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   18158篇
  免费   1432篇
  国内免费   85篇
耳鼻咽喉   223篇
儿科学   511篇
妇产科学   295篇
基础医学   2314篇
口腔科学   258篇
临床医学   1981篇
内科学   4564篇
皮肤病学   232篇
神经病学   1308篇
特种医学   654篇
外科学   2803篇
综合类   265篇
一般理论   9篇
预防医学   1271篇
眼科学   629篇
药学   1097篇
中国医学   50篇
肿瘤学   1211篇
  2023年   89篇
  2022年   133篇
  2021年   279篇
  2020年   184篇
  2019年   353篇
  2018年   359篇
  2017年   297篇
  2016年   301篇
  2015年   329篇
  2014年   503篇
  2013年   753篇
  2012年   1065篇
  2011年   1033篇
  2010年   639篇
  2009年   626篇
  2008年   1066篇
  2007年   1131篇
  2006年   1156篇
  2005年   1092篇
  2004年   1065篇
  2003年   1015篇
  2002年   946篇
  2001年   300篇
  2000年   290篇
  1999年   249篇
  1998年   204篇
  1997年   186篇
  1996年   146篇
  1995年   192篇
  1994年   151篇
  1993年   121篇
  1992年   207篇
  1991年   167篇
  1990年   171篇
  1989年   161篇
  1988年   171篇
  1987年   163篇
  1986年   144篇
  1985年   124篇
  1984年   130篇
  1983年   138篇
  1982年   135篇
  1981年   121篇
  1980年   116篇
  1979年   98篇
  1978年   98篇
  1977年   108篇
  1976年   83篇
  1975年   61篇
  1974年   68篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
1.
ABSTRACT

The lack of stable housing can impair access and continuity of care for patients living with human immunodeficiency virus (HIV). This study investigated the relationship between housing status assessed at multiple time points and several core HIV-related outcomes within the same group of HIV patients experiencing homelessness. Patients with consistently stable housing (CSH) during the year were compared to patients who lacked CSH (non-CSH group). The study outcomes included HIV viral load (VL), CD4 counts, and health care utilization. Multivariable and propensity weighted analyses were used to assess outcomes adjusting for potential group differences. Of 208 patients, 88 (42%) had CSH and 120 (58%) were non-CSH. Patients with CSH had significantly higher proportion of VL suppression and higher mean CD4 counts. The frequency of nurse visits in the CSH group was less than a half of that in the non-CSH group. Patients with CSH were less likely to be admitted to the medical respite facility, and if admitted, their length of stay was about a half of that for the non-CSH group. Our study findings show that patients with CSH had significantly better HIV virologic control and immune status as well as improved health care utilization.  相似文献   
2.
BACKGROUND: Human serum albumin (HAS) is used to treat hypoproteinaemia in neonates and as a volume expander. The aim of this study was to quantify the decrease in serum concentration of ionized magnesium ([Mg2+]) when human serum albumin is added to neonatal serum in vitro. METHODS: Human serum albumin was added to 20 cord serum samples of term infants to reach incremental concentrations of 0 to 20.0 g/l and [Mg2+] were measured. RESULTS: Serum [Mg2+] decreased significantly with the addition of serum albumin. At incremental serum albumin concentration of 10 to 20 g/l, which is within the range of the desired aim in the treatment of hypoalbuminaemia, the magnitude of the decrease in serum [Mg2+] was approximately 0.041 to 0.052 mmol/l (10 to 13 per cent) from the average baseline value. CONCLUSION: The addition of albumin causes a decrease in [Mg2+]. From this in vitro study we speculate that fast infusion of albumin in human neonates may potentially cause a clinically significant decrease in serum [Mg2+].  相似文献   
3.
4.
5.
6.
7.
The effects of chemical exposure on the developing nervous system have been documented in both humans and animals for a variety of agents. However, the comparability of these effects has not been carefully evaluated to determine the predictability of animal models to adverse effects in humans. A workshop sponsored by the U.S. Environmental Protection Agency (EPA) and the National Institute on Drug Abuse was held on April 11-13, 1989, to address the Qualitative and Quantitative Comparability of Human and Animal Developmental Neurotoxicity. Invited experts were asked to review the human and animal data on several agents that are known to cause developmental neurotoxicity in humans, including lead, methylmercury, selected abused agents, anticonvulsants, polychlorinated biphenyls (PCBs), ethanol and X-irradiation, and to make quantitative comparisons on a specific end point basis as well as on a functional category basis. In addition, they were asked to make quantitative comparisons when adequate dose-effect data were available. The data also were evaluated in the context of the proposed EPA developmental neurotoxicity testing battery to determine whether or not the battery would adequately detect the effects of each agent. Finally, four work groups were asked to reach consensus on issues relating to: 1) comparability of end points across species for developmental neurotoxicity; 2) testing methods in developmental neurotoxicity for use in human risk assessment; 3) weight-of-evidence and quantitative evaluation of data from developmental neurotoxicity studies; and 4) triggers for developmental neurotoxicity testing.  相似文献   
8.
9.
10.
BACKGROUND: Season of birth (SOB) has been regarded as a risk factor for atopy. The aim of this study was to explore the relationship between season of birth (SOB) and later development of atopic disease in children and adolescents. METHODS: A total of 1,007 randomly selected subjects, 7 to 17 years of age, who were living in urban Copenhagen, Denmark were studied. All participants were interviewed about respiratory symptoms and possible risk factors for atopic disease. Skin test reactivity, serum total immunoglobulin E (IgE), and airway responsiveness were measured using standard techniques. RESULTS: The overall risk of atopy, as judged by skin test reactivity and serum total IgE, was the same regardless of SOB. On the contrary, asthma was more common in subjects born in the autumn compared with subjects born during the remaining part of the year (12.4% vs. 5.6%), OR = 2.40, 95% CI (1.56-3.94), p < 0.001. This was observed both for atopic asthma OR = 2.41, 95% CI (1.25-4.64), p = 0.007, non-atopic asthma, OR = 2.35, 95% CI (1.14-4.83), p = 0.02, and house dust mite (HDM) sensitive airway hyperresponsiveness, OR = 3.00, 95% CI (1.44-6.24), p = 0.002. Rhinitis and pollen allergy were not significantly related to SOB. CONCLUSIONS: Atopy itself is independent of season of birth, whereas asthma is more prevalent among subjects born during the autumn. Regarding asthma, these results suggest that the first months of life enclose a period of particular vulnerability towards environmental risk factors, especially exposure to aeroallergens like HDM.  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