全文获取类型
收费全文 | 1336篇 |
免费 | 154篇 |
出版年
2022年 | 7篇 |
2021年 | 20篇 |
2020年 | 7篇 |
2019年 | 10篇 |
2018年 | 14篇 |
2017年 | 16篇 |
2016年 | 33篇 |
2015年 | 60篇 |
2014年 | 51篇 |
2013年 | 88篇 |
2012年 | 95篇 |
2011年 | 86篇 |
2010年 | 48篇 |
2009年 | 48篇 |
2008年 | 67篇 |
2007年 | 74篇 |
2006年 | 61篇 |
2005年 | 58篇 |
2004年 | 63篇 |
2003年 | 64篇 |
2002年 | 53篇 |
2001年 | 29篇 |
2000年 | 29篇 |
1999年 | 36篇 |
1998年 | 14篇 |
1997年 | 18篇 |
1996年 | 21篇 |
1995年 | 10篇 |
1994年 | 11篇 |
1993年 | 16篇 |
1992年 | 17篇 |
1991年 | 17篇 |
1990年 | 11篇 |
1989年 | 9篇 |
1988年 | 8篇 |
1987年 | 12篇 |
1986年 | 13篇 |
1985年 | 8篇 |
1984年 | 11篇 |
1983年 | 9篇 |
1982年 | 14篇 |
1981年 | 17篇 |
1980年 | 9篇 |
1979年 | 14篇 |
1978年 | 15篇 |
1977年 | 7篇 |
1976年 | 11篇 |
1972年 | 12篇 |
1970年 | 12篇 |
1967年 | 6篇 |
排序方式: 共有1490条查询结果,搜索用时 46 毫秒
1.
2.
Mark Andrews Alan Brown Jean-Yves Chiva David Fradet David Gordon Mark Lansdell Malcolm MacKenny 《Bioorganic & medicinal chemistry letters》2009,19(8):2329-2332
The reported selective serotonin Re-uptake Inhibitor Litoxetine was used as the starting point in the design of a range of potential SSRIs with high ease of synthetic accessibility. Preparation and subsequent optimization yielded a range of potent and highly selective SSRIs. 相似文献
3.
4.
Hexaheme nitrite reductases purified to homogeneity from Escherichia coli K-12 and Wolinella succinogenes were studied by low-temperature EPR spectroscopy. In their isolated states, the two enzymes revealed nearly identical EPR spectra when measured at 12 K. Both high-spin and low-spin ferric heme EPR resonances with g values of 9.7, 3.7, 2.9, 2.3 and 1.5 were observed. These signals disappeared upon reduction by dithionite. Reaction of reduced enzyme with nitrite resulted in the formation of ferrous heme-NO complexes with distinct EPR spectral characteristics. The heme-NO complexes formed with the two enzymes differed, however, in g values and line-shapes. When reacted with hydroxylamine, reduced enzymes also showed the formation of ferrous heme-NO complexes. These results suggested the involvement of an enzyme-bound NO intermediate during the six-electron reduction of nitrite to ammonia catalyzed by these two hexaheme nitrite reductases. Heme proteins that can either expose bound NO to reduction or release it are significant components of both assimilatory and dissimilatory metabolisms of nitrate. The different ferrous heme-NO complexes detected for the two enzymes indicated, nevertheless, their subtle variation in heme reactivity during the reduction reaction. 相似文献
5.
6.
M T Thébault J P Raffin J Y Le Gall 《Biochemical and biophysical research communications》1987,145(1):453-459
31P NMR has been used to observe the in vivo phosphometabolite concentrations in the tail musculature from the prawn Palaemon elegans, at rest and after escape swimming and subsequent recovery. Muscular fatigue corresponds to a 60% breakdown of phosphoarginine, and a 45% increase of sugar phosphates. The pHi fell from 7.10 to 6.86. During recovery, the sugar phosphates and arginine phosphate are replenished after 20 minutes. The ATP concentration did not change throughout the experiment. The pHi was restored within 20 minutes. 相似文献
7.
8.
Effects of acetylene on hydrogenases from the sulfate reducing and methanogenic bacteria 总被引:1,自引:0,他引:1
S H He S B Woo D V DerVartanian J Le Gall H D Peck 《Biochemical and biophysical research communications》1989,161(1):127-133
The effect of acetylene on the activity of the three types of hydrogenase from the anaerobic sulfate reducing bacteria has been investigated. The (Fe) hydrogenase is resistant to inhibition by acetylene while the nickel-containing hydrogenases are inhibited by acetylene with the (NiFe) hydrogenase being 10-50 fold more sensitive than the (NiFeSe) hydrogenase. In addition the Ni(III) EPR signal (g approximately 2.3) of the "as isolated" (NiFe) hydrogenase was significantly decreased in intensity upon exposure to acetylene. 相似文献
9.
Protoplasts were isolated from female gametophytes of Chondrus crispus (Stackh.) using commercial cellulase and various carrageenases prepared from marine bacteria. Depending on the nature of the donor tissue (apices or whole thallus, wild or cultivated strains), yields ranged from 1.0–8.5×108 protoplasts per gram of fresh tissue. Preincubating the tissue with a potassium chelator, Kryptofix 222, enhanced protoplast yields by 30–50 %. Based on staining with fluorescein diacetate most protoplasts were viable. A few protoplasts regenerated a cell wall and divided. 相似文献
10.
Raymond Hellio Dr. Claude Fréhel Jean-Yves Rauzier Nalin Rastogi 《Current microbiology》1988,17(4):235-242
Cytochemical characterization of mycobacterial surfaces was carried out on virulent (H37Rv) and avirulent (H37Ra) strains ofMycobacterium tuberculosis. The results were quantified and compared with those obtained with three colony types of the opportunistic pathogenMycobacterium avium. Mycobacterium aurum, a rapidly growing, nonpathogenic species, served as a model for the cytochemical methods. Concanavalin A (ConA) reacted with -d-mannose and -d-glucose residues, whereas negative charged residues were detected with either the ionized ferritin (CF) or the colloidal ferric hydroxide (CIH) method. Strongly acidic sulfate groups were detected by their selective blockage with alcian blue (AB) at pH 1 prior to the CIH labeling at pH 1.8. Weakly acidic groups were demonstrated by AB blockage at pH 2.5 prior to staining with CF stain. Except forM. aurum, all other strains showed a marked heterogeneity in regard to the abundance of their surface labeling. Accessible sulfate groups were present on the cell surface of the virulent H37Rv strain ofM. tuberculosis, but not on the avirulent strain H37Ra. Distribution of ConA receptors, on the other hand, was unrelated to the virulence or pathogenicity of the bacterial strain. 相似文献