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   173925篇
  免费   2421篇
  国内免费   729篇
化学   94195篇
晶体学   2497篇
力学   7698篇
综合类   7篇
数学   18152篇
物理学   54526篇
  2021年   1019篇
  2020年   1164篇
  2019年   1174篇
  2018年   1197篇
  2017年   1199篇
  2016年   2418篇
  2015年   1979篇
  2014年   2564篇
  2013年   7875篇
  2012年   6478篇
  2011年   8189篇
  2010年   4986篇
  2009年   5123篇
  2008年   7529篇
  2007年   7532篇
  2006年   7244篇
  2005年   6755篇
  2004年   6018篇
  2003年   5176篇
  2002年   5062篇
  2001年   6073篇
  2000年   4605篇
  1999年   3509篇
  1998年   2657篇
  1997年   2654篇
  1996年   2615篇
  1995年   2307篇
  1994年   2197篇
  1993年   2049篇
  1992年   2371篇
  1991年   2335篇
  1990年   2055篇
  1989年   2029篇
  1988年   2046篇
  1987年   1972篇
  1986年   1886篇
  1985年   2794篇
  1984年   2787篇
  1983年   2236篇
  1982年   2425篇
  1981年   2301篇
  1980年   2247篇
  1979年   2190篇
  1978年   2266篇
  1977年   2211篇
  1976年   2143篇
  1975年   2129篇
  1974年   2037篇
  1973年   2118篇
  1972年   1201篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Preface     
  相似文献   
102.
103.
TGA, DTA and DSC analyses indicate that benzotriazole is significantly more stable thermally than 1,2,3-triazole.  相似文献   
104.
Well-Posedness by Perturbations of Variational Problems   总被引:3,自引:0,他引:3  
In this paper, we consider the extension of the notion of well-posedness by perturbations, introduced by Zolezzi for optimization problems, to other related variational problems like inclusion problems and fixed-point problems. Then, we study the conditions under which there is equivalence of the well-posedness in the above sense between different problems. Relations with the so-called diagonal well-posedness are also given. Finally, an application to staircase iteration methods is presented.  相似文献   
105.
The mass power spectrum for a Universe dominated by the Chaplygin gas is evaluated numerically from scales of the order of the Hubble horizon to 100 Mpc. The results are compared with a pure baryonic Universe and a cosmological constant model. In all three cases, the spectrum increases with k, the wavenumber of the perturbations. The slope of the spectrum is higher for the baryonic model and smaller for the cosmological constant model, the Chaplygin gas interpolating these two models. The results are analyzed in terms of the sound velocity of the Chaplygin gas and the moment the Universe begins to accelerate.  相似文献   
106.
Deformation quantization, which achieves the passage from classical mechanics to quantum mechanics by the replacement of the pointwise multiplication of functions on phase space by the star product, is a powerful tool for treating systems involving bosonic degrees of freedom, both in quantum mechanics and in quantum field theory. In the present paper we show how these methods may be naturally extended to systems involving fermions. In particular we show how supersymmetric quantum mechanics can be formulated in this approach and consider examples involving both non-relativistic and relativistic systems.  相似文献   
107.
We show that if A is an abelian compact Lie group, all A-equivariant complex vector bundles are orientable over a complex orientable equivariant cohomology theory. In the process, we calculate the complex orientable homology and cohomology of all complex Grassmannians. Received: 14 February 2000; in final form: 4 August 2000 / Published online: 19 October 2001  相似文献   
108.
This paper presents an adaptive memory-based method for solving the Capacitated Vehicle Routing Problem (CVRP), called BoneRoute. The CVRP deals with the problem of finding the optimal sequence of deliveries conducted by a fleet of homogeneous vehicles, based at one depot, to serve a set of customers. The computational performance of the BoneRoute was found to be very efficient, producing high quality solutions over two sets of well known case studies examined.  相似文献   
109.
The Wheeler–DeWitt equation of arbitrary Hartle–Hawking factor ordering for several minisuperspace universe models, such as the pure gravity Friedmann–Robertson–Walker and Taub ones, is mapped onto the dynamics of corresponding classical oscillators. The latter ones are studied by the classical Ermakov invariant method, which is a natural approach in this context. For the more realistic case of a minimally coupled massive scalar field, one can study, within the same type of approach, the corresponding squeezing features as a possible means of describing cosmological evolution. Finally, we comment on the analogy with the accelerator physics.  相似文献   
110.
Recursive algorithms for the computation of standard deviation and average deviation are derived and their applications in data acquisition are discussed. The relative speeds and accuracies of the two algorithms are compared for synthetic data. The performance of recursive estimation under shot and proportional noise limitations is also described. As an example of the utility of these algorithms, absorbance data with constant confidence intervals are collected regardless of incident and transmitted intensities. The desired precision is specified prior to data acquisition and used to control signal-averaging of the data in real time.  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