全文获取类型
收费全文 | 94113篇 |
免费 | 362篇 |
国内免费 | 884篇 |
专业分类
95359篇 |
出版年
2023年 | 7篇 |
2022年 | 17篇 |
2021年 | 34篇 |
2020年 | 8篇 |
2019年 | 24篇 |
2018年 | 11863篇 |
2017年 | 10688篇 |
2016年 | 7474篇 |
2015年 | 646篇 |
2014年 | 326篇 |
2013年 | 361篇 |
2012年 | 4282篇 |
2011年 | 12871篇 |
2010年 | 12055篇 |
2009年 | 8260篇 |
2008年 | 9839篇 |
2007年 | 11393篇 |
2006年 | 294篇 |
2005年 | 547篇 |
2004年 | 1006篇 |
2003年 | 1055篇 |
2002年 | 806篇 |
2001年 | 282篇 |
2000年 | 184篇 |
1999年 | 43篇 |
1998年 | 35篇 |
1997年 | 40篇 |
1996年 | 25篇 |
1995年 | 12篇 |
1994年 | 12篇 |
1993年 | 34篇 |
1992年 | 28篇 |
1991年 | 45篇 |
1990年 | 12篇 |
1989年 | 13篇 |
1988年 | 23篇 |
1987年 | 18篇 |
1985年 | 9篇 |
1984年 | 16篇 |
1983年 | 21篇 |
1977年 | 7篇 |
1976年 | 6篇 |
1975年 | 8篇 |
1972年 | 247篇 |
1971年 | 275篇 |
1970年 | 7篇 |
1965年 | 13篇 |
1962年 | 24篇 |
1944年 | 12篇 |
1940年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Sabine Favre-Bonté Eric Chamot Thilo Köhler Jacques-A Romand Christian van Delden 《BMC microbiology》2007,7(1):33
Background
Pseudomonas aeruginosa frequently colonizes and is responsible for severe ventilator-associated pneumonia in intubated patients. A quorum-sensing (QS) circuit, depending on the production of the two QS-signaling molecules (autoinducers, AIs) 3-oxo-C12-HSL and C4-HSL, regulates the production by P. aeruginosa of several virulence factors and is required for biofilm formation. Therefore QS-inhibition has been suggested as a new target for preventive and/or therapeutic strategies. However the precise role of QS during colonization and subsequent infections of intubated patients remains unclear. 相似文献992.
Raja Noor Zaliha Raja Abd Rahman Thean Chor Leow Abu Bakar Salleh Mahiran Basri 《BMC microbiology》2007,7(1):77
Background
Thermophilic Bacillus strains of phylogenetic Bacillus rRNA group 5 were described as a new genus Geobacillus. Their geographical distribution included oilfields, hay compost, hydrothermal vent or soils. The members from the genus Geobacillus have a growth temperatures ranging from 35 to 78°C and contained iso-branched saturated fatty acids (iso-15:0, iso-16:0 and iso-17:0) as the major fatty acids. The members of Geobacillus have similarity in their 16S rRNA gene sequences (96.5–99.2%). Thermophiles harboring intrinsically stable enzymes are suitable for industrial applications. The quest for intrinsically thermostable lipases from thermophiles is a prominent task due to the laborious processes via genetic modification. 相似文献993.
Background
The ubiquitin-proteasome system is the predominant pathway for myofibrillar proteolysis but a previous study in C2C12 myotubes only observed alterations in lysosome-dependent proteolysis in response to complete starvation of amino acids or leucine from the media. Here, we determined the interaction between insulin and amino acids in the regulation of myotube proteolysis 相似文献994.
