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   8743篇
  免费   605篇
  国内免费   28篇
耳鼻咽喉   67篇
儿科学   354篇
妇产科学   236篇
基础医学   1384篇
口腔科学   126篇
临床医学   1257篇
内科学   1586篇
皮肤病学   158篇
神经病学   952篇
特种医学   202篇
外科学   717篇
综合类   45篇
一般理论   8篇
预防医学   828篇
眼科学   151篇
药学   523篇
中国医学   9篇
肿瘤学   773篇
  2023年   71篇
  2022年   68篇
  2021年   201篇
  2020年   150篇
  2019年   219篇
  2018年   263篇
  2017年   182篇
  2016年   231篇
  2015年   233篇
  2014年   315篇
  2013年   465篇
  2012年   663篇
  2011年   654篇
  2010年   360篇
  2009年   316篇
  2008年   640篇
  2007年   608篇
  2006年   566篇
  2005年   593篇
  2004年   513篇
  2003年   456篇
  2002年   436篇
  2001年   75篇
  2000年   41篇
  1999年   63篇
  1998年   98篇
  1997年   81篇
  1996年   67篇
  1995年   69篇
  1994年   51篇
  1993年   50篇
  1992年   23篇
  1991年   32篇
  1990年   28篇
  1989年   27篇
  1988年   23篇
  1987年   16篇
  1986年   30篇
  1985年   29篇
  1984年   30篇
  1983年   26篇
  1982年   21篇
  1981年   37篇
  1980年   25篇
  1979年   15篇
  1978年   19篇
  1977年   12篇
  1976年   17篇
  1972年   10篇
  1971年   11篇
排序方式: 共有9376条查询结果,搜索用时 656 毫秒
151.
BACKGROUND: Light-induced fluorescence endoscopy (LIFE) may improve the detection of high-grade dysplasia (HGD) and early stage cancer (EC) in Barrett's esophagus (BE). The aim of this study was to compare LIFE with standard endoscopy (SE) in a randomized crossover study. METHODS: Fifty patients with BE underwent SE and LIFE in a randomized sequence (4 to 6-week interval between procedures). The two procedures were performed by two different endoscopists who were blinded to the findings of the other examination. Targeted biopsy specimens were taken from detected lesions, followed by random biopsy specimens with a 2-cm interval, 4-quadrant protocol. Biopsy specimens were routinely evaluated and subsequently reviewed by a single, blinded expert GI pathologist. RESULTS: Targeted biopsy specimens had a sensitivity for the diagnosis of HGD/EC of 62% (8/13) for both techniques. The overall sensitivity (all biopsy specimens) was 85% for SE and 69% for LIFE (p = 0.69). All targeted biopsy specimens had a positive predictive value (PPV) for HGD/EC of 41% for SE and 28% for LIFE (p = 0.40); autofluorescence-targeted biopsy specimens had a PPV of 13%. False-positive lesions had a significantly higher rate of acute inflammation than random biopsy specimens. CONCLUSIONS: In this study, LIFE did not improve the detection of HGD or EC in patients with BE compared with SE.  相似文献   
152.
OBJECTIVE: Surgical cure of Cushing's syndrome (CS) is followed by adrenocortical insufficiency, which may be long-lasting. The aim was to elucidate recovery of adrenocortical function, defined as a normal cortisol response to ACTH stimulation, and the relation to ACTH in patients cured for CS due to pituitary Cushing's disease (CD) or adrenal (AA) adenomas. DESIGN: A retrospective study including 32 patients considered surgically cured for CS (18 CD, 14 AA). RESULTS: Twelve (67%) patients with CD recovered within median 24 months (range 7 months-4(1)/(2) years) whereas six did not recover within 3-12 years. Plasma ACTH (p-ACTH) at time of recovery was not different from p-ACTH in patients not recovering (P = 0.9). Eleven (79%) patients with AA recovered within 24 months (10 months-4 years) whereas three did not recover within 4-10 years. p-ACTH at time of recovery was higher compared to patients not recovering (P < 0.04). No differences were observed comparing CD and AA patients concerning preoperative 24-h urinary free cortisol (UFC) excretion, postoperative unstimulated s-cortisol or recovery time. By contrast, p-ACTH measured at time of recovery was higher in AA compared to CD (median 12.3 vs. 4.6 pmol/l) (P < 0.001), whereas plasma dehydroepiandrosterone sulfate (p-DHEAS) was lower in AA compared to CD (median 300 vs. 1500 nmol/l) (P = 0.02). CONCLUSION: Recovery of secondary adrenal insufficiency is a slow process in both CD and AA. ACTH measured at time of recovery was significantly higher and DHEAS significantly lower in patients with AA compared to CD, which may suggest different mechanisms of the recovery process and different set points in the glucocorticoid feedback inhibition of ACTH secretion.  相似文献   
153.
154.
155.
156.
157.

