全文获取类型
收费全文 | 1453篇 |
免费 | 164篇 |
出版年
2022年 | 10篇 |
2021年 | 20篇 |
2020年 | 21篇 |
2019年 | 23篇 |
2018年 | 24篇 |
2017年 | 26篇 |
2016年 | 34篇 |
2015年 | 51篇 |
2014年 | 50篇 |
2013年 | 76篇 |
2012年 | 74篇 |
2011年 | 70篇 |
2010年 | 55篇 |
2009年 | 49篇 |
2008年 | 58篇 |
2007年 | 66篇 |
2006年 | 66篇 |
2005年 | 52篇 |
2004年 | 43篇 |
2003年 | 48篇 |
2002年 | 43篇 |
2001年 | 53篇 |
2000年 | 53篇 |
1999年 | 48篇 |
1998年 | 18篇 |
1997年 | 20篇 |
1996年 | 9篇 |
1995年 | 15篇 |
1994年 | 15篇 |
1993年 | 21篇 |
1992年 | 28篇 |
1991年 | 24篇 |
1990年 | 31篇 |
1989年 | 24篇 |
1988年 | 18篇 |
1987年 | 21篇 |
1986年 | 14篇 |
1985年 | 17篇 |
1983年 | 13篇 |
1982年 | 13篇 |
1981年 | 10篇 |
1980年 | 8篇 |
1979年 | 15篇 |
1977年 | 15篇 |
1976年 | 10篇 |
1975年 | 15篇 |
1974年 | 17篇 |
1973年 | 14篇 |
1972年 | 16篇 |
1971年 | 10篇 |
排序方式: 共有1617条查询结果,搜索用时 31 毫秒
121.
Vpx is a virion-associated protein of human immunodeficiency virus type 2 (HIV-2) and simian immunodeficiency viruses. The yeast two-hybrid system was used to identify invariant chain (Ii) as a cellular protein that interacts with HIV-2 Vpx. Vpx-Ii interaction was confirmed in cell-free reactions using bacterially expressed glutathione S-transferase fusion proteins and by coimmunoprecipitation in transfected and infected cells. In chronically infected cells expressing Vpx, Ii levels were markedly decreased, presumably due to enhanced degradation. These findings suggest that Vpx may disrupt major histocompatibility complex class II antigen presentation. 相似文献
122.
Sequencing of the internal transcribed spacer region ITS1 as a molecular tool detecting variation in the Stylosanthes guianensis species complex 总被引:1,自引:0,他引:1
J. Vander Stappen S. Van Campenhout S. Gama Lopez G. Volckaert 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,96(6-7):869-877
The internal transcribed spacer (ITS) regions 1 and 2 of the ribosomal DNA from Stylosanthes guianensis CIAT 1283 and cv ‘Schofield’ were amplified by polymerase chain reaction using conserved ITS primers from the 18S, 5.8S and
26S ribosomal genes flanking those regions. The entire region of 683 bp long was cloned, and seven clones were sequenced.
Comparison of the ITS spacer regions with published DNA sequences of other plant species revealed limited homology only; this
was in contrast to their comparison with the 5.8S rDNA sequences. The ITS1 region of 45 S. guianensis accessions was amplified by PCR and sequenced on both strands using the conserved primers ITS2-ITS5. These sequences, ranging
from 201 to 204 bp, were aligned to each other to assess intra-specific polymorphism. Within the S. guianensis (Aubl.) Sw. species complex, 11 DNA sequence types could be distinguished based on an insertion/deletion (indel) event and
15 single base-pair substitutions. In 1 of the S. guianensis types, two kinds of ITS1 sequence were observed in each individual, reminiscent of an incomplete homogenization of the repeat
structure in this type. Polymorphisms in the sequence of the ITS1 region were used to define molecular markers for S. guianensis on the basis of PCR-restriction fragment length polymorphism and selective PCR.
Received: 24 June 1997 / Accepted: 31 October 1997 相似文献
123.
