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   4252篇
  免费   283篇
  国内免费   14篇
耳鼻咽喉   44篇
儿科学   141篇
妇产科学   125篇
基础医学   680篇
口腔科学   91篇
临床医学   385篇
内科学   854篇
皮肤病学   86篇
神经病学   407篇
特种医学   185篇
外科学   534篇
综合类   46篇
一般理论   3篇
预防医学   263篇
眼科学   49篇
药学   374篇
中国医学   9篇
肿瘤学   273篇
  2022年   35篇
  2021年   94篇
  2020年   44篇
  2019年   93篇
  2018年   89篇
  2017年   79篇
  2016年   81篇
  2015年   107篇
  2014年   124篇
  2013年   208篇
  2012年   265篇
  2011年   318篇
  2010年   188篇
  2009年   141篇
  2008年   279篇
  2007年   296篇
  2006年   234篇
  2005年   222篇
  2004年   192篇
  2003年   169篇
  2002年   158篇
  2001年   74篇
  2000年   77篇
  1999年   85篇
  1998年   47篇
  1997年   29篇
  1996年   20篇
  1995年   34篇
  1994年   27篇
  1993年   25篇
  1992年   48篇
  1991年   44篇
  1990年   40篇
  1989年   44篇
  1988年   45篇
  1987年   30篇
  1986年   27篇
  1985年   33篇
  1984年   32篇
  1983年   31篇
  1980年   16篇
  1979年   25篇
  1978年   18篇
  1977年   20篇
  1976年   23篇
  1974年   28篇
  1973年   19篇
  1972年   23篇
  1971年   18篇
  1970年   19篇
排序方式: 共有4549条查询结果,搜索用时 15 毫秒
61.
BACKGROUND AND OBJECTIVE: Rapid identification and investigation of potential outbreaks is key to limiting transmission in the healthcare setting. Manual review of laboratory results remains a cumbersome, time-consuming task for infection control practitioners (ICPs). Computer-automated techniques have shown promise for improving the efficiency and accuracy of surveillance. We examined the use of automated control charts, provided by an automated surveillance system, for detection of potential outbreaks. SETTING: A 656-bed academic medical center. METHODS: We retrospectively reviewed 13 months (November 2001 through November 2002) of laboratory-patient data, comparing an automated surveillance application with standard infection control practices. We evaluated positive predictive value, sensitivity, and time required to investigate the alerts. An ICP created 75 control charts. A standardized case investigation form was developed to evaluate each alert for the likelihood of nosocomial transmission based on temporal and spatial overlap and culture results. RESULTS: The 75 control charts were created in 75 minutes and 18 alerts fired above the 3-sigma level. These were independently reviewed by an ICP and associate hospital epidemiologist. The review process required an average of 20 minutes per alert and the kappa score between the reviewers was 0.82. Eleven of the 18 alerts were determined to be potential outbreaks, yielding a positive predictive value of 0.61. Routine surveillance identified 5 of these 11 alerts during this time period. CONCLUSION: Automated surveillance with user-definable control charts for cluster identification was more sensitive than routine methods and is capable of operating with high specificity and positive predictive value in a time-efficient manner.  相似文献   
62.
Objective: Alendronate and calcitonin are antiresorptive drugs that were used for the treatment of postmenopausal osteoporosis and were shown to increase bone mineral density (BMD). However, the effect of both drugs in daily clinical practice may differ from that observed in clinical trials.Method: About 50 postmenopausal osteoporotic women were observed during their first year of treatment. Among them, 32 patients used alendronate and 18 used calcitonin. Lumbar spine and femoral neck BMD were measured by dual energy X-ray absorptiometry (DXA) at baseline and after 1 year of therapy. Biochemical markers (B-ALP – bone-specific alkaline phosphatase, OTC – osteocalcin and DPD/UCr – deoxypyridinoline/creatinine ratio) of bone metabolism were measured at baseline and 6 months later. Patient compliance was assumed by tablet counting and verified at interview. Each patient was further questioned about her attitude towards the treatment, as well as her dairy product intake, physical activity, use of other medications, smoking and social status.Main outcome measure: (1) Annual percent change in BMD in lumbar spine and femoral neck after the one-year treatment with either alendronate or calcitonin. (2) The change in biochemical markers of bone turnover.Results: The lumbar spine BMD significantly increased by 7.0% (P < 0.001), the femoral neck BMD by 4.3% (P < 0.01). OTC, B-ALP and DPD/UCr decreased significantly during the therapy with alendronate. Compliance with therapy was 79% (95% CI 68–90%). In the calcitonin-treated group, the lumbar spine BMD significantly increased by 3.1 % (P < 0.05), while the femoral neck BMD remained unchanged. OTC, B-ALP and DPD/UCr did not change significantly during the treatment with calcitonin. Compliance with calcitonin therapy was 87% (95% CI 63–110%). The annual change of BMD in both treatment groups was independent on all questioned factors.Conclusion: In daily practice, alendronate enhanced significantly BMD both in lumbar spine and femoral neck. Calcitonin showed increase only in the lumbar spine BMD.  相似文献   
63.
