全文获取类型
收费全文 | 5302篇 |
免费 | 576篇 |
国内免费 | 1篇 |
专业分类
5879篇 |
出版年
2022年 | 32篇 |
2021年 | 55篇 |
2020年 | 35篇 |
2019年 | 44篇 |
2018年 | 42篇 |
2017年 | 47篇 |
2016年 | 98篇 |
2015年 | 173篇 |
2014年 | 172篇 |
2013年 | 245篇 |
2012年 | 318篇 |
2011年 | 356篇 |
2010年 | 221篇 |
2009年 | 207篇 |
2008年 | 286篇 |
2007年 | 337篇 |
2006年 | 301篇 |
2005年 | 326篇 |
2004年 | 331篇 |
2003年 | 299篇 |
2002年 | 332篇 |
2001年 | 76篇 |
2000年 | 51篇 |
1999年 | 91篇 |
1998年 | 83篇 |
1997年 | 75篇 |
1996年 | 63篇 |
1995年 | 58篇 |
1994年 | 60篇 |
1993年 | 61篇 |
1992年 | 59篇 |
1991年 | 46篇 |
1990年 | 53篇 |
1989年 | 50篇 |
1988年 | 47篇 |
1987年 | 46篇 |
1986年 | 43篇 |
1985年 | 46篇 |
1984年 | 62篇 |
1983年 | 51篇 |
1982年 | 48篇 |
1981年 | 48篇 |
1980年 | 38篇 |
1979年 | 35篇 |
1978年 | 36篇 |
1977年 | 44篇 |
1976年 | 40篇 |
1975年 | 27篇 |
1974年 | 29篇 |
1973年 | 43篇 |
排序方式: 共有5879条查询结果,搜索用时 15 毫秒
81.
Robert M. Malina John H. Himes Carol Dutton Stepick Francisca Gutierrez Lopez Peter H. Buschang 《American journal of physical anthropology》1981,54(3):327-336
Weight, stature, arm circumference, and the triceps skinfold were measured in 1,410 school children, 6 through 14 years of age, from two urban colonias in the city of Oaxaca de Juarez (n = 479), and from two rural Ladino (n = 467) and two rural Zapotec (n = 464) communities in the Valley of Oaxaca in southern Mexico. Children from rural Ladino communities and urban colonias are significantly taller, heavier, and more muscular than children in rural Zapotec communities. The differences between rural Ladino and urban colonia children favor the former, particularly for weight and stature. These observations thus suggest (1) that children in the rural, indigenous communities in the Valley of Oaxaca are relatively undernourished compared to children in Ladinoized and urban communities, and (2) that rural-to-urban migration does not necessarily result in improved growth status. 相似文献
82.
Robert M. Malina John H. Himes Carol Dutton Stepick Francisca Gutierrez Lopez Peter H. Buschang 《American journal of physical anthropology》1981,55(2):269-280
Weight, stature, arm circumference, and the triceps skinfold were measured in 1,410 school children, 6 through 14 years of age, from two urban colonias in the city of Oaxaca de Juarez (n = 479), and from two rural Ladino (n = 467) and two rural Zapotec (n = 464) communities in the Valley of Oaxaca in southern Mexico. Children from rural Ladino communities and urban colonias are significantly taller, heavier, and more muscular than children in rural Zapotec communities. The differences between rural Ladino and urban colonia children favor the former, particularly for weight and stature. These observations thus suggest (1) that children in the rural, indigenous communities in the Valley of Oaxaca are relatively undernourished compared to children in Ladinoized and urban communities, and (2) that rural-to-urban migration does not necessarily result in improved growth status. 相似文献
83.
Carol J. Maslansky Gary M. Williams 《In vitro cellular & developmental biology. Plant》1982,18(8):683-693
Summary Hepatocyte primary cultures (HPC) derived from rat, mouse, hamster, and rabbit liver were characterized for a variety of parameters.
The conditions that maximized recovery, attachment, and survival varied between species. Hepatocytes from all four species
were capable of attaching in serum-free Williams’ medium E (WME), but optimal attachment as monolayer cultures was achieved
for mouse and hamster HPC in medium receiving 1% calf serum supplementation. Hamster hepatocytes required additional cations,
whereas rabbit and rat hepatocytes displayed maximal attachment in medium supplemented with 10% calf serum. Survival of mouse
and rabbit hepatocytes after 24 h in serum supplemented media was in the order of 90%. Rat and hamster hepatocyte 24 h survival
was approximately 70 and 60%, respectively, and was not significantly affected by serum supplementation. Hepatocytes from
each species varied in their content of cytochromeP450 at the time of isolation and in the rate of reduction during culture. Mouse and rat hepatocytes demonstrated the most
rapid decline in content during the initial 24 h in culture, whereas concentrations in rabbit hepatocytes were virtually unchanged.
