全文获取类型
收费全文 | 175篇 |
免费 | 11篇 |
国内免费 | 9篇 |
专业分类
195篇 |
出版年
2023年 | 2篇 |
2022年 | 2篇 |
2020年 | 1篇 |
2019年 | 3篇 |
2018年 | 3篇 |
2017年 | 2篇 |
2016年 | 1篇 |
2015年 | 13篇 |
2014年 | 10篇 |
2013年 | 12篇 |
2012年 | 8篇 |
2011年 | 14篇 |
2010年 | 9篇 |
2009年 | 11篇 |
2008年 | 7篇 |
2007年 | 6篇 |
2006年 | 9篇 |
2005年 | 2篇 |
2004年 | 4篇 |
2003年 | 6篇 |
2002年 | 3篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 3篇 |
1998年 | 7篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 6篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1955年 | 1篇 |
1954年 | 2篇 |
排序方式: 共有195条查询结果,搜索用时 5 毫秒
21.
Molecular phylogeny and divergence times of drosophilid species 总被引:17,自引:15,他引:17
The phylogenetic relationships and divergence times of 39 drosophilid
species were studied by using the coding region of the Adh gene. Four
genera--Scaptodrosophila, Zaprionus, Drosophila, and Scaptomyza (from
Hawaii)--and three Drosophila subgenera--Drosophila, Engiscaptomyza, and
Sophophora--were included. After conducting statistical analyses of the
nucleotide sequences of the Adh, Adhr (Adh-related gene), and nuclear rRNA
genes and a 905-bp segment of mitochondrial DNA, we used Scaptodrosophila
as the outgroup. The phylogenetic tree obtained showed that the first major
division of drosophilid species occurs between subgenus Sophophora (genus
Drosophila) and the group including subgenera Drosophila and Engiscaptomyza
plus the genera Zaprionus and Scaptomyza. Subgenus Sophophora is then
divided into D. willistoni and the clade of D. obscura and D. melanogaster
species groups. In the other major drosophilid group, Zaprionus first
separates from the other species, and then D. immigrans leaves the
remaining group of species. This remaining group then splits into the D.
repleta group and the Hawaiian drosophilid cluster (Hawaiian Drosophila,
Engiscaptomyza, and Scaptomyza). Engiscaptomyza and Scaptomyza are tightly
clustered. Each of the D. repleta, D. obscura, and D. melanogaster groups
is monophyletic. The splitting of subgenera Drosophila and Sophophora
apparently occurred about 40 Mya, whereas the D. repleta group and the
Hawaiian drosophilid cluster separated about 32 Mya. By contrast, the
splitting of Engiscaptomyza and Scaptomyza occurred only about 11 Mya,
suggesting that Scaptomyza experienced a rapid morphological evolution. The
D. obscura and D. melanogaster groups apparently diverged about 25 Mya.
Many of the D. repleta group species studied here have two functional Adh
genes (Adh-1 and Adh-2), and these duplicated genes can be explained by two
duplication events.
相似文献
22.
CA Kalva-Filho EZ Campos VL Andrade ASR Silva AM Zagatto MCS Lima M Papoti 《Biology of sport / Institute of Sport》2015,32(4):333-337
The aims of the present study were to investigate the relationship of aerobic and anaerobic parameters with 400 m performance, and establish which variable better explains long distance performance in swimming. Twenty-two swimmers (19.1±1.5 years, height 173.9±10.0 cm, body mass 71.2±10.2 kg; 76.6±5.3% of 400 m world record) underwent a lactate minimum test to determine lactate minimum speed (LMS) (i.e., aerobic capacity index). Moreover, the swimmers performed a 400 m maximal effort to determine mean speed (S400m), peak oxygen uptake () and total anaerobic contribution (CANA). The CANA was assumed as the sum of alactic and lactic contributions. Physiological parameters of 400 m were determined using the backward extrapolation technique ( and alactic contributions of CANA) and blood lactate concentration analysis (lactic anaerobic contributions of CANA). The Pearson correlation test and backward multiple regression analysis were used to verify the possible correlations between the physiological indices (predictor factors) and S400m (independent variable) (p < 0.05). Values are presented as mean ± standard deviation. Significant correlations were observed between S400m (1.4±0.1 m·s-1) and LMS (1.3±0.1 m·s-1; r = 0.80), (4.5±3.9 L·min-1; r = 0.72) and CANA (4.7±1.5 L·O2; r= 0.44). The best model constructed using multiple regression analysis demonstrated that LMS and explained 85% of the 400 m performance variance. When backward multiple regression analysis was performed, CANA lost significance. Thus, the results demonstrated that both aerobic parameters (capacity and power) can be used to predict 400 m swimming performance. 相似文献
23.
Polyana C Tizioto Jeremy F Taylor Jared E Decker Caio F Gromboni Mauricio A Mudadu Robert D Schnabel Luiz L Coutinho Gerson B Mour?o Priscila SN Oliveira Marcela M Souza James M Reecy Renata T Nassu Flavia A Bressani Patricia Tholon Tad S Sonstegard Mauricio M Alencar Rymer R Tullio Ana RA Nogueira Luciana CA Regitano 《遗传、选种与进化》2015,47(1)
24.
25.
