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   307900篇
  免费   3419篇
  国内免费   4515篇
化学   144675篇
晶体学   5029篇
力学   17638篇
综合类   628篇
数学   43334篇
物理学   104530篇
  2021年   3445篇
  2020年   3730篇
  2019年   4535篇
  2018年   6555篇
  2017年   6937篇
  2016年   8288篇
  2015年   4039篇
  2014年   7485篇
  2013年   12909篇
  2012年   10871篇
  2011年   12588篇
  2010年   10830篇
  2009年   11009篇
  2008年   12414篇
  2007年   12079篇
  2006年   10888篇
  2005年   9397篇
  2004年   9000篇
  2003年   8202篇
  2002年   8497篇
  2001年   8160篇
  2000年   6626篇
  1999年   4824篇
  1998年   4443篇
  1997年   4273篇
  1996年   3874篇
  1995年   3422篇
  1994年   3493篇
  1993年   3493篇
  1992年   3491篇
  1991年   3859篇
  1990年   3878篇
  1989年   3876篇
  1988年   3628篇
  1987年   3695篇
  1986年   3372篇
  1985年   3881篇
  1984年   4113篇
  1983年   3524篇
  1982年   3705篇
  1981年   3387篇
  1980年   3145篇
  1979年   3640篇
  1978年   3691篇
  1977年   3857篇
  1976年   3928篇
  1975年   3672篇
  1974年   3527篇
  1973年   3688篇
  1972年   3178篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
121.
The stressed state of a thick three-layer plate with two circular holes is studied. Resolving functions are expressed in terms of Kolosov-Muskhelishvili integral potentials and modified Bessel functions. The problem is reduced to solving an infinite set of linear algebraic equations.Translated from Teoreticheskaya i Prikladnaya Mekhanika, No. 18, pp. 25–28, 1987.  相似文献   
122.
The Langevin dynamics and fluctuational-dissipative relationships for the hydrodynamic fluctuations for systems which are described in the third Barnett order with respect to the gradients of the hydrodynamic variables are generalized on the basis of a kinetic approach.  相似文献   
123.
124.
125.
Various methods for describing the distribution of water in the H2O-tributyl phosphate (TBP) system were considered. An equation for describing the deviations from the Henry law was proposed. A three-parameter equation for calculating the distribution of water in H2O-TBP-solvent systems was derived. It is based on the additive solubility model and allows for the dependence of the activity coefficients on the TBP concentration. Based on the published data, the parameters of the equation for a number of systems were calculated.  相似文献   
126.
A new method for calculating the radial spheroidal functions of the first kind is proposed for the arguments that are greater than unity in modulus. A well-known representation of these functions is refined and used for this purpose. The constructs and the software implementation proposed in the paper provide an efficient tool for the calculation of the functions with a desired accuracy in a wide range of parameters.  相似文献   
127.
1H-Pyrazoles, triazoles, and imidazoles in reaction with ethoxycarbonylimine and arylsulfonylimines of chloral yield addition products, corresponding 1-(1-amidotrichloroethyl)azoles. Derivatives of 1-alkylpyrazoles and pyrazolones react with chloral 4-chlorophenylsulfonylimine to furnish products of C-amidotrichloroethylation into position 4 of the azole ring.  相似文献   
128.
 In this contribution we consider a phenomenon of metastable states in antiprotonic helium atoms, precise spectroscopy of these states and a present-day study of the electromagnetic properties of antiprotons. Received October 16, 2001; accepted for publication November 13, 2001  相似文献   
129.
The effect of hydrogen on the photoluminescence and planar conductivity of GaAs/InGaAs quantum-well heterostructures with an island Pd layer at the anodically oxidized surface was studied. Unlike continuous deposited Pd layers, island layers do not cause the formation of defects in the GaAs surface region and yet the Pd layer maintains high catalytic activity with respect to hydrogen. It is found that the thermal treatment of such a structure in a hydrogen atmosphere causes atomic-hydrogen passivation of the defects in quantum wells. Studies of the characteristics of planar photoresistors with an island Pd layer acting as hydrogen sensors show that their hydrogen detectivity is approximately two orders of magnitude higher than that of diode structures with continuous Pd layers.  相似文献   
130.
It was shown that the reaction of o-hyroxyphenyldiphenylmethanol with benzaldehyde labeled with 17O and 18O isotopes proceeds in such a way that oxygen atoms of the starting phenoloalcohol are retained.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 632–633, May, 1991.  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