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   4046篇
  免费   206篇
  国内免费   13篇
耳鼻咽喉   86篇
儿科学   113篇
妇产科学   37篇
基础医学   557篇
口腔科学   223篇
临床医学   351篇
内科学   680篇
皮肤病学   76篇
神经病学   406篇
特种医学   172篇
外科学   578篇
综合类   10篇
一般理论   1篇
预防医学   333篇
眼科学   123篇
药学   242篇
中国医学   4篇
肿瘤学   273篇
  2024年   4篇
  2023年   34篇
  2022年   55篇
  2021年   106篇
  2020年   77篇
  2019年   90篇
  2018年   108篇
  2017年   60篇
  2016年   123篇
  2015年   105篇
  2014年   138篇
  2013年   205篇
  2012年   274篇
  2011年   264篇
  2010年   158篇
  2009年   146篇
  2008年   300篇
  2007年   278篇
  2006年   306篇
  2005年   249篇
  2004年   226篇
  2003年   232篇
  2002年   210篇
  2001年   37篇
  2000年   23篇
  1999年   33篇
  1998年   53篇
  1997年   33篇
  1996年   30篇
  1995年   30篇
  1994年   34篇
  1993年   35篇
  1992年   21篇
  1991年   13篇
  1990年   10篇
  1989年   13篇
  1988年   17篇
  1987年   9篇
  1986年   9篇
  1985年   13篇
  1984年   13篇
  1983年   14篇
  1982年   10篇
  1981年   10篇
  1980年   8篇
  1979年   12篇
  1978年   12篇
  1977年   4篇
  1975年   4篇
  1974年   4篇
排序方式: 共有4265条查询结果,搜索用时 15 毫秒
71.
In this report we present our experience of non-invasive magnetic resonance imaging (MR) angiography and selective catheter angiography in assessing the patency of bronchial artery revascularization grafts after an en bloc double-lung and heart-lung transplantation. We studied 8 patients who had undergone pulmonary transplantation with direct bronchial artery revascularization. Catheter angiography was performed 10 days to 63 months postoperatively. MR angiography was performed within 24 h of the catheter procedure and the results were compared with the findings from catheter angiography. Catheter angiography showed the bronchial revascularization graft to be patent in 6 patients and occluded in 2. At MR angiography, the patency of bronchial artery revascularization grafts was reliably identified in 7 of the 8 patients. One patient had inadequate image quality because of void artefacts caused by haemostatic clips. It is concluded that MR angiography is a reliable method for assessing the patency of bronchial artery revascularization grafts.  相似文献   
72.
The study aimed to clarify the role of direct bronchial artery revascularization (BAR) after en bloc double-lung (DLT) and heart-lung transplantation (HLT). Group I comprised eight patients with en bloc DLT or HLT and successful BAR, while group II included 14 DLT or HLT cases without BAR or with failed BAR. From these groups, 2 subgroups were extracted: group III, including 6 cases of en bloc DLT with successful BAR and group IV 10 HLT cases without or with failed BAR. Airway healing was evaluated at bronchoscopy and patency of BAR with angiography. Pulmonary viral, bacterial and fungal infections, rejections and bronchiolitis obliterans syndrome (BOS) were registered. Tracheal healing at 2 weeks and 3 months was better in group I than in group II (p = 0.003 and p = 0.05, respectively). Compared with group IV, tracheal anastomotic healing at 2 weeks was better in group III (p = 0.007) and tended to be better also after 3 months (p = 0.07). The incidence of infections, rejection or BOS did not differ between groups I and II. BAR thus improved healing of tracheal anastomosis.  相似文献   
73.
74.
75.
76.
77.
The aim of this in vitro study was to compare the load-bearing capacity of posterior four-unit fixed partial dentures (FPDs) produced with two different yttria-stabilized polycrystalline tetragonal zirconia (Y-TZP) ceramics, one being a presintered material, the other a fully sintered, hot isostatically pressed material. Additionally, as a novel approach, the influence of preliminary mechanical damage upon the fracture force of an FPD has been investigated. A total of 20 frameworks each were milled from presintered zirconia and from fully sintered zirconia. Prior to veneering, 10 frameworks of each material were 'damaged' by a defined saw cut similar to an accidental flaw generated during shape cutting. Before fracture testing, all FPDs were subjected to thermal and mechanical cycling. Additionally, scanning electron microscopy was used to investigate fracture surfaces. Statistical analysis showed that FPDs milled from fully sintered zirconia had a significantly higher fracture resistance compared with specimens made from presintered material, whereas preliminary damage did not have a significant effect. After aging, FPDs made from both materials were capable of withstanding occlusal forces reported in the literature. Therefore, both types of Y-TZP may be suitable for posterior four-unit all-ceramic FPDs, although further prolonged aging experiments and prospective clinical trials are required to prove their fitness for clinical use.  相似文献   
78.
