全文获取类型
收费全文 | 1692篇 |
免费 | 106篇 |
国内免费 | 2篇 |
专业分类
1800篇 |
出版年
2023年 | 5篇 |
2022年 | 12篇 |
2021年 | 20篇 |
2020年 | 6篇 |
2019年 | 12篇 |
2018年 | 15篇 |
2017年 | 9篇 |
2016年 | 21篇 |
2015年 | 54篇 |
2014年 | 77篇 |
2013年 | 96篇 |
2012年 | 137篇 |
2011年 | 127篇 |
2010年 | 72篇 |
2009年 | 69篇 |
2008年 | 120篇 |
2007年 | 114篇 |
2006年 | 118篇 |
2005年 | 112篇 |
2004年 | 115篇 |
2003年 | 95篇 |
2002年 | 82篇 |
2001年 | 17篇 |
2000年 | 18篇 |
1999年 | 25篇 |
1998年 | 29篇 |
1997年 | 32篇 |
1996年 | 20篇 |
1995年 | 13篇 |
1994年 | 17篇 |
1993年 | 14篇 |
1992年 | 20篇 |
1991年 | 11篇 |
1990年 | 7篇 |
1989年 | 10篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 3篇 |
1985年 | 7篇 |
1984年 | 9篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1973年 | 5篇 |
1968年 | 2篇 |
1965年 | 2篇 |
1957年 | 2篇 |
排序方式: 共有1800条查询结果,搜索用时 15 毫秒
61.
62.
Echalier A Trivelli X Corbier C Rouhier N Walker O Tsan P Jacquot JP Aubry A Krimm I Lancelin JM 《Biochemistry》2005,44(6):1755-1767
Peroxiredoxins (Prxs) constitute a family of thiol peroxidases that reduce hydrogen peroxide, peroxinitrite, and hydroperoxides using a strictly conserved cysteine. Very abundant in all organisms, Prxs are produced as diverse isoforms characterized by different catalytic mechanisms and various thiol-containing reducing agents. The oligomeric state of Prxs and the link with their functionality is a subject of intensive research. We present here a combined X-ray and nuclear magnetic resonance (NMR) study of a plant Prx that belongs to the D-Prx (type II) subfamily. The Populus trichocarpa Prx is the first Prx shown to be regenerated in vitro by both the glutaredoxin and thioredoxin systems. The crystal structure and solution NMR provide evidence that the reduced protein is a specific noncovalent homodimer both in the crystal and in solution. The dimer interface is roughly perpendicular to the plane of the central beta sheet and differs from the interface of A- and B-Prx dimers, where proteins associate in the plane parallel to the beta sheet. The homodimer interface involves residues strongly conserved in the D (type II) Prxs, suggesting that all Prxs of this family can homodimerize. The study provides a new insight into the Prx oligomerism and the basis for protein-protein and enzyme-substrate interaction studies by NMR. 相似文献
63.
Combined inactivation and expression strategy to study gene function under physiological conditions: application to identification of new Escherichia coli adhesins 下载免费PDF全文
In bacteria, whereas disruption methods have been improved recently, the use of plasmid complementation strategies are still subject to limitations, such as cloning difficulties, nonphysiological levels of gene expression, or a requirement for antibiotics as plasmid selection pressure. Moreover, because of the pleiotropic modifications of cell physiology often induced by plasmid-based complementation, these strategies may introduce biases when biological process such as adhesion or biofilm formation are studied. We developed a plasmid-free approach that combines the lambda-red linear DNA recombination method with site-directed insertion of a repression and expression (RExBAD) cassette which places a functional pBAD promoter upstream of a target gene. We showed that this method permits both inactivation and modulation of most Escherichia coli gene expression, including expression of toxin and essential genes. We used this strategy to study adhesion and bacterial biofilms by placing the RExBAD cassette in front of the tra operon, encoding the DNA transfer and pilus genes on the F conjugative plasmid, and in front of flu, the antigen 43 (Ag43) autotransporter adhesin-encoding gene. In silico analysis revealed the existence of 10 genes with homology to the Ag43 gene that were good candidates for genes that encode putative new adhesins in E. coli. We used the RExBAD strategy to study these genes and demonstrated that induction of expression of four of them is associated with adhesion of E. coli to abiotic surfaces. The potential use of the RExBAD approach to study the function of cryptic or uncharacterized genes in large-scale postgenomic functional analyses is discussed. 相似文献
64.
