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   82906篇
  免费   8183篇
  国内免费   157篇
耳鼻咽喉   1181篇
儿科学   2492篇
妇产科学   1789篇
基础医学   11848篇
口腔科学   2021篇
临床医学   10174篇
内科学   14621篇
皮肤病学   1301篇
神经病学   6732篇
特种医学   2819篇
外国民族医学   10篇
外科学   11418篇
综合类   1663篇
一般理论   67篇
预防医学   9482篇
眼科学   1852篇
药学   6748篇
  1篇
中国医学   77篇
肿瘤学   4950篇
  2021年   1111篇
  2020年   739篇
  2019年   1120篇
  2018年   1397篇
  2017年   1003篇
  2016年   1094篇
  2015年   1244篇
  2014年   1635篇
  2013年   2570篇
  2012年   3467篇
  2011年   3745篇
  2010年   1995篇
  2009年   1915篇
  2008年   3226篇
  2007年   3544篇
  2006年   3416篇
  2005年   3481篇
  2004年   3248篇
  2003年   3020篇
  2002年   2954篇
  2001年   2716篇
  2000年   2827篇
  1999年   2509篇
  1998年   1081篇
  1997年   888篇
  1996年   876篇
  1995年   787篇
  1994年   812篇
  1993年   743篇
  1992年   2094篇
  1991年   2019篇
  1990年   1894篇
  1989年   1868篇
  1988年   1770篇
  1987年   1777篇
  1986年   1685篇
  1985年   1665篇
  1984年   1387篇
  1983年   1261篇
  1982年   842篇
  1981年   723篇
  1979年   1215篇
  1978年   875篇
  1977年   764篇
  1976年   718篇
  1975年   717篇
  1974年   859篇
  1973年   752篇
  1972年   733篇
  1971年   640篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
The high incidence of trauma among young men has been observed in many countries. To better understand this risk, we analyzed male injuries and their causes in Finland. The incidence peak of medically attended trauma in men aged 15-24 years was caused by occupational and sports injuries, whereas that of hospitalizations was due to motor vehicle injuries. Age patterns of nonfatal trauma resembled those recorded in the U.S.A. However, patterns and causes of fatal trauma were very different in the two countries: early adulthood in the U.S.A. and late middle-age in Finland were the ages of highest injury mortality. The majority of deaths in young men were caused by motor vehicle injuries in the U.S.A., whereas suicides and the extremely high rate of fatal non-motor vehicle accidents, largely due to alcohol poisoning and drownings, formed the main bulk of injury mortality in Finland. Similarities in early adulthood suggest general biological factors, whereas the deviance of the middle-aged male Finns from the general pattern may indicate more specific psychosocial factors.  相似文献   
82.
The portrayal of alcohol was examined in a systematic sampleof 50 programmes broadcast on British television. Four out offive programmes contained visual or verbal references to alcohol.On average, there was a reference to alcohol in every 6 minutesof programming. The programmes showed more alcohol being consumedthan soft drinks or beverages, but there were few referencesto the hazards of alcohol consumption. The main recommendationis that television companies should accept a responsibilityfor presenting a more realistic and healthier approach to theuse of alcohol in Britain  相似文献   
83.
Separate exposures to 0.12 ppm ozone (O3) or 0.18 ppm nitrogen dioxide (NO2) have not demonstrated consistent changes in pulmonary function in adolescent subjects. However, in polluted urban air, O3 and NO2 occur in combination. Therefore, this project was designed to investigate the pulmonary effects of combined O3 and NO2 exposures during intermittent exercise in adolescent subjects. Twelve healthy and twelve well-characterized asthmatic adolescent subjects were exposed randomly to clean air or 0.12 ppm O3 and 0.30 ppm NO2 alone or in combination during 60 minutes of intermittent moderate exercise (32.5 1/min). The inhalation exposures were carried out while the subjects breathed on a rubber mouthpiece with nose clips in place. The following pulmonary functional values were measured before and after exposure: peak flow, total respiratory resistance, maximal flow at 50 and 75 percent of expired vital capacity, forced expiratory volume in one second and forced vital capacity (FVC). Statistical significance of pulmonary function changes was tested by analysis of covariance for repeated measures. After exposure to 0.12 ppm O3 a significant decrease was seen in maximal flow at 50% of FVC in asthmatic subjects. After exposure to 0.30 ppm NO2 a significant decrease was seen in FVC also in the asthmatic subjects. One possible explanation for these changes is the multiple comparison effect. No significant changes in any parameters were seen in the asthmatic subjects after the combined O3-NO2 exposure or in the healthy subjects after any of the exposures.  相似文献   
84.
