全文获取类型
收费全文 | 9106篇 |
免费 | 210篇 |
国内免费 | 838篇 |
出版年
2023年 | 64篇 |
2022年 | 90篇 |
2021年 | 119篇 |
2020年 | 129篇 |
2019年 | 173篇 |
2018年 | 146篇 |
2017年 | 139篇 |
2016年 | 265篇 |
2015年 | 296篇 |
2014年 | 408篇 |
2013年 | 733篇 |
2012年 | 548篇 |
2011年 | 494篇 |
2010年 | 295篇 |
2009年 | 415篇 |
2008年 | 466篇 |
2007年 | 445篇 |
2006年 | 401篇 |
2005年 | 354篇 |
2004年 | 328篇 |
2003年 | 350篇 |
2002年 | 374篇 |
2001年 | 279篇 |
2000年 | 267篇 |
1999年 | 220篇 |
1998年 | 200篇 |
1997年 | 207篇 |
1996年 | 224篇 |
1995年 | 258篇 |
1994年 | 181篇 |
1993年 | 132篇 |
1992年 | 145篇 |
1991年 | 130篇 |
1990年 | 136篇 |
1989年 | 102篇 |
1988年 | 24篇 |
1987年 | 21篇 |
1986年 | 21篇 |
1985年 | 36篇 |
1984年 | 38篇 |
1983年 | 21篇 |
1982年 | 42篇 |
1981年 | 51篇 |
1980年 | 101篇 |
1979年 | 116篇 |
1978年 | 62篇 |
1977年 | 38篇 |
1976年 | 15篇 |
1974年 | 14篇 |
1973年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
ABSTRACT Four new species of the collembolan genus Xenylla, X. convexopyga, X. longistriata, X. dotata and X. marina from Korea are described. X. convexopyga is characterized by an absence of the dorsal seta m3 on Th. II-III. While the other three new species share similarities in dorsal chaetotaxic characters. However, they are dissimilar in the following respects: ventral chaetotaxy, body colour, presence or absence of inner teeth on unguis, the length proportion of abdominal segments and thoracic segments, arrangement of anal papillae and the general shape of apical bulb of fourth antennal segment. As a result of this study, a total of 25 species in 6 genera of Hypogastruridae have been recorded from the Korean Peninsula. 相似文献
22.
通过最近的整理,澜沧江共有沙鳅属鱼类3种,它们是斑鳍沙鳅Botia beaufortiSmith、中华沙鳅B.superciliaris Gnther、黑线沙鳅(新种)B.nigrolineata.黑线沙鳅为新种,鉴别特征是沿背中和体侧有显著的黑色纵条,起自头后止于尾鳍基。首次提出云南沙鳅Botia yunnanensis Chen可能是斑鳍沙鳅的次异名,中华沙鳅是在澜沧江的首次纪录。在附录中记录了突吻沙鳅B.rostrata Gnther,是国内首次纪录,也是萨尔温江和伊洛瓦底江水系的首次纪录。文中每个种均有插图,对新种作了详细的描述,对老种的有关名称作了(林厂里)订或讨论。 相似文献
23.
Ten species of Lepadella Bory de St. Vincent, 1826, including one new species and one new form, are documented from North-Eastern India. Two of these species are new records from this country and six are new reports from N.E. region. Comments are also made on the status and distribution of various Indian taxa. 相似文献
24.
Meloidogyne californiensis n. sp. is described and illustrated from bulrush Scirpus robustus in California. LM and SEM studies revealed that this species differs from other known species in the genus Meloidogyne especially by the prominent posterior cuticular protuberances in the female, the distinct shape of the perineal pattern which is marked by one prominent stria in the perineum, indistinct lateral lines, many broken discontinuous striae on both sides of the arch, and the excretory pore being located posterior to stylet base. Second-stage juveniles 448-628 μm long, stylet length 11-13 μm, styler delicate, with small knobs sloping posteriorly, cephalic region with 2 or 3 annuli, and inflated rectum. Males vary greatly in size (712-1,952 μm), stylet length 18-28 μm (mean 22 μm), cephalic region slightly set off the body with two or three annuli, spear heavy with massive rounded knobs, lateral field marked by four areolated incisures as seen by SEM. 相似文献
25.
