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   21855篇
  免费   1464篇
  国内免费   114篇
耳鼻咽喉   316篇
儿科学   478篇
妇产科学   437篇
基础医学   2806篇
口腔科学   621篇
临床医学   1861篇
内科学   5431篇
皮肤病学   456篇
神经病学   1915篇
特种医学   539篇
外科学   3630篇
综合类   169篇
一般理论   8篇
预防医学   1351篇
眼科学   657篇
药学   1234篇
  1篇
中国医学   43篇
肿瘤学   1480篇
  2023年   152篇
  2022年   308篇
  2021年   712篇
  2020年   378篇
  2019年   631篇
  2018年   765篇
  2017年   445篇
  2016年   500篇
  2015年   635篇
  2014年   847篇
  2013年   1072篇
  2012年   1773篇
  2011年   1818篇
  2010年   975篇
  2009年   891篇
  2008年   1453篇
  2007年   1505篇
  2006年   1364篇
  2005年   1235篇
  2004年   1102篇
  2003年   932篇
  2002年   885篇
  2001年   171篇
  2000年   142篇
  1999年   215篇
  1998年   218篇
  1997年   152篇
  1996年   147篇
  1995年   159篇
  1994年   130篇
  1993年   131篇
  1992年   148篇
  1991年   108篇
  1990年   90篇
  1989年   97篇
  1988年   91篇
  1987年   80篇
  1986年   77篇
  1985年   58篇
  1984年   69篇
  1983年   69篇
  1982年   77篇
  1981年   61篇
  1980年   53篇
  1979年   67篇
  1978年   45篇
  1977年   43篇
  1976年   39篇
  1974年   36篇
  1973年   32篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
961.
962.
963.
OBJECTIVE: The objectives of our study were to investigate differences in Doppler sonography features between benign and malignant breast lesions and between malignant lesions with different prognostic factors and to propose diagnostic criteria for Doppler sonography of breast lesions. SUBJECTS AND METHODS: We performed power and duplex Doppler sonography examinations in 826 breast lesions scheduled for sonographically guided core needle biopsy. Lesion vascularity, pulsatility index (PI), and resistive index (RI) of the vessels detected were analyzed and correlated with histologic results. RESULTS: Color flow was more frequently seen in malignant (237/348 lesions, 68%) than in benign (171/478, 36%) lesions (p < 0.001). However, sensitivity, specificity, and positive and negative predictive values for this sign were low (68%, 64%, 58%, and 73%, respectively). The RI and PI values were significantly higher (p < 0.001) in cancers. Although an overlap in these values between benign and malignant lesions was observed, all but one nodule with an RI of greater than 0.99 (those with null or inverted diastolic flow) or a PI of greater than 4 were malignant. No significant relationship was found between PI, RI, or flow visualization on power Doppler sonography and tumor grade or lymph node involvement in cancers. CONCLUSION: Flow visualization on power Doppler sonography indicates a higher possibility of malignancy but is not useful as the main sign for malignancy. However, any lesion with a vessel that has an RI value greater than 0.99 or a PI value greater than 4 within it must be considered as probably malignant regardless of any other sonography sign present. Doppler findings are not useful to predict tumor grade or lymph node involvement.  相似文献   
964.

Objectives

Research investigating the longitudinal effects of the most popular sports on bone development in adolescent males is scarce. The aim is to investigate the effect of 12-month participation in osteogenic and non-osteogenic sports on bone development.

Design

A 12-month study was conducted in adolescent males involved in football, swimming and cycling and compared with an active control group.

Methods

116 adolescent males (13.1 ± 0.1 years at baseline): 37 footballers, 37 swimmers, 28 cyclists and 14 active controls were followed for 12 months. Bone mineral content (BMC) was measured by dual-energy X-ray absorptiometry, and bone stiffness was measured by quantitative ultrasound. Bone outcomes at 12 months were adjusted for baseline bone status, age, height, lean mass and moderate to vigorous physical activity.

Results

Footballers had higher improvement in adjusted BMC at the total body, total hip, shaft, Ward’s triangle, legs and bone stiffness compared to cyclists (6.3–8.0%). Footballers had significantly higher adjusted BMC at total body, shaft and legs compared to swimmers (5.4–5.6%). There was no significant difference between swimmers and cyclists for any bone outcomes. Swimming and cycling participation resulted in non-significant lower bone development at most sites of the skeleton compared to controls (?4.3 to ?0.6%).

Conclusions

Football participation induces significantly greater improvements in BMC and bone stiffness over 12 months compared to cycling and swimming.

Clinical trial registration

ISRCTN17982776.  相似文献   
965.
OBJECTIVES: The objectives were to assess the prevalence of high-risk HPV in the male sexual partners of women with HPV-induced lesions, and correlate it with biopsies guided by peniscopy. STUDY DESIGN: Fifty-four asymptomatic male sexual partners of women with low-grade squamous intra-epithelial lesions (LSIL) associated with high-risk HPV were examined between April 2003 and June 2005. The DNA-HPV was tested using a second-generation hybrid capture technique in scraped penile samples. Peniscopy identified acetowhite lesions leading to biopsy. RESULTS: High-risk HPV was present in 25.9% (14 out of 54) of the cases. Peniscopy led to 13 biopsies (24.07%), which resulted in two cases of condyloma, two cases of intra-epithelial neoplasia (PIN) I, one case of PIN II, and eight cases of normal tissue. The high-risk HPV test demonstrated 80% sensitivity, 100% specificity, 100% positive predictive value, and 88.9% negative predictive value for the identification of penile lesions. There was a greater chance of finding HPV lesions in the biopsy in the positive cases of high-risk HPV with abnormal peniscopy (p=0.007); OR=51 (CI 1.7-1527.1). CONCLUSION: Among asymptomatic male sexual partners of women with low-grade intra-epithelial squamous lesions, those infected by high-risk HPV have a higher chance of having abnormal penile tissue compared with male partners without that infection.  相似文献   
966.
967.
968.
969.
970.
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