全文获取类型
收费全文 | 5831篇 |
免费 | 111篇 |
国内免费 | 30篇 |
专业分类
化学 | 3578篇 |
晶体学 | 15篇 |
力学 | 173篇 |
数学 | 1318篇 |
物理学 | 888篇 |
出版年
2020年 | 59篇 |
2019年 | 41篇 |
2016年 | 91篇 |
2015年 | 74篇 |
2014年 | 85篇 |
2013年 | 215篇 |
2012年 | 184篇 |
2011年 | 196篇 |
2010年 | 136篇 |
2009年 | 132篇 |
2008年 | 191篇 |
2007年 | 216篇 |
2006年 | 181篇 |
2005年 | 203篇 |
2004年 | 167篇 |
2003年 | 130篇 |
2002年 | 112篇 |
2001年 | 47篇 |
2000年 | 59篇 |
1999年 | 52篇 |
1998年 | 46篇 |
1997年 | 66篇 |
1996年 | 66篇 |
1995年 | 80篇 |
1994年 | 80篇 |
1993年 | 72篇 |
1992年 | 87篇 |
1991年 | 60篇 |
1990年 | 65篇 |
1989年 | 74篇 |
1988年 | 85篇 |
1987年 | 72篇 |
1986年 | 87篇 |
1985年 | 121篇 |
1984年 | 114篇 |
1983年 | 85篇 |
1982年 | 120篇 |
1981年 | 121篇 |
1980年 | 110篇 |
1979年 | 120篇 |
1978年 | 108篇 |
1977年 | 108篇 |
1976年 | 96篇 |
1975年 | 110篇 |
1974年 | 82篇 |
1973年 | 88篇 |
1972年 | 55篇 |
1971年 | 60篇 |
1970年 | 63篇 |
1966年 | 47篇 |
排序方式: 共有5972条查询结果,搜索用时 15 毫秒
1.
2.
Computational Optimization and Applications - It has been shown that a global minimizer of a smooth determinant of a matrix function corresponds to the largest cycle of a graph. When it exists,... 相似文献
3.
Shoraku Ryu Kazuo Furihata Masanori Koda Feifei Wei Takuya Miyakawa Masaru Tanokura 《Magnetic resonance in chemistry : MRC》2016,54(3):213-221
Japanese persimmon (Diospyros kaki L.) is recognized as an outstanding source of biologically active compounds relating to many health benefits. In the present study, NMR spectroscopy provided a comprehensive metabolic overview of Japanese persimmon juice. Detailed signal assignments of Japanese persimmon juice were carried out using various 2D NMR techniques incorporated with broadband water suppression enhanced through T1 effects (BB‐WET) or WET sequences, and 26 components, including minor components, were identified. In addition, most components were quantitatively evaluated by the integration of signals using conventional 1H NMR and BB‐WET NMR. This is the first detailed analysis combined with quantitative characterization of chemical components using NMR for Japanese persimmon. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
4.
5.
6.
Nadia Lahrichi Teodor Gabriel Crainic Michel Gendreau Walter Rei Louis-Martin Rousseau 《The Journal of the Operational Research Society》2015,66(1):44-56
The dairy transportation problem (DTP) consists of determining the best routes to be performed for collecting milk from farms and delivering it to processing plants. We study the particular case of the province of Quebec, where the Fédération des producteurs de lait du Québec is responsible for negotiating the transportation costs on behalf of producers. Several issues are highlighted in the actual process of designing contracts such as using historical data. We propose an approach based on scenario analysis that consists of revising both the steps and the information used to construct the routes. We develop a generalized tabu search algorithm that integrates the different characteristics of the DTP. 相似文献
7.
8.
Chromatographia - Drug scheduling has directed the testing approaches for forensic laboratories since the 1970s when Cannabis (marijuana and hemp) and its psychoactive constituent,... 相似文献
9.
10.
Dr. Mykhaylo Dukh Walter A. Tabaczynski Sairaman Seetharaman Dr. Zhongping Ou Prof. Dr. Karl M. Kadish Prof. Dr. Francis D'Souza Prof. Dr. Ravindra K. Pandey 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(65):14996-15006
A series of chlorin-bacteriochlorin dyads (derived from naturally occurring chlorophyll-a and bacteriochlorophyll-a), covalently connected either through the meso-aryl or β-pyrrole position (position-3) via an ester linkage have been synthesized and characterized as a new class of far-red emitting fluorescence resonance energy transfer (FRET) imaging, and heavy atom-lacking singlet oxygen-producing agents. From systematic absorption, fluorescence, electrochemical, and computational studies, the role of chlorin as an energy donor and bacteriochlorin as an energy acceptor in these wide-band-capturing dyads was established. Efficiency of FRET evaluated from spectral overlap was found to be 95 and 98 % for the meso-linked and β-pyrrole-linked dyads, respectively. Furthermore, evidence for the occurrence of FRET from singlet-excited chlorin to bacteriochlorin was secured from studies involving femtosecond transient absorption studies in toluene. The measured FRET rate constants, kFRET, were in the order of 1011 s−1, suggesting the occurrence of ultrafast energy transfer in these dyads. Nanosecond transient absorption studies confirmed relaxation of the energy transfer product, 1BChl*, to its triplet state, 3Bchl*. The 3Bchl* thus generated was capable of producing singlet oxygen with quantum yields comparable to their monomeric entities. The occurrence of efficient FRET emitting in the far-red region and the ability to produce singlet oxygen make the present series of dyads useful for photonic, imaging and therapy applications. 相似文献