全文获取类型
收费全文 | 26094篇 |
免费 | 596篇 |
国内免费 | 160篇 |
专业分类
化学 | 17523篇 |
晶体学 | 214篇 |
力学 | 656篇 |
综合类 | 1篇 |
数学 | 4403篇 |
物理学 | 4053篇 |
出版年
2021年 | 177篇 |
2020年 | 213篇 |
2019年 | 284篇 |
2018年 | 232篇 |
2017年 | 207篇 |
2016年 | 444篇 |
2015年 | 344篇 |
2014年 | 455篇 |
2013年 | 1322篇 |
2012年 | 1191篇 |
2011年 | 1508篇 |
2010年 | 780篇 |
2009年 | 624篇 |
2008年 | 1365篇 |
2007年 | 1417篇 |
2006年 | 1411篇 |
2005年 | 1411篇 |
2004年 | 1240篇 |
2003年 | 1042篇 |
2002年 | 1017篇 |
2001年 | 374篇 |
2000年 | 297篇 |
1999年 | 244篇 |
1998年 | 285篇 |
1997年 | 312篇 |
1996年 | 395篇 |
1995年 | 298篇 |
1994年 | 282篇 |
1993年 | 287篇 |
1992年 | 273篇 |
1991年 | 238篇 |
1990年 | 224篇 |
1989年 | 240篇 |
1988年 | 268篇 |
1987年 | 251篇 |
1986年 | 248篇 |
1985年 | 388篇 |
1984年 | 436篇 |
1983年 | 322篇 |
1982年 | 427篇 |
1981年 | 402篇 |
1980年 | 341篇 |
1979年 | 331篇 |
1978年 | 347篇 |
1977年 | 331篇 |
1976年 | 274篇 |
1975年 | 270篇 |
1974年 | 261篇 |
1973年 | 239篇 |
1972年 | 143篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Discovery,Characterization, and Analogue Synthesis of Bohemamine Dimers Generated by Non‐enzymatic Biosynthesis 下载免费PDF全文
Dr. Peng Fu Aaron Legako Scott La Prof. Dr. John B. MacMillan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(10):3491-3495
Dibohemamines A–C ( 5 – 7 ), three new dimeric bohemamine analogues dimerized through a methylene group, were isolated from a marine‐derived Streptomyces spinoverrucosus. The structures determined by spectroscopic analysis were confirmed through the semi‐synthetic derivatization of monomeric bohemamines and formaldehyde. These reactions, which could occur under mild conditions, together with the detection of formaldehyde in the culture, revealed that this dimerization is a non‐enzymatic process. In addition to the unique dimerization of the dibohemamines, dibohemamines B and C were found to have nm cytotoxicity against the non‐small cell‐lung cancer cell line A549. In view of the potent cytotoxicity of compounds 6 and 7 , a small library of bohemamine analogues was generated for biological evaluation by utilizing a series of aryl and alkyl aldehydes. 相似文献
992.
993.
Meng Liu Wenqing Zhang Qiang Zhang John D. Brennan Yingfu Li 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(33):9773-9777
ϕ29 DNA polymerase (ϕ29DP) is able to carry out repetitive rounds of DNA synthesis using a circular DNA template by rolling circle amplification (RCA). It also has the ability to execute 3′–5′ digestion of single‐stranded but not double‐stranded DNA. A biosensor engineering strategy is presented that takes advantage of these two properties of ϕ29DP coupled with structure‐switching DNA aptamers. The design employs a DNA assembly made of a circular DNA template, a DNA aptamer, and a pre‐primer. The DNA assembly is unable to undergo RCA in the absence of cognate target owing to the formation of duplex structures. The presence of the target, however, triggers a structure‐switching event that causes nucleolytic conversion of the pre‐primer by ϕ29DP into a mature primer to facilitate RCA. This method relays target detection by the aptamer to the production of massive DNA amplicons, giving rise to dramatically enhanced detection sensitivity. 相似文献
994.
995.
996.
997.
998.
999.
1000.
Róbert Bordás Volker John Ellen Schmeyer Dominique Thévenin 《Theoretical and Computational Fluid Dynamics》2013,27(3-4):253-271
The droplet size distribution in a turbulent flow field is considered and modeled by means of a population balance system. This paper studies different numerical methods for the 4D population balance equation and their impact on an output of interest, the time-space-averaged droplet size distribution at the outlet, which is known from experiments. These methods include different interpolations of the experimental data at the inlet, various discretizations in time and space, and different schemes for computing the coalescence integrals. It will be shown that noticeable changes in the output of interest might occur. In addition, the computational efficiency of the studied methods is discussed. 相似文献