全文获取类型
收费全文 | 5612篇 |
免费 | 174篇 |
国内免费 | 169篇 |
专业分类
系统科学 | 86篇 |
丛书文集 | 145篇 |
教育与普及 | 75篇 |
理论与方法论 | 44篇 |
现状及发展 | 21篇 |
综合类 | 5082篇 |
自然研究 | 502篇 |
出版年
2024年 | 5篇 |
2023年 | 23篇 |
2022年 | 55篇 |
2021年 | 63篇 |
2020年 | 66篇 |
2019年 | 70篇 |
2018年 | 62篇 |
2017年 | 92篇 |
2016年 | 76篇 |
2015年 | 140篇 |
2014年 | 278篇 |
2013年 | 196篇 |
2012年 | 691篇 |
2011年 | 372篇 |
2010年 | 308篇 |
2009年 | 331篇 |
2008年 | 340篇 |
2007年 | 506篇 |
2006年 | 373篇 |
2005年 | 303篇 |
2004年 | 235篇 |
2003年 | 229篇 |
2002年 | 211篇 |
2001年 | 170篇 |
2000年 | 130篇 |
1999年 | 93篇 |
1998年 | 58篇 |
1997年 | 90篇 |
1996年 | 50篇 |
1995年 | 57篇 |
1994年 | 56篇 |
1993年 | 62篇 |
1992年 | 31篇 |
1991年 | 41篇 |
1990年 | 22篇 |
1989年 | 29篇 |
1988年 | 18篇 |
1987年 | 11篇 |
1986年 | 10篇 |
1985年 | 1篇 |
1984年 | 1篇 |
排序方式: 共有5955条查询结果,搜索用时 15 毫秒
81.
杨国兵 《河北经贸大学学报(综合版)》2014,(1):15-21
以CNKI2008年1月1日-2013年12月25日相关文献为基础,对我国网络问政研究的文献进行梳理,从网络问政研究的兴起与进展、网络问政研究文献的结构分析以及网络问政研究的主题和内容分布三个方面综合分析研究者的观点,可以看出当前我国在网络问政领域的研究存在着不足,如有关网络问政的相关概念有待明晰,研究领域倚重、研究范围有待拓展,研究主题泛化、理论深度有待挖掘,研究方法滞后、学术规范性偏弱。今后,应及时总结并汲取国内外先进经验,加强学术规范性及多学科理论交叉研究。 相似文献
82.
盐碱土改良剂的研究和应用进展 总被引:2,自引:0,他引:2
盐碱化土壤严重阻碍植物生长,对农业生产和生态景观十分不利,有必要利用高效的材料对其进行改良。综述了近年来应用较广泛的盐碱土改良剂及其作用机理,分析各种改良剂的应用范围和优缺点,并对今后改良剂的应用和研究提出了展望。 相似文献
83.
The South Korean species of the genus Exochus are revised. Ten new species, Exochus acostulatus Lee & Choi, sp. nov., Exochus adentatus Lee & Choi, sp. nov., Exochus areolaris Lee & Choi, sp. nov., Exochus carinalis Lee & Choi, sp. nov., Exochus dentisternum Lee & Choi, sp. nov., Exochus depressus Lee & Choi, sp. nov., Exochus nigritulus Lee & Choi sp. nov., Exochus occipitalis Lee & Choi, sp. nov., Exochus orbitalis Lee & Choi, sp. nov. and Exochus propodealis Lee & Choi, sp. nov., are described. Also, 21 species of this genus are reviewed and newly recorded from South Korea, with diagnoses provided. A key to the South Korean species of Exochus and illustrations of external characters are provided.
http://zoobank.org/urn:lsid:zoobank.org:pub:B28700A7-9CA7-4AE7-9816-9C8F4CD46160 相似文献
84.
Sumaya Ahad 《Journal of Natural History》2016,50(27-28):1669-1685
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
85.
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
86.
《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
87.
《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
88.
89.
《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
90.
《Journal of Natural History》2012,46(4):901-916
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