全文获取类型
收费全文 | 82778篇 |
免费 | 8334篇 |
国内免费 | 157篇 |
专业分类
耳鼻咽喉 | 1182篇 |
儿科学 | 2498篇 |
妇产科学 | 1794篇 |
基础医学 | 11905篇 |
口腔科学 | 1998篇 |
临床医学 | 10167篇 |
内科学 | 14627篇 |
皮肤病学 | 1294篇 |
神经病学 | 6750篇 |
特种医学 | 2756篇 |
外国民族医学 | 10篇 |
外科学 | 11431篇 |
综合类 | 1662篇 |
一般理论 | 67篇 |
预防医学 | 9467篇 |
眼科学 | 1857篇 |
药学 | 6766篇 |
1篇 | |
中国医学 | 78篇 |
肿瘤学 | 4959篇 |
出版年
2021年 | 1143篇 |
2020年 | 748篇 |
2019年 | 1134篇 |
2018年 | 1407篇 |
2017年 | 1020篇 |
2016年 | 1106篇 |
2015年 | 1254篇 |
2014年 | 1655篇 |
2013年 | 2587篇 |
2012年 | 3502篇 |
2011年 | 3775篇 |
2010年 | 2000篇 |
2009年 | 1920篇 |
2008年 | 3250篇 |
2007年 | 3565篇 |
2006年 | 3439篇 |
2005年 | 3487篇 |
2004年 | 3262篇 |
2003年 | 3025篇 |
2002年 | 2960篇 |
2001年 | 2713篇 |
2000年 | 2824篇 |
1999年 | 2501篇 |
1998年 | 1064篇 |
1997年 | 871篇 |
1996年 | 860篇 |
1995年 | 775篇 |
1994年 | 802篇 |
1993年 | 735篇 |
1992年 | 2092篇 |
1991年 | 2018篇 |
1990年 | 1893篇 |
1989年 | 1855篇 |
1988年 | 1763篇 |
1987年 | 1773篇 |
1986年 | 1678篇 |
1985年 | 1660篇 |
1984年 | 1384篇 |
1983年 | 1254篇 |
1982年 | 836篇 |
1981年 | 713篇 |
1979年 | 1212篇 |
1978年 | 871篇 |
1977年 | 760篇 |
1976年 | 714篇 |
1975年 | 713篇 |
1974年 | 859篇 |
1973年 | 752篇 |
1972年 | 733篇 |
1971年 | 641篇 |
排序方式: 共有10000条查询结果,搜索用时 796 毫秒
191.
V Raptopoulos A Davidoff A Karellas M A Davis B L Coolbaugh E H Smith 《AJR. American journal of roentgenology》1988,150(6):1303-1306
Visualization of the head of the pancreas by CT was prospectively evaluated in two groups of 100 patients who did not have pancreatic disease. Patients were given either a fat-density oral contrast material (12.5% corn-oil emulsion and metoclopramide) or a conventional high-density oral contrast material (barium suspension or iodinated solution). There was no statistically significant difference in the subjects' tolerance to the two regimens. There was, however, a significant improvement in ability to distinguish the head of the pancreas from the duodenal C-loop when the fat-density contrast material was given. When pancreaticoduodenal discrimination was graded, patients given corn-oil emulsion and metoclopramide received an average score of 0.94, whereas those given the high-density agent received an average score of 0.74, with 1.00 being the highest possible score (p less than .005). These data suggest that for routine CT evaluation of the head of the pancreas, a combination of corn-oil emulsion and metoclopramide may be superior to the conventional high-density oral contrast agents given without metoclopramide. 相似文献
192.
