全文获取类型
收费全文 | 226篇 |
免费 | 2篇 |
国内免费 | 3篇 |
专业分类
化学 | 136篇 |
晶体学 | 3篇 |
力学 | 6篇 |
数学 | 47篇 |
物理学 | 39篇 |
出版年
2024年 | 2篇 |
2022年 | 2篇 |
2021年 | 2篇 |
2019年 | 2篇 |
2018年 | 6篇 |
2017年 | 2篇 |
2016年 | 10篇 |
2015年 | 2篇 |
2014年 | 2篇 |
2013年 | 11篇 |
2012年 | 10篇 |
2011年 | 11篇 |
2010年 | 9篇 |
2009年 | 4篇 |
2008年 | 5篇 |
2007年 | 8篇 |
2006年 | 13篇 |
2005年 | 10篇 |
2004年 | 11篇 |
2003年 | 8篇 |
2002年 | 15篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 3篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 3篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 7篇 |
1988年 | 5篇 |
1987年 | 11篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 4篇 |
1973年 | 2篇 |
1969年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有231条查询结果,搜索用时 0 毫秒
101.
102.
Yang TC Maeser NK Laryukhin M Lee HI Dean DR Seefeldt LC Hoffman BM 《Journal of the American Chemical Society》2005,127(37):12804-12805
X-ray crystallographic study of the nitrogenase MoFe protein revealed electron density from an atom (denoted X) inside the active-site metal cluster, the [MoFe7S9:homocitrate] FeMo-cofactor. The electron density associated with X is consistent with a single N, O, or C atom. We now have tested whether X is an N or not by comparing the Q-band ENDOR and ESEEM signals from resting-state (S = 3/2) MoFe protein and NMF-extracted FeMo-co from bacteria grown with either 14N or 15N as the exclusive N source. All of the 14N or 15N signals associated with the protein are lost upon extraction of the FeMo-co. We interpret this as strong evidence that X is not an N. 相似文献
103.
Barney BM Yang TC Igarashi RY Dos Santos PC Laryukhin M Lee HI Hoffman BM Dean DR Seefeldt LC 《Journal of the American Chemical Society》2005,127(43):14960-14961
A high population intermediate has been trapped on the nitrogenase active site FeMo cofactor during reduction of N2. In addition, intermediates have been trapped during reduction of CH3-N=NH by the alpha-195Gln variant and during reduction of H2N-NH2 by the alpha-70Ala/alpha-195Gln variant. Each of these trapped states shows an EPR signal arising from an S = 1/2 state of the FeMo cofactor. 15N ENDOR shows that each intermediate has a nitrogenous species bound to the FeMo cofactor, with a single type of N seen for each bound intermediate. The g tensors are unique to each intermediate, g(e) = [2.084, 1.993, 1.969], g(m) = [2.083, 2.021, 1.993], g(l) = [2.082, 2.015, 1.987], as are the 15N hyperfine couplings at g1, which suggests that three distinct stages of NN reduction may have been trapped. The 1H ENDOR spectra show that the N2 intermediate is at a distinct and earlier stage of reduction from the other two, so at least two stages of NN reduction have been trapped. Some possible structures of the hydrazine intermediate are presented. 相似文献
104.
High-speed analysis of multiplexed short tandem repeats with an electrophoretic microdevice 总被引:3,自引:0,他引:3
Mitnik L Carey L Burger R Desmarais S Koutny L Wernet O Matsudaira P Ehrlich D 《Electrophoresis》2002,23(5):719-726
We report the development of a robust and effective method for multiplexed short tandem repeat (STR) analysis within a chip-based microdevice. The method uses a laser-induced fluorescence detection system and simultaneously detects three- and four-color multiplexed polymerase chain reaction (PCR) samples. Analyses of the eight combined DNA index system (CODIS) STR loci were performed in 20 min with single-base-pair resolution ranging from 0.75 to 1. A simultaneous analysis of fifteen loci-ladders and a gender marker Amelogenin based on the PowerPlexTM 16 System was achieved in less than 35 min. The system is capable of repetitive operation and may be extended to high-throughput multilane devices that could be readily interfaced to an automated sample loading system. 相似文献
105.
We establish some stability theorems for Feynman’s operational calculus in the setting where the time-ordering measures are allowed to have both continuous and discrete parts. In particular, we investigate stability in a number of special cases of this blended approach to the operational calculus.Mathematics Subject Classifications (2000) Primary: 46J15, 47A56, 47A60, 60B10; secondary: 46N50, 47N50. 相似文献
106.
107.
108.
Given a numerical semigroup S=〈a 0,a 1,a 2,…,a t 〉 and n∈S, we consider the factorization n=c 0 a 0+c 1 a 1+?+c t a t where c i ≥0. Such a factorization is maximal if ∑c i is a maximum over all such factorizations of n. We provide an algorithm for computing the maximum number of maximal factorizations possible for an element in S, which is called the maximal denumerant of S. We also consider various cases that have connections to the Cohen-Macualay and Gorenstein properties of associated graded rings for which this algorithm simplifies. 相似文献
109.
We examined the effect of the oxygenation level on efficacy of two photosensitizing agents, both of which target lysosomes for photodamage, but via different photochemical pathways. Upon irradiation, the chlorin termed NPe6 forms singlet oxygen in high yield while the bacteriopheophorbide WST11 forms only oxygen radicals (in an aqueous environment). Photokilling efficacy by WST11 in cell culture was impaired when the atmospheric oxygen concentration was reduced from 20% to 1%, while photokilling by NPe6 was unaffected. Studies in a cell‐free system revealed that the rates of photobleaching of these agents, as a function of the oxygenation level, were correlated with results described above. Moreover, the rate of formation of oxygen radicals by either agent was more sensitive to the level of oxygenation than was singlet oxygen formation by NPe6. These data indicate that the photochemical process that leads to oxygen radical formation is more dependent on the oxygenation level than is the pathway leading to formation of singlet oxygen. 相似文献
110.