power and scanning rate on the surface morphologies of Ni–Co alloy coatings. The results indicate that the shape and size of induced microtextures can be controlled by the laser power and scanning rate. The size of grains increases with increase in the work current of the laser (WCL) at a certain scanning rate. With the WCL constant, the size of grains decreases with increase in scanning rate while their average height increases. It is a simple and easily-controlled method for the fabrication of microstructures on Ni–Co alloy coatings, which has promising applications in investigations of the properties of microtextured surfaces, such as friction, adhesion, and wetting.  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