全文获取类型
收费全文 | 39827篇 |
免费 | 2651篇 |
国内免费 | 2034篇 |
专业分类
化学 | 21177篇 |
晶体学 | 173篇 |
力学 | 1576篇 |
综合类 | 639篇 |
数学 | 8817篇 |
物理学 | 12130篇 |
出版年
2023年 | 339篇 |
2022年 | 520篇 |
2021年 | 1615篇 |
2020年 | 873篇 |
2019年 | 858篇 |
2018年 | 670篇 |
2017年 | 775篇 |
2016年 | 986篇 |
2015年 | 1011篇 |
2014年 | 1526篇 |
2013年 | 2453篇 |
2012年 | 1657篇 |
2011年 | 1902篇 |
2010年 | 1780篇 |
2009年 | 2303篇 |
2008年 | 2390篇 |
2007年 | 2500篇 |
2006年 | 1833篇 |
2005年 | 1167篇 |
2004年 | 1076篇 |
2003年 | 1127篇 |
2002年 | 3595篇 |
2001年 | 1277篇 |
2000年 | 838篇 |
1999年 | 709篇 |
1998年 | 706篇 |
1997年 | 472篇 |
1996年 | 492篇 |
1995年 | 433篇 |
1994年 | 454篇 |
1993年 | 486篇 |
1992年 | 469篇 |
1991年 | 311篇 |
1990年 | 260篇 |
1989年 | 217篇 |
1988年 | 253篇 |
1987年 | 200篇 |
1986年 | 222篇 |
1985年 | 331篇 |
1984年 | 252篇 |
1983年 | 156篇 |
1982年 | 298篇 |
1981年 | 475篇 |
1980年 | 429篇 |
1979年 | 472篇 |
1978年 | 374篇 |
1977年 | 283篇 |
1976年 | 238篇 |
1974年 | 77篇 |
1973年 | 153篇 |
排序方式: 共有10000条查询结果,搜索用时 826 毫秒
91.
The content of residual monomers is one of the most important characteristics of polymer dispersions. As a result of the similar physicochemical parameters of ethyl acrylate and methyl methacrylate, it is very difficult to determine the residual monomers in acrylate dispersions obtained by emulsion polymerization of both monomers. Gas chromatography with capillary columns, however, permits separation of these monomers and their quantitative determination in acrylate dispersions. 相似文献
92.
Biswarup Mukhopadhyaya 《Pramana》1998,51(1-2):181-190
The observable consequences of gauge-mediated supersymmetry breaking (GMSB) are reviewed here. Implications of scenarios both
with a neutralino and a slepton as the next lightest supersymmetric particle (NLSP) are surveyed in relation to hadronic ande
+
e
- colliders. We also discuss the phenomenological consequences of the NLSP decaying slowly, giving rise to delayed events in
the detectors.The importance of distinguishing signals of GMSB models from those of the commonly discussed supergravity-type
theories is emphasized. 相似文献
93.
Space time-index plots for probing dynamical nonstationarity 总被引:3,自引:0,他引:3
We propose a simple method to efficiently probe dynamical nonstationarity in observed time series. In a space time-index plot, the density distributions as a function of normalized time-index are V-shaped due to nonstationarity. We show that this method is workable for short data sets and typical examples are illustrated. 相似文献
94.
Ph. Batchelor 《Commentarii Mathematici Helvetici》1998,73(3):337-352
On estime la dérivée des petites valeurs propres du Laplacien sur une famille de surfaces de Riemann. Ces valeurs propres
sont considérées comme des fonctions sur l'espace de Teichmüller, et l'estimation des dérivées peut s'exprimer dans ce contexte.
Received: December 21, 1995 相似文献
95.
