全文获取类型
收费全文 | 64003篇 |
免费 | 1488篇 |
国内免费 | 313篇 |
专业分类
化学 | 34715篇 |
晶体学 | 546篇 |
力学 | 2023篇 |
综合类 | 12篇 |
数学 | 13965篇 |
物理学 | 14543篇 |
出版年
2023年 | 288篇 |
2022年 | 242篇 |
2021年 | 450篇 |
2020年 | 604篇 |
2019年 | 562篇 |
2018年 | 1907篇 |
2017年 | 2072篇 |
2016年 | 2036篇 |
2015年 | 1632篇 |
2014年 | 1572篇 |
2013年 | 2930篇 |
2012年 | 5445篇 |
2011年 | 4942篇 |
2010年 | 3257篇 |
2009年 | 2765篇 |
2008年 | 2804篇 |
2007年 | 2825篇 |
2006年 | 2575篇 |
2005年 | 6081篇 |
2004年 | 5287篇 |
2003年 | 3340篇 |
2002年 | 1479篇 |
2001年 | 1033篇 |
2000年 | 762篇 |
1999年 | 652篇 |
1998年 | 481篇 |
1997年 | 352篇 |
1996年 | 454篇 |
1995年 | 303篇 |
1994年 | 317篇 |
1993年 | 334篇 |
1992年 | 452篇 |
1991年 | 361篇 |
1990年 | 324篇 |
1989年 | 293篇 |
1988年 | 266篇 |
1987年 | 225篇 |
1986年 | 210篇 |
1985年 | 257篇 |
1984年 | 221篇 |
1983年 | 184篇 |
1982年 | 165篇 |
1981年 | 171篇 |
1979年 | 168篇 |
1978年 | 145篇 |
1977年 | 124篇 |
1976年 | 193篇 |
1975年 | 138篇 |
1974年 | 124篇 |
1973年 | 161篇 |
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
41.
The versatile behavior of a trihydrazidophosphoradamantane allowing the synthesis of a variety of neutral, mono- or di-cationic water-soluble molecules of potential interest for biphasic catalysis is reported. 相似文献
42.
In this paper we construct an example of a word metric on an infinite cyclic subgroup. This example shows that subexponential
distortion does not obstruct non-trivial growth of connected radii. This answers a question of Gromov [6]. The constructed
metric has other pathological properies. Specifically, its asymptotic cone depends on the choice of ultrafilter and scaling
sequence.
The work has been partially supported by the Swiss National Science Foundation. 相似文献
43.
44.
We build a metric space which is homeomorphic to a Cantor set but cannot be realized as the attractor of an iterated function system. We give also an example of a Cantor set K in R3 such that every homeomorphism f of R3 which preserves K coincides with the identity on K. 相似文献
45.
Lubomír Kubáček 《Applications of Mathematics》2006,51(6):565-582
Some remarks to problems of point and interval estimation, testing and problems of outliers are presented in the case of multivariate
regression model.
This work was supported by the Council of Czech Government J14/98:153100011. 相似文献
46.
Milan Medved? 《Journal of Mathematical Analysis and Applications》2002,267(2):643-650
A criterion for the nonexplosion of solutions to semilinear evolution equations on Banach spaces is proved. The result is obtained by applying a modification of the Bihari type inequality to the case of a weakly singular nonlinear integral inequality. 相似文献
47.
Ricardo Celorrio Vı́ctor Domínguez Francisco-Javier Sayas 《Comptes Rendus Mathematique》2002,334(10):923-926
In this work we study the solution of Laplace's equation in a domain with holes by an iteration consisting of splitting the problem in an exterior one, around the holes, plus an interior problem in the unholed domain. We show the existence of a decomposition of the solution when the exterior problem is represented by means of a single-layer protential. Also, for the three-dimensional case and with some adjustments for the two-dimensional case, we prove convergence of the method by writing the iteration as a Jacobi iteration for an operator equation and studying the spectrum of the iteration operator. To cite this article: R. Celorrio et al., C. R. Acad. Sci. Paris, Ser. I 334 (2002) 923–926. 相似文献
48.
Capillary Electrophoresis Chiral Separation for Enantiomeric Purity Determination of a Basic Drug in Pharmaceutical Formulations 总被引:1,自引:0,他引:1
Capillary electrophoresis using a running buffer composed of β-cyclodextrin as the chiral selector and ethanolamine mesylate at pH 9.6 is being used to monitor the stereochemical stability of a hydrophobic drug, containing two chiral centers, in two different formulated self-emulsifying drug delivery system (SEDDS) products. The separation takes place in less than 25 min. Strategies for enhancing the method reproducibility and detection sensitivity in the lower potency formulation are presented. The results demonstrating the specificity, assay precision, recovery, linearity and range achieved during the method validation experiments are presented in this paper.Presented at: CE in the Biotechnology and Pharmaceutical Industries: 7th Symposium on the Practical Applications for the Analysis of Proteins, Nucleotides and Small Molecules, Montreal, Canada, August 12–16, 2005. 相似文献
49.
50.
A simple model consisting of two electronic levels and one vibrational mode (phonon) was theoretically studied. The electronic-vibrational interaction was linear in the vibrational displacement. The vibrational mode was taken in the harmonic approximation and was attached to the thermal bath formed by the ambient environment. The kinetic constants of the vibrational dissipation were of the second order in the vibrational-bath coupling and were taken in the Markovian limit. Although, depending on the parameters of the model, different curves of the non-radiative vibration-induced excited state decay were obtained, in general, three time intervals, corresponding to different physical behaviour, were found. In the short-time interval, small oscillations superimposed on the excited state decay were observed. They were determined by the vibrational frequency and influenced by electronic-vibrational coupling. In the middle-time interval, almost quasi-exponential decay was detected; its rate constant increased with stronger electronic-vibrational interaction and speed of vibrational relaxation. In the long-time interval, the decay was very slow and, under special conditions, even an asymptotic non-zero excited state population was observed. Its value increased with the strength of the off-diagonal electron-vibrational coupling. Links of the parameters of the model with quantum chemical terms were estimated. 相似文献