全文获取类型
收费全文 | 5651篇 |
免费 | 686篇 |
国内免费 | 28篇 |
专业分类
耳鼻咽喉 | 33篇 |
儿科学 | 245篇 |
妇产科学 | 159篇 |
基础医学 | 862篇 |
口腔科学 | 145篇 |
临床医学 | 777篇 |
内科学 | 1076篇 |
皮肤病学 | 119篇 |
神经病学 | 416篇 |
特种医学 | 323篇 |
外科学 | 631篇 |
综合类 | 217篇 |
一般理论 | 7篇 |
预防医学 | 495篇 |
眼科学 | 108篇 |
药学 | 430篇 |
中国医学 | 1篇 |
肿瘤学 | 321篇 |
出版年
2021年 | 107篇 |
2020年 | 39篇 |
2019年 | 87篇 |
2018年 | 80篇 |
2017年 | 76篇 |
2016年 | 74篇 |
2015年 | 98篇 |
2014年 | 125篇 |
2013年 | 197篇 |
2012年 | 206篇 |
2011年 | 218篇 |
2010年 | 135篇 |
2009年 | 184篇 |
2008年 | 190篇 |
2007年 | 213篇 |
2006年 | 206篇 |
2005年 | 209篇 |
2004年 | 212篇 |
2003年 | 218篇 |
2002年 | 236篇 |
2001年 | 237篇 |
2000年 | 231篇 |
1999年 | 185篇 |
1998年 | 113篇 |
1997年 | 109篇 |
1996年 | 98篇 |
1995年 | 91篇 |
1994年 | 78篇 |
1993年 | 100篇 |
1992年 | 121篇 |
1991年 | 137篇 |
1990年 | 157篇 |
1989年 | 155篇 |
1988年 | 153篇 |
1987年 | 138篇 |
1986年 | 115篇 |
1985年 | 109篇 |
1984年 | 92篇 |
1983年 | 81篇 |
1982年 | 72篇 |
1981年 | 57篇 |
1980年 | 57篇 |
1979年 | 60篇 |
1978年 | 63篇 |
1977年 | 57篇 |
1976年 | 32篇 |
1975年 | 36篇 |
1974年 | 42篇 |
1973年 | 29篇 |
1972年 | 32篇 |
排序方式: 共有6365条查询结果,搜索用时 31 毫秒
1.
Emma J. Walker Noni E. MacDonald Nehal Islam Nicole Le Saux Karina A. Top Deshayne B. Fell 《Vaccine》2019,37(13):1725-1735
Objective
To systematically review literature on uptake and timeliness of diphtheria-tetanus-pertussis, measles-mumps-rubella, and/or polio-containing vaccines in infants who were born preterm, with a low birth weight, and/or with chronic health conditions that were diagnosed within the first 6?months of life.Methods
Using a standardized search strategy developed by a medical librarian, records were extracted from MEDLINE, Embase, Database of Abstracts of Reviews of Effects, and CINAHL up to May 8, 2018.Results
Out of the 1997 records that were screened, we identified 21 studies that met inclusion criteria. Eleven studies assessed vaccine coverage and/or timeliness in preterm infants, 6 in low birth weight infants, and 7 in children with chronic health conditions. Estimates of coverage in these populations were highly variable, ranging from 40% to 100% across the vaccines and population groups.Conclusions
There is a lack of studies reporting coverage and timeliness of routine immunizations in special populations of children.Policy implications
Our review suggests a need for improved surveillance of immunization status in special populations of infants, as well as a need for standardization of reporting practices. 相似文献2.
3.
Spleen sizing by ultrasound in polycythaemia and thrombocythaemia: comparison with SPECT 总被引:3,自引:1,他引:2
M. Messinezy L. M. MacDonald T. O. Nunan N. B. Westwood S. Chinn & T. C. Pearson 《British journal of haematology》1997,98(1):103-107
Detection of non-palpable early splenic enlargement may aid diagnosis of primary polycythaemia (PP) and primary thrombocythaemia (PT). In this study linear spleen sizing by ultrasound has been compared with spleen volume estimation by single photon emission computerized tomography (SPECT) in 26 patients. Spleen length by ultrasound correlated well with SPECT volume estimation.
