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   5787篇
  免费   628篇
  国内免费   31篇
耳鼻咽喉   51篇
儿科学   205篇
妇产科学   90篇
基础医学   920篇
口腔科学   125篇
临床医学   627篇
内科学   918篇
皮肤病学   44篇
神经病学   543篇
特种医学   504篇
外科学   1108篇
综合类   105篇
一般理论   2篇
预防医学   534篇
眼科学   116篇
药学   337篇
中国医学   3篇
肿瘤学   214篇
  2021年   70篇
  2019年   71篇
  2018年   87篇
  2017年   56篇
  2016年   56篇
  2015年   84篇
  2014年   106篇
  2013年   159篇
  2012年   190篇
  2011年   178篇
  2010年   147篇
  2009年   127篇
  2008年   190篇
  2007年   203篇
  2006年   241篇
  2005年   215篇
  2004年   191篇
  2003年   199篇
  2002年   209篇
  2001年   193篇
  2000年   170篇
  1999年   154篇
  1998年   125篇
  1997年   122篇
  1996年   131篇
  1995年   98篇
  1994年   91篇
  1993年   92篇
  1992年   141篇
  1991年   150篇
  1990年   172篇
  1989年   167篇
  1988年   164篇
  1987年   147篇
  1986年   123篇
  1985年   123篇
  1984年   85篇
  1983年   89篇
  1982年   67篇
  1981年   64篇
  1980年   48篇
  1979年   66篇
  1978年   49篇
  1977年   52篇
  1976年   58篇
  1975年   56篇
  1974年   57篇
  1971年   57篇
  1970年   51篇
  1969年   57篇
排序方式: 共有6446条查询结果,搜索用时 0 毫秒
101.
Increased lung vascular permeability leading to increased plasma protein extravasation and accumulation (PPA) is a characteristic feature of acute lung injury. Using a previously described technique, PPA was monitored in the lungs of patients with the adult respiratory distress syndrome (ARDS) — an extreme example of acute lung injury in man. An external radiation probe detector was used to monitor the pulmonary accumulation of the plasma protein transferrin radiolabelled in-vivo with 113mIn. Ten patients with ARDS exhibiting increased PPA indices (>1.0x10-3/min) were given an intravenous infusion of terbutaline (7 g/kg) over 30 min. Of the four patients in whom the post-drug PPA indices remained within the ARDS range, none survived, whilst five of the six patients in whom the post-drug PPA indices were reduced to below 1.0x10-3/min survived. PPA indices prior to the administration of terbutaline were not significantly different between the survivor (n=5) and non-survivor (n=5) groups. There was a significant decrease in the PPA indices following terbutaline in survivors (p<0.01) but not in non-survivors. Thus beta-2-agonists in therapeutic doses can inhibit increased lung vascular permeability in man. These findings may have prognostic and therapeutic implication for beta-2-agonists in ARDS.  相似文献   
102.
From January 1979 to October 1986, 86 patients with surgically resectable adenocarcinoma of the rectum or rectosigmoid were treated with adjuvant radiotherapy consisting of preoperative 2,400 cGy (22 patients), preoperative 4,000 cGy (14 patients), "sandwich" technique (27 patients), and postoperative irradiation (23 patients). Average follow-up was 42.9 months. The local recurrence rate was 4.5%, 9.1%, 7.4%, and 34.8%, respectively. The distant metastasis rate was 18.2%, 18.2%, 7.4%, and 30.4%, respectively. Preoperative radiotherapy with adequate surgical resection appears more effective in reducing the incidence of local recurrence.  相似文献   
103.
The purpose of this laboratory study was to assess the value of refractometry in identifying the contents of a variety of opioid-containing solutions. A hand-held refractometer was used to document the refraction produced by the undiluted contents of alfentanil, fentanyl, morphine, sufentanil ampoules and by solutions of Ringer’s lactate, 0.9% saline, 3.3% dextrose in 0.3% saline, and distilled water. Each opioid was then serially diluted in serial 1:2, 1:4, and 1:8 dilutions in each of these solutions and the refractions of each determined. Based on this information, blinded identification of various diluted opioid solutions was attempted. Refractometer values for undiluted fentanyl and sufentanil were identical with those for distilled water. Those for undiluted alfentanil and morphine were almost identical with each other and with 1:2 and 1:4 dilutions of either drug in Ringer’s lactate or 0.9% saline. We conclude that refractometry is an unreliable screening method to detect tampering with opioid solutions.  相似文献   
104.
