全文获取类型
收费全文 | 32320篇 |
免费 | 203篇 |
国内免费 | 283篇 |
专业分类
化学 | 12431篇 |
晶体学 | 316篇 |
力学 | 1483篇 |
综合类 | 13篇 |
数学 | 9705篇 |
物理学 | 8858篇 |
出版年
2022年 | 50篇 |
2021年 | 101篇 |
2020年 | 101篇 |
2019年 | 95篇 |
2018年 | 1277篇 |
2017年 | 1542篇 |
2016年 | 854篇 |
2015年 | 675篇 |
2014年 | 606篇 |
2013年 | 928篇 |
2012年 | 3322篇 |
2011年 | 2510篇 |
2010年 | 1940篇 |
2009年 | 1645篇 |
2008年 | 676篇 |
2007年 | 730篇 |
2006年 | 696篇 |
2005年 | 4501篇 |
2004年 | 3954篇 |
2003年 | 2362篇 |
2002年 | 545篇 |
2001年 | 356篇 |
2000年 | 134篇 |
1999年 | 208篇 |
1998年 | 153篇 |
1997年 | 100篇 |
1996年 | 74篇 |
1995年 | 73篇 |
1994年 | 84篇 |
1992年 | 212篇 |
1991年 | 177篇 |
1990年 | 167篇 |
1989年 | 144篇 |
1988年 | 128篇 |
1987年 | 76篇 |
1986年 | 61篇 |
1985年 | 70篇 |
1984年 | 62篇 |
1983年 | 59篇 |
1982年 | 48篇 |
1979年 | 60篇 |
1978年 | 58篇 |
1977年 | 47篇 |
1976年 | 116篇 |
1975年 | 59篇 |
1974年 | 70篇 |
1973年 | 73篇 |
1972年 | 52篇 |
1969年 | 48篇 |
1966年 | 54篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Eduard Feireisl Antonín Novotný Hana Petzeltov 《Mathematical Methods in the Applied Sciences》2002,25(12):1045-1073
We prove a general compactness result for the solution set of the compressible Navier–Stokes equations with respect to the variation of the underlying spatial domain. Among various corollaries, we then prove a general existence theorem for the system in question with no restrictions on smoothness of the spatial domain. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
3.
Julia K Pruns Jens-Peter Vietzke Manfred Strassner Claudius Rapp Ulrich Hintze Wilfried A K?nig 《Rapid communications in mass spectrometry : RCM》2002,16(3):208-211
A new solvent-free sample preparation method using silver trifluoroacetate (AgTFA) was developed for the analysis of low molecular weight paraffins and microcrystalline waxes by laser desorption/ionization time-of-flight mass spectrometry (LDI-TOFMS). Experiments show that spectral quality can be enhanced by dispersing AgTFA directly in liquid paraffins without the use of additional solvents. This preparation mixture is applied directly to the MALDI probe. Solid waxes could be examined by melting prior to analysis. The method also provides sufficiently reproducible spectra that peak area ratios between mono- and bicyclic alkane peaks indicated variations in the cycloalkane content of paraffin samples. Dehydrogenation of hydrocarbons observed during the desorption/ionization process was studied by analysis of alkane standards. 相似文献
4.
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
5.
This paper solves the problem of the duration of the total eclipseof a satellite of a body, provided that (a) the body is sphericalin shape and the mass distribution inside the body is sphericallysymmetrical; (b) the satellite is a very small object; (c) thesatellite's orbit around a body is circular and the satellitecan pass through the centre of its shadow; (d) a source of lightis the source of the conical body's shadow (umbra) and it doesnot change its apparent position in the sky; (e) there are noperturbations on the satellite's orbit. The solution presentedrepresents the general discussion of the problem based on utilizationof some parts of the theory of contraction mappings. 相似文献
6.
Balázs Szendröi 《Mathematische Zeitschrift》2002,240(2):233-241
This note shows that a certain toric quotient of the quintic Calabi-Yau threefold in provides a counterexample to a recent conjecture of Cox and Katz concerning nef cones of toric hypersurfaces.
Received: 8 February 2001; in final form: 17 September 2001 / Published online: 1 February 2002 相似文献
7.
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
8.
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
9.
We consider the one-dimensional steady-state semiconductor deviceequations modelling a pnpn device. There are two relevant scalingsof the equations corresponding to small and large applied voltages.In both scalings, the semiconductor equations can be consideredas singularly perturbed. It turns out that the small-voltagescaling breaks down for current values between two saturationcurrents. In that interval, the large-voltage scaling has tobe employed. For both scalings, we derive the first-order termsof an asymptotic expansion and show that the reduced problemhas a solution. An example verifies that the current-voltagecurves obtained have the expected qualitative structure. 相似文献
10.
K. Morigaki K. Takeda H. Hikita C. Ogihara P. Roca i Cabarrocas 《Journal of Non》2008,354(19-25):2131-2134
Our model for light-induced defect creation in hydrogenated amorphous silicon is applied to its kinetics, i.e., the growing curve of light-induced dangling bond density as a function of illumination time, which is fitted to a stretched exponential function. Two parameters β and τ involved in the function are estimated as functions of saturated dangling bond density in terms of our model. These are compared with two experimental results, i.e., our results obtained from ESR measurements and Shimakawa et al.’s results obtained from photoconductivity measurements. The saturated dangling bond density is also measured as a function of the generation rate of free carriers. The experimental results are compared with calculated results and discussed. 相似文献