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   4862篇
  免费   321篇
  国内免费   11篇
耳鼻咽喉   168篇
儿科学   86篇
妇产科学   78篇
基础医学   691篇
口腔科学   245篇
临床医学   458篇
内科学   888篇
皮肤病学   54篇
神经病学   473篇
特种医学   281篇
外科学   624篇
综合类   26篇
一般理论   3篇
预防医学   411篇
眼科学   110篇
药学   262篇
中国医学   7篇
肿瘤学   329篇
  2023年   44篇
  2021年   56篇
  2020年   71篇
  2019年   111篇
  2018年   98篇
  2017年   88篇
  2016年   72篇
  2015年   76篇
  2014年   99篇
  2013年   159篇
  2012年   220篇
  2011年   211篇
  2010年   140篇
  2009年   127篇
  2008年   218篇
  2007年   201篇
  2006年   192篇
  2005年   199篇
  2004年   179篇
  2003年   147篇
  2002年   143篇
  2001年   177篇
  2000年   149篇
  1999年   110篇
  1998年   69篇
  1997年   53篇
  1996年   62篇
  1995年   52篇
  1994年   47篇
  1993年   47篇
  1992年   89篇
  1991年   104篇
  1990年   120篇
  1989年   112篇
  1988年   76篇
  1987年   92篇
  1986年   87篇
  1985年   72篇
  1984年   68篇
  1983年   48篇
  1982年   50篇
  1981年   31篇
  1980年   40篇
  1979年   66篇
  1978年   40篇
  1977年   35篇
  1975年   44篇
  1974年   37篇
  1973年   31篇
  1970年   35篇
排序方式: 共有5194条查询结果,搜索用时 11 毫秒
71.
Nursing for Women's Health convened a group of nurse researchers for a roundtable discussion about the relationship of research to the profession of nursing, how research drives evidence‐based practice and how nurses can get involved in research and in its application to the care of women and newborns.  相似文献   
72.
BACKGROUND: Considerable research has been conducted into the nature of airway inflammation in chronic obstructive pulmonary disease (COPD) but the relationship between proximal airways inflammation and both dynamic collapse of the peripheral airways and HRCT determined emphysema severity remains unknown. A number of research tools have been combined to study smokers with a range of COPD severities classified according to the GOLD criteria. METHODS: Sixty five subjects (11 healthy smokers, 44 smokers with stage 0-IV COPD, and 10 healthy non-smokers) were assessed using lung function testing and HRCT scanning to quantify emphysema and peripheral airway dysfunction and sputum induction to measure airway inflammation. RESULTS: Expiratory HRCT measurements and the expiratory/inspiratory mean lung density ratio (both indicators of peripheral airway dysfunction) correlated more closely in smokers with the severity of airflow obstruction (r = -0.64, p<0.001) than did inspiratory HRCT measurements (which reflect emphysema severity; r = -0.45, p<0.01). Raised sputum neutrophil counts also correlated strongly in smokers with HRCT indicators of peripheral airway dysfunction (r = 0.55, p<0.001) but did not correlate with HRCT indicators of the severity of emphysema. CONCLUSIONS: This study suggests that peripheral airway dysfunction, assessed by expiratory HRCT measurements, is a determinant of COPD severity. Airway neutrophilia, a central feature of COPD, is closely associated with the severity of peripheral airway dysfunction in COPD but is not related to the overall severity of emphysema as measured by HRCT.  相似文献   
73.
Colorectal cancer is the third most common malignancy and cause of cancer-related deaths worldwide. Approximately half of the patients diagnosed with colorectal cancer ultimately die of the condition. Death from colorectal cancer can be prevented by early detection, but unfortunately presentation is often late, with a worse prognosis. Screening by fecal occult blood testing reduces disease-specific mortality, but there is a need for sensitive and specific noninvasive biomarkers to facilitate detecting the disease, staging it, and predicting the best therapeutic options. MicroRNAs (miRNAs) are short noncoding RNA sequences that have a crucial role in the regulation of gene expression. They have significant regulatory functions in basic cellular processes, such as cell differentiation, proliferation, and apoptosis. Evidence suggests that miRNAs may function as both tumor suppressors and oncogenes. The main mechanism for changes in the function of miRNAs in cancer cells is due to aberrant gene expression. Accurate discrimination of miRNA profiles between tumor and normal mucosa in colorectal cancer allows definition of specific expression patterns of miRNAs, giving good potential as diagnostic and therapeutic targets. MiRNAs expressed in colorectal cancers are also abundantly present and stable in stool and plasma samples. Their extraction from these three sources is feasible and reproducible. The ease and reliability of determining miRNA profiles in plasma or stool makes them potential molecular markers for colorectal cancer screening. This review summarizes the role miRNAs have in colorectal cancer, highlighting particularly the potential diagnostic, prognostic, and therapeutic implications in the future treatment of the disease.  相似文献   
74.
75.
76.
77.
We studied the kinematics of 8 ligamentous unstable elbow joint preparations after application of the Orthofix elbow external fixation device. Valgus, varus, external rotatory, and internal rotatory load tests were performed in lateral collateral ligament (LCL)-deficient and LCL/medial collateral ligament (MCL)-deficient joints. After placement of the fixator, the mean extension decreased significantly to 19.5 degrees +/- 7.2 degrees in the LCL-deficient joint and to 19.1 degrees +/- 6.6 degrees in the LCL/MCL-deficient joint compared with the mean extension of the intact joint, which was 10.5 degrees +/- 4.2 degrees. After application of the fixator, valgus displacement was significantly decreased by 4.0 degrees +/- 3.4 degrees in the LCL-deficient joint and by 3.6 degrees +/- 3.3 degrees in the LCL/MCL-deficient joint compared with the intact joint. External rotatory displacement was significantly decreased in the LCL-deficient joint by 4.9 degrees +/- 3.7 degrees and in the LCL/MCL-deficient joint by 5.0 degrees +/- 4.7 degrees. Internal rotatory displacement was significantly decreased by 3.3 degrees +/- 2.7 degrees in the LCL-deficient joint, but it was not significantly changed in the LCL/MCL-deficient joint. The Orthofix elbow external fixator guided elbow motion to a more varus position compared with the intact elbow and decreased the range of motion of the joint, constraining mainly extension. We conclude that the fixator stabilized the ligamentous unstable elbow joint efficiently but at the expense of changes in the normal motion pattern.  相似文献   
78.

