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   2761篇
  免费   111篇
  国内免费   33篇
耳鼻咽喉   7篇
儿科学   107篇
妇产科学   30篇
基础医学   533篇
口腔科学   106篇
临床医学   346篇
内科学   596篇
皮肤病学   113篇
神经病学   116篇
特种医学   279篇
外科学   264篇
综合类   53篇
预防医学   109篇
眼科学   29篇
药学   165篇
中国医学   1篇
肿瘤学   51篇
  2016年   28篇
  2015年   36篇
  2014年   35篇
  2013年   89篇
  2012年   54篇
  2011年   38篇
  2010年   56篇
  2009年   46篇
  2008年   54篇
  2007年   81篇
  2006年   77篇
  2005年   53篇
  2004年   48篇
  2003年   57篇
  2002年   46篇
  2001年   55篇
  2000年   47篇
  1999年   47篇
  1998年   87篇
  1997年   98篇
  1996年   109篇
  1995年   74篇
  1994年   76篇
  1993年   77篇
  1992年   50篇
  1991年   50篇
  1990年   51篇
  1989年   73篇
  1988年   66篇
  1987年   53篇
  1986年   56篇
  1985年   43篇
  1984年   61篇
  1983年   33篇
  1982年   34篇
  1981年   40篇
  1980年   52篇
  1979年   29篇
  1978年   27篇
  1977年   43篇
  1976年   41篇
  1975年   40篇
  1972年   29篇
  1971年   28篇
  1965年   51篇
  1964年   50篇
  1963年   47篇
  1962年   41篇
  1961年   40篇
  1960年   65篇
排序方式: 共有2905条查询结果,搜索用时 0 毫秒
81.
The combination of captopril and nitroglycerin early after acutemyocardial infarction (AMI) could lead to a dangerous decreasein blood pressure coronary perfusion. To evaluate the safetyaspects and haemodynamic effects of this combination, we studied36 first ‘Q wave’ thrombolysed anterior wall AMIpatients during the 24 h following the onset of symptoms. Afterwards, thrombolysis patients received a continuous infusionof nitroglycerin and were submitted to pulmonary artery catheterization.Those patients with mean arterial pressure (MAP) 70 mmHg, cardiacindex 2.21. min–1.m–2, and wedge pressure 10 mmHgwere included and randomized to receive 6.25 mg of captoprilevery 6 h on the first day and 12.5 mg qid on the second f MAP 70mmHg (group 1). A second group (group 2) received a placebo.Haemodynamic parameters were determined after 1, 6 and thenevery 6 h up to 48 h after basal measurements. Significant differenceswere observed only for the MAP and the rate-pressure product(reduction in group 1 values, P <0.05). However, MAP wasmaintained within acceptable limits. Our data support the factthat the combination of captopril and nitroglycerin in the earlyhours of a non-complicated anterior wall AMI is safe, and couldguarantee its use in large clinical trials to determine theeffects on left ventricle remodelling and survival after AMI.  相似文献   
82.

Background

Dietary oleic acid may prevent pancreatic ductal adenocarcinoma (PDA) by reducing hyperinsulinaemia which can otherwise promote DNA damage and tumour growth. Results from previous epidemiological studies investigating oleic acid are inconsistent. This study aims to clarify the relationship between dietary oleic acid intake and the risk of developing PDA using nutritional information from food diaries plus published serum biomarker data from HbA1c.

Methods

23,658 participants, aged 40–74 years, were recruited into EPIC-Norfolk and completed 7-day food diaries which recorded; foods, brands and portion sizes to calculate nutrient intakes. Serum HbA1c was measured at recruitment in 11,147 participants (48.7% of cohort). Hazard ratios (HRs) for quintiles of dietary oleic acid intake and serum HbA1c were estimated using Cox regression. Additional analyses were made according to whether body mass index (BMI) was greater or less than 25?kg/m2 as this influences hyperinsulinaemia.

