全文获取类型
收费全文 | 252篇 |
免费 | 16篇 |
专业分类
化学 | 188篇 |
晶体学 | 3篇 |
力学 | 4篇 |
数学 | 7篇 |
物理学 | 56篇 |
无线电 | 10篇 |
出版年
2022年 | 6篇 |
2021年 | 5篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 4篇 |
2016年 | 10篇 |
2015年 | 7篇 |
2014年 | 7篇 |
2013年 | 7篇 |
2012年 | 9篇 |
2011年 | 11篇 |
2010年 | 3篇 |
2009年 | 9篇 |
2008年 | 7篇 |
2007年 | 13篇 |
2006年 | 7篇 |
2005年 | 14篇 |
2004年 | 9篇 |
2003年 | 11篇 |
2002年 | 20篇 |
2001年 | 11篇 |
2000年 | 5篇 |
1999年 | 1篇 |
1998年 | 8篇 |
1997年 | 5篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 6篇 |
1993年 | 2篇 |
1991年 | 2篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 8篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1972年 | 3篇 |
1971年 | 2篇 |
1970年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有268条查询结果,搜索用时 15 毫秒
71.
A 3D display equipped with a linearly moving mirror reflecting a series of 2D cross sections pictures has been devised. The pictures were displayed by a CRT in perfect synchronization with the back-and-forth movements of the mirror. The 80x80x80 mm(3) 3D space contained 128x128 pixels; with each pixel having 256 grades of intensity, enough to produce a satisfactory 3D image of an ultrasonic echogram of hepatic vessels. The images can be observed from different angles by changing the observer's position or by prompt rotation of the image through a console. Mechanical problems inherent in using moving parts have been solved. 相似文献
72.
We evaluated the activation and inhibition effects of phosphatidylcholine (PC) and sphingomyelin (SM) on lipoprotein lipase
(LPL) for medium or long chain-triglycerides (TG) in monolayers at the air/water interface. Monolayers of medium chain-TG,
being in an expanded state at a surface pressure of 15 mN/m, showed low susceptibility to LPL in the subphase. Adding 50 mole%
of PC or SM into these monolayers reduced the partial molecular area of the TG and enhanced the LPL activity. Monolayers of
long chain-TG, being in a condensed state, showed high susceptibility of LPL either with or without PC. SM added to the long
chain-TG monolayers, however, inhibited the LPL action. We investigated the interaction between TG and phospholipid on the
basis of the collapse pressure-measurements of mixed monolayers. For medium chain-TG monolayers, PC and SM gave similar collapse
pressure-composition profiles. Contrary to this, SM gave a markedly higher collapse pressure of long chain-TG than PC: SM
stabilized the monolayer state of long chain-TG. These results suggested that I) orientation of the acyl chains of TG molecule
in a monolayer is crucial for the LPL activity, and that II) strong interaction between SM and long chain-TG retards the substrate-transfer
from the mixed monolayer to the catalytic pocket of LPL.
Received: 6 March 1996 Accepted: 19 July 1996 相似文献
73.
Sunazuka T Handa M Nagai K Shirahata T Harigaya Y Otoguro K Kuwajima I Omura S 《Organic letters》2002,4(3):367-369
The first convergent total synthesis of (+/-)-arisugacin A was accomplished by stereoselective construction of the arisugacin skeleton via a Knoevenagel-type reaction of an alpha,beta-unsaturated aldehyde with a 4-hydroxy 2-pyrone and stereoselective dihydroxylation followed by deoxygenation. 相似文献
74.
Sachin Handa James C. Fennewald Bruce H. Lipshutz 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(13):3500-3503
On the basis of the far higher solubility of oxygen gas inside the hydrocarbon core of nanomicelles, metal and peroxide free aerobic oxidation of aryl alkynes to β‐ketosulfones has been achieved in water at room temperature. Many examples are offered that illustrate broad functional group tolerance. The overall process is environmentally friendly, documented by the associated low E Factors. 相似文献
75.
76.
77.
Optical Review - We investigated the relationship between the refractive index of intraocular lenses and optical phenomena such as leading dysphotopsia. A modified Liou–Brennan model... 相似文献
78.
A series of differently substituted Chugaev‐type palladium bis(acyclic diaminocarbene) complexes was screened to identify the most active catalyst for Mizoroki–Heck coupling reactions of aryl bromides with styrene. The best catalyst, which contains three methyl groups on the bis(carbene) ligand, gives excellent coupling yields at 120 °C for both activated and deactivated aryl bromides. However, activity with aryl chlorides is limited to electron‐deficient examples. The optimized catalyst demonstrates limited air and moisture stability, giving reduced yields in couplings of activated aryl bromides in open‐flask conditions. The modular synthesis of this class of catalysts should allow further fine‐tuning of activity in Mizoroki–Heck and related coupling reactions. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
79.
80.
Satoshi Sakamoto Yasuaki Kabe Mamoru Hatakeyama Yuki Yamaguchi Hiroshi Handa 《Chemical record (New York, N.Y.)》2009,9(1):66-85
In drug development research, the elucidation and understanding of the interactions between physiologically active substances and proteins that numerous genes produce is important. Currently, most commercially available drugs and physiologically active substances have been brought to market without knowledge of factors interacting with the drugs and the substances. Affinity purification is a useful and powerful technique employed to understand factors that are targeted by drugs and physiologically active substances. However, use of conventional matrices for affinity chromatography often causes a decrease in efficiency of affinity purification and, as a result, more practical matrices for affinity purification have been developed for application in drug discovery research. In this paper, we describe the development of high‐performance affinity beads (SG beads and FG beads) that enable one‐step affinity purification of drug targets and the elucidation of the mechanism of the action of the drugs. We also describe a chemical screening system using our affinity beads. We hope that utilization of the affinity beads will contribute to the progress of research in chemical biology. © 2009 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 9: 66–85; 2009: Published online in Wiley InterScience ( www.interscience.wiley.com ) DOI 10.1002/tcr.20170 相似文献