全文获取类型
收费全文 | 3378篇 |
免费 | 195篇 |
出版年
2023年 | 21篇 |
2022年 | 47篇 |
2021年 | 89篇 |
2020年 | 70篇 |
2019年 | 72篇 |
2018年 | 104篇 |
2017年 | 93篇 |
2016年 | 124篇 |
2015年 | 158篇 |
2014年 | 206篇 |
2013年 | 251篇 |
2012年 | 319篇 |
2011年 | 286篇 |
2010年 | 177篇 |
2009年 | 137篇 |
2008年 | 210篇 |
2007年 | 171篇 |
2006年 | 185篇 |
2005年 | 159篇 |
2004年 | 125篇 |
2003年 | 112篇 |
2002年 | 88篇 |
2001年 | 24篇 |
2000年 | 14篇 |
1999年 | 19篇 |
1998年 | 18篇 |
1997年 | 19篇 |
1996年 | 14篇 |
1995年 | 10篇 |
1994年 | 12篇 |
1992年 | 11篇 |
1991年 | 9篇 |
1990年 | 13篇 |
1989年 | 9篇 |
1988年 | 9篇 |
1986年 | 13篇 |
1985年 | 9篇 |
1984年 | 12篇 |
1983年 | 12篇 |
1982年 | 10篇 |
1980年 | 17篇 |
1977年 | 10篇 |
1976年 | 7篇 |
1975年 | 7篇 |
1974年 | 8篇 |
1973年 | 7篇 |
1972年 | 8篇 |
1971年 | 10篇 |
1969年 | 9篇 |
1964年 | 7篇 |
排序方式: 共有3573条查询结果,搜索用时 15 毫秒
991.
992.
993.
Blaby IK Majumder M Chatterjee K Jana S Grosjean H de Crécy-Lagard V Gupta R 《RNA (New York, N.Y.)》2011,17(7):1367-1380
Pseudouridine (Ψ), the isomer of uridine, is commonly found at various positions of noncoding RNAs of all organisms. Ψ residues are formed by a number of single- or multisite specific Ψ synthases, which generally act as stand-alone proteins. In addition, in Eukarya and Archaea, specific ribonucleoprotein complexes, each containing a distinct box H/ACA guide RNA and four core proteins, can produce Ψ at many sites of different cellular RNAs. Cbf5 is the core Ψ synthase in these complexes. Using Haloferax volcanii as an archaeal model organism, we show that, contrary to eukaryotes, the Cbf5 homolog (HVO_2493) is not essential in this archaeon. The Cbf5-deleted strain of H. volcanii completely lacks Ψ at positions 1940, 1942, 2605, and 2591 (Escherichia coli positions 1915, 1917, 2572, and 2586) of its 23S rRNA, and contains reduced steady-state levels of some box H/ACA RNAs. Archaeal Cbf5 is known to have tRNA Ψ55 synthase activity in vitro but we could not confirm this activity in vivo in H. volcanii. Conversely, the Pus10 (previously PsuX) homolog (HVO_1979), which can produce tRNA Ψ55, as well as Ψ54 in vitro, is shown here to be essential in H. volcanii, whereas the corresponding tRNA Ψ55 synthases, Pus4 and TruB, are not essential in yeast and E. coli, respectively. Finally, we demonstrate that HVO_1852, the TruA/Pus3 homolog, is responsible for the pseudouridylation of position 39 in H. volcanii tRNAs and that the corresponding gene is not essential. 相似文献
994.
Thanabalasundaram G Schneidewind J Pieper C Galla HJ 《The international journal of biochemistry & cell biology》2011,43(9):1284-1293
The blood-brain barrier consists of the cerebral microvascular endothelium, pericytes, astrocytes and neurons. In this study we analyzed the differentiation stage dependent influence of primary porcine brain capillary pericytes on the barrier integrity of primary porcine brain capillary endothelial cells. At first, we were able to induce two distinct differentiation stages of the primary pericytes in vitro. TGFβ treated pericytes expressed more α-SMA and actin while desmin, vimentin and nestin expression was decreased when compared to bFGF induced cells. Further analysis of α-SMA revealed that most of the pericytes differentiated with TGFβ expressed functional α-SMA while only few cells expressed functional α-SMA in the presence of bFGF. In addition the permeability factors VEGF, MMP-2 and MMP-9 were higher secreted by the α-SMA positive phenotype indicating a proangiogenic role of this TGFβ induced pericyte differentiation stage. Higher level of VEGF, MMP-2 and MMP-9 were as well detected in the TGFβ pretreated pericyte coculture with endothelial cells when compared to the influence of the bFGF pretreated pericytes. The TEER measurement of the barrier integrity of endothelial cells revealed that bFGF induced α-SMA negative pericytes stabilize the barrier integrity while α-SMA positive pericytes differentiated by TGFβ decrease the barrier integrity. These results together reveal the potential of pericytes to regulate the endothelial barrier integrity in a differentiation stage dependant pathway. 相似文献
995.
Multiple myeloma (MM) is an incurable plasma cell (PC) malignancy characterized by the accumulation of monoclonal PCs in the
bone marrow. For deeper understanding of the molecular mechanisms involved in the development of this disease, the influence
of microenvironment, or the prediction of response of tumor PCs to anti-MM treatment, it is possible to use modern technologies
for genomic and proteomic analyses. Due to progress in instrumentation, one of the main tools of proteomic analysis is mass
spectrometry in combination with chosen separation techniques. This review will provide a short survey of the most commonly
used proteomic techniques and show examples of their applications in MM proteome studies. 相似文献
996.
997.
998.
Basen M Krüger M Milucka J Kuever J Kahnt J Grundmann O Meyerdierks A Widdel F Shima S 《Environmental microbiology》2011,13(5):1370-1379
Anaerobic oxidation of methane (AOM) with sulfate is catalysed by microbial consortia of archaea and bacteria affiliating with methanogens and sulfate-reducing Deltaproteobacteria respectively. There is evidence that methane oxidation is catalysed by enzymes related to those in methanogenesis, but the enzymes for sulfate reduction coupled to AOM have not been examined. We collected microbial mats with high AOM activity from a methane seep in the Black Sea. The mats consisted mainly of archaea of the ANME-2 group and bacteria of the Desulfosarcina-Desulfococcus group. Cell-free mat extract contained activities of enzymes involved in sulfate reduction to sulfide: ATP sulfurylase (adenylyl : sulfate transferase; Sat), APS reductase (Apr) and dissimilatory sulfite reductase (Dsr). We partially purified the enzymes by anion-exchange chromatography. The amounts obtained indicated that the enzymes are abundant in the mat, with Sat accounting for 2% of the soluble mat protein. N-terminal amino acid sequences of purified proteins suggested similarities to the corresponding enzymes of known species of sulfate-reducing bacteria. The deduced amino acid sequence of PCR-amplified genes of the Apr subunits is similar to that of Apr of the Desulfosarcina/Desulfococcus group. These results indicate that the major enzymes involved in sulfate reduction in the Back Sea microbial mats are of bacterial origin, most likely originating from the bacterial partner in the consortium. 相似文献
999.