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   5277篇
  免费   451篇
  国内免费   51篇
耳鼻咽喉   14篇
儿科学   220篇
妇产科学   76篇
基础医学   587篇
口腔科学   89篇
临床医学   606篇
内科学   1096篇
皮肤病学   90篇
神经病学   389篇
特种医学   311篇
外科学   636篇
综合类   199篇
一般理论   3篇
预防医学   492篇
眼科学   151篇
药学   336篇
中国医学   11篇
肿瘤学   473篇
  2022年   41篇
  2021年   108篇
  2020年   57篇
  2019年   117篇
  2018年   95篇
  2017年   71篇
  2016年   108篇
  2015年   110篇
  2014年   149篇
  2013年   272篇
  2012年   262篇
  2011年   260篇
  2010年   184篇
  2009年   159篇
  2008年   227篇
  2007年   257篇
  2006年   254篇
  2005年   239篇
  2004年   234篇
  2003年   233篇
  2002年   178篇
  2001年   191篇
  2000年   152篇
  1999年   127篇
  1998年   103篇
  1997年   83篇
  1996年   75篇
  1995年   60篇
  1994年   62篇
  1993年   70篇
  1992年   69篇
  1991年   72篇
  1990年   63篇
  1989年   86篇
  1988年   63篇
  1987年   81篇
  1986年   48篇
  1985年   49篇
  1984年   38篇
  1983年   38篇
  1982年   32篇
  1981年   27篇
  1980年   32篇
  1978年   29篇
  1977年   38篇
  1976年   31篇
  1975年   33篇
  1974年   30篇
  1972年   36篇
  1970年   27篇
排序方式: 共有5779条查询结果,搜索用时 15 毫秒
71.
Rice bran exhibits chemopreventive properties that may help to prevent colorectal cancer (CRC), and a short-term rice bran dietary intervention may promote intestinal health via modification of the intestinal microbiota. We conducted a pilot, double-blind, randomised placebo-controlled trial to assess the feasibility of implementing a long-term (24-week) rice bran dietary intervention in Chinese subjects with a high risk of CRC, and to examine its effects on the composition of their intestinal microbiota. Forty subjects were randomised into the intervention group (n = 19) or the control group (n = 20). The intervention participants consumed 30 g of rice bran over 24-h intervals for 24 weeks, whilst the control participants consumed 30 g of rice powder on the same schedule. High rates of retention (97.5%) and compliance (≥91.3%) were observed. No adverse effects were reported. The intervention significantly enhanced the intestinal abundance of Firmicutes and Lactobacillus, and tended to increase the Firmicutes/Bacteroidetes ratio and the intestinal abundance of Prevotella_9 and the health-promoting Lactobacillales and Bifidobacteria, but had no effect on bacterial diversity. Overall, a 24-week rice bran dietary intervention was feasible, and may increase intestinal health by inducing health-promoting modification of the intestinal microbiota. Further larger-scale studies involving a longer intervention duration and multiple follow-up outcome assessments are recommended.  相似文献   
72.
Osteoporosis is a systemic skeletal disease characterized by low bone mass and bone structural deterioration that may result in fragility fractures. Use of bone imaging modalities to accurately predict fragility fractures is always an important issue, yet the current gold standard of dual-energy X-ray absorptiometry (DXA) for diagnosis of osteoporosis cannot fully satisfy this purpose. The latest high-resolution peripheral quantitative computed tomography (HR-pQCT) is a three-dimensional (3D) imaging device to measure not only volumetric bone density, but also the bone microarchitecture in a noninvasive manner that may provide a better fracture prediction power. This systematic review and meta-analysis was designed to investigate which HR-pQCT parameters at the distal radius and/or distal tibia could best predict fragility fractures. A systematic literature search was conducted in Embase, PubMed, and Web of Science with relevant keywords by two independent reviewers. Original clinical studies using HR-pQCT to predict fragility fractures with available full text in English were included. Information was extracted from the included studies for further review. In total, 25 articles were included for the systematic review, and 16 articles for meta-analysis. HR-pQCT was shown to significantly predict incident fractures and/or major osteoporotic fractures (MOFs). Of all the HR-pQCT parameters, our meta-analysis revealed that cortical volumetric bone mineral density (Ct.vBMD), trabecular thickness (Tb.Th), and stiffness were better predictors. Meanwhile, HR-pQCT parameters indicated better performance in predicting MOFs than incident fractures. Between the two standard measurement sites of HR-pQCT, the non-weight-bearing distal radius was a more preferable site than distal tibia for fracture prediction. Furthermore, most of the included studies were white-based, whereas very few studies were from Asia or South America. These regions should build up their densitometric databases and conduct related prediction studies. It is expected that HR-pQCT can be used widely for the diagnosis of osteoporosis and prediction of future fragility fractures. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).  相似文献   
73.