OBJECTIVES: To validate self-reported preclinical mobility limitation concept and self-report assessment method against muscle power and walking speed, and to study the predictive validity of preclinical mobility limitation with respect to future risk of manifest mobility limitation. DESIGN: Observational prospective cohort study and cross-sectional analysis. SETTING: Research laboratory and community. PARTICIPANTS: A total of 632 community-living (age range, 75-81 y) women and men took part in the baseline assessments and 302 persons in the semi-annual interviews on mobility limitation over 2 years. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Walking speed, muscle power, and self-reported preclinical and manifest mobility limitation. Preclinical mobility limitation was defined as self-reported tiredness or modification of task performance without task difficulty. At baseline, 4 subgroups were created according to self-reported preclinical mobility limitation in any of 3 mobility tasks (walking 2 km, walking 0.5 km, climbing up stairs): no limitation, preclinical limitation, and minor and major manifest limitation. RESULTS: At baseline, participants with preclinical mobility limitation showed intermediate levels of walking speed and muscle power, compared with those with no limitation or manifest mobility limitation. Participants reporting baseline preclinical mobility limitation had 3- to 6-fold higher age- and sex-adjusted risk of progressing to major manifest mobility limitation during the 2-year follow-up compared with participants with no limitation at baseline, whereas the risk among those with minor limitation at baseline was 14- to 18-fold higher compared with those with no limitation. CONCLUSIONS: The self-report assessment tool proved to be a valid measure to capture the early signs of disability and may serve as an inexpensive tool for identifying those nondisabled persons at high risk for future disability.  相似文献   
79.
High impact loading is known to prevent some of the age-related bone loss but its effects on the density distribution of cortical bone are relatively unknown. This study examined the effects of age and habitual sprinting on tibial and fibular mid-shaft bone traits (structural, cortical radial and polar bone mineral density distributions). Data from 67 habitual male sprinters aged 19–39 and 65–84 years, and 60 non-athletic men (referents) aged 21–39 and 65–80 years are reported. Tibial and fibular mid-shaft bone traits (strength strain index SSI, cortical density CoD, and polar and radial cortical density distributions) were assessed with peripheral quantitative computed tomography. Analysis of covariance (ANCOVA) adjusted for height and body mass indicated that the sprinters had 21 % greater tibial SSI (P < 0.001) compared to the referents, with no group × age-group interaction (P = 0.54). At the fibula no group difference or group × age-group interaction was identified (P = 0.12–0.81). For tibial radial density distribution ANCOVA indicated no group × radial division (P = 0.50) or group × age-group × division interaction (P = 0.63), whereas an age × radial division interaction was observed (P < 0.001). For polar density distribution, no age-group × polar sector (P = 0.21), group × polar sector (P = 0.46), or group × age-group × polar sector interactions were detected (P = 0.15). Habitual sprint training appears to maintain tibial bone strength, but not radial cortical density distribution into older age. Fibular bone strength appeared unaffected by habitual sprinting.  相似文献   
80.
Three human protoparvoviruses, bufavirus (BuV), tusavirus (TuV) and cutavirus (CuV), have recently been discovered in diarrheal stool. BuV has been associated with diarrhea and CuV with cutaneous T-cell lymphoma, but there are hardly any data for TuV or CuV in stool or respiratory samples. Hence, using qPCR and IgG enzyme immunoassays, we analyzed 1072 stool, 316 respiratory and 445 serum or plasma samples from 1098 patients with and without gastroenteritis (GE) or respiratory-tract infections (RTI) from Finland, Latvia and Malawi. The overall CuV-DNA prevalences in stool samples ranged between 0–6.1% among our six patient cohorts. In Finland, CuV DNA was significantly more prevalent in GE patients above rather than below 60 years of age (5.1% vs 0.2%). CuV DNA was more prevalent in stools among Latvian and Malawian children compared with Finnish children. In 10/11 CuV DNA-positive adults and 4/6 CuV DNA-positive children with GE, no known causal pathogens were detected. Interestingly, for the first time, CuV DNA was observed in two nasopharyngeal aspirates from children with RTI and the rare TuV in diarrheal stools of two adults. Our results provide new insights on the occurrence of human protoparvoviruses in GE and RTI in different countries.  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