全文获取类型
收费全文 | 18875篇 |
免费 | 679篇 |
国内免费 | 90篇 |
专业分类
化学 | 11231篇 |
晶体学 | 165篇 |
力学 | 475篇 |
综合类 | 1篇 |
数学 | 3677篇 |
物理学 | 4095篇 |
出版年
2023年 | 125篇 |
2022年 | 116篇 |
2021年 | 295篇 |
2020年 | 330篇 |
2019年 | 364篇 |
2018年 | 327篇 |
2017年 | 315篇 |
2016年 | 696篇 |
2015年 | 581篇 |
2014年 | 645篇 |
2013年 | 1194篇 |
2012年 | 1016篇 |
2011年 | 1170篇 |
2010年 | 782篇 |
2009年 | 681篇 |
2008年 | 885篇 |
2007年 | 897篇 |
2006年 | 683篇 |
2005年 | 648篇 |
2004年 | 573篇 |
2003年 | 495篇 |
2002年 | 479篇 |
2001年 | 289篇 |
2000年 | 281篇 |
1999年 | 212篇 |
1998年 | 216篇 |
1997年 | 212篇 |
1996年 | 196篇 |
1995年 | 182篇 |
1994年 | 168篇 |
1993年 | 180篇 |
1992年 | 170篇 |
1991年 | 151篇 |
1990年 | 157篇 |
1989年 | 143篇 |
1988年 | 125篇 |
1987年 | 132篇 |
1986年 | 136篇 |
1985年 | 206篇 |
1984年 | 210篇 |
1983年 | 151篇 |
1982年 | 159篇 |
1981年 | 168篇 |
1980年 | 150篇 |
1979年 | 166篇 |
1978年 | 162篇 |
1977年 | 129篇 |
1976年 | 139篇 |
1975年 | 150篇 |
1974年 | 150篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
71.
72.
73.
The presented one-capacitor pinch driver, designed as a compact coaxial structure (including spark-gap and discharge section) consistent with the capacitor output, generates a current of 200 kA with 700 ns quarter-period, suitable for studying the optimization of Z-pinch radiative characteristics. The driver is described, measurements of its parameters summarized, and relations to our previous and future activities briefly reviewed.This work was supported in part by the Grant Agency of the Czech Republic under contract No. 202/93/1023. 相似文献
74.
V. D. Fedotov N. P. Obuchov R. A. Zadikhanov J. Spěváček J. Straka 《Applied magnetic resonance》1993,4(4):491-511
The combined analysis of1H and13C NMR relaxation data in solid lysozyme and some typical homopolypeptides was carried out by using “model-free” approach. Three types of relaxation transitions (γ’, γ and β) were revealed in the temperature range investigated. The microdynamical parameters of these motions were determined. From the comparison of these parameters with those of selected synthetic polymers it follows that the molecular motions in proteins and synthetic polymers are of the same nature. All these motions show pronounced anisotropic character. In the investigated temperature range no molecular motions corresponding to α-relaxation (liquid-like) transition were revealed. The hydration effects on parameters of the motions in proteins were considered. The most pronounced effect takes place for β-transition. The effect of Brownian rotation of protein molecule in solution on measured correlation function of local motions was also discussed. 相似文献
75.
Jan Sunner 《Journal of the American Society for Mass Spectrometry》1993,4(5):410-418
Liquid secondary ionization mass spectra of solutions of alkali chlorides in glycerol were studied as a function of salt concentration. The experimental abundances of glycerol ions and of Cs+(CsCl) n cluster ions were successfully reproduced by assuming that most of the randomly distributed ions pair up with counterions shortly after impact. Further, it is considered that clustering (or proton transfer) reactions occur mainly between an ion that survives the pairing process and ion pairs (or basic analytes) in the immediate vicinity; however, some mixing undoubtedly occurs in the later stages of the desorption process. At the density of the original matrix, the range of proton transfer is calculated to be 5–15 Å, and that of clustering approximately 25% shorter. These reaction distances are inversely correlated with the internal energy of the ejected ions. In general, liquid secondary ionization mass spectra of alkali chloride solutions can be seen to result from competitive ion-ion recombination reactions in the decaying matrix. Finally, from the abundances of cluster ions containing [glycerol - H]? ions, it is estimated that approximately 1% of the glycerol molecules in the ejected volume are ionized in the collision cascade. 相似文献
76.
Presented by R. Freese. 相似文献
77.
The sulphur K-edge x-ray absorption spectra of SO2 multilayer and of SO2 submonolayer adsorbed on Cu(100) are analysed. It is found that the dominant spectral features are of a molecular origin. The results support earlier findings that the SO2 molecule stands perpendicular to the surface. Use of non-selfconsistent potentials does not lead to a good quantitative agreement between theory and experiment. 相似文献
78.
79.
Michael Demuth Peter Stollmann Günter Stolz Jan van Casteren 《Integral Equations and Operator Theory》1995,23(2):145-153
We give trace norm estimates for products of integral operators and for diffusion semigroups. These are applied to differences of heat semigroups. A natural example of an integral operator with finite trace which is not trace class is given. 相似文献
80.
In this paper we deal with nonlinear second-order boundary value problems with impulses. The impulsive functions depend implicitly on the different considered variables and the boundary value conditions are nonlinear. In both cases functional dependence on the solution is allowed. The existence results follow from the existence of a pair of well-ordered lower and upper solutions. 相似文献