全文获取类型
收费全文 | 3263篇 |
免费 | 334篇 |
国内免费 | 11篇 |
专业分类
耳鼻咽喉 | 14篇 |
儿科学 | 69篇 |
妇产科学 | 77篇 |
基础医学 | 399篇 |
口腔科学 | 56篇 |
临床医学 | 367篇 |
内科学 | 778篇 |
皮肤病学 | 182篇 |
神经病学 | 316篇 |
特种医学 | 88篇 |
外科学 | 423篇 |
综合类 | 45篇 |
一般理论 | 5篇 |
预防医学 | 265篇 |
眼科学 | 55篇 |
药学 | 324篇 |
肿瘤学 | 145篇 |
出版年
2023年 | 57篇 |
2022年 | 43篇 |
2021年 | 118篇 |
2020年 | 103篇 |
2019年 | 97篇 |
2018年 | 108篇 |
2017年 | 78篇 |
2016年 | 76篇 |
2015年 | 68篇 |
2014年 | 114篇 |
2013年 | 162篇 |
2012年 | 180篇 |
2011年 | 211篇 |
2010年 | 106篇 |
2009年 | 111篇 |
2008年 | 184篇 |
2007年 | 177篇 |
2006年 | 168篇 |
2005年 | 159篇 |
2004年 | 124篇 |
2003年 | 114篇 |
2002年 | 109篇 |
2001年 | 68篇 |
2000年 | 60篇 |
1999年 | 60篇 |
1998年 | 40篇 |
1997年 | 17篇 |
1996年 | 19篇 |
1995年 | 16篇 |
1994年 | 16篇 |
1993年 | 21篇 |
1992年 | 47篇 |
1991年 | 39篇 |
1990年 | 31篇 |
1989年 | 24篇 |
1988年 | 36篇 |
1987年 | 39篇 |
1986年 | 37篇 |
1985年 | 25篇 |
1984年 | 22篇 |
1983年 | 14篇 |
1982年 | 25篇 |
1981年 | 17篇 |
1979年 | 29篇 |
1978年 | 14篇 |
1977年 | 17篇 |
1975年 | 18篇 |
1974年 | 18篇 |
1973年 | 14篇 |
1970年 | 14篇 |
排序方式: 共有3608条查询结果,搜索用时 15 毫秒
1.
Many studies identify the risk factors for joining street gangs, but few explore disengagement. This article provides a systematic review of the factors which contribute to disengagement from gangs. Understanding this area is of paramount importance to developing policy and guiding practitioners working with this population, given the impact this lifestyle has on gang members and society as a whole. Seven academic databases, reference lists of relevant publications, an online search engine and a government database were used to identify relevant studies. Inclusion and exclusion criteria and quality assessment methods were employed. Data were then extracted and synthesised. Of 2515 citations, seven were found to have methodological rigour. The findings suggest there is not one definitive reason for gang exit but rather that multiple factors contribute. Variability was found in the quality scores. The limitations of this review are discussed, along with clinical implications and suggestions for future research. 相似文献
2.
Carlos A. ávila-Orta Zoe V. Qui?ones-Jurado Miguel A. Waldo-Mendoza Erika A. Rivera-Paz Víctor J. Cruz-Delgado José M. Mata-Padilla Pablo González-Morones Ronald F. Ziolo 《Materials》2015,8(11):7900-7912
Isotactic polypropylenes (iPP) with different melt flow indexes (MFI) were used to fabricate nanocomposites (NCs) with 10 wt % loadings of multi-wall carbon nanotubes (MWCNTs) using ultrasound-assisted extrusion methods to determine their effect on the morphology, melt flow, and electrical properties of the NCs. Three different types of iPPs were used with MFIs of 2.5, 34 and 1200 g/10 min. Four different NC fabrication methods based on melt extrusion were used. In the first method melt extrusion fabrication without ultrasound assistance was used. In the second and third methods, an ultrasound probe attached to a hot chamber located at the exit of the die was used to subject the sample to fixed frequency and variable frequency, respectively. The fourth method is similar to the first method, with the difference being that the carbon nanotubes were treated in a fluidized air-bed with an ultrasound probe before being used in the fabrication of the NCs with no ultrasound assistance during extrusion. The samples were characterized by MFI, Optical microscopy (OM), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), electrical surface resistivity, and electric charge. MFI decreases in all cases with addition of MWCNTs with the largest decrease observed for samples with the highest MFI. The surface resistivity, which ranged from 1013 to 105 Ω/sq, and electric charge, were observed to depend on the ultrasound-assisted fabrication method as well as on the melt flow index of the iPP. A relationship between agglomerate size and area ratio with electric charge was found. Several trends in the overall data were identified and are discussed in terms of MFI and the different fabrication methods. 相似文献
3.
Quality of object relations versus interpersonal functioning as predictors of therapeutic alliance and psychotherapy outcome 总被引:1,自引:0,他引:1
W E Piper H F Azim A S Joyce M McCallum G W Nixon P S Segal 《The Journal of nervous and mental disease》1991,179(7):432-438
The purpose of the study was to compare an interview measure of quality of object relations to questionnaire and interview measures of recent interpersonal functioning with respect to the prediction of therapeutic alliance and psychotherapy outcome. The sample consisted of 64 patients who had received approximately 20 sessions of short-term individual psychotherapy within a controlled, clinical-trial investigation. Ratings of therapeutic alliance were provided independently by the patient and the therapist after each session. Outcome measures, which were provided by three sources (patient, therapist, and independent assessor), covered the areas of interpersonal functioning, psychiatric symptomatology, self-esteem, and life satisfaction. Quality of object relations, which characterizes the patient's lifelong pattern of relationships, was the best predictor. It was significantly related to patient-rated and therapist-rated therapeutic alliance and to patient improvement of both general symptomatology and specific target problems. The study also replicated previous studies that have reported significant relationships between therapeutic alliance and therapy outcome. The advantages of pretherapy predictors of therapy outcome, such as quality of object relations, are discussed. 相似文献
4.
