全文获取类型
收费全文 | 66232篇 |
免费 | 14837篇 |
国内免费 | 6169篇 |
专业分类
化学 | 61964篇 |
晶体学 | 759篇 |
力学 | 2795篇 |
综合类 | 406篇 |
数学 | 5865篇 |
物理学 | 15449篇 |
出版年
2024年 | 57篇 |
2023年 | 611篇 |
2022年 | 885篇 |
2021年 | 1223篇 |
2020年 | 2376篇 |
2019年 | 3588篇 |
2018年 | 2033篇 |
2017年 | 1644篇 |
2016年 | 4704篇 |
2015年 | 4883篇 |
2014年 | 5219篇 |
2013年 | 6274篇 |
2012年 | 5702篇 |
2011年 | 5147篇 |
2010年 | 4939篇 |
2009年 | 4857篇 |
2008年 | 4643篇 |
2007年 | 3788篇 |
2006年 | 3509篇 |
2005年 | 3312篇 |
2004年 | 2753篇 |
2003年 | 2356篇 |
2002年 | 3160篇 |
2001年 | 2246篇 |
2000年 | 2061篇 |
1999年 | 1123篇 |
1998年 | 590篇 |
1997年 | 504篇 |
1996年 | 513篇 |
1995年 | 423篇 |
1994年 | 374篇 |
1993年 | 300篇 |
1992年 | 283篇 |
1991年 | 224篇 |
1990年 | 189篇 |
1989年 | 166篇 |
1988年 | 154篇 |
1987年 | 93篇 |
1986年 | 81篇 |
1985年 | 70篇 |
1984年 | 38篇 |
1983年 | 39篇 |
1982年 | 17篇 |
1981年 | 22篇 |
1980年 | 17篇 |
1979年 | 8篇 |
1978年 | 15篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1957年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
141.
142.
Julien Ferrari Christian Terreaux Tibor Kurtn Attila Szikszai‐Kiss Sndor Antus JeromeD. Msonthi Kurt Hostettmann 《Helvetica chimica acta》2003,86(8):2768-2778
Investigation of the methanol extract of the roots of Gnidia involucrata (Thymelaeaceae) led to the isolation and characterization of two new 3,8″‐biflavonoid diastereoisomers, named GB‐4 ( 6a ) and GB‐4a ( 6b ). Their absolute configurations were determined in mixture by on‐line LC/CD measurements, which also allowed the revision of absolute configurations of the biflavanoids GB‐1 and GB‐2, and the configurational assignment of GB‐3. 相似文献
144.
145.
Xiao Qi ZHENG Yong Hui WANG Qing Xiang GUO* Li YANG You Cheng LIU Department of Chemistry University of Science Technology of China Hefei National Laboratory of Applied Organic Chemistry Lanzhou University Lanzhou 《中国化学快报》2003,(8)
As artificial enzymes, the binding constants of cyclodextrins (CDs) and their substrates are expected to be high1. For this purpose, many kinds of bridged cyclodextrin dimers2 whose two cyclodextrins are linked by various spacers have been constructed. It was of interest to make the dimers, whose binding constants would exceed 108dm3/mol3. Up to date, the bridged cyclodextrin dimers have been extensively studied as enzyme models and as molecular receptors4-6. Recently, we synthesized a brid… 相似文献
146.
147.
148.
Aiqing Zhang Xiangdan Li Changwoon Nah Keejun Hwang Myong‐Hoon Lee 《Journal of polymer science. Part A, Polymer chemistry》2003,41(1):22-29
A soluble aromatic polyimide was chloromethylated via a reaction with chloromethyl methyl ether in the presence of tin(IV) chloride to produce a new starting material for the modification of aromatic polyimides. The chemical structure of the resulting polymer was confirmed by 1H NMR and Fourier transform infrared spectroscopy. The maximum number of chloromethyl groups per repeat unit was 1.81. The chloromethylated polyimide was stable up to 250 °C and soluble in both chloroform and tetrahydrofuran. So that its utilization for further modification could be demonstrated, cinnamic acid was reacted with the formed polyimide, and it produced a new photosensitive polyimide with a cinnamoyl side chain. The photosensitivity of the resulting polyimide was investigated with ultraviolet spectroscopic methods. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 22–29, 2003 相似文献
149.
The goal of the paper is to analyse properties of solutions for linear thermoelastic systems of type III in one space variable. Our approach does not use energy methods, it bases on a special diagonalization procedure which is different in different parts of the phase space. This procedure allows to derive explicit representations of solutions. These representations help to prove results for well‐posedness of the Cauchy problem, LP–Lq decay estimates on the conjugate line and results for propagation of singularities. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
150.
The microstructure of CosoNi22Ga28 ribbon with the L10 structure is examined. The band-like morphology is observed. These bands with the width in a range of 40-200 nm appear along the transverse direction of the ribbon. The giant magnetoimpedance (GMI) effect in this alloy is measured. The results show that Co5oNi22Ga28 exhibits a sharp peak of the GAI effect. The maximum GAH ratio up to 360% is detected. The GMI effect measured versus temperature shows large jumps of the magnetoimpedance amplitude at the reversal martensitic transformation temperature 240℃ and Curie temperature 375℃C respectively. The jump ratios of the magnetoimpedance amplitude examined at these temperatures are about 5 and 10, respectively. 相似文献