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   3078篇
  免费   115篇
  国内免费   14篇
耳鼻咽喉   11篇
儿科学   14篇
妇产科学   23篇
基础医学   241篇
口腔科学   762篇
临床医学   244篇
内科学   702篇
皮肤病学   30篇
神经病学   199篇
特种医学   144篇
外科学   278篇
综合类   189篇
预防医学   116篇
眼科学   10篇
药学   175篇
中国医学   29篇
肿瘤学   40篇
  2024年   4篇
  2023年   94篇
  2022年   83篇
  2021年   141篇
  2020年   107篇
  2019年   253篇
  2018年   278篇
  2017年   141篇
  2016年   83篇
  2015年   66篇
  2014年   206篇
  2013年   178篇
  2012年   99篇
  2011年   127篇
  2010年   85篇
  2009年   102篇
  2008年   92篇
  2007年   142篇
  2006年   72篇
  2005年   78篇
  2004年   65篇
  2003年   39篇
  2002年   16篇
  2001年   25篇
  2000年   19篇
  1999年   20篇
  1998年   18篇
  1997年   15篇
  1996年   9篇
  1995年   4篇
  1994年   7篇
  1993年   31篇
  1992年   12篇
  1991年   12篇
  1990年   8篇
  1989年   12篇
  1988年   4篇
  1985年   44篇
  1984年   55篇
  1983年   29篇
  1982年   56篇
  1981年   26篇
  1980年   22篇
  1979年   24篇
  1978年   42篇
  1977年   13篇
  1976年   21篇
  1975年   46篇
  1974年   40篇
  1973年   37篇
排序方式: 共有3207条查询结果,搜索用时 15 毫秒
101.
Objective: Clinical literature was examined for evidence supporting use of CAD/CAM reconstructions and fiber‐reinforced materials. Materials and methods: Potential evidence was identified via databases [PubMed; EMBASE (R) Drugs & Pharmacology; Center for Reviews and Dissemination, University of York; Cochrane Library], hand search of non‐indexed literature, secondary reference searches, and personal contacts with clinical trial PI's. Search terms included: dental restorations; CAD/CAM; CEREC; LAVA; CERCON; Procera; inlay/onlay; dental prosthesis; fiber‐reinforced composite (FRC). Results: Two randomized‐controlled clinical trials were identified as examined in one Cochrane Collaboration review relevant to CAD/CAM inlays. One systematic review of 15 CAD/CAM inlay studies was examined. Six studies were identified of three commercial FRC endodontic posts and eight reported on FRC use for fixed denture prostheses. Fifteen ongoing prospective trials were identified studying CAD/CAM fabricated zirconia‐based prostheses. A total of 76 papers were referenced including those related to use of in vitro measures as evidence. Conclusions: Review of the Cochrane analysis raised concerns that typical RCT protocols may prove insufficient for stratification of confounding variables (patient, practitioner, material) when treatment outcomes are primarily prosthesis‐ or material‐based (not patient‐based, e.g., as in fracture). RCT designs are most straightforward when treatment outcomes are patient‐based (e.g., soft tissue changes). When treatment responses are material‐based, controls also become difficult to define and studies become tests of equivalency/superiority; where well‐stratified cohort designs are likely preferred. Large numbers of independent cohort studies support the use of CAD/CAM ceramic inlay/onlay restorations and crowns but many complications inhibit the application of high‐level systematic review. Except perhaps for fiber‐based endodontic posts, the clinical FRC literature appears insufficient for expert review. Single in vitro measures cannot currently serve as evidence for clinical practice, except in limited cases of simple function (e.g., impression material accuracy). Batteries of in vitro measures are often applied during materials development but cannot substitute for clinical study.  相似文献   
102.
Introduction: Type 2 diabetes mellitus (T2DM) is a growing and serious global health problem. Inhibition of the sodium––glucosecotransporter-2 (SGLT2) can increase urinary glucose excretion and decrease plasma glucose levels in an insulin-independent manner. Ertugliflozin is a highly selective inhibitor of SGLT2, and was approved in the US for the treatment of adults with T2DM.

