全文获取类型
收费全文 | 2933篇 |
免费 | 198篇 |
专业分类
3131篇 |
出版年
2024年 | 4篇 |
2023年 | 33篇 |
2022年 | 63篇 |
2021年 | 106篇 |
2020年 | 89篇 |
2019年 | 95篇 |
2018年 | 122篇 |
2017年 | 96篇 |
2016年 | 140篇 |
2015年 | 183篇 |
2014年 | 201篇 |
2013年 | 220篇 |
2012年 | 264篇 |
2011年 | 240篇 |
2010年 | 145篇 |
2009年 | 109篇 |
2008年 | 142篇 |
2007年 | 136篇 |
2006年 | 121篇 |
2005年 | 90篇 |
2004年 | 83篇 |
2003年 | 70篇 |
2002年 | 77篇 |
2001年 | 44篇 |
2000年 | 43篇 |
1999年 | 33篇 |
1998年 | 13篇 |
1997年 | 12篇 |
1996年 | 15篇 |
1995年 | 10篇 |
1994年 | 15篇 |
1993年 | 11篇 |
1992年 | 12篇 |
1991年 | 11篇 |
1990年 | 7篇 |
1989年 | 9篇 |
1988年 | 8篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 8篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 5篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 2篇 |
排序方式: 共有3131条查询结果,搜索用时 15 毫秒
61.
Saulo Alves Aflitos Gabino Sanchez‐Perez Dick de Ridder Paul Fransz Michael E. Schranz Hans de Jong Sander A. Peters 《The Plant journal : for cell and molecular biology》2015,82(1):174-182
Breeding by introgressive hybridization is a pivotal strategy to broaden the genetic basis of crops. Usually, the desired traits are monitored in consecutive crossing generations by marker‐assisted selection, but their analyses fail in chromosome regions where crossover recombinants are rare or not viable. Here, we present the Introgression Browser (iBrowser ), a bioinformatics tool aimed at visualizing introgressions at nucleotide or SNP (Single Nucleotide Polymorphisms) accuracy. The software selects homozygous SNPs from Variant Call Format (VCF) information and filters out heterozygous SNPs, multi‐nucleotide polymorphisms (MNPs) and insertion–deletions (InDels). For data analysis iBrowser makes use of sliding windows, but if needed it can generate any desired fragmentation pattern through General Feature Format (GFF) information. In an example of tomato (Solanum lycopersicum) accessions we visualize SNP patterns and elucidate both position and boundaries of the introgressions. We also show that our tool is capable of identifying alien DNA in a panel of the closely related S. pimpinellifolium by examining phylogenetic relationships of the introgressed segments in tomato. In a third example, we demonstrate the power of the iBrowser in a panel of 597 Arabidopsis accessions, detecting the boundaries of a SNP‐free region around a polymorphic 1.17 Mbp inverted segment on the short arm of chromosome 4. The architecture and functionality of iBrowser makes the software appropriate for a broad set of analyses including SNP mining, genome structure analysis, and pedigree analysis. Its functionality, together with the capability to process large data sets and efficient visualization of sequence variation, makes iBrowser a valuable breeding tool. 相似文献
62.
Ester B. M. Remmerswaal Paul L. Klarenbeek Nuno L. Alves Marieke E. Doorenspleet Barbera D. C. van Schaik Rebecca E. E. Esveldt Mirza M. Idu Ester M. M. van Leeuwen Nelly van der Bom-Baylon Antoine H. C. van Kampen Sven D. Koch Hanspeter Pircher Frederike J. Bemelman Anja ten Brinke Frank Baas Ineke J. M. ten Berge Rene A.W. van Lier Niek de Vries 《Journal of virology》2015,89(1):568-580
63.
