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   10069篇
  免费   637篇
  国内免费   41篇
耳鼻咽喉   69篇
儿科学   230篇
妇产科学   173篇
基础医学   1328篇
口腔科学   289篇
临床医学   765篇
内科学   2273篇
皮肤病学   186篇
神经病学   805篇
特种医学   977篇
外科学   1704篇
综合类   68篇
一般理论   1篇
预防医学   544篇
眼科学   145篇
药学   512篇
  1篇
中国医学   8篇
肿瘤学   669篇
  2023年   106篇
  2022年   230篇
  2021年   367篇
  2020年   230篇
  2019年   279篇
  2018年   343篇
  2017年   205篇
  2016年   285篇
  2015年   332篇
  2014年   389篇
  2013年   419篇
  2012年   644篇
  2011年   615篇
  2010年   425篇
  2009年   343篇
  2008年   516篇
  2007年   527篇
  2006年   526篇
  2005年   525篇
  2004年   421篇
  2003年   358篇
  2002年   353篇
  2001年   118篇
  2000年   111篇
  1999年   113篇
  1998年   91篇
  1997年   94篇
  1996年   67篇
  1995年   53篇
  1994年   61篇
  1993年   48篇
  1992年   55篇
  1991年   64篇
  1990年   74篇
  1989年   48篇
  1988年   46篇
  1987年   59篇
  1986年   39篇
  1985年   48篇
  1984年   42篇
  1983年   28篇
  1982年   26篇
  1981年   35篇
  1979年   29篇
  1978年   27篇
  1977年   27篇
  1975年   24篇
  1974年   30篇
  1932年   36篇
  1923年   26篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
Background: A deeper joint socket (concave incongruity) is found at most angles of flexion of the humero-ulnar joint and maintained over a wide range of physiological loading. It is, however, unclear how far this incongruity affects the distribution of load and subchondral mineralization of this joint as compared with a congruous configuration. Methods: Two nonlinear, axisymmetrical finite element models with two cartilage layers were constructed, one congruous and one incongruous, with a joint space of realistic magnitude. The distribution of subchondral mineralization was determined by computed tomography osteoabsorptiometry in the same six specimens that were investigated in the first part of the study, and compared with the biomechanical data obtained there and the predictions of the models. Results: In the congruous case, the center of the socket is highly loaded, whereas the periphery does not experience mechanical stimulation. A central bone density maximum is predicted. With concave incongruity the position of the contact areas shifts from the joint margin towards the center as the load increases, and the peak stresses are considerably lower. A bicentric ventro-dorsal distribution pattern of subchondral mineralization is predicted, and this is actually found in the six specimens. Conclusions: Concave incongruity is shown to determine load transmission and subchondral mineralization of the humero-ulnar joint. It is suggested that this shape leads to a more even distribution of stress, provides intermittent stimulation of the cartilaginous tissue, and has beneficial effects on the metabolism, nutrition, and lubrication of the articular cartilage during cyclic loading. © 1995 Wiley-Liss, Inc.  相似文献   
42.
Felix  S. B.  Baumann  G.  Hashemi  T.  Niemczyk  M.  Ochsenfeld  G.  Ahmad  Z.  Shirani  S.  Blömer  H. 《Inflammation research》1991,33(3-4):349-358
Summary In vivo anaphylaxis is associated with respiratory distress and cardiovascular failure. The present investigation was designed to further characterize respiratory and cardiac anaphylactic events. In guinea pigs, sensitization was produced by subcutaneous application of ovalbumin together with Freund's adjuvant. Fourteen days after sensitization, the effects of an intravenous infusion of ovalbumin were tested in the anesthetized artificially ventilated guinea pigs. The renewed application of the antigen induced an initial increase of left ventricular pressure which was followed by a rapid decrease 5 min after antigenic challenge. Enddiastolic left ventricular pressure increased within 3 min, thus indicating left ventricular pump failure. In the same time range, ECG recordings uniformly showed signs of acute myocardial ischemia. In addition, heart rate steadily decreased. All animals died within 15 min. Simultaneously with cardiac anaphylactic malfunction, severe arterial hypoxia and carbon dioxide retention occurred, revealing respiratory distress.Histamine is known as a potent bronchoconstrictor via histamine H1-receptor stimulation. Administration of H1-recpetor antagonists to improve respiration may therefore provide further information on the contribution of pulmonary malfunction to anaphylactic cardiovascular shock. Therefore, additional experiments were performed with sensitized guinea pigs pretreated with the histamine H1-receptor blocker mepyramine. In these experiments the antigenic challenge induced a dissociation of cardiac and respiratory manifestation of anphylaxis. Despite inhibition of hypoxia and carbon dioxide retention, left ventricular pump failure and occurrence of myocardial ischemia were delayed but not suppressed.It is concluded that histamine is an important mediator of anaphylactic respiratory distress. However, vasoactive anaphylactic mediators other than histamine are primarily involved in anaphylactic cardiac malfunction occurring during the later phase of systemic anaphylaxis.Supported by grant Fe 250/1-1 from the Deutsche Forschungsgemeinschaft (DFG).  相似文献   
43.
Journal of Public Health - The purpose of this paper is to investigate the implementation of value-based care principles in the context of frailty in the perioperative process, highlighting the...  相似文献   
44.
