全文获取类型
收费全文 | 19113篇 |
免费 | 1301篇 |
国内免费 | 71篇 |
专业分类
耳鼻咽喉 | 342篇 |
儿科学 | 520篇 |
妇产科学 | 341篇 |
基础医学 | 2278篇 |
口腔科学 | 238篇 |
临床医学 | 1923篇 |
内科学 | 4260篇 |
皮肤病学 | 466篇 |
神经病学 | 1711篇 |
特种医学 | 675篇 |
外科学 | 2817篇 |
综合类 | 235篇 |
现状与发展 | 1篇 |
一般理论 | 18篇 |
预防医学 | 1767篇 |
眼科学 | 501篇 |
药学 | 1254篇 |
中国医学 | 23篇 |
肿瘤学 | 1115篇 |
出版年
2023年 | 95篇 |
2022年 | 113篇 |
2021年 | 440篇 |
2020年 | 269篇 |
2019年 | 409篇 |
2018年 | 519篇 |
2017年 | 354篇 |
2016年 | 420篇 |
2015年 | 463篇 |
2014年 | 670篇 |
2013年 | 954篇 |
2012年 | 1373篇 |
2011年 | 1440篇 |
2010年 | 789篇 |
2009年 | 754篇 |
2008年 | 1210篇 |
2007年 | 1314篇 |
2006年 | 1268篇 |
2005年 | 1234篇 |
2004年 | 1251篇 |
2003年 | 1083篇 |
2002年 | 958篇 |
2001年 | 169篇 |
2000年 | 146篇 |
1999年 | 188篇 |
1998年 | 253篇 |
1997年 | 168篇 |
1996年 | 143篇 |
1995年 | 149篇 |
1994年 | 133篇 |
1993年 | 109篇 |
1992年 | 101篇 |
1991年 | 89篇 |
1990年 | 68篇 |
1989年 | 75篇 |
1988年 | 70篇 |
1987年 | 77篇 |
1986年 | 72篇 |
1985年 | 78篇 |
1984年 | 89篇 |
1983年 | 66篇 |
1982年 | 86篇 |
1981年 | 108篇 |
1980年 | 78篇 |
1979年 | 62篇 |
1978年 | 48篇 |
1977年 | 62篇 |
1976年 | 42篇 |
1975年 | 37篇 |
1974年 | 36篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
972.
The impact of regular ecstasy use on memory function 总被引:1,自引:0,他引:1
Aim To assess memory impairment in a group of regular users of ecstasy compared with a group of regular users of cannabis, after accounting for possible confounding factors such as other drug use, premorbid intelligence and psychopathology.
METHOD Comparative and regression analysis was used to determine the presence or absence of a difference in memory function between 40 regular ecstasy users and 37 regular users of cannabis, who were interviewed at the National Drug and Alcohol Research Centre in Sydney, Australia. Regression analysis was used to find associations between life-time exposure to ecstasy use and memory performance. Memory function was assessed using an age-standardized memory test. Other scales were used to assess premorbid intelligence, physical and psychological health, drug withdrawal and other drug use.
Results Initial comparative analysis showed a trend towards a significantly poorer performance by the regular ecstasy-using group on the 'auditory immediate memory' and 'auditory delayed memory' indices. When regression analysis was performed an estimate of verbal intelligence was found to be the most predictive of most memory indices including 'auditory immediate memory' and 'auditory delayed memory'. Life-time exposure to ecstasy was not predictive of the memory indices. The current frequency of cannabis use was found to have some predictive effect for immediate and delayed visual memory.
Conclusion This study does not show memory impairment in a group of ecstasy users relative to cannabis using controls. The previously reported association of life-time exposure to ecstasy and memory was not found. The findings may indicate a confounding role of cannabis use, as has been recently reported. 相似文献
METHOD Comparative and regression analysis was used to determine the presence or absence of a difference in memory function between 40 regular ecstasy users and 37 regular users of cannabis, who were interviewed at the National Drug and Alcohol Research Centre in Sydney, Australia. Regression analysis was used to find associations between life-time exposure to ecstasy use and memory performance. Memory function was assessed using an age-standardized memory test. Other scales were used to assess premorbid intelligence, physical and psychological health, drug withdrawal and other drug use.
Results Initial comparative analysis showed a trend towards a significantly poorer performance by the regular ecstasy-using group on the 'auditory immediate memory' and 'auditory delayed memory' indices. When regression analysis was performed an estimate of verbal intelligence was found to be the most predictive of most memory indices including 'auditory immediate memory' and 'auditory delayed memory'. Life-time exposure to ecstasy was not predictive of the memory indices. The current frequency of cannabis use was found to have some predictive effect for immediate and delayed visual memory.