Molecular,genetic and evolutionary analysis of a paracentric inversion in Arabidopsis thaliana 下载免费PDF全文
Paul Fransz Gabriella Linc Cheng‐Ruei Lee Saulo Alves Aflitos Jesse R. Lasky Christopher Toomajian Hoda Ali Janny Peters Peter van Dam Xianwen Ji Mateusz Kuzak Tom Gerats Ingo Schubert Korbinian Schneeberger Vincent Colot Rob Martienssen Maarten Koornneef Magnus Nordborg Thomas E. Juenger Hans de Jong Michael E. Schranz 《The Plant journal : for cell and molecular biology》2016,88(2):159-178
Chromosomal inversions can provide windows onto the cytogenetic, molecular, evolutionary and demographic histories of a species. Here we investigate a paracentric 1.17‐Mb inversion on chromosome 4 of Arabidopsis thaliana with nucleotide precision of its borders. The inversion is created by Vandal transposon activity, splitting an F‐box and relocating a pericentric heterochromatin segment in juxtaposition with euchromatin without affecting the epigenetic landscape. Examination of the RegMap panel and the 1001 Arabidopsis genomes revealed more than 170 inversion accessions in Europe and North America. The SNP patterns revealed historical recombinations from which we infer diverse haplotype patterns, ancient introgression events and phylogenetic relationships. We find a robust association between the inversion and fecundity under drought. We also find linkage disequilibrium between the inverted region and the early flowering Col‐FRIGIDA allele. Finally, SNP analysis elucidates the origin of the inversion to South‐Eastern Europe approximately 5000 years ago and the FRI‐Col allele to North‐West Europe, and reveals the spreading of a single haplotype to North America during the 17th to 19th century. The ‘American haplotype’ was identified from several European localities, potentially due to return migration. 相似文献
64.
Peptidases in the extracellular space might affect the integrity of recombinant proteins expressed in, and secreted from, plant cells. To identify extracellular peptidases, we recovered the leaf intercellular fluid from Nicotiana tabacum plants by an infiltration-centrifugation method. The activity of various peptidases was detected by an in vitro assay in the presence of specific inhibitors, using BSA and human serum gamma-globulin as substrates. Peptidases were detected by 1- and 2-D zymography in a polyacrylamide gel containing gelatin as substrate. Proteolytic activity was observed over a wide range of molecular masses equal to, or higher than, 45 kDa. To identify the peptidases, the extracellular proteins were digested with trypsin and analyzed by LC and MS. Seventeen peptides showing identity or similarity to predicted plant aspartic, cysteine, and serine peptidases have been identified. The extracellular localization of a cysteine peptidase aleurain homolog was also shown. 相似文献
65.
de Aquino TM Liesen AP da Silva RE Lima VT Carvalho CS de Faria AR de Araújo JM de Lima JG Alves AJ de Melo EJ Góes AJ 《Bioorganic & medicinal chemistry》2008,16(1):446-456
In the present communication, a new series of 2-[(phenylmethylene)hydrazono]-4-oxo-3-phenyl-5-thiazolidineacetic acids (2a-p) have been synthesized. Benzaldehyde 4-phenyl-3-thiosemicarbazones substituted (1a-p) were also obtained and used as intermediate to give the title compounds. All synthesized compounds were characterized by IR, (1)H and (13)C NMR. The in vitro anti-Toxoplasma gondii activity of 1a-p and 2a-p was evaluated. The 4-thiazolidinones (2a-p) were screened for their in vitro antimicrobial activity. For anti-Toxoplasma gondii activity, in general, all compounds promoted decreases in the percentage of infected cells leading to parasite elimination. These effects on intracellular parasites also caused a decrease in the mean number of tachyzoites. In addition, most of the 4-thiazolidinones showed more effective toxicity against intracellular parasites, with IC(50) values ranging from 0.05 to 1 mM. According to results of antimicrobial activity, compounds 2f, 2l, and 2p showed best activity against Mycobacterium luteus, 2c was more active against Mycobacterium tuberculosis, and 2g, 2l, and 2n showed same activity as nistatin (standard drug) against Candida sp. (4249). 相似文献
66.
Muñoz G Alves E Fernández A Ovilo C Barragán C Estellé J Quintanilla R Folch JM Silió L Rodríguez MC Fernández AI 《Animal genetics》2007,38(6):639-646
Refinement of previous QTL on porcine chromosome 12 for fatty-acid composition and a candidate gene association analysis were conducted using an Iberian × Landrace cross. The concentrations of ten fatty acids were assayed in backfat tissue from which four metabolic ratios were calculated for 403 F2 animals. Linkage analysis identified two significant QTL. The first QTL was associated with the average chain length ratio and the percentages of myristic, palmitic and gadoleic acids. The second QTL was associated with percentages of palmitoleic, stearic and vaccenic acids. Based upon its position on SSC12, fatty acid synthase was tested as a candidate gene for the first QTL and no significant effects were found. Similarly, gastric inhibitory polypeptide ( GIP ) and acetyl-coenzyme A carboxylase alpha ( ACACA ) were tested as candidate genes for the second QTL using three SNPs in GIP and 15 synonymous SNPs in ACACA cDNA sequences. Two missense SNPs in GIP showed significant effects with palmitoleic and stearic fatty-acid concentration. Highly significant associations were found for two SNPs in ACACA with stearic, palmitoleic and vaccenic fatty-acid concentrations. These associations could be due to linkage disequilibrium with the causal mutations. 相似文献
67.
