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   2021篇
  免费   77篇
  国内免费   3篇
化学   1666篇
晶体学   23篇
力学   20篇
数学   99篇
物理学   293篇
  2023年   15篇
  2022年   17篇
  2021年   14篇
  2020年   32篇
  2019年   38篇
  2018年   19篇
  2017年   16篇
  2016年   53篇
  2015年   43篇
  2014年   59篇
  2013年   81篇
  2012年   105篇
  2011年   150篇
  2010年   70篇
  2009年   62篇
  2008年   135篇
  2007年   113篇
  2006年   126篇
  2005年   116篇
  2004年   115篇
  2003年   95篇
  2002年   79篇
  2001年   45篇
  2000年   30篇
  1999年   23篇
  1998年   22篇
  1997年   25篇
  1996年   22篇
  1994年   13篇
  1992年   16篇
  1991年   19篇
  1990年   17篇
  1989年   10篇
  1988年   20篇
  1987年   12篇
  1986年   12篇
  1985年   12篇
  1984年   20篇
  1983年   17篇
  1982年   13篇
  1981年   24篇
  1980年   23篇
  1979年   19篇
  1978年   15篇
  1977年   16篇
  1976年   15篇
  1975年   12篇
  1974年   15篇
  1973年   13篇
  1971年   10篇
排序方式: 共有2101条查询结果,搜索用时 15 毫秒
1.
Summary A supersonic jet spectrum of 9,10-dichloroanthracene is measured by stimulated-emission-pumping fluorescence dip spectrometry and conventional fluorescence spectrometry. The performance obtained is compared for these spectrometric methods, providing same information concerned with the energy level of the ground state. The former is more preferential for measurement of a high-resolution spectrum, since the spectral resolution is determined by the linewidth of the dumping laser. On the other hand, the latter is more preferential for measurement with better sensitivity at the expense of the spectral resolution, since the fluorescence throughput can be improved by increasing the slit width of the monochromator.Dedicated to Professor Dr. Wilhelm Fresenius on the occasion of his 80th birthday  相似文献   
2.
Tsuyoshi Kitamura 《Tetrahedron》2004,60(43):9649-9657
Synthesis of (+)-anthramycin was examined. A pyrrolobenzodiazepine skeleton could be synthesized by reductive cyclization of pyrrolidine derivative, which was obtained by enyne metathesis. The conjugated enamide ester part of (+)-anthramycin derivative was constructed by cross-metathesis.  相似文献   
3.
A new method was devised for measuring the pH of a concrete surface by pHBOY-P2 with a piece of filter paper by extracting the pH value from concrete. This is a simple and inexpensive method that does not damage the concrete building, and is easy to apply on concrete samples for monitoring. By using the method mentioned above, a drastic decrease of the pH value of concrete bridges and buildings has investigated. The method is environmentally friendly to detect the pH value change of concrete as an environmental sample investigation.  相似文献   
4.
5.
This paper derives a conservation law for mean waiting times in a single-server multi-class service queueing system (M X/G/1 type queue) with setup times which may be dependent on multiple customer classes and its arrival batch size by using the work decomposition property in the queueing system with vacations.  相似文献   
6.
We investigate low-temperature behaviors of a system with chirality-pair interaction on a one-dimensional lattice. In the course of the investigation, we evaluate asymptotic forms of the characteristic values of the integral equation satisfied by the Mathieu functions. It turns out that the low-temperature behavior of correlation length of the chirality-pair correlation function is different from the one for the Ising model of spin ±1 but akin to the one for the Ising model of infinite spin.  相似文献   
7.
We consider positive solutions of elliptic partial differential equations on non-compact domains of Riemannian manifolds. We explicitly determine Martin boundaries and Martin kernels for a class of elliptic equations in skew product form by exploiting and developing perturbation theory for elliptic equations and short/long-time estimates for fundamental solutions of parabolic equations.  相似文献   
8.
9.
10.
We consider nonnegative solutions of a parabolic equation in a cylinder D×(0,T), where D is a noncompact domain of a Riemannian manifold. Under the assumption [IU] (i.e., the associated heat kernel is intrinsically ultracontractive), we establish an integral representation theorem: any nonnegative solution is represented uniquely by an integral on (D×{0})∪(MD×[0,T)), where MD is the Martin boundary of D for the associated elliptic operator. We apply it in a unified way to several concrete examples to explicitly represent nonnegative solutions. We also show that [IU] implies the condition [SP] (i.e., the constant function 1 is a small perturbation of the elliptic operator on D).  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