5.
6.
Nonsteroidal anti-inflammatory drug use and increased risk for peptic ulcer disease in elderly persons 总被引:25,自引:0,他引:25
M R Griffin J M Piper J R Daugherty M Snowden W A Ray 《Annals of internal medicine》1991,114(4):257-263
OBJECTIVE: To evaluate the relative risk for peptic ulcer disease that is associated with the use of nonaspirin nonsteroidal anti-inflammatory drugs. DESIGN: Nested case-control study. SETTING: Tennessee Medicaid program. PARTICIPANTS: Medicaid enrollees 65 years of age or older were included in the study. The 1415 case patients had been hospitalized for confirmed peptic ulcer disease at some point from 1984 through 1986. The 7063 control persons represented a stratified random sample of other Medicaid enrollees. MEASUREMENTS AND MAIN RESULTS: The estimated relative risk for the development of peptic ulcer disease among current users of nonaspirin nonsteroidal anti-inflammatory drugs, compared with that among nonusers, was 4.1 (95% CI, 3.5 to 4.7). For current users, the risk increased with increasing dose, from a relative risk of 2.8 (CI, 1.8 to 4.3) for the lowest to a relative risk of 8.0 (CI, 4.4 to 14.8) for the highest dose category. The risk was greatest in the first month of use (relative risk, 7.2; CI, 4.9 to 10.5). If the association is fully causal, 29% of peptic ulcers in the study sample resulted from the use of these drugs, and the excess risk associated with such use was 17.4 hospitalizations for ulcer disease per 1000 person-years of exposure. CONCLUSIONS: These data support other findings indicating that a clinically significant risk for serious ulcer disease is associated with the use of nonaspirin nonsteroidal anti-inflammatory drugs. The data show that this risk increases with dose and recency of use and that use of these drugs may be responsible for a large proportion of peptic ulcer disease among elderly persons. 相似文献
7.
Yu X Kong Gavin Wright Konrad Pesudovs Justin ODay Zoe Wainer Harrison S Weisinger 《Clinical & experimental optometry》2007,90(5):336-344
Horner syndrome is an uncommon but important clinical entity, representing interruption of the sympathetic pathway to the eye and face. Horner syndrome is almost always diagnosed clinically, though pharmacological testing can be used to confirm the diagnosis. Imaging modalities such as PET, CT and MRI are important components of work‐up for patients presenting with acquired Horner syndrome. Our patient’s presentation with Horner syndrome unmasked the causative superior sulcus squamous cell carcinoma and a coincidental lower lobe adenocarcinoma. Successful radical treatment of these cancers resulted in complete resolution of the syndrome and disease‐free survival at 18 months. We review the anatomy and pathophysiology underlying this and other causes of Horner syndrome. 相似文献
8.
The perception of moving objects and our successful interaction with them entail that the visual system integrates shape and motion information about objects. However, neuroimaging studies have implicated different human brain regions in the analysis of visual motion (medial temporal cortex; MT/MST) and shape (lateral occipital complex; LOC), consistent with traditional approaches in visual processing that attribute shape and motion processing to anatomically and functionally separable neural mechanisms. Here we demonstrate object-selective fMRI responses (higher responses for intact than for scrambled images of objects) in MT/MST, and especially in a ventral subregion of MT/MST, suggesting that human brain regions involved mainly in the processing of visual motion are also engaged in the analysis of object shape. 相似文献
9.
Reduction by prostaglandin E1 or prostaglandin E0 of myocardial infarct size in the rabbit by activation of ATP-sensitive potassium channels. 总被引:10,自引:2,他引:8
下载免费PDF全文
![点击此处可从《British journal of pharmacology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
E. J. Hide P. Ney J. Piper C. Thiemermann J. R. Vane 《British journal of pharmacology》1995,116(5):2435-2440
1. This study examined whether pretreatment of rabbits with infusions of prostaglandin E1 (PGE1) or prostaglandin E0 (PGE0) (which were terminated prior to the onset of ischaemia) reduce myocardial infarct size arising from coronary artery occlusion (60 min) and reperfusion (120 min). In addition, we investigated whether the observed cardioprotective effects of these two prostaglandins were due to the activation of ATP-sensitive potassium (KATP) channels. 2. In the anaesthetized rabbit, infarct size (expressed as a percentage of the area at risk) after 60 min of coronary artery occlusion followed by 2 h of reperfusion was 59 +/- 4% (n = 10). PGE1 or PGE0 treatment (1.0 micrograms kg-1 min-1), administered as 1 h pretreatments (0.05 ml min-1, i.v.), significantly reduced infarct size to 44 +/- 6% (n = 6) or 42 +/- 1% (n = 6), respectively. PGE1 or PGE0 pretreatment resulted in a significant reduction in mean arterial blood pressure, which returned to baseline within 15 min of discontinuation of the infusion (i.e. prior to LAL ligation). 3. The reduction in infarct size afforded by PGE1 was abolished by pretreatment of rabbits with the KATP channel blockers, glibenclamide (60 +/- 4%; n = 8) or 5-hydroxydecanoate (58 +/- 6%; n = 6). Similarly, glibenclamide also largely attenuated the reduction in infarct size afforded by PGE0 (52 +/- 3%; n = 8). 4. We propose that a 1 h pretreatment of PGE1 or PGE0 reduces infarct size by activating protein kinase C resulting in the opening of KATP channels. 相似文献
10.