全文获取类型
收费全文 | 2427613篇 |
免费 | 198437篇 |
国内免费 | 4388篇 |
专业分类
耳鼻咽喉 | 34915篇 |
儿科学 | 74162篇 |
妇产科学 | 63719篇 |
基础医学 | 341743篇 |
口腔科学 | 68192篇 |
临床医学 | 221319篇 |
内科学 | 479244篇 |
皮肤病学 | 48539篇 |
神经病学 | 205826篇 |
特种医学 | 97935篇 |
外国民族医学 | 886篇 |
外科学 | 368854篇 |
综合类 | 56843篇 |
现状与发展 | 1篇 |
一般理论 | 1052篇 |
预防医学 | 195010篇 |
眼科学 | 56835篇 |
药学 | 181022篇 |
4篇 | |
中国医学 | 4439篇 |
肿瘤学 | 129898篇 |
出版年
2018年 | 25900篇 |
2017年 | 19982篇 |
2016年 | 21853篇 |
2015年 | 24716篇 |
2014年 | 35591篇 |
2013年 | 53528篇 |
2012年 | 72914篇 |
2011年 | 76726篇 |
2010年 | 44921篇 |
2009年 | 43047篇 |
2008年 | 72278篇 |
2007年 | 76759篇 |
2006年 | 77405篇 |
2005年 | 75377篇 |
2004年 | 72411篇 |
2003年 | 69835篇 |
2002年 | 68757篇 |
2001年 | 112850篇 |
2000年 | 116787篇 |
1999年 | 98719篇 |
1998年 | 28402篇 |
1997年 | 25917篇 |
1996年 | 25756篇 |
1995年 | 24904篇 |
1994年 | 23438篇 |
1993年 | 21823篇 |
1992年 | 79562篇 |
1991年 | 76533篇 |
1990年 | 73701篇 |
1989年 | 70952篇 |
1988年 | 65960篇 |
1987年 | 64893篇 |
1986年 | 61422篇 |
1985年 | 58509篇 |
1984年 | 44354篇 |
1983年 | 37757篇 |
1982年 | 23060篇 |
1981年 | 20514篇 |
1980年 | 19160篇 |
1979年 | 41370篇 |
1978年 | 29080篇 |
1977年 | 24424篇 |
1976年 | 22879篇 |
1975年 | 24006篇 |
1974年 | 29677篇 |
1973年 | 28077篇 |
1972年 | 26257篇 |
1971年 | 24180篇 |
1970年 | 22773篇 |
1969年 | 21102篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
O. Ieromina C. J. M. Musters P. M. Bodegom W. J. G. M. Peijnenburg M. G. Vijver 《Ecotoxicology (London, England)》2016,25(6):1170-1180
Analyzing functional species’ characteristics (species traits) that represent physiological, life history and morphological characteristics of species help understanding the impacts of various stressors on aquatic communities at field conditions. This research aimed to study the combined effects of pesticides and other environmental factors (temperature, dissolved oxygen, dissolved organic carbon, floating macrophytes cover, phosphate, nitrite, and nitrate) on the trait modality distribution of aquatic macrofauna communities. To this purpose, a field inventory was performed in a flower bulb growing area of the Netherlands with significant variation in pesticides pressures. Macrofauna community composition, water chemistry parameters and pesticide concentrations in ditches next to flower bulb fields were determined. Trait modalities of nine traits (feeding mode, respiration mode, locomotion type, resistance form, reproduction mode, life stage, voltinism, saprobity, maximum body size) likely to indicate pesticides impacts were analyzed. According to a redundancy analysis, phosphate -and not pesticides- constituted the main factor structuring the trait modality distribution of aquatic macrofauna. The functional composition could be ascribed for 2–4 % to pesticides, and for 3–11 % to phosphate. The lack of trait responses to pesticides may indicate that species may have used alternative strategies to adapt to ambient pesticides stress. Biomass of animals exhibiting trait modalities related to feeding by predation and grazing, presence of diapause form or dormancy, reproduction by free clutches and ovoviviparity, life stage of larvae and pupa, was negatively correlated to the concentration of phosphate. Hence, despite the high pesticide pollution in the area, variation in nutrient-related stressors seems to be the dominant driver of the functional composition of aquatic macrofauna assembly in agricultural ditches. 相似文献
22.
23.
24.
Nidogen 1 (NID1) is a glycoprotein found in basement membranes involved in cross-linking collagen IV and laminin. The role of NID in breast cancer has only been evaluated in a small number of studies and the findings of these studies have been inconsistent. Our previous work revealed that highly tumorigenic murine mammary tumor cells express high levels of Nid1 while weakly tumorigenic mammary tumor cells express low levels of Nid1. To investigate Nid1, two stable knockdown lines were created, and Nid1 knockdown was confirmed at both the mRNA and protein level. Nid1 knockdown significantly reduced cell proliferation and migration/invasion and these reductions in proliferation and migration/invasion could be rescued by conditioned media containing NID1 protein. The reduced migration/invasion observed in the Nid1 knockdown cells was not associated with significant alterations in the epithelial gene Cdh1 or the mesenchymal genes Snai1, Snai2, Twist1, Twist2, Zeb1 and Zeb2. Therefore, suppression of Nid1 expression reduces proliferation and migration/invasion in claudin-low murine mammary tumor cells. 相似文献
25.
26.
27.
28.
Susan E. Hickman Alexia M. Torke Greg A. Sachs Rebecca L. Sudore Anne L. Myers Qing Tang Giorgos Bakoyannis Bernard J. Hammes 《Journal of pain and symptom management》2019,57(6):1143-1150.e5
ContextIt is especially important that patients are well informed when making high-stakes, preference-sensitive decisions like those on the Physician Orders for Life-Sustaining Treatment (POLST) form. However, there is currently no way to easily evaluate whether patients understand key concepts when making these important decisions.ObjectivesTo develop a POLST knowledge survey.MethodsExpert (n = 62) ratings of key POLST facts were used to select items for a POLST knowledge survey. The survey was administered to nursing facility residents (n = 97) and surrogate decision-makers (n = 112). A subset (n = 135) were re-administered the survey after a standardized advance care planning discussion to assess the scale's responsiveness to change.ResultsThe 19-item survey demonstrated adequate reliability (α = 0.72.). Residents' scores (x = 11.4, standard deviation 3.3) were significantly lower than surrogate scores (x = 14.7, standard deviation 2.5) (P < 0.001). Scores for both groups increased significantly after administration of a standardized advance care planning discussion (P < 0.001). Although being a surrogate, age, race, education, cognitive functioning, and health literacy were significantly associated with higher POLST Knowledge Survey scores in univariate analyses, only being a surrogate (P < 0.001) and being white (P = 0.028) remained significantly associated with higher scores in multivariate analyses.ConclusionThe 19-item POLST Knowledge Survey demonstrated adequate reliability and responsiveness to change. Findings suggest the survey could be used to identify knowledge deficits and provide targeted education to ensure adequate understanding of key clinical decisions when completing POLST. 相似文献
29.
30.