首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2405篇
  免费   161篇
  国内免费   74篇
系统科学   10篇
丛书文集   60篇
教育与普及   13篇
理论与方法论   4篇
现状及发展   44篇
综合类   1951篇
自然研究   558篇
  2024年   3篇
  2023年   10篇
  2022年   27篇
  2021年   23篇
  2020年   53篇
  2019年   48篇
  2018年   55篇
  2017年   67篇
  2016年   53篇
  2015年   77篇
  2014年   82篇
  2013年   58篇
  2012年   533篇
  2011年   95篇
  2010年   68篇
  2009年   82篇
  2008年   77篇
  2007年   118篇
  2006年   109篇
  2005年   86篇
  2004年   86篇
  2003年   88篇
  2002年   68篇
  2001年   61篇
  2000年   70篇
  1999年   69篇
  1998年   58篇
  1997年   68篇
  1996年   41篇
  1995年   44篇
  1994年   63篇
  1993年   60篇
  1992年   33篇
  1991年   32篇
  1990年   23篇
  1989年   21篇
  1988年   10篇
  1987年   11篇
  1986年   5篇
  1985年   4篇
  1982年   1篇
排序方式: 共有2640条查询结果,搜索用时 31 毫秒
31.
One new and two known species of the genus Tantunema Siddiqi, 1982 are described and illustrated. Tantunema indicum sp. nov. is characterized by having a small body (length 0.32–0.45 mm); lip region cap-like, set off by slight constriction; odontostyle 6–7 µm and odontophore 8–10 µm long; pharyngeal expansion gradual, expanded part occupying about 35–41% of total neck length, lumen of posterior expanded part widened and thickened; female genital system mono-opisthodelphic, anterior genital branch absent; tail short, hemispheroid, 0.8–1.1 anal body diameter long. Tantunema pakistanense (Timm, 1964) comb. nov. (=Tylencholaimus pakistanensis Timm, 1964) and Tantunema intermedium (Peña-Santiago and Coomans, 1996) Andrássy, 2009 are redescribed. A diagnostic compendium and key to species of the genus is also provided.  相似文献   
32.
Xanthophryne is a toad genus endemic to the northern Western Ghats of India, with two extant sister species – Xanthophryne koynayensis and Xanthophryne tigerina. Both species are local endemics and endangered. We studied reproductive biology of these toads and found that they are specialized to the lateritic rocky outcrops at mid-elevations in high rainfall areas. Xanthophryne toads have sporadic, multiple spawning bouts lasting 2–4 days during early monsoon. In this explosive breeding behaviour, we observed male toads to engage in ‘pelvic thrusts’, a unique and novel behaviour among anurans. Females oviposit in shallow pools in depressions of lateritic boulders where their tadpoles metamorphose. These ephemeral rocky pools have limited resources and they desiccate rapidly with a break in the rains. To mitigate the stochastic risk of desiccation and subsequent large-scale egg/tadpole mortality, females may disperse their reproductive investment spatially and temporally in multiple clutches, and tadpoles metamorphose rapidly. Here, we describe the amplexus, spawning and male advertisement call, and provide a comparative account of the life history traits of the two Xanthophryne species. These toads face numerous threats and are in need of urgent conservation action. These toads, seemingly well adapted to the isolated rocky outcrops, offer an excellent opportunity to understand endemism, mating systems, anuran ecology and behaviour.  相似文献   
33.
In this study, a total of nine species of the family Psychidae were recognised from Korea. Among them, Psyche yeongwolensis sp. nov. is described as new to science. Also, a species, Proutia maculatella Saigusa et Sugimoto, is reported for the first time from Korea. All available material were dissected and illustrated. Also, an annotated catalogue of the family Psychidae from Korea is provided.  相似文献   
34.
Thirty eight species of anascan Cheilostomata are described from the collections of Discovery Investigations, and other British antarctic expeditions. Ten new species are described, including Stomhypselosaria watersi introduced for Cellaria dubia (Busk) sensu Waters (1904). Two new genera are introduced, and Swanomia nom. nov. is proposed for Mawsonia Livingstone 1928, non Woodward 1907.  相似文献   
35.
《Journal of Natural History》2012,46(6):1639-1655
The genus Bovichtus includes four species from the Australasian region, viz. B. variegatus Richardson, B. psychrolutes Günther, B. angustifrons Regan, and B. oculus n. sp. B. decipiens Regan and Aurion effulgens Waite are junior synonyms of B. variegatus and B. psychrolutes respectively. B. oculus, described from a specimen taken in 847–902 m on the Campbell Plateau in the New Zealand Subantarctic, is the first known deep water Bovichtus species. It differs from all congeners in having a very large eye (horizontal diameter <9·0 times in SL) and, alone with B. psychrolutes, has a patch of ctenoid scales on the body behind the pectoral fin base.  相似文献   
36.
《Journal of Natural History》2012,46(9):1287-1295
Marionina macgrathi sp. nov. and M. ulstrupae sp. nov. are described from rock crevices, animal mats and algal turf on a wave-exposed rocky shore at Carnsore Point, County Wexford. Both resemble M. appendiculata Nielsen and Christensen, 1959 in having sigmoid setae and lacking a muscular penial bulb, but differ in possessing seminal vesicles and larger sperm funnels. The new species differ from each other in characters of the sperm funnel, spermatheca, coelomocytes and clitellum. They are compared with material of M. appendiculata from three localities in Ireland and two in USA.  相似文献   
37.
《Journal of Natural History》2012,46(5):1137-1175
The taxonomic value of the notopleural cleft in Phoridae is highlighted. A cladogram relating Gymnophora and Woodiphora to Megaselia is presented. Recognition of the genus Woodiphora is clarified, and the Old World species of Haplophleba transferred to Woodiphora. The evolution of the female abdominal sternite 9 is discussed. The tribe Megaseliini is proposed. A key to the Australasian and Oriental species of Woodiphora is provided. Twenty new species are described and two new synonyms proposed.  相似文献   
38.
A collection of eight species of terrestrial isopods from lava and cave sites on Ascension Island is described. Two species, Niambia longiantennata (Platyarthridae) and Elumoides coecus (Eubelidae), are described as new. Atlantoscia alceui Ferrara and Taiti (Philosciidae) is considered to be a junior synonym of A. floridana (Van Name) and the genus Ocelloscia Schultz and Johnson of Atlantoscia Ferrara and Taiti. At present the oniscidean fauna known from Ascension Island consists of 13 species.  相似文献   
39.
《Journal of Natural History》2012,46(6):1395-1414
Guernea minor sp. nov. and G. ezoensis sp. nov. are described from Japan. Based on these new species and the literature, a tentative revision of the subfamily Prophliantinae is proposed. The subgenus Prinassus of the genus Guernea is invalidated. The subgenus Haustoriopsis of the genus Guernea is re-elevated to a separate genus from Guernea. Dexaminoculus is transferred from Prophliantinae to Dexamininae.  相似文献   
40.
《Journal of Natural History》2012,46(7):1021-1058
A report of the Leucosiidae collected during the Albatross Philippines expedition 1907–1910 is given. A total of 36 species in 17 genera are treated, with one genus (Heterolithadia) and nine species (Alox rugosum, Arcania elongata, Arcania globata, Heterolithadia fallax, Myra acutidens, Leucosia craniolaris, L. galantua, L. perlatta and Nucia tuberculosa) being new records for the Philippines and one species being new. This brings the total number of species known from the Philippines to 64, in 22 genera. A complete list of Philippine Leucosiidae is provided.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号