Ultrasound spleen length was also measured in 60 normal control subjects where the upper limit of the 95% reference range was 11.6 cm. Changes in spleen length with both age and body weight were substantial and overshadowed the imperfect reproducibility of this method. Therefore, interpretation of an individual's measured spleen length should be in relation to that predicted for adults of the same age and weight, particularly at the extremes of the younger, heavier patients and also the older, lighter patients.
Ultrasound spleen lengths of different patient groups (21 PP, 26 PT, 17 idiopathic erythrocytosis, 12 secondary polycythaemia, nine apparent polycythaemia) were compared both using the measured overall reference range and the differences from the values predicted for their age and weight. The comparison showed that almost all patients with PP whose spleens were not palpable had spleen lengths greater than the upper limit for the normal control group, but separation from the other patient groups was incomplete.
Detection of non-palpable splenomegaly by ultrasound length should remain a 'minor' criterion amongst the 'proposed modified diagnostic criteria' of PP. 相似文献
Ultrasound spleen length was also measured in 60 normal control subjects where the upper limit of the 95% reference range was 11.6 cm. Changes in spleen length with both age and body weight were substantial and overshadowed the imperfect reproducibility of this method. Therefore, interpretation of an individual's measured spleen length should be in relation to that predicted for adults of the same age and weight, particularly at the extremes of the younger, heavier patients and also the older, lighter patients.
Ultrasound spleen lengths of different patient groups (21 PP, 26 PT, 17 idiopathic erythrocytosis, 12 secondary polycythaemia, nine apparent polycythaemia) were compared both using the measured overall reference range and the differences from the values predicted for their age and weight. The comparison showed that almost all patients with PP whose spleens were not palpable had spleen lengths greater than the upper limit for the normal control group, but separation from the other patient groups was incomplete.
Detection of non-palpable splenomegaly by ultrasound length should remain a 'minor' criterion amongst the 'proposed modified diagnostic criteria' of PP. 相似文献
4.
5.
6.
7.
8.
Coronary artery bypass grafts: visualization with MR imaging 总被引:1,自引:0,他引:1
9.
Hysterosalpingography was performed in 31 patients by means of a low-dose scanning-beam digital radiographic system. The technique permits adequate evaluation of gynecologic abnormalities while allowing significant reduction in radiation: 2.4-mR (6.1 X 10(-7) C/kg) exposure to the skin and 0.7-mrad (7 X 10(-6) Gy) mean dose to the ovaries per image obtained. Sixteen patients demonstrated readily recognizable and documented abnormalities, corroborated by laparoscopy, laparotomy, or other supportive evidence. 相似文献
10.
Margaret MacDonald Matthew Law John Kaldor Jim Hales Gregory J. Dore 《The International journal on drug policy》2003,14(5-6):353
Objective: To examine the effectiveness of needle and syringe programmes (NSPs) in preventing HIV transmission among injecting drug users (IDUs).Methods: An ecological study design was used to determine change in HIV prevalence among injecting drug users between cities with and without NSPs. Several data sources, such as electronic journal databases, surveillance reports, websites, and index review of relevant journals, were used to identify studies of HIV seroprevalence among IDUs, and presence of NSPs. The rate of change in HIV prevalence was estimated by regression analysis.Results: There were 778 years of data from 99 cities globally included in the analysis. HIV prevalence decreased by 18.6% per annum in cities that introduce NSPs, and increased by 8.1% in cities that had never introduced NSPs (mean difference −24.7% [95% CI: −43.8, 0.5%], P=0.06). The mean difference was –33% when comparison was weighted to one over the variance of the regression estimator (29% decrease in cities with NSPs and 5% increase in cities without NSPs, P<0.001). When analysis was restricted to cities with first HIV seroprevalence less than 10%, the average annual change in seroprevalence was 18% lower in cities with NSPs (P=0.03).Conclusions: Despite the inherent limitations within an ecological study design, the study provides additional evidence that NSPs reduce transmission of HIV infection. The rapid spread of HIV among IDU populations and increasing rates of injecting in many countries calls for scaling up of NSPs as well as other harm reduction strategies. 相似文献