The electrochemical behavior of polycrystalline TiO2 anatase coatings prepared by a one-step hydrothermal synthesis on commercially pure (CP) Ti grade 2 and a Ti13Nb13Zr alloy for bone implants was investigated in Hank’s solution at 37.5 °C. The aim was to verify to what extent the in-situ-grown anatase improved the behavior of the substrate in comparison to the bare substrates. Tafel-plot extrapolations from the potentiodynamic curves revealed a substantial improvement in the corrosion potentials for the anatase coatings. Moreover, the coatings grown on titanium also exhibited lower corrosion-current densities, indicating a longer survival of the implant. The results were explained by considering the effects of crystal morphology, coating thickness and porosity. Evidence for the existing porosity was obtained from corrosion and nano-indentation tests. The overall results indicated that the hydrothermally prepared anatase coatings, with the appropriate morphology and surface properties, have attractive prospects for use in medical devices, since better corrosion protection of the implant can be expected.  相似文献   
64.
65.
66.
67.
Attention-deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental disorder with impairments across the lifespan. The persistence of ADHD is associated with considerable liability to neuropsychiatric co-morbidity such as depression, anxiety and substance use disorder. The substantial heritability of ADHD is well documented and recent genome-wide analyses for risk genes revealed synaptic adhesion molecules (e.g. latrophilin-3, LPHN3; fibronectin leucine-rich repeat transmembrane protein-3, FLRT3), glutamate receptors (e.g. metabotropic glutamate receptor-5, GRM5) and mediators of intracellular signalling pathways (e.g. nitric oxide synthase-1, NOS1). These genes encode principal components of the molecular machinery that connects pre- and postsynaptic neurons, facilitates glutamatergic transmission, controls synaptic plasticity and empowers intersecting neural circuits to process and refine information. Thus, identification of genetic variation affecting molecules essential for the formation, specification and function of excitatory synapses is refocusing research efforts on ADHD pathogenesis to include the long-neglected glutamate system.  相似文献   
68.
Localization of the HIV type-1 (HIV-1) Gag protein on the plasma membrane (PM) for virus assembly is mediated by specific interactions between the N-terminal myristoylated matrix (MA) domain and phosphatidylinositol-(4,5)-bisphosphate [PI(4,5)P2]. The PM bilayer is highly asymmetric, and this asymmetry is considered crucial in cell function. In a typical mammalian cell, the inner leaflet of the PM is enriched in phosphatidylserine (PS) and phosphatidylethanolamine (PE) and contains minor populations of phosphatidylcholine (PC) and PI(4,5)P2. There is strong evidence that efficient binding of HIV-1 Gag to membranes is sensitive not only to lipid composition and net negative charge, but also to the hydrophobic character of the acyl chains. Here, we show that PS, PE, and PC interact directly with MA via a region that is distinct from the PI(4,5)P2 binding site. Our NMR data also show that the myristoyl group is readily exposed when MA is bound to micelles or bicelles. Strikingly, our structural data reveal a unique binding mode by which the 2′-acyl chain of PS, PE, and PC lipids is buried in a hydrophobic pocket whereas the 1′-acyl chain is exposed. Sphingomyelin, a major lipid localized exclusively on the outer layer of the PM, does not bind to MA. Our findings led us to propose a trio engagement model by which HIV-1 Gag is anchored to the PM via the 1′-acyl chains of PI(4,5)P2 and PS/PE/PC and the myristoyl group, which collectively bracket a basic patch projecting toward the polar leaflet of the membrane.  相似文献   
69.
Team Reach Out Biloxi is a nursing student-initiated service-learning project with the goal of providing ongoing assistance to the victims of Hurricane Katrina. On 6 different occasions from 2005 to 2008, Purdue nursing students integrated their leadership skills with application of public health knowledge, compassion, and concern as they worked in partnership with the Gulfport region Coastal Family Health Clinics (CFHC). This article reviews the service-learning framework, course planning, and implementation of a 3-year posthurricane disaster project.  相似文献   
70.
Ichthyoses are a common group of keratinization disorders. A non-inflammatory generalized persistent skin desquamation is observed. It is characterized by increased cell turnover, thickening of the stratum corneum and functional changes of sebaceous and sweat glands. All of these favor fungal proliferation. Dermatophytes may infect skin, hair and nails causing ringworm or tinea. They have the ability to obtain nutrients from keratinized material. One of its most prevalent genera is Trichophyton rubrum. Although tineas and ichthyoses are quite common, the association of the two entities is rarely reported in the literature. Three cases of ichthyosis associated with widespread infection by T. rubrum are presented. Resistance to several antifungal treatments was responsible for worsening of ichthyosis signs and symptoms.  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