全文获取类型
收费全文 | 1384篇 |
免费 | 135篇 |
出版年
2023年 | 10篇 |
2022年 | 20篇 |
2021年 | 37篇 |
2020年 | 14篇 |
2019年 | 17篇 |
2018年 | 30篇 |
2017年 | 14篇 |
2016年 | 30篇 |
2015年 | 60篇 |
2014年 | 69篇 |
2013年 | 77篇 |
2012年 | 97篇 |
2011年 | 69篇 |
2010年 | 51篇 |
2009年 | 47篇 |
2008年 | 51篇 |
2007年 | 78篇 |
2006年 | 50篇 |
2005年 | 54篇 |
2004年 | 43篇 |
2003年 | 58篇 |
2002年 | 41篇 |
2001年 | 21篇 |
2000年 | 33篇 |
1999年 | 23篇 |
1998年 | 19篇 |
1997年 | 18篇 |
1996年 | 12篇 |
1995年 | 11篇 |
1994年 | 10篇 |
1993年 | 9篇 |
1992年 | 16篇 |
1991年 | 15篇 |
1990年 | 17篇 |
1989年 | 13篇 |
1988年 | 18篇 |
1987年 | 19篇 |
1986年 | 15篇 |
1985年 | 14篇 |
1984年 | 19篇 |
1983年 | 22篇 |
1982年 | 16篇 |
1981年 | 9篇 |
1979年 | 20篇 |
1978年 | 9篇 |
1976年 | 9篇 |
1975年 | 10篇 |
1974年 | 7篇 |
1973年 | 11篇 |
1972年 | 14篇 |
排序方式: 共有1519条查询结果,搜索用时 203 毫秒
141.
142.
Insulin resistance has been documented in type 1 diabetes and may contribute to the high risk for cardiovascular disease in this population and progression of nephropathy. We investigated associations of renal parameters, including urinary albumin excretion rate (UAE), serum creatinine and creatinine clearance, with surrogate measure of insulin sensitivity calculated using a formula derived from euglycemic-hyperinsulinemic clamp studies (estimated glucose disposal rate, eGDR). Study included 353 patients with type 1 diabetes, none showed signs of adrenal, thyroid, renal, or cardiovascular diseases. Insulin sensitivity was measured with eGDR calculated with the equation: 24.31-(12.22xWHR)-(3.29xHT)-(0.57xHbA1c). The units were mgkg(-1)min(-1); WHR=waist to hip ratio; HT=hypertension. Correlations and logistic regression analysis were performed to identify relationships between renal parameters and eGDR, individual components of insulin resistance and risk of insulin resistance. UAE and serum creatinine significantly correlated with insulin resistance measured by eGDR (r=-0.13, and -0.17, all p<0.05), and its components disorders, WHR and HbA1c. After stratifying patients in quartiles of eGDR, those in the upper quartile of the eGDR had significantly reduced levels of UAE and serum creatinine, compared to subjects in lowest quartile. In a logistic regression analysis risk for development of insulin resistance in our subjects were independently predicted only by UAE (odds ratio = 1.01, p<0.01). Our results provide evidence of associations between insulin resistance and its components disorders with renal parameters, such as UAE and serum creatinine. Insulin resistance, measured with eGDR, predicts the increment in UAE in subjects with type 1 diabetes. Since progression to microalbuminuria is likely to occur in majority of diabetic patients, there is a need to further explore the role of risk factors such as insulin resistance. 相似文献
143.
Sundvall M Korhonen A Vaparanta K Anckar J Halkilahti K Salah Z Aqeilan RI Palvimo JJ Sistonen L Elenius K 《The Journal of biological chemistry》2012,287(27):23216-23226
144.