Jernej Jakse Natasa Stajner Zlata Luthar Jean-Marc Jeltsch Branka Javornik 《Molecular breeding : new strategies in plant improvement》2011,28(2):227-239
Data mining of gene sequences available from various projects dealing with the development of expressed sequence tags (ESTs)
can contribute to the discovery of new microsatellite markers. Our aim was to develop new microsatellite markers in hop isolated
from an enriched cDNA library and from coding GenBank sequences and to test their suitability in hop diversity studies and
for construction of a linkage map. In a set of 614 coding GenBank sequences, 72 containing microsatellites were found (11.7%);
the most frequent were trinucleotide repeats (54.0%) followed by dinucleotide repeats (34.5%). Additionally, 11 sequences
containing microsatellites were isolated from an enriched cDNA library. A total of 34 primer pairs were designed, 29 based
on GenBank sequences and five on sequences from the cDNA enriched library. Twenty-seven (79.4%) coding microsatellites were
successfully amplified and used in diversity and linkage mapping studies. Eleven primer pairs amplified 12 coding microsatellite
loci suitable for mapping and were placed on female and male linkage maps. We were able to extend previous simple sequence
repeat (SSR) female, male and integral maps by 38.8, 25.8 and 40.0 cM, respectively. In the diversity study, 36 diverse hop
genotypes were analyzed. Twenty-four coding microsatellites were polymorphic, 17 showing co-dominant behavior and 7 primer
pairs amplifying three or more bands in some hop genotypes. Altogether, 143 microsatellite DNA fragments were amplified and
they revealed a clear separation of hop genotypes according to geographical region, use or breeding history. In addition,
a discussion and comparison of results with other plant coding/EST SSR studies is presented. Our results showed that these
microsatellite markers can enhance hop diversity and linkage mapping studies and are a comparable marker system to non-coding
SSRs. 相似文献
65.
Iglika Djoumerska-Alexieva Lubka Roumenina Anastas Pashov Jordan Dimitrov Maya Hadzhieva Sandro Lindig Elisaveta Voynova Petya Dimitrova Nina Ivanovska Clemens Bockmeyer Zvetanka Stefanova Catherine Fitting Markus Bl?ss Ralf Claus Stephan von Gunten Srini Kaveri Jean-Marc Cavaillon Michael Bauer Tchavdar Vassilev 《Molecular medicine (Cambridge, Mass.)》2015,21(1):1002-1010
Sepsis is a major cause for death worldwide. Numerous interventional trials with agents neutralizing single proinflammatory mediators have failed to improve survival in sepsis and aseptic systemic inflammatory response syndromes. This failure could be explained by the widespread gene expression dysregulation known as “genomic storm” in these patients. A multifunctional polyspecific therapeutic agent might be needed to thwart the effects of this storm. Licensed pooled intravenous immunoglobulin preparations seemed to be a promising candidate, but they have also failed in their present form to prevent sepsis-related death. We report here the protective effect of a single dose of intravenous immunoglobulin preparations with additionally enhanced polyspecificity in three models of sepsis and aseptic systemic inflammation. The modification of the pooled immunoglobulin G molecules by exposure to ferrous ions resulted in their newly acquired ability to bind some proinflammatory molecules, complement components and endogenous “danger” signals. The improved survival in endotoxemia was associated with serum levels of proinflammatory cytokines, diminished complement consumption and normalization of the coagulation time. We suggest that intravenous immunoglobulin preparations with additionally enhanced polyspecificity have a clinical potential in sepsis and related systemic inflammatory syndromes. 相似文献
66.
67.
68.
Ten microsatellite loci were used to investigate the impact of human activity on the spatial and temporal genetic structure of Vitellaria paradoxa (Sapotaceae), a parkland tree species in agroforestry systems in southern Mali. Two stands (forest and fallow) and three cohorts (adults, juveniles and natural regeneration) in each stand were studied to: (i) compare their levels of genetic diversity (gene diversity, HE; allelic richness, Rs; and inbreeding, FIS); (ii) assess their genetic differentiation (FST); and (iii) compare their levels of spatial genetic structuring. Gene diversity parameters did not vary substantially among stands or cohorts, and tests for bottleneck events were nonsignificant. The inbreeding coefficients were not significantly different from zero in most cases (FIS = -0.025 in forest and 0.045 in fallow), suggesting that the species is probably outbreeding. There was a weak decrease in F(IS) with age, suggesting inbreeding depression. Differentiation of stands within each cohort was weak (FST = 0.026, 0.0005, 0.010 for adults, juveniles and regeneration, respectively), suggesting extensive gene flow. Cohorts within each stand were little differentiated (FST = -0.001 and 0.001 in forest and fallow, respectively). The spatial genetic structure was more pronounced in fallow than in forest where adults showed no spatial structuring. In conclusion, despite the huge influence of human activity on the life cycle of Vitellaria paradoxa growing in parkland systems, the impact on the pattern of genetic variation at microsatellite loci appears rather limited, possibly due to the buffering effect of extensive gene flow between unmanaged and managed populations. 相似文献
69.
70.