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   3638篇
  免费   256篇
  国内免费   21篇
耳鼻咽喉   61篇
儿科学   123篇
妇产科学   40篇
基础医学   474篇
口腔科学   472篇
临床医学   270篇
内科学   770篇
皮肤病学   111篇
神经病学   241篇
特种医学   175篇
外科学   443篇
综合类   56篇
一般理论   1篇
预防医学   317篇
眼科学   51篇
药学   199篇
中国医学   22篇
肿瘤学   89篇
  2023年   28篇
  2022年   45篇
  2021年   105篇
  2020年   89篇
  2019年   104篇
  2018年   135篇
  2017年   71篇
  2016年   115篇
  2015年   123篇
  2014年   166篇
  2013年   185篇
  2012年   236篇
  2011年   295篇
  2010年   211篇
  2009年   158篇
  2008年   200篇
  2007年   202篇
  2006年   149篇
  2005年   163篇
  2004年   129篇
  2003年   94篇
  2002年   71篇
  2001年   53篇
  2000年   68篇
  1999年   60篇
  1998年   51篇
  1997年   53篇
  1996年   49篇
  1995年   43篇
  1994年   29篇
  1993年   37篇
  1992年   20篇
  1991年   21篇
  1990年   27篇
  1989年   35篇
  1988年   25篇
  1987年   26篇
  1986年   29篇
  1985年   28篇
  1984年   17篇
  1983年   23篇
  1982年   15篇
  1981年   21篇
  1980年   10篇
  1979年   11篇
  1977年   11篇
  1976年   11篇
  1974年   9篇
  1972年   12篇
  1967年   8篇
排序方式: 共有3915条查询结果,搜索用时 31 毫秒
1.
2.
Objective: Polyunsaturated fatty acids n-3 (PUFA n-3) have shown effects in reducing tumor growth, in particular eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) abundantly present in fish oil (FO). When these fatty acids are provided in the diet, they alter the functions of the cells, particularly in tumor and immune cells. However, the effects of α-linolenic fatty acid (ALA), which is the precursor of EPA and DHA, are controversial. Thus, our objective was to test the effect of this parental fatty acid. Methods: Non-tumor-bearing and tumor-bearing Wistar rats (70 days) were supplemented with 1 g/kg body weight of FO or Oro Inca® (OI) oil (rich in ALA). Immune cells function, proliferation, cytokine production, and subpopulation profile were evaluated. Results: We have shown that innate immune cells enhanced phagocytosis capacity, and increased processing and elimination of antigens. Moreover, there was a decrease in production of pro-inflammatory cytokines (tumor necrosis factor-alpha (TNF-α) and interleukin 6 (IL-6)) by macrophages. Lymphocytes showed decreased proliferation capacity, increased cluster of differentiation 8 (CD8+) subpopulation, and increased TNF-α production. Conclusions: Oil rich in ALA caused similar immune modulation in cancer when compared with FO.  相似文献   
3.
4.
5.
6.
7.
Incidence and radiologic findings of neurocysticercosis were investigated in a series of 23,800 consecutive head examinations using computed tomography (CT). The condition was diagnosed in 168 cases (0.7%). The parenchymatous form was the most common presentation (96.3%), while the meningeal form corresponded to only 11.9 per cent of cases. These two forms coexisted in some cases. These findings reversed the knowledge on the condition based on conventional radiography. The different CT appearances in the brain are described and a new radiologic protocol for the CT evaluation of the condition is advocated, which includes a follow-up after a trial cure with Praziquantel in the presence of cysts not associated with suggestive brain calcifications. CT was more sensitive than conventional radiography in the differentiation between dead and living larvae, thus having an impact on the therapeutic management of the patients.  相似文献   
8.
BACKGROUND: Elevated liver enzymes are infrequent in patients with hepatitis C virus (HCV) infection undergoing chronic hemodialysis (HD), suggesting that the alanine aminotransferase (ALT) is a poor predictor of hepatocellular damage in this population. OBJECTIVE: To establish a more appropriate cut-off value of ALT to identify biochemical activity due to HCV infection in HD patients. STUDY DESIGN: A total of 217 patients, with an average age of 51.2 years, were evaluated between January and October 2002; 130 were males (60%). Serum ALT was measured by a kinetic method in five consecutive monthly blood samples, from which an average was obtained and divided by the upper limit of normal (ULN). HCV antibodies were determined using an enzyme immunoassay, the serum HCV-RNA by nested-PCR and HCV genotype by hybridization of the amplified sequence from the 5'-non-coding region. The cut-off value of ALT was obtained from a ROC curve. RESULTS: Within the 217 patients, 18 (8.3%) were anti-HCV-positive, 17 (7.8%) of whom were also HCV-RNA-positive. Genotype distribution was: 1a=47%; 1b=18%; 3a=35%. Mean ALT/ULN (0.77+/-0.57) of the 18 anti-HCV-positive cases was higher (p<0.001) than the negative group (0.38+/-0.23). The mean ALT/ULN (0.81+/-0.57) of the 17 HCV-RNA-positive cases was also higher (p<0.0001) than the negative cases (0.37+/-0.23). The cut-off value of ALT to distinguish the anti-HCV-positive from negative patients was 0.50% or 50% of the ULN (sensitivity=67%; specificity=83%). According to the HCV-RNA, the cut-off value of ALT was 0.45% or 45% of the ULN (sensitivity=71%; specificity=80%). CONCLUSION: Reducing the cut-off of ALT by half, enables a better identification of biochemical activity in patients with HCV infection on chronic HD.  相似文献   
9.
10.
Our objective was to evaluate the frequency of neoplastic and preneoplastic skin lesions in Parkinson's disease (PD) patients when compared with an aged-matched population. We performed a cross-sectional survey in PD patients and in an age-matched control group. Patients and controls were examined by a movement disorder specialist and a dermatologist. 150 PD patients and 146 controls were included. Thirty-five PD patients (23.3%) presented skin lesions that could be classified as neoplastic or preneoplastic vs. 20 subjects in the control group (13.7%) (OR 95%, CI 1.92 [1.05, 3.51]). However, this difference lost statistical significance when adjusted for gender (recruitment of controls was matched just for age with an over representation of males in the PD group). Twenty-nine PD patients (19%) presented actinic keratosis and basal cell carcinoma was diagnosed in 4 patients (3%). Although nonconclusive, our results are in agreement with previous studies suggesting an increased risk of skin cancer in PD patients. The frequency of actinic keratosis in PD patients and the associated risk to develop melanoma recommends its screening in future epidemiological studies.  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