Areas covered: In this paper, the mechanism of action, pharmacokinetics, clinical efficacy, safety, etc., of ertugliflozin have been introduced. Expert commentary: Ertugliflozin offers a novel, therapeutic approach to T2DM. Advantages of ertugliflozin include reduction in glycated hemoglobin, weight loss and blood pressure lowering with a low risk of hypoglycemia. The main adverse effects likely to be seen are genital fungal infections. Studies show that there is no increased risk of cardiovascular disease, but studies focusing on longer duration outcome are still essential.  相似文献   

103.
Abstract

Objective: Despite immense popularity of Jaipur foot as low cost prosthetic, not much work has been reported on its design for manufacturing standardization. Without manufacturing standardization, it cannot be mass produced using contemporary manufacturing technologies. The objective of this work is to carry out its computer aided design (CAD) followed by computer aided engineering (CAE) based on the material properties obtained from the previous work [1 Rachel HT, Kristine MF, Benjamin BW, et al. Assessment of the compressive and tensile mechanical properties of materials used in the Jaipur foot prosthesis. Prosthet Orthot Int. 2018;42:511517.[Crossref], [PubMed], [Web of Science ®] [Google Scholar]] of the authors. This may lead to the possible use of modern manufacturing processes for the Jaipur foot design.

Design: After modelling using CAD tool including its organic surfaces, the designed foot was analysed using a CAE tool for balanced standing load conditions to determine maximum stresses and deformation in its various parts. The bending analysis was done to check the dorsiflexion movement so that the strained sections could be identified for more reliable and durable prosthetic foot. For the static load analysis, base of the foot was constrained and 300–500 N load was applied through the bolt whereas for bending, the part near the bolt was fixed and pressure was applied at junction of front foot and toes.

Results: The results show that the maximum stress and deformation occur at the bolt, while the skin undergoes maximum strain. CAE analysis also proves the robustness of the Jaipur foot design and a well manufactured Jaipur foot as per standardized design should be able to withstand the real life conditions without failure. The CAD model is also used for FDM based printing for a nonfunctional prototype of Jaipur foot.
  • Implications for rehabilitation
  • The results of this study will serve as an important guideline for further research regarding equivalent material replacement, material optimization and obtaining an optimized design after studying the foot for dynamic analysis.

