全文获取类型
收费全文 | 1796180篇 |
免费 | 173831篇 |
国内免费 | 1827篇 |
专业分类
1971838篇 |
出版年
2021年 | 18520篇 |
2018年 | 20052篇 |
2017年 | 18871篇 |
2016年 | 29882篇 |
2015年 | 43580篇 |
2014年 | 51747篇 |
2013年 | 77862篇 |
2012年 | 52416篇 |
2011年 | 44873篇 |
2010年 | 49159篇 |
2009年 | 48768篇 |
2008年 | 40978篇 |
2007年 | 40342篇 |
2006年 | 42342篇 |
2005年 | 43368篇 |
2004年 | 42335篇 |
2003年 | 39381篇 |
2002年 | 37372篇 |
2001年 | 58943篇 |
2000年 | 57223篇 |
1999年 | 50492篇 |
1998年 | 28510篇 |
1997年 | 28410篇 |
1996年 | 27373篇 |
1995年 | 25546篇 |
1994年 | 25157篇 |
1993年 | 24487篇 |
1992年 | 42842篇 |
1991年 | 41076篇 |
1990年 | 39792篇 |
1989年 | 39936篇 |
1988年 | 37098篇 |
1987年 | 35021篇 |
1986年 | 33109篇 |
1985年 | 34361篇 |
1984年 | 31477篇 |
1983年 | 27326篇 |
1982年 | 24882篇 |
1981年 | 23478篇 |
1980年 | 22011篇 |
1979年 | 27636篇 |
1978年 | 23948篇 |
1977年 | 22601篇 |
1976年 | 21298篇 |
1975年 | 21870篇 |
1974年 | 23050篇 |
1973年 | 23278篇 |
1972年 | 20362篇 |
1971年 | 18606篇 |
1970年 | 16386篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
951.
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
952.
953.
954.
955.
956.
Sukhraj S. Dhillon Graeme P. Berlyn Jerome P. Miksche 《American journal of botany》1978,65(2):192-196
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
957.
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
958.
959.
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
960.
Isoproterenol-stimulated cyclic AMP (cAMP) accumulation in lymphocytes is an index of beta-adrenergic receptor functioning. It is not known if a delay between blood collection and subsequent cell preparation influences cAMP accumulation. We compared cAMP levels in lymphocytes processed from whole blood immediately after collection and following a 3.5 hour delay. There were no significant changes in either basal or stimulated levels of cAMP. This information may alleviate time constraints in certain experimental designs where immediate isolation of lymphocytes from whole blood may not be practical. 相似文献