全文获取类型
收费全文 | 653篇 |
免费 | 62篇 |
国内免费 | 1篇 |
出版年
2022年 | 3篇 |
2021年 | 7篇 |
2020年 | 5篇 |
2018年 | 4篇 |
2017年 | 3篇 |
2016年 | 9篇 |
2015年 | 24篇 |
2014年 | 22篇 |
2013年 | 34篇 |
2012年 | 35篇 |
2011年 | 35篇 |
2010年 | 25篇 |
2009年 | 30篇 |
2008年 | 23篇 |
2007年 | 28篇 |
2006年 | 35篇 |
2005年 | 26篇 |
2004年 | 32篇 |
2003年 | 38篇 |
2002年 | 32篇 |
2001年 | 23篇 |
2000年 | 30篇 |
1999年 | 25篇 |
1998年 | 15篇 |
1997年 | 12篇 |
1996年 | 11篇 |
1995年 | 8篇 |
1994年 | 11篇 |
1993年 | 13篇 |
1992年 | 8篇 |
1991年 | 14篇 |
1990年 | 9篇 |
1989年 | 5篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 10篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 7篇 |
1981年 | 2篇 |
1979年 | 3篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1967年 | 5篇 |
1966年 | 4篇 |
1965年 | 2篇 |
1946年 | 1篇 |
1943年 | 1篇 |
排序方式: 共有716条查询结果,搜索用时 15 毫秒
11.
Tremblay A.; Poehlman E. T.; Nadeau A.; Dussault J.; Bouchard C. 《Journal of applied physiology》1987,62(2):539-544
The present study investigated the role of heredity in determining changes in the energy cost of submaximal exercise in response to short-term overfeeding. Six pairs of monozygotic twins were subjected to a 1,000 kcal/day surplus for 22 days with careful experimental controls over food intake and physical activities. O2 consumption (VO2) was measured during a submaximal treadmill exercise test 165 min postprandially before and the morning after the overfeeding protocol. As expected, overfeeding induced significant increases in body weight and fat mass. No significant increase in mean exercise VO2 was observed after overfeeding. However, the interindividual variation in overfeeding-induced changes in exercise VO2 was large and not randomly distributed. When comparing intrapair variance for changes in exercise VO2 to interpair variance, a moderate to high within-pair resemblance in response, i.e., a genotype-overfeeding interaction, was observed. Changes in exercise VO2 were positively correlated with those in postexercise levels of blood catecholamines, particularly epinephrine. A negative correlation was found between changes in exercise VO2 and body fat gain. These results are consistent with the concept of a role for the sympathoadrenal system in the regulation of adaptive thermogenesis and the predisposition to store fat. Moreover, these data suggest that the sensitivity to adapt in exercise energy expenditure after overfeeding is inherited to a significant extent. 相似文献
12.
Summary Red blood cell esterase D (ESD) polymorphism was studied in a French-Canadian population from Quebec city, Canada, by means of high voltage electrophoresis on agarose gel followed, in heterozygotes for ESD1, by IEF to reveal the possible allele ESD*5. Frequencies of the ESD alleles in 904 unrelated individuals were ESD*1: 0.888, EDS*2: 0.095 and ESD*5: 0.017. The segregation pattern observed in 275 families confirmed a Mendelian inheritance of three autosomal alleles. 相似文献
13.
A mass in the neck, facial pain and cranial nerve palsies are the most common presenting symptoms of malignant tumours of the nasopharynx. Surgery is limited to biopsy for histological diagnosis. External irradiation is the treatment of choice, both for the primary lesion and the regional and distant metastases. Illustrative case histories are presented in detail. Experience over a 20-year period demonstrates that a 20% five-year survival rate has been obtained. 相似文献
14.
To investigate the mechanism by which the large T antigen (T-Ag) of polyomavirus and simian virus 40 can promote recombination in mammalian cells, we analyzed homologous recombination events occurring between two defective copies of the polyomavirus middle T (pmt) oncogene lying in close proximity on the same chromosome in a rat cell line. Reconstitution of a functional pmt gene by spontaneous recombination occurred at a rate of about 2 x 10(-7) per cell generation. Introduction of the polyomavirus large T (plt) oncogene into the cell line by DNA transfection promoted recombination very efficiently, with rates in the range of 10(-1) to 10(-2) per cell generation. Recombination was independent of any amplification of viral sequences and could even be promoted by the large T-Ag from simian virus 40, which cannot activate polyomavirus DNA replication. To explain the role of large T-Ag, we propose a novel mechanism of nonconservative recombination involving slipped-strand mispairing between the two viral repeats followed by gap repair synthesis. 相似文献
15.
