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   3772篇
  免费   137篇
  国内免费   64篇
耳鼻咽喉   85篇
儿科学   90篇
妇产科学   97篇
基础医学   522篇
口腔科学   145篇
临床医学   407篇
内科学   451篇
皮肤病学   36篇
神经病学   381篇
特种医学   217篇
外科学   221篇
综合类   368篇
一般理论   1篇
预防医学   257篇
眼科学   88篇
药学   348篇
中国医学   46篇
肿瘤学   213篇
  2023年   29篇
  2022年   61篇
  2021年   99篇
  2020年   83篇
  2019年   78篇
  2018年   90篇
  2017年   58篇
  2016年   65篇
  2015年   81篇
  2014年   180篇
  2013年   249篇
  2012年   183篇
  2011年   215篇
  2010年   159篇
  2009年   196篇
  2008年   174篇
  2007年   189篇
  2006年   169篇
  2005年   132篇
  2004年   118篇
  2003年   106篇
  2002年   79篇
  2001年   64篇
  2000年   76篇
  1999年   85篇
  1998年   62篇
  1997年   77篇
  1996年   60篇
  1995年   57篇
  1994年   47篇
  1993年   54篇
  1992年   47篇
  1991年   53篇
  1990年   44篇
  1989年   38篇
  1988年   33篇
  1987年   35篇
  1986年   47篇
  1985年   37篇
  1984年   56篇
  1983年   22篇
  1982年   45篇
  1981年   24篇
  1980年   28篇
  1979年   21篇
  1978年   10篇
  1977年   17篇
  1976年   10篇
  1975年   8篇
  1973年   7篇
排序方式: 共有3973条查询结果,搜索用时 15 毫秒
11.
本文介绍了一种双歧杆菌的选择鉴别培养基,并用该培养基对重庆市正常人群肠道双歧杆菌进行了定量分析,进而确定了正常值,为进一步研究双歧杆菌与人类的健康和疾病以及生态学防治提供了科学依据.同时也显示了正常人类肠道中双收杆菌的含量与年龄及性别无显著差异.  相似文献   
12.
Ultrasonography in the detection of cervical incompetency   总被引:2,自引:0,他引:2  
In 80 pregnancies with clinical and ultrasonic signs of cervical incompetency, the length of the cervix and the thickness of the anterior wall of a lower uterine segment have been evaluated ultrasonically. We have also measured the width of the endocervical canal and studied the prolapse of fetal membranes (with fetal parts) into the endocervical canal. We evaluated these same parameters in 80 healthy pregnancies. The length of the cervix, the thickness of the anterior wall of a lower uterine segment, and the width of the endocervical canal were followed longitudinally in the patients from the 10th to the 36th gestation week. No statistically significant differences between age groups were found. In four age groups at risk for cervical incompetency, cervical lengths and wall thickness were significantly different (p less than 0.001) from those in comparable controls. Forty-five percent of the patients in the at-risk group, with cervical cerclage, delivered at 37.3 (range: 32 to 41) weeks and 6.25% of pregnancies ended in abortion when the amniotic membrane herniated into the cervical canal, with or without some part of the fetus.  相似文献   
13.
学龄儿童掌指骨发育某些正常变异的观察   总被引:1,自引:0,他引:1  
1980年和1990年对1259名城乡7~12岁学龄儿童掌指骨发育的正常变异进行了观察。结果证实,小指中节骨发育变异的检出率最高(总检出率14.7%),且男女儿童1990年此率均高于1980年(P<0.05),反映城市儿童该变异近10年有增高的趋势;1990年男女学龄儿童小指中节骨变异检出率城市明显高于农村(P<0.01);Ⅱ掌骨副骨骺总检出率3.8%,指骨骺核硬化总检出率2.2%,这两种变异男性明显高于女性.且无城乡差异。本观察各年龄组小指中节骨的变异同骨龄无规律性联系。  相似文献   
14.
The aim of our study was to establish normal values of urinary pyridinoline (Pyr) and deoxypyridinoline (DPyr) excretion for children aged 3–18 years, examine the biological variability of the marker, and assess its clinical value for pediatric patients with growth hormone deficiency. Pyr and DPyr was measured in first void urine samples from 692 healthy subjects (340 boys, 352 girls) by high-performance liquid chromatography. At sampling, age, body height, and weight was recorded for all individuals. Short-term variability in crosslinks excretion was examined in four healthy children. The clinical value of the marker was studied in seven patients with growth hormone (GH) deficiency. In childhood, crosslinks excretion exceeded normal adult values by about fivefold and declined during puberty. In the age range of 13–18 years, gender-related differences in Pyr and DPyr levels were observed, presumably resulting from the earlier onset of puberty in girls. Urinary levels of Pyr and DPyr were highly correlated both in males and females. Pyr/DPyr ratio was significantly higher in adolescents than children, suggesting enhanced release of Pyr from extraosseous sources. In both genders, neither age nor anthropometric variables showed a linear effect on crosslinks excretion. The range of within-subject, short-term variability in urinary Pyr and DPyr was relatively high (CV: 6%–21%), indicating that single measurements of crosslinks excretion may not adequately reflect bone resorption rates in children. Pyr and DPyr levels were significantly lower in GH-deficient patients and normalized during human growth hormone (hGH) therapy. Significant correlations between growth velocity (GV) and crosslinks levels were found, but individual prediction of GV increment during hGH treatment may be inaccurate. Pyr/DPyr ratio was not related to GV. It is concluded that measurement of urinary Pyr and DPyr excretion in children may be a valuable tool to assess bone resorption rates in population-based studies. In individual patients, however, only qualitative evaluation of disease severity and response to treatment seems justified.  相似文献   
15.
