全文获取类型
收费全文 | 32687篇 |
免费 | 1090篇 |
国内免费 | 249篇 |
专业分类
化学 | 22707篇 |
晶体学 | 223篇 |
力学 | 772篇 |
数学 | 5422篇 |
物理学 | 4902篇 |
出版年
2022年 | 284篇 |
2021年 | 420篇 |
2020年 | 515篇 |
2019年 | 484篇 |
2018年 | 376篇 |
2017年 | 373篇 |
2016年 | 835篇 |
2015年 | 737篇 |
2014年 | 807篇 |
2013年 | 1725篇 |
2012年 | 1866篇 |
2011年 | 2353篇 |
2010年 | 1141篇 |
2009年 | 1005篇 |
2008年 | 2011篇 |
2007年 | 2021篇 |
2006年 | 1998篇 |
2005年 | 1862篇 |
2004年 | 1588篇 |
2003年 | 1383篇 |
2002年 | 1285篇 |
2001年 | 402篇 |
2000年 | 390篇 |
1999年 | 360篇 |
1998年 | 335篇 |
1997年 | 357篇 |
1996年 | 486篇 |
1995年 | 343篇 |
1994年 | 298篇 |
1993年 | 270篇 |
1992年 | 267篇 |
1991年 | 237篇 |
1990年 | 202篇 |
1989年 | 203篇 |
1988年 | 236篇 |
1987年 | 198篇 |
1986年 | 180篇 |
1985年 | 349篇 |
1984年 | 341篇 |
1983年 | 244篇 |
1982年 | 314篇 |
1981年 | 323篇 |
1980年 | 300篇 |
1979年 | 283篇 |
1978年 | 259篇 |
1977年 | 227篇 |
1976年 | 206篇 |
1975年 | 208篇 |
1974年 | 210篇 |
1973年 | 209篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
David Loffreda 《Surface science》2006,600(10):2103-2112
Adsorption thermodynamics based on density functional theory (DFT) calculations are exposed for the interaction of several multifunctional molecules with Pt and Au(1 1 0)-(1 × 2) surfaces. The Gibbs free adsorption energy explicitly depends on the adsorption internal energy, which is derived from DFT adsorption energy, and the vibrational entropy change during the chemisorption process. Zero-point energy (ZPE) corrections have been systematically applied to the adsorption energy. Moreover the vibrational entropy change has been computed on the basis of DFT harmonic frequencies (gas and adsorbed phases, clean surfaces), which have been extended to all the adsorbate vibrations and the metallic surface phonons. The phase diagrams plotted in realistic conditions of temperature (from 100 to 400 K) and pressure (0.15 atm) show that the ZPE corrected adsorption energy is the main contribution. When strong chemisorption is considered on the Pt surface, the multifunctional molecules are adsorbed on the surface in the considered temperature range. In contrast for weak chemisorption on the Au surface, the thermodynamic results should be held cautiously. The systematic errors of the model (choice of the functional, configurational entropy and vibrational entropy) make difficult the prediction of the adsorption-desorption phase boundaries. 相似文献
112.
We present an algorithm which calculates the monopole number of anSU
2-valued lattice gauge field, together with a lattice Higgs field, on a simplicial lattice of dimension ≧3. The calculation
is gauge invariant. The expected value of the monopole density (for a fixed Higgs field) does not depend on the Higgs field.
Partially supported by NSF grants DMS 8607168 and DMS 8907753
Partially supported by PSC-CUNY and by NSF grant DMS 8805485 相似文献
113.
David Ritz Finkelstein 《International Journal of Theoretical Physics》2006,45(8):1397-1427
In the Darwinian evolution of physical theories, stability (genericity) has survival value. To convert a singular physical theory based on Lie algebras of several levels into a generic quantum theory with the same levels and nearly the same predictions and symmetries in a limited correspondence domain, it suffices to simplify the algebra of each level by a small homotopy (general quantization). This extends and unifies special relativization, general relativization, and canonical quantization. For exercise I general-quantize the scalar meson field in Minkowski space-time. The predictions of the resulting theory are finite, including its zero-point energy.This updates part of a talk given at Glafka 2005, Athens. quant-ph/0601002 相似文献
114.
We analyze new forms of aberrations affecting a time dependent magnetic field lens recently proposed. The lens consist of an axially symmetric ellipsoidal solenoid producing a spatially uniform but time pulsating homogeneous field. The dynamics of electrons emitted by some object and injected into this coil shows that this system is capable of focusing a parallel beam or produce images free of geometrical aberrations. The cardinal elements of this lens change periodically in positions and therefore to obtain a stationary image it is necessary to employ a chopped electron beam. Two forms of aberrations originate from the finite duration of the electron pulse and the energy dispersion of the incoming beam (chromatic aberration). Their image degradation effects are quite similar and result from recording different axially displaced images at some fixed stationary plane. We show how, by adjusting the parameters characterizing the magnetic pulse and introducing small apertures that increase the depth of focus, their effects can be reduced or in some cases eliminated. Other forms of instrumental aberrations characteristic of this time dependent magnetic field lens are briefly discussed. 相似文献
115.
The historical development of Hensel's lemma is briefly discussed (Section 1). Using Newton polygons, a simple proof of a general Hensel's lemma for separable polynomials over Henselian fields is given (Section 3). For polynomials over algebraically closed, valued fields, best possible results on continuity of roots (Section 4) and continuity of factors (Section 6) are demonstrated. Using this and a general Krasner's lemma (Section 7), we give a short proof of a general Hensel's lemma and show that it is, in a certain sense, best possible (Section 8). All valuations here are non-Archimedean and of arbitrary rank. The article is practically self-contained. 相似文献
116.
117.
N. David Mermin 《Pramana》1998,51(5):549-565
I list several strong requirements for what I would consider a sensible interpretation of quantum mechanics and discuss two
simple recent theorems which have important implications for such an interpretation. My talk will not clear everything up;
indeed, you may conclude that it has not cleared anything up. But I hope it will provide a different perspective from which
to view some old and vexing puzzles (or, if you believe nothing needs to be cleared up, some ancient verities.) 相似文献
118.
119.
Nonequilibrium statistical mechanics close to equilibrium is studied using SRB states and a formula [10] for their derivatives
with respect to parameters. We write general expressions for the thermodynamic fluxes (or currents) and the transport coefficients,
generalizing the results of [4, 5]. In this framework we give a general proof of the Onsager reciprocity relations.
Received: 2 December 1996 / Accepted: 13 March 1997 相似文献
120.
In this paper a statistical multiplexer that processes a mixture of real-time and non-real-time traffic is studied under bursts of traffic. Different scheduling algorithms are compared under conditions when one of the classes of traffic has a sudden increase in its arrival rate during a short period of time. The results show a difference in the way the scheduling disciplines studied behave under short overloads of traffic even though the scheduling algorithms had been set up to give similar performance under steady-state arrivals. The lifetime of real-time packets is shown to have a great effect on the way in which the performance of the scheduling algorithms compare.Robert Lackman is an IBM employee in the IBM Resident Study Program. 相似文献