全文获取类型
收费全文 | 2902篇 |
免费 | 130篇 |
国内免费 | 3篇 |
出版年
2022年 | 8篇 |
2021年 | 19篇 |
2019年 | 16篇 |
2018年 | 23篇 |
2017年 | 17篇 |
2016年 | 27篇 |
2015年 | 48篇 |
2014年 | 68篇 |
2013年 | 251篇 |
2012年 | 156篇 |
2011年 | 146篇 |
2010年 | 91篇 |
2009年 | 87篇 |
2008年 | 159篇 |
2007年 | 162篇 |
2006年 | 171篇 |
2005年 | 181篇 |
2004年 | 186篇 |
2003年 | 205篇 |
2002年 | 194篇 |
2001年 | 30篇 |
2000年 | 15篇 |
1999年 | 28篇 |
1998年 | 50篇 |
1997年 | 50篇 |
1996年 | 35篇 |
1995年 | 32篇 |
1994年 | 35篇 |
1993年 | 24篇 |
1992年 | 37篇 |
1991年 | 26篇 |
1990年 | 16篇 |
1989年 | 23篇 |
1988年 | 28篇 |
1987年 | 21篇 |
1986年 | 10篇 |
1985年 | 22篇 |
1984年 | 30篇 |
1983年 | 32篇 |
1982年 | 42篇 |
1981年 | 33篇 |
1980年 | 26篇 |
1979年 | 17篇 |
1978年 | 17篇 |
1977年 | 18篇 |
1976年 | 15篇 |
1975年 | 19篇 |
1974年 | 14篇 |
1973年 | 9篇 |
1968年 | 7篇 |
排序方式: 共有3035条查询结果,搜索用时 0 毫秒
61.
Toshio Okazaki Masakazu Watanabe Kenya Mizuguchi Kazumi Hosoya 《Ichthyological Research》1991,38(2):133-140
Two types of the dark chub,Zacco temmincki, collected from 10 river systems in Japan were genetically characterized at 27 protein coding loci using starch-gel electrophoresis. They were fixed for different alleles at 13 loci. No hybrid individuals were observed, even in specimens collected in stations where both types appear sympatrically, indicating that each type of the dark chub represents a distinct species. 相似文献
62.
Hiide Yoshino Nobuyuki Miyatani Megumi Saito Toshio Ariga Alessandra Lugaresi Norman Latov Yasunori Kushi Takeshi Kasama Robert K. Yu 《Journal of neurochemistry》1992,59(5):1684-1691
The gangliosides GM1 and GD1b have recently been reported to be potential target antigens in human motor neuron disease (MND) or motor neuropathy. The mechanism for selective motoneuron and motor nerve impairment by the antibodies directed against these gangliosides, however, is not fully understood. We recently investigated the ganglioside composition of isolated bovine spinal motoneurons and found that the ganglioside pattern of the isolated motoneurons was extremely complex. GM1, GD1a, GD1b, and GT1b, which are major ganglioside components of CNS tissues, were only minor species in motoneurons. Among the various ganglioside species in motoneurons, several were immunoreactive to sera from patients with MND and motor neuropathy. One of these gangliosides was purified from bovine spinal cord and characterized as N-glycolylneuraminic acid-containing GM1 [GM1(NeuGc)] by compositional analysis, fast atom bombardment mass spectra, and the use of specific antibodies. Among seven sera with anti-GM1 antibody activities, five sera reacted with GM1(NeuGc) and two did not. Two other gangliosides, which were recognized by another patient's serum, appeared to be specific for motoneurons. We conclude that motoneurons contained, in addition to the known ganglioside antigens GM1 and GD1b, other specific ganglioside antigens that could be recognized by sera from patients with MND and motor neuropathy. 相似文献
63.
Genetic Manipulation of the Extent of Desaturation of Fatty Acids in Membrane Lipids in the Cyanobacterium Synechocystis PCC6803 总被引:1,自引:0,他引:1
Wada Hajime; Gombos Zoltan; Sakamoto Toshio; Murata Norio 《Plant & cell physiology》1992,33(5):535-540
The desA gene of the cyanobacterium, Synechocystis PCC6803,is responsible for the desaturation of fatty acids at the 相似文献
64.
Toshio Sugimoto Tsutomu Kawasaki Tomohiko Kato Robert F. Whittier Daisuke Shibata Yukio Kawamura 《Plant molecular biology》1992,20(4):743-747
A full-length cDNA encoding a subunit of phosphoenolpyruvate carboxylase (PEPC) was isolated from a developing seed expression library of the C3 plant Glycine max. The corresponding mRNA is present at similar levels in leaf, stem, root and developing seed. Two potential start codons exist, and the activity of protein initiated from the first such codon could be subject to regulation by protein kinase. Sequence comparison shows a similar upstream start codon in the case of the Ppc2 gene from Mesembryanthemum crystallinum, previously assumed to lack the sequences necessary for phosphorylation. The soybean encoded protein tends to resemble other C3-type PEPC proteins more closely than those implicated in C4 or crassulacean acid metabolism. 相似文献
65.
