全文获取类型
收费全文 | 2172篇 |
免费 | 178篇 |
国内免费 | 1篇 |
专业分类
2351篇 |
出版年
2024年 | 5篇 |
2023年 | 32篇 |
2022年 | 65篇 |
2021年 | 135篇 |
2020年 | 71篇 |
2019年 | 81篇 |
2018年 | 83篇 |
2017年 | 63篇 |
2016年 | 107篇 |
2015年 | 138篇 |
2014年 | 183篇 |
2013年 | 159篇 |
2012年 | 186篇 |
2011年 | 194篇 |
2010年 | 104篇 |
2009年 | 80篇 |
2008年 | 114篇 |
2007年 | 94篇 |
2006年 | 85篇 |
2005年 | 94篇 |
2004年 | 80篇 |
2003年 | 68篇 |
2002年 | 50篇 |
2001年 | 4篇 |
2000年 | 11篇 |
1999年 | 7篇 |
1998年 | 6篇 |
1997年 | 10篇 |
1996年 | 8篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 1篇 |
1992年 | 6篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1982年 | 3篇 |
1978年 | 1篇 |
1948年 | 1篇 |
1943年 | 1篇 |
1941年 | 1篇 |
1935年 | 1篇 |
1934年 | 2篇 |
排序方式: 共有2351条查询结果,搜索用时 15 毫秒
161.
162.
163.
164.
Discovery of A-type procyanidin dimers in yellow raspberries by untargeted metabolomics and correlation based data analysis 总被引:1,自引:0,他引:1
Elisabete Carvalho Pietro Franceschi Antje Feller Lorena Herrera Luisa Palmieri Panagiotis Arapitsas Samantha Riccadonna Stefan Martens 《Metabolomics : Official journal of the Metabolomic Society》2016,12(9):144
Introduction
Raspberries are becoming increasingly popular due to their reported health beneficial properties. Despite the presence of only trace amounts of anthocyanins, yellow varieties seems to show similar or better effects in comparison to conventional raspberries.Objectives
The aim of this work is to characterize the metabolic differences between red and yellow berries, focussing on the compounds showing a higher concentration in yellow varieties.Methods
The metabolomic profile of 13 red and 12 yellow raspberries (of different varieties, locations and collection dates) was determined by UPLC–TOF-MS. A novel approach based on Pearson correlation on the extracted ion chromatograms was implemented to extract the pseudospectra of the most relevant biomarkers from high energy LC–MS runs. The raw data will be made publicly available on MetaboLights (MTBLS333).Results
Among the metabolites showing higher concentration in yellow raspberries it was possible to identify a series of compounds showing a pseudospectrum similar to that of A-type procyanidin polymers. The annotation of this group of compounds was confirmed by specific MS/MS experiments and performing standard injections.Conclusions
In berries lacking anthocyanins the polyphenol metabolism might be shifted to the formation of a novel class of A-type procyanidin polymers.165.
Comparisons of microsatellites and single‐nucleotide polymorphisms (SNPs) have found that SNPs outperform microsatellites in population genetic analyses, questioning the continued utility of microsatellites in population and landscape genetics. Yet, highly polymorphic markers may be of value in species that have reduced genetic variation. This study repeated previous analyses that used microsatellites with SNPs developed from ddRAD sequencing in the black‐capped vireo source‐sink system. SNPs provided greater resolution of genetic diversity, population differentiation, and migrant detection but could not reconstruct parentage relationships due to insufficient heterozygosities. The biological inferences made by both sets of markers were similar: asymmetrical gene flow from source sites to the remaining sink sites. With the landscape genetic analyses, we found different results between the two molecular markers, but associations of the top environmental features (riparian, open habitat, agriculture, and human development) with dispersal estimates were shared between marker types. Despite the higher precision of SNPs, we find that microsatellites effectively uncover population processes and patterns and are superior for parentage analyses in this species with reduced genetic diversity. This study illustrates the continued applicability and relevance of microsatellites in population genetic research. 相似文献
166.
