全文获取类型
收费全文 | 776782篇 |
免费 | 88044篇 |
国内免费 | 1015篇 |
专业分类
865841篇 |
出版年
2016年 | 8526篇 |
2015年 | 12476篇 |
2014年 | 14654篇 |
2013年 | 20409篇 |
2012年 | 23312篇 |
2011年 | 23928篇 |
2010年 | 15917篇 |
2009年 | 14657篇 |
2008年 | 21178篇 |
2007年 | 22002篇 |
2006年 | 20820篇 |
2005年 | 20018篇 |
2004年 | 19980篇 |
2003年 | 18836篇 |
2002年 | 18538篇 |
2001年 | 33403篇 |
2000年 | 33828篇 |
1999年 | 27074篇 |
1998年 | 9666篇 |
1997年 | 9896篇 |
1996年 | 9318篇 |
1995年 | 8907篇 |
1994年 | 8613篇 |
1993年 | 8638篇 |
1992年 | 22365篇 |
1991年 | 21980篇 |
1990年 | 21461篇 |
1989年 | 20751篇 |
1988年 | 19448篇 |
1987年 | 18473篇 |
1986年 | 17532篇 |
1985年 | 17521篇 |
1984年 | 14496篇 |
1983年 | 12483篇 |
1982年 | 9649篇 |
1981年 | 8942篇 |
1980年 | 8186篇 |
1979年 | 13844篇 |
1978年 | 11268篇 |
1977年 | 10160篇 |
1976年 | 9551篇 |
1975年 | 10930篇 |
1974年 | 11959篇 |
1973年 | 11769篇 |
1972年 | 10764篇 |
1971年 | 9847篇 |
1970年 | 8423篇 |
1969年 | 8294篇 |
1968年 | 7593篇 |
1967年 | 6643篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
Besides vobtusine and vobtusine-lactone, deoxyvobtusine was isolated from the leaves of Voacanga grandifolia (Miq. Rolfe. Spectral and chemical evi 相似文献
63.
64.
Metabolic pathways involved in the oxidation of isopropanol into acetone by the intact rat 总被引:3,自引:0,他引:3
Isopropanol administered in a large (6 g/kg, orally) as well as in a lower dose (1 g/kg, I.P.) is slowly oxidized into acetone by the intact rat. Using two inhibitors, 3 amino-1,2,4-triazole and pyrazole, investigations on the hepatic enzymatic system involved in the oxidation of isopropanol show that catalase does not play an important part in this pathway, contrary to alcohol dehydrogenase which is the major enzyme responsible for this oxidation. Although isopropanol oxidation is mainly catalysed in the liver through alcohol dehydrogenase, no alteration of the hepatic extramitochondrial redox state occurs after the administration of a large as well as of a lower dose of isopropanol. From these experiments it may be concluded that alterations of the liver NAD+/NADH ratio, which seem to play an important part in the ethanol induced fatty liver, are not involved in the isopropanol induced one. 相似文献
65.
66.
67.
68.
Tansley Review No. 112 总被引:4,自引:0,他引:4
69.
Y. Salas A. Márquez J. Canelón Y. Perazzo V. Colmenárez J. A. López 《Mycopathologia》2012,174(5-6):511-517
Pythium insidiosum is a pathogenic oomycete known since 1890 that causes pythiosis in mammals. In this report, seven P. insidiosum isolates were recovered from Venezuelan horses and were characterized. The strains were recovered from biopsied tissues and kunkers collected from granulomatous masses located on the hind limb and from a nodular lesion in the left upper eyelid, which decrease the ability of the horses to be used for working purposes. The methods used to identify P. insidiosum isolates were based on the production of sporangia and zoospores, histopathology and PCR assay. To further characterize these strains, portions of the 18S rRNA genes of the seven isolates were sequenced. The sequences showed high homology to previously described P. insidiosum DNA sequences available in GenBank. Similar studies based on the morphological, histological and molecular data identified the etiological agent in samples of granulomatous lesions in these equines as P. insidiosum. In America, the infection has been diagnosed more frequently in equines of Brazil, Colombia, Costa Rica and the United States of America. 相似文献