全文获取类型
收费全文 | 264005篇 |
免费 | 7540篇 |
国内免费 | 3965篇 |
专业分类
化学 | 138950篇 |
晶体学 | 4176篇 |
力学 | 12471篇 |
综合类 | 143篇 |
数学 | 28672篇 |
物理学 | 91098篇 |
出版年
2022年 | 2560篇 |
2021年 | 3273篇 |
2020年 | 3424篇 |
2019年 | 3613篇 |
2018年 | 4272篇 |
2017年 | 4015篇 |
2016年 | 5905篇 |
2015年 | 4133篇 |
2014年 | 6088篇 |
2013年 | 12756篇 |
2012年 | 11201篇 |
2011年 | 12933篇 |
2010年 | 8885篇 |
2009年 | 8691篇 |
2008年 | 11033篇 |
2007年 | 10944篇 |
2006年 | 10359篇 |
2005年 | 9037篇 |
2004年 | 8216篇 |
2003年 | 7178篇 |
2002年 | 6986篇 |
2001年 | 8033篇 |
2000年 | 6135篇 |
1999年 | 5007篇 |
1998年 | 4034篇 |
1997年 | 3991篇 |
1996年 | 3690篇 |
1995年 | 3441篇 |
1994年 | 3160篇 |
1993年 | 2935篇 |
1992年 | 3352篇 |
1991年 | 3277篇 |
1990年 | 3161篇 |
1989年 | 2891篇 |
1988年 | 2922篇 |
1987年 | 2889篇 |
1986年 | 2700篇 |
1985年 | 3418篇 |
1984年 | 3635篇 |
1983年 | 2965篇 |
1982年 | 3141篇 |
1981年 | 3121篇 |
1980年 | 2914篇 |
1979年 | 3072篇 |
1978年 | 3144篇 |
1977年 | 3163篇 |
1976年 | 3221篇 |
1975年 | 2973篇 |
1974年 | 2916篇 |
1973年 | 3078篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
D. N. Zaporozhets 《Journal of Mathematical Sciences》2006,137(1):4525-4530
In this note, we find the distibution of the number of real zeros of a random polynomial. We also derive a formula for the
expected number of complex zeros lying in a given domain of the complex plane. Bibliography: 7 titles.
__________
Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 320, 2004, pp. 69–79. 相似文献
33.
We give a coring version for the duality theorem for actions and coactions of a finitely generated projective Hopf algebra.
We also provide a coring analogue for a theorem of H.-J. Schneider, which generalizes and unifies the duality theorem for
finite Hopf algebras and its refinements.
This paper was written while the first author visited the Mathematics Departments of Syracuse University and California State
University Dominguez Hills. He would like to thank both departments for their hospitality. 相似文献
34.
In the study of the behaviors of barriers in an enclosed field, one should take into account such phenomena as sound energy reflection, absorption, scattering and diffraction. Therefore, the study is much more difficult than that in free field. In this paper, sound barriers are classified into four kinds according to their size, number and shape. Each kind of barriers is modelled by a corresponding method based on a computer program—SOFIS. The program combines the ray-tracing technique and statistical method. The impulse response and some acoustical parameters such as sound pressure level at different positions can be calculated by the program, no matter there are a certain kind of barriers in the field or the field is empty. The ray-tracing program and the algorithms for various barriers are validated by the comparison between measurement and prediction of the reverberation room and the anechoic room of the Northwestern Polytechnic University. 相似文献
35.
A new geometrical method to determine the surface damage threshold for ultrashort pulses is presented. It consists in the formation of a surface damage profile by a movement of the sample across the laser beam focus. A single measurement of the maximum transversal dimension of this damage profile, which depends solely on the laser beam power, is used to calculate the local damage threshold intensity. It is also theoretically shown that the damage in the transverse dimension can be controlled under the diffraction-limited spot. 相似文献
36.
M. Brokate D. Rachinskii 《NoDEA : Nonlinear Differential Equations and Applications》2006,13(4):385-411
The paper is concerned with the study of plasticity models described by differential equations with stop and play operators.
We suggest sufficient conditions for the global stability of a unique periodic solution for the scalar models and for the
vector models with biaxial inputs of a particular form, namely the sum of a uniaxial function and a constant term. For another
class of simple biaxial inputs, we present an example of the existence of unstable periodic solutions.
The paper was written during the research stay of D. Rachinskii at the Technical University Munich supported by the research
fellowship from the Alexander von Humboldt Foundation. His work was partially supported by the Russian Science Support Foundation, Russian Foundation for Basic Research (Grant No. 01-01-00146, 03-01-00258), and the Grants of the President of Russia (Grant No. MD-87.2003.01, NS-1532.2003.1). The support is gratefully acknowledged. 相似文献
37.
38.
A simple scheme is developed for treatment of vertical bed topography in shallow water flows. The effect of the vertical step on flows is modelled with the shallow water equations including local energy loss terms. The bed elevation is denoted with zb‐ for the left and zb+ for the right values at each grid point, hence exactly representing a discontinuity in the bed topography. The surface gradient method (SGM) is generalized to reconstruct water depths at cell interfaces involving a vertical step so that the fluxes at the cell interfaces can accurately be calculated with a Riemann solver. The scheme is verified by predicting a surge crossing a step, a tidal flow over a step and dam‐break flows on wet/dry beds. The results have shown good agreements compared with analytical solutions and available experimental data. The scheme is efficient, robust, and may be used for practical flow calculations. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
39.
D. A. Tikhomirov O. S. Slyadevskaya A. V. Eremeev 《Chemistry of Heterocyclic Compounds》1991,27(9):966-969
A convenient method of synthesis of 2-(methoxycarbonylmethylene)-substituted imidazolidines and imidazolidinium bromides, and also of bicyclic diazo compounds has been developed starting from methyl bromopropiolate and ethylenediamine and its derivatives.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1205–1208, September, 1991. 相似文献
40.
I. L. Davies K. E. Markides M. L. Lee M. W. Raynor K. D. Bartle 《Journal of separation science》1989,12(4):193-207
Although coupled liquid chromatographygas chromatography (LC-GC) was first demonstrated ten years ago, only in the last few years has there been a sudden surge of interest in the technique. Approximately 70% of the total number of LC-GC applications have been published in the last two years (1987–88) alone. This review categorizes LC-GC publications into four main application areas: fossil fuels, foods, environmental samples, biologiical/pharmaceutical samples, and miscellaneous samples. Multidimensional separations carried out using other coupled-column chromatographic techniques (such as supercritical fluid chromatography (SFC) with GC, and on-line trace enrichment-GC) have also been included in this review. 相似文献