全文获取类型
收费全文 | 38230篇 |
免费 | 4200篇 |
国内免费 | 5223篇 |
专业分类
化学 | 32265篇 |
晶体学 | 886篇 |
力学 | 1683篇 |
综合类 | 253篇 |
数学 | 3884篇 |
物理学 | 8682篇 |
出版年
2024年 | 54篇 |
2023年 | 472篇 |
2022年 | 720篇 |
2021年 | 1086篇 |
2020年 | 1349篇 |
2019年 | 1299篇 |
2018年 | 1129篇 |
2017年 | 1457篇 |
2016年 | 1591篇 |
2015年 | 1436篇 |
2014年 | 1766篇 |
2013年 | 2817篇 |
2012年 | 2186篇 |
2011年 | 2534篇 |
2010年 | 2041篇 |
2009年 | 2550篇 |
2008年 | 2335篇 |
2007年 | 2367篇 |
2006年 | 2130篇 |
2005年 | 1938篇 |
2004年 | 1986篇 |
2003年 | 1563篇 |
2002年 | 1901篇 |
2001年 | 1168篇 |
2000年 | 951篇 |
1999年 | 785篇 |
1998年 | 661篇 |
1997年 | 599篇 |
1996年 | 654篇 |
1995年 | 614篇 |
1994年 | 570篇 |
1993年 | 392篇 |
1992年 | 411篇 |
1991年 | 245篇 |
1990年 | 183篇 |
1989年 | 169篇 |
1988年 | 178篇 |
1987年 | 135篇 |
1986年 | 110篇 |
1985年 | 101篇 |
1984年 | 95篇 |
1983年 | 40篇 |
1982年 | 90篇 |
1981年 | 125篇 |
1980年 | 128篇 |
1979年 | 134篇 |
1978年 | 108篇 |
1977年 | 82篇 |
1976年 | 77篇 |
1973年 | 37篇 |
排序方式: 共有10000条查询结果,搜索用时 697 毫秒
71.
72.
E. L. Kristallovich A. G. Eshimbetov N. D. Chuvylkin L. I. Belen'kii Kh. M. Shakhidoyatov 《Chemistry of Natural Compounds》2003,39(5):495-500
The principal types of electronic transitions in absorption spectra of deoxyvasicinone and its 6-amino- and 6-nitro-derivatives were determined by analyzing the electron-density distributions in excited states calculated using ZINDO/S. 相似文献
73.
74.
75.
Mrio J. Edmundo 《Mathematical Logic Quarterly》2005,51(6):639-641
We show that if G is a definably compact, definably connected definable group defined in an arbitrary o‐minimal structure, then G is divisible. Furthermore, if G is defined in an o‐minimal expansion of a field, k ∈ ? and pk : G → G is the definable map given by pk (x ) = xk for all x ∈ G , then we have |(pk )–1(x )| ≥ kr for all x ∈ G , where r > 0 is the maximal dimension of abelian definable subgroups of G . (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
76.
富勒烯 (C60 /C70 )与N ,N ,N′ ,N′ 四 (对甲苯基 ) 4,4′ 二胺 1,1′ 二苯硒醚 (TPDASe)间在激光光诱导条件下 ,发生了分子间的电子转移过程 .在可见 -近红外区 ( 60 0~ 12 0 0nm) ,观测到了TPDASe阳离子自由基、富勒烯 (C60 /C70 )激发三线态和阴离子自由基 ,在苯腈溶液中 ,观测瞬态谱测定了电子从TPDASe转移到富勒烯 (C60 /C70 )激发三线态的量子转化产率(ΦTet)和电子转移常数 (Ket) . 相似文献
77.
On the Application of the Auxiliary Problem Principle 总被引:6,自引:0,他引:6
The auxiliary problem principle (APP) derives from a general theory on decomposition-coordination methods establishing a comprehensive framework for both one-level and two-level methods. In this paper, the results of the two-level methods of APP are specialized for an efficient application to some engineering problems. 相似文献
78.
Monika Goikoetxea María J. Barandiaran José M. Asua 《Journal of polymer science. Part A, Polymer chemistry》2007,45(24):5838-5846
The mechanisms involved in the formation of n‐butanol during the synthesis of butyl acrylate containing latices were investigated. The experimental results showed that neither the hydrolysis of butyl acrylate nor of the ester bond in the butyl acrylate segments of the polymer played a major role in the formation of n‐butanol, which was mainly generated from the polymer backbone, by transfer reactions to polymer chain followed by cyclization. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5838–5846, 2007 相似文献
79.
Hana Macková Daniela Králová Daniel Horák 《Journal of polymer science. Part A, Polymer chemistry》2007,45(24):5884-5898
The aim of this study was to develop novel thermally responsive polymer microspheres with magnetic properties. Dispersion and inverse emulsion copolymerization of N‐isopropylacrylamide (NIPAAm) and N,N′‐methylenebisacrylamide (MBAAm) was investigated in the presence of γ‐Fe2O3 nanoparticles. The resulting microspheres were characterized in terms of morphology, size, polydispersity, iron content, and temperature‐dependent swelling using optical microscopy, transmission electron microscopy, scanning electron microscopy, QELS, and AAS. The effects of several variables, such as the concentration of γ‐Fe2O3, MBAAm crosslinking agent, Span 80 surfactant, 2,2′‐azobis(2‐methyloctanenitrile) (AMON) initiator, and polymerization temperature on the properties of the microspheres were studied. Swelling and thermoresponsive behavior of the microspheres containing γ‐Fe2O3 nanoparticles were also investigated. The microspheres contained about 8 wt % of iron. The presence of magnetic nanoparticles and their concentration changes did not have any significant effect on the temperature sensitivity of the composites. The particles gradually shrink into an increasingly collapsed state when the temperature is raised to 40 °C since the increase in temperature weakens the hydration and PNIPAAm chains gradually become more hydrophobic, which leads to the collapse of the particles. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5884–5898, 2007 相似文献
80.
基于CSCW的协同编著系统的设计 总被引:3,自引:0,他引:3
讨论了计算机支持的协同工作(CSCW)的主要技术,其中重点讨论了协同编著系统设计中的并发控制技术,指出了其与传统的并发控制技术的区别。根据CSCW的基本原理设计出了一个基于Browse/Server结构的协同编著系统的系统模型。该系统模型比传统的模型更加方便了用户之间通过Internet的浏览器进行协作。 相似文献