全文获取类型
收费全文 | 389篇 |
免费 | 32篇 |
出版年
2021年 | 7篇 |
2020年 | 6篇 |
2019年 | 13篇 |
2018年 | 5篇 |
2017年 | 5篇 |
2016年 | 10篇 |
2015年 | 12篇 |
2014年 | 9篇 |
2013年 | 10篇 |
2012年 | 12篇 |
2011年 | 14篇 |
2010年 | 11篇 |
2009年 | 8篇 |
2008年 | 8篇 |
2007年 | 4篇 |
2006年 | 14篇 |
2005年 | 9篇 |
2004年 | 6篇 |
2003年 | 5篇 |
2002年 | 6篇 |
2001年 | 6篇 |
2000年 | 6篇 |
1999年 | 8篇 |
1998年 | 10篇 |
1996年 | 5篇 |
1995年 | 5篇 |
1994年 | 7篇 |
1992年 | 10篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 9篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 15篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1979年 | 8篇 |
1977年 | 13篇 |
1976年 | 17篇 |
1975年 | 9篇 |
1974年 | 6篇 |
1973年 | 4篇 |
1970年 | 4篇 |
1969年 | 5篇 |
1968年 | 5篇 |
1967年 | 7篇 |
1959年 | 3篇 |
1958年 | 3篇 |
排序方式: 共有421条查询结果,搜索用时 15 毫秒
81.
82.
Muscle mass as a factor limiting physical work 总被引:4,自引:0,他引:4
Shephard R. J.; Bouhlel E.; Vandewalle H.; Monod H. 《Journal of applied physiology》1988,64(4):1472-1479
Maximal exercise has been performed by eight men and eight women, using four types of ergometer (2-leg, 1-leg, arm + shoulder, and arm) while breathing room air and while breathing 12% O2. Results have been related to anthropometric estimates of muscle mass in the active limbs. Although significant sex differences of O2 transfer and power output are shown, the sex-specific aerobic performance was roughly proportional to active muscle volume (both when comparing individuals on a given type of ergometer and when comparing average scores of the several types of ergometer). However, the relationship was closer for steady power output than for peak O2 intake (where the scores for arm work were boosted by the use of accessory muscles and by hyperventilation). When breathing 12% O2, the 2-leg performance was substantially reduced (an average of 28.7% for O2 transport and 19.2% for power output). This effect dropped to 9.1% for O2 transport and 12% for power output in one-leg ergometry and was negligible for arm or arm plus shoulder work. It is argued that because of difficulty in perfusing small muscles, arm work is limited largely by the intrinsic power of the active muscles, that single-leg ergometry is limited rather equally by central circulatory and muscular factors, and that two-leg ergometry is almost entirely dependent on the central circulatory transport of O2. 相似文献
83.
T J Verde S G Thomas R W Moore P Shek R J Shephard 《Journal of applied physiology》1992,73(4):1494-1499
Ten elite male runners (age, 29.8 +/- 1.7 yr; maximum oxygen consumption, 65.3 +/- 4.9 ml.kg-1.min-1; 10-km times, 31 min 43 s +/- 1 min 46 s) deliberately increased training schedules by an average of 38% for 3 wk. Resting heart rate and maximal oxygen intake were unchanged, but the heart rate response to acute exercise was decreased. Following heavy training, blood samples taken at rest showed trends to a decreased helper/suppressor cell ratio, an increased phytohemagglutinin (PHA)- and concanavalin (ConA)-stimulated lymphocyte proliferation, and a decreased production of immunoglobulins IgG and IgM. Whereas PHA-stimulated lymphocyte proliferation was initially unchanged by acute exercise, after 3 wk of heavy training the same acute exercise caused an 18% suppression of proliferation. Acute exercise following heavy training did not alter pokeweed-stimulated IgG or IgM synthesis. There was no correlation between changes in lymphocyte subpopulations, helper/suppressor ratios, and mitogen-induced cellular proliferation. The immune system of endurance-trained athletes at rest seemed to tolerate the stress of heavy training, but superimposition of a bout of acute exercise on the chronic stress of heavy training resulted in immunosuppression, which was transient and most likely not of clinical significance. 相似文献
84.
K. L. Shephard 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1992,162(3):231-240
Summary An isolated and perfused fish gill filament preparation has been developed to facilitate investigations on the fish gill microclimate. Measurements have been made of the concentration of sodium at the lamellar surface and in the mixed-exit water, and of the maximum interlamellar velocity. When the external water has a sodium concentration of 0.10 mmol · 1-1, water at the gill surface has a mean sodium concentration of 0.146 mmol · 1-1. Mixed-exit water, 50 m behind the perfused filament, has a mean sodium concentration of 0.118 mmol · 1-1. When the water flowing over the filament has a maximum velocity of 18 cm · s-1, the maximum velocity between secondary lamellae is 1.5 cm · s-1. These measurements have been used to support the development of a velocity-modified diffusion model which describes ion movement in the interlamellar space. The analysis and observations on the preparation suggest that substantial unstirred layers do not exist at the lamellar surfaces in this preparation. Simple diffusion to and from the tissue surfaces, in conjunction with parabolic velocity profiles within the interlamellar spaces adequately explain net sodium movements. 相似文献
85.
