全文获取类型
收费全文 | 2868篇 |
免费 | 164篇 |
国内免费 | 4篇 |
专业分类
3036篇 |
出版年
2023年 | 10篇 |
2022年 | 35篇 |
2021年 | 36篇 |
2020年 | 30篇 |
2019年 | 47篇 |
2018年 | 70篇 |
2017年 | 47篇 |
2016年 | 78篇 |
2015年 | 135篇 |
2014年 | 155篇 |
2013年 | 196篇 |
2012年 | 248篇 |
2011年 | 247篇 |
2010年 | 163篇 |
2009年 | 123篇 |
2008年 | 195篇 |
2007年 | 195篇 |
2006年 | 132篇 |
2005年 | 149篇 |
2004年 | 158篇 |
2003年 | 86篇 |
2002年 | 87篇 |
2001年 | 71篇 |
2000年 | 74篇 |
1999年 | 60篇 |
1998年 | 17篇 |
1997年 | 16篇 |
1996年 | 16篇 |
1995年 | 22篇 |
1994年 | 10篇 |
1993年 | 7篇 |
1992年 | 16篇 |
1991年 | 20篇 |
1990年 | 10篇 |
1989年 | 8篇 |
1988年 | 9篇 |
1987年 | 10篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1980年 | 5篇 |
1979年 | 9篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1970年 | 1篇 |
1969年 | 4篇 |
1967年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有3036条查询结果,搜索用时 8 毫秒
91.
92.
Comparative genomics of the mating-type loci of the mushroom Flammulina velutipes reveals widespread synteny and recent inversions 总被引:1,自引:0,他引:1
van Peer AF Park SY Shin PG Jang KY Yoo YB Park YJ Lee BM Sung GH James TY Kong WS 《PloS one》2011,6(7):e22249
Background
Mating-type loci of mushroom fungi contain master regulatory genes that control recognition between compatible nuclei, maintenance of compatible nuclei as heterokaryons, and fruiting body development. Regions near mating-type loci in fungi often show adapted recombination, facilitating the generation of novel mating types and reducing the production of self-compatible mating types. Compared to other fungi, mushroom fungi have complex mating-type systems, showing both loci with redundant function (subloci) and subloci with many alleles. The genomic organization of mating-type loci has been solved in very few mushroom species, which complicates proper interpretation of mating-type evolution and use of those genes in breeding programs.Methodology/Principal Findings
We report a complete genetic structure of the mating-type loci from the tetrapolar, edible mushroom Flammulina velutipes mating type A3B3. Two matB3 subloci, matB3a that contains a unique pheromone and matB3b, were mapped 177 Kb apart on scaffold 1. The matA locus of F. velutipes contains three homeodomain genes distributed over 73 Kb distant matA3a and matA3b subloci. The conserved matA region in Agaricales approaches 350 Kb and contains conserved recombination hotspots showing major rearrangements in F. velutipes and Schizophyllum commune. Important evolutionary differences were indicated; separation of the matA subloci in F. velutipes was diverged from the Coprinopsis cinerea arrangement via two large inversions whereas separation in S. commune emerged through transposition of gene clusters.Conclusions/Significance
In our study we determined that the Agaricales have very large scale synteny at matA (∼350 Kb) and that this synteny is maintained even when parts of this region are separated through chromosomal rearrangements. Four conserved recombination hotspots allow reshuffling of large fragments of this region. Next to this, it was revealed that large distance subloci can exist in matB as well. Finally, the genes that were linked to specific mating types will serve as molecular markers in breeding. 相似文献93.
Hwang IK Yoo KY Yoo DY Choi JW Lee CH Choi JH Yoon YS Won MH 《Cellular and molecular neurobiology》2011,31(5):669-674
Cyclic AMP (cAMP) response element-binding protein (CREB) is involved in memory, learning, and synaptic transmission. In this
study, we observed changes of phosphorylated CREB (pCREB) immunoreactivity and its protein levels as well as brain-derived
neurotrophic factor (BDNF) levels in the hippocampal dentate gyrus at postnatal (P) 1, 7, 14, and 21 in mice. In addition,
we also investigated pCREB expression in doublecortin (DCX, a marker for neuronal progenitors) immunoreactive neuroblasts
at P21. pCREB immunoreaction at P1 was detected in most of cells in the dentate gyrus, thereafter pCREB immunoreactivity was
decreased in all the layers of the dentate gyrus with time, however, strong pCREB immunoreactivity was shown in cells confined
to the subgranular zone of the dentate gyrus at P21. In this group, many pCREB immunoreactive cells were co-localized with
DCX immunoreactive neuroblasts. In addition, pCREB protein levels were decreased with age, showing that their levels were
very low at P21, while BDNF protein levels were increased with age. These results suggest that pCREB may play important roles
in functional maturity of granule cells in mice. 相似文献
94.
Ji?Won?Lee Eun?Jung?Lee Seung?Sik?Yoo Sung?Hoon?Park Hee?Sook?Kim Eun?Yeol?LeeEmail author 《Biotechnology and Bioprocess Engineering》2003,8(5):306-308
Enantioselective hydrolysis for the production of chiral styrene oxide was investigated using the epoxide hydrolase activity
of a newly isolatedRhodosporidium kratochvilovae SYU-08. The effects of reaction prameters—buffer type, pH, temperature, initial substrate concentrations, phenyl-1,2-ethanediol
concentrations on hydrolysis rate, and enantioselectivity—were analyzed. Optically active (S)-styrene oxide with an enantiomeric excess higher than 99 % was obtained from its racemate with a yield of 38 % (theoretically
50% maximum yield) from an initial concentration of 80 mM. 相似文献
95.
