全文获取类型
收费全文 | 327345篇 |
免费 | 38060篇 |
国内免费 | 138篇 |
专业分类
365543篇 |
出版年
2018年 | 2897篇 |
2016年 | 3993篇 |
2015年 | 5501篇 |
2014年 | 6482篇 |
2013年 | 9181篇 |
2012年 | 10272篇 |
2011年 | 10495篇 |
2010年 | 7108篇 |
2009年 | 6281篇 |
2008年 | 9111篇 |
2007年 | 9499篇 |
2006年 | 8846篇 |
2005年 | 8537篇 |
2004年 | 8588篇 |
2003年 | 8265篇 |
2002年 | 8213篇 |
2001年 | 14395篇 |
2000年 | 14399篇 |
1999年 | 11564篇 |
1998年 | 4129篇 |
1997年 | 4195篇 |
1996年 | 3991篇 |
1995年 | 3837篇 |
1994年 | 3838篇 |
1993年 | 3725篇 |
1992年 | 9846篇 |
1991年 | 9431篇 |
1990年 | 9248篇 |
1989年 | 8984篇 |
1988年 | 8390篇 |
1987年 | 8008篇 |
1986年 | 7246篇 |
1985年 | 7353篇 |
1984年 | 6073篇 |
1983年 | 5334篇 |
1982年 | 4189篇 |
1981年 | 3712篇 |
1980年 | 3527篇 |
1979年 | 6115篇 |
1978年 | 4564篇 |
1977年 | 4285篇 |
1976年 | 3983篇 |
1975年 | 4308篇 |
1974年 | 4676篇 |
1973年 | 4730篇 |
1972年 | 4373篇 |
1971年 | 4080篇 |
1970年 | 3447篇 |
1969年 | 3346篇 |
1968年 | 2979篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
961.
962.
Species composition and ecological structure of ground beetle population was studied in northern taiga meadows of the Arkhangelsk Region. Meadows in the northern forest zone proved to harbor 91 ground beetle species. Carabid complexes formed in the intrazonal biocenoses of the northern forest zone can be as rich as the family topical groups in the southern forest zone by the number of species and ecological diversity. Ecological properties of the fauna and ground beetle population proved similar in different parts of the forest zone. The proportion of stenobiotic meadow species proved to decrease while that of ecologically plastic ones increased from south to north. The proportion of the genus Harpalus decreased in the ground beetle population while the number of Amara species remained unaltered and their abundance increased. The changes in the species composition caused no transformation of the ecological structure of ground beetle population since they were limited to a single life form or guild. 相似文献
963.
J M Doby B Rault R Barker 《Comptes rendus des séances de la Société de biologie et de ses filiales》1975,169(4):1053-1056
Colonies of Thelohania apodemi in fresh preparations of the brain of the field mouse show an intense fluorescence with ultra violet radiation. This phenomenon is undoubtedly due to the presence of chitin in the spore envelope. It is to our knowledge the first time that such a phenomenon of fluorescence has been described in the Microsporida. 相似文献
964.
965.
I M Badalova B N Mishan'kin I Iu Suchkov 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1987,(5):24-28
In two different strains of cholera vibrios two recA-dependent plasmids, pVib I (1.9-2.2 Md) and pVib II (5.2-5.8 Md), have been detected. These plasmids determine the synthesis of vibriocin, coagulase and fibrinolysin, which has been established by the cotransformation of the DNA of plasmids pVib I and pBR322 and by the transfer mobilization with the use of plasmid RP4. 相似文献
966.
C Gottesmann J Rebelle B Maillet M Rodi J L Rallo 《Comptes rendus des séances de la Société de biologie et de ses filiales》1975,169(6):1584-1589
The authors describe the results obtained on rats by a method of four channel telemetric recording system. The transmitter with a range of a few meters, has a pass band from 0,3 to 400 Hz, weighs 4 grams and can operate autonomously for a minimum of 10 days. 相似文献
967.
968.
969.
970.
A Girre J Gaubicher B Rault 《Comptes rendus des séances de la Société de biologie et de ses filiales》1980,174(6):948-956
A continuous flow incubation (perifusion) was used to examine the effect of 5 alpha-androstane-3 beta, 17 beta diol 3 beta diol) on the release of FSH induced by LH-RH. Over a 3 h-period the 3 beta diol exerts inhibitory effects on male and female pituitaries at high dose (1 microgram/ml) and only on male pituitaries at low dose (100 ng/ml). 相似文献