全文获取类型
收费全文 | 1294篇 |
免费 | 65篇 |
专业分类
1359篇 |
出版年
2015年 | 23篇 |
2014年 | 18篇 |
2013年 | 36篇 |
2012年 | 37篇 |
2011年 | 27篇 |
2010年 | 40篇 |
2009年 | 34篇 |
2008年 | 51篇 |
2007年 | 62篇 |
2006年 | 32篇 |
2005年 | 42篇 |
2004年 | 23篇 |
2003年 | 18篇 |
2002年 | 29篇 |
2001年 | 21篇 |
1999年 | 24篇 |
1998年 | 16篇 |
1997年 | 27篇 |
1996年 | 20篇 |
1995年 | 23篇 |
1994年 | 18篇 |
1993年 | 21篇 |
1992年 | 27篇 |
1991年 | 34篇 |
1990年 | 22篇 |
1989年 | 27篇 |
1988年 | 12篇 |
1987年 | 21篇 |
1986年 | 18篇 |
1985年 | 14篇 |
1984年 | 16篇 |
1982年 | 16篇 |
1980年 | 12篇 |
1979年 | 14篇 |
1976年 | 12篇 |
1975年 | 15篇 |
1974年 | 18篇 |
1973年 | 23篇 |
1972年 | 18篇 |
1971年 | 15篇 |
1969年 | 14篇 |
1965年 | 36篇 |
1964年 | 19篇 |
1963年 | 32篇 |
1962年 | 23篇 |
1961年 | 34篇 |
1960年 | 21篇 |
1959年 | 30篇 |
1958年 | 28篇 |
1957年 | 12篇 |
排序方式: 共有1359条查询结果,搜索用时 0 毫秒
101.
102.
Jacques Simard Dominique Bérubé Märten Sandberg Karl-Heinz Grzeschik Richard Gagné Vidar Hansson Tore Jahnsen 《Human genetics》1992,88(6):653-657
Summary A cDNA for the human catalytic subunit (C) of cAMP-dependent protein kinase (PKA) has been cloned from a testis cDNA library. In the present study, we have determined the chromosomal localization of this gene using a cDNA for C as a probe. Southern blot analysis of genomic DNA from human/mouse cell hybrids revealed that the presence or absence of a 20-kbXbaI fragment, which hybridized with the C probe, was concordant with the presence of human chromosome 1.In situ hybridization to metaphase chromosome confirmed the somatic cell hybrid data and regionally mapped the C gene of PKA to the p36 band on chromosome 1. 相似文献
103.
Expression of Characteristics of Ammonium Nutrition as Affected by pH of the Root Medium 总被引:5,自引:1,他引:5
CHAILLOU S.; VESSEY J. K.; MOROT-GAUDRY J. F.; RAPER C. D. JR; HENRY L. T.; BOUTIN J. P 《Journal of experimental botany》1991,42(2):189-196
To study the effect of root-zone pH on characteristic responsesof -fed plants, soybeans (Glycine max {L.}Merr. cv. Ransom) were grown in flowing solution culture for21 d on four sources of N (1.0 mol m3 , 0.67 mol m3 plus 0.33 mol m3, 0.33 mol m3 plus 0.67 mol m3 , and 1.0 mol m3) with nutrient solutions maintained at pH 6.0, 5.5, 5.0, and 4.5. Amino acid concentration increased inplants grown with as the sole source of N at all pH levels. Total amino acid concentration in the rootsof -fed plants was 8 to 10 times higher than in -fed plants, with asparagine accounting for more than 70% of the total in the roots of these plants.The concentration of soluble carbohydrates in the leaves of-fed plants was greater than that of -fed plants, but was lower in roots of -fed plants, regardless of pH. Starch concentration was only slightlyaffected by N source or root-zone pH. At all levels of pH tested,organic acid concentration in leaves was much lower when was the sole N source than when all or part of theN was supplied as . Plants grown with mixed plus N sources were generally intermediate between - and -fed plants. Thus, changes in tissue compositioncharacteristic of nutrition when root-zone pH was maintained at 4.5 and growth was reduced, still occurredwhen pH was maintained at 5.0 or above, where growth was notaffected. The changes were slightly greater at pH 4.5 than athigher pH levels. Key words: Ammonium, nitrogen nutrition, root-zone pH, soybean, tissue composition 相似文献
104.