Artemisia annua hairy roots were grown in liquid-phase bubble column and gas-phase nutrient mist reactors. In most cases the bubble column reactor accumulated more biomass than the mist reactor; the highest final biomass concentrations observed were 15.3 g DW/L in the bubble column reactor and 14.4 g DW/L in the mist reactor. Further analysis showed that the average specific growth rate in the mist reactors was essentially constant and independent of the biomass concentration at the beginning of the mist mode. In contrast, at low packing densities the average growth rate in the bubble column reactors was higher than in the mist reactors, decreasing to comparable rates at high packing densities. Finally, an aerosol deposition model was used to compare the volume of medium captured by the root bed in the mist reactor to the volume of medium required to maintain a specified growth rate. The results suggest that under the current operating conditions, lower growth rates in the mist reactor may be due to insufficient nutrient availability. 相似文献
96.
Double-stranded RNA unwinding and modifying activity is detected ubiquitously in primary tissues and cell lines. 总被引:15,自引:4,他引:15 下载免费PDF全文
R W Wagner C Yoo L Wrabetz J Kamholz J Buchhalter N F Hassan K Khalili S U Kim B Perussia F A McMorris et al. 《Molecular and cellular biology》1990,10(10):5586-5590
A double-stranded RNA unwinding and modifying activity was found to be present in a wide range of tissues and cell types. The level of activity did not vary significantly with respect to the state of cell differentiation, cell cycle, or transformation. Thus, the unwinding and modifying activity, localized in the nucleus in somatic cells and capable of converting many adenosine residues to inosine, appears to be one of the housekeeping genes. 相似文献
97.
The Calvin cycle enzyme pentose-5-phosphate 3-epimerase is encoded within the cfx operons of the chemoautotroph Alcaligenes eutrophus. 总被引:2,自引:0,他引:2 下载免费PDF全文
Several genes (cfx genes) encoding Calvin cycle enzymes in Alcaligenes eutrophus are organized in two highly homologous operons comprising at least 11 kb. One cfx operon is located on the chromosome; the other is located on megaplasmid pHG1 of the organism (B. Bowien, U. Windh?vel, J.-G. Yoo, R. Bednarski, and B. Kusian, FEMS Microbiol. Rev. 87:445-450, 1990). Corresponding regions of about 2.7 kb from within the operons were sequenced. Three open reading frames, designated cfxX (954 bp), cfxY (765 bp), and cfxE (726 bp), were detected at equivalent positions in the two sequences. The nucleotide identity of the sequences amounted to 94%. Heterologous expression of the subcloned pHG1-encoded open reading frames in Escherichia coli suggested that they were functional genes. The observed sizes of the gene products CfxX (35 kDa), CfxY (27 kDa), and CfxE (25.5 kDa) closely corresponded to the values calculated on the basis of the sequence information. E. coli clones harboring the cfxE gene showed up to about 19-fold-higher activities of pentose-5-phosphate 3-epimerase (PPE; EC 5.1.3.1) than did reference clones, suggesting that cfxE encodes PPE, another Calvin cycle enzyme. These data agree with the finding that in A. eutrophus, PPE activity is significantly enhanced under autotrophic growth conditions which lead to a derepression of the cfx operons. No functions could be assigned to CfxX and CfxY. 相似文献
98.
Summary The cloning of glucoamylase geneSTA using theSUC2 promoter intoSaccharomyces cerevisiae was performed. The signal sequence ofSTA gene was used for the secretion of glucoamylase protein. The plasmid constructed in this way was named YEpSUCSTA and its expression was identified. The expression of YEpSUCSTA was repressed in the presence of glucose in growth medium, but derepressed when glucose became depleted. YEpSUCSTA showed the similar efficiency of glucoamylase secretion as YEpSTA-F which has the entireSTA gene. Glucoamylase activity in starch-glucose medium was largely increased because cell mass and plasmid stability were high in biosynthesis phase compared to extracellular glucoamylase activities in media which starch or glucose was the only carbon source. 相似文献
99.
100.
Woosuk Kim Dae Won Kim Hoon Jae Jeong Dae Young Yoo Hyo Young Jung Sung Min Nam Jong Hwi Kim Jung Hoon Choi Moo-Ho Won Yeo Sung Yoon Seung Myung Moon Soo Young Choi In Koo Hwang 《Neurochemical research》2014,39(1):187-193
The DJ-1 gene is highly conserved in diverse species and DJ-1 is known as an anti-oxidative stress factor. In this study, we investigated the neuroprotective effects of DJ-1 against ischemic damage in the rabbit spinal cord. Tat-DJ-1 fusion proteins were constructed to facilitate the penetration of DJ-1 protein into the neurons. Tat-1-DJ-1 fusion protein was administered to the rabbit 30 min after ischemia/reperfusion, and transient spinal cord ischemia was induced by occlusion of the aorta at the subrenal region for 15 min. The administration of Tat-DJ-1 significantly improved the Tarlov score compared to that in the Tat (vehicle)-treated group at 24, 48 and 72 h after ischemia/reperfusion. At 72 h after ischemia/reperfusion, the number of cresyl violet-positive neurons was significantly increased in the Tat-DJ-1-treated group compared to that in the vehicle-treated group. Lipid peroxidation as judged from the malondialdehyde levels was significantly decreased in the Tat-DJ-1-treated group compared to that in the vehicle-treated group. In contrast, superoxide dismutase and catalase levels were significantly increased in the Tat-DJ-1-treated group compared to that in the vehicle-treated group. This result suggests that DJ-1 protects neurons from ischemic damage in the ventral horn of the spinal cord via its antioxidant effects. 相似文献