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   5220篇
  免费   262篇
  国内免费   16篇
耳鼻咽喉   42篇
儿科学   343篇
妇产科学   115篇
基础医学   771篇
口腔科学   132篇
临床医学   364篇
内科学   912篇
皮肤病学   433篇
神经病学   280篇
特种医学   77篇
外科学   458篇
综合类   108篇
一般理论   1篇
预防医学   326篇
眼科学   238篇
药学   546篇
中国医学   21篇
肿瘤学   331篇
  2023年   50篇
  2022年   172篇
  2021年   247篇
  2020年   130篇
  2019年   163篇
  2018年   178篇
  2017年   129篇
  2016年   166篇
  2015年   158篇
  2014年   208篇
  2013年   261篇
  2012年   369篇
  2011年   358篇
  2010年   232篇
  2009年   196篇
  2008年   250篇
  2007年   235篇
  2006年   256篇
  2005年   236篇
  2004年   201篇
  2003年   187篇
  2002年   202篇
  2001年   86篇
  2000年   100篇
  1999年   79篇
  1998年   37篇
  1997年   34篇
  1996年   32篇
  1995年   15篇
  1994年   20篇
  1993年   22篇
  1992年   41篇
  1991年   30篇
  1990年   51篇
  1989年   46篇
  1988年   39篇
  1987年   31篇
  1986年   28篇
  1985年   26篇
  1984年   26篇
  1983年   20篇
  1982年   15篇
  1981年   11篇
  1980年   13篇
  1979年   14篇
  1978年   12篇
  1977年   18篇
  1976年   7篇
  1974年   9篇
  1971年   7篇
排序方式: 共有5498条查询结果,搜索用时 15 毫秒
101.
102.
103.
Soil manganese (Mn) deficiency limits the growth and crop yield. Growing Mn efficient cultivars i.e. the cultivars with high yield at low Mn supply would represent a long term solution and sustainable approach to crop production. To evaluate Mn efficiency of 38 diverse rice genotypes, field experiment was conducted during kharif seasons using Mn deficient (2.20?mg?kg?1) soil. Typic Ustrochrepts loamy sand soil, treated with 0?kg Mn?ha?1 (no Mn, low level) and 20?kg Mn?ha?1 supplemented with two foliar sprays@ 0.5?% MnSO4 (high level). The relative grain yield i.e. Mn efficiency index varied from 100 to 84?% and relative grain Mn uptake i.e. Mn efficiency from 80 to 53?% among the genotypes and the cultivar PR116 was having highest Mn efficiency index as well as efficiency. On the basis of grain yield and Mn efficiency, genotypes were classified as efficient and responsive (PR116, 3047, PAU201, 3131, 3125, HKR127, 3106, 3129, 3128, 3100 and 3138), efficient and nonresponsive (PR120, PR113, 3126, 3033, 3132, 3056, 3130, 3036, 3109, 3124, 3101 and 3136), inefficient and responsive (3127, PR115, 3133, 3134 and 3142), and inefficient and nonresponsive (PR114, PR118, 3137, PR111, 3108, PUSA44, 3135, 3139, 3140 and 3141). From a practical point of view, genotypes that produce high grain yield at a low level of Mn and respond well to Mn additions are the most desirable because they are able to express their high yield potential in a wide range of Mn availability.  相似文献   
104.
Cardiac transplantation is indicated for patients with end-stage cardiomyopathy secondary to cardiac sarcoidosis. Although rare, recurrent disease has been reported in two cases. The current report presents a case of recurrent cardiac sarcoidosis in a patient 45 months postorthotopic heart transplantation and 40 months following reactivation of latent Mycobacterium tuberculosis infection. The patient was the first to have recurrent disease following an infection that has been proposed to be involved in its pathogenesis. The patient’s interval between transplant and recurrence is the longest reported to date.  相似文献   
105.
106.

Background

Fine-needle aspiration (FNA) of adrenals is needed in patients with pyrexia of unknown origin (PUO) and adrenal enlargement in absence of other diagnostic clues. Adrenals are easily accessible by endoscopic ultrasound (EUS) due to proximity; however, there is no systemic study available on FNA of adrenals in patients with PUO. The aim of this study was to evaluate the diagnostic yield and safety of EUS-FNA of enlarged adrenal in patients with PUO.

Methods

Data was analyzed from October 2010 to September 2016 at a single tertiary care center in northern India. EUS-FNA of enlarged adrenals was done in 52 patients for the etiological diagnosis of PUO in whom a definitive diagnosis could not be made with other means.