  相似文献   
104.
Combined injury to the anterior cruciate ligament (ACL) and meniscus is associated with earlier onset and increased rates of post-traumatic osteoarthritis compared with isolated ACL injury. However, little is known about the initial changes in joint structure associated with these different types of trauma. We hypothesized that trauma to the ACL and lateral meniscus has an immediate effect on morphometry of the articular cartilage and meniscus about the entire tibial plateau that is more pronounced than an ACL tear without meniscus injury. Subjects underwent magnetic resonance imaging scanning soon after injury and prior to surgery. Those that suffered injury to the ACL and lateral meniscus underwent changes in the lateral compartment (increases in the posterior–inferior directed slopes of the articular cartilage surface, and the wedge angle of the posterior horn of the meniscus) and medial compartment (the cartilage-to-bone height decreased in the region located under the posterior horn of the meniscus, and the thickness of cartilage increased and decreased in the mid and posterior regions of the plateau, respectively). Subjects that suffered an isolated ACL tear did not undergo the same magnitude of change to these articular structures. A majority of the changes in morphometry occurred in the lateral compartment of the knee; however, change in the medial compartment of the knee with a normal appearing meniscus also occurred. Statement of clinical significance: Knee injuries that involve combined trauma to the ACL and meniscus directly affect both compartments of the knee, even if the meniscus and articular cartilage appears normal upon arthroscopic examination. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:759-767, 2020  相似文献   
105.
In our first survey of transplant centers in March 2020, >75% of kidney and liver programs were either suspended or operating under restrictions. To safely resume transplantation, we must understand the evolving impact of COVID-19 on transplant recipients and center-level practices. We therefore conducted a six-week follow-up survey May 7-15, 2020, and linked responses to the COVID-19 incidence map, with a response rate of 84%. Suspension of live donor transplantation decreased from 72% in March to 30% in May for kidneys and from 68% to 52% for livers. Restrictions/suspension of deceased donor transplantation decreased from 84% to 58% for kidneys and from 73% to 42% for livers. Resuming transplantation at normal capacity was envisioned by 83% of programs by August 2020. Exclusively using local recovery teams for deceased donor procurement was reported by 28%. Respondents reported caring for a total of 1166 COVID-19–positive transplant recipients; 25% were critically ill. Telemedicine challenges were reported by 81%. There was a lack of consensus regarding management of potential living donors or candidates with SARS-CoV-2. Our findings demonstrate persistent heterogeneity in center-level response to COVID-19 even as transplant activity resumes, making ongoing national data collection and real-time analysis critical to inform best practices.  相似文献   
106.
(1) It is estimated that 10% of the world’s population will need a dental implant in their lifetime. Despite all the advances in the comprehension of dental implant designs, materials and techniques, traditional implants still have many limitations. Customized root-analogue implants are, therefore, gaining increased interest in dental rehabilitation and are expected to not only preserve more hard and soft tissues but also avoid a second surgery and improve patient overall satisfaction. In this sense, the aim of this review was to collect and analyse the clinical trials and case reports on customized root-analogue implants available in the literature; (2) This review was carried out according to the PRISMA Statement. An electronic database search was performed using five databases: PubMed, Google Scholar, Medline, Science Direct, and Scopus. The following keywords were used for gathering data: custom-made, dental implants, root-analogue, anatomical, customized and tooth-like; (3) 15 articles meeting the inclusion criteria—articles reporting clinical trials, case reports or animal studies and articles with root-analogue implants and articles with totally customized implant geometries—were selected for the qualitative synthesis. The design and manufacturing techniques, implant material and surface treatments were assessed and discussed; (4) The performance of some root-analogue implants with specific features (i.e., macro-retentions) was successful, with no signs of infection, periodontitis nor bleeding during the follow-up periods.  相似文献   
107.
ObjectiveSeveral microRNA (miRNA) polymorphisms have been associated with susceptibility to specific health disorders, including cardiovascular diseases. The aim of the present study was to investigate whether four well-studied miRNA polymorphisms in non-Caucasian populations, namely miR146a G>C (rs2910164), miR149 C>T (rs2292832), miR196a2 C>T (rs11614913) and miR499 A>G (rs3746444), contribute to the risk for the development of premature Coronary Artery Disease (CAD) in the Greek population.MethodsWe used a case-control study to examine these associations in 400 individuals: 200 CAD patients [including a subgroup of myocardial infraction (MI) patients] and 200 healthy controls, all of Greek origin. MiRNA polymorphisms were genotyped using three different assays: Polymerase chain reaction - restriction fragment length polymorphism (PCR-RFLP), High resolution Melting (HRM) and Sanger sequencing.ResultsTwo of these polymorphisms, miR196a2 C>T (rs11614913) and miR499 A>G (rs3746444) were found to be strongly associated with increased risk for CAD (p=0.0388 and p=0.0013, respectively) and for MI (p=0.0281 and p=0.0273, respectively). Furthermore, miR146C-miR149C-miR196T-miR499G allele combination appeared to be significantly related to CAD (p=0.0185) and MI (p=0.0337) prevalence.ConclusionsOur results suggest that at least two of the studied polymorphisms, miR196a2 C>T (rs11614913) and miR499 A>G (rs3746444), as well as the miR146C-miR149C-miR196T-miR499G allele combination could represent useful biomarkers of CAD and/or MI susceptibility in the Greek population. These special genetic characteristics, in combination with environmental factors and personal habits, might contribute to CAD and/or MI prevalence.  相似文献   
108.
ObjectiveTo evaluate the association between bezafibrate, a drug used to treat hypertriglyceridemia, and long-term cancer incidence in patients with coronary artery disease (CAD).Patients and MethodsThe study comprised 2980 patients with CAD (mean age, 60 years; 2729 [91.6%] men) who were free of cancer and were enrolled in the Bezafibrate Infarction Prevention study, a double-blind trial conducted between May 1, 1990, and January 31, 1993, in 18 cardiology departments in Israel. Patients randomized to receive 400 mg of bezafibrate (n=1486) or placebo (n=1494) daily for a median of 6.2 years (range, 4.7-7.6 years) were followed up for incidence of cancer through the Israeli National Cancer Registry and all-cause death through the Population Registry of the State of Israel until December 31, 2013. Cox proportional hazards and Fine and Gray survival models were used to assess the bezafibrate-cancer association.ResultsClinical characteristics and laboratory values were well balanced between the 2 groups at the study entry. Over a median follow-up of 22.5 years (range, 21.2-23.9 years), cancer developed in 753 patients. With death considered a competing event, the cumulative incidence of cancer at the end of the follow-up was lower in the bezafibrate vs the placebo group (23.9%; 95 CI, 21.9%-26.1% vs 27.2%; 95 CI, 25.1%-29.4%; P=.04). The hazard ratio for cancer in the bezafibrate vs placebo groups was 0.86 (95% CI, 0.74-0.99). In mediation analysis, the association between bezafibrate treatment and cancer incidence was not sensitive to adjustment for on-trial lipid levels but was attenuated on adjustment for on-trial fibrinogen levels.ConclusionBezafibrate treatment is associated with reduced risk of cancer among patients with CAD. Fibrinogen, but not lipid lowering, is linked to this association.  相似文献   
109.
ObjectiveTo assess the prevalence of atherosclerotic cardiovascular disease (ASCVD) and its individual phenotypes of coronary artery disease (CAD), peripheral artery disease (PAD), and cerebrovascular disease by age and sex in a large US cohort of hospitalized patients with systemic lupus erythematosus (SLE).MethodsA nested case-control study of adults with and without SLE was conducted from the January 1, 2008, through December 31, 2014, National Inpatient Sample. Hospitalized patients with SLE were matched (1:3) by age, sex, race, and calendar year to hospitalized patients without SLE. The prevalences of CAD, PAD, and cerebrovascular disease were evaluated, and associations with SLE were determined after adjustment for common cardiovascular risk factors.ResultsAmong the 252,676 patients with SLE and 758,034 matched patients without SLE, the mean age was 51 years, 89% were women, and 49% were white. Patients with SLE had a higher prevalence of ASCVD vs those without SLE (25.6% vs 19.2%; OR, 1.45; 95% CI, 1.44-1.47; P<.001). After multivariable adjustment, SLE was associated with a greater odds of ASCVD (adjusted odds ratio [aOR], 1.46; 95% CI, 1.41-1.51). The association between SLE and ASCVD was observed in women and men and was attenuated with increasing age. Also, SLE was associated with increased odds of CAD (aOR, 1.42; 95% CI, 1.40-1.44), PAD (aOR, 1.25; 95% CI, 1.22-1.28), and cerebrovascular disease (aOR, 1.68; 95% CI, 1.65-1.71).ConclusionIn hospitalized US patients, SLE was associated with increased ASCVD prevalence, which was observed in both sexes and was greatest in younger patients.  相似文献   
110.