10 new Turkish taxa are described:Arenaria eliasiana, A. sivasica, A. monscragus, A. angustifolioides; Campanula lycica; Scutellaria orientalis subsp.tortumensis; Stachys choruhensis, S. tundjeliensis; Calamintha caroli-henricana; Aristolochia rechingeriana, the latter two species named in honour ofKarl Heinz Rechinger;Allium vuralii.
Dedicated to Prof. DrKarl Heinz Rechinger on the occasion of his 80th birthday. For part I see Pl. Syst. Evol.154, 111–128. 相似文献
26.
U. D. Bongale 《Hydrobiologia》1989,171(2):103-106
Six new taxa including two new species (Cosmarium bourrellyi Bongale sp. nov. andC. desikacharyi Bongale sp. nov.) and four new varieties (C. auriculatum var.protrusum Bongale var. nov.,C. pachydermum var.inflatum Bongale var. nov.,C. pseudoconnatum var.tuberculans Bongale var. nov. andC. quadrum var.rotundatum Bongale var. nov.) are reported. Algae were collected from a paddy field at Belgaum. 相似文献
27.
Eckhard Fischer Birgit Strehlow Dieter Hartz Volkmar Braun 《Archives of microbiology》1990,153(4):329-336
After uptake of microbial ferrisiderophores, iron is assumed to be released by reduction. Two ferrisiderophore-reductase activities were identified in Escherichia coli K-12. They differed in cellular location, susceptibility to amytal, and competition between oxygen and ferrichrome-iron(III) reduction. The ferrisiderophore reductase associated with the 40,000×g sediment (membrane-bound enzyme) was inhibited by 10 mM amytal in contrast to the ferrisiderophore reductase present in the 100,000×g supernatant (soluble enzyme). Reduction by the membrane-bound enzyme followed sigmoid kinetics, but was biphasic in the case of the soluble enzyme. The soluble reductase could be assigned to a protein consisting of a single polypeptide of M
r
26000. Reduction of iron(III) by the purified enzyme depended on the addition of NADH or NADPH which were equally active reductants. The cofactor FMN and to a lesser degree FAD stimulated the reaction. Substrate specificity of the soluble reductase was low. In addition to the hydroxamate siderophores arthrobactin, schizokinen, fusigen, aerobactin, ferrichrome, ferrioxamine B, coprogen, and ferrichrome A, the iron(III) complexes of synthetic catecholates, dihydroxy benzoic acid, and dicitrate, as well as carrier-free iron(III) were accepted as substrates. Both ferrisiderophore reductases were not controlled by the fur regulatory system and were not suppressed by anaerobic growth.Abbreviations DHB
dihydroxybenzoic acid
- MECAM
1,3,5-N,N,N-tris-(2,3-dihydroxybenzoyl)-triamino-methylbenzene
- MECAMS
2,3-dihydroxy-5-sulfonyl-derivative of MECAM 相似文献
28.
湖北省淡水蟹类的动物地理学分析及新亚种的记述(软甲纲:十足目) 总被引:2,自引:0,他引:2
湖北省蟹类地理分布的分析结果,古北界和东洋界的划线以31°N上下为过渡区,中部以汉水为界,113°E以东则逐步转向黄淮平原区,因此该省不仅是南北的转折,也是东西的交接地带。文中报道了两个新亚种:Sinopotamon denticulatum styxum S.depressum obliquum。 相似文献
29.
本文报道了岩羊小肠的祁连毛圆线虫,新种Trichostrongylus qilianensis sp. nov., 其形态与已发表的39种毛圆线虫均有明显区别。 相似文献
30.
龟鳖类锥虫两新种(动体目:锥体科) 总被引:1,自引:0,他引:1
龟鳖类锥虫的研究,国内外均比较少。本文记述了在中华鳖和乌龟血液中发现的两新种,鳖锥虫和龟锥虫。这是国内首次对龟鳖类锥虫研究的报道。 相似文献