105.
The inhibitory effects on platelet reactivity of increased extracellular magnesium were investigated. Wherever possible, experiments were performed in hirudinized whole blood. Concentration dependent inhibition of platelet aggregation and dense granule release were observed with MgSO(4). Antiaggregatory effects were identical with MgCl(2), indicating that the effects are due to the Mg(2+) ion. Antiaggregatory effects of CaCl(2), differed from those of MgCl(2), indicating that this is not a non-specific divalent cation effect. MgSO(4) also caused concentration-dependent inhibition of platelet thromboxane production. Experiments in the presence of apyrase and indomethacin showed that complex formation with ADP and inhibition of cyclo-oxygenase do not entirely account for the inhibitory effect of magnesium on platelet activation. Studies with an anti-GPIIb/IIIa antibody showed that the inhibitory effects on the release reaction and thromboxane synthesis are independent of those on aggregation. The results are consistent with magnesium modifying an intracellular signal transduction pathway common to several agonists, rather than the effects of magnesium being specific for one agonist. This study also shows that MgSO(4) inhibits agonist-induced increases in intracellular free calcium. Increasing the extracellular concentration of magnesium up to 10 mM had no effect on agonist-induced increments in intraplatelet free Mg(2+) concentration.  相似文献   
106.
The degree of practice effects with the Brief NIMH Neuropsychological Battery for HIV Infection and AIDS is reported using a 7-10 day test-retest interval. The patient groups were asymptomatic and symptomatic of HIV while the control group was made up of "at risk" volunteers. Statistically significant practice effects were obtained on the California Verbal Learning Test, the Paced Auditory Serial Addition Task and the Visual Search Test among the infected individuals. The controls subjects demonstrated statistically significant practice effects on all of the neuropsychological tests. The implications of these findings in prospective studies are discussed.  相似文献   
107.
108.
OBJECTIVE: To develop an algorithm for determining the stage of change for dietary fat intake in African-American women. DESIGN: We examined the relationships between stage of change, dietary fat intake, and associated eating behaviors and developed an assessment tool for placing subjects in their appropriate stage of change. SUBJECTS: Working class and middle-income African-American women in Nashville, Tenn; 174 in study 1 and 208 in study 2. STATISTICAL ANALYSES: Fat and fiber intake by stage of change was examined using multivariate analysis of variance. Hierarchical cluster analysis was performed using Ward's method. RESULTS: A significant difference in fat intake was noted between women trying to change their intake and those not trying to change in study 1 (P < .001) and study 2 (P < .03). Of those trying to change, only 34% (study 1) and 9% (study 2) of subjects reported fat intakes below the Healthy People 2000 goal of 30% of energy from fat. In study 1, cluster analysis identified 14 groups of foods that significantly separated subjects into not trying, noncompliant, and compliant categories. Compliant subjects ate out less; ate fewer snack foods and less chicken, meat, and fat; and ate more fruits, vegetables, breakfast foods, and low-fat products. These results led to development of the Eating Styles Questionnaire (study 2), which facilitated more appropriate placement of the noncompliant group in stages of change for dietary fat intake. APPLICATIONS/CONCLUSIONS: These data support the stage construct of the Transtheoretical Model for dietary fat reduction in African-American women. Moreover, the Eating Styles Questionnaire (ESQ) can improve determination of stage of change for this group of women. The ESQ can be used to diagnose the eating styles that contribute to a high-fat intake and help in the design of interventions to lower fat intakes.  相似文献   
109.
BACKGROUND: For acute cholecystitis in the latter 19th century and early 20th century, the diagnosis was difficult and the management not defined. METHODS AND RESULTS: Bernhard Riedel of Jena in Germany documented his patients, analysed his results, and described his method of cholecystectomy. CONCLUSIONS: Riedel advocated early operation for acute cholecystitis when the conditions were favourable, as for acute appendicitis. He stressed the importance of good lighting, an experienced surgeon and trained assistants. He advocated conservative treatment for minor cholecystitis (biliary colic) until the diagnosis was certain, followed by elective cholecystectomy to reduce the risk of subsequent acute cholecystitis or bile duct stones. Caution was advised when analysing previous statistics, to ensure appropriate patient comparison.  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