全文获取类型
收费全文 | 60463篇 |
免费 | 8433篇 |
国内免费 | 5912篇 |
专业分类
化学 | 25128篇 |
晶体学 | 1469篇 |
力学 | 10342篇 |
综合类 | 729篇 |
数学 | 15303篇 |
物理学 | 21837篇 |
出版年
2024年 | 97篇 |
2023年 | 552篇 |
2022年 | 957篇 |
2021年 | 1297篇 |
2020年 | 1719篇 |
2019年 | 1569篇 |
2018年 | 1585篇 |
2017年 | 2101篇 |
2016年 | 2522篇 |
2015年 | 2102篇 |
2014年 | 2928篇 |
2013年 | 5045篇 |
2012年 | 3684篇 |
2011年 | 4055篇 |
2010年 | 3452篇 |
2009年 | 3783篇 |
2008年 | 3758篇 |
2007年 | 3726篇 |
2006年 | 3468篇 |
2005年 | 3184篇 |
2004年 | 2872篇 |
2003年 | 2567篇 |
2002年 | 2479篇 |
2001年 | 1929篇 |
2000年 | 1858篇 |
1999年 | 1630篇 |
1998年 | 1484篇 |
1997年 | 1229篇 |
1996年 | 1048篇 |
1995年 | 968篇 |
1994年 | 831篇 |
1993年 | 692篇 |
1992年 | 682篇 |
1991年 | 513篇 |
1990年 | 416篇 |
1989年 | 320篇 |
1988年 | 295篇 |
1987年 | 228篇 |
1986年 | 185篇 |
1985年 | 194篇 |
1984年 | 185篇 |
1983年 | 89篇 |
1982年 | 122篇 |
1981年 | 83篇 |
1980年 | 60篇 |
1979年 | 80篇 |
1978年 | 43篇 |
1977年 | 44篇 |
1976年 | 20篇 |
1973年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
41.
非线性互补问题的一种全局收敛的显式光滑Newton方法 总被引:2,自引:0,他引:2
本针对Po函数非线性互补问题,给出了一种显式光滑Newton方法,该方法将光滑参数μ进行显式迭代而不依赖于Newton方向的搜索过程,并在适当的假设条件下,证明了算法的全局收敛性。 相似文献
42.
电路过渡过程所列方程是微分方程,本文中采用的是方框图模型分析法,即将微分方程的复杂示解分解成最基本的加(减)、乘(除)、积分(微分)、增益等运算,采用VB设计用户界面产进行计算,并给出了一算例。 相似文献
43.
Demixing during film casting of blends of polystyrene, polymethylmethacrylate, and a symmetric diblock copolymer of styrene and methylmethacrylate is discussed. The concentration fluctuations in the homogeneous solutions were calculated in mean field approximation. The structures in the homogeneous and demixed solutions and in the dry films were measured by small-angle x-ray scattering, and the morphologies of the dry films were characterized by transmission electron microscopy. The structure of the dry blends is evidently already pre-formed in solution. 相似文献
44.
45.
It is proved that for any integerk≥ 54 000, there isN
k
>0 depending onk only such that every even integer ≥N
k
is a sum of two odd prime numbers andk powers of 2.
Project partially supported by RGC Research Grant (No.HKU 7122/97P) and Post-Doctoral Fellowship of the University of Hong
Kong. 相似文献
46.
Rafael López 《Annals of Global Analysis and Geometry》1997,15(3):201-210
In this paper we study constant mean curvature compact surfaces with two Jordan curves in parallel planes as boundary and we investigate the point at which the surface inherits the symmetries of its boundary. 相似文献
47.
M. Hanson 《Chromatographia》1994,39(7-8):431-437
Summary Pressure/temperature variation in SFC was shown to influence selectivity towards steroids. Major changes were observed for polar column packings compared to non-polar packings and variation of the amount of modifier showed that this is valid over the whole investigated range. The effect is underlined by a fall in resolution in the low density range (low pressure/high temperature) for polar stationary phases and appears to be significantly larger than for non-polar phases. Major selectivity shifts induced by variation of the physical properties of the mobile phase are considered to be due to the greater effect of polar modifiers on the nature of polar stationary phases than on non-polar phases. 相似文献
48.
49.
Phase Relations and Sodium Ion Conductivity within the Quasi-binary System Na2SiF6/Na2AIF6 . The phase diagram of the Na2SiF6/Na3AlF6 system has been determined by means of x-ray powder diffraction, thermal analysis and conductivity measurements in the sub-solidus region. Na3AlF6 accomodates up to 73 mol.-% Na2SiF6 maintaining the crystal structure type. The sodium ion conductivity increases by about five orders of magnitude upon doping Na3AlF6 with Na2SiF6. 相似文献
50.
J.V.P. de OliveiraA.V. Cardona M.T. VilhenaR.C. Barros 《Journal of Quantitative Spectroscopy & Radiative Transfer》2002,73(1):55-62
We describe a semi-analytical numerical method for coherent isotropic scattering time-dependent radiative transfer problems in slab geometry. This numerical method is based on a combination of two classes of numerical methods: the spectral methods and the Laplace transform (LTSN) methods applied to the radiative transfer equation in the discrete ordinates (SN) formulation. The basic idea is to use the essence of the spectral methods and expand the intensity of radiation in a truncated series of Laguerre polynomials in the time variable and then solve recursively the resulting set of “time-independent” SN problems by using the LTSN method. We show some numerical experiments for a typical model problem. 相似文献