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   1651篇
  免费   129篇
  国内免费   2篇
耳鼻咽喉   9篇
儿科学   57篇
妇产科学   30篇
基础医学   267篇
口腔科学   13篇
临床医学   222篇
内科学   340篇
皮肤病学   18篇
神经病学   134篇
特种医学   53篇
外科学   152篇
综合类   19篇
一般理论   2篇
预防医学   177篇
眼科学   35篇
药学   91篇
中国医学   2篇
肿瘤学   161篇
  2023年   13篇
  2022年   17篇
  2021年   27篇
  2020年   13篇
  2019年   17篇
  2018年   22篇
  2017年   23篇
  2016年   20篇
  2015年   20篇
  2014年   44篇
  2013年   64篇
  2012年   106篇
  2011年   88篇
  2010年   56篇
  2009年   48篇
  2008年   83篇
  2007年   75篇
  2006年   72篇
  2005年   102篇
  2004年   85篇
  2003年   82篇
  2002年   105篇
  2001年   44篇
  2000年   62篇
  1999年   42篇
  1998年   22篇
  1997年   22篇
  1996年   16篇
  1995年   11篇
  1994年   16篇
  1993年   14篇
  1992年   35篇
  1991年   29篇
  1990年   26篇
  1989年   31篇
  1988年   28篇
  1987年   12篇
  1986年   16篇
  1985年   9篇
  1984年   8篇
  1983年   9篇
  1981年   11篇
  1980年   10篇
  1979年   8篇
  1978年   10篇
  1977年   10篇
  1973年   7篇
  1972年   7篇
  1969年   8篇
  1968年   10篇
排序方式: 共有1782条查询结果,搜索用时 15 毫秒
21.
Objective To assess serum lipid and lipoprotein concentrations and oral glucose tolerance in postmenopausal women treated with 17β-oestradiol (2 mg/day) and cyclical dydrogesterone (10 mg/day for 14 days per 28 day cycle).
Design A 24 month prospective study of 29 women acting as their own controls. On-treatment samples were taken during the combined (oestrogen–progestogen) phase of therapy.
Setting Metabolic research unit in London.
Population Postmenopausal women with no previous exposure to hormone replacement therapy attending a menopause clinic in a London hospital.
Methods Fasting serum sampling and oral glucose tolerance testing.
Main outcome measures Serum lipids and lipoprotein concentrations and plasma glucose, insulin and C-peptide responses to an oral glucose load.
Results Restricting the analysis to the 17 women who completed the study, no effect was seen on serum triglyceride concentrations. There was a mean fall of 5.9% (95% CI 1.2 to −13.0) in concentrations of serum total cholesterol, reflecting the balance of a 10.7% fall (95% CI 4.3 to −25.8) in low density lipoprotein cholesterol concentrations and a 16.3% increase (95% CI 7.3 to −25.3) in those of high density lipoproteins. Fasting glucose concentrations and glucose tolerance test responses were unchanged. Fasting insulin concentrations fell substantially (–41.6%, 95% CI −23.4 to −59.8) with falls also being seen in insulin responses to glucose. Fasting C-peptide concentrations increased by 36.2% (95% CI 9.17 to 63.3), with no consistent effect on C-peptide responses to glucose.
Conclusions Dydrogesterone did not appear to oppose the potentially beneficial effects of oestradiol on insulin or either low or high density lipoproteins, making the combination with 17β-oestradiol a potentially useful option for postmenopausal women particularly those at risk of cardiovascular disease or diabetes mellitus.  相似文献   
22.
Objective To define the metabolic profile of postmenopausal hormone replacement therapies when delivered through gels, patches, implants or other non-oral routes. Such information may be useful in the absence of reliable clinical data on the effects of these therapies on the risk of cardiovascular disease.
Design and methods Selective literature review.
Patients Postmenopausal women.
Results Non-oral oestrogen therapies fail to invoke the hepatic response associated with oral therapy. Changes in hepatic protein synthesis are minimal and so plasma levels of binding globulins and other proteins tend to be normal. Many of the perturbations of the haemostatic system seen with oral therapy are avoided. In the absence of hepatic over-synthesis of apolipoproteins, plasma lipoprotein levels are unchanged or reduced. The direct effects of oestrogen on vascular function are apparent when the hormone is administered non-orally.