IntroductionThe difference in outcome between right (RCD) and left colonic diverticulitis (LCD) is not well established. The aim of this study was to analyse the presentation and surgical outcome of RCD versus left-sided disease following emergency surgery.MethodWe conducted a retrospective review of patients presenting with acute diverticulitis over a 10-year period from 2004 to 2014 to a tertiary unit. Patient demographics, Hinchey classification, need for emergency surgery, perioperative outcome and recurrence were evaluated.ResultsIn total 360 patients presented with acute diverticulitis, 218 (61%) were right-sided and 142 (39%) were left-sided. The mean age (57 yrs vs 68 yrs) and median length of stay (4 days vs 5 days) were significantly less in RCD (p < 0.001). The need for emergency surgery was similar between RCD and LCD (30.7% vs 23.2%, p = 0.12). Sixty-seven (31%) patients with RCD required emergency surgery, 42 (62.7%) of these were based on a presumptive diagnosis of appendicitis and underwent laparoscopic appendicectomy only. Operative morbidity (10.4% vs 51.5%, p < 0.001) and mortality were significantly higher in LCD (1.5% v 15.2%, p = 0.007). Subgroup analysis of non-appendicectomy, RCD patients, showed LCD were more likely to require surgery (11.5% vs 23.2%, p = 0.003). There was no difference in recurrence (p = 0.6).ConclusionRight colonic diverticulitis patients are younger and disease course is more benign compared to LCD. Presentation can be confused with appendicitis without proper imaging. In the rare cases where emergency surgery is required, RCD is associated with a lower operative morbidity and mortality compared to left-sided disease.  相似文献   
74.
M D Law  J Speck  J W Moyer 《Virology》1992,188(2):732-741
The nucleotide sequence of Impatiens necrotic spot virus (INSV) M RNA was determined from cDNA clones. The INSV M RNA was 4972 nucleotides in length with two open reading frames (ORFs) in an ambisense genomic organization. The larger ORF near the 3' end of the viral RNA, coding for a protein with a predicted molecular weight of 124.9 kDa, was in the viral complementary sense and produced the G2 and G1 proteins. A smaller ORF in the viral sense was capable of coding for a 34.1-kDa polypeptide, designated the NSm protein. Two subgenomic RNA species were detected in INSV-infected tissue that corresponded to the predicted sizes (3.3 and 1.0 kb) of the G2-G1 and NSm mRNAs. The ORFs were separated by a 478 nucleotide A-U-rich intergenic region similar to the regions found in other viral RNAs with ambisense ORFs. The intergenic region was predicted to form a stable stem-loop structure (-81.2 kcal/mole). The ambisense genomic organization is characteristic of the S RNA for members of the Phlebovirus, Uukuvirus, and Tospovirus genera in the Bunyaviridae family. This is the first report of an ambisense Bunyaviridae M RNA.  相似文献   
75.
76.
The results of a national survey which examined current computer usage and occupational therapist direct entry of Workload Measurement Data is presented. Results indicated an almost equal distribution of departments using computers versus not using computers. A variety of software packages are used for the purposes of collecting workload measurement data, but the majority of departments use customized in-house programmes. The most common method of data entry was a clerk in a central location, however, a number of departments are considering a switch to therapist direct entry. Advantages and disadvantages of both methods were described by survey respondents.  相似文献   
77.
