全文获取类型
收费全文 | 1045116篇 |
免费 | 108584篇 |
国内免费 | 1507篇 |
专业分类
1155207篇 |
出版年
2018年 | 10520篇 |
2017年 | 9752篇 |
2016年 | 13972篇 |
2015年 | 18152篇 |
2014年 | 21492篇 |
2013年 | 30577篇 |
2012年 | 34436篇 |
2011年 | 34894篇 |
2010年 | 23720篇 |
2009年 | 21886篇 |
2008年 | 30911篇 |
2007年 | 32074篇 |
2006年 | 29947篇 |
2005年 | 28712篇 |
2004年 | 28129篇 |
2003年 | 27223篇 |
2002年 | 26631篇 |
2001年 | 46081篇 |
2000年 | 45845篇 |
1999年 | 36627篇 |
1998年 | 13252篇 |
1997年 | 13404篇 |
1996年 | 12798篇 |
1995年 | 11831篇 |
1994年 | 11503篇 |
1993年 | 11381篇 |
1992年 | 30092篇 |
1991年 | 29425篇 |
1990年 | 28660篇 |
1989年 | 27802篇 |
1988年 | 25638篇 |
1987年 | 24360篇 |
1986年 | 22692篇 |
1985年 | 22555篇 |
1984年 | 18586篇 |
1983年 | 16186篇 |
1982年 | 12281篇 |
1981年 | 11101篇 |
1980年 | 10307篇 |
1979年 | 17505篇 |
1978年 | 13664篇 |
1977年 | 12327篇 |
1976年 | 11654篇 |
1975年 | 13109篇 |
1974年 | 13971篇 |
1973年 | 13737篇 |
1972年 | 12618篇 |
1971年 | 11130篇 |
1970年 | 9819篇 |
1969年 | 9578篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
4.
A patient with chronic anemia is presented who radiologically showed prominent rugae of the stomach. Angiography demonstrated an arteriovenous malformation with a large feeding artery and prominent draining veins. 相似文献
5.
6.
7.
8.
A. A. Kepel' 《Russian Journal of Marine Biology》2000,26(6):450-452
The alga Analipus japonicus (Harv.) Wynne displays a distinct seasonal pattern in its development in Peter the Great Bay (Sea of Japan). In winter and spring, it occurs only in the form of basal crusts, and vertical axes develop in the summer–autumn period. It reproduces mostly asexually from July to November. Algae with unilocular sporangia occur very seldom, only in June and July. 相似文献
9.
Genetic analysis of sterile mutants in the dpy-5 unc-13 (I) genomic region of Caenorhabditis elegans
Essential genes were identified in the 1.5-map unit dpy-5 unc-13 region of chromosome I in the Caenorhabditis elegans genome by rescuing lethal mutations using the duplication sDp2. In this paper, we report the mapping and complementation testing of lethal mutations, 45 of which identify 18 new, essential
genes. This analysis brings the number of essential genes defined by the sDp2 rescue of lethal mutants to 97; 64 of these map between dpy-5 and unc-13. 61% of these essential genes are identified by more than one allele. Positioning of the mutations was done using the breakpoints
of six duplications. The mutant phenotypes of 14 loci essential for fertility were characterized by Nomarski microscopy and
DAPI staining. None of the mutants were rescued by wild-type male sperm. The cytological data showed that four genes produced
mutants with defects in gonadogenesis, let-395, let-603, let-605 and let-610. Mutations in seven genes, let-355, let-367, let-384, let-513, let-544, let-545 and let-606, affected germ cell proliferation or gametogenesis. Mutants for the remaining three genes, let-370, let-599 and let-604, produced eggs that failed to develop or hatch, thereby acting as maternal effect lethals. We observed a nonrandom distribution
of arrest phenotypes with regard to map position.
Received: 8 May 1996 / Accepted : 27 January 1997 相似文献