16.
This paper discusses the use of the Milgram obedience experiments and the Tuskegee syphilis study in the bioethical literature. The two studies are presented and a variety of uses of them identified and discussed. It is argued that the use of these studies as paradigms of problematic research relies on a reduction of their complexity. What is discussed is thus often constructions of these studies that are closer to hypothetical examples than to the real studies.  相似文献   
17.
Summary. The effect of age and sex on relative changes in blood flow and vascular resistance in skeletal muscle and subcutaneous tissue during postural changes and during local increase in transmural pressure was studied in 33 healthy subjects. The intra-individual variation was studied in five subjects. Blood flow was measured by the local 133Xenon wash-out method. No relation to age or sex was seen in the centrally elicited sympathetic vasoconstrictor responses in subcutaneous tissue and skeletal muscle and in the locally elicited vasoconstriction in subcutaneous tissue. A small, but statistically significant, correlation to sex and age was found in the local sympathetic vasoconstrictor response in skeletal muscle. The age correlation was caused only by an attenuated response in the young subjects below 40 years of age and may be fortuitous. The intra-individual variation was acceptably small. Based on the present results, a reduction in blood flow in skeletal muscle and subcutaneous tissue during centrally or locally elicited sympathetic vasoconstriction of 10% or less should be considered abnormal. The local 133Xenon wash-out method is of value in examining patients suspected of dysfunction in the sympathetic part of the autonomic nervous system.  相似文献   
18.
本文将生化自动分析仪应用于健康检诊中,就其中1089名健康者的血清进行12项生化指标的检测,并对测得的结果进行分析整理,确定国人的正常值范围。同时又对自动分析仪的质量管理进行了探讨。  相似文献   
19.
Gender differences after acute cocaine administration have received little attention in spite of the fact that males and females respond differently to many drugs. Seven male and seven female occasional cocaine users received both an intranasal dose of cocaine hydrochloride (0.9 mg/kg) and placebo powder in a randomized order and reported subjective effects via an instrumental joystick device and various questionnaires. Blood samples were withdrawn at 5-min intervals to assess pharmacokinetic differences. Male subjects achieved the highest peak plasma cocaine levels (144.4 ± 17.5 ng/ml), detected cocaine effects significantly faster than females and also experienced a greater number of episodes of intense good and bad effects. Women studied during the follicular phase of their menstrual cycle had peak plasma cocaine levels of 73.2 ± 9.9 ng/ml, which was significantly higher than when they were studied during their luteal phase (54.7 ± 8.7 ng/ml), but there were no differences in their subjective reports of cocaine effects. In spite of the different cocaine blood levels and subjective effects, peak heart rate increases did not differ between males and females suggesting that women may be more sensitive than males to the cardiovascular effects of cocaine. These data suggest that there are significant gender and menstrual cycle differences in the response to acute intranasal cocaine administration and these differences may have implications for the differential abuse of this drug.This paper is dedicated to Xavier Lamas, MD, PhD, who lost his life while ascending Mt. Everest, August 1995  相似文献   
20.
年龄因素对健康人心率变异性的影响   总被引:1,自引:0,他引:1  
目的探讨年龄因素对健康人心率变异性(HRV)的影响。材料与方法将236例健康人分为五个年龄组,使用美国先进医用设备公司5.0版本HRV软件做短时时域及频域HRV分析。结果年龄因素对健康人HRV短时时域和频域分析的多项指标产生显著影响,随着年龄增大,时域指标中的HRSD、SDANN、rMSSD及PNN50均逐渐降低;随着年龄增长,频域指标中各频段下的绝对面积,即:VLF、LF、MF及HF均逐渐降低;而频域指标中各频段下的相对面积,即:VLFP、LFP、MFP、HFP随着年龄增长呈不同的发展趋势。LF/HF随着年龄的增加而逐渐升高。结论HRV随着年龄的增加而下降,尤以迷走神经活性下降为显著。频域指标中各频段的相对面积较绝对面积能更敏感地反映交感、迷走神经张力的消长。  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