全文获取类型
收费全文 | 23866篇 |
免费 | 4353篇 |
国内免费 | 3832篇 |
专业分类
化学 | 17692篇 |
晶体学 | 472篇 |
力学 | 1509篇 |
综合类 | 333篇 |
数学 | 2698篇 |
物理学 | 9347篇 |
出版年
2024年 | 81篇 |
2023年 | 477篇 |
2022年 | 879篇 |
2021年 | 1033篇 |
2020年 | 1023篇 |
2019年 | 1065篇 |
2018年 | 924篇 |
2017年 | 921篇 |
2016年 | 1205篇 |
2015年 | 1384篇 |
2014年 | 1531篇 |
2013年 | 1892篇 |
2012年 | 2224篇 |
2011年 | 2189篇 |
2010年 | 1571篇 |
2009年 | 1669篇 |
2008年 | 1782篇 |
2007年 | 1553篇 |
2006年 | 1478篇 |
2005年 | 1153篇 |
2004年 | 994篇 |
2003年 | 801篇 |
2002年 | 900篇 |
2001年 | 750篇 |
2000年 | 551篇 |
1999年 | 435篇 |
1998年 | 308篇 |
1997年 | 202篇 |
1996年 | 190篇 |
1995年 | 154篇 |
1994年 | 124篇 |
1993年 | 130篇 |
1992年 | 82篇 |
1991年 | 64篇 |
1990年 | 59篇 |
1989年 | 59篇 |
1988年 | 39篇 |
1987年 | 38篇 |
1986年 | 38篇 |
1985年 | 33篇 |
1984年 | 16篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1971年 | 2篇 |
1966年 | 2篇 |
1957年 | 3篇 |
1936年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
孟昭英院士是著名物理学家、我国电子学开拓者,在清华大学物理系历史上是积极倡导“理工会通”教育思想的杰出大师,曾为我国培养了许多高级科技人才,有的成了我国某学科学术带头人,有的是佩戴上“两弹、一星”国家勋章的科学家.孟昭英先生一生辉煌、半生坎坷,但是即使在蒙受奇冤的年代,仍然以国家和民族大业为重,不懈努力.改革开放后,更是老骥伏枥,惮精竭虑地为清华大学物理系的重振作出了卓越贡献.值此孟昭英先生诞辰100周年之际,挥泪命笔写下此文。 相似文献
22.
Based on solving the couple mode equation numerically, the characterization of the signal power on the gate power was analyzed. And the relationship of the tolerance of the grating period and the bulk temperature on the interaction length was analyzed. 相似文献
23.
24.
25.
Because of package, a single FBG has dual Bragg wavelength. One is sensitive to stress and the other is sensitive to temperature. By using the special mechanism, the wavelengths can be tuned by stress and temperature respectively. 相似文献
26.
Characteristics and structures of weak efficient surfaces of production possibility sets 总被引:1,自引:0,他引:1
Quanling Wei Hong Yan Gang Hao 《Journal of Mathematical Analysis and Applications》2007,327(2):1055-1074
This paper studies the characteristics and structure of the weak surface of the production possibility set. We apply techniques and methods of transferring a polyhedral cone from its intersection form to its sum form, identify an intersection representation of the production possibility set. We give the structure theorem of weak surface of the production possibility set, which includes three complementary slackness conditions. We define the input weak efficiency and output weak efficiency for different DEA models according to the representation of the intersection form. It investigates the characteristics of the weak surfaces, and proves the structure theorems of input weak DEA efficiency and output weak DEA efficiency. The structure theorems establish weighted combination of inputs and outputs that are weak DEA efficient. Numerical examples are provided for illustration. 相似文献
27.
Qing Shi Dong Yang Yanlei Su Jian Li Zhongyi Jiang Yanjun Jiang Weikang Yuan 《Journal of nanoparticle research》2007,9(6):1205-1210
Lipase from Candida rugosa was covalently anchored onto acid-treated multi-walled carbon nanotubes (MWNTs) through a self-catalytic mechanism. A variety
of characterization techniques including FTIR, Raman spectroscopy, and XPS were employed to demonstrate the formation of the
ester linkage between lipase and MWNTs. The MWNTs-lipase biocomposites showed significantly increased solubility in some common-used
organic solvents, such as THF, DMF and chloroform. This study may offer a novel and facile route for covalent modification
of carbon nanotubes, and expand the potential utilization of both lipases and MWNTs in the fields of biocatalyst and biosensor. 相似文献
28.
This paper discusses a class of second-order derivative nonlinear Schrödinger equations which are used to describe the upper-hybrid oscillation propagation. By establishing a variational problem, applying the potential well argument and the concavity method, we prove that there exists a sharp condition for global existence and blow-up of the solutions to the nonlinear Schrödinger equation. In addition, we also answer the question: how small are the initial data, the global solutions exist? 相似文献
29.
Thin films of polystyrene (PS), poly(methyl methacrylate) (PMMA) and polystyrene-polyacrylonitrile copolymer (PS-AN), containing various embedded transition-metal complexes, have been studied by FTIR microscopy. The spatial distributions of the transition-metal carbonyl complexes throughout the thin organic polymer films have been determined by a two-dimensional IR mapping procedure. The spectral variations observed in the distribution of the metal carbonyls throughout the different polymer films are discussed. The IR data show that the technique used to prepare the organometallic-embedded thin films (viz. freeze-drying of solutions followed by hot mechanical pressing of the residues) does in general lead to homogeneous films which may eventually find industrial application, e.g. as membrane sensors for small molecules. 相似文献