全文获取类型
收费全文 | 28583篇 |
免费 | 5168篇 |
国内免费 | 4436篇 |
专业分类
化学 | 21616篇 |
晶体学 | 546篇 |
力学 | 1625篇 |
综合类 | 376篇 |
数学 | 3109篇 |
物理学 | 10915篇 |
出版年
2024年 | 20篇 |
2023年 | 457篇 |
2022年 | 568篇 |
2021年 | 796篇 |
2020年 | 1025篇 |
2019年 | 1135篇 |
2018年 | 871篇 |
2017年 | 888篇 |
2016年 | 1279篇 |
2015年 | 1322篇 |
2014年 | 1611篇 |
2013年 | 2098篇 |
2012年 | 2651篇 |
2011年 | 2683篇 |
2010年 | 2073篇 |
2009年 | 2030篇 |
2008年 | 2303篇 |
2007年 | 1942篇 |
2006年 | 1878篇 |
2005年 | 1757篇 |
2004年 | 1369篇 |
2003年 | 1097篇 |
2002年 | 1087篇 |
2001年 | 906篇 |
2000年 | 710篇 |
1999年 | 591篇 |
1998年 | 437篇 |
1997年 | 344篇 |
1996年 | 330篇 |
1995年 | 276篇 |
1994年 | 307篇 |
1993年 | 223篇 |
1992年 | 190篇 |
1991年 | 193篇 |
1990年 | 132篇 |
1989年 | 118篇 |
1988年 | 82篇 |
1987年 | 45篇 |
1986年 | 64篇 |
1985年 | 58篇 |
1984年 | 34篇 |
1983年 | 33篇 |
1982年 | 25篇 |
1981年 | 24篇 |
1980年 | 18篇 |
1979年 | 15篇 |
1978年 | 15篇 |
1977年 | 14篇 |
1976年 | 9篇 |
1974年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
83.
A Convenient Synthesis of N‐Aryl Benzamides by Rhodium‐Catalyzed ortho‐Amidation and Decarboxylation of Benzoic Acids 下载免费PDF全文
Dr. Xian‐Ying Shi Ke‐Yan Liu Juan Fan Xue‐Fen Dong Prof. Dr. Jun‐Fa Wei Prof. Dr. Chao‐Jun Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(5):1900-1903
The rhodium‐catalyzed amidation of substituted benzoic acids with isocyanates by directed C?H functionalization followed by decarboxylation to afford the corresponding N‐aryl benzamides is demonstrated, in which the carboxylate serves as a unique, removable directing group. Notably, less common meta‐substituted N‐aryl benzamides are generated readily from more accessible para‐ or ortho‐substituted groups by employing this strategy. 相似文献
84.
85.
86.
87.
Host–Guest Assembly of a Molecular Reporter with Chiral Cyanohydrins for Assignment of Absolute Stereochemistry 下载免费PDF全文
Hadi Gholami Dr. Mercy Anyika Jun Zhang Dr. Chrysoula Vasileiou Prof. Dr. Babak Borhan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(27):9235-9239
The absolute stereochemistry of cyanohydrins, derived from ketones and aldehydes, is obtained routinely, in a microscale and derivatization‐free manner, upon their complexation with Zn‐MAPOL, a zincated porphyrin host with a binding pocket comprised of a biphenol core. The host–guest complex leads to observable exciton‐coupled circular dichroism (ECCD), the sign of which is easily correlated to the absolute stereochemistry of the bound cyanohydrin. A working model, based on the ECCD signal of cyanohydrins with known configuration, is proposed. 相似文献
88.
89.
Ao‐kai Zhang Jun Ling Kewen Li Guo‐dong Fu Tasuku Nakajima Takayuki Nonoyama Takayuki Kurokawa Jian Ping Gong 《Journal of Polymer Science.Polymer Physics》2016,54(13):1227-1236
In this study, controlled amount of dangling ends is introduced to the two series of poly(ethylene glycol)‐based hydrogel networks with three and four crosslinking functionality by using click chemistry. The structure of the gels with regulated defect percentage is confirmed by comparing the results of low‐field NMR characterization and Monte Carlo simulation. The mechanical properties of these gels were characterized by tensile stress–strain behaviors of the gels, and the results are analyzed by Gent model and Mooney–Rivlin model. The shear modulus of the swollen gels is found to be dependent on the functionality of the network, and decreases with the defect percentage. Furthermore, the value of shear modulus well obeys the Phantom model for all the gels with varied percentage of the defects. The maximum extension ratio, obtained from the fitting of Gent model, is also found to be dependent on the functionality of the network, and does not change with the defect percentage, except at very high defect percentage. The value of the maximum extension ratio is between that predicted from Phantom model and the Affine model. This indicates that at the large deformation, the fluctuation of the crosslinking points is suppressed for some extend but still exists. Polymer volume fractions at various defect percentages obtained from prediction of Flory–Rehner model are found to be in well agreement with the swelling experiment. All these results indicate that click chemistry is a powerful method to regulate the network structure and mechanical properties of the gels. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1227–1236 相似文献
90.