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   125969篇
  免费   9203篇
  国内免费   219篇
耳鼻咽喉   1136篇
儿科学   3472篇
妇产科学   2595篇
基础医学   19700篇
口腔科学   3320篇
临床医学   10617篇
内科学   25607篇
皮肤病学   2167篇
神经病学   12120篇
特种医学   5210篇
外国民族医学   9篇
外科学   15797篇
综合类   532篇
现状与发展   1篇
一般理论   106篇
预防医学   14435篇
眼科学   1970篇
药学   7405篇
中国医学   236篇
肿瘤学   8956篇
  2023年   539篇
  2022年   897篇
  2021年   1956篇
  2020年   1422篇
  2019年   2061篇
  2018年   2596篇
  2017年   2198篇
  2016年   2390篇
  2015年   2669篇
  2014年   3665篇
  2013年   4786篇
  2012年   7368篇
  2011年   7447篇
  2010年   3855篇
  2009年   4052篇
  2008年   6598篇
  2007年   6814篇
  2006年   6553篇
  2005年   6204篇
  2004年   5304篇
  2003年   5007篇
  2002年   4555篇
  2001年   4436篇
  2000年   4387篇
  1999年   3917篇
  1998年   1615篇
  1997年   1339篇
  1996年   1417篇
  1995年   1151篇
  1994年   1082篇
  1993年   979篇
  1992年   2685篇
  1991年   2408篇
  1990年   2287篇
  1989年   2141篇
  1988年   1957篇
  1987年   1710篇
  1986年   1630篇
  1985年   1557篇
  1984年   1112篇
  1983年   972篇
  1982年   526篇
  1981年   466篇
  1980年   402篇
  1979年   867篇
  1978年   526篇
  1977年   431篇
  1974年   421篇
  1973年   410篇
  1972年   370篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.

Background

The randomized EXCEL (Evaluation of XIENCE versus Coronary Artery Bypass Surgery for Effectiveness of Left Main Revascularization) trial reported a similar rate of the 3-year composite primary endpoint of death, myocardial infarction (MI), or stroke in patients with left main coronary artery disease (LMCAD) and site-assessed low or intermediate SYNTAX scores treated with percutaneous coronary intervention (PCI) and coronary artery bypass grafting (CABG). Whether these results are consistent in high-risk patients with diabetes, who have fared relatively better with CABG in most prior trials, is unknown.

Objectives

In this pre-specified subgroup analysis from the EXCEL trial, the authors sought to examine the effect of diabetes in patients with LMCAD treated with PCI versus CABG.

Methods

Patients (N = 1,905) with LMCAD and site-assessed low or intermediate CAD complexity (SYNTAX scores ≤32) were randomized 1:1 to PCI with everolimus-eluting stents versus CABG, stratified by the presence of diabetes. The primary endpoint was the rate of a composite of all-cause death, stroke, or MI at 3 years. Outcomes were examined in patients with (n = 554) and without (n = 1,350) diabetes.

Results

The 3-year composite primary endpoint was significantly higher in diabetic compared with nondiabetic patients (20.0% vs. 12.9%; p < 0.001). The rate of the 3-year primary endpoint was similar after treatment with PCI and CABG in diabetic patients (20.7% vs. 19.3%, respectively; hazard ratio: 1.03; 95% confidence interval: 0.71 to 1.50; p = 0.87) and nondiabetic patients (12.9% vs. 12.9%, respectively; hazard ratio: 0.98; 95% confidence interval: 0.73 to 1.32; p = 0.89). All-cause death at 3 years occurred in 13.6% of PCI and 9.0% of CABG patients (p = 0.046), although no significant interaction was present between diabetes status and treatment for all-cause death (p = 0.22) or other endpoints, including the 3-year primary endpoint (p = 0.82) or the major secondary endpoints of death, MI, or stroke at 30 days (p = 0.61) or death, MI, stroke, or ischemia-driven revascularization at 3 years (p = 0.65).

Conclusions

In the EXCEL trial, the relative 30-day and 3-year outcomes of PCI with everolimus-eluting stents versus CABG were consistent in diabetic and nondiabetic patients with LMCAD and site-assessed low or intermediate SYNTAX scores.(Evaluation of XIENCE versus Coronary Artery Bypass Surgery for Effectiveness of Left Main Revascularization [EXCEL]; NCT01205776)  相似文献   
2.

Introduction

The aim of this study was to evaluate the root canal shaping effect of instruments manufactured from nickel titanium, M-Wire, and Gold wire with different glide path preparation techniques.

Methods

One hundred thirty-five mesiobuccal canals of extracted human maxillary molars were randomly divided into 3 equal groups (N = 45) for glide path preparation with K-files (KF) (Dentsply Sirona, Ballaigues, Switzerland), One G (OG) files (Micro-Mega, Besançon, France), and ProGlider (PG) files (Dentsply Sirona). Specimens of each glide path group were further divided equally into 3 groups for instrumentation with ProTaper Next (PTN, Dentsply Sirona), One Shape (OS, Micro-Mega), and WaveOne Gold (WOG, Dentsply Sirona) systems (n = 15). Micro–computed tomographic imaging was used to scan teeth before instrumentation and after shaping to compare centering ratio and canal transportation values at the apical, midroot, and coronal levels and the overall changes in canal volume. Data sets were statistically analyzed (analysis of variance and Kruskal-Wallis H tests).

Results

The centering ratios for all groups were statistically similar at all levels. Apical canal transportation was significantly high for K/OS and K/PTN (P = .003). Midroot canal transportation was significantly high for K/PTN, K/OS, and OG/OS (P = .0003). Coronal canal transportation was significantly high for K/PTN and K/OS (P = .011). The highest change in canal volume was observed with all PTN groups and the lowest with PG/WOG (P = .06).

