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   2552篇
  免费   198篇
  国内免费   3篇
耳鼻咽喉   26篇
儿科学   151篇
妇产科学   45篇
基础医学   251篇
口腔科学   55篇
临床医学   284篇
内科学   527篇
皮肤病学   29篇
神经病学   216篇
特种医学   261篇
外科学   343篇
综合类   31篇
一般理论   1篇
预防医学   193篇
眼科学   34篇
药学   143篇
中国医学   2篇
肿瘤学   161篇
  2023年   13篇
  2022年   15篇
  2021年   53篇
  2020年   36篇
  2019年   33篇
  2018年   35篇
  2017年   40篇
  2016年   33篇
  2015年   42篇
  2014年   63篇
  2013年   80篇
  2012年   104篇
  2011年   119篇
  2010年   98篇
  2009年   87篇
  2008年   93篇
  2007年   95篇
  2006年   98篇
  2005年   105篇
  2004年   110篇
  2003年   79篇
  2002年   66篇
  2001年   71篇
  2000年   99篇
  1999年   76篇
  1998年   60篇
  1997年   39篇
  1996年   49篇
  1995年   45篇
  1994年   41篇
  1993年   39篇
  1992年   51篇
  1991年   45篇
  1990年   47篇
  1989年   52篇
  1988年   58篇
  1987年   49篇
  1986年   32篇
  1985年   41篇
  1984年   38篇
  1983年   45篇
  1982年   41篇
  1981年   22篇
  1980年   26篇
  1979年   19篇
  1978年   18篇
  1977年   17篇
  1976年   23篇
  1975年   18篇
  1974年   13篇
排序方式: 共有2753条查询结果,搜索用时 471 毫秒
51.
52.
53.
A significant number of casualties in previous conflicts died from peripheral vascular wounds. A well-designed tourniquet could possibly have prevented these deaths. The objective of this study was the identification of such a tourniquet. A survey of Special Operations corpsmen established important characteristics necessary in an ideal tourniquet. Because most available devices do not and patented ideas could not meet these criteria, a number of prototypes were developed. Seven potentially satisfactory tourniquets were evaluated by 15 Navy SEAL corpsmen. The success and timing of placement were recorded, and a follow-up questionnaire was completed. Of the several successful tourniquets, two were preferred. Tourniquets incorporating a windlass technique take longer to place and often fail when placed with only one hand. New, relatively simple tourniquet devices incorporating bladder and ratchet mechanisms can significantly improve tourniquet performance.  相似文献   
54.
55.
56.
Yang  GY; Liao  J; Kim  K; Yurkow  EJ; Yang  CS 《Carcinogenesis》1998,19(4):611-616
In order to study the biological activities of tea preparations and purified tea polyphenols, their growth inhibitory effects were investigated using four human cancer cell lines. Growth inhibition was measured by [3H]thymidine incorporation after 48 h of treatment. The green tea catechins (-)-epigallocatechin-3-gallate (EGCG) and (-)- epigallocatechin (EGC) displayed strong growth inhibitory effects against lung tumor cell lines H661 and H1299, with estimated IC50 values of 22 microM, but were less effective against lung cancer cell line H441 and colon cancer cell line HT-29 with IC50 values 2- to 3- fold higher. (-)-Epicatechin-3-gallate, had lower activities, and (-)- epicatechin was even less effective. Preparations of green tea polyphenols and theaflavins had higher activities than extracts of green tea and decaffeinated green tea. The results suggest that the growth inhibitory activity of tea extracts is caused by the activities of different tea polyphenols. Exposure of H661 cells to 30 microM EGCG, EGC or theaflavins for 24 h led to the induction of apoptosis as determined by an annexin V apoptosis assay, showing apoptosis indices of 23, 26 and 8%, respectively; with 100 microM of these compounds, the apoptosis indices were 82, 76 and 78%, respectively. Incubation of H661 cells with EGCG also induced a dose-dependent formation of H2O2. Addition of H2O2 to H661 cells caused apoptosis in a manner similar to that caused by EGCG. The EGCG-induced apoptosis in H661 cells was completely inhibited by exogenously added catalase (50 units/ml). These results suggest that tea polyphenol-induced production of H2O2 may mediate apoptosis and that this may contribute to the growth inhibitory activities of tea polyphenols in vitro.   相似文献   
57.
