全文获取类型
收费全文 | 10045篇 |
免费 | 235篇 |
国内免费 | 11篇 |
专业分类
化学 | 5857篇 |
晶体学 | 179篇 |
力学 | 212篇 |
数学 | 1600篇 |
物理学 | 2443篇 |
出版年
2022年 | 43篇 |
2021年 | 199篇 |
2020年 | 152篇 |
2019年 | 194篇 |
2018年 | 177篇 |
2017年 | 182篇 |
2016年 | 316篇 |
2015年 | 264篇 |
2014年 | 330篇 |
2013年 | 767篇 |
2012年 | 507篇 |
2011年 | 588篇 |
2010年 | 474篇 |
2009年 | 412篇 |
2008年 | 510篇 |
2007年 | 477篇 |
2006年 | 401篇 |
2005年 | 369篇 |
2004年 | 327篇 |
2003年 | 327篇 |
2002年 | 263篇 |
2001年 | 185篇 |
2000年 | 175篇 |
1999年 | 135篇 |
1998年 | 137篇 |
1997年 | 113篇 |
1996年 | 107篇 |
1995年 | 137篇 |
1994年 | 87篇 |
1993年 | 65篇 |
1992年 | 92篇 |
1991年 | 73篇 |
1990年 | 91篇 |
1989年 | 78篇 |
1988年 | 85篇 |
1987年 | 66篇 |
1986年 | 74篇 |
1985年 | 123篇 |
1984年 | 134篇 |
1983年 | 76篇 |
1982年 | 82篇 |
1981年 | 81篇 |
1980年 | 101篇 |
1979年 | 68篇 |
1978年 | 78篇 |
1977年 | 82篇 |
1976年 | 79篇 |
1975年 | 66篇 |
1974年 | 52篇 |
1973年 | 48篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Regularity and other properties of absolutely continuous invariant measures for the quadratic family
In the current paper we study in more detail some properties of the absolutely continuous invariant measures constructed in the course of the proof of Jakobson's Theorem. In particular, we show that the density of the invariant measure is continuous at Misiurewicz points. From this we deduce that the Lyapunov exponent is also continuous at these points (our considerations apply just to the parameters constructed in the proof of Jakobson's Theorem). Other properties, like the positivity of the Lyapunov exponent, uniqueness of the absolutely continuous invariant measure and exactness of the corresponding dynamical system, are also proved.This paper was written during the author's stay at the IAS while supported by NSF grant DMS-860 1978 相似文献
52.
Janusz Mierczyński Wenxian Shen Xiao-Qiang Zhao 《Journal of Differential Equations》2004,204(2):471-510
The purpose of this paper is to investigate uniform persistence for nonautonomous and random parabolic Kolmogorov systems via the skew-product semiflows approach. It is first shown that the uniform persistence of the skew-product semiflow associated with a nonautonomous (random) parabolic Kolmogorov system implies that of the system. Various sufficient conditions in terms of the so-called unsaturatedness and/or Lyapunov exponents for uniform persistence of the skew-product semiflows are then provided. Among others, it is shown that if the associated skew-product semiflow has a global attractor and its restriction to the boundary of the state space has a Morse decomposition which is unsaturated or whose external Lyapunov exponents are positive, then it is uniformly persistent. More specific conditions are discussed for uniform persistence in n-species, particularly 3-species, random competitive systems. 相似文献
53.
JPC – Journal of Planar Chromatography – Modern TLC - Emodin and twelve phenolic acids (ellagic, gallic, protocatechuic, homoprotocatechuic, caffeic, p-hydroxybenzoic, p-coumaric,... 相似文献
54.
55.
We study solutions of the Cauchy problem for a supercritical semilinear parabolic equation which converge to a singular steady state from below as t→∞. We show that the grow-up rate of such solutions depends on the spatial decay rate of initial data. 相似文献
56.
Joanna Tarasińska 《Applications of Mathematics》2003,48(1):67-72
Two estimates of the regression coefficient in bivariate normal distribution are considered: the usual one based on a sample and a new one making use of additional observations of one of the variables. They are compared with respect to variance. The same is done for two regression lines. The conclusion is that the additional observations are worth using only when the sample is very small. 相似文献
57.
Agnieszka Grzelka Marek Cypryk Peter C. Hupfield 《Journal of organometallic chemistry》2004,689(4):705-713
Kinetics studies of the condensation of model hydroxyl-terminated oligosiloxanes, pentamethyldisiloxane-1-ol (MDH) and heptamethyltrisiloxane-1-ol (MD2H), catalysed by protic complex of tetrakis(pentafluorophenyl)borate in the toluene solution were performed. The dominating reaction was condensation, which was accompanied by disproportionation of oligosiloxanols. Water released in the condensation forms separate dispersed phase, but the phase separation and the presence of water does not affect the rate of the polycondensation. Both processes, condensation and disproportionation, show analogous kinetic laws being first order in silanol and half order in catalyst. They exhibit also similar values of activation parameters. The kinetics are explained by the formation of a reactive protic complex of silanol with borate being in fast preequilibrium with an unreactive complex including two borate molecules and the silanol molecules. The equilibrium lies to the side of the unreactive borate complex. 相似文献
58.
59.
Grzegorz M. Salamończyk 《Tetrahedron letters》2003,44(40):7449-7453
An efficient synthesis of antiviral dendritic prodrug candidates, water-soluble, polyanionic conjugates of 1st and 2nd generation thiophosphate dendrimers with acyclovir, is described. 相似文献
60.
Examples of quasi-exactly solvable hamiltonians in the Bargmann—Fock representation are given. The existence of an invariant subspace is studied as a result of hidden symmetry of the spectral problem. 相似文献