首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   723篇
  免费   44篇
  2022年   6篇
  2021年   9篇
  2019年   6篇
  2018年   11篇
  2017年   5篇
  2016年   12篇
  2015年   21篇
  2014年   24篇
  2013年   39篇
  2012年   47篇
  2011年   38篇
  2010年   27篇
  2009年   27篇
  2008年   31篇
  2007年   28篇
  2006年   40篇
  2005年   39篇
  2004年   42篇
  2003年   50篇
  2002年   31篇
  2001年   14篇
  2000年   19篇
  1999年   24篇
  1998年   6篇
  1997年   8篇
  1996年   3篇
  1995年   3篇
  1994年   2篇
  1993年   6篇
  1992年   9篇
  1991年   12篇
  1990年   11篇
  1989年   7篇
  1988年   11篇
  1987年   7篇
  1986年   7篇
  1985年   10篇
  1984年   10篇
  1983年   7篇
  1982年   5篇
  1981年   5篇
  1980年   6篇
  1979年   8篇
  1978年   4篇
  1977年   3篇
  1976年   2篇
  1975年   6篇
  1974年   6篇
  1972年   2篇
  1971年   2篇
排序方式: 共有767条查询结果,搜索用时 218 毫秒
31.
In order to reduce the cost of bioethanol production from lignocellulosic biomass, we conferred the ability to ferment cellulosic materials directly on Zymobacter palmae by co-expressing foreign endoglucanase and β-glucosidase genes. Z. palmae is a novel ethanol-fermenting bacterium capable of utilizing a broad range of sugar substrates, but not cellulose. Therefore, the six genes encoding the cellulolytic enzymes (CenA, CenB, CenD, CbhA, CbhB, and Cex) from Cellulomonas fimi were introduced and expressed in Z. palmae. Of these cellulolytic enzyme genes cloned, CenA degraded carboxymethylcellulose and phosphoric acid-swollen cellulose (PASC) efficiently. The extracellular CenA catalyzed the hydrolysis of barley β-glucan and PASC to liberate soluble cello-oligosaccharides, indicating that CenA is the most suitable enzyme for cellulose degradation among those cellulolytic enzymes expressed in Z. palmae. Furthermore, the cenA gene and β-glucosidase gene (bgl) from Ruminococcus albus were co-expressed in Z. palmae. Of the total endoglucanase and β-glucosidase activities, 57.1 and 18.1 % were localized in the culture medium of the strain. The genetically engineered strain completely saccharified and fermented 20 g/l barley β-glucan to ethanol within 84 h, producing 79.5 % of the theoretical yield. Thus, the production and secretion of CenA and BGL enabled Z. palmae to efficiently ferment a water-soluble cellulosic polysaccharide to ethanol.  相似文献   
32.
N-Benzoylgiycine amidohydrolase (hippurate hydrolase EC 3.5.1.32), which catalyzes the hydrolysis of hippuric acid to benzoic acid and glycine, was found in a cell-free extract of Pseudomonas putida C692-3 grown on a medium containing hippuric acid. The enzyme was purified from the extract by ammonium sulfate fractionation and column chromatographies on DEAE-cellulose, DEAE-Sephadex A-50, hydroxyapatite, and Sepharose CL-6B. The enzyme was finally crystallized. The crystalline enzyme was almost homogeneous on electrophoresis. The enzyme had a molecular weight of about 170,000 and consisted of four subunits identical in molecular weight (approximately 42,000). The enzyme hydrolyzed N-benzoylglycine most rapidly, and N-benzoyl-l-alanine and N-benzoyl-l-aminobutyric acid. The Km value for these substrates were 0.72 mm, 0.87 mm, and 0.87mm, respectively. The optimum pH of the enzyme reaction was 7.0 to 8.0 and the enzyme was stable from pH 6.0 to 8.0.  相似文献   
33.
34.
35.
36.
Marine Biotechnology - Most mammals, including humans, show obvious aging phenotypes, for example, loss of tissue plasticity and sarcopenia. In this regard, fish can be attractive models to study...  相似文献   
37.
