全文获取类型
收费全文 | 129870篇 |
免费 | 10443篇 |
国内免费 | 570篇 |
专业分类
耳鼻咽喉 | 1508篇 |
儿科学 | 3823篇 |
妇产科学 | 2276篇 |
基础医学 | 16560篇 |
口腔科学 | 2266篇 |
临床医学 | 13289篇 |
内科学 | 28042篇 |
皮肤病学 | 1899篇 |
神经病学 | 12553篇 |
特种医学 | 4019篇 |
外国民族医学 | 1篇 |
外科学 | 19775篇 |
综合类 | 1668篇 |
现状与发展 | 1篇 |
一般理论 | 156篇 |
预防医学 | 11350篇 |
眼科学 | 3804篇 |
药学 | 8797篇 |
1篇 | |
中国医学 | 278篇 |
肿瘤学 | 8817篇 |
出版年
2023年 | 1252篇 |
2022年 | 1153篇 |
2021年 | 2626篇 |
2020年 | 1776篇 |
2019年 | 2550篇 |
2018年 | 3427篇 |
2017年 | 2724篇 |
2016年 | 2982篇 |
2015年 | 3301篇 |
2014年 | 4705篇 |
2013年 | 6240篇 |
2012年 | 8791篇 |
2011年 | 9396篇 |
2010年 | 5453篇 |
2009年 | 5237篇 |
2008年 | 8295篇 |
2007年 | 8676篇 |
2006年 | 8279篇 |
2005年 | 8257篇 |
2004年 | 7777篇 |
2003年 | 7137篇 |
2002年 | 6886篇 |
2001年 | 1292篇 |
2000年 | 930篇 |
1999年 | 1295篇 |
1998年 | 1535篇 |
1997年 | 1312篇 |
1996年 | 1007篇 |
1995年 | 1004篇 |
1994年 | 838篇 |
1993年 | 818篇 |
1992年 | 704篇 |
1991年 | 639篇 |
1990年 | 557篇 |
1989年 | 518篇 |
1988年 | 522篇 |
1987年 | 494篇 |
1986年 | 427篇 |
1985年 | 503篇 |
1984年 | 567篇 |
1983年 | 529篇 |
1982年 | 709篇 |
1981年 | 620篇 |
1980年 | 541篇 |
1979年 | 371篇 |
1978年 | 350篇 |
1977年 | 352篇 |
1976年 | 291篇 |
1975年 | 274篇 |
1974年 | 280篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Data concerning rural youth drinking and driving practices werecollected from 622 junior and senior high school students innorthwest Ohio, utilizing an ex post facto cross-sectional survey-researchdesign. The results suggested that 69% of the sample had usedalcohol at least once. With regard to quantity of alcohol use,about 27% reported drinking four or more drinks at a sitting.Approximately 19% of the sample had driven under the influenceof alcohol and 35% had ridden in a car with an intoxicated school-agedriver; 35% had refused a ride from a friend who was intoxicated,while 43% had tried to stop a drunk friend from driving. Nosignificant differences were found between males and femalesregarding drinking and driving but grade level was a significantmoderating factor. As grade level increased, the frequency ofeach alcohol-related behavior increased substantially (P <0.01). This paper presents prevalence data concerning drinkingand driving among rural youth as well as recommendations forcommunity health education program development. 相似文献
72.
73.
74.
Paul Moorehead 《Canadian Medical Association journal》2005,172(11):1475
75.
76.
Rene C. Bakker Eduard M. Scholten Johan W. de Fijter Leendert C. Paul 《Transplantation reviews (Orlando, Fla.)》2004,18(1):54-64
Although extensively studied, the pathophysiologic characteristics of chronic cyclosporine (CsA) nephrotoxicity are still far from being completely understood. The recognition of chronic CsA nephrotoxicity in allografted kidneys is hampered by a lack of easily assessable sensitive and specific markers. Long-term results of CsA withdrawal trials and trials that evaluated CsA sparing or withdrawal after the diagnosis of chronic allograft nephropathy (CAN) have shown that chronic CsA nephrotoxicity has a more important role in the etiology of late transplant dysfunction than appreciated before. Various hypotheses have explained the renal structural changes of chronic CsA nephrotoxicity including ischemia, cellular toxicity, and the stimulation of renal fibrosis by growth factors or cytokines. Possible ways to prevent chronic CsA nephrotoxicity include improved therapeutic drug monitoring and CsA withdrawal or avoidance. Patients with aspecific CAN in late biopsy may benefit from withdrawal of CsA or a reduction of its dose. Current knowledge is being discussed. It is concluded that in the near future more strategies are likely to be used to prevent loss of allograft function as a result of drug toxicity. 相似文献
77.
