全文获取类型
收费全文 | 1100篇 |
免费 | 50篇 |
国内免费 | 1篇 |
出版年
2022年 | 6篇 |
2021年 | 15篇 |
2020年 | 15篇 |
2019年 | 12篇 |
2018年 | 18篇 |
2017年 | 19篇 |
2016年 | 21篇 |
2015年 | 51篇 |
2014年 | 40篇 |
2013年 | 73篇 |
2012年 | 97篇 |
2011年 | 94篇 |
2010年 | 64篇 |
2009年 | 51篇 |
2008年 | 79篇 |
2007年 | 75篇 |
2006年 | 66篇 |
2005年 | 65篇 |
2004年 | 72篇 |
2003年 | 73篇 |
2002年 | 68篇 |
2001年 | 7篇 |
2000年 | 7篇 |
1999年 | 6篇 |
1998年 | 6篇 |
1997年 | 3篇 |
1996年 | 9篇 |
1995年 | 9篇 |
1994年 | 4篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1980年 | 1篇 |
1977年 | 3篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1969年 | 1篇 |
1926年 | 1篇 |
排序方式: 共有1151条查询结果,搜索用时 15 毫秒
1.
Nobuhiko Ohga 《Ecological Research》1992,7(3):341-353
Herbaceous lomas in the Peruvian coastal desert, of South America establish in spring, and its habitat is limited to the southern
or southwestern slopes along the coast that are affected by thick fog. The time of appearance, the duration and the thickness
of the fog vary greatly from year to year, so the lomas can grow only in habitats with enough water to, sustain seed germination
and plant growth. This paper studies the species composition and density of the buried seed population, of the herbaceous
lomas of Loma Ancon in order to clarify the mechanisms of the lomas' establishment. The mean number of species with viable
seeds was about, 12 spp. m−2 and that of dead seeds was about 22 spp. m−2. The dominant species wereSolanum tuberiferum, S. pinnatifidum andNolana humifusa, both in viable and dead seeds. Viable seed density was about 5000–8000 seeds m−2, which is comparable with the seed densities of other herbaceous communities. Dead seed density was about 15000–27000 seeds
m−2, or nearly three times the viable seed density, because the rate of decomposition was slow in the extremely dry conditions.
The net increase of viable seeds by seed production was estimated at about 5000 seeds m−2 in 1980, and the increase in the number of dead seeds was 2200 seeds m−2. 相似文献
2.
3.
Abstract A novel mycoplasmal species designated as Mycoplasma penetrans has recently been isolated from patients infected with human immunodeficiency virus. The 16S rRNA gene from this mycoplasma was cloned and its nucleotide sequence determined. This sequence was aligned with previously published homologous sequences from several mycoplasmas and with related Gram-positive bacteria and a phylogenetic tree was constructed. The results indicate that M. penetrans belongs to the evolutionary group Pneumoniae. 相似文献
4.
5.
Tomomi Hidaka Masao Goda Tomohisa Kuzuyama Naomi Takei Makoto Hidaka Haruo Seto 《Molecular & general genetics : MGG》1995,249(3):274-280
The biosynthetic pathway for production of the antibiotic fosfomycin by Streptomyces wedmorensis consists of four steps including the formation of a C-P bond and an epoxide. Fosfomycin production genes were cloned from genomic DNA using S. wedmorensis mutants blocked at different steps of the biosynthetic pathway. Four genes corresponding to each of the biosynthetic steps were found to be clustered in a DNA fragment of about 5 kb. Nucleotide sequencing of a large fragment revealed the presence of ten open reading frames, including the four biosynthetic genes and six genes with unknown functions. 相似文献
6.
Tomomi Nakamoto 《Journal of plant research》1995,108(1):71-75
The growth of the primary seminal root of maize (Zea mays L.) is characterized by an initial negative gravitropic reaction and a later positive one that attains a plagiotropic liminal
angle. The effects of temperature and water potential of the surrounding soil on these gravitropic reactions were studied.
Temperatures of 32, 25, and 18C and soil water potentials of −5,−38, and −67 kPa were imposed and the direction of growth
was measured for every 1 cm length of the root. The initial negative gravitropic reaction extended to a distance of about
10cm from the graln. Higher temperatures reduced the initial negative gravitropic reaction. Lower soil water potential induced
a downward growth at root emergence. A mathematical model, in which it was assumed that the rate of the directional change
of root growth was a sum of a time-dependent negative gravitropic reaction and an establishment of the liminal angle, adequately
fitted the distance-angle relations. It was suggested that higher temperatures and/or a lower water potential accelerated
the diminution of the intitial negative gravitropic reaction. 相似文献
7.
