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   119048篇
  免费   8103篇
  国内免费   627篇
耳鼻咽喉   1475篇
儿科学   2717篇
妇产科学   1904篇
基础医学   15333篇
口腔科学   3561篇
临床医学   11082篇
内科学   27170篇
皮肤病学   2145篇
神经病学   11059篇
特种医学   4340篇
外国民族医学   1篇
外科学   19381篇
综合类   908篇
一般理论   198篇
预防医学   8450篇
眼科学   2273篇
药学   7255篇
中国医学   263篇
肿瘤学   8263篇
  2023年   904篇
  2022年   1557篇
  2021年   4093篇
  2020年   2273篇
  2019年   3536篇
  2018年   4223篇
  2017年   2896篇
  2016年   3038篇
  2015年   3568篇
  2014年   4928篇
  2013年   6249篇
  2012年   9496篇
  2011年   9793篇
  2010年   5315篇
  2009年   4652篇
  2008年   7867篇
  2007年   7774篇
  2006年   7461篇
  2005年   7214篇
  2004年   6467篇
  2003年   5864篇
  2002年   5336篇
  2001年   777篇
  2000年   647篇
  1999年   827篇
  1998年   1057篇
  1997年   859篇
  1996年   690篇
  1995年   649篇
  1994年   521篇
  1993年   539篇
  1992年   424篇
  1991年   394篇
  1990年   353篇
  1989年   318篇
  1988年   319篇
  1987年   285篇
  1986年   324篇
  1985年   322篇
  1984年   393篇
  1983年   337篇
  1982年   373篇
  1981年   380篇
  1980年   285篇
  1979年   175篇
  1978年   210篇
  1977年   185篇
  1976年   141篇
  1975年   150篇
  1974年   153篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
ABSTRACT

Objective: The purpose of this study was to examine the influence of a total knee arthroplasty (TKA) on linked cranial and caudal structures.

Methods: Thirty-five (14f/21m) subjects participated in this study: 15 subjects (9f, 6m) pre- and post- TKA and a control group of 20 subjects (5f, 15m). The measurements included: jaw condyle position and movement, back scan, plantar pressure distribution, and body sway.

Results: There were no significant differences in electronic position analysis of the jaw; however, the protrusion of the TKA group improved (p = 0.001). The test group had a more anteriorly inclined thoracic spine and a less pronounced lumbar lordosis. Before and after surgery, the body sway in the test group was larger.

Conclusion: The TKA affected most prominently the static mechanisms of the postural control and the spine position. The trajectories of the mandible during protrusion also changed slightly.  相似文献   
33.
Food-grade titanium dioxide (E171) is widely used as a food additive, and it is known that after oral consumption, E171 is translocated into the bloodstream reaching the highest titanium level at 6 h. E171 is accumulated in some organs triggering toxicity, but the effects on the blood parameters after oral consumption have been less studied. Recently, evidence shows that oral exposure to E171 induces behavioral signs of anxiety and depression. The relation between blood alterations and psychiatric disorders has been previously demonstrated. However, the oral exposure to E171 effects on alterations in blood parameters and effects linked to alterations in animal behavior has not been explored. In this short communication, we aimed to investigate the effects of E171 on specific blood parameters (hematocrit, hemoglobin, number of erythrocytes, and leukocytes) and anxiety and compulsive-like behavior in males and females orally exposed to ~5 mg/kg for 4 weeks. The results showed that E171 decreased hematocrit and hemoglobin in male but not in female mice while leukocyte and erythrocyte count remained unaltered. Oral consumption of E171 decreased the levels of anxiety-like behavior in females but not in male mice, while compulsive-like behavior was increased in both male and female mice.  相似文献   
34.

Purpose

A hydrogel rectal spacer (HRS) is a medical device that is approved by the U.S. Food and Drug Administration to increase the separation between the prostate and rectum. We conducted a cost-effectiveness analysis of HRS use for reduction in radiation therapy (RT) toxicities in patients with prostate cancer (PC) undergoing external beam RT (EBRT).

Methods and Materials

A multistate Markov model was constructed from the U.S. payer perspective to examine the cost-effectiveness of HRS in men with localized PC receiving EBRT (EBRT alone vs EBRT + HRS). The subgroups analyzed included site of HRS placement (hospital outpatient, physician office, ambulatory surgery center) and proportion of patients with good baseline erectile function (EF). Data on EF, gastrointestinal and genitourinary toxicities incidence, and potential risks associated with HRS implantation were obtained from a recently published randomized clinical trial. Health utilities and costs were derived from the literature and the 2018 Physician Fee Schedule and were discounted 3% annually. Quality-adjusted life years (QALYs) and costs were modeled for a 5-year period from receipt of RT. Probabilistic sensitivity analysis and value-based threshold analyses were conducted.

Results

The per-patient 5-year incremental cost for spacers administered in a hospital outpatient setting was $3578, and the incremental effectiveness was 0.0371 QALYs. The incremental cost-effectiveness ratio was $96,440/QALY for patients with PC undergoing HRS insertion in a hospital and $39,286/QALY for patients undergoing HRS insertion in an ambulatory facility. For men with good baseline EF, the incremental cost-effectiveness ratio was $35,548/QALY and $9627/QALY in hospital outpatient and ambulatory facility settings, respectively.

