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   3382篇
  免费   196篇
  国内免费   15篇
耳鼻咽喉   33篇
儿科学   140篇
妇产科学   52篇
基础医学   474篇
口腔科学   56篇
临床医学   259篇
内科学   517篇
皮肤病学   126篇
神经病学   260篇
特种医学   145篇
外科学   437篇
综合类   371篇
预防医学   178篇
眼科学   84篇
药学   248篇
  1篇
中国医学   18篇
肿瘤学   194篇
  2023年   15篇
  2022年   27篇
  2021年   83篇
  2020年   35篇
  2019年   67篇
  2018年   84篇
  2017年   49篇
  2016年   71篇
  2015年   91篇
  2014年   96篇
  2013年   128篇
  2012年   177篇
  2011年   206篇
  2010年   175篇
  2009年   109篇
  2008年   159篇
  2007年   160篇
  2006年   161篇
  2005年   116篇
  2004年   137篇
  2003年   92篇
  2002年   98篇
  2001年   83篇
  2000年   99篇
  1999年   88篇
  1998年   48篇
  1997年   40篇
  1996年   41篇
  1995年   36篇
  1994年   36篇
  1993年   16篇
  1992年   46篇
  1991年   39篇
  1990年   45篇
  1989年   50篇
  1988年   38篇
  1987年   45篇
  1986年   44篇
  1985年   42篇
  1984年   34篇
  1983年   28篇
  1982年   24篇
  1981年   21篇
  1980年   27篇
  1979年   30篇
  1978年   20篇
  1977年   22篇
  1976年   16篇
  1975年   12篇
  1973年   15篇
排序方式: 共有3593条查询结果,搜索用时 78 毫秒
1.
2.
3.
4.
AIM: To evaluate and compare the utility of polymerase chain reaction (PCR) for the diagnosis of tuberculous effusions in children. METHODS: PCR, adenosine deaminase (ADA) activity and absolute lymphocyte count (ALC) were evaluated in the fluid of 31 tuberculous (20 pleural, 8 ascites and 3 pericardial) and 24 non-tuberculous (10 transudtative ascites, 8 empyema thoracis, 3 malignant pleural and 3 pyopericardium) effusions. RESULTS: Fluid PCR for Mycobacterium tuberculosis was positive in 74% of tuberculous effusions, whereas it was falsely positive in 13% of the non-tuberculous group. The mean fluid ADA and ALC values were significantly higher in tuberculous effusions than in non-tuberculous effusions (p<0.001). The sensitivity and specificity of PCR, ADA (> or =38 IU/l) and ALC (> or =275/mm3) were 74% and 88%, 81% and 75%, and 90% and 83%, respectively, in diagnosing tuberculous effusions. The sensitivity of PCR, ADA and ALC was 100%, 100% and 88%, respectively, for confirmed tuberculous effusions. When the two tests were combined (either/or positive), the sensitivity increased (90-100%) at the expense of specificity. When both the tests were positive, then the specificity markedly increased (92-96%), but sensitivity of the tests decreased. CONCLUSION: Fluid PCR alone should not be relied on as a single test; rather, combined analysis with either ADA or ALC could be more useful in the diagnosis of tuberculous effusions in children.  相似文献   
5.
BACKGROUND: The present study was aimed to define the gender ratio, familial occurrence, age of onset, precipitating factors, clinical types, nail and joint involvement of psoriasis in childhood and adolescence in Turkey. METHODS: A total of 61 children with psoriasis under 18 years old were evaluated retrospectively, for age, gender, age of disease onset, family history, concomitant disease, the clinical type of psoriasis, clinical localization, nail and joint involvement and treatment modalities. RESULTS: Of the patients, 23 (37.70%) were boys and 38 (62.30%) were girls. Mean age was 9.28 +/- 4.02 years in girls and 11.18 +/- 3.85 years in boys (9.96 +/- 4.03 years in all children). Mean age at the onset of the disease was 6.81 +/- 4.11 years in girls and 7.03 +/- 4.28 years in boys (6.89 +/- 4.14 years in all patients). In 14 (23%) cases, a positive family history was detected. The most frequent probable triggering factors were upper respiratory tract infections (14.8%) and positive throat culture for A group ss-hemolytic streptococcus (21.3%). Frequency of emotional stress and psychiatric morbidity were 54% and 9.8%, respectively. The most frequent localizations at onset were trunk (44.3%), extremities (54.0%), and scalp (36.0%). Three children (4.9%) had a history of dissemination from psoriatic diaper rash. In total, 51 (83.6%) patients presented with psoriasis vulgaris, eight (13.1%) with generalized pustular psoriasis, and the remaining two (3.3%) with erythrodermic psoriasis. CONCLUSION: The incidence of psoriasis among dermatological patients in childhood and adolescence was 3.8%. The disease tends to appear earlier in girls than boys. The authors suggested that stress and upper respiratory infections are the most important triggering factors in childhood and adolescence psoriasis.  相似文献   
6.
7.
I(indigenous)-compounds are age-related, carcinogen adduct-like, putative indigenous DNA modifications detectable by 32P-postlabeling assay in untreated animals. To investigate the origins of these DNA derivatives, we examined the effects of dietary vitamin E, a natural antioxidant, on I-compounds of rat liver and kidney DNA. Weanling female Sprague-Dawley rats were fed Draper's diets containing 0, 100, 1000, or 10,000 mg/kg alpha-tocopheryl acetate for 6 mo. The DNA from four individual rats of each group was analyzed by a nuclease P1-enhanced version of the 32P-postlabeling assay for DNA adducts. The amount of vitamin E in the liver was measured by high performance liquid chromatography. Rats fed vitamin E-deficient diet (0 mg/kg) showed identical profiles and similar levels of I-compounds as those fed the 100 mg/kg diet. Most I-spots were significantly intensified and one tissue-specific extra spot was found in both liver and kidney DNA of rats fed the 1000 or 10,000 mg/kg vitamin E diet. However, one of the five major I-spots detected in the kidney was weaker in the 1000 and 10,000 mg/kg groups than in the 0 and 100 mg/kg groups. These results show that formation of most I-compounds was not affected by vitamin E-deficient diet, and that long-term feeding of diet containing high levels of vitamin E may cause metabolic alterations leading to an increased formation of DNA-reactive (potentially mutagenic or carcinogenic) electrophiles.  相似文献   
8.
The intestinal uptake of [14C]oxalate, [14C]glyoxylate, and [14C]glycolate are studied in brush border membrane vesicles (BBMV) isolated from vitamin A-deficient and pair-fed control rats. The data obtained indicate that oxalate and its precursors are transported across the BBMV by passive diffusion. The intestinal uptake of glyoxylate and glycolate remains unaltered in vitamin A deficiency, while uptake rate of oxalate was significantly increased (p less than 0.01) in vitamin A-deficient rats as compared to pair-fed controls. In conclusion, the results indicate that vitamin A deficiency leads to hyperabsorption of oxalate through the gut.  相似文献   
9.
10.
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