首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1354篇
  免费   109篇
  国内免费   2篇
耳鼻咽喉   4篇
儿科学   62篇
妇产科学   31篇
基础医学   196篇
口腔科学   44篇
临床医学   100篇
内科学   273篇
皮肤病学   22篇
神经病学   57篇
特种医学   25篇
外科学   197篇
综合类   30篇
预防医学   89篇
眼科学   52篇
药学   179篇
中国医学   7篇
肿瘤学   97篇
  2023年   14篇
  2022年   16篇
  2021年   36篇
  2020年   27篇
  2019年   41篇
  2018年   46篇
  2017年   26篇
  2016年   48篇
  2015年   51篇
  2014年   64篇
  2013年   52篇
  2012年   121篇
  2011年   101篇
  2010年   59篇
  2009年   56篇
  2008年   67篇
  2007年   61篇
  2006年   94篇
  2005年   69篇
  2004年   66篇
  2003年   45篇
  2002年   51篇
  2001年   28篇
  2000年   28篇
  1999年   21篇
  1998年   13篇
  1996年   7篇
  1995年   7篇
  1994年   5篇
  1993年   5篇
  1992年   14篇
  1991年   8篇
  1990年   7篇
  1989年   11篇
  1988年   7篇
  1987年   13篇
  1986年   6篇
  1985年   5篇
  1983年   7篇
  1982年   3篇
  1981年   12篇
  1980年   5篇
  1979年   3篇
  1978年   7篇
  1977年   4篇
  1976年   4篇
  1975年   4篇
  1970年   2篇
  1966年   2篇
  1965年   2篇
排序方式: 共有1465条查询结果,搜索用时 15 毫秒
21.
Acute aortic syndrome is a group of life-threatening diseases of the thoracic aorta that usually present to the emergency department. It includes aortic dissection, aortic intramural hematoma, and penetrating aortic ulcer. Rare aortic pathologies of aorto-esophageal fistula and mycotic aneurysm may also be included in this list. All these conditions require urgent treatment with complex clinical care and management. Most patients who present with chest pain are evaluated with a chest radiograph in the emergency department. It is important that maximum diagnostic information is extracted from the chest radiograph as certain signs on the chest radiograph are extremely useful in pointing towards the diagnosis of acute aortic syndrome.  相似文献   
22.
Agriculture is a major contributor to air pollution, the largest environmental risk factor for mortality in the United States and worldwide. It is largely unknown, however, how individual foods or entire diets affect human health via poor air quality. We show how food production negatively impacts human health by increasing atmospheric fine particulate matter (PM2.5), and we identify ways to reduce these negative impacts of agriculture. We quantify the air quality–related health damages attributable to 95 agricultural commodities and 67 final food products, which encompass >99% of agricultural production in the United States. Agricultural production in the United States results in 17,900 annual air quality–related deaths, 15,900 of which are from food production. Of those, 80% are attributable to animal-based foods, both directly from animal production and indirectly from growing animal feed. On-farm interventions can reduce PM2.5-related mortality by 50%, including improved livestock waste management and fertilizer application practices that reduce emissions of ammonia, a secondary PM2.5 precursor, and improved crop and animal production practices that reduce primary PM2.5 emissions from tillage, field burning, livestock dust, and machinery. Dietary shifts toward more plant-based foods that maintain protein intake and other nutritional needs could reduce agricultural air quality–related mortality by 68 to 83%. In sum, improved livestock and fertilization practices, and dietary shifts could greatly decrease the health impacts of agriculture caused by its contribution to reduced air quality.

