全文获取类型
收费全文 | 750篇 |
免费 | 11篇 |
国内免费 | 10篇 |
专业分类
化学 | 436篇 |
晶体学 | 4篇 |
力学 | 15篇 |
数学 | 138篇 |
物理学 | 178篇 |
出版年
2020年 | 7篇 |
2019年 | 6篇 |
2017年 | 5篇 |
2016年 | 10篇 |
2014年 | 10篇 |
2013年 | 27篇 |
2012年 | 20篇 |
2011年 | 39篇 |
2010年 | 18篇 |
2009年 | 16篇 |
2008年 | 33篇 |
2007年 | 22篇 |
2006年 | 37篇 |
2005年 | 36篇 |
2004年 | 23篇 |
2003年 | 28篇 |
2002年 | 32篇 |
2001年 | 28篇 |
2000年 | 20篇 |
1999年 | 14篇 |
1998年 | 7篇 |
1997年 | 10篇 |
1996年 | 19篇 |
1995年 | 13篇 |
1994年 | 15篇 |
1993年 | 16篇 |
1992年 | 22篇 |
1991年 | 12篇 |
1990年 | 12篇 |
1989年 | 7篇 |
1988年 | 11篇 |
1987年 | 9篇 |
1986年 | 9篇 |
1985年 | 9篇 |
1984年 | 6篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1979年 | 6篇 |
1978年 | 5篇 |
1977年 | 8篇 |
1976年 | 6篇 |
1975年 | 10篇 |
1974年 | 9篇 |
1973年 | 11篇 |
1972年 | 6篇 |
1971年 | 7篇 |
1970年 | 11篇 |
1969年 | 5篇 |
1939年 | 5篇 |
排序方式: 共有771条查询结果,搜索用时 196 毫秒
71.
Heinrich Hart G. Hentschel Bauer H. Passow Jr und W. Hoffman 《Fresenius' Journal of Analytical Chemistry》1928,74(1-2):49-52
Ohne Zusammenfassung 相似文献
72.
Ohne Zusammenfassung 相似文献
73.
74.
75.
Darryn E. Bryant Saad El-Zanati Charles Vanden Eynden Dean G. Hoffman 《Graphs and Combinatorics》2001,17(1):55-59
Let S
k
denote the complete bipartite graph K
1,
k
and let Q
n
denote the n-cube. We prove that the obvious necessary conditions for the existence of an S
k
-decomposition of Q
n
are sufficient.
Received: July 21, 1999 Final version received: May 16, 2000 相似文献
76.
77.
78.
J. I. Hoffman 《Fresenius' Journal of Analytical Chemistry》1934,96(3-4):135-137
Ohne Zusammenfassung 相似文献
79.
Chuanlei Liu Kurt Ungar Dylan Pierce Ian Hoffman Weihua Zhang 《Journal of Radioanalytical and Nuclear Chemistry》2017,312(3):471-478
In assistance of radionuclide measurements at Canada’s Comprehensive Nuclear-Test-Ban Treaty (CTBT) laboratory, a Geant4 Monte Carlo application has been developed in simulating a broad-energy germanium detector and calculating detection efficiencies. The detector model was optimized in a reliable and non-biased manner through simultaneous tuning on gap distance and detector dimension, and was validated over various realistic measurement scenarios. All work is based on a series of experiments which covers the typical energy range of gamma radiation in environmental analysis, and considers the variety of the CTBT sample type, dimension and distance-to-detector. In all cases, the predicted efficiencies are consistent with the empirical ones within 5%, with a typical deviation of 3% in majority. 相似文献
80.
Davydov R Osborne RL Shanmugam M Du J Dawson JH Hoffman BM 《Journal of the American Chemical Society》2010,132(42):14995-15004
Dehaloperoxidase (DHP) from Amphitrite ornata is a heme protein that can function both as a hemoglobin and as a peroxidase. This report describes the use of 77 K cryoreduction EPR/ENDOR techniques to study both functions of DHP. Cryoreduced oxyferrous [Fe(II)-O(2)] DHP exhibits two EPR signals characteristic of a peroxoferric [Fe(III)-O(2)(2-)] heme species, reflecting the presence of conformational substates in the oxyferrous precursor. (1)H ENDOR spectroscopy of the cryogenerated substates shows that H-bonding interactions between His N(ε)H and heme-bound O(2) in these conformers are similar to those in the β-chain of oxyferrous hemoglobin A (HbA) and oxyferrous myoglobin, respectively. Decay of cryogenerated peroxoferric heme DHP intermediates upon annealing at temperatures above 180 K is accompanied by the appearance of a new paramagnetic species with an axial EPR signal with g(⊥) = 3.75 and g(∥) = 1.96, characteristic of an S = 3/2 spin state. This species is assigned to Compound I (Cpd I), in which a porphyrin π-cation radical is ferromagnetically coupled with an S = 1 ferryl [Fe(IV)═O] ion. This species was also trapped by rapid freeze-quench of the ambient-temperature reaction mixture of ferric [Fe(III)] DHP and H(2)O(2). However, in the latter case Cpd I is reduced very rapidly by a nearby tyrosine to form Cpd ES [(Fe(IV)═O)(porphyrin)/Tyr(?)]. Addition of the substrate analogue 2,4,6-trifluorophenol (F(3)PhOH) suppresses formation of the Cpd I intermediate during annealing of cryoreduced oxyferrous DHP at 190 K but has no effect on the spectroscopic properties of the remaining cryoreduced oxyferrous DHP intermediates and kinetics of their decay. These observations indicate that substrate (i) binds to oxyferrous DHP outside of the distal pocket and (ii) can reduce Cpd I to Cpd II [Fe(IV)═O]. These assumptions are also supported by the observation that F(3)PhOH has only a small effect on the EPR properties of radiolytically cryooxidized and cryoreduced ferrous [Fe(II)] DHP. EPR spectra of cryoreduced ferrous DHP disclose the multiconformational nature of the ferrous DHP precursor. The observation and characterization of Cpds I, II, and ES in the absence and in the presence of F(3)PhOH provides definitive evidence of a mechanism involving consecutive one-electron steps and clarifies the role of all intermediates formed during turnover. 相似文献