全文获取类型
收费全文 | 9446篇 |
免费 | 337篇 |
国内免费 | 558篇 |
专业分类
化学 | 3284篇 |
晶体学 | 256篇 |
力学 | 102篇 |
综合类 | 61篇 |
数学 | 5185篇 |
物理学 | 1453篇 |
出版年
2023年 | 64篇 |
2022年 | 105篇 |
2021年 | 118篇 |
2020年 | 115篇 |
2019年 | 198篇 |
2018年 | 171篇 |
2017年 | 163篇 |
2016年 | 163篇 |
2015年 | 192篇 |
2014年 | 258篇 |
2013年 | 550篇 |
2012年 | 335篇 |
2011年 | 571篇 |
2010年 | 522篇 |
2009年 | 647篇 |
2008年 | 701篇 |
2007年 | 666篇 |
2006年 | 540篇 |
2005年 | 451篇 |
2004年 | 416篇 |
2003年 | 337篇 |
2002年 | 451篇 |
2001年 | 246篇 |
2000年 | 237篇 |
1999年 | 247篇 |
1998年 | 200篇 |
1997年 | 154篇 |
1996年 | 208篇 |
1995年 | 168篇 |
1994年 | 158篇 |
1993年 | 127篇 |
1992年 | 105篇 |
1991年 | 64篇 |
1990年 | 55篇 |
1989年 | 35篇 |
1988年 | 28篇 |
1987年 | 38篇 |
1986年 | 21篇 |
1985年 | 54篇 |
1984年 | 28篇 |
1983年 | 26篇 |
1982年 | 38篇 |
1981年 | 54篇 |
1980年 | 44篇 |
1978年 | 40篇 |
1977年 | 46篇 |
1976年 | 43篇 |
1975年 | 24篇 |
1974年 | 28篇 |
1973年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
51.
继续作者最近的研究,用所谓的Hankel向量方法建立S[a,b]函数类中带边界插值数据的Nevanlinna-Pick插值问题与[a,b]上的某种带约束条件的Hausdorff矩量问题之间解集之间明确的一一对应关系.通过N[a,b]函数类与S[a,b]函数类之间的联系,从而由BNP(N[a,b])问题的可解性准则和解的参数化描述获得BNP(S[a,b)问题的可解性准则和解的参数化表示. 相似文献
52.
R.J Hand 《Journal of Non》2003,315(3):276-287
Glass may be strengthened by epoxy coatings although the strengthening mechanisms remain unclear. Possible strengthening mechanisms are reviewed and are used to analyse strength data for both a solvent based and a water based coating system. The coatings either fill (solvent based coatings), or partially fill (water based coatings) surface cracks and it is shown that closure stresses arising from the thermal expansion mismatch of the coating within these cracks can account for the observed degrees of strengthening. It is also demonstrated that other suggested mechanisms such as flaw healing cannot fully account for the observed degree of strengthening. 相似文献
53.
F.O. Borges G.H. Cavalcanti A.G. Trigueiros 《Journal of Quantitative Spectroscopy & Radiative Transfer》2003,78(1):119-129
The weighted oscillator strengths (gf) and the lifetimes presented in this work were carried out in a multi configuration Hartree-Fock relativistic (HFR) approach. In this calculation, the electrostatic parameters were optimized by a least-squares procedure, in order to improve the adjustment to experimental energy levels. This method produces gf-values that are in better agreement with intensity observations and lifetime values that are closer to the experimental ones. In this work, we presented all the experimentally known electric dipole S IX and S X spectral lines. 相似文献
54.
We studied the low speed fracture regime (10−4-10−9 m s−1) in different glassy materials (soda-lime glass, glass ceramics) with variable but controlled length scale of heterogeneity. The chosen mechanical system enabled us to work in pure mode I (tensile) and at a fixed load on double cleavage drilled compression specimen. The internal residual stresses of studied samples were carefully relaxed by appropriate thermal treatment. By means of optical and atomic force microscopy techniques fracture surfaces have been examined. We have shown for the first time that the crack front line underwent an out-of-plane oscillating behavior as a result of a reproducible sequence of instabilities. The wavelength of such a phenomenon is in the micrometer range and its amplitude in the nanometer range. These features were observed for different glassy materials providing that a typical length scale characterizing internal heterogeneities was lower than a threshold limit estimated to few nanometers. This effect is the first clear experimental evidence of crack path instabilities in the low speed regime in a uniaxial loading experiment. This phenomenon has been interpreted by referring to the stability criterion for a straight crack propagation as presented by Adda-Bedia et al. [Phys. Rev. Lett. 76 (1996) 1497]. 相似文献
55.
56.
Franc Forstnerič 《Mathematische Annalen》1992,292(1):163-180
57.
58.
59.
This article introduces and analyzes a p-version FEM for variational inequalities resulting from obstacle problems for some quasi-linear elliptic partial differential
operators. We approximate the solution by controlling the obstacle condition in images of the Gauss–Lobatto points. We show
existence and uniqueness for the discrete solution u
p
from the p-version for the obstacle problem. We prove the convergence of u
p
towards the solution with respect to the energy norm, and assuming some additional regularity for the solution we derive
an a priori error estimate. In numerical experiments the p-version turns out to be superior to the h-version concerning the convergence rate and the number of unknowns needed to achieve a certain exactness of the approximation. 相似文献
60.
In this paper, we establish a theorem on the distribution of primes in quadratic progressions on average. 相似文献