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   898648篇
  免费   63531篇
  国内免费   2327篇
耳鼻咽喉   12474篇
儿科学   28683篇
妇产科学   26143篇
基础医学   126611篇
口腔科学   24683篇
临床医学   74773篇
内科学   183177篇
皮肤病学   18985篇
神经病学   71408篇
特种医学   36459篇
外国民族医学   336篇
外科学   142137篇
综合类   19029篇
一般理论   247篇
预防医学   64565篇
眼科学   20084篇
药学   63812篇
中国医学   1798篇
肿瘤学   49102篇
  2018年   9049篇
  2017年   7161篇
  2016年   7675篇
  2015年   8730篇
  2014年   12370篇
  2013年   19211篇
  2012年   25664篇
  2011年   27262篇
  2010年   16581篇
  2009年   15784篇
  2008年   26129篇
  2007年   27740篇
  2006年   27923篇
  2005年   27453篇
  2004年   26297篇
  2003年   25475篇
  2002年   25074篇
  2001年   41362篇
  2000年   42556篇
  1999年   36270篇
  1998年   9967篇
  1997年   9149篇
  1996年   9084篇
  1995年   8446篇
  1994年   8081篇
  1993年   7586篇
  1992年   28204篇
  1991年   26979篇
  1990年   26411篇
  1989年   25346篇
  1988年   23553篇
  1987年   23172篇
  1986年   22250篇
  1985年   21153篇
  1984年   15807篇
  1983年   13477篇
  1982年   8087篇
  1979年   14591篇
  1978年   10208篇
  1977年   8627篇
  1976年   8147篇
  1975年   8960篇
  1974年   10700篇
  1973年   10183篇
  1972年   9663篇
  1971年   8917篇
  1970年   8585篇
  1969年   8025篇
  1968年   7684篇
  1967年   7086篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
The aim of this study was to evaluate learners’ acceptance of a webinar for continuing medical education that was instigated by the International Association of Oral and Maxillofacial Surgeons (IAOMS). A live, interactive webinar on orthognathic surgery was broadcast via the Internet. The learners’ acceptance of the webinar was evaluated using a standardized, validated questionnaire (Student Evaluation of Educational Quality, SEEQ). One hundred and fifty-three participants attended the webinar; 55 participants (46 male, nine female) completed the questionnaire. The mean age of the respondents was 41.6 ± 10.0 years. The age of male and female respondents did not differ significantly. The respondents were spread over five continents, with the highest number from Brazil. The SEEQ showed a high level of acceptance for almost all subscales. There was no statistically significant difference between male and female respondents concerning acceptance of the webinar (P = 0.614). The wide distribution of participants shows the potential for webinars as facilitators of barrier-free distribution of knowledge. The webinar was well accepted by the attendees independent of sex, specialty, and work experience. However, the sex ratio reflects the underrepresentation of women in oral and maxillofacial surgery.  相似文献   
152.
The current coronavirus disease (COVID‐19) outbreak, caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), has raised the possibility of potential neurotropic properties of this virus. Indeed, neurological sequelae of SARS‐CoV‐2 infection have already been reported and highlight the relevance of considering the neurological impact of coronavirus (CoV) from a translational perspective. Animal models of SARS and Middle East respiratory syndrome, caused by structurally similar CoVs during the 2002 and 2012 epidemics, have provided valuable data on nervous system involvement by CoVs and the potential for central nervous system spread of SARS‐CoV‐2. One key finding that may unify these pathogens is that all require angiotensin‐converting enzyme 2 as a cell entry receptor. The CoV spike glycoprotein, by which SARS‐CoV‐2 binds to cell membranes, binds angiotensin‐converting enzyme 2 with a higher affinity compared with SARS‐CoV. The expression of this receptor in neurons and endothelial cells hints that SARS‐CoV‐2 may have higher neuroinvasive potential compared with previous CoVs. However, it remains to be determined how such invasiveness might contribute to respiratory failure or cause direct neurological damage. Both direct and indirect mechanisms may be of relevance. Clinical heterogeneity potentially driven by differential host immune‐mediated responses will require extensive investigation. Development of disease models to anticipate emerging neurological complications and to explore mechanisms of direct or immune‐mediated pathogenicity in the short and medium term is therefore of great importance. In this brief review, we describe the current knowledge from models of previous CoV infections and discuss their potential relevance to COVID‐19.  相似文献   
153.
ABSTRACT

Forensic DNA analysis is dependent on comparing the known and the unknown. Expand the number of known profiles, and the likelihood of a successful match increases. Forensic use of DNA is moving towards comparing samples of unknown origin with publicly available genetic data, such as the records held by genetic genealogy providers. Use of forensic genetic genealogy has yielded a number of recent high-profile successes but has raised ethical and privacy concerns. Navigating family trees is complex, even more so when combined with a comparison of genetic relationships. This intelligence-gathering process has led to occasional false leads, and its use also risks a public backlash, similar to concerns over Cambridge Analytica. A cautious approach to use of this technique is therefore warranted.  相似文献   
154.
