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   4822篇
  免费   421篇
  国内免费   20篇
耳鼻咽喉   44篇
儿科学   169篇
妇产科学   117篇
基础医学   525篇
口腔科学   218篇
临床医学   474篇
内科学   1078篇
皮肤病学   60篇
神经病学   229篇
特种医学   81篇
外科学   496篇
综合类   112篇
一般理论   2篇
预防医学   570篇
眼科学   192篇
药学   550篇
中国医学   59篇
肿瘤学   287篇
  2024年   6篇
  2023年   87篇
  2022年   106篇
  2021年   409篇
  2020年   223篇
  2019年   258篇
  2018年   282篇
  2017年   188篇
  2016年   206篇
  2015年   170篇
  2014年   238篇
  2013年   328篇
  2012年   389篇
  2011年   389篇
  2010年   208篇
  2009年   139篇
  2008年   216篇
  2007年   184篇
  2006年   167篇
  2005年   176篇
  2004年   142篇
  2003年   116篇
  2002年   114篇
  2001年   36篇
  2000年   45篇
  1999年   47篇
  1998年   37篇
  1997年   52篇
  1996年   26篇
  1995年   19篇
  1994年   17篇
  1993年   24篇
  1992年   20篇
  1991年   26篇
  1990年   22篇
  1989年   16篇
  1988年   27篇
  1987年   15篇
  1986年   14篇
  1985年   6篇
  1984年   9篇
  1982年   4篇
  1981年   4篇
  1980年   9篇
  1979年   8篇
  1978年   8篇
  1976年   6篇
  1975年   3篇
  1970年   2篇
  1967年   2篇
排序方式: 共有5263条查询结果,搜索用时 187 毫秒
1.
Coronavirus disease-19 (COVID-19) caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is now a pandemic threat. This virus is supposed to be spread by human to human transmission. Cellular angiotensin-converting enzyme 2 (ACE2) is the receptor of SARS-CoV-2 which is identical or similar in different species of animals such as pigs, ferrets, cats, orangutans, monkeys, and humans. Moreover, a recent study predicted that dogs might be secondary hosts during the evolution of SARS-CoV-2 from bat to human. Therefore, there is a possibility of spreading SARS-CoV-2 through domestic pets. There are now many reports of SARS-CoV-2 positive cases in dogs, cats, tigers, lion, and minks. Experimental data showed ferrets and cats are highly susceptible to SARS-CoV-2 as infected by virus inoculation and can transmit the virus directly or indirectly by droplets or airborne routes. Based on these natural infection reports and experimental data, whether the pets are responsible for SARS-CoV-2 spread to humans; needs to be deeply investigated. Humans showing clinical symptoms of respiratory infections have been undergoing for the COVID-19 diagnostic test but many infected people and few pets confirmed with SARS-CoV-2 remained asymptomatic. In this review, we summarize the natural cases of SARS-CoV-2 in animals with the latest researches conducted in this field. This review will be helpful to think insights of SARS-CoV-2 transmissions, spread, and demand for seroprevalence studies, especially in companion animals.  相似文献   
2.
Alzheimer’s disease is characterized by the extracellular accumulation of the amyloidβin the form of amyloid plaques and the intracellular deposition of the microtubule-associated protein tau in the form of neurofibrillary tangles.Most of the Alzheimer’s drugs targeting amyloidβhave been failed in clinical trials.Particularly,tau pathology connects greatly in the pathogenesis of Alzheimer’s disease.Tau protein enhances the stabilization of microtubules that leads to the appropriate function of the neuron.Changes in the quantity or the conformation of tau protein could affect its function as a microtubules stabilizer and some of the processes wherein it is involved.The molecular mechanisms leading to the accumulation of tau are principally signified by numerous posttranslational modifications that change its conformation and structural state.Therefore,aberrant phosphorylation,as well as truncation of tau protein,has come into focus as significant mechanisms that make tau protein in a pathological entity.Furthermore,the shape-shifting nature of tau advocates to comprehend the progression of Alzheimer’s disease precisely.In this review,we emphasize the recent studies about the toxic and shape-shifting nature of tau in the pathogenesis of Alzheimer’s disease.  相似文献   
3.
ABSTRACT

