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   3487篇
  免费   249篇
  国内免费   19篇
耳鼻咽喉   21篇
儿科学   133篇
妇产科学   196篇
基础医学   419篇
口腔科学   116篇
临床医学   334篇
内科学   580篇
皮肤病学   58篇
神经病学   368篇
特种医学   277篇
外科学   352篇
综合类   54篇
一般理论   4篇
预防医学   339篇
眼科学   31篇
药学   244篇
中国医学   2篇
肿瘤学   227篇
  2021年   37篇
  2020年   35篇
  2019年   57篇
  2018年   58篇
  2017年   43篇
  2016年   38篇
  2015年   57篇
  2014年   64篇
  2013年   101篇
  2012年   145篇
  2011年   129篇
  2010年   87篇
  2009年   86篇
  2008年   110篇
  2007年   149篇
  2006年   101篇
  2005年   116篇
  2004年   102篇
  2003年   95篇
  2002年   96篇
  2001年   117篇
  2000年   112篇
  1999年   100篇
  1998年   62篇
  1997年   69篇
  1996年   70篇
  1995年   37篇
  1994年   45篇
  1993年   50篇
  1992年   70篇
  1991年   75篇
  1990年   59篇
  1989年   83篇
  1988年   70篇
  1987年   79篇
  1986年   89篇
  1985年   101篇
  1984年   74篇
  1983年   61篇
  1982年   30篇
  1981年   35篇
  1980年   36篇
  1979年   43篇
  1978年   40篇
  1977年   35篇
  1976年   40篇
  1975年   38篇
  1973年   30篇
  1972年   32篇
  1969年   27篇
排序方式: 共有3755条查询结果,搜索用时 15 毫秒
101.
102.
Objective. To investigate the role of interleukin-6 (IL-6) and transforming growth factor β1 (TGF β1) in the regulation of tissue inhibitor of metalloproteinases—1 (TIMP-1) synthesis in human articular chondrocytes. Methods. Articular cartilage was obtained from human knee joints 24 hours after death. Chondrocytes were isolated by collagenase digestion and embedded in low-gelling-temperature agarose. After stimulation by cytokines, total RNA was isolated and analyzed by Northern blotting. TIMP-1 protein levels were determined using a competitive enzyme-linked immunosorbent assay. Results. Human chondrocytes in agarose culture expressed messenger RNA (mRNA) for the IL-6 receptor (gp80) and its signal-transducing subunit gp130. In contrast to the findings in a previous study, IL-6 did not stimulate TIMP-1 expression in these cells, whereas TGF β1 was an important inducer of TIMP-1 mRNA and protein synthesis. Conclusion. Our findings suggest that TGF β1 has a protective effect on the extracellular matrix of human articular chondrocytes.  相似文献   
103.
Purpose

Stereotactic radiation therapy (SRT) and immune checkpoint inhibitors (ICI) may act synergistically to improve treatment outcomes but may also increase the risk of symptomatic radiation necrosis (RN). The objective of this study was to compare outcomes for patients undergoing SRT with and without concurrent ICI.

Methods and materials

Patients treated for BMs with single or multi-fraction SRT were retrospectively reviewed. Concurrent ICI with SRT (SRT-ICI) was defined as administration within 3 months of SRT. Local control (LC), radiation necrosis (RN) risk and distant brain failure (DBF) were estimated by the Kaplan-Meier method and compared between groups using the log-rank test. Wilcoxon rank sum and Chi-square tests were used to compare covariates. Multivariate cox regression analysis (MVA) was performed.

