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   643篇
  免费   24篇
  国内免费   9篇
耳鼻咽喉   5篇
儿科学   38篇
妇产科学   6篇
基础医学   86篇
口腔科学   13篇
临床医学   71篇
内科学   143篇
皮肤病学   47篇
神经病学   19篇
特种医学   93篇
外科学   26篇
综合类   1篇
预防医学   27篇
眼科学   10篇
药学   65篇
肿瘤学   26篇
  2021年   6篇
  2019年   4篇
  2018年   5篇
  2016年   4篇
  2015年   8篇
  2014年   7篇
  2013年   17篇
  2012年   10篇
  2011年   8篇
  2010年   20篇
  2009年   18篇
  2008年   10篇
  2007年   14篇
  2006年   7篇
  2005年   7篇
  2004年   8篇
  2003年   8篇
  2002年   3篇
  2001年   10篇
  2000年   7篇
  1999年   12篇
  1998年   26篇
  1997年   29篇
  1996年   37篇
  1995年   28篇
  1994年   29篇
  1993年   16篇
  1992年   8篇
  1991年   19篇
  1990年   11篇
  1989年   29篇
  1988年   28篇
  1987年   27篇
  1986年   20篇
  1985年   23篇
  1984年   13篇
  1983年   4篇
  1982年   11篇
  1981年   9篇
  1980年   12篇
  1979年   8篇
  1978年   9篇
  1977年   7篇
  1976年   9篇
  1975年   8篇
  1974年   6篇
  1973年   3篇
  1972年   4篇
  1969年   3篇
  1966年   6篇
排序方式: 共有676条查询结果,搜索用时 15 毫秒
11.
12.
We surveyed the prevalence of parasitic infections in the mountainous province of Hoa Binh, north-west Vietnam, involving 526 households of six ethnic groups: Muong, Kinh, Dao, Thai, Tay and Hmong. Eggs or cysts of at least one parasite species were detected in 88% of stool samples (n = 2522). Prevalences of nematodes were high among all ethnic groups: hookworm (52%), Trichuris trichiura (50%) and Ascaris lumbricoides (45%). Ascaris infection appeared to be lower in households owning a latrine, was highest among children and decreased with age. Prevalence of hookworm rose during childhood, remained high until old age, was highest among adult women, but was not linked to anaemia. Eggs of Chlonorchis spp. were found in 126 (5%) individuals (of the Muong, Kinh or Thai groups only). Chlonorchiasis increased with age and was highest among adult men. Taenia eggs were found in three individuals (0.1%). Giardia lamblia was found in all districts and among all groups and the prevalence of infection was estimated at 3%.  相似文献   
13.
14.
15.
Impaired immune responsiveness in Plasmodium berghei immune mice   总被引:1,自引:0,他引:1  
Mice immunized against Plasmodium berghei parasites by drug-controlled infection exhibited decreased immunoresponsiveness against rabbit red blood cells (RRBC). Increasing RRBC antigen dose increased responsiveness, but agglutinating anti-RRBC antibodies of the IgG class remained undetectable. Clearance of colloidal carbon from the bloodstream of malaria-immunized mice was not different from controls. Removal of all the persistent parasites from immune mice did not restore responsiveness until 140 days after treatment, suggesting that the parasite per se did not influence responsiveness directly. Because of this, and because of the fact that priming of mice with RRBC before P. berghei immunization was not more effective than priming after immunization, it was concluded that antigen uptake and subsequent presentation were not impaired in P. berghei immune mice, in contrast to infected mice. Anti-RRBC antibodies were detected in serum of P. berghei immune mice, but regulation of responsiveness to RRBC by transfer of such immune mouse serum was not found. Immunoglobulin levels, especially of the IgG2 and IgG3 subclass were elevated in sera of P. berghei immune mice, which indicated an LPS-like polyclonal activation. The results also suggest that during drug-controlled infection, which leads to immunity against infection, a state of B-cell tolerance is induced.  相似文献   
16.
17.
