全文获取类型
收费全文 | 1982篇 |
免费 | 95篇 |
出版年
2021年 | 15篇 |
2020年 | 15篇 |
2019年 | 13篇 |
2018年 | 25篇 |
2017年 | 17篇 |
2016年 | 26篇 |
2015年 | 66篇 |
2014年 | 68篇 |
2013年 | 98篇 |
2012年 | 121篇 |
2011年 | 121篇 |
2010年 | 66篇 |
2009年 | 51篇 |
2008年 | 101篇 |
2007年 | 73篇 |
2006年 | 85篇 |
2005年 | 74篇 |
2004年 | 80篇 |
2003年 | 72篇 |
2002年 | 75篇 |
2001年 | 37篇 |
2000年 | 46篇 |
1999年 | 42篇 |
1998年 | 30篇 |
1997年 | 23篇 |
1996年 | 28篇 |
1995年 | 18篇 |
1994年 | 20篇 |
1993年 | 18篇 |
1992年 | 35篇 |
1991年 | 27篇 |
1990年 | 37篇 |
1989年 | 39篇 |
1988年 | 36篇 |
1987年 | 29篇 |
1986年 | 33篇 |
1985年 | 33篇 |
1984年 | 28篇 |
1983年 | 18篇 |
1982年 | 22篇 |
1981年 | 21篇 |
1980年 | 13篇 |
1979年 | 26篇 |
1978年 | 24篇 |
1977年 | 11篇 |
1975年 | 15篇 |
1974年 | 17篇 |
1973年 | 21篇 |
1972年 | 13篇 |
1970年 | 14篇 |
排序方式: 共有2077条查询结果,搜索用时 92 毫秒
71.
72.
Bente Christiansen Jens Pete Lomholt Kjell Johansen 《Environmental Biology of Fishes》1982,7(3):291-296
Synopsis Oxygen uptake (Vo
2) was measured in carp of approximately 40 cm length swimming at controlled variable oxygen tensions (Po
2). At Po
2> 120 mm Hg Vo
2 increased with an increase in swimming speed from 5.6 to 11.3 cm · sec–1. Extrapolation of Vo
2 to zero activity at Po
2 = 140 mm Hg revealed a standard O2 uptake of 36.7 ml O2 · kg–1 · h–1 at 20° C. At the lowest swimming speed (5.6 cm · s–1) the oxygen uptake increased when the water Po
2 was reduced. A near doubling in Vo
2 was seen at Po
2 = 70 mm Hg compared to 140 mm Hg. At higher swimming speeds in hypoxic water Vo
2 decreased relative to the values at low swimming speeds. As a result the slope of the lines expressing log Vo
2 as a function of swimming speed decreased from positive to negative values with decreasing Po
2 of the water. pH of blood from the caudal vein drawn before and at termination of swimming at Po
2 = 70 mm Hg and 100 mm Hg did not show any decrease in relation to rest values at Po
2 = 140 mm Hg. Blood lactate concentration did not increase during swimming at these tensions. 相似文献
73.
M Hansson M Beran B Andersson R Kiessling 《Journal of immunology (Baltimore, Md. : 1950)》1982,129(1):126-132
This study demonstrates the ability of human NK cells to inhibit in vitro granulopoiesis of autologous and allogeneic BM cells. NK lytic activity and GM-CFC inhibition was present among nonstimulated lymphocytes from healthy donors and could be increased by treatment of PBL with IFN. Both the cytotoxic NK cells and the GM-CFC inhibitory cells could be enriched for among nonadherent, low-density cells. High-density cells were not cytotoxic, only inhibitory to a small extent, and could become neither cytotoxic nor more inhibitory after IFN treatment. In contrast, low-density cells showed an increased cytotoxic and GM-CFC inhibitory capacity after IFN treatment. The NK mediated GM-CFC inhibition was dependent on cell contact with BM cells, increased with longer preincubation times, and was most efficient against 7-day GM-CFC as compared with 14 day GM-CFC progenitors. In conclusion, these data provide new information about the human NK cell as a potent inhibitor of in vitro granulopoiesis and also as a possible regulator of hematopoiesis in vivo. 相似文献
74.
Abstract: This paper reports on the electrophoretic protein/polypeptide pattern of a rat brain primary culture. For comparison, the polypeptide pattern of neuronal and glial enriched fractions from adult rat brain and cerebral hemispheres from newborn and adult rat have been analysed. Water-soluble and SDS-extractable polypeptide fractions appeared and/or increased in amount in the cultures until confluency. The polypeptide pattern of the cultures most resembled that of the glial cell fractions, showing some of this fraction's specificity. Removal of fetal calf serum and addition of 0.1 mM dibutyryl cyclic adenosine monophosphate (dB-cAMP) produced few changes in the electrophoretic pattern. The study thus provides evidence in favour of the astroglial nature of the brain primary culture. It also shows that the cells undergo some maturation in the culture. 相似文献
75.
76.
77.
78.
1. Pyruvate carboxylase is present in brown adipose tissue mitochondria. 2. In isolated mitochondria, pyruvate, bicarbonate and ATP, the substrates for pyruvate carboxylase, are able to replace added malate in supplying a condensing partner for acetyl-CoA formed from beta-oxidation of fatty acids. 3. In brown adipocytes, pyruvate and CO2 increase the rate of norepinephrine-stimulated respiration synergistically. 4. The norepinephrine-stimulated respiration in brown adipocytes is diminished when pyruvate transport into the mitochondria is inhibited. 5. Pyruvate carboxylation increases the intramitochondrial level of citric acid cycle intermediates, as shown by titrations of malonate inhibition of respiration. 6. Pyruvate carboxylation can continuously supply the mitochondria with citric acid cycle intermediates, as evidenced by its ability to maintain respiration when oxoglutarate conversion to glutamate is stimulated. 7. Pyruvate carboxylation is necessary for maximal oxygen consumption even when drainage of the citric acid cycle for amino acid synthesis is eliminated. 8. Pyruvate carboxylation explains observed effects of CO2 on respiration in brown adipocytes, and may also explain the increased glucose uptake by brown adipose tissue during thermogenesis in vivo. 相似文献
79.
P Kirveskari H Hansson B Hedegard U Karlsson 《American journal of physical anthropology》1978,48(1):107-112
The teeth of modern Skolt Lapps from northern Finland are considerably larger than those of their ancestors of the Eighteenth Century. The increase is probably attributable to improved nutrition. One or more teeth, excluding the third molars, were congenitally missing in 18.8% of the population aged 5 to 20 years. Relative to a standard the anterior teeth are larger than the posterior teeth, particularly the premolars. This accords well with the hypodontia pattern which is dominated by premolar agenesis. 相似文献
80.