全文获取类型
收费全文 | 32120篇 |
免费 | 606篇 |
国内免费 | 190篇 |
专业分类
化学 | 21236篇 |
晶体学 | 234篇 |
力学 | 824篇 |
综合类 | 1篇 |
数学 | 5714篇 |
物理学 | 4907篇 |
出版年
2021年 | 210篇 |
2020年 | 271篇 |
2019年 | 323篇 |
2018年 | 264篇 |
2017年 | 237篇 |
2016年 | 528篇 |
2015年 | 418篇 |
2014年 | 538篇 |
2013年 | 1527篇 |
2012年 | 1369篇 |
2011年 | 1696篇 |
2010年 | 910篇 |
2009年 | 755篇 |
2008年 | 1545篇 |
2007年 | 1624篇 |
2006年 | 1583篇 |
2005年 | 1609篇 |
2004年 | 1403篇 |
2003年 | 1174篇 |
2002年 | 1167篇 |
2001年 | 437篇 |
2000年 | 391篇 |
1999年 | 317篇 |
1998年 | 342篇 |
1997年 | 394篇 |
1996年 | 468篇 |
1995年 | 382篇 |
1994年 | 365篇 |
1993年 | 363篇 |
1992年 | 362篇 |
1991年 | 301篇 |
1990年 | 290篇 |
1989年 | 314篇 |
1988年 | 356篇 |
1987年 | 319篇 |
1986年 | 334篇 |
1985年 | 506篇 |
1984年 | 555篇 |
1983年 | 406篇 |
1982年 | 551篇 |
1981年 | 526篇 |
1980年 | 453篇 |
1979年 | 451篇 |
1978年 | 451篇 |
1977年 | 434篇 |
1976年 | 370篇 |
1975年 | 379篇 |
1974年 | 341篇 |
1973年 | 323篇 |
1972年 | 197篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
Bourget Alain Jakobson Dmitry Min-Oo Maung Toth John A. 《Letters in Mathematical Physics》2003,64(2):105-118
We determine the limiting density of the zeroes of Heine–Stieltjes polynomials (or of any set of points satisfying the conclusion of Heine–Stieltjes Theorem) in the thermodynamic limit and use this to prove a strong law of large numbers for the zeroes. 相似文献
63.
Detailed chemical kinetic mechanisms of complex chemical phenomena may be composed of hundreds of species and thousands of individual elementary reactions. It can be an extremely laborious and error‐prone procedure to compare two of these mechanisms, particularly if they come from different sources. We have created software tools which help to highlight the differences between mechanisms written in a Chemkin format and demonstrate their applicability to five literature mechanisms describing the high temperature oxidation of methane. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36:467–471, 2004 相似文献
64.
Walter D. Neumann Paul Norbury 《Transactions of the American Mathematical Society》2003,355(2):519-538
We show that although the fundamental group of the complement of an algebraic affine plane curve is not easy to compute, it possesses a more accessible quotient, which we call the Orevkov invariant.
65.
We consider the asymptotic dynamics of the Einstein-Maxwell field equations for the class of non-tilted Bianchi cosmologies with a barotropic perfect fluid and a pure homogeneous source-free magnetic field, with emphasis on models of Bianchi type VII0, which have not been previously studied. Using the orthonormal frame formalism and Hubble-normalized variables, we show that, as is the case for the previously studied class A magnetic Bianchi models, the magnetic Bianchi VII0 cosmologies also exhibit an oscillatory approach to the initial singularity. However, in contrast to the other magnetic Bianchi models, we rigorously establish that typical magnetic Bianchi VII0 cosmologies exhibit the phenomena of asymptotic self-similarity breaking and Weyl curvature dominance in the late-time regime. 相似文献
66.
John Swain 《Zeitschrift fur Physik C Particles and Fields》1996,71(1):455-457
The final states for the processb→sy have been extensively discussed in the literature. Similarly-detailed analyses for the caseb→s gluon have not been performed. Generally this process is searched for in 2-body decays such as B0→K+ π ?. We present simple arguments to suggest that most of the time the quark-level process will give rise to final states with rather high multiplicities. Comments are made about the applicability of these results tob→d gluon and hadronicb→u decays. 相似文献
67.
The sessile-drop method is used to measure the surface tension and density of liquid indium and uranium under high vacuum. Measurements are made over the temperature range 156–500°C for In and at the melting point for U. Surface oxides are efficiently removed with a glow discharge system. Drop profiles are captured by photograph and processed using nonlinear regression to yield the surface tension and density. In this regression procedure, normal distances from calculated profiles to data points are minimized. For indium, the density and surface tension measurements yield mp = 7.05 × 103kg/m3, d/dT = −0.776 kg/m3·°C, and γmp = 0.568 N/m, dγ/dT = −9.45 × 10−5 N/m·°C. The results for uranium at the melting point are mp = 17.47 × 103 kg/m3 and γmp = 1.653 N/m. 相似文献
68.
Stochastic resonance is a statistical phenomenon that has been observed in periodically modulated, noise-driven, bistable systems. The characteristic signatures of the effect include an increase in the signal-to-noise of the output as noise is added to the system, and exponentially decreasing peaks in the probability density as a function of residence times in one state. Presented are the results of a numerical simulation where these same signatures were observed by adding achaotic driving term instead of a white noise term. Although the probability distributions of the noise and chaos inputs were significantly different, the stochastic and chaotic resonances were equal within the experimental error. 相似文献
69.
John C. Baez 《Communications in Mathematical Physics》1998,193(1):219-231
Working in the Palatini formalism, we describe a procedure for constructing degenerate solutions of general relativity on
4-manifold M from certain solutions of 2-dimensional $BF$ theory on any framed surface Σ embedded in M. In these solutions the cotetrad field e (and thus the metric) vanishes outside a neighborhood of Σ, while inside this neighborhood the connection A and the field satisfy the equations of 4-dimensional BF theory. Our construction works in any signature and with any value of the cosmological constant. If for some 3-manifold S, at fixed time our solutions typically describe “flux tubes of area”: the 3-metric vanishes outside a collection of thickened
links embedded in S, while inside these thickened links it is nondegenerate only
in the two transverse directions. We comment on the quantization of the theory of solutions of this form and its relation
to the loop representation of quantum gravity.
Received: 21 April 1997 / Accepted: 22 August 1997 相似文献
70.
Recently, with the advent of supercomputers, there has been considerable interest in the use of direct numerical simulation to obtain information about turbulent shear flow at low Reynolds number. This paper presents a pseudospectral technique to solve the full three-dimensional time-dependent Navier-Stokes and advection-diffusion equations without the use of subgrid-scale modelling. The technique has not been previously used for fully developed turbulent channel flow simulation and is based on methods applied in other contexts. The emphasis of this paper is to provide a reasonably detailed account of how the simulation is done rather than to present new calculations of turbulence. The details of an algorithm for turbulent channel flow simulation and the grid and time step sizes needed to integrate through transient behaviour to steady state turbulence have not been published before and are presented here. Results from a Cray-2 simulation of fully developed turbulent flow in a channel with heat transfer are presented along with a critical comparison between experiment and computation. The first- and second-order moments agree well with experimental measurements; the agreement is poor for higher-order moments such as the skewness and flatness near the walls of the channel. Detailed information given about the effects of spatial grid resolution on a computed results is important for estimating the size of the computation required to study various aspects of a turbulent flow. 相似文献