According to the current nutritional recommendations issued by professional diabetes and nutrition associations, diabetic patients should keep to a diet consisting of 45–60% carbohydrates, 10–20% protein, and not more than 35% fat. However, not all of these nutritional recommendations are evidence based. For example, current studies show that the intake of insoluble roughage may be underrepresented. It is also possible that diabetic patients could benefit from keeping to the lower end of the recommended range for carbohydrates (45%) and the upper end of the range advised for protein (20%).  相似文献   
155.
Cytogenetic abnormalities are observed in approximately two‐thirds of patients with acute myeloid leukemia (AML). Chromosome rearrangements are associated with specific subtypes of AML and associated prognosis. We report a patient with AML, M2, who was primarily refractory to standard induction chemotherapy with idarubicin and cytarabine. Flow cytometry of a bone marrow aspirate showed aberrant expression of B‐cell markers including CD19. Cytogenetic studies disclosed a translocation between 5q35 and 11q13. Fluorescence in situ hybridization analyses demonstrated that neither the NSD1 nor MLL genes were involved in this case. Further study is required to define conclusively the genes involved and their contribution to pathogenesis in this case.  相似文献   
156.
157.
We have carried out a prospective randomised, single blind clinical trial to investigate the effect of continuous passive motion on range of knee flexion, lack of extension, pain levels and analgesic use after total knee replacement surgery. 85 subjects were randomly allocated to control or study group. All subjects followed the existing rehabilitation protocol, which permits immediate active range of motion exercises and mobilisation with the study group using continuous passive motion for 1 h, twice a day. Outcome measures employed were range of motion, pain assessed on a visual analogue scale and analgesic use according to the WHO ladder. Blinded evaluation was carried out preoperatively, at time of discharge from hospital, 6 weeks, 6 and 12 months postoperation. No significant difference was observed between groups at all time intervals for each outcome variable using Wilcoxon Rank sum tests. The results substantiate previous findings that short duration continuous passive motion following total knee arthroplasty does not influence outcome of range of motion or reported pain.  相似文献   
158.
BACKGROUND: The laparoscopic resection of rectal cancer shows morbidity and oncological safety comparable to the open approach, but morbidity increases after conversion to open resection. No oncological long-term results are available for the latter patients. METHODS: From 01/01/2000-31/12/2002, patients with curatively resected rectal cancer enrolled in a observational study were evaluated for morbidity, mortality, tumor- and local recurrence rate, paying attention to patients with conversion from laparoscopic to open resection. RESULTS: 237 (3.3%) of 7,189 patients underwent laparoscopic resection (ITT). These patients showed significantly more T1/2 tumors (P<0.001) in earlier UICC stages (P<0.001) than open resected patients. 35 (14.8%) of 237 laparoscopic procedures were converted. Compared with patients receiving complete laparoscopic or open resection, these patients showed significantly higher frequencies of intraoperative (P<0.001) and general postoperative complications (P=0.003) as well as the highest overall morbidity (P=0.031). After a median follow-up of 30.1 months, the highest 5-year local recurrence rate was found in the converted group (16.0%). The laparoscopically resected patients showed a local recurrence rate of 3.3%, patients with open resection of 12.4% (P=0.082). The disease-free survival rate did not differ between the groups (P=0.585). CONCLUSION: Laparoscopic resection of rectal cancer provides oncological results similar to open resection. After conversion, the short and oncological long-term outcomes were worse. Considering a conversion rate of 15%, only a strict indication for the laparoscopic approach can be allowed, and laparoscopic resection should be performed at centers.  相似文献   
159.
160.
Chronic obstructive pulmonary disease (COPD) is characterised by a local pulmonary inflammatory response to respiratory pollutants and by systemic inflammation. Tumour necrosis factor (TNF)-alpha has been implicated in systemic effects of COPD and operates by binding the p55 (R1) and p75 (R2) TNF-alpha receptors. To investigate the contribution of each TNF-alpha receptor in the pathogenesis of COPD, the present study examined the effects of chronic air or cigarette smoke (CS) exposure in TNF-alpha R1 knockout (KO) mice, TNF-alpha R2 KO mice and wild type (WT) mice. CS was found to significantly increase the protein levels of soluble TNF-alpha R1 (by four-fold) and TNF-alpha R2 (by 10-fold) in the bronchoalveolar lavage of WT mice. After 3 months, CS induced a prominent pulmonary inflammatory cell influx in WT and TNF-alpha R1 KO mice. In TNF-alpha R2 KO mice, CS-induced pulmonary inflammation was clearly attenuated. After 6 months, no emphysema was observed in CS-exposed TNF-alpha R2 KO mice in contrast to WT and TNF-alpha R1 KO mice. CS-exposed WT and TNF-alpha R1 KO mice failed to gain weight, whereas the body mass of TNF-alpha R2 KO mice was not affected. These current findings suggest that both tumour necrosis factor-alpha receptors contribute to the pathogenesis of chronic obstructive pulmonary disease, but tumour necrosis factor-alpha receptor-2 is the most active receptor in the development of inflammation, emphysema and systemic weight loss in this murine model of chronic obstructive pulmonary disease.  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