全文获取类型
收费全文 | 4887篇 |
免费 | 431篇 |
国内免费 | 473篇 |
出版年
2024年 | 5篇 |
2023年 | 56篇 |
2022年 | 134篇 |
2021年 | 253篇 |
2020年 | 173篇 |
2019年 | 216篇 |
2018年 | 201篇 |
2017年 | 152篇 |
2016年 | 223篇 |
2015年 | 294篇 |
2014年 | 338篇 |
2013年 | 359篇 |
2012年 | 449篇 |
2011年 | 392篇 |
2010年 | 249篇 |
2009年 | 205篇 |
2008年 | 267篇 |
2007年 | 215篇 |
2006年 | 225篇 |
2005年 | 188篇 |
2004年 | 183篇 |
2003年 | 136篇 |
2002年 | 139篇 |
2001年 | 106篇 |
2000年 | 100篇 |
1999年 | 94篇 |
1998年 | 61篇 |
1997年 | 60篇 |
1996年 | 46篇 |
1995年 | 49篇 |
1994年 | 35篇 |
1993年 | 27篇 |
1992年 | 27篇 |
1991年 | 32篇 |
1990年 | 16篇 |
1989年 | 6篇 |
1988年 | 12篇 |
1987年 | 19篇 |
1986年 | 8篇 |
1985年 | 12篇 |
1984年 | 8篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1981年 | 5篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有5791条查询结果,搜索用时 46 毫秒
941.
Identification and evaluation of a potential biocontrol agent,Bacillus subtilis,against Fusarium sp. in apple seedlings 总被引:3,自引:0,他引:3
Ruicheng Ju Yuhua Zhao Jinyu Li Hongxia Jiang Peng Liu Tao Yang Zhengzong Bao Baoqiang Zhou Xiaoyi Zhou Xunli Liu 《Annals of microbiology》2014,64(1):377-383
To find a potential biocontrol agent against Fusarium sp. in apple seedlings, an endophytic bacterium strain was isolated from apple tree tissues. The inhibitive efficiency of the isolated strain against the hyphal growth of Fusarium sp. and Rhizoctonia solani was tested. Strain Y-1 showed significant inhibitory effects against Fusarium oxysporum, F. moniliforme, F. proliferatum, F. solani and R. solani. Its antifungal activity against F. oxysporum was the highest, reaching up to 64.90 %. In vivo tests indicated that strain Y-1 effectively protects apple from F. oxysporum infections. The control effect reached 92.26 % when bacterial inoculation was performed 3 days prior to pathogen inoculation. Strain Y-1 could colonize the rhizosphere and tissues within 30 days. It was also able to induce systemic resistance in apple seedlings as shown by the activities of SOD and POD. Strain Y-1 significantly increased the root length, root wet and dry weights, and plant height of the apple seedlings compared with the control group. The homology analysis of the 16S rRNA sequence, together with morphological, physical, and biochemical analyses, revealed that strain Y-1 is Bacillus subtilis. 相似文献
942.
Comparing the Device Physics and Morphology of Polymer Solar Cells Employing Fullerenes and Non‐Fullerene Acceptors 下载免费PDF全文
Jason T. Bloking Tommaso Giovenzana Andrew T. Higgs Andrew J. Ponec Eric T. Hoke Koen Vandewal Sangwon Ko Zhenan Bao Alan Sellinger Michael D. McGehee 《Liver Transplantation》2014,4(12)
There is a need to find electron acceptors for organic photovoltaics that are not based on fullerene derivatives since fullerenes have a small band gap that limits the open‐circuit voltage (VOC), do not absorb strongly and are expensive. Here, a phenylimide‐based acceptor molecule, 4,7‐bis(4‐(N‐hexyl‐phthalimide)vinyl)benzo[c]1,2,5‐thiadiazole (HPI‐BT), that can be used to make solar cells with VOC values up to 1.11 V and power conversion efficiencies up to 3.7% with two thiophene polymers is demonstrated. An internal quantum efficiency of 56%, compared to 75–90% for polymer‐fullerene devices, results from less efficient separation of geminate charge pairs. While favorable energetic offsets in the polymer‐fullerene devices due to the formation of a disordered mixed phase are thought to improve charge separation, the low miscibility (<5 wt%) of HPI‐BT in polymers is hypothesized to prevent the mixed phase and energetic offsets from forming, thus reducing the driving force for charges to separate into the pure donor and acceptor phases where they can be collected. 相似文献
943.
