全文获取类型
收费全文 | 1681篇 |
免费 | 64篇 |
国内免费 | 1篇 |
专业分类
1746篇 |
出版年
2023年 | 5篇 |
2022年 | 7篇 |
2021年 | 9篇 |
2020年 | 10篇 |
2019年 | 13篇 |
2018年 | 22篇 |
2017年 | 15篇 |
2016年 | 42篇 |
2015年 | 66篇 |
2014年 | 56篇 |
2013年 | 102篇 |
2012年 | 85篇 |
2011年 | 120篇 |
2010年 | 69篇 |
2009年 | 55篇 |
2008年 | 102篇 |
2007年 | 114篇 |
2006年 | 115篇 |
2005年 | 98篇 |
2004年 | 80篇 |
2003年 | 113篇 |
2002年 | 89篇 |
2001年 | 13篇 |
2000年 | 14篇 |
1999年 | 20篇 |
1998年 | 24篇 |
1997年 | 12篇 |
1996年 | 13篇 |
1995年 | 21篇 |
1994年 | 17篇 |
1993年 | 13篇 |
1992年 | 15篇 |
1991年 | 20篇 |
1990年 | 17篇 |
1989年 | 13篇 |
1988年 | 5篇 |
1987年 | 10篇 |
1986年 | 15篇 |
1985年 | 9篇 |
1984年 | 12篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1980年 | 10篇 |
1978年 | 8篇 |
1977年 | 10篇 |
1976年 | 4篇 |
1975年 | 5篇 |
1966年 | 3篇 |
1965年 | 3篇 |
排序方式: 共有1746条查询结果,搜索用时 15 毫秒
141.
Mikołajczyk MM Zaleśny R Czyżnikowska Z Toman P Leszczynski J Bartkowiak W 《Journal of molecular modeling》2011,17(9):2143-2149
An assessment of several widely used exchange--correlation potentials in computing charge-transfer integrals is performed.
In particular, we employ the recently proposed Coulomb-attenuated model which was proven by other authors to improve upon
conventional functionals in the case of charge-transfer excitations. For further validation, two distinct approaches to compute
the property in question are compared for a phthalocyanine dimer. 相似文献
142.
143.
Błaszczyk L Popiel D Chełkowski J Koczyk G Samuels GJ Sobieralski K Siwulski M 《Journal of applied genetics》2011,52(2):233-243
In the present study, we reinvestigate the diversity of Trichoderma in Poland utilizing a combination of morphological and molecular/phylogenetic methods. A total of 170 isolates were collected
from six different substrata at 49 sites in Poland. These were divided among 14 taxa as follows: 110 of 170 Trichoderma isolates were identified to the species level by the analysis of their ITS1, ITS2 rDNA sequences as: T. harzianum (43 isolates), T. aggressivum (35), T. citrinoviride (11), T. hamatum (9), T. virens (6), T. longibrachiatum (4), T. polysporum (1), and T. tomentosum (1); 60 isolates belonging to the Viride clade were identified based on a fragment of the translation-elongation factor 1-alpha
(tef1) gene as: T. atroviride (20 isolates), T. gamsii (2), T. koningii (17), T. viridescens (13), T. viride (7), and T. koningiopsis (1). Identifications were made using the BLAST interface in TrichOKEY and TrichoBLAST (). The most diverse substrata were soil (nine species per 22 isolates) and decaying wood (nine species per 75 isolates). The
most abundant species (25%) isolated from all substrata was T. harzianum. 相似文献
144.
145.
Epigenetic contribution to stress adaptation in plants 总被引:5,自引:0,他引:5
Plant epigenetics has recently gained unprecedented interest, not only as a subject of basic research but also as a possible new source of beneficial traits for plant breeding. We discuss here mechanisms of epigenetic regulation that should be considered when undertaking the latter. Since these mechanisms are responsible for the formation of heritable epigenetic gene variants (epialleles) and also regulate transposons mobility, both aspects could be exploited to broaden plant phenotypic and genetic variation, which could improve long-term plant adaptation to environmental challenges and, thus, increase productivity. 相似文献
146.