Conclusion This study does not show memory impairment in a group of ecstasy users relative to cannabis using controls. The previously reported association of life-time exposure to ecstasy and memory was not found. The findings may indicate a confounding role of cannabis use, as has been recently reported. 相似文献
973.
974.
Engleman HM McDonald JP Graham D Lello GE Kingshott RN Coleman EL Mackay TW Douglas NJ 《American journal of respiratory and critical care medicine》2002,166(6):855-859
Mandibular repositioning splints (MRSs) and continuous positive airway pressure (CPAP) are used to treat the sleep apnea/hypopnea syndrome (SAHS). There are some data suggesting that patients with milder symptoms prefer MRS, but there are few comparative data on outcomes. Therefore, we performed a randomized crossover trial of 8 weeks of CPAP and 8 weeks of MRS treatment in consecutive new outpatients diagnosed with SAHS (apnea/hypopnea index [AHI] >or= 5/hour, and >or= 2 symptoms including sleepiness). Assessments at the end of both limbs comprised home sleep study, subjective ratings of treatment value, sleepiness, symptoms, and well-being, and objective tests of sleepiness and cognition. Forty-eight of 51 recruited patients completed the trial (12 women; age [mean +/- SD], 46 +/- 9 years; Epworth 14 +/- 4; median AHI, 22/hour; interquartile ratio [IQR], 11-43/hour). Significant (p 相似文献
975.
976.
Leptin and the skeleton 总被引:5,自引:0,他引:5
977.
978.
PURPOSE: Mouthguards protect the tooth-bone complex from impact loads that occur during sporting activity. The aim of this study is to investigate the effects of varying mouthguard thickness and stiffness on the magnitude of tensile stresses in the tooth-bone-complex. METHODS: A two-dimensional, plane stress, finite element representation of a central maxillary incisor (CMI) is created. For validation purposes, displacements of the incisal edge of the unprotected tooth model are compared with in vivo displacements under similar loads. A protective mouthguard is then superimposed over the model with varied labial thickness (1-6 mm) and stiffness (9-900MPa) representing a range of designs available. A large horizontal static load of 500N is then applied to the anterior surface of the mouthguard and the resulting stresses in the tooth-bone complex are presented. It is suggested that this loading condition most accurately represent the situation occurring when a guarded tooth collides with a soft object (e.g. boxing glove). RESULTS: It is generally found that mouthguard thickness and stiffness are both desirable in terms of reducing stresses. However, the protection offered by the low-stiffness guards, regardless of thickness, is minimal. Since this low-stiffness (9MPa) is representative of the most common choice of material in mouthguard fabrication, such findings may cast doubt on the ability of popular mouthguards to redistribute stress. CONCLUSION: While few would disagree that these low-stiffness guards absorb shock during hard-object collisions (e.g. baseballs), they may not protect the tooth-bone during soft-object collisions (e.g. boxing gloves). In order to optimize their protective capabilities for a range of loads, the range of materials used in mouthguard construction may have to be reconsidered. 相似文献
979.
A short history of biological warfare 总被引:1,自引:0,他引:1
Metcalfe N 《Medicine, conflict, and survival》2002,18(3):271-282
Biological weapons have been used in war from the start of recorded history. This article reviews the history of the subject, including the outbreak of the Black Death and the use of smallpox against American Indians. The new science of microbiology was misused from soon after its start and, despite the 1925 Geneva Protocol, the Japanese experimented extensively on prisoners in China. The Allies carried out extensive research during the Second World War, notably the United Kingdom into anthrax on Gruinard Island and the United States into a variety of agents. Despite the 1972 Biological Weapons Convention (BWC), a major programme continued in the former Soviet Union (leading to an accidental outbreak of anthrax). Most recently Iraq was revealed as having an extensive programme, with weaponization of large amounts of various agents, and several terrorists groups have attempted to use biological agents as weapons. Modern developments in biotechnology could lead to even more serious developments, and effective preventive measures, including strengthening of the BWC, are imperative. 相似文献
980.
Arya N 《Medicine, conflict, and survival》2002,18(4):360-366
Figures for deaths from private use of small arms, particularly in children and young people, are summarized and responses to the discussion of these figures in a recent editorial in the British Medical Journal are considered. It is contended that the figures highlight a major public health problem, particularly in the United States. Further, this article emphasizes that the politicization of the debate by the US gun lobby should not be allowed to obscure the conflict-related consequences of small arms in the developing world. 相似文献