全文获取类型
收费全文 | 16482篇 |
免费 | 324篇 |
国内免费 | 84篇 |
专业分类
化学 | 9372篇 |
晶体学 | 126篇 |
力学 | 566篇 |
数学 | 2287篇 |
物理学 | 4539篇 |
出版年
2022年 | 91篇 |
2021年 | 123篇 |
2020年 | 183篇 |
2019年 | 127篇 |
2018年 | 135篇 |
2017年 | 107篇 |
2016年 | 228篇 |
2015年 | 238篇 |
2014年 | 282篇 |
2013年 | 595篇 |
2012年 | 634篇 |
2011年 | 799篇 |
2010年 | 466篇 |
2009年 | 408篇 |
2008年 | 714篇 |
2007年 | 754篇 |
2006年 | 752篇 |
2005年 | 774篇 |
2004年 | 660篇 |
2003年 | 515篇 |
2002年 | 470篇 |
2001年 | 462篇 |
2000年 | 424篇 |
1999年 | 259篇 |
1998年 | 215篇 |
1997年 | 214篇 |
1996年 | 282篇 |
1995年 | 255篇 |
1994年 | 240篇 |
1993年 | 283篇 |
1992年 | 269篇 |
1991年 | 249篇 |
1990年 | 197篇 |
1989年 | 205篇 |
1988年 | 226篇 |
1987年 | 207篇 |
1986年 | 168篇 |
1985年 | 227篇 |
1984年 | 214篇 |
1983年 | 169篇 |
1982年 | 215篇 |
1981年 | 183篇 |
1980年 | 181篇 |
1979年 | 183篇 |
1978年 | 185篇 |
1977年 | 143篇 |
1976年 | 165篇 |
1975年 | 129篇 |
1974年 | 141篇 |
1973年 | 112篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
101.
Nynke A. M. Verhaegh Jeroen S. van Duijneveldt Jan K. G. Dhont Henk N. W. Lekkerkerker 《Physica A》1996,230(3-4):409-436
Mixtures of colloidal silica spheres and polydimethylsiloxane in cyclohexane with a colloid-polymer size ratio of about one were found to phase separate into two fluid phases, one which is colloid-rich and one which is colloid-poor. In this work the phase separation kinetics of this fluid-fluid phase separation is studied for different compositions of the colloid-polymer mixtures, and at several degrees of supersaturation, with small angle light scattering and with light microscopy. The small angle light scattering curve exhibits a peak that grows in intensity and that shifts to smaller wave vector with time. The characteristic length scale that is obtained from the scattering peak is of the order of a few μm, in agreement with observations by light microscopy. The domain size increases with time as
, which might be an indication of coarsening by diffusion and coalescence, like in the case of binary liquid mixtures and polymer blends. For sufficiently low degrees of supersaturation the angular scattering intensity curves satisfy dynamical scaling behavior. 相似文献
102.
A modified expansion-shock tube for nucleation and condensation studies in a supersaturated vapour is described. An analysis is made of the gas-dynamical properties of the new tube configuration and numerical simulations with the Random Choice Method are compared with experiments. It is shown that with the modified configuration one single nucleation pulse can be realized. 相似文献
103.
104.
Rüdiger Schultz Leen Stougie Maarten H. van der Vlerk 《Mathematical Programming》1998,83(1-3):229-252
In this paper we present a framework for solving stochastic programs with complete integer recourse and discretely distributed right-hand side vector, using Gröbner basis methods from computational algebra to solve the numerous second-stage integer programs. Using structural properties of the expected integer recourse function, we prove that under mild conditions an optimal solution is contained in a finite set. Furthermore, we present a basic scheme to enumerate this set and suggest improvements to reduce the number of function evaluations needed. 相似文献
105.
This paper concerns methods by which a trusted authority can distribute keys and/or broadcast a message over a network, so that each member of a privileged subset of users can compute a specified key or decrypt the broadcast message. Moreover, this is done in such a way that no coalition is able to recover any information on a key or broadcast message they are not supposed to know. The problems are studied using the tools of information theory, so the security provided is unconditional (i.e., not based on any computational assumption).In a recent paper st95a, Stinson described a method of constructing key predistribution schemes by combining Mitchell-Piper key distribution patterns with resilient functions; and also presented a construction method for broadcast encryption schemes that combines Fiat-Naor key predistribution schemes with ideal secret sharing schemes. In this paper, we further pursue these two themes, providing several nice applications of these techniques by using combinatorial structures such as orthogonal arrays, perpendicular arrays, Steiner systems and universal hash families. 相似文献
106.
Hans van den Berg Michel Mandjes Rudesindo Núñez-Queija 《Operations Research Letters》2007,35(3):297-307
We study a processor-sharing model in which users choose between a high- and a low-priority service, based on their utility functions and prices charged by the service provider. The latter aims at revenue maximization. The model is motivated by file transmissions in data networks with distributed congestion control. 相似文献
107.
108.
E. Maria Claesson Nilesh C. Mehendale Robertus J.M. Klein Gebbink Gerard van Koten Albert P. Philipse 《Journal of magnetism and magnetic materials》2007
Monodisperse magnetizable colloidal silica particles in a stable dispersion have been functionalized with a homogeneous catalyst: a PCP–pincer Pd-complex. In a proof-of-principle experiment we demonstrate the catalytic activity of the colloids in a C–C bond formation reaction. Advantages of the magnetic silica carriers are the large surface-to-volume ratio and the easy recovery by magnetic separation. After magnetic separation, the catalyst-loaded particles are readily redispersed for further use. 相似文献
109.
Long-Mei Zeng Xiong Fu Jing-Yu Su Florecita De Guzman J. Francis Schmitz M. Bilayet Hossain Dick van Der Helm 《中国化学》1991,9(2):136-143
Three pyrrololactam alkaloids have been isolated from the marine sponge Phacellia fusca Schmidt collected from the South China Sea, and their structures were determined as 1–3 , on the grounds of spectral data. This is the first report of these compounds from this sponge. The structure of 1 was confirmed by X-ray analysis. 相似文献
110.
Martin van Gemmeren 《Transactions of the American Mathematical Society》1996,348(6):2413-2426
In the first part we prove an extension of the Chern-Lashof inequality for noncompact immersed manifolds with finitely many ends. For this we give a lower bound of the total absolute curvature in terms of topological invariants of the manifold. In the second part we discuss tightness properties for such immersions. Finally, we give an upper bound for the substantial codimension.