全文获取类型
收费全文 | 30013篇 |
免费 | 1017篇 |
国内免费 | 658篇 |
专业分类
化学 | 12815篇 |
晶体学 | 273篇 |
力学 | 736篇 |
综合类 | 59篇 |
数学 | 9527篇 |
物理学 | 8278篇 |
出版年
2023年 | 156篇 |
2022年 | 268篇 |
2021年 | 219篇 |
2020年 | 282篇 |
2019年 | 611篇 |
2018年 | 395篇 |
2017年 | 415篇 |
2016年 | 333篇 |
2015年 | 332篇 |
2014年 | 353篇 |
2013年 | 1218篇 |
2012年 | 772篇 |
2011年 | 1279篇 |
2010年 | 838篇 |
2009年 | 1183篇 |
2008年 | 1233篇 |
2007年 | 1244篇 |
2006年 | 1336篇 |
2005年 | 1213篇 |
2004年 | 1390篇 |
2003年 | 1476篇 |
2002年 | 1925篇 |
2001年 | 1891篇 |
2000年 | 1770篇 |
1999年 | 1940篇 |
1998年 | 1665篇 |
1997年 | 1063篇 |
1996年 | 591篇 |
1995年 | 353篇 |
1994年 | 286篇 |
1993年 | 164篇 |
1992年 | 176篇 |
1991年 | 156篇 |
1990年 | 250篇 |
1989年 | 216篇 |
1988年 | 187篇 |
1987年 | 149篇 |
1986年 | 182篇 |
1985年 | 238篇 |
1984年 | 243篇 |
1983年 | 124篇 |
1982年 | 214篇 |
1981年 | 297篇 |
1980年 | 269篇 |
1979年 | 166篇 |
1978年 | 196篇 |
1977年 | 103篇 |
1976年 | 71篇 |
1975年 | 80篇 |
1974年 | 74篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
We prove the existence of solutions to nonlinear free boundary problem with singularities at given points. 相似文献
32.
C. Sparber J. A. Carrillo J. Dolbeault P. A. Markowich 《Monatshefte für Mathematik》2004,141(3):237-257
We analyze the long-time behavior of transport equations for a class of dissipative quantum systems with Fokker-planck type diffusion operator, subject to confining potentials of harmonic oscillator type. We establish the existence and uniqueness of a non-equilibrium steady state for the corresponding dynamics. Further, using a (classical) convex Sobolev inequality, we prove an optimal exponential rate of decay towards this state and additionally give precise dispersion estimates in those cases, where no stationary state exists. 相似文献
33.
Walter Benz 《Monatshefte für Mathematik》2004,141(1):1-10
The lines of euclidean and hyperbolic geometries are characterized as metric lines in the sense of Blumenthal–Menger, and the lines of spherical and elliptic geometry as periodic ones. In euclidean geometries there do not exist periodic lines. 相似文献
34.
We will prove a result concerning the inclusion of non-trivial invariant ideals inside non-trivial ideals of a twisted crossed
product. We will also give results concerning the primeness and simplicity of crossed products of twisted actions of locally
compact groups on -algebras.
Received: 25 January 2002; in final form: 22 May 2002/Published online: 2 December 2002
This work is partially supported by Hong Kong RGC Direct Grant. 相似文献
35.
The form of the probability density derived from the evolution in time of a previously truncated frequency distribution of animal Liveweights is of interest in animal husbandry. Truncated frequency distributions arise when the heavier animals are sold for slaughter and the lighter animals retained. The demands of modern quality assurance schemes require that, given information on animal growth, the farmer is able to estimate the number of animals that would meet the specifications at some time in the future after truncation. Assuming that animal growth can be described by a linear stochastic differential equation, we derive an explicit expression for the probability density of animal Liveweights at any time after the truncation of an initial Gaussian density. It is shown that this probability density converges rapidly to a Gaussian density, so that after about 20 days of typical growth rates for lambs, the resulting density is practically indistinguishable from Gaussian. 相似文献
36.
报道了一种用国产激光二极管泵浦的1064nm单频NdYVO4红外激光器的设计.利用布氏片和石英晶体组合构成的双折射滤光片技术,在泵浦功率为800mW时,实现了功率为360mW的1064nm红外单频输出.测量结果表明,偏振比超过了10001,功率稳定性优于0.5%,振幅噪声小于0.1%. 相似文献
37.
The content of residual monomers is one of the most important characteristics of polymer dispersions. As a result of the similar physicochemical parameters of ethyl acrylate and methyl methacrylate, it is very difficult to determine the residual monomers in acrylate dispersions obtained by emulsion polymerization of both monomers. Gas chromatography with capillary columns, however, permits separation of these monomers and their quantitative determination in acrylate dispersions. 相似文献
38.
I. Peshko G. Galich M. Lopiychuk A. Khizhnyak V. Nakvasuk 《Optics & Laser Technology》1997,29(4):211-215
A laser system containing four CW Nd:YAG double-rod lasers, transforming optics and a fibre with input-output optics has been designed and investigated. It is shown that reduction of the beam parameter product of the non-Gaussian beams in the image space of the lens has made it possible to collect the emission of four lasers to the same fibre. Independent laser operation has provided the output power control in the range of 10–900 W with a stable light spot size on the input end of the fibre. 相似文献
39.
40.
We present a variational treatment for the E × e pseudo Jahn-Teller system. Through canonical transformation the electron and phonon states are decoupled. An analytical form is obtained for the ground state energy by scaling transformation. Including both the dynamical displacement of phonon modes and the softening of phonon frequency, this approach yields fairly accurate results for the ground state energy. The energy splitting and Ham's reduction factor are calculated, which also generates fairly good results compared with other perturbation results. We argue that our variational wave function is valid for the weak and intermediate coupling range. 相似文献