全文获取类型
收费全文 | 50977篇 |
免费 | 4923篇 |
国内免费 | 3833篇 |
专业分类
化学 | 44078篇 |
晶体学 | 856篇 |
力学 | 1520篇 |
综合类 | 292篇 |
数学 | 830篇 |
物理学 | 12157篇 |
出版年
2024年 | 61篇 |
2023年 | 414篇 |
2022年 | 989篇 |
2021年 | 875篇 |
2020年 | 1235篇 |
2019年 | 1269篇 |
2018年 | 1360篇 |
2017年 | 1737篇 |
2016年 | 2168篇 |
2015年 | 1912篇 |
2014年 | 1907篇 |
2013年 | 4474篇 |
2012年 | 3107篇 |
2011年 | 2890篇 |
2010年 | 2521篇 |
2009年 | 2920篇 |
2008年 | 2534篇 |
2007年 | 2733篇 |
2006年 | 2507篇 |
2005年 | 2309篇 |
2004年 | 2113篇 |
2003年 | 1769篇 |
2002年 | 1762篇 |
2001年 | 1307篇 |
2000年 | 1371篇 |
1999年 | 1222篇 |
1998年 | 1061篇 |
1997年 | 977篇 |
1996年 | 911篇 |
1995年 | 947篇 |
1994年 | 753篇 |
1993年 | 643篇 |
1992年 | 536篇 |
1991年 | 500篇 |
1990年 | 445篇 |
1989年 | 389篇 |
1988年 | 487篇 |
1987年 | 442篇 |
1986年 | 362篇 |
1985年 | 343篇 |
1984年 | 339篇 |
1983年 | 171篇 |
1982年 | 295篇 |
1981年 | 208篇 |
1980年 | 180篇 |
1979年 | 169篇 |
1978年 | 36篇 |
1977年 | 11篇 |
1976年 | 9篇 |
1973年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
A method employing a wide pore polymeric reversed phase column has been developed for the separation of most of the chlorophylls and related compounds previously described as occurring in marine microalgae. The high selectivity toward molecular shape of this kind of stationary phase has enabled compounds of very similar structure, such as chlorophylls c1, c2 and Mg-divinylpheoporphyrin a5 monomethyl ester, and chlorophyll a and the phytol-substituted chlorophyll c-like pigments, which commonly coelute on monomeric bonded phases, to be resolved in a single run. Some of these pigments, formerly thought to be a single compound, have, in fact, been demonstrated to be groups of two or more. The method has been successfully applied to both algal cultures and natural sea water samples. When visible light absorbance detection was used, the method proved suitable for separation of various carotenoids. 相似文献
102.
激光相位成像雷达的研究 总被引:1,自引:0,他引:1
利用无合作目标漫反射激光相位测距的原理,对关键单元技术进行分析和设计,研制成一种用于自主式车辆视觉导引的激光相位成像雷达的原理样机. 相似文献
103.
脂肪乳剂Intralipid代谢产物的高效液相色谱测定 总被引:2,自引:0,他引:2
本文介绍了利用HPLC色谱柱前衍生化技术简便,正确和灵敏地测定血清中游离脂肪酸的方法。在最佳条件下,一些脂肪酸的最低检知量为0.04μg。方法已用于脂肪乳剂Intralipid在诱发急性坏死性胰腺炎动物体内代谢产物测定。 相似文献
104.
105.
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
106.
107.
V.I. Fernández A. Iucci C.M. Naón 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(1):53-56
We present an extension of the Tomonaga-Luttinger model in which left and right-moving particles have different Fermi velocities.
We derive expressions for one-particle Green's functions, momentum-distributions, density of states, charge compressibility
and conductivity as functions of both the velocity difference ε and the strength of the interaction β. This allows us to identify
a novel restricted region in the parameter space in which the system keeps the main features of a Luttinger liquid but with
an unusual behavior of the density of states and the static charge compressibility κ. In particular κ diverges on the boundary
of the restricted region, indicating the occurrence of a phase transition.
Received 20 May 2002 / Received in final form 23 August 2002 Published online 19 November 2002 相似文献
109.
A novel type of corner reflector for the reflection of surface plasmon polariton (SPP) is proposed. The reflector consists
of two layers of compensatory media whose permittivity and permeability take opposite signs to that of the corresponding layer
of the SP waveguide. By rigorously solving Maxwell's equations, the reflected SPP is proved to exist. The transverse wave
vector of the reflected SPP is always antiparallel to that of the incident SPP and no phase retardation is introduced. 相似文献
110.
The impact of fabrication errors on a planar waveguide demultiplexer is analyzed based on an analytical method. The explicit
expression of the transfer function taking into account phase and amplitude errors is presented in order to analyze the loss
and crosstalk of the demultiplexer caused by fabrication errors. A basic requirement for the demultiplexer with a certain
crosstalk criterion can be easily obtained. Using an etched diffraction grating demultiplexer as an example, it is shown that
the analytical results have a good agreement with results from a numerical method. 相似文献