Background and aims

The role of lipoprotein (a) [Lp(a)] in coronary artery diseases (CAD) with special clinical background such as type 2 diabetes mellitus (T2DM) has not been fully determined. The aim of the present study was to investigate the relation of Lp(a) to type 2 diabetic patients with or without CAD.

Methods and results

A total of 2040 consecutive patients with T2DM who received selective coronary angiography (CAG) due to angina-like chest pain were enrolled. The patients were subsequently divided into CAD and non-CAD groups according to the results of CAG. The severity of CAD was evaluated by the Gensini Score (GS), number of stenotic vessels, and history of myocardial infarction (MI). Data showed that Lp(a) levels were higher in the CAD group than in the non-CAD group (median: 15.00 mg/dL vs. 11.88 mg/dL, P = 0.025). The results from CAD subgroup analysis indicated that the patients with MI, multiple-vessel disease and high GS had higher Lp(a) levels compared with those in their matched subgroups (P < 0.05, respectively). After adjustment for confounders, Lp(a) levels were independently related to the presence and severity of CAD (CAD:OR = 1.564; MI:OR = 1.523; high GS:OR = 1.388; multiple-vessel disease:OR = 1.455; P < 0.05, respectively).

Conclusion

Elevated Lp(a) levels were independently associated with the presence and severity of CAD in patients with T2DM. More studies are necessary to confirm our findings.  相似文献   
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