The health and environmental consequences of feeding the increasingly large and affluent global population are becoming increasingly apparent. These consequences have spurred interest in identifying food production practices and diets that improve human health and reduce environmental harm. Recent work has demonstrated that many of the opportunities for food producers and consumers to improve nutritional outcomes also have environmental benefits, such as reducing greenhouse gas emissions, land and water use, and eutrophication (16). It is largely unknown, however, how individual foods and diets affect air quality, even though air pollution is the largest environmental mortality risk factor in the United States and globally (7, 8), and agriculture is itself known to be a major contributor to reduced air quality (8, 9). In the United States alone, atmospheric fine particulate matter (PM2.5) from anthropogenic sources is responsible for about 100,000 premature deaths each year, one-fifth of which are linked to agriculture (10, 11).Here, we show how different foods affect human health by reducing air quality. We consider the emission of pollutants that contribute to atmospheric PM2.5, the chronic exposure to which increases the incidence of premature mortality from cardiovascular disease, cancer, and stroke (12, 13). These pollutants include directly emitted PM2.5 (primary PM2.5) and PM2.5 formed in the atmosphere (secondary PM2.5) from the precursors ammonia (NH3), nitrogen oxides (NOx), sulfur dioxide (SO2), and nonmethane volatile organic compounds (NMVOCs). From a spatially explicit inventory of emissions of primary PM2.5 and secondary PM2.5 precursors from agricultural supply chain activities for commodities in the contiguous United States (SI Appendix, Figs. S1 and S2) (14, 15) (Materials and Methods), we estimate increases in atmospheric concentrations of total (primary + secondary) PM2.5 attributable to agricultural emissions; total PM2.5 transport, chemistry, and removal; and exposure of populations to total PM2.5 using an ensemble of three independent air quality models (1619). We describe damages attributable to 95 agricultural commodities and 67 final food products (full list in SI Appendix, Table S1), which cover >99% of US agricultural production (20).  相似文献   
23.
Effect of alcohol on viral hepatitis and other forms of liver dysfunction   总被引:1,自引:0,他引:1  
Alcohol is a known hepatotoxic agent, which may exacerbate liver injury caused by other agents. The wide prevalence of alcohol use and abuse in society makes it an important cofactor in many other liver diseases. Examples of liver diseases that are significantly influenced by ingestion of alcohol include chronic viral hepatitis, disorders of iron overload, and obesity-related liver disease.  相似文献   
24.
Left ventricular assist devices(LVAD) are increasingly become common as life prolonging therapy in patients with advanced heart failure. Current devices are now used as definitive treatment in some patients given the improved durability of continuous flow pumps. Unfortunately, continuous flow LVADs are fraught with complications such as gastrointestinal(GI) bleeding that are primarily attributed to the formation of arteriovenous malformations. With frequent GI bleeding, antiplatelet and anticoagulation therapies are usually discontinued increasing the risk of life-threatening events. Small bowel bleeds account for 15%as the source and patients often undergo multiple endoscopic procedures.Treatment strategies include resuscitative measures and endoscopic therapies.Medical treatment is with octreotide. Novel treatment options include thalidomide, angiotensin converting enzyme inhibitors/angiotensin Ⅱ receptor blockers, estrogen-based hormonal therapies, doxycycline, desmopressin and bevacizumab. Current research has explored the mechanism of frequent GI bleeds in this population, including destruction of von Willebrand factor,upregulation of tissue factor, vascular endothelial growth factor, tumor necrosis factor-α, tumor growth factor-β, and angiopoetin-2, and downregulation of angiopoetin-1. In addition, healthcare resource utilization is only increasing in this patient population with higher admissions, readmissions, blood product utilization, and endoscopy. While some of the novel endoscopic and medical therapies for LVAD bleeds are still in their development stages, these tools will yet be crucial as the number of LVAD placements will likely only increase in the coming years.  相似文献   
25.
26.
The Digital Imaging and Communications in Medicine (DICOM) standard is the universal format for interoperability in medical imaging. In addition to imaging data, DICOM has evolved to support a wide range of imaging metadata including contrast administration data that is readily available from many modern contrast injectors. Contrast agent, route of administration, start and stop time, volume, flow rate, and duration can be recorded using DICOM attributes [1]. While this information is sparsely and inconsistently recorded in routine clinical practice, it could potentially be of significant diagnostic value. This work will describe parameters recorded by automatic contrast injectors, summarize the DICOM mechanisms available for tracking contrast injection data, and discuss the role of such data in clinical radiology.  相似文献   
27.
It was postulated that thalidomide causes birth defects by being metabolized to a toxic electrophilic intermediate. This hypothesis was tested by using an in vitro assay in which drug toxicity to human lymphocytes was assessed in the presence of a hepatic microsomal drug metabolizing system. Maternal hepatic microsomes from pregnant rabbits mediated the production of a metabolite that was toxic to lymphocytes. Toxicity was enhanced by inhibitors of epoxide hydrolase (EC 3.3.2.3) and abolished by adding the purified enzyme to the incubation medium. The metabolite thus appears to be in arene oxide, consistent with the previously reported isolation of phenolic metabolites of thalidomide from the urine of treated animals. Two teratogenic analogs of thalidomide (phthalimidophthalimide and phthalimidinoglutarimide) were also toxic in the system; two nonteratogenic analogs (phthalimide and hexahydrothalidomide) were not toxic, even in the presence of epoxide hydrolase inhibitors. The toxic metabolite of thalidomide was not produced by rat liver microsomes (the rat is not sensitive to thalidomide teratogenesis) but was produced by hepatic preparations from maternal rabbits, and rabbit, monkey, and human (all sensitive species) fetuses. A toxic arene oxide therefore may be involved in the teratogenicity of thalidomide.  相似文献   
28.
Before installing Photovoltaic (PV) panels at a place it is important to estimate the solar potential of the place. Most approaches available in literature do not consider the presence of surrounding obstructions, thus leading to wrong estimates. Light Detection and Ranging (LiDAR) data or 3D (Geographic Information System) GIS based approaches consider obstructions but prove cost-effective only at city-wide scales. This paper presents a cost-effective, accurate, and scalable approach for this purpose. The proposed approach utilizes terrestrial images of surroundings and identifies obstructions present therein. Using the azimuth and elevation angles of the principal axes of the terrestrial images the azimuth and elevation angles of each pixel in these images are determined. Using thresholding and morphological closing the terrestrial images are segmented into sky and non-sky zones. Sun is considered visible at the point of interest if it lies in the sky zone. The position of the Sun is determined using the solar position algorithm and the irradiance reaching the Earth surface is computed using the modified radiative transfer model. Finally, the total irradiance over a chosen time period at a given location is estimated by integrating the irradiances for the duration when the Sun is visible.  相似文献   
29.