Sébastien JD Giroux Celmar Alves-Leiva Yann Lécluse Patrick Martin Olivier Albagli Isabelle Godin 《BMC developmental biology》2007,7(1):79
Background
Hematopoietic development in vertebrate embryos results from the sequential contribution of two pools of precursors independently generated. While intra-embryonic precursors harbour the features of hematopoietic stem cells (HSC), precursors formed earlier in the yolk sac (YS) display limited differentiation and self-renewal potentials. The mechanisms leading to the generation of the precursors in both sites are still largely unknown, as are the molecular basis underlying their different potential. A possible approach to assess the role of candidate genes is to transfer or modulate their expression/activity in both sites. We thus designed and compared transduction protocols to target either native extra-embryonic precursors, or hematopoietic precursors. 相似文献995.
996.
997.
Ping-Yen Chen Wun-Shaing W Chang Ruey-Hwang Chou Yiu-Kay Lai Sheng-Chieh Lin Chia-Yi Chi Cheng-Wen Wu 《BMC molecular biology》2007,8(1):2
Background
Despite of the fact that mammalian genomes are far more spacious than prokaryotic genomes, recent nucleotide sequencing data have revealed that many mammalian genes are arranged in a head-to-head orientation and separated by a small intergenic sequence. Extensive studies on some of these neighboring genes, in particular homologous gene pairs, have shown that these genes are often co-expressed in a symmetric manner and regulated by a shared promoter region. Here we report the identification of two non-homologous brain disease-related genes, with one coding for a serine protease inhibitor (SERPINI1) and the other for a programmed cell death-related gene (PDCD10), being tightly linked together by an asymmetric bidirectional promoter in an evolutionarily conserved fashion. This asymmetric bidirectional promoter, in cooperation with some cis-acting elements, is responsible for the co-regulation of the gene expression pattern as well as the tissue specificity of SERPINI1 and PDCD10. 相似文献998.
Shunpu Zhang 《BMC bioinformatics》2007,8(1):230
Background
The Significance Analysis of Microarrays (SAM) is a popular method for detecting significantly expressed genes and controlling the false discovery rate (FDR). Recently, it has been reported in the literature that the FDR is not well controlled by SAM. Due to the vast application of SAM in microarray data analysis, it is of great importance to have an extensive evaluation of SAM and its associated R-package (sam2.20). 相似文献999.
Background
The arginine-vasopressin 1a receptor has been identified as a key determinant for social behaviour in Microtus voles, humans and other mammals. Nevertheless, the genetic bases of complex phenotypic traits like differences in social and mating behaviour among species and individuals remain largely unknown. Contrary to previous studies focusing on differences in the promotor region of the gene, we investigate here the level of functional variation in the coding region (exon 1) of this locus. 相似文献1000.
Anna Bocci Sandro Lovari Muhammad Zafar Khan Emiliano Mori 《European Journal of Wildlife Research》2017,63(6):92
The snow leopard Panthera uncia coexists with the wolf Canis lupus throughout most of its distribution range. We analysed the food habits of snow leopards and wolves in their sympatric range in the Karakoram mountains of Pakistan. A total of 131 genotyped scats (N?=?74, snow leopard; N?=?57, Tibetan wolf) were collected during the cold periods (i.e. winter and spring) of 2011 and 2012 in the Hushey valley. Large mammals, i.e. livestock and ibex, accounted for 84.8 and 83.1% of the diet (relative frequency) of the snow leopard and the wolf, respectively. Domestic prey was the staple of the diet of both snow leopards (66.6%) and wolves (75.1%). Ibex Capra ibex, the only wild ungulate in our study area, contributed 18.2 and 16.9% of relative frequencies in the diets of the snow leopard and the wolf, respectively. In winter, the snow leopard heavily relied on domestic sheep (43.3%) for food, whereas the wolf preyed mainly on domestic goats (43.4%). Differently from other study areas, both snow leopards and wolves showed no apparent prey preference (Jacobs index: snow leopard min. ??0.098, max. 0.102; Tibetan wolf min. ??0.120, max. 0.03). In human depauperate areas, with livestock and only a few wild prey, should competitive interactions arise, two main scenarios could be expected, with either predator as a winner. In both cases, the best solution could primarily impinge on habitat restoration, so that a balance could be found between these predators, who have already coexisted for thousands of years. 相似文献