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   237945篇
  免费   2377篇
  国内免费   833篇
化学   120327篇
晶体学   4047篇
力学   10890篇
综合类   1篇
数学   26459篇
物理学   79431篇
  2020年   1825篇
  2019年   2103篇
  2018年   2773篇
  2017年   2694篇
  2016年   4022篇
  2015年   2496篇
  2014年   4073篇
  2013年   10369篇
  2012年   7769篇
  2011年   9681篇
  2010年   6816篇
  2009年   6762篇
  2008年   8966篇
  2007年   9019篇
  2006年   8515篇
  2005年   7771篇
  2004年   7143篇
  2003年   6361篇
  2002年   6276篇
  2001年   7182篇
  2000年   5453篇
  1999年   4310篇
  1998年   3623篇
  1997年   3554篇
  1996年   3379篇
  1995年   3080篇
  1994年   3019篇
  1993年   3099篇
  1992年   3199篇
  1991年   3390篇
  1990年   3132篇
  1989年   3090篇
  1988年   3136篇
  1987年   3010篇
  1986年   2851篇
  1985年   3880篇
  1984年   4091篇
  1983年   3260篇
  1982年   3492篇
  1981年   3423篇
  1980年   3311篇
  1979年   3401篇
  1978年   3492篇
  1977年   3417篇
  1976年   3512篇
  1975年   3194篇
  1974年   3195篇
  1973年   3226篇
  1972年   2256篇
  1971年   1861篇
排序方式: 共有10000条查询结果,搜索用时 321 毫秒
191.
We calculate the leading and next-to-leading logarithmic resummed distribution for the jet broadening in deep inelastic scattering, as well as the power correction for both the distribution and mean value. A truncation of the answer at NLL accuracy, as is standard, leads to unphysical divergences. We discuss their origin and show how the problem can be resolved. We then examine DIS specific procedures for matching to fixed order calculations and compare our results to the data. One of the tools developed for the comparison is an NLO parton distribution evolution code. When compared to PDF sets from MRST and CTEQ it reveals limited discrepancies in both. Received: 16 October 2001 / Published online: 12 April 2002  相似文献   
192.
The circular dichroism (CD) method has been used to study the stereochemistry of the bisbenzyltetrahydroisoquinoline alkaloids. A relationship has been established between the absolute configurations of the asymmetric centers and the parameters of the Cotton effects in the CD spectra. The changes in the CD spectra on protonation have been correlated with conformational rearrangements of the molecules due to the different attachment of the oxygen bridges.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 818–823, November–December, 1979.  相似文献   
193.
Compositions of generalized fractional integral operators involving Gauss hy-pergeometric function with power weights are studied. Composition formulas for such integrals which are the operators of the same type are obtained. In parti-cular, compositions of two identical operators are given.  相似文献   
194.
195.
It is proved that biorthogonal polynomials obey two different kinds of Christoffel-Darboux-type formulae, one linking polynomials with a different parameter and one combining polynomials with different degrees. This is used to produce a mixed recurrence relation, which is valid for all biorthogonal polynomials. This recurrence relation establishes several results on interlacing property of zeros of successive biorthogonal polynomials and leads to a new result on the interlace of zeros of orthogonal polynomials (of equal degrees) with respect to two distributionsdψ(x) andx p dψ(x), 0<p≤1, with support in either [0, 1] or [1, ∞).  相似文献   
196.
197.
198.
Consider an organization with several categories of staff, each having a specified number of members. The age of entry into service and the age of retirement are both specified. Withdrawals occur at time-independent rates. Under this set-up, the authors have computed the maximum ages at which promotions should take place, assuming that the staff members continuing at various ages are random. Some illustrative calculations have been carried out.  相似文献   
199.
The aggregate error locator is defined and a computation method is given. The aggregate error locator is then used in a type of Forney algorithm to compute the error values in the received words of a Ca,b algebraic geometry code.  相似文献   
200.
In the field of industrial vision, the 3D inspection of highly reflective metallic objects is still a delicate task. The specular reflections prevent the use of a 3D laser scanner, whereas the phase shifting-based 3D systems are more adapted to inspect surfaces with low curvature. This paper deals with a new automated 3D inspection system based on polarization analysis. Studying the state of polarization of the reflected light is very useful for obtaining information on the normals of the surface. An extension of the shape from polarization method from dielectric to metallic surfaces is demonstrated. Then, an improved relaxation algorithm is provided in order to reconstruct the shape from the normal field given by the polarization analysis. Finally, applications to shape defect detection are discussed and the efficiency of the system in discriminating defects on highly reflective metallic objects made by stamping and polishing is presented. The text was submitted by the authors in English.  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