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   1418096篇
  免费   126690篇
  国内免费   1954篇
  2021年   18113篇
  2019年   16300篇
  2018年   18234篇
  2017年   16929篇
  2016年   28556篇
  2015年   43134篇
  2014年   51231篇
  2013年   77681篇
  2012年   41681篇
  2011年   31391篇
  2010年   45344篇
  2009年   46225篇
  2008年   29213篇
  2007年   27533篇
  2006年   32254篇
  2005年   32951篇
  2004年   32322篇
  2003年   29575篇
  2002年   27394篇
  2001年   35118篇
  2000年   32401篇
  1999年   32315篇
  1998年   25762篇
  1997年   25640篇
  1996年   25076篇
  1995年   23242篇
  1994年   22979篇
  1993年   22100篇
  1992年   28188篇
  1991年   26738篇
  1990年   25445篇
  1989年   26051篇
  1988年   23968篇
  1987年   22611篇
  1986年   21692篇
  1985年   23423篇
  1984年   23061篇
  1983年   20404篇
  1982年   20664篇
  1981年   19867篇
  1980年   18605篇
  1979年   19061篇
  1978年   18093篇
  1977年   17237篇
  1976年   16388篇
  1975年   16170篇
  1974年   16704篇
  1973年   17017篇
  1972年   14451篇
  1971年   13323篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
861.
Of 41 fungicides tested in the laboratory, copper carbonate, copper sulphate, mercuric chloride, Agrosan GN, quintozene, kasugamycin, carboxin, pyracar-bolid, carbendazim, chloroneb, benomyl, Ohric, RH 893 (2-n-octyl-4-isothiazole-3-one) and Terrazole were most inhibitory to the mycelial growth of Rhizoctonia solani on Czapek's agar plates and had EC50 values of less than 1 μg a.i./ml, while copper oxychloride, Udonkor, zineb, ziram, F 319 (3-hydroxy-5-methyl isoxazole) and anilazine were much less toxic, ziram being least inhibitory with an EC50 of 214 μg a.i./ml. Of 17 fungicides tested in the greenhouse as seed treatments, thiabendazole, carbendazim, benomyl, thiophanate-methyl, dichlozoline and Ohric gave 80–90% control of damping-off of mung bean seedlings. A single soil drench with thiophanate-methyl and two drenches with benomyl gave about 90% disease control, More seedlings with R. solani infection survived when thiophanate-methyl was used as a post-inoculation soil drench than when benomyl or chloroneb were used.  相似文献   
862.
863.
Laminated pacinian corpuscles from the cat mesentery have been studied morphologically and morphometrically after nerve section and colchicine application to the nerve and the results obtained are represented. Similar interventions in the nerve produce changes in the receptors resembling those of wallerian type degeneration, degeneration rate after sectioning being higher than after colchicine application. At early stages after colchicine application the internal cone and its nuclei increase in size. The data obtained suggest the nuclei of the internal cone to be under neurotrophic control of the sensory neuron that might be realized via axoplasmic transport of substances.  相似文献   
864.
865.
Five populations of Pinus rigida growing in contrasting ecological situations ranging from North Carolina (35°53'N latitude) to Quebec (45°06'N latitude) showed no significant variation in amounts of nuclear DNA with respect to germinating seedlings. Nuclear volume of dormant nuclei also showed no significant variation between and within populations, a finding that is consistent with the concept that the basic 2C DNA value of Pinus rigida is uniform under all habitats. This finding is in contrast to numerous reports for other coniferous species.  相似文献   
866.
Two acrasid cellular slime molds. Guttulinopsis vulgaris and G. nivea, are compared at the ultrastructural level. The amoebae of the two species are indistinguishable except for the presence of intranuclear fibers in G. vulgaris. Both species share some unusual features, including: plate-like cristae in the mitochondria, production of microbody-like organelles in the perinuclear space, spores with thin bilaminar walls, and stalks containing microfilaments bound in striated bundles. These and other observations are discussed with regard to the development of the sorocarps and the relationship of the genus to other members of the Acrasida.  相似文献   
867.
Indomethacin and substance BW-755C in experiments on isolated myometrium striae of pregnant white rats exert an inhibiting effect on the contractile uterus function due to inhibition of cyclooxygenase or lipoxygenase ways of the arachidonic acid transformation. Prostaglandin F2 alpha is sensitive to functioning of the cyclooxygenase and lipoxygenase ways of the arachidonic acid transformation, while oxytocin--only lipoxygenase one. Conclusions rest on results from multiparametric analysis of the contractile uterus function suggested by authors and confirmed by the pattern recognition method--the Karunen-Loev orthogonal decomposition.  相似文献   
868.
There was a range of severity of parasitism of stem-borer larvae by Hymenoptera and Nematoda and much premature death of the larvae. A nematode, Panagrolaimus rigidus, normally considered to be saprophytic, was implicated in some mortality of stem-borer larvae.  相似文献   
869.
870.
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