Lourens Poorter Alfredo Alarcón Geoffrey Blate Urbano Choque Todd S. Fredericksen Marco J. Justiniano Claudio Leaño Juan Carlos Licona William Pariona Francis E. Putz Lincoln Quevedo Marisol Toledo 《Biotropica》2012,44(3):276-283
Soil characteristics are important drivers of variation in wet tropical forest structure and diversity, but few studies have evaluated these relationships in drier forest types. Using tree and soil data from 48 and 32 1 ha plots, respectively, in a Bolivian moist and dry forest, we asked how soil conditions affect forest structure and diversity within each of the two forest types. After correcting for spatial effects, soil‐vegetation relationships differed between the dry and the moist forest, being strongest in the dry forest. Furthermore, we hypothesized that soil nutrients would play a more important role in the moist forest than in the dry forest because vegetation in the moist forest is less constrained by water availability and thus can show its full potential response to soil fertility. However, contrary to our expectations, we found that soil fertility explained a larger number of forest variables in the dry forest (50 percent) than in the moist forest (17 percent). Shannon diversity declined with soil fertility at both sites, probably because the most dominant, shade‐tolerant species strongly increased in abundance as soil fertility increased. 相似文献
145.
We assessed viability of 18 strains of filamentous ectomycorrhizal and saprotrophic basid-iomycetes and ascomycetes after cryopreservation with a novel technique based on charcoal filter paper strips (CFS). The results indicate that axenic fungal cultures grown on CFS recovered from freezing within a few days, even though none survived cryopreservation by the conventional straw method. Fungal growth on CFS was more vigorous, with morphological differentiations such as rhizomorphs and an increased amount of aerial mycelia compared to the unamended culture media. Accordingly CFS allows the cryopreservation of a wide range of rare and important ectomycorrhizal and saprotrophic fungi, which hitherto were difficult to revive from liquid nitrogen storage with the conventional and widely applied straw technique. 相似文献
146.
Slusky DA Metayer C Aldrich MC Ward MH Lea CS Selvin S Buffler PA 《Cancer epidemiology》2012,36(4):375-380
Introduction: Self-reported household pesticide use has been associated with higher risk of childhood leukemia in a number of case–control studies. The aim of this study is to assess the reliability of self-reported household use of pesticides and potential differences in reliability by case–control status, and by socio-demographic characteristics. Methods: Analyses are based on a subset of the Northern California Childhood Leukemia Study population. Eligible households included those with children less than 8 years old who lived in the same residence since diagnosis (reference date for controls). The reliability was based on two repeated in-person interviews. Kappa, percent positive and negative agreements were used to assess reliability of responses to ever/never use of six pesticides categories. Results: Kappa statistics ranged from 0.31 to 0.61 (fair to substantial agreement), with 9 out of the 12 tests indicating moderate agreement. The percent positive agreement ranged from 46 to 80% and the percent negative agreement from 54 to 95%. Reliability for all pesticide types as assessed by the three reliability measures did not differ significantly for cases and controls as confirmed by bootstrap analysis. For most pesticide types, Kappa and percent positive agreement were higher for non-Hispanics than Hispanics and for households with higher income vs. lower income. Conclusions: Reproducibility of maternal-reported pesticide use was moderate to high and was similar among cases and controls suggesting that differential recall is not likely to be a major source of bias. 相似文献
147.
148.
Chillakuri CR Sheppard D Lea SM Handford PA 《Seminars in cell & developmental biology》2012,23(4):421-428
The Notch receptor is part of a core signalling pathway which is highly conserved in all metazoan species. It is required for various cell fate decisions at multiple stages of development and in the adult organism, with dysregulation of the pathway associated with genetic and acquired diseases including cancer. Although cellular and in vivo studies have provided considerable insight into the downstream consequences of Notch signalling, relatively little is known about the molecular basis of the receptor/ligand interaction and initial stages of activation. Recent advances in structure determination of the extracellular regions of human Notch-1 and one of its ligands Jagged-1 have given new insights into docking events occurring at the cell surface which may facilitate the development of new highly specific therapies. We review the structural data available for receptor and ligands and identify the challenges ahead. 相似文献
149.
150.
Katharina A. Quadt Lea Barfod Daniel Andersen Jonas Bruun Ben Gyan Tue Hassenkam Michael F. Ofori Lars Hviid 《PloS one》2012,7(9)