Results

The mean age was 48±14 years; 36 were males and 16 were females. EUS-FNA was done from the left adrenal in 50 patients and from the right sample in 2 patients. A technical success was achieved in 100% cases. The 19-G needle was used in the majority (75%) to the presence of necrotic areas in adrenals; median numbers of passes were 2. The cytopathological diagnoses were tuberculosis (n?=?36), histoplasmosis (n?=?13), lymphoma (n?=?2), and metastasis from undiagnosed neuroendocrine tumor of lung (n?=?1). Thus, a diagnosis could be made in 52/52 (100%) patients. None of the patients had any procedure-related complications.

Conclusions

EUS-FNA is a safe and effective method for evaluating etiology of PUO in patients with adrenal enlargement.
  相似文献   
107.
108.
Arterial chronic total occlusions (CTO) are a common and clinically relevant problem in patients with coronary artery disease. Percutaneous coronary intervention (PCI) success rates in a wide range of CTO are low, primarily due to inability of guidewire crossing. The pathophysiology of CTO is poorly understood and limits our ability to introduce innovative therapies. Recent studies from our laboratory have suggested that microvessel formation within arterial CTO is a complex process with temporal and regional differences. Moreover, there is evidence from pilot studies that the presence of either microvessels or the particular extracellular matrix environment in the adjacent perivascular tissue can facilitate guidewire crossing and successful PCI. Currently, studies are underway in our experimental CTO model to delineate the pathophysiology of microvessel formation in CTO and its potential role in PCI.  相似文献   
109.
OBJECTIVES: To determine whether a change in practice to introduce a multidisciplinary fall-prevention program can reduce falls and injury in nonacute patients in a rehabilitation hospital. DESIGN: A quasi-experimental study. SETTING: Three geriatric wards with a similar design, equipment, staffing levels, and skill mix. PARTICIPANTS: Eight hundred twenty-five consecutive patients. INTERVENTION: The patients' fall-risk status was assessed using the Downton Score. Current practice was maintained on the two control wards (n=550). On the experimental ward (n=275), a fall-prevention program was introduced. A multidisciplinary team met weekly specifically to discuss patients' fall risk and formulate a targeted plan. Patients at risk were identified using wristbands; risk factors were corrected or environmental changes made to enhance safety. MEASUREMENTS: Primary outcomes were number of fallers, recurrent fallers, total falls, patients sustaining injury, and falls per occupied bed days. Secondary outcomes were place of discharge and mortality. RESULTS: Patients were matched for age and risk status. Control wards had proportionally more fallers (20.2% vs 14.2%: P=.033), patients sustaining injury (8.2% vs 4%: P=.025), and total number of falls (170 vs 72: P=.045). These results did not remain significant after controlling for differing length of stay. There was no reduction in recurrent fallers (6.4% vs 4.7%: P=.43) and no effect on place of discharge (home discharges; 57.5% vs 60.7%: P=.41) or mortality (15.3% vs 13.8%: P=.60). CONCLUSION: This study shows that falls might be reduced in a multidisciplinary fall-prevention program, but the results are not definitive because of the borderline significance achieved and the variable length of stay. More research on fall prevention in hospital is required, particularly as to what interventions, if any, are effective at reducing falls in this group of patients.  相似文献   
110.
Coronary artery disease has assumed alarming proportions in Indians and often affects people at younger age. Traditional risk factors fail to explain the high incidence of disease. Although lipoprotein(a) has been shown to be a powerful risk factor for atherosclerosis, there is very limited data with regard to its significance in premature coronary artery disease. The present study was therefore undertaken to assess lipoprotein(a) levels and its role as a marker of coronary artery disease in patients below the age of 40 years. Lipid profile and lipoprotein(a) levels were estimated in 50 patients of angiographically proven coronary artery disease and an equal number of age-matched healthy controls. There was no significant difference in the family history of coronary artery disease, body mass index and waist-hip ratio between the two groups. Total plasma cholesterol, triglyceride and LDL-cholesterol levels were significantly higher and HDL-cholesterol significantly lower in patients as compared to controls. In patients of coronary artery disease, mean lipoprotein(a) levels, measured by ELISA method, were 35.0 +/- 32.4 mg/dL and the median was 26.7 mg/dL. These values were significantly higher than the mean of 20.3 +/- 17.0 mg/dL (p < 0.002) and the median of 13.8 mg/dL (p < 0.015) in controls. Multiple regression analysis, to assess the influence of various risk factors, showed that low HDL-cholesterol (odds ratio 4.62, 95% CI 1.84-11.60; p < 0.015) and elevated lipoprotein(a) levels (odds ratio 3.06, 95% CI 1.24-7.55; p < 0.001) were independent risk factors, whereas high total cholesterol and triglyceride levels did not have any independent influence on premature coronary artery disease. Our data thus suggest that lipoprotein (a) levels are elevated and constitute an independent risk factor in patients with premature coronary artery disease below 40 years of age.  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