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   1399835篇
  免费   131227篇
  国内免费   1934篇
  2021年   18121篇
  2020年   13835篇
  2019年   18093篇
  2018年   19869篇
  2017年   18550篇
  2016年   30084篇
  2015年   44523篇
  2014年   52436篇
  2013年   78829篇
  2012年   40102篇
  2011年   29243篇
  2010年   45783篇
  2009年   46482篇
  2008年   27054篇
  2007年   24915篇
  2006年   29832篇
  2005年   30793篇
  2004年   30038篇
  2003年   27346篇
  2002年   25319篇
  2001年   35091篇
  2000年   32396篇
  1999年   32216篇
  1998年   25621篇
  1997年   25533篇
  1996年   24980篇
  1995年   23161篇
  1994年   22900篇
  1993年   22015篇
  1992年   28092篇
  1991年   26657篇
  1990年   25357篇
  1989年   25991篇
  1988年   23883篇
  1987年   22534篇
  1986年   21631篇
  1985年   23336篇
  1984年   22994篇
  1983年   20347篇
  1982年   20584篇
  1981年   19778篇
  1980年   18519篇
  1979年   19001篇
  1978年   18039篇
  1977年   17157篇
  1976年   16320篇
  1975年   16129篇
  1974年   16650篇
  1973年   16960篇
  1972年   14405篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
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   
972.
973.
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   
974.
975.
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   
976.
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   
977.
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   
978.
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   
979.
980.
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