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   694235篇
  免费   53140篇
  国内免费   1431篇
耳鼻咽喉   10310篇
儿科学   19749篇
妇产科学   20042篇
基础医学   99431篇
口腔科学   20452篇
临床医学   60326篇
内科学   131951篇
皮肤病学   13627篇
神经病学   56287篇
特种医学   28158篇
外国民族医学   141篇
外科学   108869篇
综合类   19710篇
现状与发展   2篇
一般理论   209篇
预防医学   53655篇
眼科学   16355篇
药学   51774篇
  13篇
中国医学   1290篇
肿瘤学   36455篇
  2018年   5913篇
  2015年   6197篇
  2014年   8951篇
  2013年   13468篇
  2012年   18163篇
  2011年   18981篇
  2010年   11208篇
  2009年   10431篇
  2008年   17985篇
  2007年   19701篇
  2006年   19603篇
  2005年   19276篇
  2004年   18938篇
  2003年   18297篇
  2002年   17564篇
  2001年   28555篇
  2000年   29177篇
  1999年   24732篇
  1998年   7404篇
  1997年   6843篇
  1996年   6811篇
  1995年   6401篇
  1994年   6192篇
  1992年   21335篇
  1991年   20938篇
  1990年   20498篇
  1989年   19834篇
  1988年   18533篇
  1987年   18224篇
  1986年   17355篇
  1985年   16793篇
  1984年   13103篇
  1983年   11252篇
  1982年   7147篇
  1981年   6512篇
  1980年   6143篇
  1979年   13493篇
  1978年   9632篇
  1977年   8181篇
  1976年   7436篇
  1975年   8126篇
  1974年   10105篇
  1973年   9741篇
  1972年   9255篇
  1971年   8565篇
  1970年   8191篇
  1969年   7898篇
  1968年   7127篇
  1967年   6615篇
  1966年   6100篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
Maternal and Child Health Journal - Objective The association between and commonality of risk factors for poor self-rated oral health (SROH) and general health (SRGH) among new mothers has not been...  相似文献   
63.
The focus on recovery, not just symptom reduction, in mental health care brings a need for psychometrically sound measures of recovery. This study examined the factor structure and sensitivity to change of a common measure of mental health recovery, the Recovery Assessment Scale (RAS). We conducted a secondary data analysis from a randomized clinical trial of self-management for depression (n = 302). We tested both bifactor and the previously found five-factor model. Sensitivity to change was examined three ways: (1) between the intervention and control group; (2) across time in the intervention group; and (3) in those whose depression remitted. The previous five-factor model was supported. One subscale, no domination by symptoms, was particularly sensitive to change and showed sensitivity to change whereas the subscale reliance on others did not show change in any of the comparisons. Results suggest that the subscales of the RAS should be examined separately in future studies of recovery.  相似文献   
64.
65.
Inhalation of ash can be of great concern for affected communities, during and after volcanic eruptions. Governmental and humanitarian agencies recommend and distribute a variety of respiratory protection (RP), most commonly surgical masks. However, there is currently no evidence on how effective such masks are in protecting wearers from volcanic ash. In Part I of this study (Mueller et al., 2018), we assessed the filtration efficiency (FE) of 17 materials from different forms of RP against volcanic ash and a surrogate, low-toxicity dust, Aloxite. Based on those results, we now present the findings from a volunteer simulation study to test the effect of facial fit through assessment of Total Inward Leakage (TIL).Four different disposable RP types that demonstrated very high median FE (≥96% for Aloxite; ≥89% for volcanic ash) were tested without provision of training on fit. These were an industry-certified mask (N95-equiv.); a surgical mask from Japan designed to filter PM2.5; a flat-fold basic mask from Indonesia; and a standard surgical mask from Mexico, which was also tested with an added medical bandage on top, as an additional intervention to improve fit.Ten volunteers (6 female, 4 male) were recruited. Each RP type was worn by volunteers under two different conditions simulating cleaning-up activities during/after volcanic ashfall. Each activity lasted 10?min and two repeats were completed for each RP type per activity. Dust (as PM2.5) concentration inside and outside the mask was measured with two TSI SidePak aerosol monitors (Models AM510 and AM520, TSI, Minnesota, USA) to calculate TIL. A questionnaire was administered after each test to collect perceptions of fit, comfort, protection and breathability.The best-performing RP type, across both activities, was the industry-certified N95-equiv. mask with 9% mean TIL. The standard surgical mask and the basic flat-fold mask both performed worst (35% TIL). With the additional bandage intervention, the surgical mask mean TIL improved to 24%. The PM2.5 surgical mask performed similarly, with 22% TIL. The N95-equiv. mask was perceived to provide the best protection, but was also perceived as being uncomfortable and more difficult to breathe through.This study provides a first objective evidence base for the effectiveness of a selection of RP types typically worn around the world during volcanic crises. The findings will help agencies to make informed decisions on the procurement and distribution of RP in future eruptions.  相似文献   
66.