BACKGROUND:

There are almost three million octogenarians living in France, many of whom present with a coronaropathy. Moreover, it appears that life expectancy at 80 years of age is still important.

OBJECTIVE:

To evaluate the results of coronary surgery among these patients.

METHODS:

Eighty-eight consecutive octogenarians who had an isolated coronary artery bypass surgery between 1996 and 2002 were compared with 165 patients 60 to 70 years of age; the two groups had been paired according to the main risk factors. Patients were contacted by telephone and then received a quality-of-life-related questionnaire.

RESULTS:

Operative mortality was 2.3% in the octogenarian versus 1.2% in the 60- to 70-year-old group (P not significant). There was more low cardiac output syndrome, postoperative acute renal failure and transfusion in octogenarians. Long-term survival (average duration of follow-up was 3.8 years) was higher in the 60- to 70-year-old group: 89.7% versus 77.9% (P=0.025). Four independent risk factors of long-term increased mortality were found: age, diabetes, history of stroke and postoperative blood transfusion. Finally, the long-term survival in the octogenarians who had this surgery was higher than in the octogenarians of the general French population to a significant degree, with a quality of life considered to be satisfactory.

CONCLUSION:

For selected octogenarians, an isolated coronary surgery can be proposed, with short- and long-term results comparable with those of a younger population.  相似文献   
158.
159.
OBJECTIVES: Although human immunodeficiency virus (HIV)-infected patients are now living longer, there are no published data on colorectal cancer (CRC) screening in this population. We hypothesized that HIV-infected patients were less likely to be screened for CRC compared to patients without HIV. METHODS: Consecutive HIV-infected patients > or =50 yr old seen in our outpatient clinic from 1/1/01 to 6/30/02 were identified. For each HIV-infected patient, we selected one age- and gender-matched control subject without HIV infection who was seen during the same time period. The electronic medical records were reviewed to determine the proportion of patients that had a fecal occult blood test (FOBT), flexible sigmoidoscopy, air-contrast barium enema (ACBE), or colonoscopy. RESULTS: During the 18-month study period, 538 HIV-infected outpatients were seen and 302 (56.1%) were > or =50 yr old. Despite significantly more visits with their primary care provider, HIV-infected patients were less likely to have ever had at least one CRC screening test (55.6%vs 77.8%, p < 0.001). The proportion of HIV-infected patients who ever had a FOBT (43.0%vs 66.6%, p < 0.001), flexible sigmoidoscopy (5.3%vs 17.5%, p < 0.001), ACBE (2.6%vs 7.9%, p= 0.004), or colonoscopy (17.2%vs 27.5%, p= 0.002) was significantly lower than in control subjects. In addition, HIV-infected patients were significantly less likely to be up-to-date with at least one CRC screening test according to current guidelines (49.3%vs 65.6%, p < 0.001). CONCLUSIONS: A substantial number of HIV-infected patients are > or =50 yr of age and CRC screening is underutilized in this population. Public health strategies to improve CRC screening in HIV-infected patients are needed.  相似文献   
160.
We studied the effects of long-term (i.e. 4 wk) voluntary exercise on the hypothalamic-pituitary-adrenocortical (HPA) axis in male mice. Voluntary exercise was provided by giving mice access to a running wheel, in which they indeed ran for about 4 km/d. Exercising mice showed similar body weights as control animals but presented less abdominal fat, lighter thymuses, and heavier adrenal glands. Exercise resulted in asymmetric structural changes in the adrenal glands. Whereas control mice had larger left than right adrenals, this condition was abolished in exercising animals, mainly because of enlargement of the right adrenal cortex. Tyrosine hydroxylase mRNA expression in the adrenal medullas of exercising mice was increased. In exercising mice, early-morning baseline plasma ACTH levels were decreased, whereas plasma corticosterone levels at the start of the dark phase were twice as high as those in control animals. To forced swimming and restraint stress, exercising mice responded with higher corticosterone levels than those of the control animals but with similar ACTH levels. However, if exposed to a novel environment, then exercising mice presented decreased ACTH responses. Interestingly, exercising mice showed a decreased corticosterone response to novelty only when the novel environment contained a functioning running wheel. Glucocorticoid receptor levels were unchanged, whereas mineralocorticoid receptor levels were decreased, in hippocampus of exercising animals. Corticotropin-releasing factor mRNA levels in the paraventricular nucleus were lower in exercising mice. Thus, voluntary exercise results in complex, adaptive changes at various levels within the HPA axis as well as in sympathoadrenomedullary and limbic/neocortical afferent control mechanisms. These changes seem to underlie the differential responsiveness of the HPA axis to physical vs. emotional challenges.  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