全文获取类型
收费全文 | 35131篇 |
免费 | 5564篇 |
国内免费 | 4172篇 |
学科分类
数理化 | 44867篇 |
出版年
2024年 | 110篇 |
2023年 | 665篇 |
2022年 | 1153篇 |
2021年 | 1255篇 |
2020年 | 1327篇 |
2019年 | 1334篇 |
2018年 | 1134篇 |
2017年 | 1073篇 |
2016年 | 1665篇 |
2015年 | 1628篇 |
2014年 | 1931篇 |
2013年 | 2554篇 |
2012年 | 3113篇 |
2011年 | 3054篇 |
2010年 | 2159篇 |
2009年 | 1937篇 |
2008年 | 2199篇 |
2007年 | 1955篇 |
2006年 | 1872篇 |
2005年 | 1732篇 |
2004年 | 1327篇 |
2003年 | 1141篇 |
2002年 | 1213篇 |
2001年 | 866篇 |
2000年 | 783篇 |
1999年 | 794篇 |
1998年 | 612篇 |
1997年 | 591篇 |
1996年 | 561篇 |
1995年 | 501篇 |
1994年 | 410篇 |
1993年 | 369篇 |
1992年 | 315篇 |
1991年 | 269篇 |
1990年 | 273篇 |
1989年 | 207篇 |
1988年 | 158篇 |
1987年 | 110篇 |
1986年 | 115篇 |
1985年 | 122篇 |
1984年 | 63篇 |
1983年 | 59篇 |
1982年 | 51篇 |
1981年 | 39篇 |
1980年 | 19篇 |
1979年 | 10篇 |
1977年 | 3篇 |
1957年 | 8篇 |
1930年 | 2篇 |
1916年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
Guofen Yu Yuanci Gao Shenggang Liu Wenxiang Wang Jin Wu 《International Journal of Infrared and Millimeter Waves》2002,23(8):1261-1269
Analysis of the field distributions in a single biological cell under electromagnetic wave is given. With Debye approximation, the dielectric relaxation of each part of the cell, including the extracellular and cellular media, the cell membrane and the nuclear membrane, was taken into account. Making use of some typical parameters for a cell, the voltage across nuclear and cytoplasma membranes under electromagnetic waves are calculated up to millimeter wave frequency range. The calculated result indicates that it is unlikely to generate electroporation by present available millimeter wave sources. 相似文献
4.
5.
Syntheses, structures, and properties of novel molybdenum and tungsten complexes of fullerenes 总被引:1,自引:0,他引:1
The synthesis and characterization of several fullerene-based organometallic complexes containing Mo and W is reported. 相似文献
6.
Jong Chan Lee Jin Young Park So Young Yoon Yong Hun Bae Seung Jun Lee 《Tetrahedron letters》2004,45(1):191-193
A novel and direct method for the synthesis of α-halocarbonyl compounds using sequential treatment of carbonyl compounds with [hydroxy(tosyloxy)iodo]benzene followed by magnesium halides under solvent-free microwave irradiation conditions is described. 相似文献
7.
使用Monte Carlo模拟的方法得出了随机粗糙表面,在Kirchhoff近似的基础上,利用数值分析的方法分析了一维随机粗糙表面的散射特征,得出了一维随机粗糙表面散射分布曲线,我们还考虑了遮蔽效应的影响,并且讨论了Kirchhoff近似的有效性。 相似文献
8.
Guangchang Zhou Jibao He Issifu I. Harruna 《Journal of polymer science. Part A, Polymer chemistry》2007,45(18):4204-4210
Amphiphilic tris(2,2′‐bipyridine)ruthenium‐cored star‐shaped polymers consisting of one polystyrene block and two poly(N‐isopropylacrylamide) blocks were prepared by the “arm‐first” method in which RAFT polymerization and nonconvalent ligand–metal complexation were employed. The prepared amphiphilic star‐shaped metallopolymers are able to form micelles in water. The size and distribution of the micelles were studied by dynamic light scattering and transmission electron microscopy techniques. Preliminary studies indicate that the polymer concentration and the hydrophilic poly(N‐isopropylacrylamide) block length can affect the morphologies of the formed metal‐interfaced core–shell micelles in water. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4204–4210, 2007 相似文献
9.
A novel and simple two-frequency Brillouin fiber laser is presented. It is based on a fiber Fabry-Perot cavity with fiber Bragg gratings as reflectors. The model of stimulated Brillouin scattering in fiber grating-based Fabry-Perot resonator is investigated. The laser allows conversion efficiency of close to 100% and suppresses the higher-order Stokes waves. The theoretical prediction is presented and the experimental demonstration is realized. 相似文献
10.
Dong‐Cheol Shin Yun‐Hi Kim Hong You Jae Gyu Jin Soon‐Ki Kwon 《Journal of polymer science. Part A, Polymer chemistry》2004,42(22):5636-5646
A poly(p‐phenylenevinylene) (PPV) derivative containing a bulky (2,2‐diphenylvinyl)phenyl group in the side chain, EHDVP‐PPV, was synthesized by Gilch route. The reduced tolane‐bisbenzyl (TBB) defects, as well as the structure of the polymer, was confirmed by various spectroscopic methods. The intramolecular energy transfer from the (2,2‐diphenylvinyl)phenyl side group to the PPV backbone was studied by UV‐vis and photoluminescence (PL) of the obtained polymer and model compound. The polymer film showed maximum absorption and emission peaks at 454 and 546 nm, respectively, and high PL efficiency of 57%. A yellow electroluminescence (λmax = 548 nm) was obtained with intensities of 6479 cd/m2 when the light‐emitting diodes of ITO/PEDOT/EHDVP‐PPV/LiF/Al were fabricated. The maximum power efficiency of the devices was 0.729 lm/W with a turn‐on voltage of 3.6 V. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5636–5646, 2004 相似文献