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   23892篇
  免费   1485篇
  国内免费   55篇
耳鼻咽喉   291篇
儿科学   834篇
妇产科学   646篇
基础医学   3549篇
口腔科学   471篇
临床医学   2819篇
内科学   4254篇
皮肤病学   695篇
神经病学   2434篇
特种医学   786篇
外国民族医学   2篇
外科学   2185篇
综合类   203篇
现状与发展   1篇
一般理论   40篇
预防医学   2658篇
眼科学   432篇
药学   1455篇
中国医学   23篇
肿瘤学   1654篇
  2023年   165篇
  2022年   128篇
  2021年   497篇
  2020年   324篇
  2019年   501篇
  2018年   534篇
  2017年   483篇
  2016年   517篇
  2015年   573篇
  2014年   758篇
  2013年   1140篇
  2012年   1594篇
  2011年   1604篇
  2010年   865篇
  2009年   827篇
  2008年   1418篇
  2007年   1426篇
  2006年   1457篇
  2005年   1376篇
  2004年   1247篇
  2003年   1145篇
  2002年   1194篇
  2001年   453篇
  2000年   376篇
  1999年   437篇
  1998年   305篇
  1997年   260篇
  1996年   159篇
  1995年   179篇
  1994年   136篇
  1993年   118篇
  1992年   225篇
  1991年   198篇
  1990年   186篇
  1989年   169篇
  1988年   129篇
  1987年   140篇
  1986年   135篇
  1985年   140篇
  1984年   126篇
  1983年   146篇
  1982年   127篇
  1981年   96篇
  1980年   81篇
  1979年   106篇
  1978年   60篇
  1977年   63篇
  1974年   70篇
  1973年   68篇
  1971年   56篇
排序方式: 共有10000条查询结果,搜索用时 24 毫秒
1.
2.
3.
In osteoimmunology, osteoclastogenesis is understood in the context of the immune system. Today, the in vitro model for osteoclastogenesis necessitates the addition of recombinant human receptor activator of nuclear factor kappa‐B ligand (RANKL) and macrophage colony‐stimulating factor (M‐CSF). The peripheral joints of patients with rheumatoid arthritis (RA) and spondyloarthritis (SpA) are characterized by an immune‐mediated inflammation that can lead to bone destruction. Here, we evaluate spontaneous in vitro osteoclastogenesis in cultures of synovial fluid mononuclear cells (SFMCs) activated only in vivo. SFMCs were isolated and cultured for 21 days at 0.5–1.0 × 106 cells/mL in culture medium. SFMCs and healthy control peripheral blood monocytes were cultured with RANKL and M‐CSF as controls. Tartrate‐resistant acid phosphatase (TRAP) positive multinucleated cells were found in the SFMC cultures after 21 days. These cells expressed the osteoclast genes calcitonin receptor, cathepsin K, and integrin β3, formed lacunae on dentin plates and secreted matrix metalloproteinase 9 (MMP9) and TRAP. Adding RANKL and M‐CSF potentiated this secretion. In conclusion, we show that SFMCs from inflamed peripheral joints can spontaneously develop into functionally active osteoclasts ex vivo. Our study provides a simple in vitro model for studying inflammatory osteoclastogenesis.  相似文献   
4.
5.

Background

The optimal noninvasive test (NIT) for patients with diabetes and stable symptoms of coronary artery disease (CAD) is unknown.

Objectives

The purpose of this study was to assess whether a diagnostic strategy based on coronary computed tomographic angiography (CTA) is superior to functional stress testing in reducing adverse cardiovascular (CV) outcomes (CV death or myocardial infarction [MI]) among symptomatic patients with diabetes.

Methods

PROMISE (Prospective Multicenter Imaging Study for Evaluation of Chest Pain) was a randomized trial evaluating an initial strategy of CTA versus functional testing in stable outpatients with symptoms suggestive of CAD. The study compared CV outcomes in patients with diabetes (n = 1,908 [21%]) and without diabetes (n = 7,058 [79%]) based on their randomization to CTA or functional testing.

Results

Patients with diabetes (vs. without) were similar in age (median 61 years vs. 60 years) and sex (female 54% vs. 52%) but had a greater burden of CV comorbidities. Patients with diabetes who underwent CTA had a lower risk of CV death/MI compared with functional stress testing (CTA: 1.1% [10 of 936] vs. stress testing: 2.6% [25 of 972]; adjusted hazard ratio: 0.38; 95% confidence interval: 0.18 to 0.79; p = 0.01). There was no significant difference in nondiabetic patients (CTA: 1.4% [50 of 3,564] vs. stress testing: 1.3% [45 of 3,494]; adjusted hazard ratio: 1.03; 95% confidence interval: 0.69 to 1.54; p = 0.887; interaction term for diabetes p value = 0.02).

Conclusions

In diabetic patients presenting with stable chest pain, a CTA strategy resulted in fewer adverse CV outcomes than a functional testing strategy. CTA may be considered as the initial diagnostic strategy in this subgroup. (PROspective Multicenter Imaging Study for Evaluation of Chest Pain [PROMISE]; NCT01174550)  相似文献   
6.
Unilateral lesions of visual cortex have the secondary consequence of suppressing visual circuits in the midbrain superior colliculus (SC), collectively producing blindness in contralesional space (“hemianopia”). Recent studies have demonstrated that SC visual responses and contralesional vision can be reinstated by a non‐invasive multisensory training procedure in which spatiotemporally concordant visual‐auditory pairs are repeatedly presented within the blind hemifield. Despite this recovery of visual responsiveness, the loss of visual cortex was expected to result in permanent deficits in that hemifield, especially when visual events in both hemifields compete for attention and access to the brain's visuomotor circuitry. This was evaluated in the present study in a visual choice paradigm in which the two visual hemifields of recovered cats were simultaneously stimulated with equally valent visual targets. Surprisingly, the expected disparity was not found, and some animals even preferred stimuli presented in the previously blind hemifield. This preference persisted across multiple stimulus intensity levels and there was no indication that animals were less aware of cues in the previously blind hemifield than in its spared counterpart. Furthermore, when auditory cues were combined with visual cues, the enhanced performance they produced on a visual task was no greater in the normal than in the previously blind hemifield. These observations suggest that the multisensory rehabilitation paradigm revealed greater inherent visual information processing potential in the previously blind hemifield than was believed possible given the loss of visual cortex.  相似文献   
7.