During the last decades wild rabbit (Oryctolagus cuniculus) populations have been progressively declining in the Iberian Peninsula as a result of several factors, namely habitat deterioration.
Hence, habitat management has become one of the most commonly used management techniques to restore wild rabbit populations.
To test the efficacy of some of these measures (creation of pastures, opening firebreaks) in rabbit populations, two managed
(M1 and M2) and two control areas (C1 and C2) were selected in the Portuguese Southwest (SW) Coast. In each study area, the
influence of habitat management was tested assessing temporal changes in rabbit abundance obtained from pellet counts and
in rabbits’ diet through microhistological analysis of fecal pellets. Rabbit densities were higher in managed than in control
areas (mean annual values: M1–1.08 pellets/m2; M2–1.60 pellets/m2; C1–0.69 pellets/m2; C2–0.40 pellets/m2). In general, Gramineae was the most consumed plant group throughout the year and in all study areas. In control areas, consumption
of alternative species with low nutritive value (e.g., Cistus ladanifer) was observed, especially in summer. Our data suggest a positive influence of habitat management on rabbit populations since
in managed areas individuals presented an overall higher abundance and a more nutritive diet. In addition, there was no evidence
that sown species were consumed in detriment to naturally occurring grasses, suggesting that in Mediterranean semi-arid regions
clearing vegetation inside the scrubland might be sufficient to improve habitat conditions for rabbits. 相似文献
68.
69.
This study reports the effect of daily mean ambient temperature on daily activity and habitat use by the giant anteater (Myrmecophaga tridactyla) in the Pantanal wetlands of Brazil. We equipped 11 giant anteaters with a global position system collar programmed to acquire a location every 10 min for 15 d. A temperature data logger left in the meteorological station at the study site registered data on ambient temperature. Giant anteaters were mainly active in open fields except during the coldest days, when they sought protection inside forests. Giant anteaters also used open habitats for resting but during the hottest or chilliest days they sheltered in forests. In the Pantanal, where temperatures are usually high, giant anteaters were active all night long, but as daily average ambient temperature decreased anteaters began and finished activity progressively earlier and reduced total activity. As a consequence, time spent active at daylight increased progressively and time spent active during the night decreased progressively, probably to allow the anteaters to expose themselves to solar radiation and to avoid heat loss during the night. 相似文献
70.
Genetic diversity and differentiation in Portuguese cattle breeds using microsatellites 总被引:1,自引:0,他引:1
Genotype data from 30 microsatellites were used to assess genetic diversity and relationships among 10 native Portuguese cattle breeds, American Charolais and the Brazilian Caracú. Hardy–Weinberg equilibrium was observed for all loci/population combinations except for five loci in Brava de Lide and one locus in Alentejana that exhibited heterozygote deficiency. Estimates of average observed and expected heterozygosities, total number of alleles (TNA) per breed and mean number of alleles (MNA) per locus/population were obtained. A total of 390 alleles were detected. TNA among Iberian cattle ranged from 170 to 237 and MNA ranged from 5.67 to 8.07. The highest observed heterozygosities were found in the Caracú, Maronesa, Garvonesa and Arouquesa and the lowest in Brava de Lide and Mirandesa. Estimation of population subdivision using Wright's FST index showed that the average proportion of genetic variation explained by breed differences was 9%. Neighbour‐joining phylogenetic trees based on DA distances showed that the genetic relationships of present‐day Portuguese native breeds are consistent with historical origins in the Brown Concave (Arouquesa, Mirandesa, Marinhoa) and Red Convex (Mertolenga, Alentejana, Garvonesa, Minhota) evolutionary groups. The Iberian Black Orthoide group, represented by Brava de Lide and Maronesa, and the Barrosã breed appeared to be more closely related to the Brown Concave group but may represent a separate lineage. The Caracú breed was not found to be closely associated with any of the native Portuguese breeds. 相似文献