67.
68.
Italian-born migrants (post-WWII) are the largest non-English-speaking background migrant group in South Australia. A cross-sectional, inter-country comparison using independent samples (40–69 years of age) from two (one in Australia, one in Italy) similar risk factor and chronic disease surveillance systems. None of the three groups (Italians, Australian-born and Italian-born Australians) had definitively worse health although the Italians had high rates for four of the seven risk factors reported (current high blood pressure, current high cholesterol, current smoking, eating less than five fruit and/or vegetables per day) than Australian-born and Italian-born Australians. Italian-born Australians had higher rates for insufficient physical activity, overweight/obese, poor self-reported health and diabetes. Australian respondents were more likely to report having two or more drinks of alcohol per day. Issues facing an ageing population require appropriate health care needs and an assessment of structural or cultural barriers to health services.  相似文献   
69.
A consistent analytical method incorporating sulfuric acid (H2SO4) digestion and ICP-MS quantification has been developed for TiO2 quantification in biotic and abiotic environmentally relevant matrices. Sample digestion in H2SO4 at 110°C provided consistent results without using hydrofluoric acid or microwave digestion. Analysis of seven replicate samples for four matrices on each of 3 days produced Ti recoveries of 97%?±?2.5%, 91?% ±?4.0%, 94%?±?1.8%, and 73?% ±?2.6% (mean?±?standard deviation) from water, fish tissue, periphyton, and sediment, respectively. The method demonstrated consistent performance in analysis of water collected over a 1 month.  相似文献   
70.
Two two-year double-blind clinical trials were undertaken involving the newly-erupted first permanent molars of 133 children aged 5-6 years at the outset. In one study of 76 subjects, half the teeth were sealed with the filled sealants Prismashield or Estiseal. In the other study of 58 children, half were again sealed with Prismashield, and the others with the unfilled Concise white sealant, by a community dental service hygienist, as part of her routine dental duties. Subjects were examined under blind conditions at 6 monthly intervals and, by 24 months in the first study, 71 per cent of Prismashield sites were intact and caries-free, compared with only 53 per cent of Estiseal-treated tooth units (P less than 0.001). In the second study comparing Prismashield and Concise, by two years, 81 per cent of Prismashield resins were complete, compared with 88 per cent of the nonfilled Concise material. There were, however, no differences noted with respect to buccal and palatal site retention for either study. It can be concluded that Estiseal is a poorer material than Prismashield, certainly in relation to its bulk retention properties. Nonetheless it is possible that, along with other tooth-coloured/transparent resins, small fragments may not be as readily detectable as is the case with the unfilled Concise white sealant. However, as the abrasion resistance of unfilled materials is poorer than that of filled resins, the similar buccal/palatal site retention for Prismashield and Concise was also unexpected. Nevertheless this study illustrates again the value of sealant placement in the erupting first permanent molars of 5-6-year-old children, at a time when these teeth are most susceptible to carious attack.  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