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   8952篇
  免费   608篇
  国内免费   58篇
耳鼻咽喉   98篇
儿科学   268篇
妇产科学   254篇
基础医学   1140篇
口腔科学   470篇
临床医学   718篇
内科学   2028篇
皮肤病学   196篇
神经病学   1027篇
特种医学   172篇
外科学   974篇
综合类   41篇
一般理论   2篇
预防医学   929篇
眼科学   78篇
药学   648篇
中国医学   22篇
肿瘤学   553篇
  2024年   18篇
  2023年   110篇
  2022年   229篇
  2021年   376篇
  2020年   209篇
  2019年   304篇
  2018年   349篇
  2017年   243篇
  2016年   273篇
  2015年   304篇
  2014年   382篇
  2013年   484篇
  2012年   742篇
  2011年   714篇
  2010年   352篇
  2009年   305篇
  2008年   521篇
  2007年   536篇
  2006年   461篇
  2005年   467篇
  2004年   337篇
  2003年   327篇
  2002年   315篇
  2001年   154篇
  2000年   129篇
  1999年   107篇
  1998年   46篇
  1997年   46篇
  1996年   46篇
  1995年   38篇
  1994年   23篇
  1993年   16篇
  1992年   68篇
  1991年   71篇
  1990年   62篇
  1989年   39篇
  1988年   37篇
  1987年   40篇
  1986年   31篇
  1985年   37篇
  1984年   26篇
  1983年   39篇
  1982年   22篇
  1981年   14篇
  1979年   14篇
  1978年   13篇
  1974年   12篇
  1973年   13篇
  1972年   13篇
  1970年   15篇
排序方式: 共有9618条查询结果,搜索用时 15 毫秒
61.
The determinants that underlie a healthy or unhealthy pregnancy are complex and not well understood. We assess the relationship between the built environment and maternal psychosocial status using directly observed residential neighborhood characteristics (housing damage, property disorder, tenure status, vacancy, security measures, violent crime, and nuisances) and a wide range of psychosocial attributes (interpersonal support evaluation list, self-efficacy, John Henryism active coping, negative partner support, Perceived Stress Scale, perceived racism, Center for Epidemiologic Studies—Depression) on a pregnant cohort of women living in the urban core of Durham, NC, USA. We found some associations between built environment characteristic and psychosocial health varied by exposure categorization approach, while others (residence in environments with more rental property is associated with higher reported active coping and negative partner support) were consistent across exposure categorizations. This study outlines specific neighborhood characteristics that are modifiable risk markers and therefore important targets for increased research and public health intervention.  相似文献   
62.
OBJECTIVE: To investigate the spatial distribution of the magnitude and direction of the current density in the human head during transcranial direct current stimulation (tDCS). METHODS: The current density distribution was calculated using a numerical method to implement a standard spherical head model into which current was injected by means of large electrodes. The model was positioned in 'MNI space' to facilitate the interpretation of spatial coordinates. RESULTS: The magnitude and direction of the current density vector are illustrated in selected brain slices for four different electrode montages. Approximately half of the current injected during tDCS is shunted through the scalp, depending on electrode dimension and position. Using stimulating currents of 2.0 mA, the magnitude of the current density in relevant regions of the brain is of the order of 0.1 A/m2, corresponding to an electric field of 0.22 V/m. CONCLUSIONS: Calculations based on a spherical model of the head can provide useful information about the magnitude and direction of the current density vector in the brain during tDCS, taking into account the geometry and position of the electrodes. Despite the inherent limitations of the spherical head model, the calculated values are comparable to those used in the most recent in vitro studies on modulation of neuronal activity. SIGNIFICANCE: The methodology presented in this paper may be used to assess the current distribution during tDCS using new electrode montages, to help optimize montages that target a specific region of the brain or to preliminarily investigate compliance with safety guidelines.  相似文献   
63.

Background  

Laparoscopic Roux-en-Y gastric bypass (LRYGB) is currently the gold standard bariatric procedure for the treatment of morbid obesity. Laparoscopic sleeve gastrectomy (LSG) is a relatively innovative procedure which has been increasingly applied lately as a sole bariatric procedure. A randomized trial was conducted in a Greek population to evaluate perioperative safety and 3-years results.  相似文献   
64.
Transcatheter aortic valve implantation by an apical approach has been developed as an alternative to conventional aortic valve replacement. Complications with these relatively new procedures are being reported. We report a case of transapical transcatheter aortic valve implantation, in which a pseudoaneurysm at the apex of the left ventricle as a complication of the procedure developed in the patient and was treated without surgery. The defect spontaneously closed.  相似文献   
65.
BACKGROUND AND OBJECTIVE: To optimize laser therapy of port-wine stains (PWSs), information about the vasculature as well as lesion depth is valuable. In this study we investigated the use of photoacoustic imaging (PAI) to obtain this information. STUDY DESIGN/MATERIALS AND METHODS: PAI uses pulsed light to generate ultrasound upon absorption of short light pulses by blood. In this study we used PAI to image vasculature in PWSs in three human volunteers. Two-dimensional imaging (scan direction vs. depth) was carried out by scanning a double-ring photoacoustic sensor over the tissue surface. RESULTS: In the photoacoustic images we observed an increased photoacoustic signal intensity at the locations of the PWS that is associated with increased vascularization. From the obtained images we measured the thickness of the vascular layer and estimated lesion depth. In some cases single vessels could be observed at the position of the PWS whereas in other cases the PWS appeared as a region with large photoacoustic signal intensity. CONCLUSIONS: PAI has the potential to reveal information about the lesion depth as well as thickness of the vascular layer.  相似文献   
66.
