全文获取类型
收费全文 | 80774篇 |
免费 | 24745篇 |
国内免费 | 20153篇 |
专业分类
化学 | 51280篇 |
晶体学 | 1316篇 |
力学 | 5509篇 |
综合类 | 515篇 |
数学 | 10829篇 |
物理学 | 56223篇 |
出版年
2023年 | 718篇 |
2022年 | 906篇 |
2021年 | 786篇 |
2020年 | 1017篇 |
2019年 | 1555篇 |
2018年 | 1564篇 |
2017年 | 2317篇 |
2016年 | 2294篇 |
2015年 | 2633篇 |
2014年 | 2504篇 |
2013年 | 4388篇 |
2012年 | 4726篇 |
2011年 | 6318篇 |
2010年 | 9725篇 |
2009年 | 10140篇 |
2008年 | 4089篇 |
2007年 | 3504篇 |
2006年 | 3203篇 |
2005年 | 3525篇 |
2004年 | 4293篇 |
2003年 | 3341篇 |
2002年 | 3166篇 |
2001年 | 3464篇 |
2000年 | 2788篇 |
1999年 | 2749篇 |
1998年 | 2244篇 |
1997年 | 2000篇 |
1996年 | 2320篇 |
1995年 | 2790篇 |
1994年 | 2835篇 |
1993年 | 2912篇 |
1992年 | 2467篇 |
1991年 | 2126篇 |
1990年 | 1772篇 |
1989年 | 1886篇 |
1988年 | 1874篇 |
1987年 | 1151篇 |
1986年 | 1206篇 |
1985年 | 856篇 |
1984年 | 977篇 |
1982年 | 904篇 |
1981年 | 745篇 |
1980年 | 777篇 |
1979年 | 538篇 |
1978年 | 541篇 |
1977年 | 636篇 |
1976年 | 1044篇 |
1973年 | 437篇 |
1972年 | 532篇 |
1971年 | 432篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
991.
YBa2Cu3O7-δ and Tl2Ba2CaCu2O8 thin films for microwave filters were synthesized by pulsed laser deposition and the two-step thalliation process. Substrate
quality requirements and the relation of thin film morphology, microstructure with microwave surface resistance were discussed. 相似文献
992.
993.
994.
S. Takahashi T. Yamashita H. Imamura S. Maekawa 《Journal of magnetism and magnetic materials》2002,240(1-3):100-102
The effect of spin relaxation on tunnel magnetoresistance (TMR) in a ferromagnet/superconductor/ferromagnet (FM/SC/FM) double tunnel junction is theoretically studied. The spin accumulation in SC is determined by balancing of the spin-injection rate and the spin-relaxation rate. In the superconducting state, the spin-relaxation time τs becomes longer with decreasing temperature, resulting in a rapid increase of TMR. The TMR of FM/SC/FM junctions provides a useful probe to extract information about spin-relaxation in superconductors. 相似文献
995.
996.
997.
New derivation results for integrands and multifunctions via the Lipschitzean approximations are obtained. Applications to multivalued differential equations on closed convex sets are presented. 相似文献
998.
通过对宁波港的交通环境,现有VTS系统及港口发展的趋势研究,提出了改善宁波港通航环境,建立和完善VTS系统的有效措施。 相似文献
999.
Cyclic voltammetric studies of certain industrially potential iron chelate catalysts 总被引:1,自引:0,他引:1
For the analysis of infrared spectroscopic bands and complex patterns partial cross correlation functions of a sample spectrum
with reference spectra are calculated. The chosen ranges of the spectra are based on empirical knowledge of infrared spectrum
structure correlations. The normalised maxima of the partial cross correlation functions are interpreted as fuzzy truth values
and are combined by fuzzy logical operators. By application of that procedure larger common substructures will be derived
from the reference spectra than by a maximum common substructure search based on the complete spectra.
Received: 30 October 1996/Revised: 24 February 1997/Accepted: 26 February 1997 相似文献
1000.
Vladimir V. Veremey Yury A. Tuchkin 《International Journal of Infrared and Millimeter Waves》1997,18(4):909-938
An analysis of resonances of scattering from multi-element grating formed by a finite number of resonant elements is presented.
It has been shown that gratings with three and more elements on its period can support the π-mode. The π-mode of a grating
is characterized by the existence of the regions in the vicinity of the grating and along its period where the electromagnetic
field has opposite phases. The existence and excitation of the π-mode in finite gratings with resonant cells formed by several
scatterers having open cavities have been studied. The particular case of the grating with cells formed by three identical
slotted cylinders has been considered in detail. An application of gratings which support the π-mode in electron-vacuum oscillators
of millimeter waves for efficient deceleration of electrons and extracting energy from electron beam is discussed. 相似文献