Introduction The focus in clinical pharmacy practice is and has for the last 30–35 years been on changing the role of pharmacy staff into service orientation and patient counselling. One way of doing this is by involving staff in change process and as a researcher to take part in the change process by establishing partnerships with staff. On the background of the authors’ widespread action research (AR)-based experiences, recommendations and comments for how to conduct an AR-study is described, and one of their AR-based studies illustrate the methodology and the research methods used. Methodology AR is defined as an approach to research which is based on a problem-solving relationship between researchers and clients, which aims at both solving a problem and at collaboratively generating new knowledge. Research questions relevant in AR-studies are: what was the working process in this change oriented study? What learning and/or changes took place? What challenges/pitfalls had to be overcome? What were the influence/consequences for the involved parts? When to use If you want to implement new services and want to involve staff and others in the process, an AR methodology is very suitable. The basic advantages of doing AR-based studies are grounded in their participatory and democratic basis and their starting point in problems experienced in practice. Limitations Some of the limitations in AR-studies are that neither of the participants in a project steering group are the only ones to decide. Furthermore, the collective process makes the decision-making procedures relatively complex.

  相似文献   
8.
BackgroundChildren with adrenal suppression (AS), a potential side effect of glucocorticoids (GCs) may be asymptomatic, present with nonspecific signs and symptoms or with adrenal crisis. Asymptomatic AS (AAS) can only be diagnosed through screening. Identifying and treating asymptomatic patients before symptoms develop may reduce morbidity. Screening guidelines for AS are lacking. Consequently, screening practices are highly variable.ObjectiveTo assess (1) the screening practices for and recognition of paediatric AAS among clinicians in Canada and (2) the educational impact of a 2-year surveillance program of symptomatic AS cases.MethodsBefore and after a 2-year Canadian Paediatric Surveillance Program (CPSP) study of symptomatic AS, participants were surveyed through the CPSP. The prestudy survey was sent to 2,548 participants in March 2010 and the poststudy survey was sent to 2,465 participants in April 2013.ResultsResponse rates were 32% for the prestudy survey and 21% for the poststudy survey. Between the pre- and poststudy surveys, the percentage of physicians who reported routinely screening patients on GCs for AS increased from 10% to 21% and the percentage who reported having a screening policy in their office/centre increased from 6% to 11%. There was no significant change in the percentage of physicians who had diagnosed a child/youth with AAS in the preceding year.ConclusionFrequency of screening for AAS increased following the 2-year study but remains low. Development of a clinical practice guideline should increase both awareness of asymptomatic AS among Canadian paediatricians and the identification of AAS, before symptoms develop.  相似文献   
9.
Despite significant improvements in the prognosis of acute promyelocytic leukemia brought about by therapeutic advances, understanding of the epidemiology of acute promyelocytic leukemia remains limited. Earlier reports have suggested that Hispanics may have an increased incidence of acute promyelocytic leukemia, but no systematic analysis of national data has yet been reported. We performed a retrospective cohort study, using data from the Surveillance, Epidemiology, and End Results (SEER) Program of the National Cancer Institute from 1992-2001 in order to compare leukemia incidence rates as a function of race and ethnicity. We identified 709 cases of acute promyelocytic leukemia and analyzed incidence rates by race and sex. Hispanics were not found to have greater lifetime incidence rates than whites, with an incidence relative rate (IRR) of 0.86 that of whites (P=0.17). The age distribution among Hispanics was significantly different from non-Hispanic whites, with greater incidence rates for children ages 1-19 years (IRR=1.9, P=0.02) and adult ages 20-44 years (IRR=1.6, P=0.004). Blacks had lower lifetime incidence rates than non-Hispanic whites (IRR=0.75, P=0.04), Hispanics (IRR=0.64, P=0.007), and Asians (IRR=0.67, P=0.03). Asians did not differ from non-Hispanic whites in lifetime or age-specific incidence rates. These results indicate that while US Hispanics do not have greater lifetime incidence rates of acute promyelocytic leukemia, blacks have lower incidence rates of acute promyelocytic leukemia than Hispanics, non-Hispanic whites, and Asians.  相似文献   
10.
Oxygen-sensitive F-19 magnetic resonance imaging of perfluorocarbon compounds requires that fluorocarbon T1 changes correlate with the local Po2 and not with the composition of the surrounding aqueous phase. The influence of various bioconstituents and paramagnetic ions within the aqueous phase on the F-19 fluorocarbon phase T1 for PFC emulsions was evaluated at 0.14 and 0.66 T. T1 was measured for FC-43, perflubron, and a fluorinated surfactant. Controlled variables introduced in the aqueous phase included annex solution constituents, blood, pH changes, and Gd-DTPA. For a constant Po2, the F-19 T1s were independent of the emulsion constituents, blood concentration, and pH. For FC-43 and perflubron, F-19 T1 was independent of the Gd-DTPA concentration, while the aqueous phase T1 decreased by more than an order of magnitude. XMO-10 (smallest emulsion particle size) showed a slight decrease in F-19 T1 with increasing Gd-DTPA concentration at 0.66 T.  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