Next generation sequencing provides rapid access to the genome of Puccinia striiformis f. sp. tritici, the causal agent of wheat stripe rust 总被引:2,自引:0,他引:2
Cantu D Govindarajulu M Kozik A Wang M Chen X Kojima KK Jurka J Michelmore RW Dubcovsky J 《PloS one》2011,6(8):e24230
Background
The wheat stripe rust fungus (Puccinia striiformis f. sp. tritici, PST) is responsible for significant yield losses in wheat production worldwide. In spite of its economic importance, the PST genomic sequence is not currently available. Fortunately Next Generation Sequencing (NGS) has radically improved sequencing speed and efficiency with a great reduction in costs compared to traditional sequencing technologies. We used Illumina sequencing to rapidly access the genomic sequence of the highly virulent PST race 130 (PST-130).Methodology/Principal Findings
We obtained nearly 80 million high quality paired-end reads (>50x coverage) that were assembled into 29,178 contigs (64.8 Mb), which provide an estimated coverage of at least 88% of the PST genes and are available through GenBank. Extensive micro-synteny with the Puccinia graminis f. sp. tritici (PGTG) genome and high sequence similarity with annotated PGTG genes support the quality of the PST-130 contigs. We characterized the transposable elements present in the PST-130 contigs and using an ab initio gene prediction program we identified and tentatively annotated 22,815 putative coding sequences. We provide examples on the use of comparative approaches to improve gene annotation for both PST and PGTG and to identify candidate effectors. Finally, the assembled contigs provided an inventory of PST repetitive elements, which were annotated and deposited in Repbase.Conclusions/Significance
The assembly of the PST-130 genome and the predicted proteins provide useful resources to rapidly identify and clone PST genes and their regulatory regions. Although the automatic gene prediction has limitations, we show that a comparative genomics approach using multiple rust species can greatly improve the quality of gene annotation in these species. The PST-130 sequence will also be useful for comparative studies within PST as more races are sequenced. This study illustrates the power of NGS for rapid and efficient access to genomic sequence in non-model organisms. 相似文献147.
148.
Zagrodzki Paweł Mietelski Jerzy W. Krośniak Mirosław Petelenz Barbara 《Biological trace element research》1994,(1):273-277
The aim of this work was to check whether the stable cesium content in forest litter affects the value of radiocesium from
litter-to-mushroom transfer factorTf or not. Total cesium in litter, measured by AAS, varied from 0.1–2.7 μg/g. These data, combined with earlier results for
mushrooms, showed no simple correlation forTf. More complex relationships provided very high correlation coefficients, but their validity needs further investigation. 相似文献
149.
Anna Szpakowicz Marek Kiliszek Witold Pepinski Ewa Waszkiewicz Maria Franaszczyk Ma?gorzata Skawronska Rafal Ploski Anna Niemcunowicz-Janica S?awomir Dobrzycki Grzegorz Opolski W?odzimierz Jerzy Musial Karol Adam Kaminski 《PloS one》2014,9(8)
Objective
The rs10757278, rs1333049 and rs4977574 are single nucleotide polymorphisms (SNPs) of chromosome 9p21 locus associated with a prevalence of acute coronary syndromes (ACS). Reports concerning their association with long-term outcome after an ACS are equivocal. The aim of our study was to investigate the association of the 9p21.3 locus with 5-year overall mortality in patients with ST-elevation myocardial infarction (STEMI).Materials and methods
We performed a retrospective analysis of data collected prospectively in 2 independent registries of consecutive patients with STEMI (derivation and validation group). Genotyping was performed with the TaqMan method. The analyzed end-point was total mortality.Results
The derivation group comprised 589 patients: 25.3% female (n = 149), mean age 62.4±12.0 years, total 5-year mortality 16.6% (n = 98). When all the study group was analyzed, no significant differences in mortality were found between the genotypes. However, in high-risk patients (GRACE risk score ≥155 points, n = 238), homozygotes associated with higher risk for ACS had significantly better 5-year survival compared to other genotypes. The hazard ratio associated with the high-risk genotype (a homozygote of high risk for ACS or a heterozygote) was: HR = 2.2 (1.15–4.2) for the rs10757278 polymorphism, HR = 2.7 (95% CI 1.3–5.4) for the rs4977574 one and HR = 2.3 (1.2–4.5) for the rs1333049 one (Cox proportional hazards model). Survival analysis in the validation group (n = 365) showed a clear trend towards better prognosis in GG homozygotes of the rs10757278 SNP, which confirms our initial results (p = 0.09, log-rank test).Conclusions
The 9p21.3 locus is associated with 5-year mortality in high-risk patients with STEMI. The genotypes associated with higher risk for ACS show a protective effect in terms of further survival (instead of a deteriorating prognosis, as reported previously). This finding, due to the very high size of the effect, could potentially be applied to clinical practice, if appropriate methods are elaborated. 相似文献150.
To date, the calcium-regulated membrane guanylate cyclase Rod Outer Segment Guanylate Cyclase type 1 (ROS-GC1) transduction system in addition to photoreceptors is known to be expressed in three other types of neuronal cells: in the pinealocytes, mitral cells of the olfactory bulb and the gustatory epithelium of tongue. Very recent studies from our laboratory show that expression of ROS-GC1 is not restricted to the neuronal cells; the male gonads and the spermatozoa also express ROS-GC1. In this presentation, the authors review the existing information on the localization and function of guanylate cyclase with special emphasis on Ca2+-modulated membrane guanylate cyclase, ROS-GC1, in the testes. The role of ROS-GC1 and its Ca2+-sensing modulators in the processes of spermatogenesis and fertilization are discussed. 相似文献