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   917篇
  免费   20篇
  国内免费   10篇
化学   571篇
晶体学   6篇
力学   7篇
数学   57篇
物理学   306篇
  2023年   4篇
  2022年   6篇
  2020年   5篇
  2019年   11篇
  2018年   4篇
  2016年   11篇
  2015年   15篇
  2014年   15篇
  2013年   30篇
  2012年   50篇
  2011年   44篇
  2010年   29篇
  2009年   41篇
  2008年   40篇
  2007年   40篇
  2006年   43篇
  2005年   43篇
  2004年   37篇
  2003年   33篇
  2002年   41篇
  2001年   27篇
  2000年   43篇
  1999年   8篇
  1998年   10篇
  1997年   9篇
  1996年   14篇
  1995年   17篇
  1994年   23篇
  1993年   9篇
  1992年   14篇
  1991年   7篇
  1990年   7篇
  1989年   13篇
  1988年   13篇
  1987年   11篇
  1986年   8篇
  1985年   20篇
  1984年   6篇
  1983年   11篇
  1982年   8篇
  1981年   12篇
  1980年   7篇
  1979年   12篇
  1978年   9篇
  1977年   6篇
  1976年   7篇
  1975年   9篇
  1974年   7篇
  1973年   9篇
  1972年   13篇
排序方式: 共有947条查询结果,搜索用时 15 毫秒
841.
A radiometric study of the kinetics of the displacement reaction between nickel(II) and65Zn-labeled zinc salt of ethylenediaminetetraacetic acid, which was previously used by the authors for the analysis of trace quantities of nickel, has been carried out under varying conditions of temperature, pH etc. The above reaction was confirmed to be first order with respect to both Ni2+ and to*ZnEDTA. The overall reaction rate constant, kf, has been shown to be inversely proportional to the concentration of Zn2+ and directly proportional to the concentration of H+. From the dependence of the rate constant on the concentration of Zn2+ and H+ a three-step mechanism is proposed for the above reaction. The values for Ea, ΔH, ΔG and ΔS for the overall reaction have been computed from the experimental data.  相似文献   
842.
The 2P12-2P32 fine structure transition in the ground (3p5) state of the argon atomic ion. Ar+, has been detected in absorption using a tunable diode laser. The transition was calibrated against water vapour lines and measured to be 1431.644 ± 0.001 cm?1 in 40Ar+ and 3.0 × 10?3 cm?1 (91 MHz) smaller in 36Ar+.  相似文献   
843.
A large number of coded items such as bank checks are initially mixed randomly. It is desired to sort them into k categories using a sorting device with m pockets (m < k). Several possible objectives are noted, and a new criterion oriented to the average time until categories are sorted out is analyzed. A simple strategy is shown to minimize the average number of sorting passes that elapse until an item is sorted out.  相似文献   
844.
845.
846.
847.
The guanidinium group is found in many natural products and has been extensively incorporated into various drug designs as well as artificial receptor structures. In this paper we critically review the various synthetic routes to guanidiniums and describe a novel approach that allows the mild formation of multi-substituted derivatives.  相似文献   
848.
We extend the topos-theoretic treatment given in previous papers of assigningvalues to quantities in quantum theory, and of related issues such as theKochen–Specker theorem. This extension has two main parts: the use of vonNeumann algebras as a base category and the relation of our generalized valuationsto (i) the assignment to quantities of intervals of real numbers and (ii) the ideaof a subobject of the coarse-graining presheaf.  相似文献   
849.
将最近从地瓜中提出来的低分子量紫色酸性磷酸酶(smPAP)基因克隆到GST融合蛋白表达载体pGEX-2T中,在大肠杆菌BL21codon plus中进行表达,用表达的融合蛋白免疫兔子产生多克隆抗体,用抗血清在昆虫细胞中表达的smPAP和地瓜提取液中分离纯化的PAP进行检测,产生了良好的交叉反应。  相似文献   
850.
In this paper we describe a construction which produces classes in compactifications of the moduli space of curves. This construction extends a construction of Kontsevich which produces classes in the open moduli space from the initial data of a cyclic A -algebra. The initial data for our construction are what we call a ‘quantum A -algebra’, which arises as a type of deformation of a cyclic A -algebra. The deformation theory for these structures is described explicitly. We construct a family of examples of quantum A -algebras which extend a family of cyclic A -algebras, introduced by Kontsevich, which are known to produce all the kappa classes using his construction.   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