全文获取类型
收费全文 | 597200篇 |
免费 | 54004篇 |
国内免费 | 1020篇 |
出版年
2021年 | 3922篇 |
2018年 | 17743篇 |
2017年 | 16648篇 |
2016年 | 14831篇 |
2015年 | 10282篇 |
2014年 | 11401篇 |
2013年 | 15713篇 |
2012年 | 23206篇 |
2011年 | 32772篇 |
2010年 | 25536篇 |
2009年 | 21210篇 |
2008年 | 27463篇 |
2007年 | 29756篇 |
2006年 | 15966篇 |
2005年 | 16351篇 |
2004年 | 16018篇 |
2003年 | 15683篇 |
2002年 | 14956篇 |
2001年 | 20054篇 |
2000年 | 19990篇 |
1999年 | 16413篇 |
1998年 | 6623篇 |
1997年 | 6516篇 |
1996年 | 6082篇 |
1995年 | 5691篇 |
1994年 | 5701篇 |
1993年 | 5689篇 |
1992年 | 13540篇 |
1991年 | 12896篇 |
1990年 | 12780篇 |
1989年 | 12739篇 |
1988年 | 11614篇 |
1987年 | 11037篇 |
1986年 | 10213篇 |
1985年 | 10412篇 |
1984年 | 8629篇 |
1983年 | 7552篇 |
1982年 | 5981篇 |
1981年 | 5267篇 |
1980年 | 5160篇 |
1979年 | 8020篇 |
1978年 | 6363篇 |
1977年 | 5658篇 |
1976年 | 5491篇 |
1975年 | 5820篇 |
1974年 | 6104篇 |
1973年 | 6014篇 |
1972年 | 5976篇 |
1971年 | 5324篇 |
1970年 | 4205篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
994.
P.Mick Richardson 《Biochemical Systematics and Ecology》1982,10(2):197-199
Published results of the distribution of anthocyanins in the Sterculiaceae have been re-interpreted on the basis of the phylogenetic status of the compounds present. A flavonoid score system was less useful than a cladistic interpretation based on Hennigian arguments. 相似文献
995.
996.
997.
Sequences related to the major subunit gene fedA of F107 fimbriae in porcine Escherichia coli strains that express adhesive fimbriae 总被引:1,自引:0,他引:1
Abstract Porcine Escherichia coli strains isolated from cases fo postweaning diarrhea or edema disease were analysed for the presence of fedA , the major subunit gene of F107 fimbriae. The E. coli isolates were known to contain colonisation factor '8813', or to express F107, 2134P or other fimbriae, different from F4, F5, F6, and F41. PCR with fedA -specific primers, restriction enzyme digestion of the PCR product, and nucleotide sequence analysis demonstrated that 2134P pili, colonisation factor '8813' and fimbriae identified on Australian strains of the O141 serotype belong to one family of F107 fimbrial antigens. 相似文献
998.
The number of orientation, feeding and social calls emitted by pipistrelle batsPipistrellus pipistrellus Schreber, 1774 andP. pygmaeus Leach, 1825 was recorded throughout the night at eight different sites. Social calls were unaffected by weather variables,
whereas orientation calls and feeding buzzes were both significantly affected by cloud and temperature conditions. The number
of emissions of each call type was significantly different between sites, indicating that the bats used different sites for
different activities. Significant positive correlations between all three combinations of call types occurred only during
the middle of the night, corresponding with the nadir of flying insects. This suggests that bats were engaged in activities
other than feeding at this time, such as territory protection or mate attraction. 相似文献
999.
D. G. Zamolodchikov V. I. Grabovskii P. P. Shulyak O. V. Chestnykh 《Doklady biological sciences》2017,476(1):200-202
Regional Evaluation of Carbon Budget of Forests (RECBF), was used to study the dynamics of carbon balance in Russian forests in 1988–2015. The carbon sink (excess of absorption over losses) to forests was minimal in 1988. Since the first half of the 1990s, its increase has started. This increase was associated with the reduction of logging volume in connection with socioeconomic reforms. Since 2008, the carbon sink was gradually reduced due to increasing losses in logging operations, forest fires, and decreased carbon absorption. 相似文献
1000.