全文获取类型
收费全文 | 47369篇 |
免费 | 1618篇 |
国内免费 | 166篇 |
专业分类
化学 | 25761篇 |
晶体学 | 262篇 |
力学 | 1242篇 |
综合类 | 5篇 |
数学 | 8102篇 |
物理学 | 13781篇 |
出版年
2023年 | 298篇 |
2021年 | 415篇 |
2020年 | 600篇 |
2019年 | 481篇 |
2018年 | 662篇 |
2017年 | 632篇 |
2016年 | 1304篇 |
2015年 | 1029篇 |
2014年 | 1162篇 |
2013年 | 2452篇 |
2012年 | 2237篇 |
2011年 | 2395篇 |
2010年 | 1617篇 |
2009年 | 1384篇 |
2008年 | 2177篇 |
2007年 | 2097篇 |
2006年 | 2020篇 |
2005年 | 1782篇 |
2004年 | 1576篇 |
2003年 | 1237篇 |
2002年 | 1135篇 |
2001年 | 984篇 |
2000年 | 840篇 |
1999年 | 598篇 |
1998年 | 531篇 |
1997年 | 502篇 |
1996年 | 616篇 |
1995年 | 528篇 |
1994年 | 569篇 |
1993年 | 573篇 |
1992年 | 627篇 |
1991年 | 453篇 |
1990年 | 456篇 |
1989年 | 430篇 |
1988年 | 386篇 |
1987年 | 397篇 |
1986年 | 367篇 |
1985年 | 557篇 |
1984年 | 539篇 |
1983年 | 448篇 |
1982年 | 474篇 |
1981年 | 484篇 |
1980年 | 458篇 |
1979年 | 458篇 |
1978年 | 435篇 |
1977年 | 430篇 |
1976年 | 415篇 |
1975年 | 397篇 |
1974年 | 383篇 |
1973年 | 333篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
201.
Michal Johanis Jan Rychtá r 《Proceedings of the American Mathematical Society》2007,135(5):1511-1514
It is shown that every separable Banach space admits an equivalent norm that is uniformly Gâteaux smooth and yet lacks asymptotic normal structure.
202.
We investigate linear parabolic systems with coupled nonsmooth capacities and mixed boundary conditions. We prove generalized resolvent estimates in W?1, p spaces. The method is an appropriate modification of a technique introduced by Agmon to obtain Lp estimates for resolvents of elliptic differential operators in the case of smooth boundary conditions. Moreover, we establish an existence and uniqueness result. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
203.
We study a small quantum system (e.g., a simplified model for an atom or molecule) interacting with two bosonic or fermionic
reservoirs (say, photon or phonon fields). We show that the combined system has a family of stationary states parametrized
by two numbers, T
1 and T
2 (‘reservoir temperatures’). If T
1 ≠ T
2, then these states are non-equilibrium stationary states (NESS). In the latter case we show that they have nonvanishing heat
fluxes and positive entropy production and are dynamically asymptotically stable. The latter means that the evolution with
an initial condition, normal with respect to any state where the reservoirs are in equilibria at temperatures T
1 and T
2, converges to the corresponding NESS. Our results are valid for the temperatures satisfying the bound min (T
1,T
2) > g
2 + α, where g is the coupling constant and 0 < α < 1 is a power related to the infra-red behaviour of the coupling functions.
Submitted: March 20, 2006. Revised: March 19, 2007. Accepted: May 11, 2007.
Marco Merkli: Partly supported by an NSERC PDF, the Institute of Theoretical Physics of ETH Zürich, Switzerland, the Departments
of Mathematics of McGill University and the University of Toronto, Canada.
Matthias Mück: Supported by DAAD under grant HSP III.
Israel Michael Sigal: Supported by NSERC under grant NA7901. 相似文献
204.
Solubility of carbon dioxide in aqueous solutions of sodium chloride: Experimental results and correlation 总被引:2,自引:0,他引:2
The solubility of carbon dioxide in aqueous solutions of sodium chloride was measured in the temperature range from 40 to 160°C, up to 6 mol-kg salt solutions and total pressures up to 10 MPa. Pitzer's(1) equations as well as the Chen and Evans(2) model were used to correlate the new data. Results are reported and compared to literature data and correlations. 相似文献
205.
The behaviour of a chiral nematic mixture with low frequency dielectric relaxtion was studied between two electrodes, with homeotropic anchoring, in the presence of an AC electric field E. The phase diagram in the parameter plane (d/p, E) was determined for this mixture which could be dielectrically negative or positive in different frequency ranges. The determination was carried out by changing the sample thickness d and both the amplitude and frequency of the electric field at a constant cholesteric pitch p. 相似文献
206.
Summary Multiconfigurational second order perturbation theory (CASSCF/CASPT2) has been used to investigate the dependence of computed valence excitation energies and transition moments on the basis sets. Pyrazine has been selected as the test molecule. Atomic normal orbital (ANO) type basis sets are used throughout. Contractions of the structure (4s3p1d/2s) are found to be an optimal compromise between the quality and the size of the calculations and are capable of yielding results virtually identical to more extended basis sets. 相似文献
207.
Lemi Türker 《Journal of mathematical chemistry》1992,9(4):341-349
A novel method, based on the topology of the cardinal vertex, is described to find an upper bound for the largest eigenvalue of a graph. 相似文献
208.
Jürgen Kurths M. Carmen Romano Marco Thiel Grigory V. Osipov Mikhail V. Ivanchenko István Z. Kiss John L. Hudson 《Nonlinear dynamics》2006,44(1-4):135-149
We present two different approaches to detect and quantify phase synchronization in the case of coupled non-phase coherent
oscillators. The first one is based on the general idea of curvature of an arbitrary curve. The second one is based on recurrences
of the trajectory in phase space. We illustrate both methods in the paradigmatic example of the R?ssler system in the funnel
regime. We show that the second method is applicable even in the case of noisy data. Furthermore, we extend the second approach
to the application of chains of coupled systems, which allows us to detect easily clusters of synchronized oscillators. In
order to illustrate the applicability of this approach, we show the results of the algorithm applied to experimental data
from a population of 64 electrochemical oscillators. 相似文献
209.
Marko D. Mihovilovic Bernhard Müller Markus Spina Arjumand I. Durrani Peter Stanetty Georg Dazinger Karl Kirchner 《Monatshefte für Chemie / Chemical Monthly》2006,137(6):785-794
Summary. Recombinant Escherichia coli overexpressing Pseudomonas sp. NCIMB 9872 cyclopentanone monooxygenase (CPMO, EC 1.14.13.16) and Acinetobacter sp. NCIMB 9871 cyclohexanone monooxygenase (CHMO, EC 1.14.13.22) have been utilized in whole-cell Baeyer-Villiger biotransformations of prochiral bicycloketones. A significant difference in substrate acceptance and stereoselectivity was
observed for bicyclo[3.3.0] and bicyclo[4.3.0] substrates. A plausible mechanism of these transformations was established
by means of high level DFT/B3LYP calculations suggesting an essential difference in electronic requirements for a successful
enzymatic conversion, which was similarly encountered in recombinant whole-cell mediated biooxidations. Some of the lactones
produced in the biocatalytic Baeyer-Villiger oxidation represent key intermediates for the synthesis of indole alkaloids. 相似文献
210.