Cardiovascular risk factors in a French-Canadian population: resolution of genetic and familial environmental effects on blood pressure by using extensive information on environmental correlates. 总被引:10,自引:8,他引:2 下载免费PDF全文
L Prusse T Rice C Bouchard G P Vogler D C Rao 《American journal of human genetics》1989,45(2):240-251
Genetic and environmental influences on systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial blood pressure (MBP) were examined in 371 French-Canadian families by using path analysis. Familial environment was estimated with environmental indices constructed from as many as 14 (of a pool of more than 100) correlates of blood pressure (BP). Approximately 20% of the variance in BP can be accounted for by the composite index, and the types of variables and the direction of their effects vary as a function of age and of the multivariate context. Path analysis of the family data suggests that genetic heritability is relatively high in children (from 0.49 for SBP to 0.56 for MBP) but much smaller in adults (from 0.08 for DBP to 0.18 for SBP). The proportion of variability explained by familial environment is estimated to be the same in children and adults and is much higher than reported to date (from 0.30 for SBP to 0.42 for DBP). In addition, sibships share significant nontransmitted environmental effects, and there is no evidence to suggest specific maternal effects in the aggregation of BP. Two unique findings emerge from this study. First, unlike in most earlier studies, we were able to arrive at the same parsimonious model for each of the BP variables. Second, the familial environment accounts for a substantial proportion of the variability in BP, which has been considerably underestimated in earlier studies. 相似文献
16.
Ejaculates were collected form three mixed-breed male dogs daily for 3 d. The semen was diluted in either a nonfat dried milk solid-glucose (NFDMS-G) or egg yolk citrate (EYC) extender at a concentration of 25 x 10(6) sperm/ml. The diluted samples were exposed to three different storage temperatures (35, 22 and 4 degrees C). Three cooling rates (-1.0, -0.3 and -0.1 degrees C/min) were also investigated at the lowest storage temperature (4 degrees C). The semen was evaluated for total motility, progressive motility and velocity at 0, 6, 12, 24, 48, 72, 96 and 120 h after collection by two independent observers. Interactions between extenders, temperatures and time after collection were found for each of the variables. Nonfat dried milk solid-glucose diluent was superior to EYC (P<0.05) in preservating sperm motility parameters that were evaluated for most of the observations. The evaluated sperm motility parameters were also significantly superior (P<0.05) in semen stored at 4 degrees C than at 35 or 22 degrees C for most of the observations. The progressive motility and velocity of sperm in semen cooled at 4 degrees C in NFDMS-G were higher (P<0.05) at the fast and medium cooling rates (-1.0 and -0.3 degrees C) than at the slow cooling rate (-0.1 degrees C/min) at 24 and 72 h, and at 48 h, respectively. In conclusion, the present study suggests that canine spermatozoal motility is well preserved when a NFDMS-glucose extender is added to the semen and the semen is cooled at a medium or fast rate to a storage temperature of 4 degrees C. Additional studies are needed to evaluate the fertility of semen stored in this manner. 相似文献
17.
In Drosophila pseudoobscura, the amylase (Amy) multigene family is
contained within a series of inversions, or gene arrangements, on the third
chromosome. The Standard (ST), Santa Cruz (SC), and Tree Line (TL)
inversions are central to the phylogeny of arrangements, and have clusters
of other arrangements derived from them. The gene arrangements belonging to
each of these three clusters have a characteristic number of Amy genes,
ranging from three in ST to two in SC to one in TL. This distribution
pattern can reflect a history of either duplications or deletions, although
the data available in the past did not permit a decision between these
alternatives. We provide unambiguous evidence that three Amy genes were
present before the divergence of the ST, SC, and TL arrangements. Thus, the
current status of the Amy multigene family is the result of deletions in
the TL and SC arrangements, which created three new pseudogenes: TL
Amy2-psi, TL Amy3-psi, and SC Amy3- psi. Analysis of pseudogene sequences
revealed that, in the SC and ST arrangements, pseudogene evolution has been
retarded, most likely due to the homogenization effect of gene conversion.