Results

One hundred seventy-nine patients treated with SRT for 385 brain lesions were included; 36 patients with 99 lesions received SRT-ICI. Median follow up was 10.3 months (SRT alone) and 7.7 months (SRT- ICI) (p = 0.08). Lesions treated with SRT-ICI were more commonly squamous histology (17% vs 8%) melanoma (20% vs 2%) or renal cell carcinoma (8% vs 6%), (p < 0.001). Non-small cell lung cancer (NSCLC) compromised 60% of patients receiving ICI (n = 59). Lesions treated with SRT-ICI had significantly improved 1-year local control compared to SRT alone (98 and 89.5%, respectively (p = 0.0078). On subset analysis of NSCLC patients alone, ICI was also associated with improved 1 year local control (100% vs. 90.1%) (p = 0.018). On MVA, only tumor size ≤2 cm was significantly associated with LC (HR 0.38, p = 0.02), whereas the HR for concurrent ICI with SRS was 0.26 (p = 0.08). One year DBF (41% vs. 53%; p = 0.21), OS (58% vs. 56%; p = 0.79) and RN incidence (7% vs. 4%; p = 0.25) were similar for SRT alone versus SRT-ICI, for the population as a whole and those patients with NSCLC.

Conclusion

These results suggest SRT-ICI may improve local control of brain metastases and is not associated with an increased risk of symptomatic radiation necrosis in a cohort of predominantly NSCLC patients. Larger, prospective studies are necessary to validate these findings and better elucidate the impact of SRT-ICI on other disease outcomes.

  相似文献   
104.
Abstract

Introduction: Curriculum mapping shows concordances and differences between the intended and the taught curriculum. To our knowledge, no previous studies describe the effects that this mapping has on the curriculum. The aim of the present study is to map the content of a lecture series in surgery to the National Catalogue of Learning Objectives in Surgery and analyze the effects this mapping has on the content of the following lecture series.

Methods: All lecturers in the lecture series were directly observed by a minimum of two reviewers and learning objectives and the level of competence were documented. After the lecture series, the results were visualized within the catalog of learning objectives and were sent to the lecturers. In the following lecture series, learning objectives were documented correspondingly.

Results: In the first lecture series, 47% of the learning objectives were taught. After the mapping, the number of learning objectives that were taught increased to 59% (p?<?0.001). The increase was found in all surgical disciplines and in all levels of competences without any changes in the average duration of the lectures.

Conclusions: The presented method for mapping a curriculum effectively increased the number of taught learning objectives without requiring longer lecture durations.  相似文献   
105.
106.
107.
108.
Background: Critical sites within reentry circuits of postinfarction ventricular tachycardia (VT) were identified during sinus rhythm (SR) and VT to determine whether electrogram characteristics during SR may be helpful in identifying successful ablation sites. Methods: In 33 patients (mean age 67 ± 11 yrs) with prior infarction, mapping and radiofrequency (RF) catheter ablation of 57 hemodynamically-tolerated VT's (cycle length 478 ± 96) were performed. The morphologies of electrograms (EGM) at sites of concealed entrainment (CE) were compared during SR and VT. RF energy was delivered at 94 sites (51 successful and 43 unsuccessful ablation sites). Results: During SR, isolated potentials (IP), but not late potentials (LP) recorded via the mapping catheter, were associated with successful ablation. At 29/39 sites with an IP during sinus rhythm, an isolated diastolic potential (IDP) also was present during VT, whereas at 4 sites IP's were present only during SR (p < 0.001). At 11/29 sites where isolated potentials were present during SR and VT, the morphology of the isolated potential during VT and SR was similar; and all but one of these sites were successful ablation sites (p = 0.01). The EGM amplitude during VT correlated with the amplitude during SR (R = 0.9, p < 0.001). An identical pacemap was present during SR at 33/94 sites; this was not associated with successful ablation. Conclusion: SR mapping may be helpful in identifying critical sites of reentry in postinfarction VT. At sites within the reentry circuit, characteristics of sinus rhythm EGM's that are associated with successful ablation include the presence of IP's, but not the presence of LP's.  相似文献   
109.
SUMMARY: The authors describe a 69 item sexual knowledge questionnaire that covers the areas: physiology, pregnancy, the sex act, masturbation, contraception, types of sexuality, and venereal disease. There is also a ‘Belief in Myths’ scale. Mean scores for delinquent boys and young mentally handicapped adults are given, with the latter having lower scores. All areas correlate with total score. The handicapped group showed increased sexual knowledge when re-tested after a human relations course. A control group, tested after the same interval, showed only random changes. Further research is suggested.  相似文献   
110.
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