Pyronin, when used in the methyl green-pyronin stain, is useful in localizing ribonucleic acid (RNA). That it has rarely been used alone is perhaps a result of the observation (Kurnick 1955) that pyronin stains deoxyrobonucleic acid (DNA) of animal tissue when not competitively inhibited by methyl green. The tests described in this note indicate that pyronin alone can be used to demonstrate RNA in fixed plant tissues. 相似文献
105.
106.
107.
D. EDWARDS H. P. BANKS S. J. CIURCA JR R. S. LAUB 《Botanical journal of the Linnean Society. Linnean Society of London》2004,146(4):399-413
New specimens of Cooksonia and Hostinella are described from the Bertie Group of Ontario and New York State, which is dated by faunas as latest Silurian (Přídolí). The rare plant fossils are unusual in that they are preserved in fine-grained, slightly argillaceous dolostones ('waterlime') rather than clastic rocks. At least two species of Cooksonia are present, one with ± globular sporangial morphology close to C. hemisphaerica Lang. Those with ellipsoidal/discoidal sporangia are compared with C. pertoni Lang, C . paranensis Gerrienne et al . and C. bohemica Schweitzer, the latter represented by a single specimen from the Přídolí of the Czech Republic. However, the paucity of specimens, which prevents assessment of taphonomic influences on shape, combined with the absence of any anatomical features and the gross morphological simplicity of the fossils, precludes specific assignment. Specimens of Hostinella include one in which apices and a lateral basal structure resembling a root are preserved. It is concluded that the Laurentian assemblage of Ontario and New York State is less diverse and disparate than coeval assemblages, which are also preserved in marine rocks. Its preservation in limestones may have been facilitated by the hypersalinity inferred from various sedimentary features, which would restrict the activity of many decomposers. © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 146 , 399–413. 相似文献
108.
Benjamin Roche Lucas Léger Grégory L’Ambert Guillaume Lacour Rémi Foussadier Gilles Besnard Hélène Barré-Cardi Frédéric Simard Didier Fontenille 《PloS one》2015,10(5)
Invasion of new territories by insect vector species that can transmit pathogens is one of the most important threats for human health. The spread of the mosquito Aedes albopictus in Europe is emblematic, because of its major role in the emergence and transmission of arboviruses such as dengue or chikungunya. Here, we modeled the spread of this mosquito species in France through a statistical framework taking advantage of a long-term surveillance dataset going back to the first observation of Ae. albopictus in the Metropolitan area. After validating the model, we show that human activities are especially important for mosquito dispersion while land use is a major factor for mosquito establishment. More importantly, we show that Ae. albopictus invasion is accelerating through time in this area, resulting in a geographic range extending further and further year after year. We also show that sporadic “jump” of Ae. albopictus in a new location far from the colonized area did not succeed in starting a new invasion front so far. Finally, we discuss on a potential adaptation to cooler climate and the risk of invasion into Northern latitudes. 相似文献
109.
David Roiz Philippe Boussès Frédéric Simard Christophe Paupy Didier Fontenille 《PLoS neglected tropical diseases》2015,9(6)
BackgroundExtreme precipitation events are increasing as a result of ongoing global warming, but controversy surrounds the relationship between flooding and mosquito-borne diseases. A common view among the scientific community and public health officers is that heavy rainfalls have a flushing effect on breeding sites, which negatively affects vector populations, thereby diminishing disease transmission. During 2014 in Montpellier, France, there were at least 11 autochthonous cases of chikungunya caused by the invasive tiger mosquito Aedes albopictus in the vicinity of an imported case. We show that an extreme rainfall event increased and extended the abundance of the disease vector Ae. albopictus, hence the period of autochthonous transmission of chikungunya.Conclusions/SignificanceOur empirical data suggests that heavy rainfall events did increase the risk of arbovirus transmission in Southern France in 2014 by favouring a rapid rise in abundance of vector mosquitoes. Further studies should now confirm these results in different ecological contexts, so that the impact of global change and extreme climatic events on mosquito population dynamics and the risk of disease transmission can be adequately understood. 相似文献
110.