Results

88 participants (55% women) developed PDA after a mean follow-up of 8.4 years (SD?=?3.9) (mean age at diagnosis?=?72.6 years, SD?=?8.8). A decreased risk of PDA was associated with increased dietary oleic acid intake (highest vs lowest quintile, HR?=?0.29, 95% CI?=?0.10–0.81, P trend across quintiles?=?0.011), with statistical significance maintained when BMI>25?kg/m2 but not if BMI<25?kg/m2. An elevated serum HbA1c was associated with increased risk of disease (highest vs lowest quintiles, HR?=?6.32, 95% CI?=?1.38–28.89, P for trend?=?0.004).

Conclusions

The data supports a protective role of oleic acid against development of PDA in those with higher BMIs possibly through influencing hyperinsulinaemia. Oleic acid intake should be accurately measured in future aetiological studies.  相似文献   
83.
Using accepted diagnostic criteria we have selected, for study, 160 patients with Crohn's disease involving the colon. There is a remarkable discrepancy between the clinical diagnosis prior to or at the time of initial admission to this hospital and the diagnosis following definitive investigation and observation of the progression of disease.
The peak age incidence occurred in the second decode The colitis group showed a greater percentage of patients over 30 years of age. Although histopathology was not obtained in all patients, there appeared to be sparing of the ascending colon in a small percentage (9%) of patients with ileocolitis.
Comparison of the clinical features of granulomatous disease limited to the colon and granulomatous ileocolitis shows a significantly greater incidence of extraintestinal symptoms and overt bleeding in the former. Nausea, vomiting, subacute obstruction, abdominal mass and internal fistulas were substantially more common in ileocolitis but the difference was not statistically significant. In this series retroperitoneal abscess did not occur in patients with disease localized to the colon. In the 10 patients with ileocolitis who developed an abscess, however, the site of fistula was the colon in four patients. In one of these, the abscess was left-sided.  相似文献   
84.
85.
86.
Objective:To compare the flexural properties of rectangular nickel-titanium (Ni-Ti) orthodontic wires in occlusoapical and faciolingual orientations using a standardized test method.Materials and Methods:Twenty-two rectangular Ni-Ti wire groups were tested in occlusoapical (ribbon) orientation: eight conventional Ni-Ti products, five superelastic Ni-Ti products, and nine thermal Ni-Ti products (n = 10 per group). Six products of thermal Ni-Ti wire were tested in faciolingual (edgewise) orientation. A three-point bending test was performed to measure deactivation force at 3.0-, 2.0-, 1.0-, and 0.5-mm deflections of each rectangular wire at 37.0 ± 0.5°C. Analysis of variance and post hoc Student-Newman-Keuls tests were used to compare the mean values of the different groups (α = .05).Results:The ranges of deactivation forces varied greatly with different kinds, sizes, products, and deflections of Ni-Ti wires. One product of conventional and superelastic Ni-Ti wires had steeper force-deflection curves. Four products had similarly shaped flat force-deflection curves, whereas the sixth product had a moderately steep force-deflection curve. Thermal Ni-Ti wires had smaller deactivation forces ranging from 0.773 N (78.8 g) to 2.475 N (252.4 g) between deflections of 1.0 and 0.5 mm, whereas wider ranges of force from 3.371 N (343.7 g) to 9.343 N (952.7 g) were predominantly found among conventional Ni-Ti wires between deflections of 3.0 and 2.0 mm.Conclusions:Clinicians should critically select archwires for use in the occlusoapical orientation not only based on Ni-Ti wire type, size (0.022 × 0.016-in or 0.025 × 0.017-in), and product but also with deactivation deflections from 0.5 and 1.0 mm to obtain light forces in the occlusoapical orientation.  相似文献   
87.
Bartonella henselae is associated with a wide spectrum of clinical manifestations, including cat scratch disease, endocarditis and meningoencephalitis, in immunocompetent and immunocompromised patients. We report the first molecularly confirmed case of B. henselae infection in an AIDS patient in state of Rio de Janeiro, Brazil. Although DNA sequence of B. henselae has been detected by polymerase chain reaction in a lymph node biopsy, acute and convalescent sera were nonreactive.  相似文献   
88.
89.
90.
This is the second part of a two‐part piece on self‐adhesive resin cements; Part I was presented in the previous issue of the Journal. Here in Part II, the specific topics concerning self‐adhesive cements are clinical performance, post‐cementation sensitivity, and cementation of endodontic posts.  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