Conclusions The net effect of non-oral oestrogen therapies on the risk of cardiovascular disease is difficult to predict on the basis of current data. Some changes in plasma lipoprotein levels, such as the reduced fasting levels of triglycerides, would be considered desirable, but the cardioprotective increase in levels of high-density lipoproteins is absent. The differential effect on haemostasis markers is promising, but preliminary data relating to transdermal patches fail to support the idea that non-oral therapies will avoid the increased risk of venous thromboembolism associated with oral therapy. The ability of non-oral therapies to improve vascular function implies that they will offer postmenopausal women at least some of the cardiovascular protection seen with oral therapy.  相似文献   
23.
Enzymatic mild acidolysis lignins (EMAL) isolated from different species of softwood and Eucalyptus globulus were submitted to comparative analysis that included thioacidolysis, derivatization followed by reductive cleavage (DFRC), and DFRC followed by quantitative (31)P NMR (DFRC/(31)P NMR). While gas chromatography (GC) was used to determine the monomer yields from both thioacidolysis and DFRC, (31)P NMR studies quantified the various phenolic hydroxy groups released by DFRC. The monomer yields from thioacidolysis and DFRC were substantially different, with thioacidolysis resulting in higher yields. In contrast, an excellent agreement was obtained in the total number of beta-aryl ether structures determined by thioacidolysis and DFRC/(31)P NMR, indicating that the combination of DFRC with quantitative (31)P NMR overcomes, at least in part, the limitations presented by the DFRC method. Both thioacidolysis and DFRC/(31)P NMR were further used to better understand the lignin isolation process from wood. The results show that mild rotary ball milling minimizes, but does not prevent, the degradation of beta-O-4 structures during the early stages of wood pulverization. The extent of such degradation was found to be higher for E. globulus than for a variety of softwoods examined. Furthermore, the structures of the EMALs isolated at yields ranging from 20% to 62% were very similar, indicating structural homogeneity in the lignin biopolymer within the secondary wall.  相似文献   
24.
25.
PurposeTo describe in detail British Columbia (BC) Cancer Agency (BCCA) Provincial Prostate Brachytherapy (PB) Quality Assurance (QA) Program.Methods and MaterialsThe BCCA PB Program was established in 1997. It operates as one system, unified and supported by electronic and information systems, making it a single PB treatment provider for province of BC and Yukon. To date, >4000 patients have received PB (450 implants in 2011), making it the largest program in Canada. The Program maintains a large provincial prospective electronic database with records on all patients, including disease characteristics, risk stratification, pathology, preplan and postimplant dosimetric data, follow-up of prostate-specific antigen, and toxicity outcomes.ResultsQA was an integral part of the program since its inception. A formal QA Program was established in 2002, with key components that include: unified eligibility criteria and planning system, comprehensive database, physics and oncologist training and mentorship programs, peer review process, individual performance outcomes and feedback process, structured continuing education and routine assessment of the program's dosimetry, toxicity and prostate-specific antigen outcomes, administration and program leadership that promotes a strong culture of patient safety. The emphasis on creating a robust, broad-based network of skilled providers has been achieved by the program's requirements for training, education, and the QA process.ConclusionsThe formal QA process is considered a key factor for the success of cancer control outcomes achieved at BCCA. Although this QA model may not be wholly transferable to all PB programs, some of its key components may be applicable to other programs to ensure quality in PB and patient safety.  相似文献   
26.
The aim of the present study was to review the English language literature on the topic of prostate‐specific antigen bounce after brachytherapy and present a summary of the current knowledge. Although ultimately prostate‐specific antigen is a reliable measure of success after prostate brachytherapy, it can be very misleading in the first 3 years because of the frequency with which temporary benign rises in prostate‐specific antigen occur. We have reviewed the English language literature on the topic of prostate‐specific antigen bounce under the following headings: prostate neoplasms, brachytherapy, biochemical definition of prostate‐specific antigen failure, “benign prostate‐specific antigen bounce” and “prostate‐specific antigen spike”. We included brachytherapy delivered as either low dose rate or high dose rate, and either as monotherapy or as a boost combined with external beam radiotherapy. A benign self‐limited rise in prostate‐specific antigen after prostate brachytherapy is seen in an average of 35% of patients, but increases in frequency with younger age. In patients aged less than 55 years, it is observed in up to 68%. Other factors, such as sexual activity, dose, prostate volume and the use of high dose rate versus low dose rate have been implicated in affecting the frequency of the benign bounce. Benign increases in prostate‐specific antigen are frequent after prostate brachytherapy. It is important to recognize and correctly diagnose this phenomenon in order to avoid unnecessary salvage treatment.  相似文献   
27.
