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   3408篇
  免费   191篇
  国内免费   7篇
耳鼻咽喉   77篇
儿科学   209篇
妇产科学   246篇
基础医学   343篇
口腔科学   192篇
临床医学   334篇
内科学   740篇
皮肤病学   78篇
神经病学   307篇
特种医学   152篇
外科学   382篇
综合类   8篇
一般理论   1篇
预防医学   123篇
眼科学   58篇
药学   150篇
中国医学   2篇
肿瘤学   204篇
  2023年   20篇
  2022年   50篇
  2021年   88篇
  2020年   45篇
  2019年   92篇
  2018年   98篇
  2017年   64篇
  2016年   90篇
  2015年   94篇
  2014年   110篇
  2013年   165篇
  2012年   236篇
  2011年   215篇
  2010年   124篇
  2009年   119篇
  2008年   212篇
  2007年   214篇
  2006年   232篇
  2005年   200篇
  2004年   185篇
  2003年   167篇
  2002年   139篇
  2001年   26篇
  2000年   42篇
  1999年   38篇
  1998年   15篇
  1997年   20篇
  1996年   21篇
  1995年   20篇
  1994年   20篇
  1993年   16篇
  1992年   34篇
  1991年   30篇
  1990年   27篇
  1989年   31篇
  1988年   22篇
  1987年   23篇
  1986年   25篇
  1985年   22篇
  1984年   31篇
  1983年   14篇
  1982年   11篇
  1981年   14篇
  1980年   10篇
  1978年   12篇
  1977年   12篇
  1975年   8篇
  1974年   11篇
  1973年   9篇
  1968年   7篇
排序方式: 共有3606条查询结果,搜索用时 15 毫秒
1.
2.
Studies on the exposure of children to sugar-sweetened beverages (SSBs) at an early age may contribute to better understand the common causes and the temporal order of the relationships between obesity and asthma in early childhood. The objective of this study was to estimate the association between SSB and child asthma traits in the 2nd year of life, modeling direct and indirect pathways mediated by the highest BMI-z of the child and allergic inflammation. Data from the BRISA cohort, São Luís-MA, Brazil (n = 1140), were obtained from the baseline and from the follow-up performed at the 2nd year of life. The main explanatory variable was the calories from added sugars in SSBs as a percentage of the total daily energy intake. The outcome child asthma traits was a latent variable deduced from four indicators: medical diagnosis of asthma, wheezing, emergency visit due to intense wheezing, and medical diagnosis of rhinitis. A high percentage of daily calories from sugars added to SSBs was directly associated with higher values of child asthma traits (standardized coefficient (SC = 0.073; P = .030)). High levels of eosinophils were also directly associated with child asthma traits (SC = 0.118; P = .049). No mediation pathways were observed via greater BMI-z or eosinophil counts. Therefore, early exposure of children to SSB may contribute to increased risk of childhood asthma, preceding the link between sugar consumption and overweight/obesity, not yet evident in children in the first 2 years of life.  相似文献   
3.
4.
5.
6.
Lipid profiles were determined in three groups of children: children with asthma receiving long-term therapy with slow-releasing theophylline, children with asthma not treated with theophylline, and a control group of children without asthma. Total cholesterol, high-density lipoprotein cholesterol, and apolipoprotein A levels and the high-density lipoprotein/low-density lipoprotein ratio were significantly higher among theophylline-treated children. The observed changes do not seem to increase the risks of atherosclerotic coronary artery disease.  相似文献   
7.
Thirty-three patients with primary gastrointestinal lymphoma (GIL) followed at Ankara University Medical School have been evaluated. The most frequent locations of the disease are the small intestine (48.4%) and the stomach (39.3%). The intermediate and high grade lymphomas constitute 84.8% of the cases. The mean age of the patients with small intestinal lymphoma is 28.7 years and 47.1 years for those with gastric lymphoma. The patients treated with surgery and chemotherapy (S+CT) have a longer survival than those treated with chemotherapy (CT) alone. In conclusion: 1) Small intestinal lymphoma occurs more frequently than gastric lymphoma in our study. 2) The median age of the Turkish patients with primary GIL is approximately 10 years less than those in the Western countries. 3) The therapeutic results of S+CT are superior to those of CT in the early stages of the disease.  相似文献   
8.
