全文获取类型
收费全文 | 6589篇 |
免费 | 369篇 |
国内免费 | 495篇 |
出版年
2024年 | 24篇 |
2023年 | 69篇 |
2022年 | 86篇 |
2021年 | 152篇 |
2020年 | 196篇 |
2019年 | 207篇 |
2018年 | 188篇 |
2017年 | 169篇 |
2016年 | 258篇 |
2015年 | 273篇 |
2014年 | 386篇 |
2013年 | 704篇 |
2012年 | 345篇 |
2011年 | 276篇 |
2010年 | 185篇 |
2009年 | 233篇 |
2008年 | 324篇 |
2007年 | 248篇 |
2006年 | 199篇 |
2005年 | 204篇 |
2004年 | 174篇 |
2003年 | 186篇 |
2002年 | 161篇 |
2001年 | 167篇 |
2000年 | 167篇 |
1999年 | 103篇 |
1998年 | 122篇 |
1997年 | 127篇 |
1996年 | 116篇 |
1995年 | 100篇 |
1994年 | 111篇 |
1993年 | 115篇 |
1992年 | 108篇 |
1991年 | 88篇 |
1990年 | 95篇 |
1989年 | 80篇 |
1988年 | 76篇 |
1987年 | 72篇 |
1986年 | 45篇 |
1985年 | 62篇 |
1984年 | 76篇 |
1983年 | 41篇 |
1982年 | 40篇 |
1981年 | 49篇 |
1980年 | 35篇 |
1979年 | 48篇 |
1978年 | 30篇 |
1977年 | 27篇 |
1975年 | 24篇 |
1973年 | 24篇 |
排序方式: 共有7453条查询结果,搜索用时 15 毫秒
51.
W. B. RUDMAN 《Zoological Journal of the Linnean Society》1988,93(2):133-185
The genus Ceratosoma (Nudibranchia: Chromodorididae) is reviewed and seven species, including two new species, are recognized. Species of the genus are known only from the Indo-West Pacific and it is suggested that the external body shape is the most useful character in distinguishing species. 相似文献
52.
Studies on the tropical marine fungi of Brunei 总被引:4,自引:0,他引:4
Driftwood, mangrove roots and branches, and seaweeds were examined for marine fungi from beaches, rocky shorelines, an artificial lake and mangrove stands. Ninety-five species, some new to science were recorded. This is the largest number of marine fungi reported from a single study. Our knowledge of the geographic distributions of these fungi has been extended. New and rare species are illustrated at the light microscope and SEM levels. 相似文献
53.
54.
K. M. Song T. C. Osborn P. H. Williams 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1988,76(4):593-600
Summary Preliminary analysis using nuclear RFLPs provided evidence that subspecies within Brassica rapa originated from two different centers. One center is in Europe, represented by turnip and turnip rape from which the oilseed sarson was derived. A second center is in South China containing a variety of Chinese vegetables of which pak choi and narinosa seem to be the most ancient forms. Based on RFLP data, the accessions of B. oleracea examined could be divided into three distinct groups, represented by thousand head kale, broccoli and cabbage. Thousand head kale and Chinese kale appear to be the primitive types. Observations of parallel variation among subspecies of both species are discussed. 相似文献
55.
A macromorphological study is made on taxa of the genusOrnithogalum subg.Heliocharmos in North Africa, Spain, and France. The results obtained are consistent with data from cytogenetics, reproductive biology and strategies of reproduction. They allow the retention of two species:O. algeriense andO. umbellatum. A biogeographical and phylogenetic interpretation of the subgenus is proposed for the western Mediterranean. Theoretical views on phenetics are discussed. 相似文献
56.
Seven tetraploid species ofElymus, viz.E. sibiricus, E. caninus, E. gmelinii, E. semicostatus, E. caucasicus, E. parviglume, andE. longearistatus subsp.canaliculatus, representing five sections were studied morphologically and used in interspecific hybridizations. The aim was to investigate whether the present sectional delimitation of the genus was in agreement with genomic data and if there was a correlation between genome constitution and morphology. The study revealed: (i) further information on the genomic affinities between the different species, (ii) that there is no congruence between genome constitution of the species and current sectional delimitation, and (iii) that there is a correlation between genome constitution and morphology in the palea apex shape and in the size of cilia of the palea. 相似文献
57.
李德中;徐克学;肖培根 《武汉植物学研究》1992,10(3):226-234
本文取中国乌头属50种(含变种)植物,选取形态学性状46个、化学性状8个、组织学性状5个、生态学性状1个,运用数量分类方法,对该属进行属下等级的分类研究。根据数学分析结果,确定了树系图中变种、种、系、亚属的分级界线,并在聚类分析的基础上,进一步探讨了各等级类群的划分。 相似文献
58.
环螽属Letana Walker,1869(=Pyrrhicia Stal,1873)迄今已知22种,分布中国、越南、泰国、缅甸、尼泊尔、印度和斯里兰卡等国。作者在整理这个属的标本时发现2新种和1新纪录种,分别采自中国(西藏)和尼泊尔,现记述于后。模式标本均保存在中国科学院上海昆虫研究所。 相似文献
59.
在整理由青海省采得蝗虫标本时,发现1新种,记述如下。模式标本保存于山东大学生物系。青海雏蝗Chorthippus qinghaiensis,新种(图1—8) 雄:体小型。头部短于前胸背板。头顶平,侧缘明显隆起,顶锐角形。头侧窝狭长方形,长为宽的3.3倍。颜面向后倾斜,颜面隆起纵沟较浅,具刻点,侧缘在中眼处略狭。触角丝状,中段一节长为宽的1.4倍。复眼较小,卵圆形,纵径为横径的1.3倍, 相似文献
60.
三节茧蜂属Acampsis Wesmael是屏腹茧蜂亚科中的1个小属,全世界仅知1种。本文新添在我国发现的2个新种:中华三节茧蜂A.chinensis sp.nov.(陕西)和湖南三节茧蜂A.hunanensis sp.nov.(湖南)。这是本属在我国的首次发现,也是在东洋区的首次报道。 相似文献