Yong Wei Jiandong Bao Huijuan Cao Jing Zhai Chatchawan Jantasuriyarat Shimin Zuo Xuebiao Pan Hua Wang Bo Zhou 《Mycological Progress》2014,13(2):247-255
The haplotype variation and phylogeography of Rhizoctonia solani AG1-IA strains were estimated using rDNA5.8S-ITS and ß-actin gene sequences. Two haplotypes of ITS sequences were revealed, designated as ITSa and ITSb. Thirty-four SNPs from the ß-actin gene, which displayed more allele discriminations than rDNA-ITS, were identified. The SNPs were used to classify R. solani into 12 haplotypes, designated as H1–H12. Most SNPs occurred at the third codon position and resulted as silent mutations. Three SNPs occurred at the first codon position and one SNP occurred at the second position, which these four SNPs causing non-synonymous mutations. According to the translational amino acid sequences, the 12 nucleotide-inferred haplotypes were further classified into 5 groups, designated as ITRL, VARI, VARL, VTRI, and VAMI. Analysis of the geographical distribution of 12 haplotypes, showed that H1 and H9 were widely distributed in all studied locations and existed simultaneously in the strains collected in most areas. The results lead to the speculation that H1 and H9 could be the founder haplotypes of ß-actin gene, and other haplotypes might be derived from them. 相似文献
944.
Jia-zeng?Sun Jigui?Wang Shuang?Wang Daoli?Yuan Zhili?Li Bao?Yi Qiang?Hou Yaping?Mao Weiquan?LiuEmail author 《Virology journal》2014,11(1):210
Mink enteritis virus (MEV) is one of the most important pathogens in the mink industry. Recent studies have shed light into the role of microRNAs (miRNAs), small noncoding RNAs of length ranging from 18–23 nucleotides (nt), as critical modulators in the host-pathogen interaction networks. We previously showed that miRNA miR-181b can inhibit MEV replication by repression of viral non-structural protein 1 expression. Here, we report that two other miRNAs (miR-320a and miR-140) inhibit MEV entry into feline kidney (F81) cells by downregulating its receptor, transferrin receptor (TfR), by targeting the 3′ untranslated region (UTR) of TfR mRNA, while being themselves upregulated. 相似文献
945.
XIA HaiYong ZHAO JianHua SUN JianHao XUE YanFang EAGLING Tristan BAO XingGuo ZHANG FuSuo LI Long 《中国科学:生命科学英文版》2014,57(3):362-362
<正>~~ 相似文献
946.
947.
T. Thanyasiriwat S. Sraphet S. Whankaew O. Boonseng J. Bao D. A. Lightfoot S. Tangphatsornruang K. Triwitayakorn 《Plant biology (Stuttgart, Germany)》2014,16(1):197-207
Starch pasting viscosity is an important quality trait in cassava (Manihot esculenta Crantz) cultivars. The aim here was to identify loci and candidate genes associated with the starch pasting viscosity. Quantitative trait loci (QTL) mapping for seven pasting viscosity parameters was carried out using 100 lines of an F1 mapping population from a cross between two cassava cultivars Huay Bong 60 and Hanatee. Starch samples were obtained from roots of cassava grown in 2008 and 2009 at Rayong, and in 2009 at Lop Buri province, Thailand. The traits showed continuous distribution among the F1 progeny with transgressive variation. Fifteen QTL were identified from mean trait data, with Logarithm of Odds (LOD) values from 2.77–13.01 and phenotype variations explained (PVE) from10.0–48.4%. In addition, 48 QTL were identified in separate environments. The LOD values ranged from 2.55–8.68 and explained 6.6–43.7% of phenotype variation. The loci were located on 19 linkage groups. The most important QTL for pasting temperature (PT) (qPT.1LG1) from mean trait values showed largest effect with highest LOD value (13.01) and PVE (48.4%). The QTL co‐localised with PT and pasting time (PTi) loci that were identified in separate environments. Candidate genes were identified within the QTL peak regions. However, the major genes of interest, encoding the family of glycosyl or glucosyl transferases and hydrolases, were located at the periphery of QTL peaks. The loci identified could be effectively applied in breeding programmes to improve cassava starch quality. Alleles of candidate genes should be further studied in order to better understand their effects on starch quality traits. 相似文献
948.