OBJECT: With the recent development and refinement of endovascular stents, the significant potential for these devices in the treatment of wide-necked dissecting and fusiform aneurysms has become apparent. In this article the authors report on the use of stents and coils to treat dissecting and fusiform vertebral artery (VA) aneurysms. METHODS: Eight consecutive patients harboring eight dissecting aneurysms and one fusiform aneurysm of the VA were succesfully treated using a procedure in which the authors inserted an intravascular stent and secondary endosaccular coils when needed. In all but one patient complete aneurysm occlusion was achieved, and in all cases there was no neurological complication. Follow-up angiography examinations were performed in all patients (mean duration of follow-up angiography review 13.1 months, range 3-42 months). The patients remained stable throughout the clinical follow-up period (mean 14.1 months, range 4-42 months). No rebleeding was recorded. CONCLUSIONS: At present this combined approach represents a reliable and safe alternative for the treatment of VA dissecting aneurysms, especially in patients who cannot tolerate occlusion tests.  相似文献   
67.
68.
Genetic variation, C-reactive protein levels, and incidence of diabetes   总被引:7,自引:0,他引:7  
C-reactive protein (CRP) has been shown to be associated with type 2 diabetes, but whether CRP has a causal role is not yet clear. We examined the association in the Rotterdam Study, a population-based prospective cohort study. The association of baseline serum CRP and incident diabetes during follow-up was investigated, and a meta-analysis was conducted on the BMI-adjusted relation of CRP and diabetes. Furthermore, the association of CRP haplotypes with serum CRP and risk of diabetes was assessed. The age- and sex-adjusted hazard ratio for diabetes was 1.41 (95% CI 1.29-1.54) per 1 SD increase in natural logarithm of CRP, and it was 1.88, 2.16, and 2.83 for the second, third, and fourth quartiles of CRP, respectively, compared with the first quartile. The risk estimates attenuated but remained statistically significant after additional adjustment for obesity indexes, which agreed with the results of the meta-analysis. The most common genetic haplotype was associated with a significantly lower CRP level compared with the three other haplotypes. The risk of diabetes was significantly higher in the haplotype with the highest serum CRP level compared with the most common haplotype (OR 1.45, 95% CI 1.08-1.96). These findings support the hypothesis that serum CRP enhances the development of diabetes.  相似文献   
69.
Background It has been suggested that obesity is associated with an altered rate of gastric emptying. The objective of the present study was to determine whether the rates of solid and semi-solid gastric emptying differ between morbidly obese patients and lean subjects. Methods The Gastric-emptying time (GET) of solid and semi-solid meals were compared between lean healthy subjects and morbidly obese patients enrolled in two previously published studies. GET of solid and semi-solid meals was measured using the 13C-octanoic acid breath test and 13C-acetic acid breath test, respectively, in 24 lean and 14 morbidly obese individuals of both sexes. Student t-test was used to compare the mean data between the lean and morbidly obese groups. The influence of sex, gender, BMI and morbid obesity on the GET of solid meals was verified by linear regression analysis. Results Mean t(1/2) values of solid GET (± standard deviation) were 203.6 ±  76.0 min and 143.5 ± 19.1 min for lean and obese subjects, respectively (P = 0.0010). Mean t(lag) values of solid GET were 127.3 ± 42.7 min and 98.4 ± 13.0 min for lean and obese subjects, respectively (P = 0.0044). No significant difference in semi-solid GET was observed between the lean and morbidly obese groups. Conclusion The present study demonstrated a significantly enhanced gastric emptying of the solid meal test in morbidly obese patients when compared to lean subjects. This finding is compatible with the hypothesis that rapid gastric emptying in morbidly obese subjects increases caloric intake due to a more rapid loss of satiety.  相似文献   
70.
AIM: The aim of the study is to compare the results obtained using two different techniques of reconstruction after pancreaticoduodenectomy: pancreaticojejunostomy and pancreatic remnant duct occlusion. METHODS: The authors describe a retrospective study performed in 44 nonselected patients submitted to pancreaticoduodenectomy from 2000 to 2004. They have been divided into 2 groups. Patient characteristics were comparable in both groups. The first group (22 patients) received pancreaticojejunostomy. The second group (22 patients) received duct occlusion with sclerosing glue. Intraoperative finding (operative time, estimated blood loss) and postoperative morbidity and mortality were evaluated. Endocrine and exocrine function were analyzed at 3 and 12 months after surgery. RESULTS: Results showed no differences in median blood loss, duration operation and hospital day. Morbidity and mortality were higher in duct occlusion group; pancreatic fistula was more frequent after duct occlusion, but less dangerous than one from pancreaticojejeunostomy. Also exocrine function was better in anastomosis group and the incidence of diabetes mellitus was higher in patients with duct occlusion. CONCLUSION: Pacreaticojejunostomy is the procedure of choice, while duct occlusion should be performed in friable stump with small pancreatic duct (higher risk of pancreatic fistula).  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