全文获取类型
收费全文 | 9387篇 |
免费 | 215篇 |
国内免费 | 862篇 |
专业分类
10464篇 |
出版年
2024年 | 25篇 |
2023年 | 68篇 |
2022年 | 101篇 |
2021年 | 117篇 |
2020年 | 134篇 |
2019年 | 179篇 |
2018年 | 166篇 |
2017年 | 150篇 |
2016年 | 291篇 |
2015年 | 409篇 |
2014年 | 446篇 |
2013年 | 735篇 |
2012年 | 558篇 |
2011年 | 505篇 |
2010年 | 302篇 |
2009年 | 417篇 |
2008年 | 450篇 |
2007年 | 453篇 |
2006年 | 404篇 |
2005年 | 362篇 |
2004年 | 330篇 |
2003年 | 354篇 |
2002年 | 384篇 |
2001年 | 278篇 |
2000年 | 271篇 |
1999年 | 225篇 |
1998年 | 203篇 |
1997年 | 212篇 |
1996年 | 222篇 |
1995年 | 260篇 |
1994年 | 185篇 |
1993年 | 129篇 |
1992年 | 145篇 |
1991年 | 125篇 |
1990年 | 137篇 |
1989年 | 104篇 |
1988年 | 22篇 |
1987年 | 24篇 |
1986年 | 26篇 |
1985年 | 33篇 |
1984年 | 38篇 |
1983年 | 20篇 |
1982年 | 45篇 |
1981年 | 50篇 |
1980年 | 100篇 |
1979年 | 114篇 |
1978年 | 60篇 |
1977年 | 38篇 |
1976年 | 15篇 |
1974年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
981.
982.
四川省高原鳅属鱼类一新种(鲤形目:鳅科) 总被引:4,自引:0,他引:4
本文记述产于凉山西溪河的高原鳅属Triplophysa鱼类一新种,西溪高原鳅TriploPhysaxiqiensissp.nov.,描述了其形态和生态特征,并与近似种进行了比较。 相似文献
983.
984.
An up-to-date checklist of the Italian Dermestidae is provided. The presence of 95 species in Italy is confirmed, while further 5 species (Dermestes (Dermestes) vorax Motschulsky, 1860, Thorictuspilosus Peyron, 1857, T. wasmanni Reitter, 1895, Attagenus (Attagenus) simonis Reitter, 1881 and Globicornis (G.) breviclavis (Reitter, 1878)) and 1 subspecies (A. (A.) tigrinus pulcher Faldermann, 1835) are excluded from the Italian fauna.Attagenus (Attagenus) calabricus Reitter, 1881 and A. (A.) lobatus Rosenhauer, 1856 are for the first time recorded from Abruzzi and Tuscany respectively; A. (A.) silvaticus Zhantiev, 1976 is recorded for the first time from mainland Italy (Apulia); Anthrenus (Anthrenus) angustefasciatus Ganglbauer, 1904 is new to northern Italy (Friuli-Venezia Giulia), central Italy (Tuscany), Apulia and Basilicata; A. (A.) munroi Hinton, 1943 is new to central Italy (Elba Island); A. (A.) delicatus Kiesenwetter, 1851 is for the first time recorded from Apulia; Globicornis (Globicornis) fasciata (Fairmaire & Brisout de Barneville, 1859) is new to southern Italy (Basilicata); G. (Hadrotoma) sulcata (C.N.F. Brisout de Barneville, 1866) is for the first time recorded from central Italy (Abruzzi), Campania and Sicily, whileTrogoderma inclusum LeConte, 1854 is new to Apulia.Seven species (Dermestes (Dermestes) peruvianus Laporte de Castelnau, 1840, D. (Dermestinus) carnivorus Fabricius, 1775, D. (Dermestinus) hankae Háva, 1999, D. (Dermestinus) intermedius intermedius Kalík, 1951, D. (Dermestinus) szekessyi Kalík, 1950, Anthrenus (Anthrenops) coloratus Reitter, 1881 and Trogodermaangustum (Solier, 1849)) recently recorded from Italy (without further details) are discussed.The lectotype and a paralectotype are designated forAttagenus (A.) calabricus Reitter, 1881 from Calabria.Attagenus pellio (Linnaeus, 1758) var. pilosissimus Roubal, 1932 is removed from synonymy with A. (A.) pellio and recognized as a valid species (stat. prom.); it is known from Lombardy, Apulia and Calabria. 相似文献
985.
The organelle ultrastructure and photosynthetic pigments of a new isolate of the picoplanktonic alga Pelagococcus subviridis Norris from the East Australian Current was compared with the North Pacific Ocean type species. No differences in the ultrastructure of the two isolates were observed. Mitosis was studied in detail in the Australian strain, and showed two unusual features: the de novo appearance of centrioles prior to mitosis, and the formation of a small, extra-nuclear spindle. The major carotenoids in both strains were fucoxanthin and a 19′-butanoyloxyfucoxanthin-like pigment, with diadinoxanthin and diatoxanthin as secondary pigments. Several minor carotenoids have not yet been identified. In addition to chlorophylls a and c2, a new chlorophyll c derivative (chlorophyll c3), present in both strains, was separated by high-performance thin-layer chromatography (HPTLC). The Australian isolate, unlike the type material, showed no evidence of chlorophyllase activity during cell harvest and extraction. While the pigment composition suggests affinities with certain newly examined prymnesiophytes, organelle ultrastructure indicates Pelagococcus to be a member of the Chrysophyceae. Mitosis is, however, atypical of both Prymnesiophyceae and Chrysophyceae, and if this picoplanktonic alga is to be retained in the Chrysophyceae it must be seen as a most unusual member. 相似文献
986.
Pedicularis zeylanica subsp. anamallyensis T. Husain & A. Garg, a new subspecies of Nilgiri lousewort from the Western Ghats of south India, is described and illustrated. 相似文献
987.
988.
In this study a new species of Neralsia is described, N. incompleta n. sp. The radial cell shape allows to distinguish it clearly from the rest of species of the genus. The distribution of Neralsia incompleta n. sp. is probably the entire American continent, having been collected from Canada to Paraguay. In spite of its abundance, the associated biology is unknown, although it should be related with parasitism of Diptera Cyclorrhapha. 相似文献
989.
《African Journal of Aquatic Science》2013,38(2):171-174
Additions and changes to the scientific and common names of southern African freshwater fishes made since 1993, are recorded and explained. Nineteen new scientific names are listed including five new species, three genus-name changes, three species-name changes and four new records from the area. Recommended common names for nineteen species are listed. 相似文献
990.
Alexis M. Silver 《Ethnic and racial studies》2013,36(5):824-840
The influx of Latin American immigrants into the US South since the early 1990s has changed the demographic face of the region, particularly among school-aged populations where the rate of growth among Latinos has been the fastest. Despite an emerging literature addressing changing racial and ethnic relations in the New US South, relatively little research has addressed the incorporation of Latino youths within southern schools. Relying on data from a four-year ethnographic and in-depth interview study in one North Carolina town, findings suggest powerful benefits of ethnic-identity based clubs for Latino youths in new immigrant destination schools. While both Latino and African American respondents faced discrimination within their community, Latino students received more formal support at school, which helped shield them from the negative impacts of discrimination. 相似文献