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   204篇
  免费   4篇
  国内免费   23篇
  2024年   1篇
  2023年   1篇
  2022年   3篇
  2021年   4篇
  2020年   1篇
  2019年   12篇
  2018年   3篇
  2017年   2篇
  2016年   6篇
  2015年   6篇
  2014年   8篇
  2013年   16篇
  2012年   5篇
  2011年   15篇
  2010年   4篇
  2009年   7篇
  2008年   7篇
  2007年   10篇
  2006年   9篇
  2005年   8篇
  2004年   10篇
  2003年   8篇
  2002年   9篇
  2001年   5篇
  2000年   10篇
  1999年   4篇
  1998年   3篇
  1997年   8篇
  1996年   2篇
  1995年   8篇
  1994年   6篇
  1993年   2篇
  1992年   3篇
  1991年   3篇
  1990年   4篇
  1989年   3篇
  1987年   4篇
  1985年   2篇
  1984年   2篇
  1983年   1篇
  1981年   2篇
  1980年   1篇
  1979年   1篇
  1978年   1篇
  1976年   1篇
排序方式: 共有231条查询结果,搜索用时 15 毫秒
101.
Microbial diversity of soil and water samples collected from pyrochemicals exposed areas of Virdhunagar district (Tamil Nadu, India) was studied. Soil and water samples from cultivable area, waste land and city area of the same region were also studied for a comparative acount. There is a remarkable reduction in total heterotrophic bacterial population (THB) in pyrochemicals exposed soil and water samples (42 × 104 CFU/g and 5.6 × 104 CFU/ml respectively), compared to the THB of cultivable area soil and water samples (98 × 107 CFU/g and 38.6 × 107 CFU/ml). The generic composition the THB of the pyrochemicals exposed samples too exhibited considerable change compared to other samples. Pseudomonas sp. was the predominant one (41.6%) followed by Achromobacter sp. (25%) in pyrochemical exposed soil and Pseudomonas sp. was the predominant one (25%) in pyrochemical exposed water samples followed by Bacillus sp. (25%) and Micrococcus sp. (16.6%). It was observed that Cornybacterium sp. and Micrococcus sp. were absent completely in pyrochemical exposed soil and Achromobacter sp. was missing in the pyrochemical exposed water samples, which were present in the other samples. The outcome of this study clearly demonstrates that pollutants such as chemicals used in pyrotechniques affect the microbial biodiversity and suitable measures have to be taken to control the pollution level and to save biodiversity.  相似文献   
102.
The genus Peperomia is one of the largest genera of basal angiosperms, comprising about 1500-1700 pantropically distributed species. The currently accepted infrageneric classification divides Peperomia into nine subgenera and seven sections. This classification is based on some 200 species, primarily using fruit morphology. The monophyly of these infrageneric taxa has never been tested and molecular phylogenetic studies of a representative sampling within Peperomia do not exist. This paper provides the first molecular phylogeny for the genus Peperomia. Monophyletic clades within Peperomia are identified and previously used morphological characters are critically reviewed. We show that the importance of some morphological characters has been overestimated and that some of these characters presumably have evolved several times independently. Only one previously described subgenus has been confirmed to be monophyletic.  相似文献   
103.
作者系统研究了新疆乌鲁木齐郝家沟剖面郝家沟组、八道湾组的孢粉化石,共计98属300种(包括2新属4新种)。根据孢粉属种组成及其含量的变化,自下而上分为5套组合:1.Concavisporites-Dictyophyllidites-Chas-matosporites-Cycadopites组合(组合1),2.Cyathidites-Deltoidospora-Chasmatosporites-Cycadopites组合(组合2),3.Cyathidites-Brevilaesuraspora-Chasmatosporites-Cycadopites-Perinopollenites组合(组合3),4.Cyathidi-tes-Osmundacidites-Pinuspollenites-Piceites-Perinopollenites组合(组合4),5.Cyathidites-Contignisporites组合(组合5)。依据组合中一些重要分子的地质时限讨论及其与相关组合的对比,将组合1归为晚三叠世,组合2—组合4归为早侏罗世早期,组合5归为早侏罗世晚期。并讨论了三叠系与侏罗系的界线及八道湾组的地质时代问题。文中描述孢子花粉2新属4新种,图示孢子花粉及疑源类共74属175种。  相似文献   
104.
Three new monotypical genera of leaf beetles are described: Aoriopsis eocenicus n. gen, n. sp. and Acolaspoides longipes n. gen., n. sp. from the subfamily Eumolpinae, and also Crepidocnema yantarica n. gen., n. sp. from the subfamily Alticinae. Short reviews of known fossil records of the mentioned subfamilies are given and position of the new genera discussed.  相似文献   
105.
