全文获取类型
收费全文 | 925篇 |
免费 | 69篇 |
国内免费 | 4篇 |
专业分类
耳鼻咽喉 | 4篇 |
儿科学 | 32篇 |
妇产科学 | 23篇 |
基础医学 | 95篇 |
口腔科学 | 8篇 |
临床医学 | 147篇 |
内科学 | 128篇 |
皮肤病学 | 16篇 |
神经病学 | 69篇 |
特种医学 | 140篇 |
外科学 | 72篇 |
综合类 | 7篇 |
一般理论 | 1篇 |
预防医学 | 123篇 |
眼科学 | 8篇 |
药学 | 70篇 |
2篇 | |
肿瘤学 | 53篇 |
出版年
2023年 | 6篇 |
2022年 | 5篇 |
2021年 | 6篇 |
2020年 | 12篇 |
2019年 | 12篇 |
2018年 | 20篇 |
2017年 | 14篇 |
2016年 | 18篇 |
2015年 | 19篇 |
2014年 | 28篇 |
2013年 | 37篇 |
2012年 | 49篇 |
2011年 | 47篇 |
2010年 | 38篇 |
2009年 | 53篇 |
2008年 | 36篇 |
2007年 | 41篇 |
2006年 | 37篇 |
2005年 | 32篇 |
2004年 | 33篇 |
2003年 | 23篇 |
2002年 | 31篇 |
2001年 | 19篇 |
2000年 | 24篇 |
1999年 | 21篇 |
1998年 | 25篇 |
1997年 | 29篇 |
1996年 | 26篇 |
1995年 | 21篇 |
1994年 | 19篇 |
1993年 | 13篇 |
1992年 | 8篇 |
1991年 | 13篇 |
1990年 | 15篇 |
1989年 | 19篇 |
1988年 | 9篇 |
1987年 | 14篇 |
1986年 | 16篇 |
1985年 | 13篇 |
1984年 | 5篇 |
1983年 | 13篇 |
1982年 | 6篇 |
1980年 | 6篇 |
1979年 | 11篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1976年 | 7篇 |
1975年 | 7篇 |
1973年 | 6篇 |
1972年 | 8篇 |
排序方式: 共有998条查询结果,搜索用时 15 毫秒
1.
Turboprop: improved PROPELLER imaging. 总被引:1,自引:0,他引:1
A variant of periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) MRI, called turboprop, is introduced. This method employs an oscillating readout gradient during each spin echo of the echo train to collect more lines of data per echo train, which reduces the minimum scan time, motion-related artifact, and specific absorption rate (SAR) while increasing sampling efficiency. It can be applied to conventional fast spin-echo (FSE) imaging; however, this article emphasizes its application in diffusion-weighted imaging (DWI). The method is described and compared with conventional PROPELLER imaging, and clinical images collected with this PROPELLER variant are shown. 相似文献
2.
Repeated survey on changes in musculoskeletal complaints relative to age and work demands. 总被引:3,自引:3,他引:0
下载免费PDF全文
![点击此处可从《Occupational and environmental medicine》网站下载免费的PDF全文](/ch/ext_images/free.gif)
B C de Zwart J P Broersen M H Frings-Dresen F J van Dijk 《Occupational and environmental medicine》1997,54(11):793-799
OBJECTIVES: To examine changes in musculoskeletal complaints over four years in groups of employees relative to age and work demands. METHODS: Repeated questionnaire data of male employees in heavy physical work (exposed group, n = 7324) and mental work (control group, n = 4686), stratified for age (20-9, 30-9, 40-9, 50-9), were analysed. For each employee, data on the occurrence of musculoskeletal complaints from two surveys with a mean interval of around four years were available. Changes in prevalences over the follow up interval were analysed. Proportions of new, recovered, and chronic cases as well as those free of complaints at both surveys were studied. RESULTS: For most complaints, there were significantly greater increases in prevalences in the exposed group compared with the control group over the follow up interval particularly within the group aged 40-9 for back, neck, and several sites of the upper and lower limbs. The 20-9 year age group also had significantly greater changes for several musculoskeletal complaints. Within the oldest age group (50-9) exposure to heavy physical work demands only affected changes in prevalences of neck and upper arm complaints. After four years in the cohort free of complaints at the start of the follow up the group aged 40-9 had the highest prevalence of complaints of the back, neck, and the upper and lower limbs. CONCLUSIONS: Middle aged and younger employees develop musculoskeletal complaints as a result of exposure to heavy physical work. In the oldest age group health related selection seems to mask the occupational health risks under study. To prevent the expected increase in musculoskeletal disorders and related work disability in our aging workforce, preventive measures should be taken at all stages of a working life. 相似文献
3.
