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   202121篇
  免费   2266篇
  国内免费   500篇
化学   110655篇
晶体学   3648篇
力学   7998篇
综合类   11篇
数学   19229篇
物理学   63346篇
  2020年   1730篇
  2019年   1924篇
  2018年   2239篇
  2017年   2359篇
  2016年   3526篇
  2015年   2201篇
  2014年   3557篇
  2013年   9086篇
  2012年   6520篇
  2011年   8027篇
  2010年   5701篇
  2009年   5660篇
  2008年   7160篇
  2007年   7068篇
  2006年   6708篇
  2005年   6060篇
  2004年   5527篇
  2003年   5101篇
  2002年   4867篇
  2001年   6141篇
  2000年   4623篇
  1999年   3518篇
  1998年   2745篇
  1997年   2703篇
  1996年   2591篇
  1995年   2440篇
  1994年   2331篇
  1993年   2165篇
  1992年   2826篇
  1991年   2730篇
  1990年   2673篇
  1989年   2691篇
  1988年   2715篇
  1987年   2722篇
  1986年   2592篇
  1985年   3304篇
  1984年   3313篇
  1983年   2599篇
  1982年   2713篇
  1981年   2765篇
  1980年   2533篇
  1979年   2875篇
  1978年   2863篇
  1977年   2980篇
  1976年   2818篇
  1975年   2553篇
  1974年   2509篇
  1973年   2465篇
  1972年   1703篇
  1968年   1703篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
Ethynylated polystyrene resins were prepared as functionalized polymer supports by the iodination reaction of macroporous polystyrene resins and reacted with transition metal diethynyl complex (Mt = Ni) and metal halides (Mt = Rh, Pd, and Pt) in a basic solvent using cuprous iodide as a catalyst to obtain macroporous polystyrene resins containing organotransition metals. The distribution of the metal acetylide complexes in the modified macroporous resins was determined by an electron probe microanalyzer. A gradient in the transition metal distribution was observed in any case of the modified resins. The stability of the organotransition metal complexes in the polymer matrix could be compared with a low molecular weight analogous complex quantitatively.  相似文献   
982.
The coupled-channel optical method is used to study positron scattering by atomic lithium at energies ranging from the ionization threshold to 60eV, The present method simultaneously treats the target channels and the positronium (Ps) channels in the coupled-channel method together with the continuum effects via an ab-initio optical potential. Ionization, elastic and inelastic cross sections in target channels, and the total cross section are also reported and compared with other theoretical and experimental data. A comparative study with the corresponding electron-lithium data is also reported.  相似文献   
983.
This is the report of flavor physics and model building working group at WHEPP-9. While activites in flavor physics have been mainly focused on B-physics, those in model building have been primarily devoted to neutrino physics. We present summary of working group discussions carried out during the workshop in the above fields, and also briefly review the progress made in some projects subsequently.  相似文献   
984.
985.
986.
987.
One important goal of the ILIMA project at FAIR is the study of masses and decay properties of relativistic isomeric beams stored and cooled in the planned storage-ring complex. A new scheme is described, where a storage-cooler ring is used for high-resolution mass separation. Experimental results on the separation of the isobaric pair 140Pr-140Ce are presented. P. Beller, deceased.  相似文献   
988.
Mechanisms for the formation of toxisterol A are suggested. The connection between the conformation of the initial previtamin and the stereochemistry of the reaction products is discussed.Lensoviet Leningrad Technological Institute. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 225–229, March–April, 1989.  相似文献   
989.
The deposition caused by suspended sediments in three points at the Seman river mouth was determined by means of137Cs. The soil pollution with this radionuclide, caused by the Chernobyl accident is given, too.  相似文献   
990.
V K B Kota  K Kar 《Pramana》1989,32(5):647-692
The subject of spectral distribution methods where one derives and applies the locally smoothed forms of observables in nuclei is briefly reviewed. It is well understood that the local forms (with respect to energy) of the level density function, expectation values and strength densities are Gaussian, linear (or ratio of Gaussians) and a bivariate Gaussian respectively. To accomodate symmetries in the above forms, one has to deal with multivariate distributions in general; for example the angular-momentum (J) decomposition leads to a bivariate Gaussian form for the level density. These results extend to indefinitely large spaces by method of partitioning and they generate convolution forms. The origin of these remarkable spectral properties is discussed and shell model examples are given to substantiate their applicability to nuclear systems. Spectral distribution theory is a practical, usable theory because the smoothed forms are defined in terms of traces of low particle-rank operators, and the trace information propagates. Finally we discuss the application of the spectral methods for a wide range of nuclear problems; these include binding energies, orbit occupancies, electromagnetic andβ-decay sum rule quantities, analysis of operators, symmetry breaking, numerical level densities, and determination of bounds on time-reversal non-invariant part of nucleon-nucleon interaction.  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