Macrophages are a heterogeneous cell type implicated in injury, repair, and fibrosis after AKI, but the macrophage population associated with each phase is unclear. In this study, we used a renal bilateral ischemia-reperfusion injury mouse model to identify unique monocyte/macrophage populations by differential expression of Ly6C in CD11b+ cells and to define the function of these cells in the pathophysiology of disease on the basis of microarray gene signatures and reduction strategies. Macrophage populations were isolated from kidney homogenates by fluorescence-activated cell sorting for whole genome microarray analysis. The CD11b+/Ly6Chigh population associated with the onset of renal injury and increase in proinflammatory cytokines, whereas the CD11b+/Ly6Cintermediate population peaked during kidney repair. The CD11b+/Ly6Clow population emerged with developing renal fibrosis. Principal component and hierarchical cluster analyses identified gene signatures unique to each population. The CD11b+/Ly6Cintermediate population had a distinct phenotype of wound healing, confirmed by results of studies inhibiting the macrophage colony-stimulating factor 1 receptor,whereas the CD11b+/Ly6Clow population had a profibrotic phenotype. All populations, including the CD11b+/Ly6Chigh population, carried differential inflammatory signatures. The expression of M2-specific markers was detected in both the CD11b+/Ly6Cintermediate and CD11b+/Ly6Clow populations, suggesting these in vivo populations do not fit into the traditional classifications defined by in vitro systems. Results of this study in a renal ischemia-reperfusion injury model allow phenotype and function to be assigned to CD11b+/Ly6C+ monocyte/macrophage populations in the pathophysiology of disease after AKI.  相似文献   
28.
Thirty-one primary total elbow replacements were implanted in 25 patients with rheumatoid arthritis between 2000 and 2004 by a surgeon. Twenty-six implants were GSB III. Seven were Coonrad–Morrey prostheses. The mean age of the patients was 70 years (40–88); 18 women, 6 men. DASH scores were recorded pre-operatively and at their latest review. Patients were also assessed according to the Mayo elbow performance score post-operatively. Mean follow-up was 29 months (8–55). The mean improvement in DASH (disabilities of the arm, shoulder and hand) was 25 (+6 to −45). The mean Mayo score (Corectly is the Mayo Elbow Score, there is also a Mayo liver score and other scores prposed in this center) was 85 (15–100). One implant was removed following deep infection (3%). One implant has been revised secondary to ulnar component fracture. Our overall major complication rate was 7%.  相似文献   
29.
Fractures are common in childhood with incidence maximal during puberty, around the time of peak height velocity. The relationships between single nucleotide polymorphisms (SNPs) in COL1A1 and COL1A2, bone mass acquisition, and childhood fractures are unclear.We recruited 394 children and adolescents aged 4 to 16 years into a noninterventional case control study. All had suffered an episode of trauma leading to hospital presentation; 205 had sustained a fracture. We determined the frequency of COL1A1 Sp1 and COL1A2 PvuII SNPs. Lumbar spine dual-energy X-ray absorptiometry (DXA) measurements were compared between fracture and control groups according to genotype. Subgroup analyses were performed according to sex, pubertal status, and site of injury.We found that the COL1A2 ‘PP’ genotype approximately halved the odds of fracture in the study group as a whole (OR = 0.45 [95% CI = 0.24–0.82], p = 0.01). In particular, possession of the same genotype by subjects who had not yet progressed beyond midpuberty was associated with reduced odds of fracture (OR = 0.38 [95% CI = 0.19–0.79], p = 0.01) and significantly increased lumbar spine bone mineral content (p = 0.03) and areal bone mineral density (p = 0.007). The COL1A1 Sp1 binding site ‘s’ allele was associated with a trebling of the odds of fracture in prepubertal children (OR = 3.1 [95% CI = 1.43–6.61], p = 0.004), but there was no association with any DXA measures.This is the first paediatric study to our knowledge that shows an association of the COL1A2 PvuII restriction site ‘PP’ genotype with a reduced risk of fracture and of the COL1A1 Sp1 binding site ‘s’ allele with an increased risk. The association of these variants with fracture risk is greatest during periods of predominantly appendicular bone growth.  相似文献   
30.
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