全文获取类型
收费全文 | 25850篇 |
免费 | 2134篇 |
国内免费 | 2163篇 |
专业分类
30147篇 |
出版年
2024年 | 66篇 |
2023年 | 357篇 |
2022年 | 826篇 |
2021年 | 1355篇 |
2020年 | 880篇 |
2019年 | 1075篇 |
2018年 | 1029篇 |
2017年 | 756篇 |
2016年 | 1080篇 |
2015年 | 1582篇 |
2014年 | 1868篇 |
2013年 | 1971篇 |
2012年 | 2388篇 |
2011年 | 2053篇 |
2010年 | 1299篇 |
2009年 | 1040篇 |
2008年 | 1414篇 |
2007年 | 1192篇 |
2006年 | 1071篇 |
2005年 | 904篇 |
2004年 | 754篇 |
2003年 | 639篇 |
2002年 | 583篇 |
2001年 | 491篇 |
2000年 | 380篇 |
1999年 | 431篇 |
1998年 | 257篇 |
1997年 | 219篇 |
1996年 | 256篇 |
1995年 | 205篇 |
1994年 | 253篇 |
1993年 | 152篇 |
1992年 | 220篇 |
1991年 | 183篇 |
1990年 | 174篇 |
1989年 | 113篇 |
1988年 | 83篇 |
1987年 | 76篇 |
1986年 | 50篇 |
1985年 | 63篇 |
1984年 | 48篇 |
1983年 | 39篇 |
1982年 | 37篇 |
1981年 | 24篇 |
1980年 | 16篇 |
1979年 | 25篇 |
1977年 | 15篇 |
1976年 | 16篇 |
1975年 | 15篇 |
1973年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
Deep RNA-Seq uncovers the peach transcriptome landscape 总被引:3,自引:0,他引:3
Lu Wang Shuang Zhao Chao Gu Ying Zhou Hui Zhou Juanjuan Ma Jun Cheng Yuepeng Han 《Plant molecular biology》2013,83(4-5):365-377
993.
Yan Geng Zhe He Zhen-Ming Lu Hong-Yu Xu Guo-Hua Xu Jin-Song Shi Zheng-Hong Xu 《Applied microbiology and biotechnology》2013,97(7):2851-2858
Antrodia camphorata is a well-known Chinese medicinal mushroom that protects against diverse health-related conditions. Submerged fermentation of A. camphorata is an alternative choice for the effective production of bioactive metabolites, but the effects of nutrition and environment on mycelial morphology are largely unknown. In this study, we show that A. camphorata American Type Culture Collection 200183 can form arthrospores in the end of liquid fermentation. Different morphologies of A. camphorata in submerged culture were analyzed using scanning electron microscopy. The optimal carbon and nitrogen sources for sporulation were soluble starch and yeast extract. We found that a carbon-to-nitrogen ratio (C/N) of 40:1, MgSO4 (0.5 g/l), KH2PO4 (3.0 g/l), an initial pH?5.0, and an inoculum size of 1.5?×?105 spores/ml led to maximum production of arthroconidia. Our results will be useful in the regulation and optimization of A. camphorata cultures for efficient production of arthroconidia in submerged culture, which can be used as inocula in subsequent fermentation processes. 相似文献
994.
Aiqiu Liu Xiaoming Tan Lun Yao Xuefeng Lu 《Applied microbiology and biotechnology》2013,97(15):7061-7071
Although successful production of fatty alcohols in metabolically engineered Escherichia coli with heterologous expression of fatty acyl-CoA reductase has been reported, low biosynthetic efficiency is still a hurdle to be overcome. In this study, we examined the characteristics of two fatty acyl-CoA reductases encoded by Maqu_2220 and Maqu_2507 genes from Marinobacter aquaeolei VT8 on fatty alcohol production in E. coli. Fatty alcohols with diversified carbon chain length were obtained by co-expressing Maqu_2220 with different carbon chain length-specific acyl-ACP thioesterases. Both fatty acyl-CoA reductases displayed broad substrate specificities for C12–C18 fatty acyl chains in vivo. The optimized mutant strain of E. coli carrying the modified tesA gene and fadD gene from E. coli and Maqu_2220 gene from Marinobacter aquaeolei VT8 produced fatty alcohols at a remarkable level of 1.725 g/L under the fermentation condition. 相似文献
995.