The rate of decline inP450 concentrations in hamster hepatocytes was intermediate between those displayed by rat and rabbit hepatocytes. These studies
have delineated conditions useful for the culture of hepatocytes from four species and have documented the status of an important
parameter of their functional capability.
This study was supported by EPA contract 68-01-6179. C. J. Maslansky was a recipient of a Monsanto Fund Fellowship in Toxicology. 相似文献
84.
Charles A. Tyson Carol E. Green Susanna E. LeValley Robert J. Stephens 《In vitro cellular & developmental biology. Plant》1982,18(11):945-951
Summary Hepatocytes from livers of rats loaded by Fe-dextran treatment were isolated by an in situ collagenase perfusion technique
and evaluated for their biochemical, cytochemical, and morphological characteristics in cell culture. Iron loads 15 times
higher than in normal rat liver cells isolated in the same way were retained in the preparations with 40% present as hemosiderin.
A simple centrifugation-mathematical approach is described for the calculation of Fe content in the hepatocyte (95%) and reticuloendothelial
(5%) fractions in the isolates. The cells were cultured for 22 h without loss of protein synthesis capability or significant
changes in cell count, viability, endogenous glutamate-oxaloacetate transaminase (GOT) or Fe and were morphologically similar
in most respects to unloaded (normal) hepatocytes similarly cultured. Studies are in progress to assess the utility of these
preparations as a model for Fe mobilization from Fe-loaded animals.
This work is supported by National Institutes of Health Grants AM 25647-03 (M. Dawson, Principal Investigator) and GM 28158-01
(C. Tyson, Principal Investigator). The technical assistance of Mr. Jack E. Dabbs, Mr. Charles Hart, and Mr. Randy Douglas
is acknowledged. 相似文献
85.
86.
87.
88.
Jorma T. Ahokas Carol Davies Peter J. Ravenscroft 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1980,183(1):65-71
A new reversed-phase high-performance liquid chromatographic method allowing simultaneous measurement of plasma concentrations of disopyramide and quinidine is described. Disopyramide and quinidine were separated on a reversed-phase column using 0.05 M phosphate buffer (pH 3.0)—acetonitrile (73:27, v/v), as mobile phase and the peaks were monitored by UV absorbance at the wavelengths of 254 and 325 nm. The drugs were extracted from alkaline plasma with chloroform containing the internal standard. The organic phase was evaporated to dryness and the residue was redissolved in a small volume of the mobile phase before analysis by high-performance liquid chromatography. The method is convenient and reliable in routine monitoring of both drugs. 相似文献
89.
Jeanne Loring Bengt Glimelius Carol Erickson James A. Weston 《Developmental biology》1981,82(1):86-94
When early embryonic quail neural tubes are dissected free from surrounding tissues and placed in culture, small stellate neural crest cells usually migrate from the explant onto the substratum. This outgrowth has been reported to consist of a mixture of cells, some of which undergo melanogenesis, while the rest remain unpigmented. We have, in contrast to earlier observations, obtained a spatial separation of the two phenotypes. In these cultures the primary outgrowth of migrating cells remained almost free of pigment-forming cells, whereas small spherical clusters containing several hundred pigment-forming cells appeared on the explanted neural tubes. Whether the clusters remained with the tube explants or were subcultured, all cluster cells differentiated into melanocytes. Prior to melanogenesis, the appearance of the cultured cells from a cluster was indistinguishable from the cells in the outgrowth. The clusters provide a source of neural crest cells, that (1) can be easily obtained in comparatively large numbers, (2) is not contaminated with any other cell type, (3) can be isolated before the onset of differentiation, and (4) is developmentally homogeneous. Thus, the cluster population is well suited for many types of experiments, such as the identification of specific environmental factors that might control neural crest cell differentiation. 相似文献
90.
Aqueous samples containing labile substances are rapidly lyophilized after the frozen solutions are crushed in Nalgene plastic
bottles. Lyophilization time compares favorably with shell-frozen samples, and samples remain frozen at all times. 相似文献