Conclusions

Based on the current Medicare Physician Fee Schedule, HRS is cost-effective at a willingness to pay threshold of $100,000. These results contain substantial uncertainty, suggesting more evidence is needed to refine future decision-making.  相似文献   
35.
Using data on waterfowl band recoveries, we identified spatially explicit hotspots of concentrated waterfowl movement to predict occurrence and spatial spread of a novel influenza A virus (clade 2.3.4.4) introduced from Asia by waterfowl from an initial outbreak in North America in November 2014. In response to the outbreak, the hotspots of waterfowl movement were used to help guide sampling for clade 2.3.4.4 viruses in waterfowl as an early warning for the US poultry industry during the outbreak . After surveillance sampling of waterfowl, we tested whether there was greater detection of clade 2.3.4.4 viruses inside hotspots. We found that hotspots defined using kernel density estimates of waterfowl band recoveries worked well in predicting areas with higher prevalence of the viruses in waterfowl. This approach exemplifies the value of ecological knowledge in predicting risk to agricultural security.  相似文献   
36.

Background

The optimal noninvasive test (NIT) for patients with diabetes and stable symptoms of coronary artery disease (CAD) is unknown.

Objectives

The purpose of this study was to assess whether a diagnostic strategy based on coronary computed tomographic angiography (CTA) is superior to functional stress testing in reducing adverse cardiovascular (CV) outcomes (CV death or myocardial infarction [MI]) among symptomatic patients with diabetes.

Methods

PROMISE (Prospective Multicenter Imaging Study for Evaluation of Chest Pain) was a randomized trial evaluating an initial strategy of CTA versus functional testing in stable outpatients with symptoms suggestive of CAD. The study compared CV outcomes in patients with diabetes (n = 1,908 [21%]) and without diabetes (n = 7,058 [79%]) based on their randomization to CTA or functional testing.

Results

Patients with diabetes (vs. without) were similar in age (median 61 years vs. 60 years) and sex (female 54% vs. 52%) but had a greater burden of CV comorbidities. Patients with diabetes who underwent CTA had a lower risk of CV death/MI compared with functional stress testing (CTA: 1.1% [10 of 936] vs. stress testing: 2.6% [25 of 972]; adjusted hazard ratio: 0.38; 95% confidence interval: 0.18 to 0.79; p = 0.01). There was no significant difference in nondiabetic patients (CTA: 1.4% [50 of 3,564] vs. stress testing: 1.3% [45 of 3,494]; adjusted hazard ratio: 1.03; 95% confidence interval: 0.69 to 1.54; p = 0.887; interaction term for diabetes p value = 0.02).

Conclusions

In diabetic patients presenting with stable chest pain, a CTA strategy resulted in fewer adverse CV outcomes than a functional testing strategy. CTA may be considered as the initial diagnostic strategy in this subgroup. (PROspective Multicenter Imaging Study for Evaluation of Chest Pain [PROMISE]; NCT01174550)  相似文献   
37.
38.
Melatonin, the main hormone produced by the pineal gland, is secreted in a circadian manner (24‐hr period), and its oscillation influences several circadian biological rhythms, such as the regulation of clock genes expression (chronobiotic effect) and the modulation of several endocrine functions in peripheral tissues. Assuming that the circadian synchronization of clock genes can play a role in the regulation of energy metabolism and it is influenced by melatonin, our study was designed to assess possible alterations as a consequence of melatonin absence on the circadian expression of clock genes in the epididymal adipose tissue of male Wistar rats and the possible metabolic repercussions to this tissue. Our data show that pinealectomy indeed has impacts on molecular events: it abolishes the daily pattern of the expression of Clock, Per2, and Cry1 clock genes and Pparγ expression, significantly increases the amplitude of daily expression of Rev‐erbα, and affects the pattern of and impairs adipokine production, leading to a decrease in leptin levels. However, regarding some metabolic aspects of adipocyte functions, such as its ability to synthesize triacylglycerols from glucose along 24 hr, was not compromised by pinealectomy, although the daily profile of the lipogenic enzymes expression (ATP‐citrate lyase, malic enzyme, fatty acid synthase, and glucose‐6‐phosphate dehydrogenase) was abolished in pinealectomized animals.  相似文献   
39.
BackgroundVenoarterial extracorporeal membrane oxygenation (VA-ECMO) is increasingly used as a life-saving therapy for patients with cardiovascular collapse, but identifying patients unlikely to benefit remains a challenge.Methods and ResultsWe created the RESCUE registry, a retrospective, observational registry of adult patients treated with VA-ECMO between January 2007 and June 2017 at 3 high-volume centers (Columbia University, Duke University, and Washington University) to describe short-term patient outcomes. In 723 patients treated with VA-ECMO, the most common indications for deployment were postcardiotomy shock (31%), cardiomyopathy (including acute heart failure) (26%), and myocardial infarction (17%). Patients frequently suffered in-hospital complications, including acute renal dysfunction (45%), major bleeding (41%), and infection (33%). Only 40% of patients (n = 290) survived to discharge, with a minority receiving durable cardiac support (left ventricular assist device [n = 48] or heart transplantation [n = 7]). Multivariable regression analysis identified risk factors for mortality on ECMO as older age (odds ratio [OR], 1.26; 95% confidence interval [CI], 1.12–1.42) and female sex (OR, 1.44; 95% CI, 1.02–2.02) and risk factors for mortality after decannulation as higher body mass index (OR 1.17; 95% CI, 1.01-1.35) and major bleeding while on ECMO support (OR, 1.92; 95% CI, 1.23–2.99).ConclusionsDespite contemporary care at high-volume centers, patients treated with VA-ECMO continue to have significant in-hospital morbidity and mortality. The optimization of outcomes will require refinements in patient selection and improvement of care delivery.  相似文献   
40.
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