全文获取类型
收费全文 | 4840篇 |
免费 | 553篇 |
国内免费 | 2828篇 |
出版年
2024年 | 63篇 |
2023年 | 179篇 |
2022年 | 273篇 |
2021年 | 269篇 |
2020年 | 270篇 |
2019年 | 293篇 |
2018年 | 191篇 |
2017年 | 217篇 |
2016年 | 187篇 |
2015年 | 252篇 |
2014年 | 377篇 |
2013年 | 341篇 |
2012年 | 506篇 |
2011年 | 453篇 |
2010年 | 403篇 |
2009年 | 383篇 |
2008年 | 466篇 |
2007年 | 460篇 |
2006年 | 374篇 |
2005年 | 379篇 |
2004年 | 283篇 |
2003年 | 250篇 |
2002年 | 273篇 |
2001年 | 229篇 |
2000年 | 215篇 |
1999年 | 130篇 |
1998年 | 71篇 |
1997年 | 48篇 |
1996年 | 50篇 |
1995年 | 35篇 |
1994年 | 24篇 |
1993年 | 32篇 |
1992年 | 24篇 |
1991年 | 18篇 |
1990年 | 24篇 |
1989年 | 13篇 |
1988年 | 20篇 |
1987年 | 12篇 |
1986年 | 13篇 |
1985年 | 17篇 |
1984年 | 11篇 |
1983年 | 7篇 |
1982年 | 5篇 |
1981年 | 12篇 |
1980年 | 6篇 |
1975年 | 4篇 |
1958年 | 6篇 |
1957年 | 13篇 |
1956年 | 8篇 |
1954年 | 5篇 |
排序方式: 共有8221条查询结果,搜索用时 6 毫秒
971.
萝卜抗真菌蛋白1(Rs-AFP1)在大肠杆菌中的融合表达
及其对大丽轮枝菌抑制活性的研究 总被引:1,自引:0,他引:1
ZHOU Xiang-Jun WANG Lun-Shan LIN Zhi-Ping JIA Jun-Wei LU Shan CHU Zhao-Qing CHEN Xiao-Ya 《植物学报(英文版)》2000,42(7):703-707
The Raphanus sativus L. antifungal protein 1 (Rs-AFP1) gene was isolated by polymerase chain reaction (PCR). The complete open reading frame and the fragment encoding the putative mature protein were inserted into the prokaryotic expression vector pET-32b(+), respectively. Subsequent expression showed that the Rs-AFP1 was produced in E. coli as a 27 kD fusion protein only when the N-terminal signal peptide was removed. After treatment with thrombin to remove part of the N-terminal His.tag sequence, the bacterially expressed Rs-AFP1 was used for fungal growth inhibition assay which was conducted on Verticillium dahliae Kleb., a soil-born fungus causing the cotton wilt disease. Results showed that, in the liquid medium, the Rs-AFP1 fusion protein at a concentration of 0.3 g/L clearly inhibited the growth of V. dahliae and the germination of spores. Thus the bacterially expressed fusion protein had the antifungal activity against V. dahliae. 相似文献
972.
973.
五味子科的系统发育:核糖体DNA ITS区序列证据 总被引:3,自引:0,他引:3
The Schisandraceae is one of the most important taxa for understanding the origin and evolution of primitive angiosperms due to its basal position in the recent cladograms of the angiosperm based both on several gene sequences and on morphological characters, but phylogenetic relationships within the family are still unresolved. The sequences of nrDNA ITS region of 15 species representing four sections of Schisandra Michx., two sections of Kadsura Kaempf. ex Juss. and one outgroup, Illicium fargesii Finet et Gagnep., were used to reconstruct the phylogeny of Schisandraceae. Fourteen most parsimonious trees (Length=259, CI=0.934 and RI=0.889) were obtained from the analysis with I.fargesii as the outgroup. In the consensus tree, the genus Schisandra was found to be divided into three clades. Sect. Pleiostema formed a clade together with sect. Maximowiczia, sect. Sphaerostema was weakly supported to be the sister group of a clade comprising S. bicolor var. tuberculata and Kadsura species. In particular, S. bicolor var. tuberculata, a species of sect. Schisandra, was nested within Kadsura. It seems from this result and the morphological characters that Schisandra might not be a monophyletic group. According to the present molecular phylogeny, both elongated hypocarpium and deciduous habit originated independently at least twice in the Schisandraceae, and therefore, the value of the present morphological characters used in the classification of the family Schisandraceae should be reevaluated. 相似文献
974.