Data from the North Pacific sperm whale (Physeter catodon Linnaeus, 1758) fishery were examined for a possible density dependent change in growth during 40 yr harvesting after World War II. Early in this period males from the eastern stock were 16.8 m or less in length. By the early 1970s the largest males in the catch exceeded 16.8 m in length and reached 18.9 m in the late 1970s. The proportion of males measuring over 16.8 m, among sexually mature males (≥14.0 m), increased from 0 to >20% during the 1970s. Increases in the maximum size of males were possibly preceded by a change in the frequency distribution of body lengths in the middle 1960s when only 10% of the postwar catch had been taken. Testis weights suggested an increase in body length at sexual maturity. Two of the three putative North Pacific stocks showed similar growth changes. Adult males taken in the Bering Sea did not show such changes during the exploitation which ended in 1972 because of overfishing. Females showed no detectable change in body size. It is concluded that: (1) density dependent effects on male growth are greater before sexual maturity than after it, (2) males may show density dependent changes even at a population level above 90% of the carrying capacity, (3) polygynous males acquire more mates and realize higher reproductive success because of increased body size, and (4) females appear to maximize production by maturing earlier and shortening calving intervals in response to density change. 相似文献
66.
67.
Li-Chun Huang Cheng-Kuo Hsiao Shu-Huey Lee Bau-Lian Huang Toshio Murashige 《In vitro cellular & developmental biology. Plant》1992,28(1):30-32
Summary Repeated grafting of 0.2-cm shoot tips from fruiting-age trees ofCitrus reticulata Blanco ‘Ponkan’ mandarin andC. sinensis Osbeck ‘Liu Tseng’ sweet orange onto freshly germinated ‘Troyer’ citrange [Poncirus trifoliata (L.) Raf. X.C. sinensis Osbeck] seedlings in vitro resulted in progressive restoration of rooting competence and vigor of regenerated roots and shoots.
The restored traits were retained through the course of the investigation and suggested a phase reversal phenomenon. 相似文献
68.
69.
Impact of whitefish on an enclosure ecosystem in a shallow eutrophic lake: changes in nutrient concentrations,phytoplankton and zoobenthos 总被引:2,自引:2,他引:0
Iwakuma Toshio Hayashi Hidetake Yasuda Ikuko Hanazato Takayuki Takada Kaori 《Hydrobiologia》1990,(1):141-152
Large bag-type (75 m3) and tube-type (105 m3) enclosures were set up in the shallow eutrophic Lake Suwa and were each stocked with exotic planktivorous whitefish (Coregonus lavaretus maraena). The release of whitefish caused the increase in nutrient concentration in the tube-type enclosure whereas no such increase
was observed in the bag-type enclosure. Bottom sediment seemed to be an important source of chironomid food for whitefish.
The proportion of phytoplankton measuring<10μm and 20–40μm, which respectively corresponded toOchromonas spp. andCryptomonas sp., were lower in the fish enclosures than in the control, which might have been caused by high grazing pressure by rotifers.
The predation by whitefish might have affected the species composition of phytoplankton through reducing copepod predation
on rotifers, not through reducing the densities of cladocerans which directly feed on phytoplankton as many investigators
have reported. The phytoplankton biomass was not affected much by the release of fish. Possible reasons are that the increase
in density of rotifers reduced the biomass of available phytoplankton and also that inedible Cyanophyceae were in the decreasing
phase of their seasonal succession and could not increase successfully in spite of elevated nutrient levels. 相似文献
70.
Bag-type enclosures (75 m3) with bottom sheets and tube-type enclosures (105 m3) open to the bottom sediment were stocked with exotic whitefish (Coregonus lavaretus maraena) to study their predation effects on the plankton community. The fish fed mainly on adult chironomids during the period of
their emergence (earlier part of the experimental period). Thereafter, the food preference was shifted to larvae of chironomids
and crustacean zooplankters. The predation effects on the plankton community were not evident in the bag-type enclosures where
zooplankton densities were consistently low. The fish reduced the crustacean populations composed ofBosmina fatalis, B. longirostris andCyclops vicinus in the tube-type enclosures where the prey density was high (above ca. 50 individuals 1−1). The results suggested that the intensity of predation depended on the prey density. Rotifers increased in the fish enclosure,
probably becauseCoregonus reduced the predation pressure byCyclops vicinus on rotifers and allowed the latter to increase. In the fish enclosures, no marked changes in species composition were observed.
Zooplankton predated by the fish seemed to be distributed near the walls of the enclosures. Problems of enclosure experiments
for examining the effects of fish predation on pelagic zooplankton communities are discussed. 相似文献