Obesity‐induced mitochondrial dysfunction in porcine adipose tissue‐derived mesenchymal stem cells 下载免费PDF全文
86.
Compensatory substitutions and the evolution of the mitochondrial 12S rRNA gene in mammals 总被引:5,自引:2,他引:3
12S ribosomal RNA (rRNA) gene sequences from a suite of mammalian taxa (13
placentals, 4 marsupials, 1 monotreme), for which phylogenetic
relationships are well established based on independent criteria, were
employed to study the evolution of this gene. Phylogenetic analysis of 12S
sequences produces a phylogeny that agrees with expectations. Base
composition provides evidence for directional symmetrical substitution
pressure in loops; in stems, base composition is much more even. Rates of
nucleotide substitution are lower in stems than loops. Patterns of
nucleotide substitution show an overall preference for transitions over
transversions, with this difference more profound in stems than loops.
Among different transversion pathways, there is a wide range of
transformation frequencies. An analysis of compensatory substitutions shows
that there is strong evidence for their occurrence and that a weighting
factor of 0.61 should be applied in phylogenetic analyses to account for
the dependence of mutations at stem positions relative to positions where
changes are independent. Among stem variables (i.e., stem length,
interaction distance, substitution rates, G+C content, and the percentage
of bases that are paired), several significant correlations were
discovered, but stem length and interaction distance are uncorrelated with
other variables.
相似文献
87.
We investigated the prevalence and phenotypic variation of Candida species in oral lichen planus (OLP) and the therapeutic implications of our findings. Eighty patients with clinically and histopathologically confirmed cases of OLP (64 non-erosive, 16 erosive) and a control group of 80 healthy individuals with no predisposing factors for oral candidiasis were examined for evidence of Candida infection. Oral swabs and smears were obtained for cytology and culture. Identification, speciation and antifungal susceptibility tests of Candida isolates were performed using an automated microbial identification system. Fifty percent of erosive OLP cases, 28% of non-erosive cases and none of the controls showed evidence of Candida. Candida albicans was found predominantly in non-erosive OLP, while other Candida species were predominate in erosive OLP. Non-Candida albicans isolates (C. glabrata, C. krusei) were resistant to the commonly used antifungals, clotrimazole and fluconazole. Candida infection is common in cases of OLP. We recommend antifungal sensitivity testing prior to antifungal therapy for the erosive form of OLP. 相似文献
88.
89.
The ability of chloroplasts isolated from Acetabulana mediterranea to synthesize the protein amino acids has been investigated. When this chloroplast isolate was presented with 14CO2 for periods of 6–8 hr, tracer was found in essentially all amino acid species of their hydrolyzed protein Phenylalanine labeling was not detected, probably due to technical problems, and hydroxyproline labeling was not tested for The incorporation of 14CO2 into the amino acids is driven by light and, as indicated by the amount of radioactivity lost during ninhydrin decarboxylation on the chromatograms, the amino acids appear to be uniformly labeled. The amino acid labeling pattern of the isolate is similar to that found in plastids labeled with 14CO2 in vivo. The chloroplast isolate did not utilize detectable amounts of externally supplied amino acids in light or, with added adenosine triphosphate (ATP), in darkness. It is concluded that these chloroplasts are a tight cytoplasmic compartment that is independent in supplying the amino acids used for its own protein synthesis. These results are discussed in terms of the role of contaminants in the observed synthesis, the "normalcy" of Acetabularia chloroplasts, the synthetic pathways for amino acids in plastids, and the implications of these observations for cell compartmentation and chloroplast autonomy. 相似文献
90.
Sexual differentiation of rat liver carbonic anhydrase III 总被引:5,自引:0,他引:5
A Shiels S Jeffery I R Phillips E A Shephard C A Wilson N D Carter 《Biochimica et biophysica acta》1983,760(3):335-342
Using radioimmunoassay, the concentration of carbonic anhydrase III in the livers of adult male rats was found to be approx. 30-times greater than that observed in mature females. Castration of male rats led to a marked reduction in liver carbonic anhydrase III concentrations which could be partially restored to control levels by testosterone replacement. Administration of testosterone to ovariectomised female rats induced about a 5-fold increase in liver carbonic anhydrase III concentration. Immunoprecipitation analysis of the products of liver mRNA translation in vitro with antiserum specific for carbonic anhydrase III showed that hormonal control of the levels of carbonic anhydrase III in liver is mediated by changes in the amount of translatable carbonic anhydrase III mRNA. Marked changes in liver carbonic anhydrase III concentrations were also observed in developing and ageing male rats. 相似文献