Andreassi MG Botto N Cocci F Battaglia D Antonioli E Masetti S Manfredi S Colombo MG Biagini A Clerico A 《Human genetics》2003,112(2):171-177
Elevated levels of plasma homocysteine (Hcy), a risk factor for coronary artery disease (CAD), can result from genetic errors, e.g., the methylenetetrahydrofolate reductase (MTHFR) polymorphism, or nutritional deficiencies, e.g., in vitamin B12 and folate. The mechanism by which Hcy induces atherosclerosis is not fully understood. Recently, Hcy has also been observed to induce DNA damage. In this study, we have investigated whether DNA damage is related to the C677T variant in the MTHFR gene and to plasma levels of Hcy, B12, and folate in patients with CAD. Patients ( n=46) with angiographically proven CAD were studied by using the micronucleus (MN) test, an accepted method for evaluating genetic instability. TT patients had plasma Hcy levels higher than those with the CT or CC genotypes (27.8+/-5.2 vs 13.7+/-2.2 and 12.9+/-1.9 micro mol/l, respectively; P=0.02). Patients with multi-vessel disease had higher plasma Hcy levels (11.6+/-1.2, 22.0+/-4.7, 19.3+/-3.9 micromol/l for one-, two- and three-vessel disease, respectively; P=0.05). The MN index increased with the number of affected vessels (8.4+/-0.7, 11.1+/-2.0, 14.2+/-1.7 for one-, two-, and three-vessels disease, respectively; P=0.02) and was significantly higher in subjects with the TT genotype compared with the CC or CT genotypes (15.7+/-2.4 vs 8.9+/-1.7 and 9.9+/-0.8; P=0.02). The MN index was also correlated negatively with plasma B12 concentration ( r=-0.343; P=0.019) and positively with plasma Hcy ( r=0.429, P=0.005). These data indicate that the MN index is associated with the severity of CAD and is related to the MTHFR polymorphism, suggesting an interesting link between coronary atherosclerosis and genetic instability in humans. 相似文献
167.
168.
Devlin Shawn P. Tappenbeck Samantha K. Craft James A. Tappenbeck Tyler H. Chess Dale W. Whited Diane C. Ellis Bonnie K. Stanford Jack A. 《Ecosystems》2017,20(1):183-197
Ecosystems - Invasion of Mysis diluviana from upstream stockings drastically altered the food web of 480 km2 Flathead Lake, Montana (USA). Mysis increased exponentially after establishment in 1982,... 相似文献
169.
170.
Gerhold RW Tate CM Gibbs SE Mead DG Allison AB Fischer JR 《Journal of wildlife diseases》2007,43(1):129-135
Mourning doves (Zenaida macroura) are the most abundant and widespread native member of the columbid family, as well as a major migratory game species, in the United States. However, there is little information on mortality factors in mourning doves. Records of necropsy accessions at the Southeastern Cooperative Wildlife Disease Study (SCWDS) from 15 southeastern states, from 1971 through 2005, were reviewed. One hundred thirty-five mourning doves were submitted from nine states during the 35-yr period. Trichomonosis constituted 40% (n = 54) of all diagnoses and was the most frequent diagnosis. Toxicoses and avian pox constituted 18.5% (n = 25) and 14.8% (n = 20) of all diagnoses, respectively. Remaining diagnoses included trauma, suspected toxicosis, Ascaridia columbae infection, suspected tick paralysis, and undetermined. Adults were observed more frequently with trichomonosis (94.1%) and toxicoses (68%) as compared to juveniles, but a gender predisposition was not apparent for either disease. Age and gender predilections were not apparent for cases of avian pox. The majority of the trichomonosis and avian pox cases were observed in the spring-summer, whereas the majority of the toxicosis cases were observed in the winter-spring. Additionally, the Georgia Department of Human Resources-Division of Public Health and West Virginia Department of Health and Human Resources submitted 809 mourning doves to SCWDS from 2001 through 2005 for West Nile virus surveillance efforts. West Nile virus was isolated from 2.1% (n = 17) and eastern equine encephalitis virus (EEEV) was isolated from 0.2% (n = 2) of the submitted birds. 相似文献