全文获取类型
收费全文 | 15310篇 |
免费 | 3050篇 |
国内免费 | 2366篇 |
专业分类
化学 | 11782篇 |
晶体学 | 246篇 |
力学 | 999篇 |
综合类 | 159篇 |
数学 | 1778篇 |
物理学 | 5762篇 |
出版年
2024年 | 45篇 |
2023年 | 254篇 |
2022年 | 468篇 |
2021年 | 546篇 |
2020年 | 611篇 |
2019年 | 680篇 |
2018年 | 549篇 |
2017年 | 519篇 |
2016年 | 866篇 |
2015年 | 915篇 |
2014年 | 971篇 |
2013年 | 1184篇 |
2012年 | 1395篇 |
2011年 | 1363篇 |
2010年 | 1076篇 |
2009年 | 1060篇 |
2008年 | 1096篇 |
2007年 | 947篇 |
2006年 | 849篇 |
2005年 | 751篇 |
2004年 | 647篇 |
2003年 | 552篇 |
2002年 | 677篇 |
2001年 | 564篇 |
2000年 | 385篇 |
1999年 | 312篇 |
1998年 | 251篇 |
1997年 | 180篇 |
1996年 | 179篇 |
1995年 | 141篇 |
1994年 | 117篇 |
1993年 | 92篇 |
1992年 | 91篇 |
1991年 | 80篇 |
1990年 | 65篇 |
1989年 | 52篇 |
1988年 | 34篇 |
1987年 | 24篇 |
1986年 | 24篇 |
1985年 | 12篇 |
1984年 | 19篇 |
1983年 | 12篇 |
1982年 | 7篇 |
1981年 | 13篇 |
1980年 | 6篇 |
1979年 | 8篇 |
1978年 | 5篇 |
1976年 | 4篇 |
1974年 | 6篇 |
1971年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
41.
该文给出了帐篷映射产生的迭代序列Cesaro平均收敛的条件.研究了它与实数二进展式度量性质之间的联系. 相似文献
42.
LI Zi-jian LIU Ning LIU Zhi-qiang LIU Shu-ying HAN Qi-de ZHANG You-yi . Institute of Vascular Medicine Peking University Third Hospital Key Laboratory of Molecular Cardiovascular Sciences Ministry of Education Beijing P. R. China . Changchun Institute of Applied Chemistry Chinese Academy of Sciences Changchun P. R. China 《高等学校化学研究》2006,22(3):319-323
Introduction Adrenoceptors(ARs),membersofthesuperfami lyofG proteincoupledreceptors,arethemostimpor tantreceptorsinvolvedincardiacregulation[1].ARsin cardiacmuscleincludebothαARsandβARssub types,whileinmostmammalianheart,βARsarethe predominantsubtypes.… 相似文献
43.
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
44.
第一讲中子散射与散裂中子源 总被引:1,自引:0,他引:1
中子散射是研究物质微观结构和动态的理想工具之一,广泛地应用于凝聚态物质研究和应用的众多学科领域.散裂中子源能是新一代的加速器基脉冲中子源,能为中子散射提供高通量的脉冲中子.文章简明地介绍了中子散射的特点和它作为物质结构和动态探针的优越性,以及散裂中子源的基本原理、发展状况和多学科的应用优势.我国计划建设的散裂中子源CSNS中,靶站将由多片钨靶、铍/铁反射体和铁/重混凝土生物屏蔽体组成.质子束功率100kW下,脉冲中子通量约为2.4×1016n/cm2/s.第一期将设计建造高通量粉末衍射仪、高分辨粉末衍射仪、小角散射仪、多功能反射仪和直接几何非弹性散射仪等五台典型的中子散射谱仪,以覆盖大部分的中子散射研究领域. 相似文献
45.
46.
Tensile impact experiments of EC8.0−24×7 glass fiber bundles at different low temperaturesT(14°C, −40°C and −10°C) and strain rates ɛ were carried out, and complete stress-strain curves were obtained. Within the range
of the experiment temperatures and strain rates, it is found that the initial modulusE, the ultimate strength σmax and the unstable strain ɛ
b
of the glass fiber bundles all increase with ɛ at an identicalT. At an identical ɛ, with the decrease ofT, E and σmax increase; but ɛ
b
increases when 10°C>T>−40°C and decreases when −40°C>T>−100°C. The strain-rate- and temperature-dependent bimodal Weibull statistical constitutive theory was adopted for the statistical
analysis of the experimental results, and the Weibull parameters of single fiber were obtained. The results show that the
bimodal Weibull distribution function is suitable to represent the strength distribution of the glass fiber at low temperature
and different strain rates. The differences in the mechanical properties between EC8.0−24×7 and EC5.5−12 ×14 glass fiber bundles
were also discussed.
Project supported by the National Natural Science Foundation of China (No. 19772058). 相似文献
47.
A Multi-component Matrix Loop Algebra and Its Application 总被引:3,自引:0,他引:3
DONG Huan-He ZHANG Ning 《理论物理通讯》2005,44(6):997-1001
A set of multi-component matrix Lie algebra is constructed. It follows that a type of new loop algebra A^- M-1 is presented. An isospectral problem is established. Integrable multi-component hierarchy is obtained by Tu pattern, which possesses tri-Hamiltonian structures. Furthermore, it can be reduced to the well-known AKNS hierarchy and BPT hierarchy. Therefore, the major result of this paper can be regarded as a unified expression integrable model of the AKNS hierarchy and the BPT hierarchy. 相似文献
48.
Shu Fen Wang Wen Guo Zou Su Wen Liu Dong Xu Duo Rong Yuan Guang Jun Zhou 《Journal of Physics and Chemistry of Solids》2004,65(7):1243-1245
The photoluminescence properties of the Bi3+ in sol-gel derived ZnTiO3 nanocrystals have been investigated. An ultra-violet emission at 360 nm and a visible emission band at 506 nm have been observed, originating from two kinds of emission centers. The former is ascribed to the 3P1-1S0 transition of Bi3+ and the latter to the recombination of the electrons with the photo-generated holes trapped in the zinc vacancies. In all cases the latter contribution is predominant. 相似文献
49.
50.
Andrew Bach Xinglong Jiang Joseph Mckenna Kapa Prasad Oljan Repic Wen‐Chung Shieh 《Journal of heterocyclic chemistry》2004,41(4):637-640
An efficient approach has been developed for the synthesis of an isofervenulin analogue 1 employing a one‐pot condensation‐substitution reaction of a chlorocarboethoxytriazine (electrophile) with a urea (nucleophile). The resulting cyclization reaction resulted in the synthesis of a pyrimido‐heterocycle in good yield in either acidic or basic media. The former was assisted by utilizing trimethylsilyl chloride. 相似文献