全文获取类型
收费全文 | 40998篇 |
免费 | 2373篇 |
国内免费 | 5189篇 |
出版年
2024年 | 77篇 |
2023年 | 599篇 |
2022年 | 887篇 |
2021年 | 1166篇 |
2020年 | 1055篇 |
2019年 | 1366篇 |
2018年 | 1108篇 |
2017年 | 1037篇 |
2016年 | 1113篇 |
2015年 | 1403篇 |
2014年 | 2065篇 |
2013年 | 2791篇 |
2012年 | 1972篇 |
2011年 | 2095篇 |
2010年 | 1764篇 |
2009年 | 2037篇 |
2008年 | 2237篇 |
2007年 | 2386篇 |
2006年 | 2376篇 |
2005年 | 2206篇 |
2004年 | 2030篇 |
2003年 | 1885篇 |
2002年 | 1716篇 |
2001年 | 1362篇 |
2000年 | 1118篇 |
1999年 | 1068篇 |
1998年 | 954篇 |
1997年 | 833篇 |
1996年 | 770篇 |
1995年 | 733篇 |
1994年 | 709篇 |
1993年 | 508篇 |
1992年 | 442篇 |
1991年 | 379篇 |
1990年 | 325篇 |
1989年 | 242篇 |
1988年 | 248篇 |
1987年 | 217篇 |
1986年 | 182篇 |
1985年 | 181篇 |
1984年 | 202篇 |
1983年 | 124篇 |
1982年 | 140篇 |
1981年 | 85篇 |
1980年 | 93篇 |
1979年 | 71篇 |
1978年 | 50篇 |
1977年 | 33篇 |
1976年 | 44篇 |
1974年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Jesus Torres-Bacete Prem Kumar Sinha Motoaki Sato Gaurav Patki Mou-Chieh Kao Akemi Matsuno-Yagi Takao Yagi 《The Journal of biological chemistry》2012,287(51):42763-42772
The bacterial H+-translocating NADH:quinone oxidoreductase (NDH-1) catalyzes electron transfer from NADH to quinone coupled with proton pumping across the cytoplasmic membrane. The NuoK subunit (counterpart of the mitochondrial ND4L subunit) is one of the seven hydrophobic subunits in the membrane domain and bears three transmembrane segments (TM1–3). Two glutamic residues located in the adjacent transmembrane helices of NuoK are important for the energy coupled activity of NDH-1. In particular, mutation of the highly conserved carboxyl residue (KGlu-36 in TM2) to Ala led to a complete loss of the NDH-1 activities. Mutation of the second conserved carboxyl residue (KGlu-72 in TM3) moderately reduced the activities. To clarify the contribution of NuoK to the mechanism of proton translocation, we relocated these two conserved residues. When we shifted KGlu-36 along TM2 to positions 32, 38, 39, and 40, the mutants largely retained energy transducing NDH-1 activities. According to the recent structural information, these positions are located in the vicinity of KGlu-36, present in the same helix phase, in an immediately before and after helix turn. In an earlier study, a double mutation of two arginine residues located in a short cytoplasmic loop between TM1 and TM2 (loop-1) showed a drastic effect on energy transducing activities. Therefore, the importance of this cytosolic loop of NuoK (KArg-25, KArg-26, and KAsn-27) for the energy transducing activities was extensively studied. The probable roles of subunit NuoK in the energy transducing mechanism of NDH-1 are discussed. 相似文献
52.
Planar cell polarity (PCP) controls the orientation of cells within tissues and the polarized outgrowth of cellular appendages. So far, six PCP core proteins including the transmembrane proteins Frizzled (Fz), Strabismus (Stbm) and Flamingo (Fmi) have been identified. These proteins form asymmetric PCP domains at apical junctions of epithelial cells. Here, we demonstrate that VhaPRR, an accessory subunit of the proton pump V‐ATPase, directly interacts with the protocadherin Fmi through its extracellular domain. It also shows a striking co‐localization with PCP proteins during all pupal wing stages in Drosophila. This localization depends on intact PCP domains. Reversely, VhaPRR is required for stable PCP domains, identifying it as a novel PCP core protein. VhaPRR performs an additional role in vesicular acidification as well as endolysosomal sorting and degradation. Membrane proteins, such as E‐Cadherin and the Notch receptor, accumulate at the surface and in intracellular vesicles of cells mutant for VhaPRR. This trafficking defect is shared by other V‐ATPase subunits. By contrast, the V‐ATPase does not seem to have a direct role in PCP regulation. Together, our results suggest two roles for VhaPRR, one for PCP and another in endosomal trafficking. This dual function establishes VhaPRR as a key factor in epithelial morphogenesis. 相似文献
53.
《Bioscience, biotechnology, and biochemistry》2013,77(5):1190-1198
The Rhynchosciara americana C3-22 gene is located in an amplified domain and is developmentally expressed. The aim of the present work was to identify intrinsically bent DNA sites in a segment containing the gene promoter and downstream sequence. The results indicated that this gene is flanked by intrinsically bent DNA sites. Three bent DNA sites (b?3, b?2, and b?1) were localized in the promoter, and one was localized downstream of the gene (b+1). These sites had helical parameters that confirmed the curved structure, as well as segments with left-handed superhelical writhe. In silico analysis of the promoters of four other insect genes, which encode secreted polypeptides, showed that they all had curved structures and similar helical parameters. Correlation with other results indicates that the detected intrinsically bent DNA sites that flank the C3-22 gene might be a consensus feature of the gene structure in the amplified domains. 相似文献
54.
Global species delimitation and phylogeography of the circumtropical ‘sexy shrimp’ Thor amboinensis reveals a cryptic species complex and secondary contact in the Indo‐West Pacific
下载免费PDF全文
![点击此处可从《Journal of Biogeography》网站下载免费的PDF全文](/ch/ext_images/free.gif)
55.
56.
《Bioscience, biotechnology, and biochemistry》2013,77(12):2758-2761
A group I intron that can be spliced in vivo and in vitro was identified in the flagellin gene of the thermophilic bacterium Geobacillus stearothermophilus. We also found one or two intervening sequences (IVS) of flagellin genes in five additional bacterial species. Furthermore, we report the presence of these sequences in two sites of a highly conserved region in the flagellin gene. 相似文献
57.
58.
A gene of Penicillium funiculosum encoding an endoglucanase was cloned and expressed in Escherichia coli using the lacZ promoter of vector pUC 18. The gene product hydrolyzed carboxymethyl cellulose and showed strong cross reactivity with P. funiculosum anticellulases. 相似文献
59.
60.