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   63458篇
  免费   4599篇
  国内免费   1307篇
耳鼻咽喉   1014篇
儿科学   2212篇
妇产科学   983篇
基础医学   7415篇
口腔科学   1030篇
临床医学   4862篇
内科学   11148篇
皮肤病学   1071篇
神经病学   14578篇
特种医学   1544篇
外国民族医学   10篇
外科学   5586篇
综合类   3685篇
现状与发展   3篇
一般理论   6篇
预防医学   3605篇
眼科学   1287篇
药学   4768篇
  20篇
中国医学   2228篇
肿瘤学   2309篇
  2023年   1244篇
  2022年   1679篇
  2021年   3283篇
  2020年   3138篇
  2019年   4037篇
  2018年   3821篇
  2017年   3036篇
  2016年   2321篇
  2015年   2265篇
  2014年   4828篇
  2013年   6282篇
  2012年   3939篇
  2011年   3757篇
  2010年   2869篇
  2009年   2661篇
  2008年   2489篇
  2007年   1986篇
  2006年   1618篇
  2005年   1324篇
  2004年   1370篇
  2003年   1171篇
  2002年   904篇
  2001年   742篇
  2000年   724篇
  1999年   549篇
  1998年   351篇
  1997年   359篇
  1996年   246篇
  1995年   285篇
  1994年   282篇
  1993年   255篇
  1992年   187篇
  1991年   185篇
  1990年   160篇
  1989年   136篇
  1988年   107篇
  1987年   95篇
  1985年   610篇
  1984年   649篇
  1983年   416篇
  1982年   495篇
  1981年   434篇
  1980年   341篇
  1979年   331篇
  1978年   276篇
  1977年   215篇
  1976年   207篇
  1975年   233篇
  1974年   168篇
  1973年   174篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
《Cancer radiothérapie》2022,26(3):502-516
The aim of the review was to present the current literature status about replanning regarding anatomical and dosimetric changes in the target and OARs in the head and neck region during radiotherapy, to discuss and to analyze factors influencing the decision for adaptive radiotherapy of head and neck cancer patients. Significant progress has been made in head and neck patients’ evaluation and qualification for adapted radiotherapy over the past ten years. Many factors leading to anatomical and dosimetric changes during treatment have been identified. Based on the literature, the most common factors triggering re-plan are weight loss, tumor and nodal changes, and parotid glands shrinkage. The fluctuations in dose distribution in the clinical area are significant predictive factors for patients’ quality of life and the possibility of recovery. It has been shown that re-planning influence clinical outcomes: local control, disease free survival and overall survival. Regarding literature studies, it seems that adaptive radiotherapy would be the most beneficial for tumors of immense volume or those in the nearest proximity of the OARs. All researchers agree that the timing of re-planning is a crucial challenge, and there are still no clear consensus guidelines for time or criteria of re-planning. Nowadays, thanks to significant technological progress, the decision is mostly made based on observation and supported with IGRT verification. Although further research is still needed, adaptive strategies are evolving and now became the state of the art of modern radiotherapy.  相似文献   
2.
3.
ObjectivePrevious epidemiologic studies have suggested an association between appendectomy and Parkinson's disease. The aim of the current study was to examine the risk of Alzheimer's disease (AD) and other types of dementia following appendicitis or appendectomy for appendicitis.DesignPopulation-based cohort study.Setting and participantsWe used claims data from the Taiwan National Health Insurance Research Database. Participants aged ≥45 years with acute appendicitis or who received appendectomy for appendicitis were enrolled and followed up for more than 15 years. Cases and controls underwent 1:1 matching by age, sex, index date, and dementia-related comorbidities.MethodsThe primary outcome was AD, and secondary outcomes included other dementia types. Adjusted hazard ratios (aHRs) were calculated, and a competing risk regression model was created. The E value for causality of evidence was calculated.ResultsPatients developing appendicitis (0.6% vs 0.1%, P = .005) and those receiving appendectomy for appendicitis (0.4% vs 0.1%, P = .003) had higher incidences of AD than the controls during the follow-up period. A Cox regression analysis with adjustment for potential confounders showed that patients with appendicitis [aHR 6.68, 95% confidence interval (CI) 1.84-24.48] and those receiving appendectomy for appendicitis (aHR 5.01, 95% CI 1.33-18.85) were more likely to develop AD than the controls. These 2 groups also had higher risks for unspecified dementia and all types of dementia but not for vascular dementia than the controls. The age at dementia diagnosis was 88.51 years in the controls; however, among people who developed dementia following appendicitis, the mean age at diagnosis was 70.18 years, and dementia occurred 5.84 years after appendicitis. The competing risk regression models and the E values support the study findings.Conclusions and implicationsAfter recovery from appendicitis, these patients should be followed up for signs of AD.  相似文献   
4.
The objective of the present study was the development and validation of the method for determining AMB-FUBINACA and its metabolite - AMB-FUBINACA O-desmethyl acid – in blood samples, followed by verification of the method in toxicological judicial and forensic medicine practice employing the example of post-aggression suicide. Most likely in consequence of development of adverse effects resulting in psychotic symptoms, a male being under the influence of the synthetic cannabinoid AMB-FUBINACA and the new synthetic opioid U-47700, mortally wounded his female partner and subsequently committed suicide. Identification and determination of the afore-mentioned xenobiotics in blood samples collected from the male and female victims were performed employing high performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS). The analytes were isolated from blood samples using the solid phase extraction (SPE) method. The blood samples collected from the male and female demonstrated respectively 110 and 196 ng/mL of AMB-FUBINACA O-desmethyl acid metabolite, 1935 and 357 ng/mL of U-47700, 250 and 200 ng/mL of N-desmethyl-U-47700, as well as 410 and 200 ng/mL of N,N-didesmethyl-U-47700. The concentration values of new psychoactive substances (NPS’s) in blood samples originating from the male and female were within the ranges encountered in cases of poisoning, including these resulting in death. Nevertheless, the evident signs of exsanguination proof that the woman was alive when she sustained lethal injuries. The presented cases illustrate the difficult to be anticipated effect exerted on the users by NPS’s.  相似文献   
5.
6.
7.
8.
9.
《Saudi Dental Journal》2022,34(7):596-603
ObjectiveStudies have shown that gingival crevices may be a significant route for SARS-CoV-2 entry. However, the role of oral health in the acquisition and severity of COVID-19 is not known.DesignA retrospective analysis was performed using electronic health record data from a large urban academic medical center between 12/1/2019 and 8/24/2020. A total of 387 COVID-19 positive cases were identified and matched 1:1 by age, sex, and race to 387 controls without COVID-19 diagnoses. Demographics, number of missing teeth and alveolar crestal height were determined from radiographs and medical/dental charts. In a subgroup of 107 cases and controls, we also examined the rate of change in alveolar crestal height. A conditional logistic regression model was utilized to assess association between alveolar crestal height and missing teeth with COVID-19 status and with hospitalization status among COVID-19 cases.ResultsIncreased alveolar bone loss, OR = 4.302 (2.510 – 7.376), fewer missing teeth, OR = 0.897 (0.835–0.965) and lack of smoking history distinguished COVID-19 cases from controls. After adjusting for time between examinations, cases with COVID-19 had greater alveolar bone loss compared to controls (0.641 ± 0.613 mm vs 0.260 ± 0.631 mm, p < 0.01.) Among cases with COVID-19, increased number of missing teeth OR = 2.1871 (1.146– 4.174) was significantly associated with hospitalization.ConclusionsAlveolar bone loss and missing teeth are positively associated with the acquisition and severity of COVID-19 disease, respectively.  相似文献   
10.
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