全文获取类型
收费全文 | 73081篇 |
免费 | 6609篇 |
国内免费 | 4861篇 |
专业分类
化学 | 26147篇 |
晶体学 | 210篇 |
力学 | 5246篇 |
综合类 | 1346篇 |
数学 | 32184篇 |
物理学 | 19418篇 |
出版年
2024年 | 119篇 |
2023年 | 728篇 |
2022年 | 1391篇 |
2021年 | 2138篇 |
2020年 | 1617篇 |
2019年 | 1707篇 |
2018年 | 1503篇 |
2017年 | 1811篇 |
2016年 | 2058篇 |
2015年 | 1879篇 |
2014年 | 2969篇 |
2013年 | 4865篇 |
2012年 | 3206篇 |
2011年 | 3796篇 |
2010年 | 3409篇 |
2009年 | 4273篇 |
2008年 | 4632篇 |
2007年 | 4820篇 |
2006年 | 3899篇 |
2005年 | 2919篇 |
2004年 | 2704篇 |
2003年 | 2687篇 |
2002年 | 5044篇 |
2001年 | 2429篇 |
2000年 | 1890篇 |
1999年 | 1637篇 |
1998年 | 1555篇 |
1997年 | 1256篇 |
1996年 | 1166篇 |
1995年 | 1035篇 |
1994年 | 855篇 |
1993年 | 859篇 |
1992年 | 788篇 |
1991年 | 653篇 |
1990年 | 505篇 |
1989年 | 378篇 |
1988年 | 424篇 |
1987年 | 313篇 |
1986年 | 321篇 |
1985年 | 446篇 |
1984年 | 343篇 |
1983年 | 216篇 |
1982年 | 362篇 |
1981年 | 535篇 |
1980年 | 477篇 |
1979年 | 517篇 |
1978年 | 402篇 |
1977年 | 311篇 |
1976年 | 254篇 |
1973年 | 167篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
271.
S. Albeverio S. N. Lakaev J. I. Abdullaev 《Functional Analysis and Its Applications》2002,36(3):212-216
A Hamiltonian describing four bosons that move on a lattice and interact by means of pair zero-range attractive potentials is considered. A stronger version of the Hunziker–Van Vinter–Zhislin theorem on the essential spectrum is established. It is proved that the set of eigenvalues lying to the left of the essential spectrum is finite for any interaction energy of two bosons and is empty if this energy is sufficiently small. 相似文献
272.
一类经典”秘书问题”的推广 总被引:2,自引:0,他引:2
”秘书问题”在最优停时理论的发展中曾起过重要作用 ,实际中的一类问题与”秘书问题”有类似之处 ,但比”秘书问题”更复杂 .本文将经典”秘书问题”进行推广 ,建立了一类比经典”秘书问题”更有实际意义的模型 ,并给出了该类模型的解 . 相似文献
273.
274.
横向放大率法确定复合光学系统的基点 总被引:2,自引:0,他引:2
介绍了应用测量横向放大率确定两薄透镜组成的复合光学系统基点的方法。由于采用线阵光电耦合器件(CCD)测量物经光学系统成像的横向放大率,提高了测量精度。 相似文献
275.
R. Gerbaldo G. Ghigo G. Giunchi L. Gozzelino F. Laviano E. Mezzetti 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(3):297-300
We present results from an extended magneto-optical (MO) analysis of two samples cut from high-density pellets of MgB2. The first sample was studied in order to show that no matter how large the sample is and despite the bulk granularity, the
material enters into a critical state in a crystal-like fashion. The second sample was chosen for the quantitative analysis.
A numerical approach based on an inverted 2D Biot-Savart model was used to calculate the current paths across the homogeneous
polycrystalline bulk, as well as in the vicinity and across some morphological defects. Local current densities in the homogeneous
part were estimated as a function of the applied magnetic field at different temperatures, in three regimes: below full penetration,
at full penetration and above full penetration, respectively. A hypothesis of interpretation of the apparent absence of magnetic
granularity inside the polycrystalline microstructure is presented. It is related to a critical state likely reached by a
network of strongly coupled Josephson junctions.
Received 31 May 2001 and Received in final form 5 December 2001 相似文献
276.
W. Kockelmann M. Hofmann O. Moze S.J. Kennedy K.H.J. Buschow 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(1):25-32
The element distributions and the magnetic ordering behaviour of compounds RNi10Si2 (R
=
Tb, Dy, Ho, Er, Tm) have been studied by neutron powder diffraction down to temperatures of 1.6 K. The compounds crystallize
in an ordered variant of the ThMn12 structure type in the tetragonal space group P4/nmm. An ordered 1:1 distribution of Ni and Si on sites 4d and 4e, respectively,
corresponds to a modulation vector [0, 0, 1] with respect to the space group I4/mmm of the ThMn12 structure. TbNi10Si2 orders antiferromagnetically below T
N
= 4.5 K with a magnetic propagation vector of [0, 0, 1/2]. The magnetic Tb moments, 8.97(2) /Tb atom at 1.6 K, are aligned along the c-axis. The Ni sites in TbNi10Si2 do not carry any ordered magnetic moments. The compounds with R
=
Dy, Ho, Er, and Tm are paramagnetic down to 1.6 K and 3.0 K, respectively.
Received 10 July 2002 / Received in final form 12 September 2002 Published online 29 October 2002 相似文献
277.
A simple model has been developed to describe the Zeeman patterns of far-infrared laser magnetic resonance spectra of the monobromomethyl radical CH2Br observed at 447.3 and 671.1μm. A satisfactory agreement between the experimental spectra of the radical and their simulation with this simple model has been achieved. This approach can be used to gain further information about the structure and the spectrum of this interesting radical. 相似文献
278.
A globally convergent Newton method for solving strongly monotone variational inequalities 总被引:14,自引:0,他引:14
Variational inequality problems have been used to formulate and study equilibrium problems, which arise in many fields including economics, operations research and regional sciences. For solving variational inequality problems, various iterative methods such as projection methods and the nonlinear Jacobi method have been developed. These methods are convergent to a solution under certain conditions, but their rates of convergence are typically linear. In this paper we propose to modify the Newton method for variational inequality problems by using a certain differentiable merit function to determine a suitable step length. The purpose of introducing this merit function is to provide some measure of the discrepancy between the solution and the current iterate. It is then shown that, under the strong monotonicity assumption, the method is globally convergent and, under some additional assumptions, the rate of convergence is quadratic. Limited computational experience indicates the high efficiency of the proposed method. 相似文献
279.
280.
Fusion-evaporation cross-sections for the α-induced reactions upon197Au,193Ir,191Ir,185Re,181Ta,121Sb and69Ga nuclei at bombarding energies near the Coulomb barrier have been measured by off-line observation of the γ-rays emitted
in the radioactive decay of the residual nuclei using stacked foil technique. The total fusion cross-section for the systems
have been compared with simple statistical model calculations using the code ALICE/91 as well as with the coupled channel
calculations that include the β2 and ν4 slatic deformations and dynamic couplings of the vibrational/rotational states of the target and the projet tile using the
code CCDEF. 相似文献