全文获取类型
收费全文 | 513603篇 |
免费 | 21836篇 |
国内免费 | 10242篇 |
专业分类
化学 | 287919篇 |
晶体学 | 6139篇 |
力学 | 24165篇 |
综合类 | 525篇 |
数学 | 59800篇 |
物理学 | 167133篇 |
出版年
2022年 | 3762篇 |
2021年 | 6521篇 |
2020年 | 7968篇 |
2019年 | 7893篇 |
2018年 | 8875篇 |
2017年 | 8453篇 |
2016年 | 13144篇 |
2015年 | 9597篇 |
2014年 | 13514篇 |
2013年 | 26571篇 |
2012年 | 23443篇 |
2011年 | 27370篇 |
2010年 | 18879篇 |
2009年 | 18554篇 |
2008年 | 23211篇 |
2007年 | 22404篇 |
2006年 | 20780篇 |
2005年 | 18179篇 |
2004年 | 16323篇 |
2003年 | 14081篇 |
2002年 | 13739篇 |
2001年 | 15112篇 |
2000年 | 11604篇 |
1999年 | 9323篇 |
1998年 | 7486篇 |
1997年 | 7361篇 |
1996年 | 7080篇 |
1995年 | 6589篇 |
1994年 | 6378篇 |
1993年 | 6026篇 |
1992年 | 6521篇 |
1991年 | 6547篇 |
1990年 | 6177篇 |
1989年 | 5843篇 |
1988年 | 5740篇 |
1987年 | 5586篇 |
1986年 | 5289篇 |
1985年 | 6731篇 |
1984年 | 6751篇 |
1983年 | 5341篇 |
1982年 | 5416篇 |
1981年 | 5356篇 |
1980年 | 4915篇 |
1979年 | 5313篇 |
1978年 | 5439篇 |
1977年 | 5346篇 |
1976年 | 5295篇 |
1975年 | 4877篇 |
1974年 | 4847篇 |
1973年 | 4848篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
Kobayashi M. Zhang Y. Ishikawa H. Sun J. Oddershede J. Juul Jensen D. Miura H. 《Experimental Mechanics》2021,61(5):817-828
Experimental Mechanics - The internal strain distribution developing during plastic deformation is important for understanding the mechanical properties of polycrystalline materials. Such... 相似文献
42.
Jiraya Kiriratnikom Xun Zhang Xiaohan Cao Bo Chu Chengjian Zhang Xinghong Zhang 《Journal of polymer science. Part A, Polymer chemistry》2022,60(15):2262-2268
Facile construction of sulfur-rich polymers using readily available raw chemicals is an area aggressively pursued but challenging. Herein we use common feedstocks of ethylene oxide (EO), propylene oxide (PO), and carbonyl sulfide (COS) to synthesize copoly(thioether)s which are traditionally produced from unpleasant and difficult to store episulfides. In this protocol, the EO/COS coupling selectively generates a pure poly(ethylene sulfide) (PES) with melting temperature (Tm) values up to 172°C and high yields up to 98%. The EO/PO/COS terpolymerization leads to the incorporation of soft poly(propylene sulfide) (PPS) and hard PES segments together, affording a random PES-co-PPS copoly(thioether) with the complete consumption of EO and PO. Additionally, by simply varying the EO/PO feeding ratio, the obtained copoly(thioether)s possess tunable thermal properties, Tm values in the range of 76–144°C, and excellent solubility. These copolymerizations are conducted in one-pot/one-step at industrially favored reaction temperatures of 100–120°C using catalysts of common organic bases, suggesting a facile and practical manner. Especially, the copoly(thioether) exhibits high refractive indices up to 1.68 owing to its high sulfur content, suggesting a broad application prospect in optical materials. 相似文献
43.
Kopytov G. F. Malyshko V. V. Goryachko A. I. Sharafan M. V. Churkina A. V. Moiseev A. V. Shashkov D. I. Lyasota O. M. 《Russian Physics Journal》2021,64(2):255-260
Russian Physics Journal - The specific features of the sorption activity of silver nanoparticles (AgNPs) on biodegradable polymers of natural (collagen) and artificial (polyamide 6.6) origin have... 相似文献
44.
Kuz’mina L. G. Navasardyan M. A. Kalle P. Bezzubov S. I. 《Crystallography Reports》2021,66(3):420-423
Crystallography Reports - The crystal and molecular structures of Cl–C6H4–O–C16H33 (I) have been studied, and its differential scanning calorimetry (DSC) study is performed.... 相似文献
45.
Chromatographia - The present work deals with the optimization, validation and application of a versatile HPLC–DAD method for concurrent estimation of nine antimicrobials and proton pump... 相似文献
46.
Polyakov K. M. Mordkovich N. N. Safonova T. N. Antipov A. N. Okorokova N. A. Dorovatovskii P. V. Veiko V. P. 《Crystallography Reports》2021,66(5):786-790
Crystallography Reports - Crystals of mutants of uridine phosphorylase from Shewanella oneidensis MR-1 at the active-site threonine residue were obtained, and the three-dimensional structures of... 相似文献
47.
Reza Kordnezhadian Bing-Yu Li Armir Zogu Dr. Joachim Demaerel Prof. Dr. Wim M. De Borggraeve Dr. Ermal Ismalaj 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(60):e202201491
Pentafluorosulfanyl (SF5)-containing compounds and corresponding analogs are a highly valuable class of fluorine-containing building blocks owing to their unique properties. The reason for that is the set of peculiar and tremendously beneficial characteristics they can impart on molecules once introduced onto them. Despite this, their application in distinct scientific fields remains modest, given the extremely harsh reaction conditions needed to access such compounds. The recent synthetic approaches via S−F, and C−SF5 bond formation as well as the use of SF5-containing building blocks embody a “stairway-to-heaven” loophole in the synthesis of otherwise-inaccessible chemical scaffolds only a few years ago. Herein, we report and evaluate the properties of the SF5 group and analogs, by summarizing synthetic methodologies available to access them as well as following applications in material science and medicinal chemistry since 2015. 相似文献
48.
Doklady Mathematics - The integrability of certain classes of homogeneous dynamical systems on the tangent bundles of four-dimensional manifolds is shown. The force fields involved in the systems... 相似文献
49.
50.
Physics of Atomic Nuclei - Emission of short electron bunches with high charge in RF guns is considered. The emission mechanism in the case of picosecond laser pulses and the presence of a strong... 相似文献