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   66912篇
  免费   6585篇
  国内免费   1233篇
耳鼻咽喉   972篇
儿科学   2324篇
妇产科学   664篇
基础医学   4552篇
口腔科学   1600篇
临床医学   7598篇
内科学   8115篇
皮肤病学   531篇
神经病学   8684篇
特种医学   2314篇
外国民族医学   3篇
外科学   4022篇
综合类   7101篇
现状与发展   5篇
一般理论   2篇
预防医学   11442篇
眼科学   617篇
药学   5042篇
  34篇
中国医学   5942篇
肿瘤学   3166篇
  2024年   83篇
  2023年   1384篇
  2022年   1819篇
  2021年   2974篇
  2020年   3581篇
  2019年   3129篇
  2018年   3029篇
  2017年   2727篇
  2016年   2629篇
  2015年   2455篇
  2014年   5070篇
  2013年   5247篇
  2012年   3942篇
  2011年   4237篇
  2010年   3166篇
  2009年   3044篇
  2008年   3272篇
  2007年   3290篇
  2006年   2920篇
  2005年   2376篇
  2004年   1904篇
  2003年   1811篇
  2002年   1386篇
  2001年   1257篇
  2000年   1051篇
  1999年   880篇
  1998年   648篇
  1997年   691篇
  1996年   474篇
  1995年   554篇
  1994年   483篇
  1993年   402篇
  1992年   423篇
  1991年   342篇
  1990年   275篇
  1989年   258篇
  1988年   230篇
  1987年   187篇
  1986年   160篇
  1985年   159篇
  1984年   150篇
  1983年   95篇
  1982年   103篇
  1981年   92篇
  1980年   78篇
  1979年   54篇
  1978年   50篇
  1977年   41篇
  1976年   37篇
  1975年   31篇
排序方式: 共有10000条查询结果,搜索用时 681 毫秒
1.
2.
Oxidative stress and inflammation are two possible mechanisms related to nephrotoxicity caused by environmental pollutants. Ellagic acid, a powerful antioxidant phytochemical, may have great relevance in mitigating pollutant-induced nephrotoxicity and preventing the progression of kidney disease. This review discusses the latest findings on the protective effects of ellagic acid, its metabolic derivatives, the urolithins, against kidney toxicity caused by heavy metals, pesticides, mycotoxins, and organic air pollutants. We describe the chelating, antioxidant, anti-inflammatory, antifibrotic, antiautophagic, and antiapoptotic properties of ellagic acid to attenuate nephrotoxicity. Furthermore, we present the molecular targets and signaling pathways that are regulated by these antioxidants, and suggest some others that should be explored. Nevertheless, the number of reports is still limited to establish the efficacy of ellagic acid against kidney damage induced by environmental pollutants. Therefore, additional preclinical studies on this topic are required, as well as the development of well-designed clinical trials.  相似文献   
3.
Demographic situation, changes in the role of women in society and growing demand for long-term care (LTC) of older people have challenged the ability to meet the growing LTC needs in most developed countries. In countries where responsibility for LTC is still largely laid on families, it is, however, even more critical and calls for improvements in formal LTC systems. More intensive stakeholder collaboration in LTC policy development, organising and delivery are of primary importance in improving LTC systems. Such collaboration, however, is not always successful; thus, it is critical to understand what makes it effective and efficient. In this paper, we specifically look into multistakeholder collaboration in LTC in Lithuania, one of the fastest ageing countries in the EU, with the demand for LTC services growing fast and exceeding the supply despite rising business and NGO engagement. To determine facilitators of such collaboration, we build on the data obtained through eight focus group discussions with all key stakeholder representatives (LTC policymakers, organisers and service providers [public, private and NGOs], 54 participants in total). Our findings indicate that in addition to national and organisational level facilitators studied in prior research, there are important individual level factors, such as meaningfulness at work, concern and care for others, possibility for personal growth and development, satisfaction with supervision, a sense of belonging and role clarity. On the other hand, our results show that collaboration is constrained by a shortage of human resources, increased workload caused by growing LTC demand, bureaucratic requirements, legal restrictions, lack of awareness of LTC service availability among elder persons, and prevailing social norms and attitudes to institutionalised care. Interestingly, a lack of financial resources is not perceived as a major constraint.  相似文献   
4.
5.
This study is focussed on micro-encapsulation of essential oils in polylactic acid (PLA) and a poly(methyl methacrylate) (PMMA) matrix as well as blends of the same. Microspheres were prepared by the solvent evaporation technique and characterised by scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and Fourier transform infra-red spectroscopy (FTIR). The encapsulation efficiencies and release profiles of the essential oils were studied by gas chromatography mass spectrometry (GC-MS) and head-space solid-phase microextraction GC-MS, respectively. Furthermore, the microspheres were tested for antibacterial activity against both Gram-negative and Gram-positive bacterial strains.