A majority of the potential health benefits of green tea, including the potential to prevent cognitive decline, have been attributed to epigallocatechin gallate (EGCG). Sunrouge is a green tea cultivar that contains EGCG and several other bioactive components such as quercetin, myricetin, cyanidin and delphinidin. We compared the effects of Sunrouge and Yabukita, the most popular Japanese green tea cultivar, on cognitive function in the senescence-accelerated mouse Prone8. These mice were fed an experimental diet containing Sunrouge extract (SRE) or Yabukita extract (YBE). SRE feeding significantly prevented cognitive decline, whereas YBE feeding had little effect. Moreover, SRE feeding prevented elevation of the amyloid-β42 level while improving the gene expression of neprilysin and decreasing beta-site APP-cleaving enzyme 1 in the brain. These preventive effects of SRE against cognitive decline were attributed to the characteristic composition of Sunrouge and strongly suggest that consumption of this cultivar could protect against age-related cognitive decline.  相似文献   
38.
MIG-seq (Multiplexed inter-simple sequence repeats genotyping by sequencing) has been developed as a low cost genotyping technology, although the number of polymorphisms obtained is assumed to be minimal, resulting in the low application of this technique to analyses of agricultural plants. We applied MIG-seq to 12 plant species that include various crops and investigated the relationship between genome size and the number of bases that can be stably sequenced. The genome size and the number of loci, which can be sequenced by MIG-seq, are positively correlated. This is due to the linkage between genome size and the number of simple sequence repeats (SSRs) through the genome. The applicability of MIG-seq to population structure analysis, linkage mapping, and quantitative trait loci (QTL) analysis in wheat, which has a relatively large genome, was further evaluated. The results of population structure analysis for tetraploid wheat showed the differences among collection sites and subspecies, which agreed with previous findings. Additionally, in wheat biparental mapping populations, over 3,000 SNPs/indels with low deficiency were detected using MIG-seq, and the QTL analysis was able to detect recognized flowering-related genes. These results revealed the effectiveness of MIG-seq for genomic analysis of agricultural plants with large genomes, including wheat.  相似文献   
39.
Characterization of the carp myosin heavy chain multigene family   总被引:3,自引:0,他引:3  
Kikuchi K  Muramatsu M  Hirayama Y  Watabe S 《Gene》1999,228(1-2):189-196
We isolated partial coding sequences for 29 carp myosin heavy chain genes (MyoHCs) and determined the nucleotide sequences around the region encoding the loop 2 of the myosin molecule. The predicted amino acid sequences from the isolated genes all showed very high similarity to those of skeletal and cardiac muscles from higher vertebrates, but not to those of smooth and non-muscle counterparts. Among all clones isolated, carp MyoHC10, MyoHCI-1-3 and MyoHC30 showed exon-nucleotide sequences identical to those of cDNAs encoding the loop 2 region of the 10 degrees C-, intermediate- and 30 degrees C-type fast skeletal isoforms [Hirayama and Watabe, Euro. J. Biochem. 246 (1997) 380-387]. The loop 2 of 28 types of carp MyoHCs was encoded by two exons separated by an intron corresponding to that of the 16th in higher vertebrate MyoHCs, whilst this intron was not found in carp MyoHC30. Although carp MyoHC30 had a gene organization different from those of higher vertebrates and other carp MyoHCs, its predicted amino acid sequence for loop 2 showed the highest homology to those of higher vertebrates among carp MyoHCs. In the 28 carp MyoHCs containing the intron, a combination of different nucleotide sequences for the two resulted in 14 distinct series for the combined coding sequence. These different nucleotide sequences encoded nine distinct amino acid sequences. Phylogenetic analysis for the present loop 2 and light meromyosin previously reported for carp MyoHCs [Imai et al., J. Exp. Biol. 200 (1997) 27-34] revealed that carp MyoHCs have recently diverged and are more closely related to each other than to MyoHCs from other species.  相似文献   
40.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号