BACKGROUND: Evidence of increased asthma and allergic response among urban versus rural residents has been reported. OBJECTIVE: To evaluate the prevalence of allergic response among asthmatic children from urban and rural areas living within close proximity. METHODS: In all, 448 asthmatic children from urban (363) and rural (85) areas were studied. The study group consisted of 234 9-year-olds and 214 12-year-olds. A health questionnaire was completed on each child who subsequently underwent allergic skin prick tests (SPTs). RESULTS: There was significantly more positive SPT response to house-dust mite, mold, cat, and cypress among asthmatic children from urban areas compared with children living in rural areas: 58.3% versus 37.6%, 46.1% versus 31.8%, 17.45 versus 5.9%, and 26.2% versus 15.3%, respectively. Positive SPT for indoor allergens were significantly greater among asthmatic urban residents than asthmatic rural residents: 63.3% versus 45.5%, respectively (P < 0.02). Positive SPT response to all the allergens checked was higher among the 12-year-old age group when compared with the 9-year-olds, 34.6% versus 22.7%, respectively (P = 0.05). CONCLUSIONS: Allergic response measured by SPT is significantly more common among asthmatic children from urban areas as opposed to rural, even though both areas are within small distance of one another. Further, asthmatic children living in urban areas demonstrated more allergic response to both indoor and outdoor allergens. The allergic response tends to increase with increased age in both urban and rural asthmatic children.  相似文献   
9.
Gene amplification occurs frequently in tumour tissues yet is,in general, non-inheritable. To study the molecular mechanismsconferring this restraint, we created transgenic mice carryinga human butyrylcholinesterase (BCHE) coding sequence, previouslyfound to be amplified in a father and son. Blot hybridizationof tail DNA samples revealed somatic transgene amplificationswith variable restriction patterns and intensities, suggestingthe occurrence of independent amplification events, in 31% (11/35)of mice from the FII generation but in only 3.5% (2/58) of theFII and FIV generations. In contrast, >10-fold amplificationsof the BCHE transgene and the endogenous acetylcholinesteraseand c-raf genes appeared in both testis and epididymis DNA from>80% of FIII mice. Drastic, selective reductions in testisBCHEmRNA but not in actin mRNA were detected by the PCR amplificationof testis cDNA from the transgenic mice, and apparently resultedin the limited transmission of amplified genes. The testicularamplification of the BCHE transgene may potentially representa general phenomenon with clinical implications in human infertility.  相似文献   
10.
The present study focused on in vitro release of polylactide-nanoencapsulated tyrphostin AG-1295, a potential agent for local therapy of restenosis. The drug was formulated in matrix-type nanoparticles, termed nanospheres (NS) using the nanoprecipitation method. AG-1295 is a model for low-molecular weight lipophilic compounds, the release behavior of which cannot be adequately characterized by existing methods. An in vitro release technique suitable for optimizing the nanoparticulate formulation release behavior was developed through a novel external sink method and an in situ release method utilizing the environmental sensitivity of the AG-1295 fluorescence spectrum. Similar tendencies were demonstrated by both methods in drug release studied as a function of selected NS preparation variables. The release properties of the drug fractions varying in their binding mode to the carrier particles were studied by the external sink method. The NS surface-adsorbed drug exhibited a significantly higher release rate compared to the drug entrapped in the polymeric matrix. The in situ release of the encapsulated drug was analyzed using the diffusion models of release from a matrix-type sphere. The release was shown to be a composite process, with a burst phase attributed largely to the rapid dissociation of the surface-bound AG-1295. The diffusion-controlled phase exhibited an alteration in kinetic pattern obviously due to the drug distribution between polymeric matrix compartments differing in their permeability. Drug in vitro release investigation may be effectively used to characterize the drug-carrier interaction and internal carrier structure in nanoparticulate formulations, as well as optimize the release behavior in respect to their therapeutic application.  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