Deux nouveaux genres et six espèces nouvelles sont décrits de Guyane française, à savoir: Diplozona emboíiata n. sp., Guianocoris unicolor n. g., n. sp., Lundioides couturíerin. gen, n. sp., Neella guiana n. sp., Phytocorís guianus n. sp. et Phytocorís jugatus n. sp. La nouvelle combinaison Guianocoris ruber (Carvalho & Carpintero 1991a) n. comb, est proposée. Deux espèces sont redécrites et illustrées: Sthenaridea carvalhoi Schuh & Schwartz 1988 et Proboscidotyius nigrosquamis (Maldonado 1969). Les genitalias femelles d’lridopeplus pellucidipennis Bergroth 1910 sont décrits pour la premiere fois, ainsi que le mâle d’Henicocnemis luctuosa (Stål 1860). La variabilité de Monalonion annulipes Signoret 1858 est mise en évidence. Quatorze espèces sont signalées comme nouvelles pour la faune de Guyane: Fuivius bisbistiilatus (Stål 1860), F. satipoensis Carvalho & Costa 1994 Henicocnemis Iuctuosa (Stål 1860), Horcisoides punctatus (Carvalho 1976), Maxacalinus cuiabanus Carvalho 1976, Notholopus coreoides Carvalho 1975, N. cuiabanus Carvalho 1975, Proboscidotyius nigrosquamis (Maldonado 1969), Sthenaridea carvalhoi Schuh & Schwartz 1988, Taedia bananaiensis Carvalho & Costa 1994, T. cajabiana Carvalho 1976, T. coimbrai Carvalho 1975, T. compactoides Carvalho 1975 et T. xinguana Carvalho 1975, ce qui porte la liste provisoire des Miridae du Dèpartement à 46 espèces.  相似文献   
106.
An illustrated key is provided to the 19 genera of the subfamily Idolothripinae from China, and a checklist given to 62 named species, of which six species are newly recorded from China, together with the genus Bolothrips that is represented by two un-named species. A generic diagnosis is given for each genus, along with some discussion of systematic relationship problems and species diversity. Identification keys to species of 11 genera are provided, and Megathrips antennatus Guo, Feng & Duan is considered as a new synonymof Megathrips lativentris (Heeger).  相似文献   
107.
Host defense peptides of 35 species of Australian frogs from the hylids Cyclorana and Litoria, and the myobatrachids Crinia, Limnodynastes and Uperoleia have been identified. The biological activities of the majority of these peptides have been determined and include hormones, neuropeptides, opioids, immunomodulators, membrane active peptides [including antimicrobial, anticancer, antiviral (enveloped viruses like HIV and Herpes) and antifungal peptides], neuronal nitric oxide synthase inhibitors, pheromones and individual peptides with other specific activities. The host defense peptide skin profile can be diagnostic at both the species and higher taxonomic levels; for example, species of Crinia, Litoria and Uperoleia each produce quite different types of peptides. Species of Cyclorana and Limnodynastes are more difficult to characterize by skin peptides alone: species of both genera produce similar peptides with no apparent activity. The skin peptide profiles of frogs from the genera Crinia, Litoria and Uperoleia may be used together with morphological and cognate methods, to differentiate between sub-species and even different population clusters of the same species. Nucleotide sequencing of cDNAs of precursors (pre-pro peptides) of bioactive peptides from the skin glands of various species of the genus Litoria show that the majority of these peptides originated from a single ancestor gene before the break away of Australia from Gondwana. The exceptions are the caerulein neuropeptides {e.g. caerulein [pEQDY(SO3H)TGWMDF(NH2)]} which have a different origin to that of other Litoria peptides. Disulfide containing peptides from skin glands of species of Crinia show a different evolutionary route to peptides from species of Litoria.  相似文献   
108.
Engel MS 《ZooKeys》2011,(148):171-184
Forty-eight family-group names are identified for insects among the Isoptera (termites), representing a nearly 19% increase since the last compilation less than 10 years ago. Accordingly, these names are newly catalogued, including various updates from the original summary. The name Reticulitermitidae is recognized as a nomen nudum while Caatingatermitinae is newly considered a nomen invalidum, and neither is available in zoological nomenclature. A catalogue of the suprafamilial names for Isoptera is appended. The name Xylophagodea is formally proposed for the Isoptera + Cryptocercidae clade.  相似文献   
109.
Akkari N  Stoev P  Enghoff H 《ZooKeys》2011,(114):1-14
Two remarkable genera and species of the millipede family Julidae, Titanophyllum spiliarumgen. n., sp. n. and Mammamia profugagen. n. sp., n., are described from caves in Greece and Italy, respectively. The presence of a flagellum and the absence of a 'pro-mesomerital forceps' on the gonopods place them in the tribe Brachyiulini Verhoeff, 1909, an unnatural grouping based on plesiomorphic characters. Both are outstanding in being the only hitherto known blind julidans having such gonopodal features. A dichotomous key to the nine valid brachyiulinine genera based on peripheral and gonopodal characters is presented. Moreover, notes on subanal hooks and anchors in Julida are provided with hypotheses on their possible function.  相似文献   
110.
DM General  GD Alpert 《ZooKeys》2012,(200):1-111
An overview of the history of myrmecology in the Philippine archipelago is presented. Keys are provided to the 11 ant subfamilies and the 92 ant genera known from the Philippines. Eleven ant genera (12%), including 3 undescribed genera, are recorded for the first time from the Philippines. The biology and ecology of the 92 genera, illustrated by full-face and profile photo-images, of Philippine ants are summarized in the form of brief generic accounts. A bibliography of significant taxonomic and behavioral papers on Philippine ants and a checklist of valid species and subspecies and their island distributions are 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