全文获取类型
收费全文 | 14721篇 |
免费 | 472篇 |
国内免费 | 323篇 |
专业分类
化学 | 9247篇 |
晶体学 | 100篇 |
力学 | 405篇 |
综合类 | 30篇 |
数学 | 1895篇 |
物理学 | 3839篇 |
出版年
2022年 | 172篇 |
2021年 | 190篇 |
2020年 | 182篇 |
2019年 | 187篇 |
2018年 | 173篇 |
2017年 | 142篇 |
2016年 | 343篇 |
2015年 | 314篇 |
2014年 | 378篇 |
2013年 | 789篇 |
2012年 | 643篇 |
2011年 | 738篇 |
2010年 | 523篇 |
2009年 | 499篇 |
2008年 | 666篇 |
2007年 | 704篇 |
2006年 | 573篇 |
2005年 | 583篇 |
2004年 | 578篇 |
2003年 | 578篇 |
2002年 | 611篇 |
2001年 | 440篇 |
2000年 | 398篇 |
1999年 | 308篇 |
1998年 | 223篇 |
1997年 | 203篇 |
1996年 | 221篇 |
1995年 | 236篇 |
1994年 | 227篇 |
1993年 | 177篇 |
1992年 | 170篇 |
1991年 | 176篇 |
1990年 | 191篇 |
1989年 | 155篇 |
1988年 | 138篇 |
1987年 | 135篇 |
1986年 | 123篇 |
1985年 | 216篇 |
1984年 | 233篇 |
1983年 | 159篇 |
1982年 | 179篇 |
1981年 | 147篇 |
1980年 | 151篇 |
1979年 | 139篇 |
1978年 | 115篇 |
1977年 | 162篇 |
1976年 | 142篇 |
1975年 | 118篇 |
1974年 | 110篇 |
1973年 | 114篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
关于RNP和SCS的若干等价条件 总被引:1,自引:0,他引:1
使用切片方法,讨论了Banach空间中有界闭凸子集的RNP和SCS的若干等价条件. 相似文献
93.
Anne Boutet De Monvel-Berthier Louis Boutet De Monvel Gilles Lebeau 《Journal d'Analyse Mathématique》1992,58(1):39-60
Sans résumé
Dedicated to Professor Shmuel Agmon 相似文献
94.
New concepts for the study of incompressible plane or axisymmetric flows are analysed by the stream tube method. Flows without eddies and pure vortex flows are considered in a transformed domain where the mapped streamlines are rectilinear or circular. The transformation between the physical domain and the computational domain is an unknown of the problem. In order to solve the non-linear set of relevant equations, we present a new algorithm based on a trust region technique which is effective for non-convex optimization problems. Experimental results show that the new algorithm is more robust compared to the Newton-Raphson method. 相似文献
95.
Ram C. Maurya Deen D. Mishra Surendra K. Jaiswal Sudipta Mukherjee 《Transition Metal Chemistry》1992,17(5):381-383
Some new low-spin hexacoordinated cyanonitrosyl complexes of Cr1 of the type [Cr(NO)(CN)2(L)2(H2)], where L is an aromatic aldehyde oxime or Mannich base, have been prepared by the interaction or K3[Cr(NO)(CN)5]· H2O with L in aqueous AcOH, and characterized by a range of physico-chemical techniques, I.r. data suggest that all the oxime
derivatives and Mannich bases act as monodentate ligands by coordinating through the aromatic nitrogen.
TMC 2564 相似文献
96.
The paper deals with the global minimization of a differentiable cost function mapping a ball of a finite dimensional Euclidean space into an interval of real numbers. It is established that a suitable random perturbation of the gradient method with a fixed parameter generates a bounded minimizing sequence and leads to a global minimum: the perturbation avoids convergence to local minima. The stated results suggest an algorithm for the numerical approximation of global minima: experiments are performed for the problem of fitting a sum of exponentials to discrete data and to a nonlinear system involving about 5000 variables. The effect of the random perturbation is examined by comparison with the purely deterministic gradient method. 相似文献
97.
98.
99.
I T Vieira P R Harper A K Shahani V De Senna 《The Journal of the Operational Research Society》2003,54(7):713-722
Mother-to-child transmission (MTCT) of HIV is the most significant source of HIV infection in children below the age of 15 years. In 2000 alone, about 600 000 new infections occurred, the vast majority from mothers living in developing countries who were not aware of their HIV-positive status. To date, at least 4.3 million children have died from AIDS. In this paper, we discuss the development of an operational model that can be used to evaluate intervention options for the prevention of MTCT of HIV. The problem was approached by defining suitable pregnancy risk groups, prevention options and the required model outputs to evaluate different intervention strategies. The method chosen to approach the problem was a discrete-event, three-phase simulation, built in Visual Basic, with a stochastic semi-Markov structure. The developed model takes individual pregnant women through each stage of their pregnancy, labour and birth. Different intervention strategies may be modelled at any time, including short-course antiretroviral drugs and cessation of breastfeeding. The model is demonstrated with data from Botswana, which has one of the highest HIV-infection rates in the world. 相似文献
100.
Fabiana Quaglia Giuseppe Fusco Giuseppe De Rosa Francesca Ungaro Agnese Miro Maria Immacolata La Rotonda 《Journal of inclusion phenomena and macrocyclic chemistry》2007,57(1-4):669-674
The aim of this work was to produce lycopene-containing powders from tomato products by a solvent-free method making use of
β-cyclodextrin (βCD). Powders were prepared by spray-drying a tomato concentrate (TC), one of the most bioavailable form of
lycopene, after mechanical treatment with βCD in different weight ratios. The obtained product was centrifuged to eliminate
partly food matrix and characterized for the amount of lycopene hydrodispersed/hydrosolubilized in the aqueous fraction. The
chemical antioxidant activity of sera was evaluated too. Powders obtained by spray-drying sera exhibited good flow properties,
a lycopene content between 0.4 and 1.09 mg/g and excellent water dispersability. The process developed, which makes use of
βCD for the treatment of tomato products, turns to be of great interest to obtain a bulk material for nutraceuticals displaying
superior biovailability of lycopene. 相似文献