Xiaofei Ji Xinfeng Bai Zhe Li Sen Wang Zhiwei Guan Xuemei Lu 《Applied microbiology and biotechnology》2013,97(16):7317-7324
Cytophaga hutchinsonii is an aerobic cellulolytic gliding bacterium. The mechanism of its cell motility over surfaces without flagella and type IV pili is not known. In this study, mariner-based transposon mutagenesis was used to identify a new locus CHU_1797 essential for colony spreading on both hard and soft agar surfaces through gliding. CHU_1797 encodes a putative outer membrane protein of 348 amino acids with unknown function, and proteins which have high sequence similarity to CHU_1797 were widespread in the members of the phylum Bacteroidetes. The disruption of CHU_1797 suppressed spreading toward glucose on an agar surface, but had no significant effect on cellulose degradation for cells already in contact with cellulose. SEM observation showed that the mutant cells also regularly arranged on the surface of cellulose fiber similar with that of the wild type strain. These results indicated that the colony spreading ability on agar surfaces was not required for cellulose degradation by C. hutchinsonii. This was the first study focused on the relationship between cell motility and cellulose degradation of C. hutchinsonii. 相似文献
996.
Profiling of dynamic changes in the microbial community during the soy sauce fermentation process 总被引:1,自引:0,他引:1
Quanzeng Wei Hongbin Wang Zhixin Chen Zhijia Lv Yufeng Xie Fuping Lu 《Applied microbiology and biotechnology》2013,97(20):9111-9119
Soy sauce is a traditional condiment manufactured by natural inoculation and mixed culture fermentation. As is well known, it is the microbial community that plays an important role in the formation of its flavors. However, to date, its dynamic changes during the long period of fermentation process are still unclear, intensively constraining the improvement and control of the soy sauce quality. In this work, we revealed the dynamic changes of the microbial community by combining a cultured dependent method and a cultured independent method of polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis. Results indicated that the two methods verified and complemented each other in profiling microbial community, and that significant dynamics of the microbial community existed during the fermentation process, especially the strong inhibition of the growth of most of the microbes when entering into the mash stage from the koji stage. In the analysis of bacterial community, Staphylococcus and Bacillus were found to be the dominant bacteria and detected in the whole fermentation process. Kurthia and Klebsiella began to appear in the koji stage and then fade away in the early stage of the mash fermentation. In the analysis of fungal community, Aspergillus sojae and Zygosaccharomyces rouxii were found to be the dominant fungi in the koji and mash fermentation, respectively. It was clearly shown that when A. sojae decreased and disappeared in the middle stage of the mash fermentation, Z. rouxii appeared and increased at the meantime. Aspergillus parasiticus, Trichosporon ovoides and Trichosporon asahii also appeared in the koji and the early period of the mash fermentation and disappeared thereafter. Similar to Z. rouxii, Millerozyma farinosa and Peronospora farinosa were also found spontaneously which appeared in the mid-late period of the mash fermentation. The principal component analysis suggested that the microbial community underwent significant changes in the early period of the fermentation and, thereafter, tended to the stabilization in the mid-late periods. This study gave us important clues to understand the fermentation process and can serve as a foundation for improving the quality of soy sauce in the future. 相似文献
997.
Haiqiang Lu Huitu Zhang Pengjun Shi Huiying Luo Yaru Wang Peilong Yang Bin Yao 《Applied microbiology and biotechnology》2013,97(18):8121-8128
A novel β-mannanase gene, man5XZ7, was cloned from thermophilic fungus Thielavia arenaria XZ7, and successfully expressed in Pichia pastoris. The gene (1,110 bp) encodes a 369-amino acid polypeptide with a molecular mass of approximately 40.8 kDa. The deduced sequence of Man5XZ7 consists of a putative 17-residue signal peptide and a catalytic module belonging to glycoside hydrolase (GH) family 5, and displays 76 % identity with the experimentally verified GH 5 endo-β-1,4-mannanase from Podospora anserina. Recombinant Man5XZ7 was optimally active at 75 °C and pH?5.0 and exhibited high activity at a wide temperature range (>50.0 % activity at 50–85 °C). Moreover, it had good adaptability to acidic to basic pH (>74.1 % activity at pH?4.0–7.0 and 25.6 % even at pH?9.0) and good stability from pH?3.0 to 10.0. These enzymatic properties showed that Man5XZ7 was a new thermophilic and alkali-tolerant β-mannanase. Further amino acid composition analysis indicated that Man5XZ7 has several characteristic features of thermophilic enzymes. 相似文献
998.
