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   369464篇
  免费   4150篇
  国内免费   943篇
化学   188753篇
晶体学   5553篇
力学   16194篇
综合类   8篇
数学   46428篇
物理学   117621篇
  2021年   3541篇
  2020年   3911篇
  2019年   4291篇
  2018年   6038篇
  2017年   6198篇
  2016年   8836篇
  2015年   5364篇
  2014年   8168篇
  2013年   18523篇
  2012年   14768篇
  2011年   17080篇
  2010年   12496篇
  2009年   12165篇
  2008年   15183篇
  2007年   14970篇
  2006年   13745篇
  2005年   12198篇
  2004年   11249篇
  2003年   9852篇
  2002年   9725篇
  2001年   11134篇
  2000年   8429篇
  1999年   6514篇
  1998年   5404篇
  1997年   5161篇
  1996年   4961篇
  1995年   4216篇
  1994年   4237篇
  1993年   4078篇
  1992年   4507篇
  1991年   4647篇
  1990年   4477篇
  1989年   4320篇
  1988年   4095篇
  1987年   4198篇
  1986年   3963篇
  1985年   4997篇
  1984年   5041篇
  1983年   4159篇
  1982年   4265篇
  1981年   3989篇
  1980年   3898篇
  1979年   4158篇
  1978年   4137篇
  1977年   4132篇
  1976年   4132篇
  1975年   3888篇
  1974年   3843篇
  1973年   3894篇
  1972年   2730篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
Summary We have estimated and measured the daily thermal expansion of an oceanographic platform. This has been found negligible as far as the calibration of a satellite altimeter is concerned.  相似文献   
132.
We study initial boundary value problems for linear scalar evolutionpartial differential equations, with spatial derivatives ofarbitrary order, posed on the domain {t > 0, 0 < x <L}. We show that the solution can be expressed as an integralin the complex k-plane. This integral is defined in terms ofan x-transform of the initial condition and a t-transform ofthe boundary conditions. The derivation of this integral representationrelies on the analysis of the global relation, which is an algebraicrelation defined in the complex k-plane coupling all boundaryvalues of the solution. For particular cases, such as the case of periodic boundaryconditions, or the case of boundary value problems for even-orderPDEs, it is possible to obtain directly from the global relationan alternative representation for the solution, in the formof an infinite series. We stress, however, that there existinitial boundary value problems for which the only representationis an integral which cannot be written as an infinite series.An example of such a problem is provided by the linearized versionof the KdV equation. Similarly, in general the solution of odd-orderlinear initial boundary value problems on a finite intervalcannot be expressed in terms of an infinite series.  相似文献   
133.
We obtain exponential upper bounds for tails of distributions of generalized L-statistics based on a sample from an exponential distribution. We prove the asymptotic normality of generalized L-statistics based on a sample from the uniform distribution on [0,1] and of L-statistics with decomposed kernels (without any restrictions on the sample distribution type).  相似文献   
134.
135.
The first stage in a multi-attribute value analysis is the development of a hierarchical structure of the attributes of the problem. This paper reports the process of developing such a structure for the problem of choosing a suitable mode of transport for radioactive waste. The initial hierarchy of attributes went through several stages of development as new insights emerged about the nature of the problem. Some of the reasons behind this restructuring are discussed, and several important questions about the structuring process are formulated.  相似文献   
136.
The {1/2, 0, 1/2} nuclear superstructure in an La0.93Sr0.07MnO3 manganite orthorhombic crystal is revealed using thermal-neutron diffraction. It is demonstrated that this superlattice belongs to the class of distortion-type structures and is directly associated with a 1/16-type ordering of Mn4+ and Mn3+ ions in a collinear ferromagnetic phase of the La0.93Sr0.07MnO3 manganite.  相似文献   
137.
The PARRNe facility has been used to produce neutron-rich isotopes 83,84Gaby the ISOL method. Their decay has been studied, and β-γ coincidence and γ-γ coincidence data were collected as a function of time. The first two excited levels in 83Ge and the first excited level in 84Ge have been measured for the first time.  相似文献   
138.
Journal of Experimental and Theoretical Physics - The magnetoresistance effect in the SmCu3Mn4O12 compound with a perovskite-like structure is investigated for the first time. It is found that an...  相似文献   
139.
A self-consistent, completely quantum calculation of the structure of the inner crust of neutron stars is carried out in the Wigner-Seitz approximation with a realistic phenomenological nuclear energy functional, where pair correlations of neutrons and protons are included in the explicit form. It has been shown that the superfluidity of neutrons and protons affects the structure of the ground state of the crust.  相似文献   
140.
We examine several interesting relationships and expressions involving Fourier-Feynman transform, convolution product and first variation for functionals in the Fresnel class F(B) of an abstract Wiener space B. We also prove a translation theorem and Parseval's identity for the analytic Feynman integral. This revised version was published online in June 2006 with corrections to the Cover Date.  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