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961.
The plant-tumorigenic 6b (AK-6b) gene of Agrobacterium tumefaciens strain AKE10 induces morphological alterations to tobacco plants, Nicotiana tabacum. To investigate the molecular mechanisms underlying these processes, we generated transgenic tobacco harboring the AK-6b gene under the control of a dexamethazone-inducible promoter. Upon induction, transgenic tobacco seedlings exhibited distinct
classes of aberrant morphologies, most notably adventitious outgrowths and stunted epicotyls. Histological analysis revealed
massive proliferation and altered venation in the newly established outgrowths. Prominent vascular development suggested that
auxin metabolism or signaling had been altered. Indeed, basipetal auxin transport in the hypocotyls of the transgenic seedlings
was reduced by 50–80%, whereas intracellular auxin contents were only slightly reduced. Analysis of cell extracts by HPLC
revealed a large accumulation of phenolic compounds, including the flavonoid kaempferol-3-rutinoside, in transgenic plants
compared with wild-type seedlings. As some naturally occurring flavonoids have been shown to affect auxin transport, we suggest
that the AK-6b gene expression impairs auxin transport via modulation of phenylpropanoid metabolism, and ultimately results in the observed
morphological alterations.
Electronic Supplementary Material Supplementary material is available for this article at 相似文献
962.
963.
A critical analysis of historically used characters, based on a large series of specimens, is presented. Based on a comparative morphological analysis of type specimens, the 19 species of Sipunculus and four of Xenosiphon are reviewed. The genera and subgenera are redefined so that, after appropriate revisions arc made, Sipunculus (Sipunculus) has eight, Sipunculus (Contraporus) new subgenus has two, and Xenosiphon has only one remaining valid species. A zoogeographical note and a key to the species are included. 相似文献
964.
Tadako Murayama Isao Uno Kimihiko Hamamoto Tatsuo Ishikawa 《Archives of microbiology》1985,142(2):109-112
A cpk mutant of Neurospora crassa with morphological alteration was obtained spontaneously during the cross between the wild-type and a glycerol utilizing cr-l strain. The growth rate of cpk was intermediate between the wild-type and cr-1 mutant strains. The cpk conidia contained a reduced level of carotenoid pigments as compared to the wild-type conidia. The cpk mutant had no detectable amount of cyclic adenosine 3,5-monophosphate (cAMP)-binding protein at all stages of growth tested. On a DEAE-Sephacel column chromatogram, protein kinase activity of the wild type was eluted at two peaks; the first peak was cAMP-dependent, and the second one was not. In contrast, the cpk strain had two peaks of cAMP-independent enzymes. It is suggested that cAMP-dependent protein kinase may be altered in the cpk mutant into a cAMP-independent type by an alteration of the regulatory subunit of this enzyme.Abbreviations cAMP
Cyclic adenosine 3,5-monophosphate
- 8-N3-[3H] cAMP
8-azido-[3H]cyclic adenosine 3,5-monophosphate 相似文献
965.
Synopsis In aquaria and in ponds crosses were made between two closely related allopatric forms of ninespine stickleback of the genus Pungitius (P. pungitius and P. platygaster). There were no ethological isolation mechanisms; F1, F2 and F3 hybrids are fertile; experimental hybrid stocks as well as backcrosses maintain themselves for at least three generations. F1 hybrids are readily distinguishable from parental forms by a combination of morphological characters; F2 hybrids grown in the north near the Arctic circle, are morphologically similar to P. pungitius. The southern form P. platygaster does not survive in northern conditions; eggs of the northern form P. pungitius die at a temperature of 28°C, normal for the spawning of the southern form. By 9 out of 19 studied morphological characters there are distinctions between the two forms. Therefore, ecologically and morphologically the two forms have diverged rather significantly. On the other hand, ethologically and genetically (as judged by the absence of postmating isolating mechanisms) the forms have diverged only slightly. As a result, the differences between the two forms are considered not to exceed the subspecies or at least semispecies rank.In recent years, due to a disturbance of the ranges of both these forms in Eurasia, a tendency for a secondary contact between P. pungitius and P. platygaster appeared in the basins of the rivers Volga and Irtysh. In the immediate future the two forms are expected to come into contact. From our data we predict possible introgressive hybridization between the northern and sourthern forms in natural conditions. 相似文献
966.
Tatsumi Kato 《Journal of plant research》1985,98(4):359-370
A total 25 population samples and some 700 herbarium specimens belonging to theHypericum pseudopetiolatum complex were morphologically examined for better understanding of taxa within the complex. As a result, it was revealed that
three distinct types, which are geographically differentiated, can be recognized within the complex in Japan.
The Japan Sea type characterized by more spherical capsules and remarkable glandular sepals occupies the Japan Sea side of
the Japan Archipelago. The Sohayaki type is characterized by more slender capsules and no or fewer glandular sepals and is
distributed on the Pacific side (so-called Sohayaki region). Distribution ranges of these two types do not overlap except
in northern and central Kyushu, where intermediates between them are sporadically detected. The Hakone type characterized
by long styles and remarkable black glands on the sepals occurs only in the volcanic area in the Fuji-Hakone-Izu region. This
type seems to be closely related to, but clearly differentiated from the Sohayaki type. 相似文献
967.
968.
GARY C. WILLIAMS 《Zoological Journal of the Linnean Society》1988,92(1):1-26
Four new species of soft corals are described from the shallow sublittoral of southern Africa. Three of the species are referable to the genus Alcyonium Linnaeus, 1758 (family Alcyoniidae), although two of these possess growth forms that are atypical for most members of the genus. A revised diagnosis of the genus is therefore included. A new species in the family Nephtheidae is also described, this being referable to the genus Capnella Gray, 1869. All four species are from the region between the Cape of Good Hope Peninsula and the eastern Cape Province of South Africa. This is the region of the Agulhas Bank, an austroafrican biogeographic region that shows a high incidence of endemism with respect to the marine invertebrate fauna. 相似文献
969.
银鲈科鱼类下咽骨的比较研究 总被引:1,自引:0,他引:1
本文比较观察了银鲈科Gerridae鱼类3属,共10种下咽骨和咽齿形态,归纳为6个类型。认为银鲈科鱼类的下咽骨为特化的类型;并对其特化的趋向及与食性的适应关系作了分析。 相似文献
970.
Wieslaw J. Kozek 《Experimental parasitology》1975,37(3):380-387
The sex of encysted and excysted intestine-infecting T. spiralis larvae can be distinguished by the following morphological characteristics: the male larva has a long (approx 50 μm) rectum, and the anterior part of the testis is curved posteriorly. The female larva has a shorter rectum (approx 25 μm), a telogonic ovary, coiled uterine and seminal receptacle primordia, and a vaginal primordium. In paraffin sections males can be recognized by the spermatocytes which are of the same size. The oocytes vary in size: the smallest are located in the ventral portion, the largest on the dorsal portion of the ovary. Sex of the larvae can be differentiated by the length of the rectum as early as the tenth day, by the curvature of the anterior part of the testis and by the uterine primordium by the eleventh day, and by the presence of the vaginal primordium by the thirteenth day of intramuscular development. Farre's Organ is believed to be the primordium of the seminal receptacle. 相似文献