全文获取类型
收费全文 | 16494篇 |
免费 | 1469篇 |
国内免费 | 1451篇 |
出版年
2024年 | 43篇 |
2023年 | 205篇 |
2022年 | 440篇 |
2021年 | 678篇 |
2020年 | 536篇 |
2019年 | 632篇 |
2018年 | 597篇 |
2017年 | 476篇 |
2016年 | 674篇 |
2015年 | 1046篇 |
2014年 | 1198篇 |
2013年 | 1255篇 |
2012年 | 1630篇 |
2011年 | 1428篇 |
2010年 | 876篇 |
2009年 | 802篇 |
2008年 | 968篇 |
2007年 | 856篇 |
2006年 | 817篇 |
2005年 | 654篇 |
2004年 | 585篇 |
2003年 | 486篇 |
2002年 | 426篇 |
2001年 | 226篇 |
2000年 | 195篇 |
1999年 | 195篇 |
1998年 | 174篇 |
1997年 | 138篇 |
1996年 | 115篇 |
1995年 | 112篇 |
1994年 | 114篇 |
1993年 | 75篇 |
1992年 | 93篇 |
1991年 | 90篇 |
1990年 | 60篇 |
1989年 | 54篇 |
1988年 | 45篇 |
1987年 | 47篇 |
1986年 | 36篇 |
1985年 | 52篇 |
1984年 | 25篇 |
1983年 | 20篇 |
1982年 | 20篇 |
1981年 | 31篇 |
1980年 | 24篇 |
1979年 | 28篇 |
1978年 | 23篇 |
1976年 | 16篇 |
1975年 | 14篇 |
1973年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Epiphytic bacteria: development of a method for determining respiring bacteria on leaves 总被引:2,自引:2,他引:0
A method was developed for studying the total numbers and the proportion of active bacteria on leaf surfaces. It involves staining gelatin impressions of leaves treated with an electron transport system indicator, 2-( p -iodophenyl)-3-( p -nitrophenyl)-5-phenyl tetrazolium chloride (INT). The method is rapid, inexpensive and allows simultaneous observation of numbers, ecology and respiratory activity of epiphytic bacteria. The total numbers of epiphytic bacteria for four species of aquatic plants varied between 0.6 to 10.2 times 106 /cm2 . The proportion of active bacteria on leaves of aquatic plants ranged from 2.2 to 42.9%. The method was also applied to a comparison of surface fouling of glass slides and aquatic leaf surfaces, indicating significant differences in numbers of bacteria but little difference in the proportion active on the two surfaces. 相似文献
42.
43.
44.
45.
46.
Eight flavonoids, four 6-oxygenated flavones, two methyl ethers of luteolin, apigenin 6,8-C-diglucoside and quercetin 3-O-glucoside,
were isolated fromNama lobbii andN. rothrockii, sole members of sects.Arachnoidea andCinerascentia, respectively. Both taxa diverge markedly from other namas in morphology and chromosome number and their placement inNama has been questioned. The occurrence of 6-oxygenated flavones in these taxa adds to their already distinctive nature. Flavonoid
evidence argues that both are more closely allied toEriodictyon than either is toNama. 相似文献
47.
Amira Klip Denise Walker Kathleen J. Ransome Dean W. Schroer Gustav E. Lienhard 《Archives of biochemistry and biophysics》1983,226(1):198-205
The glucose transporter in the plasma membrane of rat skeletal muscle has been identified by two approaches. In one, the transporter was detected as the polypeptide that was differentially labeled by photolysis with [3H]cytochalasin B in the presence of l- and d-glucose. [3H]Cytochalasin B is a high-affinity ligand for the transporter that is displaced by d-glucose. In the other, the transporter was detected by means of its reaction with rabbit antibodies against the purified glucose transporter from human erythrocytes. By both procedures, the transporter was found to be a polypeptide with a mobility corresponding to a molecular weight of 45,000–50,000 upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis. 相似文献
48.
A c-type cytochrome from Hydrogenomonas eutropha was purified 150-fold by butanol extraction, ammonium sulfate precipitation, and column chromatography. Three distinct c-type cytochromes were recovered which did not bind with either carbon monoxide or cyanide and hence did not appear to be denatured. Polyacrylamide gel electrophoresis indicated that one protein was acidic and the other two were basic. The acidic cytochrome c had a sedimentation coefficient of 3.46. Its amino acid composition was not markedly different from other bacterial cytochromes, but relative to mammalian cytochromes c it was low in lysine, threonine, and isoleucine and high in alanine and valine. 相似文献
49.
50.