全文获取类型
收费全文 | 12394篇 |
免费 | 217篇 |
国内免费 | 53篇 |
专业分类
化学 | 7095篇 |
晶体学 | 97篇 |
力学 | 420篇 |
数学 | 2102篇 |
物理学 | 2950篇 |
出版年
2022年 | 108篇 |
2021年 | 121篇 |
2020年 | 137篇 |
2019年 | 142篇 |
2018年 | 147篇 |
2017年 | 121篇 |
2016年 | 216篇 |
2015年 | 196篇 |
2014年 | 206篇 |
2013年 | 660篇 |
2012年 | 450篇 |
2011年 | 560篇 |
2010年 | 401篇 |
2009年 | 330篇 |
2008年 | 520篇 |
2007年 | 478篇 |
2006年 | 489篇 |
2005年 | 437篇 |
2004年 | 425篇 |
2003年 | 341篇 |
2002年 | 333篇 |
2001年 | 228篇 |
2000年 | 221篇 |
1999年 | 171篇 |
1998年 | 141篇 |
1997年 | 163篇 |
1996年 | 201篇 |
1995年 | 161篇 |
1994年 | 152篇 |
1993年 | 183篇 |
1992年 | 194篇 |
1991年 | 210篇 |
1990年 | 146篇 |
1989年 | 148篇 |
1988年 | 174篇 |
1987年 | 203篇 |
1986年 | 174篇 |
1985年 | 223篇 |
1984年 | 213篇 |
1983年 | 169篇 |
1982年 | 205篇 |
1981年 | 201篇 |
1980年 | 189篇 |
1979年 | 197篇 |
1978年 | 190篇 |
1977年 | 185篇 |
1976年 | 162篇 |
1975年 | 169篇 |
1974年 | 153篇 |
1973年 | 146篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Gert de Cooman Matthias C.M. Troffaes Enrique Miranda 《Journal of Mathematical Analysis and Applications》2008,340(2):982-999
This paper deals with n-monotone functionals, which constitute a generalisation of n-monotone set functions. Using the notion of exactness of a functional, we introduce a new notion of lower and upper integral which subsumes as particular cases most of the approaches to integration in the literature. As a consequence, we can characterise which types of integrals can be used to calculate the natural extension (the lower envelope of all linear extensions) of a positive bounded charge. 相似文献
993.
Using a general approach which provides sequential optimality conditions for a general convex optimization problem, we derive necessary and sufficient optimality conditions for composed convex optimization problems. Further, we give sequential characterizations for a subgradient of the precomposition of a K-increasing lower semicontinuous convex function with a K-convex and K-epi-closed (continuous) function, where K is a nonempty convex cone. We prove that several results from the literature dealing with sequential characterizations of subgradients are obtained as particular cases of our results. We also improve the above mentioned statements. 相似文献
994.
995.
996.
997.
A tractor-trailer problem, with full load, from the class of combined routeing and scheduling problems is described. Distinctive features of the problem are: movements must be carried out within certain time windows; subsets of movements are linked in the sense that they must be executed in a certain order; and different priorities are attached to different movements. A new bidirectional sequential constructive heuristic is developed for the solution of this problem. The method constructs routes and schedules for the available tractor fleet. The algorithm attempts to minimize the total time for all the movements by minimizing the time taken up by unproductive movements (so-called deadhead) and waiting time between movements. Some practical aspects of the implementation of the approach are discussed. 相似文献
998.
Tong Van Duc 《Geometriae Dedicata》1987,23(3):347-353
Résumé On se propose d'étudier l'algèbre de Lie des champs de vecteurs qui laissent invariante la structure presque tangente sur le fibré tangent. On montre que cette algèbre de Lie est égale à son algèbre dérivée et on détermine toutes ses dérivations. On en déduit que cette algèbre de Lie caractérise la structure différentiable de la variété de base du fibré tangent. 相似文献
999.
A rapid, reliable and sensitive method is reported for the detection of residues of diethylstilbestrol (DES) in meat samples. Enzymatic digestion of the muscle tissue followed by ether extract yields a raw extract which, depending on its fat content, can be partitioned in an alkali/chloroform mixture or passed through a Sephadex LH-20 column. To avoid false positive results in the radio-immunoassay, this extract is purified further by high-performance liquid chromatography on an RP-18 column. The detection limit is 0.07 ng g?1. 相似文献
1000.
The thermal reactions of endo- and exo-5-cyanobicyclo-[2.2.2]oct-2-ene and their trans- and cis-6-methyl-substituted derivatives have been investigated in the gas phase between 518 and 630 K. Each product decomposes by two parallel first-order retro-Diels-Alder reactions, a main one with formation of cyclohexa-1,3-diene and a minor one with elimination of ethene. Slight isomerizations are also observed. The kinetic results can be explained in terms of a biradical mechanism. The rate-determining step is shown to depend on the amount of resonance energy in the biradical. Heats of formation and entropies of the bicyclo[2.2.2]oct-2-enes studied are estimated. 相似文献