X. Li H. J. van Eck J. N. A. M. Rouppe van der Voort D.-J. Huigen P. Stam E. Jacobsen 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,96(8):1121-1128
Due to the complexity of tetrasomic inheritance, mapping studies in potato (Solanum tuberosum L.) are generally conducted at the diploid level. In the present study we tested the feasibility of Bulked Segregant Analysis
(BSA) using a tetraploid offspring for the identification of AFLP markers linked to the R2 allele, which confers race-specific resistance to Phytophthora infestans. Eleven bulk-specific AFLP markers, detected in fingerprints of 205 AFLP primer combinations, could be mapped in a linkage
group encompassing the R2 locus. The efficiency of BSA at the tetraploid level, determined by the frequency of single-dose restriction fragments (SDRF),
was much higher than expected on the basis of overall genetic dissimilarity between the parental clones. The fortuitous detection
of AFLPs with linkage to the R2 allele is explained on the basis of specific genetic dissimilarity between cultivated potato and the chromosomal segment
introgressed from S. demissum carrying the resistant R2 allele. AFLP markers common to those with linkage to R2 were visually recognized by their electrophoretic mobility in the AFLP fingerprint in a parental clone of a reference mapping
population. Using these common AFLP markers we anchored the linkage group comprising the R2 allele to potato chromosome 4.
Received: 30 October 1997 / Accepted: 6 November 1997 相似文献
124.
125.
M. Dumarey I. SmetsY. Vander Heyden 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2010,878(28):2733-2740
Previously, multivariate calibration techniques have been successfully applied to model and predict the antioxidant activity of green tea from its chromatographic fingerprint. Since the selectivity differences between dissimilar chromatographic systems have already been valuably used in several applications, in this paper it is studied whether combining the complementary information contained in two dissimilar fingerprints can improve the predictive capacity of the multivariate calibration model. The simplest way of combining the data is concatenating both fingerprints for each sample. The resulting matrix can then be subjected to Orthogonal Projections to Latent Structures (O-PLS). Unfortunately, this approach resulted in a more complex model with a prediction error of about the average of the errors obtained with the individual fingerprints. Secondly, only the peaks with high loading and low orthogonal loading from both chromatograms were included in the O-PLS model. This resulted in a reduced complexity, but not in better predictions, probably due to a lack of complementarity of the information concerning the antioxidant capacity. Finally, the concatenated fingerprints were subjected to stepwise multiple linear regression (MLR) in order to build a model based on the variables most correlated with the antioxidant capacity. The obtained prediction error was lower than those of both previous approaches, but still higher than the error of the model based on a single analysis. This is probably again caused by a lack of complementarity in the variables. Nevertheless, it was advantageous to develop fingerprints on dissimilar system, because it enables to choose the most suited chromatographic profile to build a multivariate calibration model for the considered purpose. In contrast to what was expected, the study showed that the most simple (so the worst separated) fingerprints resulted in the best predictions. On the other hand, a more complex fingerprint in which more compounds are separated is still important to improve the interpretability of the model. 相似文献
126.
127.
128.
129.
Yiying Liu Elzbieta Rzeszutek Menno van der Voort Cheng-Hsuan Wu Even Thoen Ida Skaar Vincent Bulone Pieter C. Dorrestein Jos M. Raaijmakers Irene de Bruijn 《PloS one》2015,10(8)
Emerging fungal and oomycete pathogens are increasingly threatening animals and plants globally. Amongst oomycetes, Saprolegnia species adversely affect wild and cultivated populations of amphibians and fish, leading to substantial reductions in biodiversity and food productivity. With the ban of several chemical control measures, new sustainable methods are needed to mitigate Saprolegnia infections in aquaculture. Here, PhyloChip-based community analyses showed that the Pseudomonadales, particularly Pseudomonas species, represent one of the largest bacterial orders associated with salmon eggs from a commercial hatchery. Among the Pseudomonas species isolated from salmon eggs, significantly more biosurfactant producers were retrieved from healthy salmon eggs than from Saprolegnia-infected eggs. Subsequent in vivo activity bioassays showed that Pseudomonas isolate H6 significantly reduced salmon egg mortality caused by Saprolegnia diclina. Live colony mass spectrometry showed that strain H6 produces a viscosin-like lipopeptide surfactant. This biosurfactant inhibited growth of Saprolegnia in vitro, but no significant protection of salmon eggs against Saprolegniosis was observed. These results indicate that live inocula of aquatic Pseudomonas strains, instead of their bioactive compound, can provide new (micro)biological and sustainable means to mitigate oomycete diseases in aquaculture. 相似文献
130.
Lori Newman Jane Rowley Stephen Vander Hoorn Nalinka Saman Wijesooriya Magnus Unemo Nicola Low Gretchen Stevens Sami Gottlieb James Kiarie Marleen Temmerman 《PloS one》2015,10(12)