Copy number variants at the 16p11.2 chromosomal locus are associated with several neuropsychiatric disorders, including autism, schizophrenia, bipolar disorder, attention‐deficit hyperactivity disorder, and speech and language disorders. A gene dosage dependence has been suggested, with 16p11.2 deletion carriers demonstrating higher body mass index and head circumference, and 16p11.2 duplication carriers demonstrating lower body mass index and head circumference. Here, we use diffusion tensor imaging to elucidate this reciprocal relationship in white matter organization, showing widespread increases of fractional anisotropy throughout the supratentorial white matter in pediatric deletion carriers and, in contrast, extensive decreases of white matter fractional anisotropy in pediatric and adult duplication carriers. We find associations of these white matter alterations with cognitive and behavioral impairments. We further demonstrate the value of imaging metrics for characterizing the copy number variant phenotype by employing linear discriminant analysis to predict the gene dosage status of the study subjects. These results show an effect of 16p11.2 gene dosage on white matter microstructure, and further suggest that opposite changes in diffusion tensor imaging metrics can lead to similar cognitive and behavioral deficits. Given the large effect sizes found in this study, our results support the view that specific genetic variations are more strongly associated with specific brain alterations than are shared neuropsychiatric diagnoses. Hum Brain Mapp 37:2833–2848, 2016. © 2016 Wiley Periodicals, Inc.  相似文献   
18.
2-D Doppler echocardiography was used to assess the occurrenceof haemodynamic abnormalities in 45 asymptomatic patients, aged4 to 16 years (median 7·4) after a Mustard operationfor transposition of the great arteries. The findings were comparedwith those derived from cardiac catheterization. Thirty-fivecardiac lesions were correctly diagnosed by 2-D Doppler echocardiographyin 23 patients, but on six occasions, minor abnormalities weremissed. 2-D Doppler echocardiography demonstrated systemic venouspathway obstruction of more than 3 mmHg at cardiac catheterizationin nine patients, and in five of the six patients with pulmonaryvenous channel obstruction. A left ventricular outflow tractobstruction (pressure difference > 15 mmHg) was diagnosedcorrectly by Doppler echocardiography in seven patients. Baffleleakage was found in two patients with a left to right shuntof 25% or more of pulmonary bloodflow, but was missed in fiveout of nine patients with small shunts. Tricuspid regurgitationwas well defined in eight patients, The absence of symptomsand a routine examination after a Mustard operation do not ruleout haemodynamic abnormalities. However, these, with the possibleexception of minor baffle leakage, can be detected by 2-D Dopplerechocardiography.  相似文献   
19.

Background

Regular exposure to tobacco smoke at home causes airway inflammation and altered cytokine regulation; however, there is variation between individuals of different countries.

Objective

To determine effects of passive smoking on plasma IL4, TNFá, and CRP in healthy male school-children in Khartoum.

Methods

A total of 135 male school-pupils (69 passive smokers and 66 non-smokers) were selected randomly from three primary schools for boys in Khartoum. Information about smoking history was collected from each pupil and his parents using a questionnaire. Plasma CRP, IL4 and TNFá were measured using commercially available ELISA kits.

Results

Plasma IL4 and TNFá in the passive smokers (mean ± SEM) is at 2.92 ± 0.93 and 19.78 ± 4.67 pg/ml respectively; whereas in the non-smokers . It is at 0.45 ± 0.28 and 5.05 ± 1.54 pg/ml respectively. The difference between the two groups is statistically significant (p <0.05). The mean plasma IL4 and TNFá were lowest with no exposure, higher with moderate exposure, and highest with heavy exposure (P < 0.05). Plasma CRP showed insignificant difference between the two groups.

Conclusion

Passive smoking causes significant rise in plasma TNFá and IL4 with a dose dependent effect among school-pupils in Khartoum.  相似文献   
20.
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