OBJECTIVE: To review the natriuretic hormone system and discuss its diagnostic, prognostic, and therapeutic potential in critically ill children. DATA SOURCE: A thorough literature search of MEDLINE was performed using search terms including heart defects, congenital; cardiopulmonary bypass, atrial natriuretic factor; natriuretic peptide, brain; carperitide; nesiritide. Preclinical and clinical investigations and review articles were identified that describe the current understanding of the natriuretic hormone system and its role in the regulation of vascular tone and fluid balance in healthy adults and children and in those with underlying cardiac, pulmonary, and renal disease. RESULTS: A predictable activation of the natriuretic hormone system occurs in children with congenital heart disease and congestive heart failure. Further study is needed to confirm preliminary reports that measurement of natriuretic hormone levels in critically ill children provides diagnostic and prognostic information, as has been demonstrated in adult cardiac populations. Natriuretic hormone infusions provide favorable hemodynamic changes and symptomatic relief when used in adults with decompensated congestive heart failure, and uncontrolled case series suggest that similar benefits may exist in children. The biological activity of the natriuretic hormone system may be decreased following pediatric cardiopulmonary bypass, and additional studies are needed to determine whether natriuretic hormone infusions provide clinical benefit in the postoperative period. Preliminary reports suggest that natriuretic hormone infusions cause physiologic improvements in adults with acute lung injury and asthma but not in those with acute renal failure. CONCLUSIONS: Although important perturbations of the natriuretic hormone system occur in critically ill infants and children, further investigation is needed before the measurement of natriuretic peptides and the use of natriuretic hormone infusions are incorporated into routine practice.  相似文献   
58.
Experience with the holmium laser as an endoscopic lithotrite   总被引:1,自引:0,他引:1  
INTRODUCTION: Holmium laser lithotripsy represents an additional option in the management of urinary tract calculi. We report the results of a cohort of patients with ureteric and bladder calculi treated with this modality. METHODS: Twenty-three patients underwent holmium laser lithotripsy to treat ureteric or bladder calculi. Power settings of 0.5 J to deliver 2.5-4.0 watts were used for the ureteric calculi, and up to 30 watts for the bladder calculi. RESULTS: The mean ureteric stone size was 7.3 mm (range 4-10 mm). One stone was upper ureteric, seven were mid-ureter and nine were lower-ureter. Eighteen of the 19 patients with ureteric calculi were free of stones 28 days postoperatively. The remaining patient was clear by 12 weeks. All patients with bladder calculi were completely cleared of stones. There were no intraoperative complications. DISCUSSION: Ureteric stone position can limit the use of extracorporeal shock wave lithotripsy due to imaging difficulties. Ureteric lithotripsy overcomes this problem. The holmium laser has proven to be safe and effective in clearing urinary stone burdens of a variety of sizes, sites and compositions in this cohort of patients.  相似文献   
59.
BACKGROUND: The purpose of the present paper was (i) to identify trends in in-hospital mortality after transurethral resection of the prostate (TURP) in Victorian public hospitals; and (ii) to explore associations between in-hospital mortality after TURP and age, adverse events, type of admission (emergency/planned), location of the hospital (metropolitan/rural), teaching status of the hospital and length of stay. METHODS: Trends in in-hospital mortality after TURP and the associations between in-hospital mortality and the aforementioned variables were studied using International Classification of Diseases, 9th revision, Clinical Modification (ICD-9-CM) coded Victorian hospital morbidity data from public hospitals between 1987-88 and 1994-95. Crude and adjusted odds ratios (OR) and 95% confidence intervals (CI) were based on univariate and multivariate logistic regression, respectively. RESULTS: After adjustment for age, comorbidity, and other confounding variables, the trend in mortality reduction over time was highly significant (P for trend < 0.0001, 95% CI for trend: 0.84-0.95). Highly significant associations with mortality were observed for emergency admissions (OR = 1.99, P < 0.0001), presence of adverse events (OR = 2.69, P < 0.0001), length of hospital stay (P for trend < 0.0001, 95% for trend: 1.88-2.15) and age (P for trend < 0.0001; 95% CI for trend: 1.26-1.48). CONCLUSIONS: Routinely collected data from hospitals can provide tentative evidence of improved effectiveness of a surgical treatment, provided analysis takes careful account of potential sources of bias, especially those related to possible changes in case selection over time. These kinds of data should stimulate a joint effort between clinicians, quality assurance experts and epidemiologists to confirm this attribution, and to locate the causative factors.  相似文献   
60.
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