全文获取类型
收费全文 | 436966篇 |
免费 | 4880篇 |
国内免费 | 1233篇 |
专业分类
化学 | 234363篇 |
晶体学 | 6496篇 |
力学 | 18796篇 |
综合类 | 13篇 |
数学 | 50040篇 |
物理学 | 133371篇 |
出版年
2021年 | 3802篇 |
2020年 | 4205篇 |
2019年 | 4537篇 |
2018年 | 5885篇 |
2017年 | 5763篇 |
2016年 | 8863篇 |
2015年 | 5596篇 |
2014年 | 8571篇 |
2013年 | 20269篇 |
2012年 | 15720篇 |
2011年 | 19316篇 |
2010年 | 13534篇 |
2009年 | 13399篇 |
2008年 | 17694篇 |
2007年 | 17586篇 |
2006年 | 16291篇 |
2005年 | 14586篇 |
2004年 | 13557篇 |
2003年 | 11913篇 |
2002年 | 11744篇 |
2001年 | 13442篇 |
2000年 | 10095篇 |
1999年 | 7927篇 |
1998年 | 6575篇 |
1997年 | 6316篇 |
1996年 | 6093篇 |
1995年 | 5484篇 |
1994年 | 5401篇 |
1993年 | 5202篇 |
1992年 | 5845篇 |
1991年 | 5935篇 |
1990年 | 5669篇 |
1989年 | 5476篇 |
1988年 | 5496篇 |
1987年 | 5376篇 |
1986年 | 5094篇 |
1985年 | 6565篇 |
1984年 | 6697篇 |
1983年 | 5302篇 |
1982年 | 5389篇 |
1981年 | 5367篇 |
1980年 | 4958篇 |
1979年 | 5353篇 |
1978年 | 5493篇 |
1977年 | 5387篇 |
1976年 | 5331篇 |
1975年 | 4917篇 |
1974年 | 4887篇 |
1973年 | 4880篇 |
1972年 | 3455篇 |
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
81.
We investigate the existence and stability of solutions for higher-order two-point boundary value problems in case the differential
operator is not necessarily positive definite, i.e. with superlinear nonlinearities. We write an abstract realization of the
Dirichlet problem and provide abstract existence and stability results which are further applied to concrete problems. 相似文献
82.
We show how methods for estimating the concentration function of the sum of independent random variables can be used to obtain estimates of the concentration function for the values of additive functions under suitable conditions. Previously obtained estimates of the concentration function are consequences of the estimate obtained in the present paper for functions from of the class under consideration. 相似文献
83.
84.
Butyltins were analyzed in waters from California river and lake marinas and were detected at the part per trillion (ppt) level in most locations. The tributyltin:dibutyltin (TBT/DBT) ratios in the fresh waters were similar to those in their saline counterparts indicating like rates of degradation in the two salinity regimes. 相似文献
85.
86.
An infinite row of periodically spaced, identical rigid circularcylinders is excited by an acoustic line source which is parallelto the generators of the cylinders. A method for calculatingthe scattered field accurately and efficiently is presented.When the cylinders are sufficiently close together, Rayleigh–Blochsurface waves that propagate energy to infinity along the arrayare excited. An expression is derived which enables the amplitudesof these surface waves to be computed without requiring thesolution to the full scattering problem. 相似文献
87.
N. Monnanteuil J.M. Colmont 《Journal of Quantitative Spectroscopy & Radiative Transfer》1983,29(2):131-136
Self broadened widths of seven lines of ozone between 75 and 120 GHz have been measured at room temperature. The variation with temperature of the self-broadening parameter for three of these lines has been studied in the range 245–292°K. 相似文献
88.
The complete set of self-consistent parameters of nominally undoped LiNbO3 crystals of congruent composition that describe the electro-optic, piezoelectric, elasto-optic, elastic, and dielectric response
has been determined by numerically evaluating available measurements. The parameters were determined at room temperature and
consist of the low-frequency clamped dielectric constants εS
ij, elastic stiffness constants at constant electric field CE
ijkl, piezoelectric stress coefficients eijk, elasto-optic constants at constant electric field pE
ijkl, and clamped electro-optic coefficients rS
ijk. It is shown that the complete set is required for calculating the effective electro-optic coefficients and dielectric constants
in photorefractive applications of LiNbO3.
Received: 4 January 2002 / Revised version: 1 February 2002 / Published online: 14 March 2002 相似文献
89.
The statistical characteristics of conditional time before ruin of an insurance company, including the distribution function of conditional time and its moments are examined. 相似文献
90.
Off-the-shell anomalous factors of the two-body Coulomb transition matrices appear in the integral form of the Faddeev second-order
nuclear-electronic amplitude, for proton-hydrogen charge transfer scattering in a typical nlm → n′l′m′ transition. A symmetric-impulse approximation (SIA) is applied to eliminate these factors and an induction method is proposed
to analytically calculate the remaining integrals. The nuclear-electronic amplitude is derived for the general case, and for
totally symmetric collisions, in terms of generalized hypergeometric functions of two variables, F
4, and of one variable, 3
F
2, respectively. The angular distribution of the second-order nuclear-electronic charge transfer amplitude shows the Thomas
mechanism as a peak or a hump for symmetric and asymmetric collisions. There also exists a peak in the forward angular distribution
of the second-order nuclear-electronic amplitude, which partly cancels the kinematic peak in the angular distribution of the
charge transfer differential cross sections. 相似文献