全文获取类型
收费全文 | 904篇 |
免费 | 41篇 |
专业分类
945篇 |
出版年
2021年 | 11篇 |
2020年 | 5篇 |
2019年 | 10篇 |
2018年 | 12篇 |
2017年 | 9篇 |
2016年 | 12篇 |
2015年 | 23篇 |
2014年 | 29篇 |
2013年 | 39篇 |
2012年 | 44篇 |
2011年 | 48篇 |
2010年 | 34篇 |
2009年 | 25篇 |
2008年 | 76篇 |
2007年 | 72篇 |
2006年 | 93篇 |
2005年 | 75篇 |
2004年 | 63篇 |
2003年 | 65篇 |
2002年 | 58篇 |
2001年 | 6篇 |
2000年 | 5篇 |
1999年 | 8篇 |
1998年 | 5篇 |
1997年 | 11篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1994年 | 9篇 |
1993年 | 2篇 |
1992年 | 5篇 |
1991年 | 7篇 |
1990年 | 7篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1983年 | 6篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1975年 | 5篇 |
1974年 | 5篇 |
1973年 | 6篇 |
1972年 | 3篇 |
1969年 | 3篇 |
1968年 | 3篇 |
1965年 | 1篇 |
排序方式: 共有945条查询结果,搜索用时 15 毫秒
941.
In this study we determined the levels of trace elements (zinc, copper, lead, cadmium and mercury) in three layers of bones
of the hip joint (cartilage, compact bone and spongy bone) of 30 red foxes (Vulpes vulpes) from north-western Poland. Concentrations of Cu, Zn, Pb and Cd were determined by atomic absorption spectrophotometry (ICP-AES)
in inductively coupled argon plasma using a Perkin-Elmer Optima 2000 DV. Determination of Hg concentration was performed by
atomic absorption spectroscopy. In cartilage, compact bone and spongy bone samples from the red fox, median concentrations
of the metals studied could be arranged in the following descending series: Zn > Cu > Pb > Cd > Hg, the values ranging from
142 to 0.002 mg/kg dw. There was a significant difference in Cu concentrations, among all the materials analyzed, with much
more Cu found in spongy bone than in compact bone. Significant differences were also noted in the case of Hg concentrations
in cartilage with compact bone and the spongy bone, and between concentrations of this metal in compact bone and spongy bone.
In males, the concentration of Hg in spongy bone was greater than in females. Younger foxes had a higher concentration of
this metal in cartilage than adults. The strongest synergistic relationships were observed in spongy bone between the Zn and
Cu, Zn and Cd, as well as between Cu and Cd. Statistically significant antagonistic relationships were detected between zinc
and lead in compact bone. In addition to monitoring studies conducted on the abiotic environment, an urgent need exists for
long-term monitoring of concentrations of heavy metals with long-term effects on living organisms. An important addition is
provided by biomonitoring studies on domesticated and free-living mammals, including Canidae. 相似文献
942.
Claudia Hemp Klaus-Gerhard Heller Elzbieta Warchalowska-Sliwa Andreas Hemp 《Organisms Diversity & Evolution》2013,13(4):521-530
The genus Aerotegmina Hemp is common on East African mountains. Two species are known and a third, A. taitensis n. sp., is described in this paper. A. kilimandjarica Hemp is widespread while A. shengenae Hemp is endemic to the South Pare Mountains and A. taitensis n. sp. is known only from the Taita Hills. Morphologically, and from their song, A. shengenae and A. taitensis n. sp. are closely related. In chromosome number A. kilimandjarica (2n?=?33) differs clearly from A. shengenae (2n?=?27). Data presented on other flightless Orthoptera suggest that the South Pare Mountains and the Taita Hills, both belonging to the geologically old mountain chain of the Eastern Arc, show a faunistic similarity not shared by any other mountain range in the area. The mechanisms that led to this phylogeographic pattern in flightless Orthoptera in the Eastern Arc Mountains of northern Tanzania and southern Kenya and the inland volcanoes are discussed. A key to the three Aerotegmina species is presented, as well as bioacoustical data of all species compared to the phaneropterine species Euryastes jagoi. 相似文献
943.
944.
Hybridization studies based on the use of the prototrophic selection technique were undertaken to compare interfertility and DNA-DNA reassociation as criteria for speciation purposes in the yeast genus Kluyveromyces. Degrees of DNA-DNA reassociation > 70% between strains as reported in the literature, were found to correlate with high recombination frequencies. Degrees of DNA-DNA reassociation < 20% between strains did however, not invariably coincide with the absence of interfertility between strains. If interfertility is accepted as criterion for conspecificity, the hitherto reported low degrees ( < 20%) of DNA-DNA reassociation in Kluyveromyces cannot confidently be employed for speciation purposes. 相似文献
945.