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   1949篇
  免费   133篇
  国内免费   22篇
耳鼻咽喉   6篇
儿科学   152篇
妇产科学   23篇
基础医学   256篇
口腔科学   47篇
临床医学   191篇
内科学   458篇
皮肤病学   25篇
神经病学   47篇
特种医学   472篇
外科学   117篇
综合类   37篇
预防医学   91篇
眼科学   17篇
药学   74篇
中国医学   3篇
肿瘤学   88篇
  2022年   5篇
  2021年   9篇
  2020年   10篇
  2019年   7篇
  2018年   18篇
  2017年   11篇
  2016年   24篇
  2015年   33篇
  2014年   36篇
  2013年   66篇
  2012年   35篇
  2011年   40篇
  2010年   74篇
  2009年   63篇
  2008年   52篇
  2007年   39篇
  2006年   49篇
  2005年   37篇
  2004年   34篇
  2003年   26篇
  2002年   30篇
  2001年   19篇
  2000年   31篇
  1999年   30篇
  1998年   137篇
  1997年   123篇
  1996年   130篇
  1995年   94篇
  1994年   78篇
  1993年   83篇
  1992年   35篇
  1991年   39篇
  1990年   24篇
  1989年   65篇
  1988年   53篇
  1987年   61篇
  1986年   52篇
  1985年   52篇
  1984年   34篇
  1983年   34篇
  1982年   35篇
  1981年   24篇
  1980年   40篇
  1979年   17篇
  1978年   16篇
  1977年   19篇
  1976年   25篇
  1975年   25篇
  1973年   5篇
  1969年   5篇
排序方式: 共有2104条查询结果,搜索用时 15 毫秒
1.
Laser-light scattering was used to observe and quantify the dynamics of human blood platelet aggregation in platelet-rich plasma (PRP). Aggregation was performed in a controlled shear environment by placing the PRP in the annular space between a rotating cylindrical rod and a stationary cylindrical tube. The instrument was capable of very sensitive continuous semi-quantitative measurements of chemically-induced microaggregation. As a demonstration of the technique, results are presented for ADP-induced aggregation at doses of 10, 1, and 0.1 microM and collagen-induced aggregation at a dose of 5 micrograms/ml, each at shear rates of 1,000 s-1 and 500 s-1. Extensive aggregation was observed in response to ADP at even the low dose of 0.1 microM, indicating a high sensitivity to microaggregates. The sensitivity of the ultimate size of the ADP-induced aggregates to ADP concentration was shear dependent. The formation of microaggregates by collagen stimulation was shown to be almost immediate, as contrasted with a 10-20 s typical lag when observed turbidometrically. Disaggregation was observed with 1 microM ADP, but this was only partial, as contrasted with the complete recovery of transmittance observed in the turbidometric technique. Electronic particle sizing and counting was employed to semiquantitatively verify the aggregate size distributions found from mathematical conversion of the laser-light scattering data.  相似文献   
2.
BACKGROUND: Our aims in the present study were to estimate the influences of pain and urinary symptoms on quality of life, and to determine which of these two variables has the most predictive power with respect to quality of life in young men with chronic prostatitis-like symptoms. METHODS: Chronic prostatitis-like symptoms were measured by the National Institutes of Health-Chronic Prostatitis Symptom Index. Of the 28,841 men aged 20 years who lived in the study community, 18,495 men (a response rate 64.1%) agreed to participate in the study. A total of 1057 men who complained of symptoms indicative of chronic prostatitis were included in the study. The influences of pain and urinary symptoms on quality of life were determined using logistic regression analysis. The receiver operating characteristic (ROC) curve was used to estimate the predictive ability of each of these variables with respect to quality of life. RESULTS: Results from multivariate analysis showed that both pain and urinary symptoms were associated with an increased likelihood of impaired quality of life, although pain contributed more to a reduced quality of life than urinary symptoms. Relative to men who experienced mild pain, men who experienced moderate pain had a 3.9-fold risk of poor quality of life (odds ratio [OR], 3.87; 95% confidence interval [CI], 2.86-5.23; P < 0.001) and those who experienced severe pain had a 15.7-fold risk of reduced quality of life (OR, 15.68; 95% CI, 6.59-37.35; P < 0.001). Moderate urinary symptoms were associated with a 1.4-fold risk of bother (OR, 1.41; 95% CI, 1.01-1.99; P < 0.001) and severe urinary symptoms were associated with 2.4-fold risk (OR, 2.39; 95% CI, 1.37-4.12; P < 0.001), relative to mild urinary symptoms. Comparison of the effects of pain and urinary symptoms showed that pain severity had the most predictive power for bother, quality of life, and quality-of-life impact. The areas under the ROC curves for bother, quality of life, and quality-of-life impact were 71.3%, 69.3% and 72.5%, respectively. CONCLUSION: Urinary symptoms and pain might be associated with an increased likelihood of impaired quality of life in young men with chronic prostatitis-like symptoms. In addition, our findings suggest that pain severity is the most influential variable for determining quality of life in this population.  相似文献   
3.
4.
5.
Evaluation of an on-line patient exposure meter in neuroradiology   总被引:1,自引:0,他引:1  
  相似文献   
6.
Pediatric knee MR imaging: pattern of injuries in the immature skeleton   总被引:3,自引:0,他引:3  
  相似文献   
7.
8.
9.
INTRODUCTION: Health care workers have long been recognized as having a high risk of work-related assault. In response to a growing threat of violence in hospitals, California implemented the Hospital Security Act (AB508) in 1993. This study compares surveys of emergency nurses before and after implementation of AB508. METHODS: In 1990, the CAL/ENA surveyed emergency departments in California to enumerate violent events and describe security programs. Using the CAL/ENA membership directory, hospitals were resurveyed in 2000 to identify changes from the original survey. Surveys were mailed to the ED nurse manager or equivalent. Survey responses were anonymous. RESULTS: Most hospitals reported fewer violent episodes after the implementation of AB508. However, 32% of hospitals reported that 5 or more verbal threats occurred monthly, and 5% reported that 5 or more violent injuries occurred monthly. Overall, hospitals reported improvements in security programs. The most notable increase was in employee training, which rose from 34% to 95.6% of reporting hospitals. However, almost a quarter of hospitals reported not having general violence prevention policies, and many believed that security personnel were inadequate. DISCUSSION: Although results reported here cannot be directly attributed to AB508, the increase in security program components suggests that hospitals are responding positively to reduce violence. The high prevalence of threats and violent events reported indicates a persistent risk of violence against health care workers.  相似文献   
10.
Inversion recovery (IR), commonly considered a pulse sequence capable of producing T1-weighted images with excellent display of normal anatomy, is versatile: The null point and peak time provide a useful, succinct summary of the properties of IR and its capacity for producing both T1- and T2-weighted images. Shortening of the inversion time (TI) and creation of a short-TI inversion-recovery (STIR) pulse sequence increases sensitivity to malignancy and other abnormalities by making the effects of prolonged T1 and T2 on signal intensity additive and by nulling the signal from fat. The authors examined over 300 patients with various malignancies and compared STIR images with T1- and T2-weighted images obtained at 0.5 T. In 43 cases, signal-difference-to-noise ratios (SD/Ns) were calculated between tumor, fat, and muscle. In general, STIR images demonstrated tumor as a conspicuously high-intensity area in a background of muted, discernible anatomic detail. The good contrast achieved with STIR sequences between tumor and fat (SD/N = 18.1) and tumor and muscle (SD/N = 12.9) consolidated into a single image the information contained separately on T1- and T2-weighted images, which facilitates efficient detection and localization of malignancy.  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