4.
Clinical aspects of pelvic inflammatory disease 总被引:2,自引:0,他引:2
Pelvic inflammatory disease (PID) is a common and poorly managed condition.
Untreated or inadequately treated, it leads to tubal infertility, ectopic
pregnancy and chronic pelvic pain. Diagnostic difficulties are compounded
by the wide variety of clinical presentations and the insensitivity and
poor specificity of laboratory tests. Better recognition of mild and
atypical disease needs a high index of suspicion whenever young, sexually
active women present with gynaecological symptoms. Laparoscopy supplemented
by microbiological tests and fimbrial minibiopsy should be regarded as the
diagnostic 'gold standard' for research studies; new studies are required
to identify techniques which might reduce under- and over-diagnosis. Early
treatment reduces the risk of an adverse effect on fertility. Any
therapeutic regimen selected should be effective against the common
aetiological agents Chlamydia trachomatis, Neisseria gonorrhoeae, genital
mycoplasmas and aerobic and anaerobic bacteria. Since at least 60% of cases
of PID can be attributed to infection with a sexually transmitted organism,
partner notification forms an essential part of management.
相似文献
5.
L. J. Stovner J.-A. Zwart K. Hagen G. M. Terwindt J. Pascual 《European journal of neurology》2006,13(4):333-345
The present review of epidemiologic studies on migraine and headache in Europe is part of a larger initiative by the European Brain Council to estimate the costs incurred because of brain disorders. Summarizing the data on 1-year prevalence, the proportion of adults in Europe reporting headache was 51%, migraine 14%, and 'chronic headache' (i.e. > or =15 days/month or 'daily') 4%. Generally, migraine, and to a lesser degree headache, are most prevalent during the most productive years of adulthood, from age 20 to 50 years. Several European studies document the negative influence of headache disorders on the quality of life, and health-economic studies indicate that 15% of adults were absent from work during the last year because of headache. Very few studies have been performed in Eastern Europe, and there are also surprisingly little data on tension-type headache from any country. Although the methodology and the quality of the published studies vary considerably, making direct comparisons between different countries difficult, the present review clearly demonstrates that headache disorders are extremely prevalent and have a vast impact on public health. The data collected should be used as arguments to increase resources to headache research and care for headache patients all over the continent. 相似文献
6.
Interactive effects of ozone and formaldehyde on the nasal respiratory lining epithelium in rats 总被引:1,自引:0,他引:1
P G Reuzel J W Wilmer R A Woutersen A Zwart P J Rombout V J Feron 《Journal of toxicology and environmental health》1990,29(3):279-292
The combined effects on the nasal epithelium of mixtures of ozone and formaldehyde at cytotoxic and noncytotoxic concentrations were examined. Male Wistar rats were exposed by inhalation during 22 h/d for 3 consecutive days to 0.3, 1.0, or 3.0 ppm formaldehyde, or to 0.2, 0.4, or 0.8 ppm ozone, or to mixtures of 0.4 ppm ozone and 0.3, 1.0, or 3.0 ppm formaldehyde, or to 1.0 ppm formaldehyde and 0.2, 0.4, or 0.8 ppm ozone, or they were sham-exposed to clean air. The noses were examined for pathological changes at six standard cross levels by light microscopy and for epithelial cell proliferation by counting [3H-methyl]thymidine-labeled cells at cross levels II and III. Ozone at 0.4 ppm or 0.8 ppm or formaldehyde at 3 ppm enhanced cell proliferation at cross level II at all locations, except for the epithelium of the septum, which was not affected by ozone. At cross level III ozone alone did not induce cell proliferation, but formaldehyde at 0.3 and 1 ppm tended to reduce cell proliferation while at 3 ppm proliferation was slightly stimulated. The combined exposure to 0.4 ppm ozone and 0.3 ppm formaldehyde induced less cell proliferation at cross levels II and III when compared with that of 0.4 ppm ozone alone. Less cell proliferation was also seen at cross level II when animals were exposed to 0.4 or 0.8 ppm ozone in combination with 1 ppm formaldehyde than when exposed to these ozone concentrations alone. A more than additive increase in cell proliferation was found at cross level II after exposure to 0.4 ppm ozone in combination with 3 ppm formaldehyde, and at cross level III in animals exposed to 0.4 ppm ozone and 1 or 3 ppm formaldehyde. Treatment-related histopathological nasal changes, such as disarrangement, loss of cilia, and hyper/metaplasia of the epithelium were seen at 0.2, 0.4, and 0.8 ppm ozone and at 3 ppm formaldehyde. Simultaneous exposure to both materials did not noticeably affect type, degree, and size of the microscopic nasal lesions. 相似文献
7.
