全文获取类型
收费全文 | 12488篇 |
免费 | 1336篇 |
国内免费 | 1807篇 |
专业分类
化学 | 9421篇 |
晶体学 | 182篇 |
力学 | 477篇 |
综合类 | 78篇 |
数学 | 2989篇 |
物理学 | 2484篇 |
出版年
2024年 | 21篇 |
2023年 | 126篇 |
2022年 | 177篇 |
2021年 | 220篇 |
2020年 | 305篇 |
2019年 | 369篇 |
2018年 | 282篇 |
2017年 | 342篇 |
2016年 | 366篇 |
2015年 | 466篇 |
2014年 | 548篇 |
2013年 | 1137篇 |
2012年 | 794篇 |
2011年 | 820篇 |
2010年 | 702篇 |
2009年 | 745篇 |
2008年 | 831篇 |
2007年 | 799篇 |
2006年 | 714篇 |
2005年 | 656篇 |
2004年 | 608篇 |
2003年 | 548篇 |
2002年 | 711篇 |
2001年 | 430篇 |
2000年 | 411篇 |
1999年 | 342篇 |
1998年 | 314篇 |
1997年 | 255篇 |
1996年 | 212篇 |
1995年 | 184篇 |
1994年 | 160篇 |
1993年 | 129篇 |
1992年 | 107篇 |
1991年 | 95篇 |
1990年 | 92篇 |
1989年 | 98篇 |
1988年 | 69篇 |
1987年 | 48篇 |
1986年 | 46篇 |
1985年 | 54篇 |
1984年 | 52篇 |
1983年 | 33篇 |
1982年 | 37篇 |
1981年 | 33篇 |
1980年 | 36篇 |
1979年 | 30篇 |
1978年 | 21篇 |
1977年 | 14篇 |
1976年 | 10篇 |
1973年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
81.
The oxidation behaviour of LnSiAlON (Ln=Y, La) glasses was studied at different temperatures (990-1150 °C) and under different water vapour pressures (360-2690 Pa). These results were also compared with those obtained under O2, N2/H2O or O2/H2O mixtures. When glasses are treated under a N2/H2O mixture, optical and SEM observations show porous scales. Transformations of the reaction rate data and a kinetic model show that there is only one limiting process occurring during oxidation. This rate limiting step is the progress of the chemical reaction at the internal interface. Determination of the pressure law dependence and thermodynamics calculations of water vapour molecules dissociation at the investigated temperatures allow us to suggest that the mechanism of oxidation corresponds to decomposition of water molecules on the oxynitride glass surface. 相似文献
82.
A. Borgschulte R. Gremaud S. de Man R.J. Westerwaal J.H. Rector B. Dam R. Griessen 《Applied Surface Science》2006,253(3):1417-1423
The optical properties, the switching kinetics and the lifetime of hydrogen switchable mirrors based on Mg-Ni alloys are determined with particular regard to the composition of the optically active metal-hydride layer in combination with the thickness of the catalytic capping layer. For this, a high-throughput experiment is introduced. The switching kinetics and the reversibility of switchable mirrors are strongly thickness dependent, though the details hinge on the fine structure of the clustered capping layer. Therefore, the kinetics is correlated with the surface structures of Pd on MgyNi1−y as investigated by scanning tunneling microscopy. The results are explained by the so-called strong metal-support interaction (SMSI) state, characterized by a complete encapsulation of the capping layer clusters by oxidized species originating from the support. The SMSI-effect is less important with increasing Pd-layer thickness, and is suppressed by a good wetting of the Pd-clusters on the optically active film. This explains the critical thickness for the catalyzed hydrogen uptake observed in many switchable mirror systems. Moreover, the degradation of the kinetics during cycling is found to depend on the Pd-layer thickness and on the gas environment. Only films, covered with at least 15 nm Pd, show small degradation caused by the SMSI-effect. The SMSI-effect is partly reversible: after changing the gas environment from hydrogen to oxygen, the oxide on the Pd-clusters can be partly removed. 相似文献
83.
Global Existence and Exponential Stability of Smooth Solutions to a Full Hydrodynamic Model to Semiconductors 总被引:1,自引:0,他引:1
We study a full hydrodynamic semiconductor model in multi-space dimension. The global existence of smooth solutions is established
and the exponential stability of the solutions as is investigated.
Received November 14, 2000; in revised form March 25, 2002 Published online August 5, 2002 相似文献
84.
A posteriori error estimators for the Stokes equations 总被引:5,自引:0,他引:5
Summary We present two a posteriori error estimators for the mini-element discretization of the Stokes equations. One is based on a suitable evaluation of the residual of the finite element solution. The other one is based on the solution of suitable local Stokes problems involving the residual of the finite element solution. Both estimators are globally upper and locally lower bounds for the error of the finite element discretization. Numerical examples show their efficiency both in estimating the error and in controlling an automatic, self-adaptive mesh-refinement process. The methods presented here can easily be generalized to the Navier-Stokes equations and to other discretization schemes.This work was accomplished at the Universität Heidelberg with the support of the Deutsche Forschungsgemeinschaft 相似文献
85.
Annalisa Buffa 《Numerische Mathematik》2002,90(4):617-640
Summary. In this paper, we analyse a stabilisation technique for the so-called three-field formulation for nonoverlapping domain decomposition
methods. The stabilisation is based on boundary bubble functions in each subdomain which are then eliminated by static condensation.
The discretisation grids in the subdomains can be chosen independently as well as the grid for the final interface problem.
We present the analysis of the method and we construct a set of bubble functions which guarantees the optimal rate of convergence.
Received May 12, 1998 / Revised version received November 21, 2000 / Published online June 7, 2001 相似文献
86.
Gabriel Picavet 《Journal of Pure and Applied Algebra》2002,174(2):163-185
We define and study algebraically flat algebras in order to have a better understanding of algebraically projective algebras of finite type (the projective algebras of literature). A close examination of the differential properties of these algebras leads to our main structure theorem. As a corollary, we get that an algebraically projective algebra of finite type over a field is either a polynomial ring or the affine algebra of a complete intersection. 相似文献
87.
Wieczorek-Ciurowa K. Gamrat K. Paryło M. Shirokov Ju. G. 《Journal of Thermal Analysis and Calorimetry》2002,70(1):165-172
The physical mixtures of hydroxocarbonates of Cu and Ni with aluminium were activated using a laboratory planetary mill. The
chemical reactions and alloy formations as the effects of grinding were followed by the phase analysis of solid products based
on the thermogravimetry and X-ray diffractometry. Experimental evidence indicates that the nature of reactions and products
of mechanical activation was dependent on the amount of aluminium and time of grinding.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
88.
89.
Here we prove that every compact differential manifold has a smooth algebraic model defined over Q. In dimension 2 we find an algebraic model (may be singular) defined over Q and birational over Q to the projective plane. 相似文献
90.
Hideaki Ishikawa 《Archiv der Mathematik》2002,79(6):439-448
In this paper we introduce a certain sum by using Dirichlet characters. We investigate the Riesz mean of the sum using the
analytic properties of the MultipleL-function systematically.
Eine überarbeitete Fassung ging am 6. 8. 2001 ein 相似文献