Purpose

To investigate the expression of IL-11 and its receptor IL-11Rα and to quantify density of CD163+ M2 macrophages in proliferative diabetic retinopathy (PDR).  相似文献   
4.
Background: Betel quid chewing is more common among the older generation in rural areas of Malaysia. Oral cancer in Asia has been associated with the habit of chewing betel quid and areca nut. Objective:  This study aims to investigate the cytotoxic effects of betel quid and areca nut extracts on the fibroblast (L929), mouth-ordinary-epithelium 1 (MOE1) and oral squamous cell carcinoma (HSC-2) cell lines. Methods: L929, MOE1 and HSC-2 cells were treated with 0.1, 0.2 and 0.4 g/ml of betel quid and areca nut extracts for 24, 48 and 72 h. MTT assay was performed to assess the cell viability. Results: Both extracts, regardless of concentration, significantly reduced the cell viability of L929 compared with the control (P<0.05). Cell viability of MOE1 was significantly enhanced by all betel quid concentrations compared with the control (P<0.05). By contrast, 0.4 g/ml of areca nut extract significantly reduced the cell viability of MOE1 at 48 and 72 h of incubation. Cell viability of HSC-2 was significantly lowered by all areca nut extracts, but 0.4 g/ml of betel quid significantly increased the cell viability of HSC-2 (P<0.05). Conclusion: Areca nut extract is cytotoxic to L929 and HSC-2, whereas the lower concentrations of areca nut extract significantly increased the cell viability of MOE1 compared to the higher concentration and control group. Although betel quid extract is cytotoxic to L929, the same effect is not observed in MOE1 and HSC-2 cell lines. Further investigations are needed to clarify the mechanism of action.  相似文献   
5.
The Impella 5.0, a percutaneously inserted left ventricular assist device, has been used to support patients who have severe heart failure or who are undergoing high-risk percutaneous coronary intervention. We report our surgical placement of the Impella 5.0, through a graft sewn to the aorta, to unload the left ventricle of a 59-year-old man who was undergoing venoarterial extracorporeal membrane oxygenation for postcardiotomy shock. The patient underwent successful placement of a long-term left ventricular assist device before his discharge from the hospital. The versatility of the Impella 5.0 is exemplified in this patient who was successfully bridged to long-term support.  相似文献   
6.
7.
目的探讨乳腺癌患者乳腺癌组织中的缺氧诱导因子-1α(HIF-1α)、Ki-67蛋白的表达与超声声像特征的关系。方法对110例乳腺癌患者进行超声检查,观察患者的毛刺征、肿块形态、钙化灶形态和血流显像分级等。取110例乳腺癌患者的乳腺癌组织,免疫组化法检测HIF-1α、Ki-67蛋白的阳性表达率。分析不同超声声像特征乳腺癌患者乳腺癌组织中HIF-1α、Ki-67蛋白的表达情况。结果110例乳腺癌患者中,43例既存在Ki-67蛋白阳性表达又存在HIF-1α蛋白阳性表达,35例仅存在Ki-67蛋白阳性表达,13例仅存在HIF-1α蛋白阳性表达,Ki-67、HIF-1α蛋白阴性表达患者共19例。乳腺癌患者乳腺癌组织中Ki-67蛋白的阳性表达率为70.91%(78/110),HIF-1α蛋白的阳性表达率为50.91%(56/110)。不同肿块形态、钙化灶形态、血流显像分级乳腺癌患者乳腺癌组织中Ki-67蛋白阳性表达率比较,差异均有统计学意义(P﹤0.05)。不同血流显像分级乳腺癌患者乳腺癌组织中HIF-1α蛋白阳性表达率比较,差异有统计学意义(P﹤0.05)。结论乳腺癌患者乳腺癌组织中HIF-1α的表达可能与血流显像分级有关,Ki-67的表达可能与肿块形态、钙化灶形态及血流显像分级有关。  相似文献   
8.
Introduction: Surgery in patients with head and neck cancers is frequently complicated by multiple stages of procedure that includes significant surgical removal of all or part of an organ with cancer, tissue reconstruction, and extensive neck dissection. Postoperative wound infections, termed ‘surgical site infections’ (SSIs) are a significant impediment to head-and-neck cancer surgery and recovery, and need to be addressed.

Areas covered: Approximately 10–45% of patients undergoing head-and-neck cancers surgery develop SSIs. SSIs can lead to delayed wound healing, increased morbidity and mortality as well as costs. Consequently, SSIs need to be avoided where possible, as even the surgery itself impacts on patients’ subsequent activities and their quality of life, which is exacerbated by SSIs. Several risk factors for SSIs need to be considered to reduce future rates, and care is also needed in the selection and duration of antibiotic prophylaxis.

Expert commentary: Head and neck surgeons should give personalized care especially to patients at high risk of SSIs. Such patients include those who have had chemoradiotherapy and need reconstructive surgery, and patients from lower and middle-income countries and from poorer communities in high income countries, who often have high levels of co-morbidity because of resource constraints.  相似文献   

9.
The aim of the study was to explore the relationship between college graduates’ dual self-consciousness, job search clarity and perceived stress, and reveal the mediating role of perceived stress between dual self-consciousness and job search clarity. In this study, 467 college graduates were investigated using the Dual Self-Consciousness Scale, Job Search Clarity Scale, and Perceived Stress Scale. After controlling for gender, age, and region, the results revealed that: (1) private self-consciousness has a significant positive predictive effect on job search clarity; (2) perceived stress has a significant negative predictive effect on job search clarity; (3) perceived stress plays partial mediation effects between private self-consciousness and job search clarity; (4) perceived stress plays complete mediation effects between public self-consciousness and job search clarity; (5) perceived stress has suppressing effects between public self-consciousness and job search clarity.  相似文献   
10.
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