全文获取类型
收费全文 | 14568篇 |
免费 | 1640篇 |
国内免费 | 3篇 |
专业分类
16211篇 |
出版年
2022年 | 120篇 |
2021年 | 271篇 |
2020年 | 152篇 |
2019年 | 171篇 |
2018年 | 201篇 |
2017年 | 164篇 |
2016年 | 330篇 |
2015年 | 579篇 |
2014年 | 583篇 |
2013年 | 708篇 |
2012年 | 852篇 |
2011年 | 876篇 |
2010年 | 528篇 |
2009年 | 470篇 |
2008年 | 687篇 |
2007年 | 665篇 |
2006年 | 630篇 |
2005年 | 606篇 |
2004年 | 561篇 |
2003年 | 490篇 |
2002年 | 468篇 |
2001年 | 329篇 |
2000年 | 324篇 |
1999年 | 289篇 |
1998年 | 169篇 |
1997年 | 159篇 |
1996年 | 120篇 |
1995年 | 135篇 |
1994年 | 136篇 |
1993年 | 149篇 |
1992年 | 231篇 |
1991年 | 233篇 |
1990年 | 240篇 |
1989年 | 233篇 |
1988年 | 216篇 |
1987年 | 207篇 |
1986年 | 174篇 |
1985年 | 187篇 |
1984年 | 164篇 |
1983年 | 147篇 |
1982年 | 160篇 |
1981年 | 151篇 |
1980年 | 130篇 |
1979年 | 159篇 |
1978年 | 117篇 |
1977年 | 109篇 |
1976年 | 108篇 |
1974年 | 93篇 |
1973年 | 95篇 |
1972年 | 89篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
72.
73.
The structure and possible mode of functioning of the female reproductive system in Nasonia vitripennis (Hymenoptera: Pteromalidae) 总被引:1,自引:0,他引:1
Associated with the female insect reproductive system are a number of glands. Those present in Nasonia vitripennis are described, their microanatomy examined and where possible this is linked with their function during the process of drilling into the host puparium, feeding on the host fluids and oviposition. The structures dealt with are the ovaries, spermatheca, alkaline gland, colleterial gland and the acid gland with reservoir. 相似文献
74.
75.
The metabolism of [2-14C]indole in the rat 总被引:3,自引:1,他引:2
1. [2-14C]Indole has been synthesized from [14C]formate and o-toluidine via N[14C]-formyltoluidine. 2. When fed to rats, the 14C of [14C]indole (dose 70–80mg./kg. body wt.) is fairly rapidly excreted, and in 2 days an average of 81% appears in the urine, 11% in the faeces and 2·4% as carbon dioxide in the expired air. 3. Radioactivity is excreted in the urine as indoxyl sulphate (50% of the dose), indoxyl glucuronide (11%), oxindole (1·4%), isatin (5·8%), 5-hydroxyoxindole conjugates (3·1%), N-formylanthranilic acid (0·5%) and unchanged indole (0·07%). The faeces contain indoxyl sulphate (0·4% of the dose) and indole (0·2%), but the major metabolites have not been identified. 4. Fed to rats with biliary cannulae an average of 5·6% of a dose of [14C]indole (20–60mg./kg. body wt.) is excreted in the bile in 2 days. Radioactivity is present as indoxyl sulphate (0·8% dose) and 5-hydroxyoxindole conjugates (0·6%). 5. Rats further metabolize indoxyl into N-formylanthranilic acid and anthranilic acid, and oxindole into 5-hydroxyoxindole. 6. With rat-liver microsomes plus supernatant under aerobic conditions, indole gives indoxyl, oxindole, possibly isatin, N-formylanthranilic acid and anthranilic acid, but under anaerobic conditions gives only oxindole. Similarly, under aerobic conditions, oxindole gives 5-hydroxyoxindole, anthranilic acid and o-aminophenylacetic acid. 7. Indole is metabolized by two pathways, one via indoxyl to isatin, N-formylanthranilic acid and anthranilic acid, and the other via oxindole to 5-hydroxyoxindole and possibly to o-aminophenylacetic and anthranilic acid. 8. The following new compounds are described: 4-hydroxy-2-nitrophenylacetic acid, 3-, 4- and 5-benzyloxy-2-nitrophenylacetic acid, 5- and 7-hydroxyoxindole and 5-aminoacridine indoxyl sulphate. 相似文献
76.
77.
78.
79.
80.