全文获取类型
收费全文 | 57961篇 |
免费 | 262篇 |
国内免费 | 556篇 |
专业分类
系统科学 | 1233篇 |
丛书文集 | 293篇 |
教育与普及 | 298篇 |
理论与方法论 | 520篇 |
现状及发展 | 32756篇 |
研究方法 | 846篇 |
综合类 | 20639篇 |
自然研究 | 2194篇 |
出版年
2013年 | 810篇 |
2012年 | 593篇 |
2011年 | 2636篇 |
2009年 | 627篇 |
2008年 | 834篇 |
2007年 | 917篇 |
2006年 | 1006篇 |
2005年 | 1171篇 |
2004年 | 2330篇 |
2003年 | 1932篇 |
2002年 | 1619篇 |
2001年 | 1415篇 |
2000年 | 987篇 |
1999年 | 997篇 |
1998年 | 653篇 |
1997年 | 771篇 |
1996年 | 537篇 |
1994年 | 685篇 |
1993年 | 690篇 |
1992年 | 909篇 |
1991年 | 788篇 |
1990年 | 893篇 |
1989年 | 698篇 |
1988年 | 671篇 |
1987年 | 691篇 |
1986年 | 773篇 |
1985年 | 916篇 |
1984年 | 783篇 |
1983年 | 713篇 |
1982年 | 809篇 |
1981年 | 851篇 |
1980年 | 932篇 |
1979年 | 1461篇 |
1978年 | 1327篇 |
1977年 | 1287篇 |
1976年 | 1139篇 |
1975年 | 1170篇 |
1974年 | 1064篇 |
1973年 | 1243篇 |
1972年 | 1312篇 |
1971年 | 1407篇 |
1970年 | 1517篇 |
1969年 | 1335篇 |
1968年 | 1325篇 |
1967年 | 1179篇 |
1966年 | 986篇 |
1965年 | 776篇 |
1964年 | 526篇 |
1958年 | 647篇 |
1957年 | 568篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
942.
943.
944.
945.
946.
947.
This paper, which presents an annotated checklist of the ‘lower Nymphalidae’ (Libytheinae, Danainae, Satyrinae, Charaxinae), is the fourth in a series on the butterfly fauna of Mount Kilimanjaro. Four genera of lower Nymphalidae (Danaus, Amauris, Bicyclus, Charaxes), with a total of 11 included species, are known or believed to occur within the main forest zone, from c. 1800 to 2800 m. Of these, only three species of Charaxes (Charaxes berkeleyi, Charaxes ansorgei, Charaxes xiphares) may be restricted locally to this primary forest. The lower slopes fauna, below 1800 m, is considerably richer, with a total of 11 genera and 41 species listed (8 species of which extend into the forest zone). Possible additional species, dubious earlier records, problems with African subspecies of Danaus chrysippus, a need for more work on certain Satyrinae, and classification of the genus Charaxes are discussed. An identification key to the subfamilies of Nymphalidae, and the 19 genera of Libytheinae, Danainae, Satyrinae, Charaxinae that occur in Tanzania, together with a key to the adults of all the species of these four subfamilies considered to occur or have occurred on Kilimanjaro, with 206 colour images, are included as online Supplementary Information. 相似文献
948.
Pholoshi A. Maake Edward A. Ueckermann Carl C. Childers 《Journal of Natural History》2016,50(15-16):975-987
Eustigmaeus floridensis sp. nov. is described and illustrated based on female specimens collected from citrus trees in Florida, USA. The new species is closely related to Eustigmaeus arcuata, Eustigmaeus segnis and Eustigmaeus microsegnis, all known to occur in Florida. Eustigmaeus floridensis sp. nov. can be distinguished by larger dimples associated with setae sce, d2 and e1 containing at least four or more vacuoles centrally; dorsal body setae broadly lanceolate and feather-like, except c2, which is slender; anogenital area with striae and one pair of serrated aggenital (ag1) and three pairs of serrated pseudanal (ps1?3) setae. A key to the Eustigmaeus species known to occur across USA is also provided. 相似文献
949.
950.
T. Covarrubias-Camarillo M. Osorio-Beristain L. Legal 《Journal of Natural History》2016,50(35-36):2299-2310
In at least 18 Lepidoptera families, caterpillars build shelters that mainly serve to regulate microclimate (humidity, temperature) and/or to avoid predation. We aimed to explore the function of the tubular structures built with the leaves of the host plant, Acacia cochliacantha Humboldt and Bonpland ex Willdenow (Fabaceae), by a lepidopteran endemic to Mexico, Baronia brevicornis Salvin. We experimentally evaluated whether tubular structure building behaviour is induced by high temperature or predator odour, and if shelters reduce or enhance predation of B. brevicornis caterpillars. We used Calosoma angulatum as predator. Our analyses showed that caterpillars did not make the tubular structures in response to high temperature. We also found no difference in predators’ visual recognition of sheltered versus unsheltered caterpillars. Caterpillars did not build shelters but they moved more often when exposed to predator odour. Unsheltered caterpillars were more frequently consumed when predators were allowed to interact with sheltered and unsheltered caterpillars. Hence, the tubular structures built by B. brevicornis are most likely a strategy for reducing predation, for example by C. angulatum. 相似文献