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   4016篇
  免费   295篇
  国内免费   87篇
耳鼻咽喉   39篇
儿科学   154篇
妇产科学   61篇
基础医学   498篇
口腔科学   61篇
临床医学   641篇
内科学   796篇
皮肤病学   60篇
神经病学   205篇
特种医学   463篇
外科学   378篇
综合类   107篇
一般理论   1篇
预防医学   382篇
眼科学   38篇
药学   307篇
中国医学   1篇
肿瘤学   206篇
  2021年   36篇
  2020年   30篇
  2019年   51篇
  2018年   69篇
  2017年   42篇
  2016年   54篇
  2015年   59篇
  2014年   66篇
  2013年   128篇
  2012年   140篇
  2011年   176篇
  2010年   124篇
  2009年   116篇
  2008年   133篇
  2007年   213篇
  2006年   157篇
  2005年   173篇
  2004年   128篇
  2003年   130篇
  2002年   113篇
  2001年   126篇
  2000年   167篇
  1999年   132篇
  1998年   137篇
  1997年   129篇
  1996年   147篇
  1995年   122篇
  1994年   120篇
  1993年   100篇
  1992年   85篇
  1991年   99篇
  1990年   78篇
  1989年   80篇
  1988年   82篇
  1987年   64篇
  1986年   71篇
  1985年   66篇
  1984年   32篇
  1983年   47篇
  1982年   33篇
  1981年   30篇
  1980年   22篇
  1979年   25篇
  1978年   25篇
  1977年   29篇
  1976年   20篇
  1975年   19篇
  1974年   24篇
  1973年   16篇
  1969年   15篇
排序方式: 共有4398条查询结果,搜索用时 15 毫秒
31.
OBJECTIVE: To assess the accuracy of three-dimensional color Doppler sonography and uterine artery arteriography in depicting changes in fibroid vascularity before and after embolization. METHODS: Preembolization and postembolization three-dimensional color Doppler sonography and selective uterine artery arteriography were retrospectively compared in 15 patients who underwent uterine artery embolization for treatment of symptomatic fibroids. Three-dimensional color Doppler sonography was performed by using a scanner with color power angiographic imaging capability. Vascularity was quantified by using an estimation of power-weighted pixel density as described by our group in previously published studies. Uterine artery arteriography was performed by using a standard selective microcatheter embolization technique. For purposes of comparison, fibroids were classified as either hypervascular or hypovascular relative to myometrial vascularity before and minutes to several hours after uterine artery embolization. Changes in fibroid vascularity (i.e., from hypervascular to hypovascular) as depicted by three-dimensional color Doppler sonography were compared with those shown on uterine artery arteriography and classified as being in agreement or disagreement. RESULTS: In 13 (87%) of 15 patients there was agreement; in 2 (13%) of 15 there was disagreement. In both cases of disagreement, three-dimensional color Doppler sonography showed collateral flow not depicted by uterine artery arteriography The mean reduction in quantitated vascularity after uterine artery embolization was 44% (range, 19%-78%). CONCLUSIONS: Three-dimensional color Doppler sonography accurately depicts fibroid vascularity and in some cases can reveal collateral flow not depicted by uterine artery arteriography.  相似文献   
32.
Hyperinsulinaemia is said to be a risk factor for cardiovasculardisease, but the extent to which different insulinaemic measuresare associated with vascular risk factors in ostensibly healthyindividuals, and whether they operate independently in men andwomen, remains uncertain. The association between risk factors and various insulinaemicmeasures was examined in 148 men and 118 women who were normoglycaemic,normotensive, and non-obese (body mass index in men <27,in women <25). A 75 g glucose tolerance test was administeredafter blood sampling for fibrinogen, lipids, lipoproteins andinsulin. Insulin was also measured after 1 and 2 hours. Significantunivariate correlations (p<0.01) were most consistently recordedbetween insulinaemic measures and fasting serum triglyceridesin men and women, whilst systolic blood pressure only correlatedwith insulinaemia in women, and diastolic blood pressure correlatedwith fasting and 2 hour insulinaemic measures in men and women.Inconsistent associations were noted with total serum cholesterolin men and women, with high density lipoprotein cholesterol,body mass index, apoprotein B and A1 in men, and with fibrinogenin women. Age was not correlated with any insulinaemic measurein men or women. Differences in vascular risk factors between quintiles of theinsulinaemic measures were examined, after correction for bodymass index. The dominant association with fasting and post-glucoseload insulinaemic measures was with triglycerides, especiallyin women, with less frequent graded differences between quintilesobserved for total cholesterol, and diastolic and systolic bloodpressures in men and women. The incidence of other risk factors often only differed in thelowest or highest quintile in comparison to other quintiles,suggesting a threshold rather than a graded effect. Furthermore,differences in HDL cholesterol and apoprotein B were only recordedfor top quintiles of post-glucose challenge/integrated insulinaemicmeasures in men, whilst serum fibrinogen concentrations onlydiffered significantly in women in the top insulinaemic areaunder the curve quintile. In the absence of additional risk factors such as diabetes,hypertension and obesity, insulinaemic measures are not consistentlyrelated to blood pressure and measures of lipid metabolism andcoagulation, and are thus a weak predictor of other cardiovascularrisk factors. The vascular risk profile associated with insulinappears somewhat different in apparently healthy men and women.  相似文献   
33.