Finally, by determining the original copy number, we have reconstructed the
evolutionary history of the Amy multigene family and linked it with the
evolution of the central gene arrangements.
相似文献
18.
Suzanne A. Adjoa Claude Bouchard Pieter Coetzer Tim D. Noakes France T. Dionne 《Human genetics》1994,93(3):347-348
A DNA polymorphism of the nuclear-encoded subunit Va of the human cytochrome c oxidase (COX), a mitochondrial respiratory enzyme, is reported. No polymorphism was detected in genes for the subunits IV and Vb of the same enzyme. 相似文献
19.
Claude Bouchard Angelo Tremblay Jean-Pierre Desprs Germain Thriault Andr Nadeauf Paul J. Lupien Sital Moorjani Denis Prudhomme Guy Fournier 《Obesity (Silver Spring, Md.)》1994,2(5):400-410
Seven pairs of young adult male identical twins completed a negative energy balance protocol during which they exercised on cycle ergometers twice a day, 9 out of 10 days, over a period of 93 days while being kept on a constant daily energy and nutrient intake. The total energy deficit caused by exercise above the estimated energy cost of body weight maintenance reached 244 ± 9.8 MJ (Mean ± SEM). Baseline energy intake was estimated over a period of 17 days preceding the negative energy balance protocol. Mean body weight loss was 5.0 kg (SEM = 0.6) (p <0.001) and it was entirely accounted for by the loss of fat mass (p <0.001). Fat-free mass was unchanged. Body energy losses reached 191 MJ (SEM = 24) (p <0.001) which represented about 78% of the estimated energy deficit. Subcutaneous fat loss was slightly more pronounced on the trunk than on the limbs as estimated from skinfolds, circumferences, and computed tomography (CT). The reduction in CT-assessed abdominal visceral fat was quite striking, from 81 cm2 (SEM = 5) to 52 cm2 (SEM = 6) (p <0.001). At the same submaximal power output level, subjects oxidized more lipids than carbohydrates after the program as indicated by the changes in the respiratory exchange ratio (p <0.05). Intrapair resemblance was observed for the changes in body weight (p <0.05), fat mass (P <0.01), percent fat (p <0.01), body energy content (p <0.01), sum of 10 skinfolds (p <0.01), abdominal visceral fat (p <0.01), fasting plasma triglycerides (p <0.05) and cholesterol (p <0.05), maximal oxygen uptake (p <0.05), and respiratory exchange ratio during submaximal work (p <0.01). We conclude that even though there were large individual differences in response to the negative energy balance and exercise protocol, subjects with the same genotype were more alike in responses than subjects with different genotypes particularly for body fat, body energy, and abdominal visceral fat changes. High lipid oxidizers and low lipid oxidizers during sub-maximal exercise were also seen despite the fact that all subjects had experienced the same exercise and nutritional conditions for about three months. 相似文献
20.
Segregation analysis of fat mass and other body composition measures derived from underwater weighing. 总被引:9,自引:4,他引:5
Segregation patterns of three body composition measures which were derived from underwater weighing were evaluated in a random sample of 176 French-Canadian families. Two of the variables can be considered as primary partitions of weight (fat mass [FM] and fat-free mass [FFM]), while the remaining variable (percent body fat [%BF]) is a derived index combining the measures of both fat and fat-free weight. This study represents the first report investigating major gene effects for these measures. Segregation analyses revealed that a major locus hypothesis could not be rejected for two of the three phenotypes. The single exception was FFM, for which nearly 60% of the variance was accounted for by a non-Mendelian major effect, which may reflect environmentally based commingling or may be in part a function of gene-environment interactions or correlations. In contrast to the results for FFM, the results for each of FM and %BF were similar and suggested a major locus which accounted for 45% of the variance, with an additional 22%-26% due to a multifactorial component. Given the similarity of the major gene characteristics for these two phenotypes, the possibility that the same gene underlies both measures warrants investigation. A reasonable hypothesis is to consider genes that may influence nutrient partitioning, as the family of candidate genes to receive the major attention. 相似文献