Poshen B Chen Lihua J Zhu Sarah J Hainer Kurtis N McCannell Thomas G Fazzio 《BMC genomics》2014,15(1)
Background
Differential accessibility of DNA to nuclear proteins underlies the regulation of numerous cellular processes. Although DNA accessibility is primarily determined by the presence or absence of nucleosomes, differences in nucleosome composition or dynamics may also regulate accessibility. Methods for mapping nucleosome positions and occupancies genome-wide (MNase-seq) have uncovered the nucleosome landscapes of many different cell types and organisms. Conversely, methods specialized for the detection of large nucleosome-free regions of chromatin (DNase-seq, FAIRE-seq) have uncovered numerous gene regulatory elements. However, these methods are less successful in measuring the accessibility of DNA sequences within nucelosome arrays.Results
Here we probe the genome-wide accessibility of multiple cell types in an unbiased manner using restriction endonuclease digestion of chromatin coupled to deep sequencing (RED-seq). Using this method, we identified differences in chromatin accessibility between populations of cells, not only in nucleosome-depleted regions of the genome (e.g., enhancers and promoters), but also within the majority of the genome that is packaged into nucleosome arrays. Furthermore, we identified both large differences in chromatin accessibility in distinct cell lineages and subtle but significant changes during differentiation of mouse embryonic stem cells (ESCs). Most significantly, using RED-seq, we identified differences in accessibility among nucleosomes harboring well-studied histone variants, and show that these differences depend on factors required for their deposition.Conclusions
Using an unbiased method to probe chromatin accessibility genome-wide, we uncover unique features of chromatin structure that are not observed using more widely-utilized methods. We demonstrate that different types of nucleosomes within mammalian cells exhibit different degrees of accessibility. These findings provide significant insight into the regulation of DNA accessibility.Electronic supplementary material
The online version of this article (doi:10.1186/1471-2164-15-1104) contains supplementary material, which is available to authorized users. 相似文献949.
950.
Wei Li Yijing Li Weizhi Li Jinping Yang Mingxin Song Ruinan Diao Honglin Jia Yixin Lu Jun Zheng Xichen Zhang Lihua Xiao 《PloS one》2014,9(5)
Despite many recent advances in genotype characterization of Enterocytozoon bieneusi worldwide and the exploration of the extent of cross-species transmission of microsporidiosis between humans and animals, the epidemiology of this neglected disease in China is poorly understood. In this study, a very high prevalence (60.3%; 94/156) of E. bieneusi infections in farmed pigs in Jilin province was detected by PCR of the ribosomal internal transcribed spacer (ITS). DNA sequence analysis of 88 E. bieneusi–positive specimens identified 12 distinct genotypes (11 known: CHN7, CS-1, CS-4, CS-6, EbpA, EbpB, EbpC, EbpD, EBITS3, G, and Henan-I; one novel: CS-9). Frequent appearance of mixed genotype infections was seen in the study animals. Weaned (74.6%; 53/71) or pre-weaned (68.8%; 22/32) pigs have infection rates significantly higher than growing pigs (35.8%; 19/53) (p<0.01). Likewise, E. bieneusi was detected in 2 of 45 sheep fecal specimens (4.4%) in Heilongjiang province, belonging to the known genotype BEB6. Genotypes EbpA, EbpC, EbpD, and Henan-I examined herein have been documented in the cases of human infections and BEB6, EbpA, EbpC, and EbpD in wastewater in central China. Infections of EbpA and EbpC in humans were also reported in other areas of the world. The other known genotypes (CHN7, CS-1, CS-4, CS-6, EBITS3, EbpB, and G) and the new genotype CS-9 were genetically clustered into a group of existing E. bieneusi genotypes with zoonotic potential. Thus, pigs could be a potential source of human E. bieneusi infections in China. 相似文献