Sexual relations in later life: a national study of married persons   总被引:4,自引:0,他引:4  
Sexual behavior among married persons 60 years of age and older was examined using data from the National Survey of Families and Households. About 53 percent of the entire sample, and 24 percent of those 76 years of age and older, report having had sexual relations at least once within the past month. Persons who have been sexually active within the past month report having sex about four times during the month. While respondent's age is significantly related to sexual behavior, the monthly incidence and overall sexual frequency variables are not influenced by gender, race, or a Gender by Spouse's Health Status interaction term. While the NSFH variables included in our model are poor predictors of elderly persons' sexual behavior, analyses reveal that a person's sense of self-worth/competence and his/her partner's health status are significantly and positively related to the incidence of sex within the past month.  相似文献   
34.
Reiman  TH; Heiken  JP; Totty  WG; Lee  JK 《Radiology》1988,169(2):564-566
Limited-field-of-view radio-frequency receiver antennas provide improved near-field sensitivity for magnetic resonance imaging by decreasing the antenna volume. The Helmholtz-type surface coil, consisting of two flat rings, is an organ-encompassing antenna that takes advantage of this principle to yield an improved signal-to-noise ratio (S/N). The coil was tested in a group of 50 patients and 16 healthy volunteers. Images obtained with the Helmholtz coil demonstrated quantitatively superior S/N of 2.2-fold or greater than that of comparison body coil images, as well as qualitatively superior anatomic resolution.  相似文献   
35.
36.
Macrophage migration inhibitory factor is a key pro-inflammatory mediator. A 5-CATT repeat functional polymorphism within the promoter of the gene was previously associated with the lowest promoter activity. It was hypothesised that patients exhibiting a 5-CATT allele would have a less aggressive inflammatory response with an associated less severe clinical phenotype in sarcoidosis. Irish Caucasian sarcoidosis patients (n = 173) followed up for 1-39 yrs and a control group (n = 166) were genotyped for the CATT repeat polymorphism. Disease severity at the time of diagnosis and at the time of elaboration of the present study was assessed by the presence of thoracic and extrathoracic symptoms, erythema nodosum, radiographic interstitial changes (chest radiograph score equal to stage II or greater, or high-resolution computed tomography confirmed), pulmonary function tests, steroid use, erythrocyte sedimentation rate, C-reactive protein and angiotensin-converting enzyme levels. In the Irish population studied, no evidence was found of a significant association between either sarcoidosis susceptibility and disease severity and the 5-CATT repeat functional polymorphism in the macrophage migration inhibitory gene. The present study found no significant association between the 5-CATT repeat macrophage migration inhibitory factor gene polymorphism and sarcoidosis, and did not support the overriding role for macrophage migration inhibitory factor in driving sarcoidosis pathogenesis.  相似文献   
37.
Whilst HLA matching is routine for renal transplantation, the possible benefits of matching donor and recipient age have not been previously examined. In this study we examined the simultaneous effect of donor to recipient age difference on the graft survival of 141 consecutive first cadaver transplant recipients treated by cyclosporin immunosuppression. Multivariate regression analysis, taking into account other variables of moderately matched recipients (i.e. dialysis time and type, donor/recipient sex, local/imported kidneys, recent sensitivity, total ischaemic time, preoperative transfusions), indicated that age-difference was the single most important variable (P less than 0.05). Individually there was no significant effect of recipient age, whilst older donors (aged greater than 50 years) were associated with significantly worse graft survival than those younger (P less than 0.01). When dealing with donors aged greater than or equal to 50 years the corresponding recipient 1-year graft was improved when the donor was no more than 5 years older than the transplant recipient. Donor age to recipient age difference is a potentially important selection criterion in renal transplantation.  相似文献   
38.
39.
We report the use of the AngioJet F140 rheolytic catheter to recannalize an acutely thrombosed aortopulmonary shunt in a 21-year-old female with palliated, complex congenital heart disease. After extracting the thrombus that filled the entire length of the shunt, three stents were placed at sites where the lumen was compromised by distortion or thrombus. Unobstructed flow was restored to the left pulmonary artery that persisted at 1-year follow-up.  相似文献   
40.
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