全文获取类型
收费全文 | 1664871篇 |
免费 | 156179篇 |
国内免费 | 1591篇 |
专业分类
1822641篇 |
出版年
2021年 | 18184篇 |
2019年 | 16329篇 |
2018年 | 19587篇 |
2017年 | 18309篇 |
2016年 | 29538篇 |
2015年 | 43553篇 |
2014年 | 51669篇 |
2013年 | 78215篇 |
2012年 | 46514篇 |
2011年 | 37412篇 |
2010年 | 47638篇 |
2009年 | 47850篇 |
2008年 | 34201篇 |
2007年 | 33306篇 |
2006年 | 36454篇 |
2005年 | 37250篇 |
2004年 | 36427篇 |
2003年 | 33704篇 |
2002年 | 31764篇 |
2001年 | 53014篇 |
2000年 | 50746篇 |
1999年 | 45745篇 |
1998年 | 27639篇 |
1997年 | 27618篇 |
1996年 | 26660篇 |
1995年 | 24845篇 |
1994年 | 24508篇 |
1993年 | 23822篇 |
1992年 | 38741篇 |
1991年 | 36972篇 |
1990年 | 35697篇 |
1989年 | 36006篇 |
1988年 | 33210篇 |
1987年 | 31326篇 |
1986年 | 29599篇 |
1985年 | 31306篇 |
1984年 | 29119篇 |
1983年 | 25526篇 |
1982年 | 23708篇 |
1981年 | 22536篇 |
1980年 | 21054篇 |
1979年 | 25368篇 |
1978年 | 22375篇 |
1977年 | 21282篇 |
1976年 | 20120篇 |
1975年 | 20262篇 |
1974年 | 21312篇 |
1973年 | 21521篇 |
1972年 | 18809篇 |
1971年 | 17133篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
881.
882.
883.
884.
885.
886.
The eggs, larvae and pelagic juveniles ofOstracion meleagris, Lactoria fornasini andLactoria diaphana were identified from reared and field collected specimens from Hawaii, Japan, Australia and the eastern Pacific. Eggs are large and pelagic with limited chorion ornamentation and a cluster of oil droplets. At hatching, larvae are well developed, rotund, and enclosed in a dermal sac. The sac disappears and dermal plates form prior to notochord flexion. Larvae of the three species can be distinguished by their pigment patterns and development of the carapace of ossified dermal plates. Eggs of the three species could not be distinguished. The larval stage ends at a small size (< 6 mm) but the juveniles may grow to a substantial size while remaining pelagic.L. diaphana matures and spawns while pelagic in the eastern Pacific. 相似文献
887.
888.
K.S. Misono R.T. Grammer H. Fukumi T. Inagami 《Biochemical and biophysical research communications》1984,123(2):444-451
Four peptides possessing both natriuretic activity and smooth muscle relaxant activity were isolated from rat atrium and their amino acid sequences determined. The four peptides designated ANF-I, ANF-II, ANF-III and ANF-IV containing 35, 31, 30 and 25 amino acid residues, respectively, were obtained in a molar ratio of 4:60:20:16. The predominant species ANF-II, which may represent the native form of ANF, has the following sequence: (H2N)-G-P-R-S-L-R-R-S-S-C-F-G-G-R-I-D-R-I-G-A-Q-S-G-L-G-C-N-S-F-R-Y-(COOH) in which Cys-10 and Cys-26 are disulfide linked. Cleavage of the aspartyl linkage at position 16 by staphylococcal protease caused complete inactivation, indicating that the ring conformation is essential. The dose-response relationships determined for the four pepdides in relaxing norepinephrine-induced contraction of rabbit thoracic aorta showed half-maximum relaxation at concentrations ranging from 1.5 × 10?9 to 2.5 × 10?9 M. Comparable dose-response relationships were observed in relaxation of carbacol-induced contraction of chick rectum strips as tested with ANF-II and ANF-IV. 相似文献
889.
A. T. Lloyd 《Genetica》1982,58(3):223-228
Surveys of gene frequencies in domestic cat (Felis catus) populations were carried out in four cities in the Netherlands. The principal variants recorded included seven mutant alleles affecting coat colour and hair length. Significant differences in frequencies were found between cities at some of the loci considered. The results of these surveys help to clarify certain trends in the distribution of mutant alleles in cat populations across Europe. Some insight is offered into the importance of trade routes in determining these patterns of distribution. In addition, comparisons between owned pets and unwanted cats indicate that human preferences have little effect on mutant allele frequencies. 相似文献
890.