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   19201篇
  免费   1901篇
  国内免费   40篇
耳鼻咽喉   159篇
儿科学   466篇
妇产科学   425篇
基础医学   2845篇
口腔科学   326篇
临床医学   1952篇
内科学   3475篇
皮肤病学   285篇
神经病学   1798篇
特种医学   655篇
外科学   2786篇
综合类   569篇
一般理论   59篇
预防医学   2201篇
眼科学   533篇
药学   1376篇
中国医学   11篇
肿瘤学   1221篇
  2023年   128篇
  2022年   195篇
  2021年   437篇
  2020年   251篇
  2019年   410篇
  2018年   449篇
  2017年   312篇
  2016年   316篇
  2015年   405篇
  2014年   529篇
  2013年   744篇
  2012年   1019篇
  2011年   1128篇
  2010年   569篇
  2009年   506篇
  2008年   948篇
  2007年   950篇
  2006年   815篇
  2005年   801篇
  2004年   819篇
  2003年   714篇
  2002年   680篇
  2001年   516篇
  2000年   510篇
  1999年   487篇
  1998年   215篇
  1997年   198篇
  1996年   185篇
  1995年   197篇
  1994年   171篇
  1993年   156篇
  1992年   366篇
  1991年   372篇
  1990年   356篇
  1989年   375篇
  1988年   297篇
  1987年   313篇
  1986年   302篇
  1985年   347篇
  1984年   262篇
  1983年   213篇
  1982年   121篇
  1980年   114篇
  1979年   194篇
  1978年   137篇
  1975年   118篇
  1974年   130篇
  1973年   121篇
  1972年   131篇
  1971年   110篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.

Background

The purpose of the study was to evaluate the association between fetal echocardiographic measurements and the need for intervention (primary coarctation repair, staged coarctation repair, or catheter intervention) in prenatally diagnosed coarctation of the aorta.

Methods

A single-centre retrospective cohort study (2005-2015) of 107 fetuses diagnosed with suspected coarctation of the aorta in the setting of an apex-forming left ventricle and antegrade flow across the mitral and aortic valves.

Results

Median gestational age at diagnosis was 32 weeks (interquartile range, 23-35 weeks). Fifty-six (52%) did not require any neonatal intervention, 51 patients (48%) underwent a biventricular repair. In univariable analysis, an increase in ascending aorta (AAo) peak Doppler flow velocity (odds ratio [OR], 1.40 [95% confidence interval [CI], 1.05-1.91] per 20 cm/s; P = 0.03) was associated with intervention. No intervention was associated with larger isthmus size (OR, 0.23; P < 0.001), transverse arch diameter (OR, 0.23; P < 0.001), and aortic (OR, 0.72; P = 0.02), mitral (OR, 0.58; P = 0.001), and AAo (OR, 0.53; P < 0.001) z-scores. In multivariable analysis, higher peak AAo Doppler (OR, 2.51 [95% CI, 1.54-4.58] per 20 cm/s; P = 0.001) and younger gestational age at diagnosis (OR, 0.81 [95% CI, 0.70-0.93] per week; P = 0.005) were associated with intervention, whereas a higher AAo z-score (OR, 0.65 [95% CI, 0.43-0.94] per z; P = 0.029) and transverse arch dimension (OR, 0.44 [95% CI, 0.18-0.97]; P = 0.05) decreased the risk of intervention.

