全文获取类型
收费全文 | 170885篇 |
免费 | 2300篇 |
国内免费 | 716篇 |
专业分类
化学 | 92045篇 |
晶体学 | 2462篇 |
力学 | 7605篇 |
综合类 | 7篇 |
数学 | 17727篇 |
物理学 | 54055篇 |
出版年
2021年 | 992篇 |
2020年 | 1114篇 |
2019年 | 1131篇 |
2018年 | 1156篇 |
2017年 | 1168篇 |
2016年 | 2331篇 |
2015年 | 1910篇 |
2014年 | 2489篇 |
2013年 | 7689篇 |
2012年 | 6278篇 |
2011年 | 7948篇 |
2010年 | 4886篇 |
2009年 | 5035篇 |
2008年 | 7311篇 |
2007年 | 7287篇 |
2006年 | 7015篇 |
2005年 | 6540篇 |
2004年 | 5863篇 |
2003年 | 5052篇 |
2002年 | 4960篇 |
2001年 | 6026篇 |
2000年 | 4559篇 |
1999年 | 3479篇 |
1998年 | 2626篇 |
1997年 | 2620篇 |
1996年 | 2568篇 |
1995年 | 2275篇 |
1994年 | 2163篇 |
1993年 | 2027篇 |
1992年 | 2345篇 |
1991年 | 2310篇 |
1990年 | 2022篇 |
1989年 | 2006篇 |
1988年 | 2031篇 |
1987年 | 1960篇 |
1986年 | 1872篇 |
1985年 | 2774篇 |
1984年 | 2753篇 |
1983年 | 2208篇 |
1982年 | 2392篇 |
1981年 | 2272篇 |
1980年 | 2228篇 |
1979年 | 2174篇 |
1978年 | 2243篇 |
1977年 | 2199篇 |
1976年 | 2129篇 |
1975年 | 2119篇 |
1974年 | 2024篇 |
1973年 | 2106篇 |
1972年 | 1202篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
851.
José M. Arrieta Neus Cónsul Anibal Rodríguez-Bernal 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2004,23(2):1-14
We prove the existence of nonconstant stable stationary
solutions of
an evolution problem with a nonlinear reaction acting on the
boundary. These solutions present layers at certain points of the
boundary. We also study the behavior of these solutions as the small
parameter appearing in the equation approaches zero and show some
stability properties of the profiles given by these equilibrium
solutions. 相似文献
852.
A comparison of a theoretical model for quasi-statically and dynamically induced environmental vibration from trains with measurements 总被引:1,自引:0,他引:1
This paper presents comparisons between a theoretical ground vibration model and measured data at three sites. The model, which is briefly outlined here, encompasses both the quasi-static and dynamic mechanisms of excitation. The vertical dynamics of a number of vehicles travelling at a constant speed on an infinite track are coupled to a semi-analytical model for a three-dimensional layered ground. This model is also used to demonstrate the roles of the two components of vibration at different frequencies and for train speeds below and above the lowest ground wave speed. It is found that, in most practical cases, the dynamic component gives rise to the higher level of vibration. 相似文献
853.
C. Bizdadea C.C. Ciobîrc E.M. Cioroianu S.O. Saliu S.C. Sraru 《Annalen der Physik》2003,12(9):543-571
The local and manifestly covariant Lagrangian interactions in four spacetime dimensions that can be added to a “free” model that describes a generic matter theory and an abelian BF theory are constructed by means of deforming the solution to the master equation on behalf of specific cohomological techniques. 相似文献
854.
C. Hanhart 《Progress in Particle and Nuclear Physics》2003,50(2):227-234
A consistent counting scheme is presented that allows to study the reactions NN → NNπ within an effective field theory. Within this scheme the chiral expansion is shown to converge contrary to claims in the literature. 相似文献
855.
The high structural similarity of decarboxylase antibody 21D8 and esterase antibody 48G7 suggests that 21D8 might also possess hydrolytic activity. Kinetic investigations show that 21D8 does promote the selective hydrolysis of methyl 4‐nitrophenyl carbonate and sodium 4‐(acetoxy)benzenesulfonate with catalytic proficiencies (kcat/Km)/kun of ca. 105 M ?1. The ability of 21D8 to accelerate a reaction for which it was not developed suggests that certain antibody scaffolds are intrinsically predisposed toward catalysis, a property that can be enhanced and refined during affinity maturation in response to a transition‐state analog. At the same time, however, the restricted structural diversity of the immune system may ultimately limit the catalytic efficiency that can be achieved. 相似文献
856.
C. Mitrescu G.L. Stephens 《Journal of Quantitative Spectroscopy & Radiative Transfer》2004,86(4):387-394
The present paper shows how the well-known similarity and scaling concepts are properties of the radiative transfer equation and not specifically of the degree of anisotropy of the phase function. It is shown that the key assumption regarding the angular dependence of the radiative field is essential in determining both the value for the parameter used to scale the radiative transfer, as well as the number of streams used in calculating the radiances for various atmospheric problems. Simulations performed on realistic type of cirrus clouds, characterized by strongly anisotropic functions, demonstrates the superior computational advantage for accurately simulating radiances. A new approach for determining the scaling parameter is introduced. 相似文献
857.
Kvon Z. D. Tkachenko V. A. Plotnikov A. E. Sablikov V. A. Renard V. Portal J. C. 《JETP Letters》2004,79(1):36-39
JETP Letters - An experimental study of the two-, three-, and four-terminal resistance of a ballistic wire is carried out. The wire is fabricated on the basis of high-mobility 2D electron gas in an... 相似文献
858.
The oxidations of diethyl sulfide by potassium dichromate, pyridinium dichromate, quinolinium dichromate, imidazolium dichromate, nicotinium dichromate, isonicotinium dichromate, pyridinium fluorochromate, quinolinium fluorochromate, imidazolium fluorochromate, pyridinium chlorochromate, quinolinium chlorochromate, and pyridinium bromochromate follow identical kinetic orders—first‐order each with respect to the chromium(VI) reagents, sulfide and hydrogen ion, and moderately inhibited by manganese(II) ion. The energy of activation varies linearly with the logarithm of frequency factor and so does the enthalpy of activation with the entropy of activation. Also, the activation free energies do not differ significantly. The dichromates and halochromates of heterocyclic bases oxidize diethyl sulfide via a common mechanism. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 35: 1–8, 2003 相似文献
859.