We describe a patient with viral induced aplastic anemia who developed severe bone pain after treatment with multiple courses of antithymocyte globulin, cyclosporine A, recombinant human granulocyte macrophage colony stimulating factor and deferoxamine. Radiographs and bone biopsy revealed extensive new trabecular bone formation in long bone diaphyses and adjacent periosteal reaction. The effects of hematopoietic growth factors, cyclosporine A and deferoxamine on bone metabolism are reviewed.  相似文献   
85.
A distinctive systematized epithelial nevus and associated multifocal carcinomas of the microcystic and sclerosing sweat duct type affected the lower extremities of a 9-year-old girl. The carcinomas were well differentiated and were both adenosyringomatous and microcystic. They qualify as microcystic and compound. In both the epithelial nevi and the carcinoma, primordial potentials are recapitulated.  相似文献   
86.
Summary Fifty-five patients with metastatic non-small cell lung cancer (NSCLC) were entered into this phase II randomized study for evaluating three new agents: gallium nitrate, amonafide and teniposide. The patients had to have ECOG performance status 0 or 1, no prior chemotherapy, and adequate hematological, hepatic and renal functions. Forty-seven patients were eligible and evaluable. Fourteen were randomized to receive gallium nitrate, 18 to amonafide and 15 to teniposide. Seventy-four percent of eligible patients were male. The majority of patients (89%) had an ECOG performance status 1. ECOG grade 4 toxicity occurred twice in patients on gallium nitrate, seven times on amonafide and 18 times on teniposide. The cause of death was attributed to amonafide in one patient (from sepsis) and to teniposide in two patients (due to infection and leukopenia). There was no objective response in all the patients entered. The overall survival times ranged from 2 weeks to 156 weeks with a median of 23 weeks. There were no survival differences among the three treatment arms. We conclude that gallium nitrate, amonafide and teniposide are inactive in metastatic NSCLC and do not warrant any further testing in this disease.The contents of this study is solely the responsibility of the authors and does not necessarily represent the official views of the National Cancer Institute.  相似文献   
87.
Biofeedback     
M S Smith 《Pediatric annals》1991,20(3):128, 130-128, 134
  相似文献   
88.
Fast spin echo (FSE) imaging has recently experienced a renewed enthusiasm in the clinical setting for its ability to provide high contrast T2-weighted images in short imaging times. This article evaluates the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) properties of the FSE sequence, inversion recovery (IR) FSE sequence, and conventional SE imaging. The results indicate that FSE imaging displays similar contrast properties to SE imaging, but that the SNR and CNR are improved secondary to the longer TRs and longer effective TEs that may be used. The SNR per unit time of the FSE sequence, and hence its efficiency, is at least a factor of 8 better than the SE sequence when 16 echoes are acquired for each excitation. The addition of a slice selective inversion pulse in IR-FSE allows rapid generation of IR images with image contrast similar to that of conventional IR sequences. When used with a multicoil array for abdominal, pelvic, and spine imaging, the IR-FSE sequence produces images that are virtually free of motion artifact from the subcutaneous fat immediately adjacent to the coils. Both FSE and IR-FSE, when compared with SE imaging, provide superior image contrast and SNR in reduced imaging time.  相似文献   
89.
Objectives - To determine whether dexamethasone `matures' the phosphatidylcholine (PC) composition of broncheoalveolar fluid in infants at high risk of neonatal chronic lung disease (CLD), either by increasing the proportion of dipalmitoylphosphatidylcholine (DPPC), expressed as a percentage of total PC (%DPPC), or by increasing the ratio of DPPC to palmitoyloleoylphosphatidylcholine (DPPC:POPC ratio).  相似文献   
90.
A case-control study of larynx cancer was conducted within a cohort of automobile workers exposed to metal working fluids, commonly referred to as machining fluids (MF). Results are based on 108 cases of larynx cancer and 5:1 matched controls. Risks associated with specific types of MF, as well as specific components of the fluids were evaluated. Based on a retrospective exposure assessment, lifetime exposures to straight and soluble fluids, grinding particulate, biocides, selected metals, sulfur, and chlorine were examined. Exposure to asbestos and acid mists at two of the three study sites was also characterized. Results suggest that straight mineral oils are associated with almost a two-fold excess in larynx cancer risk. There was also evidence of an association with elemental sulfur, commonly added to straight MF to improve the integrity of the materials under extreme pressure and heat. It is not clear whether sulfur is causally related to an excess relative risk of larynx cancer or whether the observed association is the result of unmeasured confounding by another contaminant or process feature. For example, the high stress operations that require MF enriched with sulfur are also more likely to produce polycyclic aromatic hydrocarbons (PAHs) during the process. Thus, the observed association with sulfur may be due to an association with PAH. The finding of excess risk of laryngeal cancer associated with MF is consistent with several previous reports in the literature. This is the first study, however, to distinguish straight mineral oils from other types of MF. Based on these findings, a general reduction in concentrations of straight mineral oil particulate in occupational environments would be prudent.  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