Conclusions

In prenatally suspected coarctation, the variables associated with intervention comprised smaller AAo and transverse arch size, earlier gestational age at diagnosis, and the additional finding of a higher peak AAo Doppler.  相似文献   
2.
3.
Patients on long-term haemodialysis suffer from dialysis arthropathy due to the deposition of dialysis amyloid. We investigated the use of 99Tc-labelled methylene diphosphonate bone scans in 17 patients as a possible in vivo diagnostic technique. In most clinically affected joints, with the exception of shoulders and hands, there was increased radioisotope uptake consistent with uptake by periarticular bone. In addition, we describe intense soft-tissue uptake around some clinically affected large joints. In contrast, control groups of patients on haemodialysis without arthropathy and patients without renal failure did not have increased uptake. A semi-quantitative scale of uptake was devised, and the following correlations were significant: pain perception and isotope uptake score in the ankles and feet, and the number of radiological lesions and isotope uptake scores in the wrists and knees. The following sites where the radioisotope might bind in the affected joints are proposed: amyloid deposits, areas of soft-tissue calcification, or areas of increased bone turnover. It is concluded that whereas the scanning technique cannot make a definite diagnosis of amyloid and, therefore, cannot be expected to supersede histological diagnosis, it is a useful adjuvant investigation, of particular importance in those patients unable or unwilling to undergo biopsy.  相似文献   
4.
5.
A worldwide survey of the use of simulation in anesthesia   总被引:6,自引:0,他引:6  
PURPOSE: To gather information regarding the global use of simulation technology in education, evaluation and research in anesthesia. METHODS: The WorldWide Web was searched and located sites with simulation centres (n = 158) were mailed a 67-item questionnaire requesting information regarding demographics, personnel, education use and research involvement. Comments were solicited. Medical school data only are reported in this article. RESULTS: Two web sites were used to generate the list of simulation centres. Sixty responses were received (38%), with 41 emanating from medical schools. Seventy-seven percent of centres were involved in undergraduate education and 85% in postgraduate education. Few centres were involved in evaluation and/or competency assessments. Sixty-one percent of centres indicated ongoing research with a further 25% interested in international collaboration. University or university departmental-based funding largely supported simulation technology used in medical schools. The lack of financial and human resources was the single most common problem identified by respondents. CONCLUSIONS: From the survey responses received, opportunities for the simulator to be used for the assessment of performance appear to be under-utilized. This may be due to the lack of research in this area, lack of standardized, valid and reliable tests and the fact that most centres have only recently acquired this technology. Further research supporting the use of the simulator in education and evaluation is required.  相似文献   
6.
Background  Nonmelanoma skin cancer (NMSC) has been linked to cutaneous human papillomaviruses of the genus beta (betaPV).
Objectives  We sought to assess the presence of betaPV in NMSC biopsies from a group of Scottish skin cancer patients, both immunocompetent (IC) patients and immunosuppressed (IS) organ transplant recipients.
Methods  One hundred and twenty-one paraffin-embedded skin tumours (27 actinic keratosis, 41 intraepidermal carcinoma, 53 squamous cell carcinoma) and 11 normal skin samples were analysed for the presence of betaPV by a polymerase chain reaction–reverse hybridization assay designed to detect the presence of the 25 known betaPV genotypes.
Results  In IC patients, betaPV was detected in 30 of 59 (51%) tumours and two of 11 (18%) normal skin samples ( P  =   0·046). In IS patients, betaPV was found in 27 of 62 (44%) tumours; no normal skin samples were available for comparison. The most frequently found genotypes were HPV-24, HPV-15 and HPV-38. Of those tumours infected with betaPV, 28 of 57 (49%) were infected with more than one genotype (range 2–8). Tumours from IS patients were from a younger age group (mean age 57·4 years) than IC patients (mean age 73·8 years). Multiple infections were more common in tumours from IC patients (21 of 30; 70%) compared with those from IS patients (seven of 27; 26%) ( P  <   0·001). In the IC group, age did not appear to influence the distribution of single and multiple infections whereas in IS patients the proportion of multiple infections to single infections increased with age. There were no multiple infections in normal skin.
Conclusions  A wide spectrum of betaPV types was detected in our samples. Further characterization of betaPV in vivo is needed in order to determine the mechanisms by which the virus contributes to cutaneous carcinogenesis.  相似文献   
7.
Current transition assessment practices.   总被引:1,自引:0,他引:1  
Although researchers have called for a movement away from prediction-related assessments to those which identify specific skill deficits, the extent to which professionals responsible for vocational assessment have shifted their focus is uncertain. The purpose of this investigation was to assess the frequency with which specified prediction-related and skill deficit-related vocational assessment procedures were administered by a sample of secondary-level teachers and employment training specialists. Additionally, the frequency with which these professionals used assessment data to aid in decision making was determined. The results revealed that teachers and employment training personnel used a variety of assessment procedures to make transition decisions. The implications of these findings are discussed.  相似文献   
8.
The functional significance of the pars tuberalis (PT) of the mammalian adenohypophysis has remained an enigma (1, 2). One view of its function is that it acts as an auxiliary gland to support the endocrine role of the pars distalis (PD) (2), as it has been shown to contain immunocytochemically identifiable thyrotrophs and gonadotrophs (1). Many of the cells of the PT are, however, ultrastructurally unique suggesting an independent function for this tissue. Our recent demonstration that the PT of the rat is a major binding site for the ligand iodomelatonin lends further support to this idea (3). We have utilized the highly specific ligand [125l]melatonin, and have demonstrated that it binds exclusively, with very high affinity, to the PT but not the PD of the adult sheep adenohypophysis. These findings support the conclusion that the PT has a distinct role in relation to melatonin action and seasonal reproduction.  相似文献   
9.
10.
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