Four renal tubular enzymes, N-acetyl-beta-glucosaminidase, beta-galactosidase, angiotensin-converting enzyme and gamma-glutamyltransferase, were measured in the urine before, and 24 hours and 1 week after extracorporeal shock wave lithotripsy in 20 consecutive patients. Extracorporeal shock wave lithotripsy was performed on the Sonolith 2000 device with the patient under intravenous narcotic sedation with fentanyl. Enzymatic activity per gram of urinary creatinine was consistently but not significantly higher before extracorporeal shock wave lithotripsy than in control subjects. All 4 enzymes were elevated 24 hours after extracorporeal shock wave lithotripsy, with the increases in beta-galactosidase and angiotensin-converting enzyme being statistically significant. However, by 7 days after the procedure the enzymes had decreased to pre-procedure concentrations or below. These data suggest that any renal tubular damage induced by extracorporeal shock wave lithotripsy is of limited magnitude and brief duration. 相似文献
193.
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
194.
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
195.
J Q Koenig D S Covert M S Smith G van Belle W E Pierson 《Toxicology and industrial health》1988,4(4):521-532
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
196.
197.
Esmolol for treatment of intraoperative tachycardia and/or hypertension in patients having cardiac operations. Bolus loading technique 总被引:1,自引:0,他引:1
J G Reves N D Croughwell E Hawkins L R Smith J R Jacobs S Rankin J Lowe P VanTrigt 《The Journal of thoracic and cardiovascular surgery》1990,100(2):221-227
Esmolol, administered as a bolus followed by continuous infusion, was used to treat the occurrence of transient tachycardia and hypertension or tachycardia alone before cardiopulmonary bypass in 45 patients. The study was conducted in two phases. Phase I (15 patients) was a dose-finding study and phase II (30 patients) was a randomized, double-blind, placebo-controlled efficacy study. All patients received the last dose of their usual beta-adrenergic blocker the night before the operation and were anesthetized with midazolam, vecuronium, and enflurane in oxygen. Treatment criteria were either a systolic blood pressure greater than 140 mm Hg and a heart rate greater than 70 or a heart rate greater than 80 beats/min. In phase I, graduated doses of esmolol were given to successive patients. A dose of 80 mg followed by a 12 mg/min infusion was declared effective. Phase II patients were randomized to receive esmolol (n = 16) or placebo (n = 14). Hemodynamic data were collected at baseline and 1, 3, 5, and 10 minutes after the administration of esmolol. Plasma norepinephrine was measured at baseline, 1, and 10 minutes. Esmolol significantly (p less than 0.05) reduced heart rate at 1, 3, 5, and 10 minutes but did not change blood pressure, pulmonary artery diastolic pressure, right atrial pressure, cardiac output, or systemic vascular resistance. Our results show that a bolus loading dose of esmolol is safe and effective in the treatment of tachycardia in patients with ischemic heart disease and that esmolol rapidly blocks the beta-adrenergic effects of norepinephrine associated with surgical stress. 相似文献
198.
Multiple genes encode nuclear factor 1-like proteins that bind to the promoter for 3-hydroxy-3-methylglutaryl-coenzyme A reductase. 总被引:37,自引:1,他引:36 下载免费PDF全文
199.
Interaction of HPV-18 and nitrosomethylurea in the induction of squamous cell carcinoma 总被引:4,自引:1,他引:3
Garrett Lenora R; Perez-Reyes Nuria; Smith Patricia P.; McDougall James K. 《Carcinogenesis》1993,14(2):329-333
A strong correlation exists between the presence of specifictypes of human papillomavirus (HPV) and the development of anogenitalcancer, as well as significant epidemiologic evidence suggestingsmokers are at increased risk of developing cervical, vulvarand/or anal carcinomas. Primary and human papillomavirus type18 (HPV-8)-immortalized human keratinocytes were used to addressthe co-carcinogenic potential of HPV and nitrosomethylurea (NMU)in tumorigenesis. Only cells containing HPV-18 and treated withNMU and the tumor-promoting phorbol ester, TPA, were transformedto a malignant phenotype. An in vitro system is described whichinitiates studies involving the mechanisms of HPV and chemicalcarcinogen co-operation in the etiology of squamous cell carcinomas. 相似文献
200.
B A Derfus M E Csuka G F Carrera G A Hanson R E Smith 《The Journal of rheumatology》1991,18(5):738-742
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