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   459794篇
  免费   5598篇
  国内免费   1496篇
化学   242341篇
晶体学   6712篇
力学   19983篇
综合类   25篇
数学   58421篇
物理学   139406篇
  2021年   3776篇
  2020年   4201篇
  2019年   4524篇
  2018年   6973篇
  2017年   7103篇
  2016年   9473篇
  2015年   6058篇
  2014年   8964篇
  2013年   20751篇
  2012年   18286篇
  2011年   21233篇
  2010年   14787篇
  2009年   14485篇
  2008年   18101篇
  2007年   18041篇
  2006年   16751篇
  2005年   18548篇
  2004年   17019篇
  2003年   13950篇
  2002年   12136篇
  2001年   13587篇
  2000年   10156篇
  1999年   8021篇
  1998年   6647篇
  1997年   6367篇
  1996年   6114篇
  1995年   5501篇
  1994年   5423篇
  1993年   5215篇
  1992年   5939篇
  1991年   6029篇
  1990年   5756篇
  1989年   5544篇
  1988年   5553篇
  1987年   5414篇
  1986年   5120篇
  1985年   6583篇
  1984年   6711篇
  1983年   5317篇
  1982年   5400篇
  1981年   5375篇
  1980年   4965篇
  1979年   5373篇
  1978年   5508篇
  1977年   5399篇
  1976年   5379篇
  1975年   4942篇
  1974年   4915篇
  1973年   4913篇
  1972年   3486篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
ABSTRACT

The Coupled-Cluster (CC) theory is one of the most successful high precision methods used to solve the stationary Schrödinger equation. In this article, we address the mathematical foundation of this theory with focus on the advances made in the past decade. Rather than solely relying on spectral gap assumptions (non-degeneracy of the ground state), we highlight the importance of coercivity assumptions – Gårding type inequalities – for the local uniqueness of the CC solution. Based on local strong monotonicity, different sufficient conditions for a local unique solution are suggested. One of the criteria assumes the relative smallness of the total cluster amplitudes (after possibly removing the single amplitudes) compared to the Gårding constants. In the extended CC theory the Lagrange multipliers are wave function parameters and, by means of the bivariational principle, we here derive a connection between the exact cluster amplitudes and the Lagrange multipliers. This relation might prove useful when determining the quality of a CC solution. Furthermore, the use of an Aubin–Nitsche duality type method in different CC approaches is discussed and contrasted with the bivariational principle.  相似文献   
42.
43.
Cavitation erosion is caused in solids exposed to strong pressure waves developing in an adjacent fluid field. The knowledge of the transient distribution of stresses in the solid is important to understand the cause of damaging by comparisons with breaking points of the material. The modeling of this problem requires the coupling of the models for the fluid and the solid. For this purpose, we use a strategy based on the solution of coupled Riemann problems that has been originally developed for the coupling of 2 fluids. This concept is exemplified for the coupling of a linear elastic structure with an ideal gas. The coupling procedure relies on the solution of a nonlinear equation. Existence and uniqueness of the solution is proven. The coupling conditions are validated by means of quasi‐1D problems for which an explicit solution can be determined. For a more realistic scenario, a 2D application is considered where in a compressible single fluid, a hot gas bubble at low pressure collapses in a cold gas at high pressure near an adjacent structure.  相似文献   
44.
45.
46.
Russian Journal of General Chemistry - Hybrid liquid crystal systems with different ratios of the components have been prepared on the basis of 5,5′-di(heptadecyl)-2,2′-bipyridine...  相似文献   
47.
48.
Palladium nanoparticle‐incorporated metal–organic framework MIL‐101 (Pd/MIL‐101) was successfully synthesized and characterized using X‐ray diffraction, nitrogen physisorption, X‐ray photoelectron, UV–visible and infrared spectroscopies, and transmission electron microscopy. The characterization techniques confirmed high porosity and high surface area of MIL‐101 and high stability of nano‐size palladium particles. Pd/MIL‐101 nanocomposite was investigated for the Sonogashira cross‐coupling reaction of aryl and heteroaryl bromides with various alkynes under copper‐free conditions. The reusability of the catalyst was tested for up to four cycles without any significant loss in catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
49.
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   
50.
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