A. Nock 《Chromosoma》1981,83(2):209-220
Nuclear and cytoplasmic RNA of Stylonychia mytilus were analyzed on denaturing polyacrylamide gels. The molecular weight of rRNA precursor molecules is within a range of 2.1×106 daltons. A comparison between the electrophoretic pattern of nuclear non-ribosomal RNA and cytoplasmic mRNA indicates that a considerable amount of nuclear RNA sequences is of higher molecular weight than cytoplasmic RNA sequences. The molecular weight distribution of cytoplasmic RNA supports the assumption that also in Stylonychia an average sized mRNA molecule contains 1,200–1,500 nucleotides according to a molecular weight of 4×105 to 5×105 daltons. The size of the polyadenylic acid fragment of poly-A+ RNA molecules is about 120 nucleotides. The total mass of cytoplasmic RNA is around 7.5/1010 g/cell, corresponding to 1.2×107 average sized mRNA molecules per cell. RNA excess hybridization experiments show that 60% of the DNA sequences are transcribed into nuclear RNA and that the cytoplasmic mRNA sequences are homologous to about 40% of macronuclear DNA sequences. There is no indication of different frequency classes within the mRNA. The number of different mRNA species in a Stylonychia cell is 1.2–1.5×104. On the average each of them is present about 1,000 times in every cell. 相似文献
26.
Chiang CW Liu CT Lettre G Lange LA Jorgensen NW Keating BJ Vedantam S Nock NL Franceschini N Reiner AP Demerath EW Boerwinkle E Rotter JI Wilson JG North KE Papanicolaou GJ Cupples LA;Genetic Investigation of ANthropometric Traits 《Genetics》2012,192(1):253-266
Ultraconserved elements in the human genome likely harbor important biological functions as they are dosage sensitive and are able to direct tissue-specific expression. Because they are under purifying selection, variants in these elements may have a lower frequency in the population but a higher likelihood of association with complex traits. We tested a set of highly constrained SNPs (hcSNPs) distributed genome-wide among ultraconserved and nearly ultraconserved elements for association with seven traits related to reproductive (age at natural menopause, number of children, age at first child, and age at last child) and overall [longevity, body mass index (BMI), and height] fitness. Using up to 24,047 European-American samples from the National Heart, Lung, and Blood Institute Candidate Gene Association Resource (CARe), we observed an excess of associations with BMI and height. In an independent replication panel the most strongly associated SNPs showed an 8.4-fold enrichment of associations at the nominal level, including three variants in previously identified loci and one in a locus (DENND1A) previously shown to be associated with polycystic ovary syndrome. Finally, using 1430 family trios, we showed that the transmissions from heterozygous parents to offspring of the derived alleles of rare (frequency ≤0.5%) hcSNPs are not biased, particularly after adjusting for the rates of genotype missingness and error in the data. The lack of transmission bias ruled out an immediately and strongly deleterious effect due to the rare derived alleles, consistent with the observation that mice homozygous for the deletion of ultraconserved elements showed no overt phenotype. Our study also illustrated the importance of carefully modeling potential technical confounders when analyzing genotype data of rare variants. 相似文献
27.
28.
The Australian freshwater cod genus, Maccullochella is represented by three species: Murray cod, M. peelii
peelii, eastern freshwater cod, M. ikei, and trout cod, M.macquariensis. Seven novel microsatellite loci from M. ikei and six previously published loci from M. peelii peelii were tested on wild populations of Murray, eastern and trout cod. Levels of polymorphism varied between species with 13 loci
polymorphic in Murray cod, 9 in trout cod and 7 in eastern cod. Observed heterozygosities ranged from 0.053 to 0.842. This
suite of microsatellite loci will facilitate future studies of the genetic status of wild and hatchery bred populations of
Maccullochella. 相似文献
29.
Anastasia Nikolopoulou Theodosia Maina Petros Sotiriou Paul Cordopatis Berthold A. Nock 《Journal of peptide science》2006,12(2):124-131
Two somatostatin analogues, [99mTc]Demotide and [99mTc]Demotate 4, were compared with [99mTc]Demotate 1, a previously reported somatostatin receptor subtype 2 (sst2) targeting tracer. Conjugates were prepared by coupling an open‐chain tetraamine chelator to D ‐Phe1 of [Tyr3]‐octreotide or [Tyr3]‐octreotate, respectively, via a p‐benzylaminodiglycolic acid spacer adopting solid‐phase peptide synthesis techniques. Peptide conjugates were collected in a highly pure form after chromatographic purification. Eventually, [99mTc]Demotide and [99mTc]Demotate 4 were obtained in ~1 Ci/µmol specific activity and >96% purity after labeling under alkaline conditions. Demotide and Demotate 4 exhibited similar high binding affinities for the sst2 expressed in AR4‐2J cells with IC50 values 0.16 and 0.10 nM, respectively. The (radio)metallated analogues [99mTc]Demotide and [99mTc]Demotate 4 showed equally high affinities to the sst2 during saturation binding assays in AR4‐2J cell membranes (Kds 0.08 and 0.07 nM, respectively). During incubation at 37 °C with AR4‐2J cells, the radiopeptides internalized effectively via a receptor‐mediated process, with [99mTc]Demotate 4 exhibiting a faster internalization rate than [99mTc]Demotide. After injection in athymic mice bearing sst2‐expressing AR4‐2J tumors, the radiotracers showed high and specific uptake in the tumor (>25%ID/g at 1 h) and in the sst2–positive organs. However, both [99mTc]Demotide and [99mTc]Demotate 4 showed unfavorably higher background activity, especially in the abdomen, in comparison to [99mTc]Demotate 1 and are, therefore, less suited than [99mTc]Demotate 1 for sst2‐targeted tumor imaging in man. Copyright © 2005 European Peptide Society and John Wiley & Sons, Ltd. 相似文献
30.