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   8913篇
  免费   641篇
  国内免费   11篇
耳鼻咽喉   45篇
儿科学   420篇
妇产科学   168篇
基础医学   999篇
口腔科学   631篇
临床医学   790篇
内科学   1524篇
皮肤病学   109篇
神经病学   826篇
特种医学   409篇
外国民族医学   2篇
外科学   1498篇
综合类   104篇
一般理论   6篇
预防医学   702篇
眼科学   232篇
药学   538篇
中国医学   2篇
肿瘤学   560篇
  2021年   121篇
  2019年   106篇
  2018年   128篇
  2017年   103篇
  2016年   91篇
  2015年   94篇
  2014年   155篇
  2013年   241篇
  2012年   303篇
  2011年   372篇
  2010年   214篇
  2009年   209篇
  2008年   374篇
  2007年   369篇
  2006年   385篇
  2005年   370篇
  2004年   379篇
  2003年   301篇
  2002年   310篇
  2001年   270篇
  2000年   268篇
  1999年   224篇
  1998年   86篇
  1997年   82篇
  1996年   87篇
  1995年   83篇
  1992年   212篇
  1991年   207篇
  1990年   208篇
  1989年   229篇
  1988年   200篇
  1987年   216篇
  1986年   188篇
  1985年   173篇
  1984年   166篇
  1983年   106篇
  1982年   73篇
  1981年   69篇
  1980年   73篇
  1979年   137篇
  1978年   110篇
  1977年   91篇
  1976年   109篇
  1975年   98篇
  1974年   109篇
  1973年   130篇
  1972年   102篇
  1971年   84篇
  1970年   79篇
  1968年   69篇
排序方式: 共有9565条查询结果,搜索用时 11 毫秒
991.
BACKGROUND: (1-3)-Beta-D-glucan is a fungal cell wall component, suspected to cause respiratory symptoms in adults. However, very little is known on the possible health effects of (1-3)-beta-D-glucan during infancy. We examined the association between (1-3)-beta-D-glucan exposure and the prevalence of allergen sensitization and wheezing during the first year of life in a birth cohort of 574 infants born to atopic parents. Endotoxin exposure was included as a possible confounder. METHODS: (1-3)-Beta-D-glucan and endotoxin exposures were measured in settled dust collected from infants' primary activity rooms. The primary outcomes at approximately age one included parental reports of recurrent wheezing and allergen sensitization evaluated by skin prick testing to a panel of 15 aeroallergens as well as milk and egg white. RESULTS: Exposure to high (1-3)-beta-D-glucan concentration (within fourth quartile) was associated with reduced likelihood of both recurrent wheezing [adjusted OR (aOR) = 0.39, 95% CI = 0.16-0.93] and recurrent wheezing combined with allergen sensitization (aOR = 0.13, 95% CI = 0.03-0.61). Similar trends were found between (1-3)-beta-D-glucan concentrations and allergen sensitization (aOR = 0.57, 95% CI = 0.30-1.10). In contrast, recurrent wheezing with or without allergen sensitization was positively associated with low (1-3)-beta-D-glucan exposure within the first quartile (aOR = 3.04, 95% CI = 1.25-7.38; aOR = 4.89, 95% CI = 1.02-23.57). There were no significant associations between endotoxin exposure and the studied health outcomes. CONCLUSIONS: This is the first study to report that indoor exposure to high levels of (1-3)-beta-D-glucan (concentration >60 microg/g) is associated with decreased risk for recurrent wheezing among infants born to atopic parents. This effect was more pronounced in the subgroup of allergen-sensitized infants.  相似文献   
992.
The results of a traditional visual mold inspection were compared to a mold evaluation based on the Relative Moldiness Index (RMI). The RMI is calculated from mold-specific quantitative PCR (MSQPCR) measurements of the concentration of 36 species of molds in floor dust samples. These two prospective mold evaluations were used to classify the mold condition in 271 homes of infants. Later, the development of respiratory illness was measured in the infants living in these homes and the predictive value of each classification system was evaluated. The binary classification of homes as either moldy or non-moldy by on-site visual home inspection was not predictive of the development of respiratory illness (wheeze and/or rhinitis) (P=0.27). Conversely, a method developed and validated in this paper, using the RMI index fit to a logistic function, can be used to predict the occurrence of illness in homes and allows stake-holders the choice among various levels of risk.  相似文献   
993.
994.
OBJECTIVE: We examined differences in preferences for the EQ-5D health states among blacks, Hispanics, and others living in the United States. STUDY DESIGN AND SETTING: A multi-stage probability sample was selected from the adult U.S. population. Each respondent valued a subset of the 243 EQ-5D health states. Regression analysis was used to analyze differences in mean valuations for 13 health states among the racial/ethnic groups. First, we compared unadjusted mean valuations among the three groups. Second, we evaluated differences in mean valuations among the groups after adjusting for other sociodemographic characteristics. Third, we evaluated the impact of race/ethnicity on estimates derived from the U.S. health state valuation (i.e., D1) model. RESULTS: Valuations differed among the groups for seven of the 13 health states, and these differences persisted after adjusting for other sociodemographic factors. Blacks appeared to perceive extreme health problems to be associated with less disutility than did members of the other two groups. CONCLUSION: Within the United States, there exist racial/ethnic differences in the perceived desirability of the EQ-5D health states that cannot be readily explained by socioeconomic disparities.  相似文献   
995.
996.
997.
998.
Arildone is an aryl diketone which is inhibitory in vitro against herpes simplex virus type 2 at a concentration of 2 micrograms/ml or less. One hundred forty-five patients with recurrent genital herpes were enrolled in a multicenter, randomized, placebo-controlled, double-blind trial to evaluate the efficacy and safety of an 8% arildone cream. Patients initiated therapy a mean of 9.9 h and a maximum of 24 h after the reported onset of lesions and applied medication 6 times daily for 7 days. The duration of viral shedding was shorter among women (P less than 0.05) and the duration of local itching was shorter among men (P less than 0.05) in patients that received arildone than in those that received placebo, but there were no significant differences between treatment groups in duration of pain, time to crusting or healing of lesions, or percentage of patients developing new lesions. Mild local irritation after application of ointment was common and occurred equally in both treatment groups. Despite early application, topical arildone cream was ineffective in the therapy of acute recurrences of genital herpes.  相似文献   
999.
1000.
Obituaries     
Platelet aggregation by adenosine diphosphate (ADP) is a self-limited and reversible process. An application of this phenomenon is described which allows removal of the platelets from large volumes of fresh platelet rich plasma (PRP) for the preparation of platelet concentrates. The macroscopic platelet clumps resulting from a concentration of 10 μgm ADP per ml of PRP are removed by centrifugation at 50 × g for 10 minutes. Resuspension of these platelets in 20 cc of native plasma results in a platelet concentrate that is 80 to 90 per cent as effective per unit as PRP in its ability to elevate the platelet count in recipients. Such concentrates are superior to concentrates prepared by other methods. The posttransfusion survival of ADP platelets compares favorably with the survival of platelets administered as PRP. There is evidence of minor sequestration but there is no apparent irreversible damage to platelets handled in this manner. Alkaline plasma and increase in plasma ionized calcium enhance the ADP aggregation and improve the efficiency of in vitro separation of platelets from PRP. However, the resulting concentrate is less effective in vivo, because of prolonged and slowly reversible clumping, and failure of these platelets to circulate.  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