全文获取类型
收费全文 | 1406篇 |
免费 | 26篇 |
专业分类
化学 | 1224篇 |
晶体学 | 9篇 |
力学 | 4篇 |
数学 | 30篇 |
物理学 | 165篇 |
出版年
2020年 | 8篇 |
2016年 | 9篇 |
2015年 | 15篇 |
2014年 | 18篇 |
2013年 | 22篇 |
2012年 | 25篇 |
2011年 | 26篇 |
2010年 | 16篇 |
2009年 | 14篇 |
2008年 | 43篇 |
2007年 | 26篇 |
2006年 | 31篇 |
2005年 | 24篇 |
2004年 | 20篇 |
2003年 | 10篇 |
2002年 | 8篇 |
2001年 | 13篇 |
2000年 | 10篇 |
1997年 | 9篇 |
1996年 | 12篇 |
1995年 | 10篇 |
1994年 | 13篇 |
1993年 | 20篇 |
1991年 | 13篇 |
1989年 | 16篇 |
1987年 | 11篇 |
1984年 | 10篇 |
1983年 | 10篇 |
1978年 | 14篇 |
1977年 | 10篇 |
1976年 | 9篇 |
1975年 | 7篇 |
1974年 | 8篇 |
1969年 | 10篇 |
1968年 | 31篇 |
1967年 | 59篇 |
1966年 | 72篇 |
1965年 | 64篇 |
1964年 | 57篇 |
1963年 | 33篇 |
1962年 | 48篇 |
1961年 | 12篇 |
1960年 | 27篇 |
1959年 | 27篇 |
1958年 | 17篇 |
1957年 | 20篇 |
1956年 | 69篇 |
1955年 | 135篇 |
1954年 | 81篇 |
1920年 | 7篇 |
排序方式: 共有1432条查询结果,搜索用时 234 毫秒
61.
Starch and its analogue glycogen are biosynthesized by enzymes that have been classified by sequence similarities into two families that have no significant sequence overlap: the animal/fungal glycogen synthases and the plant/bacterial glycogen (starch) synthases. Recent gene sequence analysis of putative archaea enzymes implicates them as a third family that links the structural and functional features of the other two classes. Herein, we present the first rapid electrospray ionization mass spectrometry-based assay to quantify any carbohydrate-polymerizing activity, the first cloning and recombinant expression as well as verification of the putative function of a glycogen synthase from the hyperthermophilic archaea Pyrococcus furiosus, and the characterization of a variety of glycogen synthases with the new assay. The new assay allowed the determination of Km and Vmax values for the rabbit, yeast, and P. furiosus glycogen synthases. Most surprisingly, unlike the synthases from rabbit or yeast and in contradiction to what would be expected from structural studies of other nucleotide-sugar binding proteins, the synthase from the archaea source accepts both uridine- and adenine-diphosphate activated glucose competitively and with comparable affinities to form a glucose polymer. This loose substrate specificity implicates this protein as the chemical link between the two branches of glycogen synthases that have evolved to accept primarily one or the other nucleotide as well as a good source enzyme for polymer bioengineering efforts. 相似文献
62.
[reaction: see text] Addition of isopropyl-beta-d-thiogalactopyranoside (IPTG) to bacterial cultures is often used to induce expression of plasmid-based genes for the production of recombinant proteins under control of the lac promoter, but a simple method to circumvent the inherent instability of this compound has not been addressed experimentally. Herein we report the first synthesis of isobutyl-C-galactoside (IBCG), the C-glycoside analogue of IPTG, and show that IBCG is superior to IPTG in inducing protein expression over long induction times. 相似文献
63.
de La Figuera J Pohl K de La Fuente OR Schmid AK Bartelt NC Carter CB Hwang RQ 《Physical review letters》2001,86(17):3819-3822
Using scanning tunneling microscopy we have observed thermally induced dislocation glide in monolayer Cu films on Ru(0001) at room temperature. The motion is governed by a Peierls barrier that depends on the detailed structure of the dislocations, in particular upon whether the threading dislocations that terminate them are dissociated or not. Calculations based on the Frenkel-Kontorova model reproduce the threading dislocation structure and provide estimates of the Peierls barrier and dislocation stiffness which are consistent with experiment. 相似文献
64.
Ohne Zusammenfassung
Memorie della r. Accademia di Bologna ser 5. T. VIII, p. 131–186. Die Abschnitte I und II s. M.-H. S. 54 ff. 相似文献
C. Arzelàs Abhandlung: Sulle serie di funzioni, parte prima
Memorie della r. Accademia di Bologna ser 5. T. VIII, p. 131–186. Die Abschnitte I und II s. M.-H. S. 54 ff. 相似文献
65.
66.
67.
68.
69.
70.