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   340515篇
  免费   3396篇
  国内免费   344篇
化学   164865篇
晶体学   3960篇
力学   18336篇
综合类   3篇
数学   49117篇
物理学   107974篇
  2021年   3539篇
  2020年   4045篇
  2019年   4799篇
  2018年   7163篇
  2017年   7199篇
  2016年   9354篇
  2015年   4822篇
  2014年   8175篇
  2013年   14809篇
  2012年   13234篇
  2011年   15004篇
  2010年   11885篇
  2009年   11680篇
  2008年   14117篇
  2007年   13923篇
  2006年   12400篇
  2005年   10942篇
  2004年   10356篇
  2003年   9389篇
  2002年   9442篇
  2001年   8453篇
  2000年   6725篇
  1999年   4950篇
  1998年   4631篇
  1997年   4401篇
  1996年   3996篇
  1995年   3493篇
  1994年   3618篇
  1993年   3637篇
  1992年   3648篇
  1991年   4005篇
  1990年   3966篇
  1989年   3965篇
  1988年   3700篇
  1987年   3771篇
  1986年   3435篇
  1985年   4137篇
  1984年   4332篇
  1983年   3629篇
  1982年   3930篇
  1981年   3616篇
  1980年   3333篇
  1979年   3811篇
  1978年   3893篇
  1977年   4019篇
  1976年   4138篇
  1975年   3828篇
  1974年   3723篇
  1973年   3881篇
  1972年   3244篇
排序方式: 共有10000条查询结果,搜索用时 359 毫秒
991.
We study the conjugate boundary-value problem with boundary conditions whose orders can be as large as the order of the differential equation or larger. We construct the Green's function of the problem over the entire space when the separating surface is a hyperplane, and we describe its properties. Bibliography: 6 titles.Translated fromMatematicheskie Metody i Fiziko-Mekhanicheskie Polya, Issue 30, 1989, pp. 20–24.  相似文献   
992.
A. V. Pomyalov  I. Laulicht  J. Barak 《Physica A》1993,200(1-4):267-277
The microwave subsidiary absorption threshold in tangentially magnetized yttrium-iron-garnet (YIG) films was measured as a function of the static magnetic field, film thickness and decrease in the 0.3–3 μm range is observed. The effect is explained quantitatively by using modified Damon-Eshbach dispersion relations which take into account exchange interactions.

The effect of temperature on hcrit, the smallest threshold field amplitude, in the 250<T< 450 K temperature range can be expressed by an empirical relationship hcrit Ms(T)-1.6 where Ms is the saturation magnetization. This hcrit vs Ms relationship is similar to that obtained for the magnetization dependence of parallel pump thresholds in Li-Ti ferrite compounds.  相似文献   

993.
Chemiluminescence (CL) was found upon the isomerization of dimethyldioxirane in the gas phase under argon atmosphere. The intensity of CL increases as temperature increases and decreases with time at constant temperature. If Silipor is placed in a cell containing the dimethyldioxirane vapor in argon, the intensity of CL sharply increases (more than 10 times) and then decreases following the exponential law. In all cases tripletly excited methyl acetate is the emitter of chemiluminescence.[/ p]Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2582–2583, October 1996.  相似文献   
994.
On the basis of the general class of solutions of 6D vacuum Einstein equations and using well-known results of the 6D geometric model of electroweak and gravitational interactions, the variations of fundamental physical constants and their influence on the observed red-shift of galaxies are investigated. By considering the interpretation of extra components of the 6D metric as reproducing the properties of matter in the 4D curved space-time, the effective quantities of matter are obtained. In particular, the states of dust and radiation are shown. The corresponding 5D models were also investigated.  相似文献   
995.
We prove that in some reasonable sense, every possible physical law can be reformulated in terms of symmetries. This result explains the well-known success of the group-theoretic approach in physics.  相似文献   
996.
997.
We consider an elastic isotropic material containing a fibrous inclusion or a void subject to loads. We study the possibility of increasing the strength of the material using “control action.” As examples of such actions we consider an additional external load, application of pressure in the cavities (voids), and variation of the temperature of uniform heating of the medium with the inclusions. Studies are carried out for two-dimensional problems of linear elasticity theory. From the class of all possible actions we single out a subclass leading to states of equal strength along the phase interface. We study the efficiency of these types of action and show that in certain cases they lead to a manifold increase in the strength of the material. We give the results of numerical studies. Translated fromTeoreticheskaya i Prikladnaya Mekhanika, No. 24, 1993, pp. 15–19.  相似文献   
998.
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, No. 4, pp. 108–112, July–August, 1993.  相似文献   
999.
1000.
The synthesis has been effected of derivatives of MDP having a spacer with an amino or carboxy group. The final stage of the synthesis was the condensation of Boc-L-Ala-D-iGln with 6-aminohexanol (followed by the two-stage replacement of the hydroxy by an azido group) or with benzyl 6-aminohexanoate.Simferopol' State University. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 122–125, January–February, 1993.  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