全文获取类型
收费全文 | 19326篇 |
免费 | 1458篇 |
国内免费 | 1448篇 |
专业分类
化学 | 7357篇 |
晶体学 | 166篇 |
力学 | 1304篇 |
综合类 | 265篇 |
数学 | 7410篇 |
物理学 | 5730篇 |
出版年
2023年 | 194篇 |
2022年 | 440篇 |
2021年 | 447篇 |
2020年 | 457篇 |
2019年 | 503篇 |
2018年 | 446篇 |
2017年 | 497篇 |
2016年 | 555篇 |
2015年 | 478篇 |
2014年 | 749篇 |
2013年 | 1355篇 |
2012年 | 774篇 |
2011年 | 880篇 |
2010年 | 777篇 |
2009年 | 1068篇 |
2008年 | 1175篇 |
2007年 | 1211篇 |
2006年 | 1055篇 |
2005年 | 820篇 |
2004年 | 729篇 |
2003年 | 716篇 |
2002年 | 776篇 |
2001年 | 663篇 |
2000年 | 622篇 |
1999年 | 544篇 |
1998年 | 497篇 |
1997年 | 373篇 |
1996年 | 270篇 |
1995年 | 227篇 |
1994年 | 205篇 |
1993年 | 200篇 |
1992年 | 266篇 |
1991年 | 167篇 |
1990年 | 120篇 |
1989年 | 107篇 |
1988年 | 115篇 |
1987年 | 111篇 |
1986年 | 86篇 |
1985年 | 99篇 |
1984年 | 102篇 |
1983年 | 58篇 |
1982年 | 110篇 |
1981年 | 182篇 |
1980年 | 192篇 |
1979年 | 192篇 |
1978年 | 174篇 |
1977年 | 105篇 |
1976年 | 113篇 |
1973年 | 80篇 |
1972年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
We obtain exponential upper bounds for tails of distributions of generalized L-statistics based on a sample from an exponential distribution. We prove the asymptotic normality of generalized L-statistics based on a sample from the uniform distribution on [0,1] and of L-statistics with decomposed kernels (without any restrictions on the sample distribution type). 相似文献
22.
23.
Some new oscillation criteria are established for a second order neutral delay differential equations. These results improve oscillation results of Y.V. Rogo-vchenko for the retarded delay differential equations. The relevance of our theorems is illustrated with two carefully selected examples. 相似文献
24.
John A. Ekaterinaris 《国际流体数值方法杂志》2004,45(11):1187-1207
A high‐order accurate, finite‐difference method for the numerical solution of incompressible flows is presented. This method is based on the artificial compressibility formulation of the incompressible Navier–Stokes equations. Fourth‐ or sixth‐order accurate discretizations of the metric terms and the convective fluxes are obtained using compact, centred schemes. The viscous terms are also discretized using fourth‐order accurate, centred finite differences. Implicit time marching is performed for both steady‐state and time‐accurate numerical solutions. High‐order, spectral‐type, low‐pass, compact filters are used to regularize the numerical solution and remove spurious modes arising from unresolved scales, non‐linearities, and inaccuracies in the application of boundary conditions. The accuracy and efficiency of the proposed method is demonstrated for test problems. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
25.
Twenty-five years ago, we introduced the phenomenon of negative luminescence (NL) into semiconductor physics. This paper provides an overview of work conducted to develop this fundamental concept. Initially, we consider the first-principle approach to radiation interaction with basic matter and the major properties of NL. Then we describe the problems of NL direct measurements in homogeneous materials and structures. Finally, we emphasize the use of NL approach in applications involving devices for infrared (IR) wavelength (3–12 μm) high-temperature (300–400 K) optoelectronics. Our subjects will include NL IR emitting diodes, radiative coolers, IR dynamic scene simulators, light up-conversion devices, and the Stealth effect in IR. 相似文献
26.
Yuh-Shan Ho 《Adsorption》2004,10(2):151-158
The kinetics of four sorption systems, Cu/tree fern, Pb/tree fern, AB9/activated clay and BR18/activated clay have been studied based on the assumption of a pseudo-second order rate law. Pseudo-isotherms using the pseudo-second order kinetic expression constant have been developed to describe the four liquid-solid sorption systems. The experimental results have been analyzed using a pseudo-Langmuir and a pseudo-Redlich-Peterson isotherm. Both isotherms were found to represent the measured sorption data well. According to the evaluation using the pseudo-Langmuir equation, the monolayer sorption capacities were obtained to be 13.9, 46.6, 124 and 105 mg g–1 for copper, lead, AB9 and BR18 respectively. 相似文献
27.
28.
Lahcne Mezrag 《Mathematische Nachrichten》2004,266(1):60-67
In [5], it is proved that a bounded linear operator u, from a Banach space Y into an Lp(S, ν) factors through Lp1 (S, ν) for some p1 > 1, if Y* is of finite cotype; (S, ν) is a probability space for p = 0, and any measure space for 0 < p < 1. In this paper, we generalize this result to uv, where u : Y → Lp(S, ν) and v : X → Y are linear operators such that v* is of finite Ka?in cotype. This result gives also a new proof of Grothendieck's theorem. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
29.
A carousel is a dynamical system that describes the movement of an equilateral linkage in which the midpoint of each rod travels parallel to it. They are closely related to the floating body problem. We prove, using the work of Auerbach, that any figure that floats in equilibrium in every position is drawn by a carousel. Of special interest are such figures with rational perimetral density of the floating chords, which are then drawn by carousels. In particular, we prove that for some perimetral densities the only such figure is the circle, as the problem suggests. 相似文献
30.