全文获取类型
收费全文 | 50291篇 |
免费 | 5081篇 |
国内免费 | 15篇 |
出版年
2021年 | 752篇 |
2020年 | 556篇 |
2019年 | 676篇 |
2018年 | 846篇 |
2017年 | 755篇 |
2016年 | 1214篇 |
2015年 | 2032篇 |
2014年 | 2246篇 |
2013年 | 2807篇 |
2012年 | 3522篇 |
2011年 | 3500篇 |
2010年 | 2301篇 |
2009年 | 2019篇 |
2008年 | 2807篇 |
2007年 | 2817篇 |
2006年 | 2710篇 |
2005年 | 2483篇 |
2004年 | 2459篇 |
2003年 | 2217篇 |
2002年 | 2195篇 |
2001年 | 793篇 |
2000年 | 715篇 |
1999年 | 781篇 |
1998年 | 594篇 |
1997年 | 474篇 |
1996年 | 406篇 |
1995年 | 458篇 |
1994年 | 430篇 |
1993年 | 440篇 |
1992年 | 525篇 |
1991年 | 458篇 |
1990年 | 441篇 |
1989年 | 474篇 |
1988年 | 454篇 |
1987年 | 427篇 |
1986年 | 348篇 |
1985年 | 410篇 |
1984年 | 415篇 |
1983年 | 387篇 |
1982年 | 387篇 |
1981年 | 343篇 |
1980年 | 330篇 |
1979年 | 301篇 |
1978年 | 241篇 |
1977年 | 247篇 |
1976年 | 252篇 |
1975年 | 264篇 |
1974年 | 236篇 |
1973年 | 213篇 |
1972年 | 188篇 |
排序方式: 共有10000条查询结果,搜索用时 828 毫秒
91.
In the South-west Thames Region 2619 patients (2105 women and 514 men) were discharged with a diagnosis of femoral neck fracture in 1974. The equivalent of a 250-bedded hospital was occupied throughout the year. The incidence, average length of stay, and mortality rate rose with increasing age and there were differences in these indices in the five health areas. These results confirm the enormous burden placed on the hospital service by patients with fracture of the femoral neck but suggest that differences in practice in the five areas may contribute to the size of the problem. 相似文献
92.
93.
The isolation of mutants of Saccharomyces cerevisiae that divide at approximately half the size of the wild type is described. Three mutants have been isolated in which the small size at bud initiation is due to a mutation in a single nuclear gene. 相似文献
94.
95.
Abstract. Small-scale species frequency and cumulative species frequency were studied in four plots in limestone grassland of the Veronica spicata-Avenula pratensis association on Stora Alvaret on the Baltic island of Öland, Sweden. Species mobility was expressed as increase in cumulative species frequency in 20 subplots of 100 cm2. Observed cumulative frequencies from 1985–1989 in all four plots, and from 1985–1995 in one plot were compared with values following from two null models, a ‘minimal mobility’ model and a random mobility model. In ca. 50 % of the cases the observed cumulative frequency was not significantly different from the random expectation. However, in many such cases the mean annual frequency was either very high or very low. Three ways of calculating the mobility rate are presented though only one is used: (observed cumulative frequency -lowest annual frequency) / expected cumulative frequency. Values × 100 range from 0 to 100. There were slight differences between the four plots which were interpreted in terms of differences in grazing intensity and soil depth. It is stressed that the idea of the Carousel model has never been meant to suggest that all species would show random mobility, which we now quantify, but that species differ in their mobility rate and that the mean rate is much higher than generally realized. 相似文献
96.
Gillian D Alton David L Pearl Ken G Bateman W Bruce McNab Olaf Berke 《BMC veterinary research》2010,6(1):42
Background
Ontario provincial abattoirs have the potential to be important sources of syndromic surveillance data for emerging diseases of concern to animal health, public health and food safety. The objectives of this study were to: (1) describe provincially inspected abattoirs processing cattle in Ontario in terms of the number of abattoirs, the number of weeks abattoirs process cattle, geographical distribution, types of whole carcass condemnations reported, and the distance animals are shipped for slaughter; and (2) identify various seasonal, secular, disease and non-disease factors that might bias the results of quantitative methods, such as cluster detection methods, used for food animal syndromic surveillance. 相似文献97.
98.
zge Karayel Francesca Tonelli Sebastian Virreira Winter Phillip E. Geyer Ying Fan Esther M. Sammler Dario R. Alessi Martin Steger Matthias Mann 《Molecular & cellular proteomics : MCP》2020,19(9):1546-1560
Highlights
- •MS-based clinical assay that accurately determines phospho Rab10 occupancy.
- •Stable isotope labeled phosphopeptide injected as a standard with endogenous tryptic phospho Rab peptide for accurate ratio determination.
- •Determination of pRab levels in neutrophils of Parkinson disease patients.
- •Relevance of pRab levels as marker of PD.
99.
100.
The low-molecular-mass form of two distinct catechol O-methyltransferase activities (S-adenosyl-L-methionine: catechol O-methyltransferase, COMT, EC 2.1.1.6) has been purified to homogeneity from rat liver using 40-70% ammonium sulfate precipitation, gel filtration on Sephadex G-100, adsorption on hydroxyapatite C and ion-exchange chromatography on DEAE-Sepharose CL-6B. The relative molecular mass Mr, determined by sodium dodecyl sulfate/polyacrylamide gel electrophoresis is 22 400 +/- 500. Irradiation of the enzyme in the presence of 8-azido-[methyl-3H]AdoMet results in the specific labeling of the catalytic site of the enzyme. Photolabeling was successful with crude COMT preparations and with the isolated enzyme. Immunocytochemical studies present new information about the localization of the low-molecular-mass form in the liver parenchyma. Subcellularly COMT immunoreactivity could be attributed exclusively to the compartment with glycogen granules. Nucleus, mitochondria and endoplasmic reticulum showed no immunostaining. 相似文献