干旱诱导性启动子驱动的海藻糖-6-磷酸合酶基因载体的构建及转基因烟草的耐旱性 总被引:39,自引:0,他引:39
The trehalose-6-phosphate synthase gene (TPS) from Saccharomyces cerevisiae Hansen and the drought-responsive promoter from Arabidopsis thaliana (L.) Heynh. have been cloned by PCR procedure. A plant expression vector with TPS under control of Prd29A has been constructed and used for the genetic transformation of tobacco. The transgenic tobacco with Prd29A/TSP demonstrated TPS expression with increased drought tolerance under drought stress. Some obvious morphological changes including dwarf and fine shoot, lancet-shaped leaves and vigorous auxiliary buds have been observed in a few transformed plants. 相似文献
975.
光合系统反应中心普遍存在电荷复合反应形成三线态分子的过程,并通过所形成的三线态β-胡萝卜素将剩余的能量经无辐射通道耗散给环境,实现光合系统的光保护功能.这一过程在人工合成系统中十分罕见,见诸报道的仅有少数由给体-受体组成的超分子体系.首次报道应用染料敏化TiO2胶体颗粒的人工太阳能电池反应,模拟光合系统三线态分子的形成过程,成功地观测到了视黄酸自由基正离子与TiO2表面束缚电子复合而形成的三线态视黄酸分子,并对其光谱和动力学过程进行了纳秒时间分辨光谱表征. 相似文献
976.
本文研究了盐度(0‰~50‰)对无瓣海桑幼苗生长的影响。盐度对无瓣海桑幼苗长叶数、茎长、植株鲜重、主根长、根系鲜重等方面起抑制作用;随盐度的提高,无瓣海桑幼苗成活率下降;但盐度对无瓣海桑幼苗叶片面积存在一个低盐(0‰~10‰)促进、高盐(15‰~40‰)抑制的过程;盐度对叶绿素含量的影响总趋势是随盐度提高,低盐时叶绿素含量下降,而当盐度超过10‰时上升。因此认为:1)无瓣海桑幼苗在无盐存在下,也可正常生长;2)无瓣海桑具有较高的耐盐能力,在盐度0‰~25‰内可正常生长,超过25‰,其生长受到抑制。 相似文献
977.
LIN Qi 《植物分类学报:英文版》2000,38(2):167-181
Taxonomic notes of the genus Illicium Linn. are presented based mainly on herbarium
studies involving more than 10 thousand speciemens from 120 herbaria worldwide, Three new combinations are made, viz, I. fargesii Finet & Gagnep. Subsp. szechuanensis (Cheng) Q. Lin, I.
parvifolium Merr. Subsp. oligandrum (Merr. & Chun)Q. Lin and I. micranhum Dunn subsp.
tsangii (A. C. Smith)Q. Lin, and thirteen species, six subspecies, three varieties and two forms
are reduced to synonyms. Thirty-four species, three subspecies and one variety are recognized inthis genus. 相似文献
978.
Introduction of a rice blight resistance gene,Xa21, into five Chinese rice varieties through anAgrobacterium-mediated system 总被引:7,自引:0,他引:7
A cloned gene, Xa21 was transferred into five widely-used Chinese rice varieties through an Agrobacterium-mediated system, and over 110 independent transgenic lines were obtained. PCR and Southern analysis of transgenic plants revealed the integration of the whole Xa21 gene into the host genomes. The integrated Xa21 gene was stably inherited, and segregated in a 3 : 1 ratio in the selfed T1 generation when one copy of the gene was integrated in the transfor-mants. Inoculation tests displayed that transgenic T0 plants and Xa21 PCR-positive T1 plants were highly resistant to bacterial blight disease. The selected Xa21 homozygous resistant transgenic lines with desirable qualities may be propagated as new varieties or utilized in hybrid rice breeding. 相似文献
979.
Using yeast two-hybrid system to detect interactions of ATP synthase subunits from Spinacia oleracea
Subunit interactions among the chloroplast ATP synthase subunits were studied using the yeast two-hybrid system. Various pairwise combinations of genes encoding a, p, y, 8 and e subunits of Spinach ATP synthase fused to the binding domain or activation domain of GAL4 DNA were introduced into yeast and then expression of a reporter gene encoding p-galactosidase was detected. Of all the combinations, that of y and e subunit genes showed the highest level of reporter gene expression, while those of a and p, a and e, p and e and p and 8 induced stable and significant reporter gene expression. The combination of 8 and e as well as that of 8 and y induced weak and unstable reporter gene expression. However, combinations of a and y, p and y and a and 8 did not induce reporter gene expression. These results suggested that specific and strong interactions between y and e, a and p, a and e, p and e and p and 8 subunits, and weak and transient interactions between 8 and e and 8 and y subunits occurred in the yeast 相似文献
980.
报道了产于我国云南红河流域山柚子科的一个原始新属——甜菜树属,该属具大型圆锥花序,两性,是Lepionurus, Melientha和Champereia 3个单型属的祖型,无疑起源于康滇古陆即今之云南高原,其发现对研究山柚子科的起源与分化具重要意义。 相似文献