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   529065篇
  免费   4170篇
  国内免费   1286篇
化学   269338篇
晶体学   7645篇
力学   25998篇
综合类   17篇
数学   67880篇
物理学   163643篇
  2021年   5050篇
  2020年   5484篇
  2019年   6236篇
  2018年   8431篇
  2017年   8568篇
  2016年   11642篇
  2015年   6190篇
  2014年   10451篇
  2013年   23530篇
  2012年   18368篇
  2011年   21830篇
  2010年   16439篇
  2009年   16305篇
  2008年   20686篇
  2007年   20531篇
  2006年   18634篇
  2005年   16635篇
  2004年   15482篇
  2003年   13967篇
  2002年   13857篇
  2001年   14734篇
  2000年   11354篇
  1999年   8754篇
  1998年   7604篇
  1997年   7472篇
  1996年   6932篇
  1995年   6258篇
  1994年   6264篇
  1993年   6019篇
  1992年   6376篇
  1991年   6867篇
  1990年   6578篇
  1989年   6488篇
  1988年   6322篇
  1987年   6133篇
  1986年   5871篇
  1985年   7411篇
  1984年   7770篇
  1983年   6535篇
  1982年   6818篇
  1981年   6327篇
  1980年   6003篇
  1979年   6505篇
  1978年   6744篇
  1977年   6629篇
  1976年   6587篇
  1975年   6302篇
  1974年   6129篇
  1973年   6424篇
  1972年   4706篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
961.
We investigate the Scheme programming language opportunities to analytically calculate the Clebsch-Gordan coefficients, Wigner 6j and 9j symbols, and general recoupling coefficients that are used in the quantum theory of angular momentum. The considered coefficients are calculated by a direct evaluation of the sum formulas. The calculation results for large values of quantum angular momenta were compared with analogous calculations with FORTRAN and Java programming languages. The text was submitted by the authors in English.  相似文献   
962.
963.
Adaptation of populations takes place with the occurrence and subsequent fixation of mutations that confer some selective advantage to the individuals which acquire it. For this reason, the study of the process of fixation of advantageous mutations has a long history in the population genetics literature. Particularly, the previous investigations aimed to find out the main evolutionary forces affecting the strength of natural selection in the populations. In the current work, we investigate the dynamics of fixation of beneficial mutations in a subdivided population. The subpopulations (demes) can exchange migrants among their neighbors, in a migration network which is assumed to have either a random graph or a scale-free topology. We have observed that the migration rate drastically affects the dynamics of mutation fixation, despite of the fact that the probability of fixation is invariant on the migration rate, accordingly to Maruyama's conjecture. In addition, we have noticed a topological dependence of the adaptive evolution of the population when clonal interference becomes effective.  相似文献   
964.
In experiment PAX, proposed for the new accelerator complex at GSI, investigations in the field of high-energy spin physics with the use of a polarized antiproton beam are planned. In this paper the possibilities for triggering are considered taking into account the PAX detector properties and a probable configuration of the trigger system is discussed for the first time. The text was submitted by the authors in English.  相似文献   
965.
We present a framework for efficiently performing Monte Carlo wave-function simulations in cavity QED with moving particles. It relies heavily on the object-oriented programming paradigm as realised in C++, and is extensible and applicable for simulating open interacting qua ntum dynamics in general. The user is provided with a number of “elements”, e.g. pumped moving particles, pumped lossy cavity modes, and various interactions to compose complex interacting systems, which contain several particles moving in electromagnetic fields of various configurations, and perform wave-function simulations on such systems. A number of tools are provided to facilitate the implementation of new elements.  相似文献   
966.
An explicitly solvable analog of the Kirchhoff flow for the case of a semipenetrable obstacle is considered. Its application to estimating the efficiency of free flow turbines is discussed.  相似文献   
967.
A review of the experimental and theoretical studies of the crown ether complexes with polar molecules in their crystals, solutions, and in a gas phase is given. The type of the molecular bonds in the complexes, their stoichiometry, and the change in the macrocycle conformation during complex formation are considered, as well as the effect of the macrocycle structure and the nature of the medium on the efficiency of the molecular bonding. New data are given on the enthalpies of transfer of the crown ethers from tetrachloromethane into solvents capable of forming hydrogen bonds. The enthalpies of specific interactions of macrocycles with the molecules of the solvents in the medium of the same solvents are characterized. The conformations of the crown ethers in the media under study are discussed.  相似文献   
968.
969.
970.
Thomas  M. F.  Case  G. S.  Bland  J.  Herring  A. D. F.  Stirling  W. G.  Tixier  S.  Boni  P.  Ward  R. C. C.  Wells  M. R.  Langridge  S. 《Hyperfine Interactions》2002,141(1-4):471-476
Hyperfine Interactions - Multilayers of Ce/Fe and U/Fe were fabricated by sputtering and studied by X-ray diffraction and reflectivity, Mössbauer spectroscopy and polarised neutron...  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