Conclusions

WOG manufactured from Gold wire combined with PG showed better root canal shaping ability and removed less dentin from the canal walls. The nickel-titanium (OS) and M-Wire (PTN) instruments used in combination with KF significantly transported more canals. PTN removed the most dentin from the canal walls regardless of the GPP technique.  相似文献   
3.
4.
Background Many breast, cervical, and colorectal cancer screening programmes were disrupted due to the COVID-19 pandemic. This study aimed to estimate the effects of five restart strategies after the disruption on required screening capacity and cancer burden.Methods Microsimulation models simulated five restart strategies for breast, cervical, and colorectal cancer screening. The models estimated required screening capacity, cancer incidence, and cancer-specific mortality after a disruption of 6 months. The restart strategies varied in whether screens were caught up or not and, if so, immediately or delayed, and whether the upper age limit was increased.Results The disruption in screening programmes without catch-up of missed screens led to an increase of 2.0, 0.3, and 2.5 cancer deaths per 100 000 individuals in 10 years in breast, cervical, and colorectal cancer, respectively. Immediately catching-up missed screens minimised the impact of the disruption but required a surge in screening capacity. Delaying screening, but still offering all screening rounds gave the best balance between required capacity, incidence, and mortality.Conclusions Strategies with the smallest loss in health effects were also the most burdensome for the screening organisations. Which strategy is preferred depends on the organisation and available capacity in a country.Subject terms: Health policy, Population screening, Cancer screening, Cancer screening  相似文献   
5.

Objectives

Triazole resistance in Aspergillus spp. is emerging and complicates prophylaxis and treatment of invasive aspergillosis (IA) worldwide. New polymerase chain reaction (PCR) tests on broncho-alveolar lavage (BAL) fluid allow for detection of triazole resistance at a genetic level, which has opened up new possibilities for targeted therapy. In the absence of clinical trials, a modelling study delivers estimates of the added value of resistance detection with PCR, and which empiric therapy would be optimal when local resistance rates are known.

Design

A decision-analytic modelling study was performed based on epidemiological data of IA, extended with estimated dynamics of resistance rates and treatment effectiveness. Six clinical strategies were compared that differ in use of PCR diagnostics (used vs not used) and in empiric therapeutic choice in case of unknown triazole susceptibility: voriconazole, liposomal amphotericin B (LAmB) or both. Outcome measures were proportion of correct treatment, survival and serious adverse events.

Results

Implementing aspergillus PCR tests was projected to result in residual treatment-susceptibility mismatches of <5% for a triazole resistance rate up to 20% (using voriconazole). Empiric LAmB outperformed voriconazole at resistance rates >5–20%, depending on PCR use and estimated survival benefits of voriconazole over LAmB. Combination therapy of voriconazole and LAmB performed best at all resistance rates, but the advantage over the other strategies should be weighed against the expected increased number of drug-related serious adverse events. The advantage of combination therapy over LAmB monotherapy became smaller at higher triazole resistance rates.

Conclusions

Introduction of current aspergillus PCR tests on BAL fluid is an effective way to increase the proportion of patients that receive targeted therapy for IA. The results indicate that close monitoring of background resistance rates and adverse drug events are important to attain the potential benefits of LAmB. The choice of strategy ultimately depends on the probability of triazole resistance, the availability of PCR and individual patient characteristics.  相似文献   
6.
7.
8.

Purpose

Most computerized adaptive testing (CAT) applications in patient-reported outcomes (PRO) measurement to date are reliability-centric, with a primary objective of maximizing measurement efficiency. A key concern and a potential threat to validity is that, when left unconstrained, individual CAT administrations could have items with systematically different attributes, e.g., sub-domain coverage. This paper aims to provide a solution to the problem from an optimal test design framework using the shadow-test approach to CAT.

Methods

Following the approach, a case study was conducted using the PROMIS® (Patient-Reported Outcomes Measurement Information System) fatigue item bank both with empirical and simulated response data. Comparisons between CAT administrations without and with the enforcement of content and item pool usage constraints were examined.

Results

The unconstrained CAT exhibited a high degree of variation in items selected from different substrata of the item bank. Contrastingly, the shadow-test approach delivered CAT administrations conforming to all specifications with a minimal loss in measurement efficiency.

Conclusions

The optimal test design and shadow-test approach to CAT provide a flexible framework for solving complex test-assembly problems with better control of their domain coverage than for the conventional use of CAT in PRO measurement. Applications in a wide array of PRO domains are expected to lead to more controlled and balanced use of CAT in the field.
  相似文献   
9.
The list of motives by Kanin (1994) is the most cited list of motives to file a false allegation of rape. Kanin posited that complainants file a false allegation out of revenge, to produce an alibi or to get sympathy. A new list of motives is proposed in which gain is the predominant factor. In the proposed list, complainants file a false allegation out of material gain, emotional gain, or a disturbed mental state. The list can be subdivided into eight different categories: material gain, alibi, revenge, sympathy, attention, a disturbed mental state, relabeling, or regret. To test the validity of the list, a sample of 57 proven false allegations were studied at and provided by the National Unit of the Dutch National Police (NU). The complete files were studied to ensure correct classification by the NU and to identify the motives of the complainants. The results support the overall validity of the list. Complainants were primarily motivated by emotional gain. Most false allegations were used to cover up other behavior such as adultery or skipping school. Some complainants, however, reported more than one motive. A large proportion, 20% of complainants, said that they did not know why they filed a false allegation. The results confirm the complexity of motivations for filing false allegations and the difficulties associated with archival studies. In conclusion, the list of Kanin is, based on the current results, valid but insufficient to explain all the different motives of complainants to file a false allegation.  相似文献   
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