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   17461篇
  免费   2976篇
  国内免费   1258篇
化学   3644篇
晶体学   57篇
力学   2453篇
综合类   458篇
数学   7515篇
物理学   7568篇
  2024年   29篇
  2023年   225篇
  2022年   417篇
  2021年   636篇
  2020年   526篇
  2019年   438篇
  2018年   412篇
  2017年   667篇
  2016年   744篇
  2015年   584篇
  2014年   1073篇
  2013年   1385篇
  2012年   1020篇
  2011年   1184篇
  2010年   947篇
  2009年   1076篇
  2008年   1164篇
  2007年   1113篇
  2006年   988篇
  2005年   848篇
  2004年   677篇
  2003年   738篇
  2002年   660篇
  2001年   539篇
  2000年   522篇
  1999年   479篇
  1998年   424篇
  1997年   377篇
  1996年   300篇
  1995年   226篇
  1994年   213篇
  1993年   183篇
  1992年   126篇
  1991年   101篇
  1990年   93篇
  1989年   62篇
  1988年   57篇
  1987年   58篇
  1986年   59篇
  1985年   48篇
  1984年   57篇
  1983年   24篇
  1982年   48篇
  1981年   34篇
  1980年   23篇
  1979年   21篇
  1978年   14篇
  1977年   14篇
  1976年   7篇
  1957年   6篇
排序方式: 共有10000条查询结果,搜索用时 609 毫秒
971.
A test problem generator, by means of neural networks nonlinear function approximation capability, is given in this paper which provides test problems, with many predetermined local minima and a global minimum, to evaluate nonlinear programming algorithms that are designed to solve the problem globally.  相似文献   
972.
本文对蔡少棠[1 ] ,[2 ] 等提出的非线性规划神经网络作了改进 ,使得该神经网络适合于通用VLSI技术实现 .  相似文献   
973.
    
This paper uses the moiré interferometry of sticking film in synchronous measurement of 2-D displacements for determining the stress intensity factors of mixed mode. The calculating formula of mixed mode SIF of a beam with an oblique crack has been derived, which can be applied to the general cases in 2-D questions of mixed mode crack. This result is of extensive value for application to engineering questions that has no analytic solutions and numerical value solutions.Projects Supported by Foundation of Natural Sciences of China.  相似文献   
974.
实验表明,在TE011模式园柱形腔中,不但可以使用扁平样品管测量水溶液样品的ESR波谱,而且获得好的腔品质因子Q和高品质的ESR信号。所观察到的信号高度,是使用最佳尺寸毛细管样品时最大信号高度的3.2倍;又是在具有波导尺寸的TE102腔中使用扁平样品管时所获得信号高度的3倍。本文对此作了定性的理论分析。  相似文献   
975.
The analysis of random graphs developed by the author, principally as a model for polymerization processes, is extended to the case of directed random graphs, with models of neural nets in mind. The principal novelty of the directed case is the representation of the partition function by a complex rather than a real integral, and the replacement of simple maxima in asymptotic evaluations by an interesting form of saddle point.  相似文献   
976.
We give a linear-time algorithm to find a feasible flow in a strongly connected network with fixed supplies and demands, each summing to a common value that is at most the minimum arc capacity. This algorithm speeds up the Goldberg-Rao maximum flow method by a constant factor.  相似文献   
977.
We investigate the behavior of a two-level quantum system in contact with a classical heat bath, e.g., a solute particle with internal degrees of freedom immersed in a solvent of massive particles. Using a combination of analytical and numerical methods, we obtain precise information about localization, time-displaced correlation functions, and the frequency-dependent susceptibility of such solute particles. We find that these quantities can have a strong dependence on the density of the solvent fluid, with the maximum changes from the behavior of the corresponding isolated quantum system occurring in many cases at very low densities. We compare the exact results with those obtained by path integral Monte Carlo. There is good agreement with the imaginary time correlations, but analytic continuation to real time proves elusive: even with the best numerical data on the former, we can only get very gross features of the latter.  相似文献   
978.
In this paper we derive the Integration-by-Parts Formula using the generalized Riemann approach to stochastic integrals, which is called the Ito-Kurzweil-Henstock integral.  相似文献   
979.
On the problem of crack system with an elliptic hole   总被引:1,自引:0,他引:1  
The problem of cracks with an elliptic hole in an infinite plane is investigated. By introducing the fictitious loads on the hole edge and using the Muskhelishvili method, the problem is reduced to solving a system of mixed-type integral equations in which some are Fredholm equations but others Cauchy-type singular ones. A numerical method is suggested and can be used for the treatment of other similar equations. The numerical results for some typical examples are given, showing that the method is really effective.  相似文献   
980.
We suggest a new construction of nonlocal representations of the current group. Instead of the Fock space, which is usually used in this situation, we consider the direct integral of countable tensor products of representations over the trajectories of some stochastic process. The construction substantially uses the invariance of the so-called infinite-dimensional Lebesgue measure.  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