全文获取类型
收费全文 | 1727篇 |
免费 | 53篇 |
国内免费 | 5篇 |
出版年
2013年 | 29篇 |
2012年 | 33篇 |
2011年 | 40篇 |
2010年 | 54篇 |
2009年 | 94篇 |
2008年 | 40篇 |
2007年 | 72篇 |
2006年 | 45篇 |
2005年 | 52篇 |
2004年 | 27篇 |
2003年 | 18篇 |
1999年 | 11篇 |
1998年 | 26篇 |
1997年 | 44篇 |
1996年 | 37篇 |
1995年 | 31篇 |
1994年 | 27篇 |
1993年 | 25篇 |
1992年 | 34篇 |
1991年 | 18篇 |
1990年 | 27篇 |
1989年 | 24篇 |
1988年 | 22篇 |
1987年 | 15篇 |
1985年 | 13篇 |
1984年 | 15篇 |
1983年 | 17篇 |
1982年 | 14篇 |
1980年 | 15篇 |
1979年 | 20篇 |
1978年 | 16篇 |
1977年 | 16篇 |
1976年 | 17篇 |
1975年 | 25篇 |
1974年 | 12篇 |
1973年 | 19篇 |
1972年 | 15篇 |
1971年 | 14篇 |
1959年 | 33篇 |
1958年 | 65篇 |
1957年 | 77篇 |
1956年 | 70篇 |
1955年 | 55篇 |
1954年 | 64篇 |
1953年 | 63篇 |
1952年 | 59篇 |
1951年 | 43篇 |
1950年 | 18篇 |
1949年 | 33篇 |
1948年 | 19篇 |
排序方式: 共有1785条查询结果,搜索用时 31 毫秒
81.
BRUINSMA J.; KARSSEN C.M.; BENSCHOP M.; VAN DORT J.B. 《Journal of experimental botany》1975,26(3):411-418
Light-grown sunflower seedlings contain 1073 x107 M indoleacetic acid (IAA). The even distributionof this endogenous IAA in straight hypocotyls does not changeduring phototropic curvature. The diffusate from hypocotylscontains substance(s) influencing the elongation rate of Avenacoleoptile segments but hardly any IAA. Phototropic curvature of the hypocotyl requires the presenceof illuminated cotyledons. Illumination of cotyledons inhibitshypocotyl growth. It is concluded that the phototropic response of the sunflowerhypocotyl is regulated by factors promoting and inhibiting cellelongation other than IAA. 相似文献
82.
CH. H. HÄNISCH TEN GATE J. VAN NETTEN J. F. DORTLAND J. BRUINSMA 《Physiologia plantarum》1975,33(4):276-279
Effects of metabolic inhibitors and growth regulators on the course of abscission and on the activities of cell wall solubilizing enzymes were studied in pedicel explants of Begonia flower buds. Actinomycin D, chloramphenicol and 2,4-dinitrophenol slightly retarded abscission, whereas cycloheximide exerted a strong inhibition if applied until 10.5 h after explant excision. Indoleacetic acid retarded and ethylene promoted abscission and cell wall solubilization. However, the activities of cell wall solubilizing enzymes did not correspond with the course of abscission. No polygalacturonase and pectic acid and pectin transeliminases could be detected in the abscission zone during abscission, whereas a low pectin methylesterase activity did not change. Endo- and exocellulase activities did not increase until about 10 h after the onset of abscission, indicating that they are the result rather than the cause of abscission. 相似文献
83.
Hormonal Regulation of Pedicel Abscission in Begonia Flower Buds 总被引:1,自引:0,他引:1
CH. H. HÄNISCH TEN CATE J. BERGHOEF A. M. H. VAN DER HOORN J. BRUINSMA 《Physiologia plantarum》1975,33(4):280-284
In order to analyse the hormonal regulation of flower bud shedding in Begonia, levels of indoleacetic acid (IAA), abscisic acid (ABA) and ethylene were determined in buds and pedicels. The translocation and metabolism of 14C-labeled IAA in pedicel segments were also studied. In a monoecious Begonia fuchsioides hybrid, abscising male flower buds contain about 1% of the IAA present in non-abscising female flowers. In a male Begonia davisii hybrid, the seasonal variation in bud drop coincides with changes in the IAA content of the buds, while also the release of IAA from the bud to the pedicel is hampered. Abscission zones of these pedicels always contain abscission promoting ethylene concentrations. The tissue is prevented from responding with abscission by IAA from the flower buds. The buds also contain ABA but without influencing abscission considerably. Pretreatment with ethylene or ABA does not affect IAA transport in pedicel segments. The rate of this transport is 4–6 mm × h–1:; the capacity increases with the transverse area. In young segments, IAA is decarboxylated and also otherwise metabolized. 相似文献
84.
The oxygen uptake of iris bulbs (Iris×hollandica‘Wedgwood’) which had been stored dry at 30 C (“retarded’ bulbs) was low (10 μmol O2 per h and bulb), the oxygen uptake of the intact bulb, the three outer fleshy scales and the remaining central part of the bulb increased three- to fourfold, nearly twofold and fourfold, respectively. Mitochondria were isolated from the scales of retarded and activated bulbs and their oxygen consumption with succinate, l -malate (plus pyruvate). x-ketoglutarate and NADH as substrate was measured polarographically. The oxidative capacity of mitochondria isolated from the scales of activated bulbs was only slightly higher than that from retarded bulbs when calculated on a tissue basis. No difference was found between the phosphorylation efficiency, respiratory control, cytochrome c deficiency, succinate dehydrogenase, malate dehydrogenase, succinate-cytochrome c rductase, NADH-cytochrome c reductase and cytochrome oxidase activity of the retarded and activated bulbs. The increase in the in vitro oxygen uptake of the scales after transition from 30 to 13 C was not accompanied by an equal increase in the oxidative capacity of their mitochondria suggesting that they are not responsible for this rise in oxygen uptake. 相似文献
85.
86.
87.
88.
89.
90.
JULIA SCHROEDER ROSEMARIE KENTIE MARCO VAN DER VELDE JOS C. E. W. HOOIJMEIJER CHRISTIAAN BOTH OLIVER HADDRATH ALLAN J. BAKER THEUNIS PIERSMA 《Ibis》2010,152(2):368-377
We show that variation in an intronic length polymorphism in the CHD1‐Z gene in Black‐tailed Godwits Limosa l. limosa is associated with fitness correlates. This is the second example of the CHDZ‐1 gene being correlated with fitness, a previous study having established that Moorhens Gallinula chloropus carrying the rare Z* allele have reduced survival. In Godwits, however, carriers of the Z* allele (374 bp) fared better than those with the more frequent Z allele (378 bp) with respect to body mass, plumage ornamentation, reproductive parameters and habitat quality. The Z* allele was found in 14% of 251 adult birds from nature reserves, but was absent from 33 birds breeding in intensively managed agricultural lands. Males and females with the Z* allele had less extensive breeding plumage, and females had a higher body mass, bred earlier and had larger eggs. There were no significant differences in annual survival between birds with and without the Z* allele. DNA isolated from museum skins demonstrated that this polymorphism was present at low frequency in 1929. We speculate that strong asymmetrical overdominance may explain the low frequency of the Z* allele and that genetic linkage to causal genes might be an explanation for the phenotypic correlations. Our findings suggest a degree of cryptic genetic population structuring in the Dutch Godwit population. 相似文献