The results showed that the microspheres compositions (PLA/PMMA ratio) have significant effect on their characteristics. The process adopted for preparing the microspheres promoted formation of spherical particles at the sizes of 1.5–9.5?µm. The highest encapsulation efficiency of the prepared microspheres was observed in systems consisting of linalool (81.10?±?10.0?wt. % for PLA system and 76.0?±?3.3?wt. % for PMMA system). Confirmation was also made that the release rate of the microspheres was affected by the size of the same.  相似文献   

6.
7.
Coronary embolism (CE) is an uncommon and unique cause of acute myocardial infarction. In this report, we review 216 cases of CE including 2 new cases from our institution. The mean patient age was 52.5 years and 62% of the patients were males. Chest pain was the most common presenting symptom followed by dyspnea, and the most commonly affected vessel was the left anterior descending artery. Leading etiologies of the embolus were atrial fibrillation, septic emboli, and iatrogenic causes. Treatment approaches varied with thrombus aspiration being used in 30% of cases. In-hospital mortality rate was 36% and 13% of the cases were complicated by cerebrovascular accident. CE is a unique pathology that leads to acute myocardial infarction. It portends a high mortality rate and requires a high level of suspicion as symptoms may be misleading. Further research is needed in order to improve recognition and management and to lower associated mortality.  相似文献   
8.
9.
Benzo[a]pyrene (BaP) is a polycyclic aromatic hydrocarbon (PAH) in particulate matter that has a diameter of ≤2.5 μm (PM2.5). Studies have demonstrated that BaP exposure causes oocyte meiotic arrest in mice. However, whether BaP exposure also affects oocyte maturation in offspring remains unclear. To test this, female mice were administered BaP before pregnancy to generate BaP-exposed offspring. Our findings showed that BaP exposure reduced the in vitro maturation and increased the abnormalities of meiotic apparatus in offspring oocytes. In addition, BaP exposure reduced the mitochondrial content and intracellular ATP generation, induced early apoptosis, increased reactive oxidative species accumulation and the genomic DNA 5-methylcytosine (5mc) level in offspring oocytes. Along with the abovementioned defective parameters, maternal BaP exposure further compromised the embryo developmental competence of offspring oocytes. In summary, our study demonstrated that maternal BaP exposure compromised offspring oocyte maturation and quality.  相似文献   
10.

Background

It has been reported that particulate matter (PM) is associated with cardiovascular diseases (CVD) while metabolic syndrome is also an important risk factor for CVD. However, few studies have investigated the epidemiological association between PM and metabolic syndrome.

Objective

To investigate the association between one-year exposure to PM with an aerodynamic diameter <2.5?μm (PM2.5) and the risk of metabolic syndrome in Korean adults without CVD.

Methods

Exposure to PM2.5 was assessed using a Community Multiscale Air Quality (CMAQ) model. Metabolic syndrome was defined by National Cholesterol Education Program Adult Treatment Panel III. Andersen and Gill model with time-varying covariates, considering recurrent events, was used to investigate the association between one-year average PM2.5 and the risk of incident metabolic syndrome in 119,998 adults from the national health screening cohort provided by Korea National Health Insurance from 2009 to 2013.

Results

Higher risk of metabolic syndrome, waist-based obesity, hypertension, hypertriglyceridemia, low HDL cholesterol, and hyperglycemia were significantly associated with a 10-μg/m3 increase in PM2.5 [adjusted hazard ratio (HR): 1.070, 1.510, 1.499, 1.468, 1.627 and 1.380, respectively]. In addition, the risk of metabolic syndrome associated with PM2.5 exposure was significant in the consistently obese group (obese at baseline and endpoint).

Conclusion

Exposure to one-year average PM2.5 is associated with an increased risk of metabolic syndrome and its components in adults without CVD. These associations are particularly prominent in the consistently obese group (obese at baseline and endpoint). Our findings indicate that PM2.5 affects the onset of MS and its components which may lead to increase the risk of CVD.  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