Background:

Maps show well the spatial configuration of information. Considerable effort is devoted to the development of geographical information systems (GIS) that increase understanding of public health problems and in particular to collaborate efforts among clinicians, epidemiologists, ecologists, and geographers to map and forecast disease risk.

Objectives:

Small populations tend to give rise to the most extreme disease rates, even if the actual rates are similar across the areas. Such situations will follow the decision-maker''s attention on these areas when they scrutinize the map for decision making or resource allocation. As an alternative, maps can be prepared using P-values (probabilistic values).

Materials and Methods:

The statistical significance of rates rather than the rates themselves are used to map the results. The incidence rates calculated for each village from 2000 to 2009 is used to estimate λ, the expected number of cases in the study area. The obtained results are mapped using Arc GIS 10.0.

Results:

The likelihood of infections from low to high is depicted in the map and it is observed that five villages namely, Odanthurai, Coimbatore Corporation, Ikkaraiboluvampatti, Puliakulam, and Pollachi Corporation are more likely to have significantly high incidences.

Conclusion:

In the probability map, some of the areas with exceptionally high or low rates disappear. These are typically small unpopulated areas, whose rates are unstable due to the small numbers problem. The probability map shows more specific regions of relative risks and expected outcomes.  相似文献   
30.

Purpose

To determine differences in health-related quality of life (HRQoL), survival and healthcare resource use of critically ill adults with and without sepsis.

Methods

We conducted a primary propensity score matched analysis of patients with and without sepsis enrolled in a large multicentre clinical trial. Outcomes included HRQoL at 6 months, survival to 2 years, length of ICU and hospital admission and cost of ICU and hospital treatment to 2 years.

Results

We obtained linked data for 3442 (97.3%) of 3537 eligible patients and matched 806/905 (89.0%) patients with sepsis with 806/2537 (31.7%) without. After matching, there were no significant differences in the proportion of survivors with and without sepsis reporting problems with mobility (37.8% vs. 38.7%, p?=?0.86), self-care (24.7% vs. 26.0%, p?=?0.44), usual activities (44.5% vs. 46.8%, p?=?0.28), pain/discomfort (42.4% vs. 41.6%, p?=?0.54) and anxiety/depression (36.9% vs. 37.7%, p?=?0.68). There was no significant difference in survival at 2 years: 482/792 (60.9%) vs. 485/799 (60.7%) (HR 1.01, 95% CI 0.86–1.18, p?=?0.94). The initial ICU and hospital admission were longer for patients with sepsis: 10.1?±?11.9 vs. 8.0?±?9.8 days (p?<?0.0001) and 22.8?±?21.2 vs. 19.1?±?19.0 days, (p?=?0.0003) respectively. The cost of ICU admissions was higher for patients with sepsis: A$43,345?±?46,263 (€35,109?±?35,043) versus 34,844?±?38,281 (€28,223?±?31,007), mean difference $8501 (€6885), 95% CI $4342–12,660 (€3517?±?10,254), p?<?0.001 as was the total cost of hospital treatment to 2 years: A$74,120?±?60,750 (€60,037?±?49,207) versus A$65,806?±?59,856 (€53,302?±?48,483), p?=?0.005.

Conclusions

Critically ill patients with sepsis have higher healthcare resource use and costs but similar survival and HRQoL compared to matched patients without sepsis.
  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号