Depression and anxiety disorders associated with headache frequency. The Nord‐Trøndelag Health Study
J.‐A. Zwart G. Dyb K. Hagen K. J.
degrd A. A. Dahl G. Bovim L. J. Stovner 《European journal of neurology》2003,10(2):147-152
The aim of this large cross‐sectional population‐based study was to examine the association between migraine, non‐migrainous headache and headache frequency with depression, and anxiety disorders. From 1995 to 1997, all 92 566 inhabitants aged 20 years and above in Nord‐Trøndelag County in Norway were invited to participate in the Nord‐Trøndelag Health Study (‘Helseundersøkelsen i Nord‐Trøndelag’ = HUNT‐2). A total of 64 560 participated, whereof 51 383 subjects (80%) completed a headache questionnaire that was included. Of these 51 383 individuals, 47 257 (92%) completed the depression subscale items and 43 478 (85%), the anxiety subscale items of the Hospital Anxiety and Depression Scale (HADS). Associations were assessed in multivariate analyses, estimating prevalence odds ratios (OR) with 95% confidence intervals (CI). Depression and anxiety disorders as measured by HADS, were significantly associated with migraine (OR = 2.7, 95% CI 2.3–3.2; OR = 3.2, 95% CI 2.8–3.6) and non‐migrainous headache (OR = 2.2, 95% CI 2.0–2.5; OR = 2.7, 95% CI 2.4–3.0) when compared with headache‐free individuals. The association was stronger for anxiety disorders than for depression. The ORs for depression and anxiety disorders amongst both migraine and non‐migrainous sufferers increased with increasing headache frequency. Depression and anxiety disorders are associated with both migraine and non‐migrainous headache, and this association seems more dependent on headache frequency than diagnostic category. 相似文献
8.
Screening for early ovarian cancer 总被引:5,自引:0,他引:5
9.
GORDON M. Wise frco fracs frcs JONATHAN E. Osborn bsurv mis PETER R. Zwart bsc msce fis 《Clinical & experimental ophthalmology》1987,15(4):269-275
The limitations of keratometry and photokeratoscopy are briefly discussed. A new photogrammetric technique of measuring corneal topography is described. Contours and cross-sections of abnormal corneas are presented to illustrate the scope and application of the new technique. 相似文献
10.
Incidence and determinants of moderate COPD (GOLD II) in male smokers aged 40–65 years: 5-year follow up
下载免费PDF全文
![点击此处可从《The British journal of general practice》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Roeland MM Geijer Alfred PE Sachs Theo JM Verheij Philippe L Salom Jan-Willem J Lammers Arno W Hoes 《The British journal of general practice》2006,56(530):656-661
BACKGROUND: Chronic obstructive pulmonary disease (COPD) is a major health problem with an estimated prevalence of 10-15% among smokers. The incidence of moderate COPD, as defined by the Global Initiative for Chronic Obstructive Lung Disease (GOLD), is largely unknown. AIM: To determine the cumulative incidence of moderate COPD (forced expiratory volume in 1 second/forced vital capacity ratio [FEV1/FVC] <0.7 and FEV1 <80% predicted) and its association with patient characteristics in a cohort of male smokers. DESIGN: Prospective cohort study. SETTING: The city of IJsselstein, a small town in the Netherlands. METHOD: Smokers aged 40-65 years who were registered with local GPs, participated in a study to identify undetected COPD. Baseline measurements were taken in 1998 of 399 smokers with normal spirometry (n = 292) or mild COPD (FEV1/FVC <0.7 and FEV1 >or=80% predicted, n = 107) and follow-up measurements were conducted in 2003. RESULTS: After a mean follow-up of 5.2 years, 33 participants developed moderate COPD (GOLD II). This showed an estimated cumulative incidence of 8.3% (95% CI = 5.8 to 11.4) and a mean annual incidence of 1.6%. No participant developed severe airflow obstruction. The risk of developing moderate COPD in smokers with baseline mild COPD (GOLD I) was five times higher than in those with baseline normal spirometry (one in five versus one in 25). CONCLUSIONS: In a cohort of middle-aged male smokers, the estimated cumulative incidence of moderate COPD (GOLD II) over 5 years was relatively high (8.3%). Age, childhood smoking, cough, and one or more GP contacts for lower respiratory tract problems were independently associated with incident moderate COPD. 相似文献