全文获取类型
收费全文 | 3330篇 |
免费 | 68篇 |
国内免费 | 13篇 |
专业分类
化学 | 2126篇 |
晶体学 | 13篇 |
力学 | 43篇 |
数学 | 467篇 |
物理学 | 762篇 |
出版年
2021年 | 31篇 |
2020年 | 57篇 |
2019年 | 44篇 |
2018年 | 24篇 |
2016年 | 55篇 |
2015年 | 62篇 |
2014年 | 68篇 |
2013年 | 115篇 |
2012年 | 115篇 |
2011年 | 151篇 |
2010年 | 97篇 |
2009年 | 92篇 |
2008年 | 125篇 |
2007年 | 131篇 |
2006年 | 115篇 |
2005年 | 96篇 |
2004年 | 111篇 |
2003年 | 96篇 |
2002年 | 94篇 |
2001年 | 64篇 |
2000年 | 52篇 |
1999年 | 42篇 |
1998年 | 35篇 |
1997年 | 58篇 |
1996年 | 53篇 |
1995年 | 45篇 |
1994年 | 46篇 |
1993年 | 45篇 |
1992年 | 43篇 |
1991年 | 35篇 |
1990年 | 40篇 |
1989年 | 50篇 |
1988年 | 38篇 |
1987年 | 45篇 |
1986年 | 46篇 |
1985年 | 64篇 |
1984年 | 48篇 |
1983年 | 32篇 |
1982年 | 46篇 |
1981年 | 43篇 |
1980年 | 33篇 |
1979年 | 46篇 |
1978年 | 49篇 |
1977年 | 56篇 |
1976年 | 49篇 |
1975年 | 34篇 |
1974年 | 36篇 |
1973年 | 35篇 |
1972年 | 28篇 |
1970年 | 23篇 |
排序方式: 共有3411条查询结果,搜索用时 0 毫秒
61.
62.
63.
64.
Michael?Sch?ferlingEmail author Michael?Riepl Petra?Pavlickova Hubert?Paul Dev?Kambhampati Bo?Liedberg 《Mikrochimica acta》2003,142(4):193-203
Two different types of -substituted alkanethiol/disulfide compounds have been used to prepare monolayer architectures on gold serving as platforms for the immobilization of receptor probe molecules – antibodies. These are: (i) carboxylic acid alkanethiols post-reacted with amino biotin to generate streptavidin surfaces, and (ii) N-hydroxysuccinimide-terminated disulfide surfaces. The properties of the monolayers, with and without attached receptor probe molecules, were analysed using infrared spectroscopy, ellipsometry, fluorescence scanning and atomic force microscopy. Several experimental parameters, such as condensation reagents, additives, probe and target concentrations and immobilization time, were systematically varied to determine the dynamic range and to optimize the sensitivity and signal-to-noise ratio of the biochip platforms. Fluorescence screening using Cy5-labelled antigens finally demonstrated that both surfaces could be successfully employed to immobilize the antibodies. The pros and cons of the two approaches are also discussed.Received November 15, 2002; accepted March 25, 2003
Published online July 28, 2003 相似文献
65.
Hofmann C Boll R Heitmann B Hauser G Dürr C Frerich A Weitnauer G Glaser SJ Bechthold A 《Chemistry & biology》2005,12(10):1137-1143
The oligosaccharide antibiotic avilamycin A is composed of a polyketide-derived dichloroisoeverninic acid moiety attached to a heptasaccharide chain consisting of six hexoses and one unusual pentose moiety. We describe the generation of mutant strains of the avilamycin producer defective in different sugar biosynthetic genes. Inactivation of two genes (aviD and aviE2) resulted in the breakdown of the avilamycin biosynthesis. In contrast, avilamycin production was not influenced in an aviP mutant. Inactivation of aviGT4 resulted in a mutant that accumulated a novel avilamycin derivative lacking the terminal eurekanate residue. Finally, AviE2 was expressed in Escherichia coli and the gene product was characterized biochemically. AviE2 was shown to convert UDP-D-glucuronic acid to UDP-D-xylose, indicating that the pentose residue of avilamycin A is derived from D-glucose and not from D-ribose. Here we report a UDP-D-glucuronic acid decarboxylase in actinomycetes. 相似文献
66.
67.
Hubert TD Vue C Bernardy JA Van Horsen DL Rossulek MI 《Journal of AOAC International》2001,84(2):392-398
3-Trifluoromethyl-4-nitrophenol (TFM) is a pesticide used for the selective control of sea lampreys (Petromyzon marinus) in stream and river tributaries of the Great Lakes. To determine concentrations of TFM and TFM glucuronide in the edible fillet tissue of fish during sea lamprey control treatments, an analytical method was developed to determine the concentrations of these residues in rainbow trout (Oncorhynchus mykiss; RBT) and channel catfish (Ictalurus punctatis; CCF). Homogenized fillets were extracted with methanol-water (80 + 20). TFM and TFM glucuronide were isolated from coextractives by C18 solid-phase extraction. TFM glucuronide was hydrolyzed to TFM by the addition of beta-glucuronidase to the TFM glucuronide extract. The extracts were analyzed separately by liquid chromatography with UV-visible detection. Recoveries from TFM-fortified CCF and RBT tissues were 84.1 and 96.1%, respectively. The method detection limits (MDLs) are 2.4 ng/g for TFM-fortified tissues of CCF and 3 ng/g for those of RBT. Recoveries were 78.8 and 77% from TFM glucuronide-fortified CCF and RBT tissues, respectively. The MDLs for TFM glucuronide-fortified tissues are 3.5 and 6.9 ng/g for CCF and RBT, respectively. 相似文献
68.
Walther Lamprecht und Hubert Katzlmeier 《Fresenius' Journal of Analytical Chemistry》1961,181(1):216-229
Zusammenfassung An kristallisierten Enzymen des biologischen Stoffwechsel wird gezeigt, daß bei der Polarographie nur die schwefelhaltigen Proteine katalytische Wasserstoffwellen geben. Von den in der Literatur beschriebenen Doppelstufen der Proteine besitzt nur die im negativeren Potentialbereich liegende Welle die eigentliche katalytische Funktion. Die erste Vorwelle von Proteinen verschwindet, wenn die polarographische Messung bei 0° C durchgeführt wird.In Proteinen sind nur Disulfidgruppen katalytisch wirksam. Sogenannte reine Sulfhydryl-Enzyme haben keinen katalytischen Effekt. Typische SH-Enzyme können jedoch polarographisch als p-Chloromercuribenzoatkomplexe gemessen werden.Durch Harnstoffzusatz bei der polarographischen Messung von Proteinen gelingt es, zwischen maskierten und freien Sulfhydryl- oder Disulfidgruppen an Enzymen zu definieren.Auszug aus der Dissertationsschrift H. Katzlmeier, Technische Hochschule München (1959). 相似文献
69.
Sénéchal K Maury O Le Bozec H Ledoux I Zyss J 《Journal of the American Chemical Society》2002,124(17):4560-4561
Thermally stable dipolar and octupolar (D2d, D3) NLO-phores are readily accessible by combining one, two, or three 4,4'-bis(dialkylaminostyryl)-[2,2']-bipyridyl ligands with zinc(II) salts. The off-resonant beta0 values point out the superiority of octupoles versus dipoles in terms of nonlinearity/transparency tradeoff. The octahedral tris(bipyridyl)zinc(II) complex exhibits a very large beta0 value (241 x 10-30 esu), which is the largest ever reported for octupolar molecules. 相似文献
70.