An analysis of the different philosophic and scientific visions of Henri Poincaré and Federigo Enriques relative to qualitative analysis provides us with a complex and interesting image of the “essential tension” between “tradition” and “innovation” within the history of science. In accordance with his scientific paradigm, Poincaré viewed qualitative analysis as a means for preserving the nucleus of the classical reductionist program, even though it meant “bending the rules” somewhat. To Enriques's mind, qualitative analysis represented the affirmation of a synthetic, geometrical vision that would supplant the analytical/quantitative conception characteristic of 19th-century mathematics and mathematical physics. Here, we examine the two different answers given at the turn of the century to the question of the relationship between geometry and analysis and between mathematics, on the one hand, and mechanics and physics, on the other.Copyright 1998 Academic Press.Un'analisi delle diverse posizioni filosofiche e scientifiche di Henri Poincaré e Federigo Enriques nei riguardi dell'analisi qualitativa fornisce un'immagine complessa e interessante della “tensione essenziale” tra “tradizione” e “innovazione” nell'ambito della storia della scienza. In linea con il proprio paradigma scientifico, Poincaré vedeva nell'analisi qualitativa un mezzo per preservare il nucleo del programma riduzionista calssico, anche se cio comportava una lieve “distorsione delle regole”. Nella mente di Enriques, l'analisi qualitativa rappresentava l'affermazione di un punto di vista sintetico e geometrico che avrebbe soppiantato la concezione analitico-quantitativa caratteristica della matematica e della fisica matematica del 19° secolo. Il nostro scopo principale è di esaminare due diverse risposte date a cavallo del secolo alla questione dei rapporti tra geometria e analisi e tra matematica da un lato e meccanica e fisica dall'altro.Copyright 1998 Academic Press.AMS subject classification: 01A55 相似文献
96.
97.
L.-H. Tang P. Smilauer D.D. Vvedensky 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(3):409-412
Two types of mechanisms are proposed for mound coarsening during unstable epitaxial growth: stochastic, due to deposition
noise, and deterministic, due to mass currents driven by surface energy differences. Both yield the relation H=(RWL)2 between the typical mound height W, mound size L, and the film thickness H. An analysis of simulations and experimental data shows that the parameter R saturates to a value which discriminates sharply between stochastic () and deterministic () coarsening. We derive a scaling relation between the coarsening exponent 1/z and the mound-height exponent which, for a saturated mound slope, yields .
Received: 11 November 1997 / Revised in final form: 28 November 1997 /
Accepted: 28 November 1997 相似文献
98.
B. Sadashive Gowda G.S.V.L. Narasimham M.V. Krishna Murthy 《International Journal of Heat and Fluid Flow》1997,18(6):613-624
In this paper, a mathematical model for forced-air precooling of spherical food products in bulk is developed. The foods are arranged in horizontal layers stacked one above the other to form a rectangular parallelepiped with a vertical gap in between the product layers. The foods are cooled by chilled air blown along the height of the package. The governing equations for the conduction heat transfer in the foods, simultaneous heat and mass transfer at the food-air interface and in the air stream are solved numerically using finite-difference methods. A comprehensive numerical study is performed by varying the process parameters over a wide range. Typical results showing the variation of moist air properties along the height of the package and the effect of each parameter on the process time are presented. The ranges of parameters for advantageous operation of the precooling system are identified. Correlations are obtained for the process time based on the product center and mass-averaged temperatures in terms of process parameters. 相似文献
99.
Magnetic Properties of the Cobaltates Na6CoS4, Na6CoSe4, and K6CoS4 The alkali metal cobalt chalcogenides Na6CoS4, Na6CoSe4, and K6CoS4 crystallize in the space group P63mc with Z = 4. The structure is characterized by isolated [CoX4]-tetrahedra. The magnetic susceptibilities show Curie-Weiss behaviour. The deviations at low temperatures are caused by antiferromagnetic interactions. The magnetic moments are discussed with regard to ligand-field parameters. 相似文献
100.
Modeling and numerical simulations of the convective flows induced by the vibration of the monocrystal during crystal growth have been performed for two configurations simulating the Cz and FZ methods. This permitted to emphasize the role of different vibrational mechanisms in the formation of the average flows. It is shown that an appropriate combination of these mechanisms can be used to counteract the usual convective flows (buoyancy- and/or thermocapillary-driven) inherent to crystal growth processes from the liquid phase. While vibrational convection is rather complex due to these identified mechanisms, the new modeling used in the present paper opens up very promising perspectives to efficiently control heat and mass transfer during real industrial applications of crystal growth from the liquid phase. 相似文献