Despite efforts to promote infant and young child feeding (IYCF) practices, there is no collective review of evidence on IYCF enablers and barriers in India. This review was conducted using 2015 Preferred Reporting Items for Systematic reviews and Meta-Analysis (PRISMA) guidelines. Six computerized bibliographic databases, Scopus, PubMed, PsycINFO, CINAHL, Embase, and Ovid MEDLINE, were searched for published studies on factors associated with IYCF practices in India from 1 January 1993, to 30 April 2020. IYCF practices examined were early initiation of breastfeeding, exclusive breastfeeding, continued breastfeeding at one year, introduction to solid semi-solid or soft foods, minimum dietary diversity, minimum meal frequency, minimum acceptable diet, continued breastfeeding at two years, predominant breastfeeding, and bottle feeding. In total, 6968 articles were retrieved, and 46 studies met the inclusion criteria. The common enablers of IYCF were higher maternal socioeconomic status (SES) and more frequent antenatal care visits (ANC) (≥3). Common barriers to IYCF practices were low SES and less frequent ANC. The review showed that the factors associated with IYCF practices in India are largely modifiable and multi-factorial. Improving IYCF practices would require the adoption of both facilities- and community-based policy interventions at the subnational and national levels in India.  相似文献   
45.
INTRICATE is a prospective double-blind placebo-controlled feasibility study, assessing the influence of combined vitamin K2 and vitamin D3 supplementation on micro-calcification in carotid artery disease as imaged by hybrid Sodium [18F]Fluoride (Na[18F]F) positron emission tomography (PET)/ magnetic resonance imaging (MRI). Arterial calcification is an actively regulated process and results from the imbalance between calcification promoting and inhibiting factors. Considering the recent advancements in medical imaging, ultrasound (US), PET/MRI, and computed tomography (CT) can be used for the selection and stratification of patients with atherosclerosis. Fifty-two subjects with asymptomatic carotid artery disease on at least one side of the neck will be included in the study. At baseline, an Na[18F]F PET/MRI and CT examination will be performed. Afterwards, subjects will be randomized (1:1) to a vitamin K (400 µg MK-7/day) and vitamin D3 (80 µg/day) or to placebo. At the 3-month follow-up, subjects will undergo a second Na[18F]F PET/MRI and CT scan. The primary endpoint is the change in Na[18F]F PET/MRI (baseline vs. after 3 months) in the treatment group as compared to the placebo arm. Secondary endpoints are changes in plaque composition and in blood-biomarkers. The INTRICATE trial bears the potential to open novel avenues for future large scale randomized controlled trials to intervene in the plaque development and micro-calcification progression.  相似文献   
46.
International Urology and Nephrology - To test the value of preoperative and postoperative cystatin C (CysC) as a predictor on kidney function after partial (PN) or radical nephrectomy (RN) in...  相似文献   
47.
BackgroundAccurate preoperative planning is a key component of successful total hip arthroplasty (THA). The purpose of the present study was to compare the accuracy and reliability of three-dimensional (hipEOS) and common digital two-dimensional (TraumaCad) templating with special focus on stem morphology.Methods51 patients undergoing THA were randomized to two groups. Preoperative planning was performed on 23 patients with hipEOS (3D) and on 28 patients with TraumaCad (2D) planning software. Planning results were compared with the implanted component size. Inter- and intraobserver reliability as well as planning accuracy of both planning methods with special focus on straight and short stem design were recorded.ResultsIntraobserver reliability of both planning methods was good for component planning (ICC2,1: 0.835-0.967). Interobserver ICC2,1 for stem and cup planning were higher for 3D templating (3D ICC2,1: 0.906-0.918 vs. 2D ICC2,1: 0.835-0.843). Total stem and cup size predictions were within 2 sizes for 3D and within 3 sizes for 2D planning. Comparing short stem planning accuracy of both planning methods, absolute difference between implanted and planned component size was significantly lower in 3D planning (P = .029). There was no significant difference in straight stem (P = .935) and cup (P = .954) planning accuracy.ConclusionOur findings suggest that 3D templating with hipEOS software has a good overall reliability and may have a better planning accuracy of short stem prostheses than digital templating with TraumaCad software. Assuming that the number of implanted short stem prostheses will further increase in coming years, a more precise planning with 3D technique can contribute to improve surgery outcome.  相似文献   
48.
Introduction It has been demonstrated that urinary neutrophil gelatinase-associated lipocalin (NGAL) and calprotectin are helpful biomarkers in the differentiation of intrinsic and prerenal acute kidney injury.Objective The present cross-sectional study investigates, whether urinary biomarkers are able to differentiate primarily inflammatory from non-inflammatory entities in chronic kidney disease (CKD).Methods Urinary calprotectin, NGAL, and kidney injury molecule-1 (KIM-1) concentrations were assessed in a study population of 143 patients with stable CKD and 29 healthy controls. Stable renal function was defined as an eGFR fluctuation ≤5 ml/min/1.73 m2 in the past 12 months. Pyuria, metastatic carcinoma, and renal transplantation were regarded as exclusion criteria. Diabetic nephropathy, hypertensive nephropathy, and polycystic kidney disease were categorized as ‘primarily non-inflammatory renal diseases’ (NIRD), whereas glomerulonephritis and vasculitis were regarded as ‘primarily inflammatory renal diseases’ (IRD).Results Urinary calprotectin and NGAL concentrations significantly differed between CKD and healthy controls (p < 0.05 each), whereas KIM-1 concentrations did not (p = 0.84). The three biomarkers did neither show significant differences in-between the individual entities, nor the two categories of IRD vs. NIRD (calprotectin 155.7 vs. 96.99 ng/ml; NGAL 14 896 vs. 11 977 pg/ml; KIM-1 1388 vs. 1009 pg/ml; p > 0.05 each). Albumin exceeds the diagnostic power of the investigated biomarkers by far.Conclusions The urinary biomarkers calprotectin, NGAL, and KIM-1 have no diagnostic value in the differentiation of primarily inflammatory vs. non-inflammatory etiologies of CKD.  相似文献   
49.
50.
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