全文获取类型
收费全文 | 325827篇 |
免费 | 3462篇 |
国内免费 | 932篇 |
专业分类
化学 | 162426篇 |
晶体学 | 4325篇 |
力学 | 15437篇 |
综合类 | 8篇 |
数学 | 38392篇 |
物理学 | 109633篇 |
出版年
2021年 | 3032篇 |
2020年 | 3331篇 |
2019年 | 3762篇 |
2018年 | 5199篇 |
2017年 | 5440篇 |
2016年 | 7368篇 |
2015年 | 4141篇 |
2014年 | 7032篇 |
2013年 | 15909篇 |
2012年 | 12381篇 |
2011年 | 14832篇 |
2010年 | 11019篇 |
2009年 | 10920篇 |
2008年 | 13236篇 |
2007年 | 13198篇 |
2006年 | 12139篇 |
2005年 | 10527篇 |
2004年 | 9835篇 |
2003年 | 8687篇 |
2002年 | 8674篇 |
2001年 | 10398篇 |
2000年 | 7625篇 |
1999年 | 5574篇 |
1998年 | 4642篇 |
1997年 | 4514篇 |
1996年 | 4161篇 |
1995年 | 3751篇 |
1994年 | 3727篇 |
1993年 | 3605篇 |
1992年 | 4005篇 |
1991年 | 4221篇 |
1990年 | 3998篇 |
1989年 | 3904篇 |
1988年 | 3691篇 |
1987年 | 3848篇 |
1986年 | 3613篇 |
1985年 | 4561篇 |
1984年 | 4624篇 |
1983年 | 3828篇 |
1982年 | 3907篇 |
1981年 | 3642篇 |
1980年 | 3591篇 |
1979年 | 3878篇 |
1978年 | 3862篇 |
1977年 | 3881篇 |
1976年 | 3862篇 |
1975年 | 3639篇 |
1974年 | 3591篇 |
1973年 | 3623篇 |
1972年 | 2583篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
61.
Eid Eldesouki I. Khalaf-Allah Reda A. Albadry Asmaa I. Easa Ammar S. 《Journal of Thermal Analysis and Calorimetry》2022,147(13):7523-7538
Journal of Thermal Analysis and Calorimetry - The Stirling cycle is regarded as one alternative to the compressive cooling cycle. The current study examines the performance of a beta Stirling... 相似文献
62.
Russian Chemical Bulletin - New representatives of (O-Si)-chelate compounds, N-(fluorosilyl)methyl derivatives of N-methylacetamide, N-methylbenzamide, N-phenylacetamide, and N-phenylbenzamide,... 相似文献
63.
Sakhautdinova G. F. Sakhautdinov I. M. Mustafin A. G. Yunusov M. S. 《Chemistry of Natural Compounds》2022,58(1):185-186
Chemistry of Natural Compounds - 相似文献
64.
Automotive proton exchange membrane fuel cell stacks need to meet manufacturer specified rated beginning-of-life (BOL) performance before being assembled into vehicles and shipped off to customers. The process of “breaking-in” of a freshly assembled stack is often referred to as “conditioning.” It has become an intensely researched area especially in automotive companies, where imminent commercialization of fuel cell electric vehicles (FCEVs) demands a short, energy- and cost-efficient, and practical conditioning protocol. Significant advances in reducing the conditioning time from 1 to 2 days to as low as 4h or less, in some cases without the use of additional inert gases such as nitrogen, and with minimal use of hydrogen, and specialized test stations will be discussed. 相似文献
65.
Chromatographia - We developed a simple, rapid, ecological RP-HPLC method for the estimation of Pitavastatin (PIT), Fenofibrate (FEN), and their impurities in a novel fixed dose combination. We... 相似文献
66.
Chumakov Yu. M. Graur V. O. Ulchina Ya. I. Smaglii V. A. Gulea A. P. Garbuz O. S. Tsapkov V. I. 《Journal of Structural Chemistry》2022,63(6):905-913
Journal of Structural Chemistry - The crystal structures and biological properties of [N′-(2-oxidobenzylidene)-N-(prop-2-en-1-yl)-carbamohydrazonothioato(2-)](1,10-phenanthroline)copper... 相似文献
67.
Chuprin A. S. Belova S. A. Bugaenko M. G. Vologzhanina A. V. Loktev A. S. Voloshin Ya. Z. Buznik V. M. Dedov A. G. 《Kinetics and Catalysis》2022,63(1):108-116
Kinetics and Catalysis - A new ruthenium(II) cage complex with polar terminal groups in the apical substituents has been synthesized; the molecular design of the complex contributes to the... 相似文献
68.
Nikita M. Ankudinov Prof. Dr. Yulia V. Nelyubina Prof. Dr. Dmitry S. Perekalin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(18):e202200195
Diene rhodium complexes are important catalysts in modern organic synthesis. Herein, we report a new approach to such complexes with the uncommon planar chirality. The synthesis is achieved by face-selective coordination of the prochiral 2,5-disubstituted-1,4-benzoquinones (R2-Q) with rhodium precursors containing the chiral auxiliary ligand S-salicyl-oxazoline (S-Salox). Such coordination leads to the formation of (R,R-R2-Q)Rh(S-Salox) complexes in high yields and with exceptional diastereoselectivity (d. r.>20 : 1). Subsequent replacement of the auxiliary ligand provides various benzoquinone rhodium complexes with retention of the planar chirality. Combined theoretical and experimental studies show that due to their electron-withdrawing nature benzoquinones bind metals stronger than the related 1,4-cyclohexadiene, but weaker than other common diene ligands, such as cyclooctadiene. 相似文献
69.
Mohammad A. Khalilzadeh Soo Young Kim Ho Won Jang Rafael Luque Rajender S. Varma Richard A. Venditti Mohammadreza Shokouhimehr 《Materials Today Chemistry》2022
The requirement of green and sustainable materials to prepare heterogeneous catalysts has intensified for practical reasons over the past few decades. Carbohydrates are possibly the most plentiful and renewable organic materials in nature with inimitable physiochemical properties, plausible low-cost and large-scale production, and sustainability features could be exploited in the generation of nanostructured heterogeneous catalysts. This review article outlines the organic transformations catalyzed by diverse carbohydrate-based nanostructured catalysts in greener and environmentally friendly processes. Selected examples are highlighted for a variety of organic reactions exploiting the proposed catalysts’ reactivity and reusability, and interactions with the intrinsic nature of the applied carbohydrate supports; advantages and speculated challenges of the introduced catalysts are deliberated as well. 相似文献
70.
Optics and Spectroscopy - The quantum yield of interconversion to triplet states for free-base 2,3,7,8,12,13,17,18-octaethylporphyrin and 5,10,15,20-tetraphenylporphyrin, as well as of... 相似文献