全文获取类型
收费全文 | 297061篇 |
免费 | 16758篇 |
国内免费 | 90篇 |
专业分类
313909篇 |
出版年
2018年 | 3963篇 |
2017年 | 4040篇 |
2016年 | 6317篇 |
2015年 | 9034篇 |
2014年 | 9866篇 |
2013年 | 11474篇 |
2012年 | 11919篇 |
2011年 | 9821篇 |
2010年 | 7612篇 |
2009年 | 6746篇 |
2008年 | 7631篇 |
2007年 | 7869篇 |
2006年 | 7610篇 |
2005年 | 13081篇 |
2004年 | 11923篇 |
2003年 | 9906篇 |
2002年 | 7518篇 |
2001年 | 10182篇 |
2000年 | 9226篇 |
1999年 | 8207篇 |
1998年 | 2419篇 |
1997年 | 2102篇 |
1996年 | 1908篇 |
1992年 | 7007篇 |
1991年 | 7259篇 |
1990年 | 7225篇 |
1989年 | 7155篇 |
1988年 | 6763篇 |
1987年 | 6291篇 |
1986年 | 5740篇 |
1985年 | 5917篇 |
1984年 | 4528篇 |
1983年 | 3651篇 |
1982年 | 2384篇 |
1981年 | 2061篇 |
1980年 | 2001篇 |
1979年 | 4221篇 |
1978年 | 3207篇 |
1977年 | 2849篇 |
1976年 | 2828篇 |
1975年 | 3476篇 |
1974年 | 3885篇 |
1973年 | 3830篇 |
1972年 | 3492篇 |
1971年 | 3305篇 |
1970年 | 2845篇 |
1969年 | 2822篇 |
1968年 | 2593篇 |
1967年 | 2371篇 |
1966年 | 2049篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
83.
84.
85.
86.
87.
88.
The fully enclosed Taiaro lagoon is hypersaline (42.5 psu) and non-tidal; constant salinity and water level result from strong
evaporation balanced by low percolation through the lagoon floor. Seawater can flow over the atoll rim during exceptionally
high seas and may then replenish lagoonal communities with propagules of oceanic origin. The distinctive water chemistry of
the lagoon suggests a possible way of identifying these immigrants. We established this potential by analysing stable isotopes
of carbon and oxygen in the recent growth layers of otoliths of two adult reef fishes, Chaetodon ulietensis and Acanthurus triostegus, collected from both sides of the atoll rim. Fish from the two locations were discriminated by their isotopic signatures,
suggesting that analysis of the microchemical signatures deposited during the larval development could be used in future work
to determine which individuals and species complete their life-cycles in this unusual lagoon.
Accepted: 28 August 1997 相似文献
89.
Application of 1% methol, which, along with cold, activates specific thermosensitive ionic channels, changes the number of functioning cold receptors on the skin of the forearm similarly to the cold exposure test; however, it does not affect the number of heat receptors and does not significantly change the threshold of cold sensation. Group variants of responses to menthol that indicate individual differences in the sensitivity of skin receptors to the effects of methol and cold have been found. The results obtained give grounds to suggest that, from the variant of response to menthol (a decrease, increase, or absence of changes in the number of functioning cold receptors 5 min after menthol application), it is possible to predict specific features of response to cold. 相似文献
90.
Maria V. Sergeeva Vadim V. Mozhaev Joseph O. Rich Yuri L. Khmelnitsky 《Biotechnology letters》2000,22(17):1419-1422
A novel biocatalytic reaction of transamidation of non-activated amides with amines is reported. Among 45 different lipolytic and proteolytic enzymes tested, only the lipase from Candida antarcticawas able to catalyze this reaction. The reaction proceeded with up to ca. 80% conversion in anhydrous methyl tert-butyl ether and worked with both N-substituted and unsubstituted amides. The biocatalytic transamidation is an equilibrium process and, therefore, higher conversions to the desired amide were achieved by using increased concentrations of the amine nucleophile. 相似文献