Multifocal atrial tachycardia is a difficult clinical problem generally associated with acute cardiorespiratory illness. The purpose of this study was to assess the feasibility and clinical utility of atrioventricular junction ablation plus permanent transvenous pacemaker implantation as therapy for uncontrolled refractory multifocal atrial tachycardia. Three patients with uncontrolled refractory multifocal atrial tachycardia underwent atrioventricular junction ablation plus permanent transvenous pacemaker implantation. Complications and outcome of each procedure was monitored and both objective and subjective assessment of physical functional capacity was assessed by a semiquantitative examination. Ablation procedures controlled the ventricular response in all patients. There were no complications related to the ablation procedure or implantation of permanent transvenous pacing system. All patients demonstrated subjective improvement in symptoms. Palpitations were virtually eradicated in these patients and all enjoyed significant improvements in rest and effort dyspnea, exercise tolerance and asthenia. Objective assessment of functional class also demonstrated significant improvements. Atrioventricular ablation plus permanent transvenous pacing offers a safe and effective therapy for uncontrolled refractory multifocal atrial tachycardia.  相似文献   
78.
During the past 15 years, occupational therapists in Canada, through the Canadian Association of Occupational Therapists, have worked to develop and implement guidelines for practice of a client-centred approach to occupational therapy. One of the difficulties with the current Guidelines for the Client-Centred Practice of Occupational Therapy is the lack of a definition and discussion of the concepts and issues fundamental to client-centred practice. In this paper, key concepts of client-centred practice: individual autonomy and choice, partnership, therapist and client responsibility, enablement, contextual congruence, accessibility and respect for diversity are discussed. Two practice examples are used to illustrate these ideas and raise issues about obstacles to the practice of client-centred occupational therapy. Research evidence about the effectiveness of client-centred concepts in enhancing client satisfaction, functional outcomes and adherence to health service programmes is reviewed.  相似文献   
79.
Indications of surgical treatment for lesions in the central nervous system depend on the risk of a definitive neurological deficit, related to the benefit of resection. Detection of eloquent areas is then necessary because of major individual variability. Neuro-imaging functional techniques are in development and are beginning to be efficient for cortical sensorymotor mapping, but still lack sensitivity and specificity for language mapping, and remain unable to give real-time data during surgery and to perform sub-cortical mapping. The more precise and reliable method of functional mapping is represented by the intra-operative direct electrical stimulations (DES), which allow identification and preservation of essential pathways for motricity, sensibility and language, at each level of the central nervous system (cortico-subcortical). We report our experience of DES in the surgery of tumours and vascular malformations located in supra-tentorial brain eloquent areas, with a consecutive series of 60 patients operated on under general or local anaesthesia, from November 1996 until May 1999 in our department at La Salpêtrière Hospital. Presenting symptoms in the 60 subjects (39 males, 21 females, mean age: 45 years) were seizures in 37 cases with normal clinical examination, and mild neurological deficit in 29 cases. MRI showed 60 supra-tentorial brain lesions: 30 precentral, 12 postcentral, 14 perisylvian in the dominant hemisphere, 4 deep-seated. All subjects underwent surgical resection using DES, with supratentorial cortico-subcortical mapping under general anaesthesia for motor areas detection in 43 cases and under local anaesthesia for sensori-motor and/or language tasks in 17 cases. The final histological diagnosis was 44 gliomas (31 low-grade and 13 high-grade), 9 metastasis, 3 cavernomas, 4 arteriovenous malformations (AVM). Resection was total or subtotal in 52 cases (87%) and partial in 8 cases (13%). 29 patients had no post-operative deficit, while the other 31 patients were impaired post-operatively, with in all cases, except 3, a complete recovery delayed for 15 days to 3 months (overall morbidity: 5%). The median follow up was 14 months. Intra-operative direct electrical stimulations of the central nervous system constitute a reliable, precise and safe method, allowing the realization of a functional mapping useful for all operations of lesions located in eloquent areas. This technique allows a minimization of definitive post-operative neurological deficit, and concurrently an improvement in the quality of resection.  相似文献   
80.
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