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   8567篇
  免费   282篇
  国内免费   3篇
化学   4407篇
晶体学   63篇
力学   198篇
数学   1863篇
物理学   2321篇
  2022年   70篇
  2021年   107篇
  2020年   129篇
  2019年   128篇
  2018年   161篇
  2017年   161篇
  2016年   341篇
  2015年   310篇
  2014年   345篇
  2013年   611篇
  2012年   446篇
  2011年   521篇
  2010年   325篇
  2009年   266篇
  2008年   301篇
  2007年   273篇
  2006年   198篇
  2005年   104篇
  2004年   125篇
  2003年   134篇
  2002年   130篇
  2001年   120篇
  2000年   130篇
  1999年   116篇
  1998年   111篇
  1997年   102篇
  1996年   92篇
  1995年   83篇
  1994年   84篇
  1993年   82篇
  1992年   84篇
  1991年   71篇
  1990年   85篇
  1989年   74篇
  1988年   76篇
  1987年   74篇
  1985年   95篇
  1984年   108篇
  1983年   70篇
  1982年   92篇
  1981年   94篇
  1980年   82篇
  1979年   97篇
  1978年   91篇
  1977年   78篇
  1976年   101篇
  1975年   93篇
  1974年   92篇
  1973年   71篇
  1968年   74篇
排序方式: 共有8852条查询结果,搜索用时 407 毫秒
171.
Let(X i ) be a martingale difference sequence. LetY be a standard normal random variable. We investigate the rate of uniform convergence
  相似文献   
172.
It is proved that the even-order equationy (2n) +p(t)y=0 is (n,n) oscillatory at if
  相似文献   
173.
The q--algebra, i.e., the system of sets closed under complementation, countable disjoint unions, and containing the empty set, generated by the system of open balls coincides with the -field of Borel sets inR sun forn=1,2, and 3. A first step to extend the proof forn=4, 5, 6, and 7 is indicated.  相似文献   
174.
The encapsulation of fine magnetite particles of 10 nm size and marker ANS within asolectin vesicles has been made by sonication of the mixture in water. For the proof of encapsulation of magnetite in vesicles the electron microscope and spectrofluoriphotometer technique were used. The theory for the calculation of the magnetic force acting on the system consisted of non-capsulated magnetic particles dispersed in water and magnetic vesicles was developed.This work was supported by the Slovak Academy of Sciences within the framework of Project GAV No. 1361.  相似文献   
175.
In this paper large-scale properties of developed magnetohydrodynamic turbulence have been investigated by using double expansion method in the frame of quantum field renormalization group. It has been shown that universal kinetic scaling regime exists, but the double expansion in general leads to qualitatively different results than those provided by the usual -expansion treatment.This work was supported by Slovak Grant Agency for Science.  相似文献   
176.
The radionuclides54Mn,60Co,90Sr,95Nb,95Zr,103Ru,106Ru,125Sb,131I,134Cs,137Cs,140Ba,144Ce,226Ra and228Ac have been studied in the Sava River environment since the Chernobyl accident in 1986. The measured periphyton concentration ratios (CR) for each radionuclide were correlated with the measured sediment distribution coefficients (Kd) for that radionuclide. The Kd-CR relationships obtained were defined by the equation ln Kd=–0.5 ln CR +7.4. These Kd-CR relationships were assumed to be referable to the Sava River ecosystem and were used to predict the missing soil Kd values and/or the missing CR values for the wide range of radionuclides, respectively. Moreover, the Kd-CR relationship characteristic for the Sava River ecosystem was compared with the Kd-CR relationship proposed by Baes1 and by Shepard2. The characterization of the partition coefficients in the Sava River environment and understanding of the mechanisms affecting radionuclide retardation and bioaccumulation are required for the planning of radioactive waste depositories in the area.  相似文献   
177.
Summary The electrochemical reduction of the Fe(III) complexes with a series of substituted N,N-Ethylenebisacetonimines was investigated by cyclic voltammetry in acetonitrile solution at a platinum electrode. The substituent does not significantly influence the redox properties of the studied complexes. The symmetry of the redox orbital is responsible for the observed behaviour of the complexes.
Elektrochemisches Verhalten einer Reihe von Fe(III)-Komplexen mit vierzähnigen Schiffschen Basen als Liganden
Zusammenfassung Die elektrochemische Reduktion der Fe(III)-Komplexe einer Reihe von substituierten N,N-Ethylenbisacetoniminen wurde mittels cyclischer Voltammetrie in Acetonitril an einer Platinelektrode untersucht. Der Substituent beeinflußt die Redoxeigenschaften der untersuchten Komplexe nicht signifikant. Das beobachtete Verhalten der Komplexe wird von der Symmetrie des Redoxorbitals bestimmt.
  相似文献   
178.
The Boussinesq approximation, where the viscosity depends polynomially on the shear rate, finds more and more frequent use in geological practice. In the paper, this modified Boussinesq approximation is investigated as a dynamical system for which the existence of a global attractor is proved. Finally, a new criterion for estimating the fractal dimension of invariant sets is formulated and its application to the problem under consideration is illustrated.  相似文献   
179.
On the ground of four axioms we define thekinematics of perfectly elastic bodies and in particular the notion ofweak deformations of a perfectly elastic body. Weak deformations turn out to agree withweak diffeomorphisms introduced in [10], a class of rectifiable currents which enjoys good closure and compactness properties. Defining thedynamics of perfectly elastic bodies in terms of twoconstitutive conditions on the stored energy function, we can therefore prove existence of stable equilibrium weak deformations for mixed boundary value problems, which moreover satisfy equilibrium and conservation equations.This work has been partially supported by the Ministero dell'Universitá e della Ricerca Scientifica, by C.N.R. contract n. 91.01343.CT01, by the European Research Project GADGET, and by Grant n.11957 of the zech Acad. of Sciences.This article was processed by the author using the LaTEX style filepljour1 from Springer-Verlag.  相似文献   
180.
We give a necessary and sufficient condition for a Bell-type inequality to hold in a horizontal sum of finitely many finite Boolean algebras.  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