Introduction

With more people receiving antiretroviral treatment (ART), the need to detect treatment failure and switch to second-line ART has also increased. We assessed CD4 cell counts (as a marker of treatment failure), determined the rate of switching to second-line treatment and evaluated mortality related to treatment failure among HIV-infected patients in Guinea-Bissau.

Methods

In this retrospective cohort study, adult patients infected with HIV-1 receiving ≥6 months of ART at an HIV clinic in Bissau were included from June 2005 to July 2014 and followed until January 2015. Treatment failure was defined as 1) a fall in CD4 count to baseline (or below) or 2) CD4 levels persistently below 100 cells/µL after ≥6 months of ART. Cox hazard models, with time since six months of ART as the time-varying coefficient, were used to estimate the hazard ratio for death and loss to follow-up.

Results

We assessed 1,591 HIV-1-infected patients for immunological treatment failure. Treatment failure could not be determined in 594 patients (37.3%) because of missing CD4 cell counts. Among the remaining 997 patients, 393 (39.4%) experienced failure. Only 39 patients (9.9%) with failure were switched from first- to second-line ART. The overall switching rate was 3.1 per 100 person-years. Mortality rate was higher in patients with than without treatment failure, with adjusted hazard rate ratios (HRRs) 10.0 (95% CI: 0.9–107.8), 7.6 (95% CI: 1.6–35.5) and 3.1 (95% CI: 1.5–6.3) in the first, second and following years, respectively. During the first year of follow-up, patients experiencing treatment failure had a higher risk of being lost to follow-up than patients not experiencing treatment failure (adjusted HRR 4.4; 95% CI: 1.7–11.8).

Conclusions

We found a high rate of treatment failure, an alarmingly high number of patients for whom treatment failure could not be assessed, and a low rate of switching to a second-line therapy. These factors could lead to an increased risk of resistance development and excess mortality.  相似文献   
79.
Background Impulsive forces in the knee joint have been suspected to be a co-factor in the development and progression of knee osteoarthritis. We thus evaluated the impulsive sagittal ground reaction forces (iGRF), shock waves and lower extremity joint kinematics at heel strike during walking in knee osteoarthritis (OA) patients and compared them to those in healthy subjects.

Subjects and methods We studied 9 OA patients and 10 healthy subjects using three-dimensional gait analyses concentrated on the heel strike. Impulse GRF (iGRF) was measured together with peak accelerations (PA) at the tibial tuberosity and sacrum. Sagittal lower extremity joint angles at heel strike were extracted from the gait analyses. As OA is painful and pain might alter movement strategies, the patient group was also evaluated following pain relief by intraarticular lidocaine injections.

Results The two groups showed similar iGRF, similar tibial and sacral PA, and similar joint angles at heel strike. Following pain relief, the OA patients struck the ground with more extended hip and knee joints and lower tibial PA compared to the painful condition. Although such changes occurred after pain relief, all parameters were within their normal ranges.

Interpretation OA patients and healthy subjects show similar impulse-forces and joint kinematics at heel strike. Following pain relief in the patient group, changes in tibial PA and in hip and knee joint angles were observed but these were still within the normal range. Our findings make us question the hypothesis that impulse-forces generated at heel strike during walking contribute to progression of OA.  相似文献   
80.
Objectives:To investigate root resorption after 6 months of active orthodontic treatment and its relation to possible risk factors.Materials and Methods:Ninety-seven patients (10–18 years) with a Class I malocclusion and crowding treated with fixed appliance and premolar extractions were examined with cone beam computed tomography before and after 6 months of active treatment. The exposure covered all teeth from first molar to first molar in both jaws. The Malmgren index was used to evaluate the degree of root resorption. Irregular root contour (score 1) was seen in most teeth already before active treatment, and therefore resorptions were registered only as score 2 (<2 mm, minor resorption) or higher.Results:Minor root resorption was noted in 10% of the patients and severe root resorption, >2 mm (score 3) was found in four patients. Root resorption was more frequently seen in the upper jaw, especially the incisors. There was no statistically significant correlation of root resorption with any of the selected risk factors.Conclusions:After 6 months of treatment, clinically significant resorption was diagnosed in 4% of the patients, ie, in 96% of the patients the radiographic examination did not reveal any significant information. The selected risk factors did not have any impact on the amount of resorption after 6 months of active treatment.  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