Yoshiyuki Suzuki Hitoshi Sakuraba Kazuhiro Ohga 《Biochemical and biophysical research communications》1980,92(3):1066-1070
A specific elevation of cell-associated α-mannosidase was observed in human skin fibroblasts cultured with concanavalin A for 12–72 hours. There was a latency of several hours before the increase of the enzyme activity occurred. When the cells were washed with α-methylmannoside, α-mannosidase activity was not increased. Other lysosomal enzymes including β-mannosidase showed a slight decrease in activity. It was concluded that the elevation of this enzyme activity was the result of a specific binding to the cell surface mediated by concanavalin A. 相似文献
8.
Norihide Hinomoto Tomomi Higaki Junichiro Abe Masafumi Yamane Eizi Yano 《Applied Entomology and Zoology》2012,47(2):165-171
We have developed and characterized 21 microsatellite markers in the aphidophagous gall midge Aphidoletes aphidimyza (Rondani) (Diptera: Cecidomyiidae). All 21 loci tested were polymorphic: the number of alleles ranged from 2 to 17. Allelic
richness and observed heterozygosities were higher in females than in males. Several loci had no heterozygosity in males,
suggesting that the loci were located on sex chromosomes or E-chromosomes, common to cecidomyiids. The high polymorphism detected
in this study suggests the markers will be of value in analyzing genetic structure of field populations. 相似文献
9.
Dimethyl sulfide (DMS) is volatile compound important as one of the characteristic flavor compounds of marine food products. The precursor of DMS in marine products is dimethyl-β- propiothetin (DMPT), which is abundunt in green algae. DMPT was effectively extracted by the use of hydrophilic solvents from dried hitoegusa (Monostroma nitidum), a green alga. At around pH 4 and at over pH 9, the extracted DMPT was rapidly degraded to DMS; at around pH 7.5, this degradation was much slower. The DMS obtained volatilized immediately from aqueous solution. However, when the DMPT was formed into a powder with dextrin and heated to release the DMS, 40 — 60% of the DMS remained in the powder. The amount of DMS remaining was 80 % when cyclodextrin was used to form the powder. 相似文献
10.
Yoshikazu Hashida Katsuaki Takechi Tomomi Abiru Noriyuki Yabe Hiroaki Nagase Koro Hattori Susumu Takio Yoshikatsu Sato Mitsuyasu Hasebe Hirokazu Tsukaya Hiroyoshi Takano 《The Plant journal : for cell and molecular biology》2020,101(6):1318-1330
In Arabidopsis thaliana the ANGUSTIFOLIA (AN) gene regulates the width of leaves by controlling the diffuse growth of leaf cells in the medio‐lateral direction. In the genome of the moss Physcomitrella patens, we found two normal ANs (PpAN1‐1 and 1‐2). Both PpAN1 genes complemented the A. thaliana an‐1 mutant phenotypes. An analysis of spatiotemporal promoter activity of each PpAN1 gene, using transgenic lines that contained each PpAN1‐promoter– uidA (GUS) gene, showed that both promoters are mainly active in the stems of haploid gametophores and in the middle to basal region of the young sporophyte that develops into the seta and foot. Analyses of the knockout lines for PpAN1‐1 and PpAN1‐2 genes suggested that these genes have partially redundant functions and regulate gametophore height by controlling diffuse cell growth in gametophore stems. In addition, the seta and foot were shorter and thicker in diploid sporophytes, suggesting that cell elongation was reduced in the longitudinal direction, whereas no defects were detected in tip‐growing protonemata. These results indicate that both PpAN1 genes in P. patens function in diffuse growth of the haploid and diploid generations but not in tip growth. To visualize microtubule distribution in gametophore cells of P. patens, transformed lines expressing P. patens α‐tubulin fused to sGFP were generated. Contrary to expectations, the orientation of microtubules in the tips of gametophores in the PpAN1‐1/1‐2 double‐knockout lines was unchanged. The relationships among diffuse cell growth, cortical microtubules and AN proteins are discussed. 相似文献