Gerbail T Krishnamurthy Shakuntala Krishnamurthy Paul H Brown 《Journal of nuclear medicine》2004,45(11):1872-1877
The main objective of this study was to test the constancy and variability of gallbladder (GB) ejection fraction (EF) in long-term studies to (a) determine whether EF ever becomes normal once it is low, (b) determine how long it takes for the EF to become abnormal once it is found to be normal, (c) explore the cause of low EF, and (d) define objective parameters for biliary and nonbiliary abdominal pain. METHODS: Fifty-two patients (42 women, 10 men) who underwent quantitative cholescintigraphy twice (total studies, 104), over a mean period of 38.54 mo between studies, were chosen for retrospective analysis. They were divided into the following groups: control (n = 13; nonbiliary abdominal pain), chronic acalculous cholecystitis (CAC) (n = 27; biliary abdominal pain), chronic calculous cholecystitis (CCC) (n = 6; biliary abdominal pain), and opioid (n = 6; nonbiliary abdominal pain). The last group had received an opioid before cholecystokinin-8 (CCK-8) infusion in one study but not in the other study. A GBEF value of > or =35% was considered normal with a 3-min infusion and > or =50% as normal with a 10-min infusion of CCK-8. RESULTS: The mean GBEF value was reproducible between the 2 sequential studies in the control group (66.0% +/- 20.5% vs. 73.9% +/- 17.7%), CAC group (24.4% +/- 22.3% vs. 16.9% +/- 10.9%), and CCC group (20.8% +/- 20.9% vs. 27.5% +/- 34.5%) but not in the opioid group (14.8% +/- 14.6% vs. 56.5% +/- 31.7%). The severity of GBEF reduction in CAC increased with time: 7.2% +/- 8.1% within 12 mo, 16.1% +/- 14.9% in 13-47 mo, and 23.5% +/- 21.3% in 48-168 mo. None of the 27 patients with CAC developed a gallstone as detected by ultrasound during the study period. In 5 patients with CAC, a mean period of 52.6 +/- 28.9 mo was required for conversion from normal to a low EF. CCK-induced cystic duct spasm is the etiology for low EF in both CAC and CCC. CONCLUSION: Normal and low GBEF values are reproducible in long-term studies. Once the EF reaches a low value, it does not return to normal, and a normal value requires many years to become abnormal. CCK-induced cystic duct spasm is the cause of low GBEF in CAC and CCC, and the severity of EF reduction is similar for both. Exclusion of opioid intake immediately before the study is critical before attributing a low GBEF value to an irreversible GB motor dysfunction. 相似文献
78.
Normal cerebral perfusion measurements using arterial spin labeling: reproducibility, stability, and age and gender effects. 总被引:4,自引:0,他引:4
Laura M Parkes Waqar Rashid Declan T Chard Paul S Tofts 《Magnetic resonance in medicine》2004,51(4):736-743
Before meaningful conclusions can be drawn from clinical measures of cerebral blood perfusion, the precision of the measurement must be determined and set in the context of inter- and intrasubject sources of variability. This work establishes the reproducibility of perfusion measurements using the noninvasive MRI technique of continuous arterial spin labeling (CASL). Perfusion was measured in 34 healthy normal subjects. Intersubject variability was assessed, and age and gender contributions were estimated. Intersubject variation was found to be large, with up to 100% perfusion difference for subjects of the same age and gender. Repeated measurements in one subject showed that perfusion remains remarkably stable in the short term when compared with intersubject variation and the large capacity for perfusion change in the brain. A significant decrease in the ratio of gray-matter to white-matter perfusion was found with increasing age (0.79% per year (P < 0.0005)). This appears to be due mainly to a reduction in gray-matter perfusion, which was found to decrease by 0.45% per year (P = 0.04). Regional analysis suggested that the gray-matter age-related changes were predominantly localized in the frontal cortex. Whole-brain perfusion was 13% higher (P = 0.02) in females compared to males. 相似文献
79.
80.
Dinesh Paul 《Indian journal of pediatrics》1989,56(1):4-5
On September 7-8, 1988, health professionals attended a national seminar at the National Institute of Public Cooperation and Child Development in New Delhi to review policies of each government department in India that dispenses essential drugs to PHC workers. Another objective included the need to agree on what essential drugs should be distributed by the various types of PHC workers. The consensus of the group was that the different levels of health services and competence of the PHC workers should determine the basic list of PHC essential drugs. In addition, the morbidity pattern in the community, safety, effectiveness, and cost of the drugs must also determine which drugs are essential. Anganwadi workers/village health guides should all have a kit with 17 of the 75 essential drugs, such as vitamin A solution, oral rehydration solution packets, choloroquine, and chlorine tablets. In addition to the same 17 drugs, all subcenters should have in stock aspirin, metoclopramide, oral contraceptives, methergin in both tablet and injection form, and activated charcoal. Each PHC center should have all of the above and the remaining 53 drugs which include antibiotics, bronchodialators, eye drops, injections, vaccines (e.g., DPT and BCG), ointments, antileprosy drugs, and snake venom. The quantity of each drug should be based on the morbidity pattern, seasonal trend, and sickness load of the area. All PHC workers should attend inservice training where tested and effective training modules and charts in each local language are used to learn how to judiciously prescribe these drugs. Further, this essential drug program should be continuously monitored and evaluated. 相似文献