全文获取类型
收费全文 | 68253篇 |
免费 | 1464篇 |
国内免费 | 10079篇 |
出版年
2022年 | 277篇 |
2021年 | 461篇 |
2020年 | 497篇 |
2019年 | 1065篇 |
2018年 | 1375篇 |
2017年 | 798篇 |
2016年 | 900篇 |
2015年 | 1071篇 |
2014年 | 1580篇 |
2013年 | 2624篇 |
2012年 | 1730篇 |
2011年 | 1283篇 |
2010年 | 1050篇 |
2009年 | 1750篇 |
2008年 | 2011篇 |
2007年 | 2674篇 |
2006年 | 2867篇 |
2005年 | 2895篇 |
2004年 | 3097篇 |
2003年 | 2833篇 |
2002年 | 2777篇 |
2001年 | 2464篇 |
2000年 | 1850篇 |
1999年 | 2086篇 |
1998年 | 1806篇 |
1997年 | 1398篇 |
1996年 | 1341篇 |
1995年 | 1409篇 |
1994年 | 1496篇 |
1993年 | 1336篇 |
1992年 | 1149篇 |
1991年 | 1144篇 |
1990年 | 932篇 |
1989年 | 791篇 |
1988年 | 822篇 |
1987年 | 634篇 |
1986年 | 556篇 |
1985年 | 2026篇 |
1984年 | 3063篇 |
1983年 | 2005篇 |
1982年 | 2387篇 |
1981年 | 2030篇 |
1980年 | 1901篇 |
1979年 | 1686篇 |
1978年 | 1552篇 |
1977年 | 1421篇 |
1976年 | 1307篇 |
1975年 | 1103篇 |
1974年 | 1091篇 |
1973年 | 1026篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
G. N. Swinney 《Journal of fish biology》1995,47(1):39-49
Specimens of the rare deep-sea anglerfish Gigantactis ios , Linophryne brevibarbata , L. aff. coronata and L. racemifera , caught in the north-eastern Atlantic, off Madeira, are reported and compared with previously described specimens, G. ios and L. racemifera are recorded for the first time from the north-eastern Atlantic. 相似文献
92.
Phenylacetic, 3-phenylpropionic, -hydroxyphenylacetic and 3 (-hydroxyphenyl) propionic acids together with the series of C2 to C6 saturated fatty acids previously reported in the anal sac secretion of the red fox () are identified as constituents of the anal sac secretion of the lion (Panthera leo). All these compounds are also observed in the anal sac secretion of the red fox using gas chromatography. The aerobic microflora of red fox and domestic dog () anal sac secretion samples invariably consisted predominantly of and . The hypothesis that the secretion volatiles so far identified may be microbiologically produced is examined. 相似文献
93.
Margarida A. Ferreira M.Aurea Cruz Costa A.Correia Alves M.Helena Lopes 《Phytochemistry》1973,12(2):433-435
7-MethyljugIone, 8,8′-dihydroxy-4,4′-dimethoxy-6,6′-dimethyl-2,2′-binaphthyl-1,1′-quinone, 2-methylnaphthazarin, mamegakinone and euclein have been isolated from Euclea pseudebenus. Euclein is the 3,6′-dimer of 7-methyljuglone. 相似文献
94.
95.
96.
97.
98.
Time course studies of carotenoid production and of mycelial growth in liquid cultures of Phycomyces blakesleeanus wild type [NRRL 1555 (?)], red mutants C9, C10 and C13 and the heterokaryon C2 * C9 are reported. The ratios of the concentrations of lycopene, γ-carotene and β-carotene in the red mutant C13 and in the heterokaryon C2 * C9 during the growth periods were measured. In these strains the concentration of lycopene is close to its final value after 2 days of growth, at a time at which β-carotene is just beginning to be produced. It is suggested that the β-carotene produced late is possibly synthesized via β-zeacarotene. 相似文献
99.
Indol-3yl-acetic acid was identified in extracts of sterile roots of Zeamays seedlings by means of TLC, chromogenic reactions, GLC and GC-MS. 相似文献
100.
Methoxybromination, with HBBT, of long chain methylene interrupted dienes led to simultaneous formation of methoxybromides and dimethoxydibromides. Formation of dimethoxydibromides in which methoxy groups are both internal is limited by steric hindrance.Methoxybromination of long chain conjugated dienes forms, in nearly equal quantities, methoxybromides resulting from a 1,4 addition and methoxybromides from 1,2 addition in which the methoxy group is adjacent to the double bond. 相似文献