The group 1 pathogenesis-related (PR-1) proteins have long been considered hallmarks of hypersensitive response/defense pathways in plants, but their biochemical functions are still obscure despite resolution of the NMR/X-ray structures of several PR-1-like proteins, including P14a (the prototype PR-1). We report here the characterization of two basic PR-1 proteins (PR-1-1 and PR-1-5) recently identified from hexaploid wheat (Triticum aestivum). Both proteins were expressed in Pichia pastoris as a single major species of ∼15 kDa. Sequence identity of the expressed PR-1 proteins was verified by MALDI-TOF/TOF analysis. Accumulation of the native PR-1-5 protein in pathogen-challenged wheat was confirmed by protein gel blot analysis. Low-temperature SDS-PAGE and yeast two-hybrid assays revealed that PR-1-1 exists primarily as a monomer whereas PR-1-5 forms homodimers. Both PR-1 proteins are resistant to proteases compared to bovine serum albumin, but PR-1-1 shows resistance mainly to subtilisin and protease K (serine proteases) whereas PR-1-5 shows resistance to subtilisin, protease K and papain (a cysteine protease). Site-specific mutations at the five putative active sites in the PR-1 domain all affected dimerization, with the mutations at Glu-72 and Glu-102 (in the PR-1-5 numeration) also diminishing protease resistance. Sequence analysis revealed that the Glu-72 and Glu-102 residues are located in motif-like sequences that are conserved in both PR-1 and the human apoptosis-related caspase proteins. These findings prompt us to examine the function of PR-1 for a role in protease-mediated programmed cell death pathways in plants. 相似文献
999.
Yonghai Liu Le Yu Jianhua Tong Junhui Ding Ruozhong Wang Yusheng Lu Langtao Xiao 《Journal of plant physiology》2013
The tiller of rice (Oryza sativa L.), which determines the panicle number per plant, is an important agronomic trait for grain production. Ascorbic acid (Asc) is a major plant antioxidant that serves many functions in plants. l-Galactono-1,4-lactone dehydrogenase (GLDH, EC 1.3.2.3) is an enzyme that catalyzes the last step of Asc biosynthesis in plants. Here we show that the GLDH-suppressed transgenic rices, GI-1 and GI-2, which have constitutively low (between 30% and 50%) leaf Asc content compared with the wild-type plants, exhibit a significantly reduced tiller number. Moreover, lower growth rate and plant height were observed in the Asc-deficient plants relative to the trait values of the wild-type plants at different tillering stages. Further examination showed that the deficiency of Asc resulted in a higher lipid peroxidation, a loss of chlorophyll, a loss of carotenoids, and a lower rate of CO2 assimilation. In addition, the level of abscisic acid was higher in GI-1 plants, while the level of jasmonic acid was higher in GI-1 and GI-2 plants at different tillering stages. The results we presented here indicated that Asc deficiency was likely responsible for the promotion of premature senescence, which was accompanied by a marked decrease in photosynthesis. These observations support the conclusion that the deficiency of Asc alters the tiller number in the GLDH-suppressed transgenics through promoting premature senescence and changing phytohormones related to senescence. 相似文献
1000.
Yongfeng He Hangun Kim Taeyong Ryu Youra Kang Jeong-Ae Kim Bo-Hyun Kim Jae-Hyuk Lee Keonwook Kang Qun Lu Kwonseop Kim 《FEBS letters》2013,587(2):193-199
This study revealed that CWR22Rv-1 cells overexpressing δ-catenin display bigger tumor formation and higher angiogenic potentials than their matched control cells in the CAM assay. In addition, δ-catenin overexpression in CWR22Rv-1 cells results in increased hypoxia-inducible factor 1-alpha (HIF-1α and vascular endothelial growth factor (VEGF) expression. Furthermore, δ-catenin overexpression was found to enhance nuclear distribution of both β-catenin and HIF-1α in hypoxic condition, which is diminished by knockdown of δ-catenin. Our current study adds novel evidence regarding contribution of δ-catenin to the progression of prostate cancer. 相似文献