Anaemia is a frequent problem after renal transplantation, whichmay appear as hypo-regenerative anaemia (due to myelotoxic drugsor infectious agents and/or poor graft function) or hyper-regenerativeanaemia (haemolysis or bleeding). It, therefore, seems reasonableto distinguish between different underlying causes of anaemiaaccording to reticulocyte counts. One of the presumably rather rare infectious agents causingtransient hypo-regenerative anaemia is the human parvovirusB19 (HPV B19) that was discovered in human blood 25 years ago[1] and was found to be the cause of ‘fifth disease’in children in the 1980s  相似文献   
8.
Anosognosia in mild cognitive impairment: Relationship to activation of cortical midline structures involved in self-appraisal.     
Michele L Ries  Britta M Jabbar  Taylor W Schmitz  Mehul A Trivedi  Carey E Gleason  Cynthia M Carlsson  Howard A Rowley  Sanjay Asthana  Sterling C Johnson 《Journal of the International Neuropsychological Society》2007,13(3):450-461
Awareness of cognitive dysfunction shown by individuals with Mild Cognitive Impairment (MCI), a condition conferring risk for Alzheimer's disease (AD), is variable. Anosognosia, or unawareness of loss of function, is beginning to be recognized as an important clinical symptom of MCI. However, little is known about the brain substrates underlying this symptom. We hypothesized that MCI participants' activation of cortical midline structures (CMS) during self-appraisal would covary with level of insight into cognitive difficulties (indexed by a discrepancy score between patient and informant ratings of cognitive decline in each MCI participant). To address this hypothesis, we first compared 16 MCI participants and 16 age-matched controls, examining brain regions showing conjoint or differential BOLD response during self-appraisal. Second, we used regression to investigate the relationship between awareness of deficit in MCI and BOLD activity during self-appraisal, controlling for extent of memory impairment. Between-group comparisons indicated that MCI participants show subtly attenuated CMS activity during self-appraisal. Regression analysis revealed a highly significant relationship between BOLD response during self-appraisal and self-awareness of deficit in MCI. This finding highlights the level of anosognosia in MCI as an important predictor of response to self-appraisal in cortical midline structures, brain regions vulnerable to changes in early AD.  相似文献   
9.
Muscarinic Receptors Activate Calcium Channels and Calcium Dependent Potassium Channels in NIE-115 Neuroblastoma Cells     
Britta Hedlund  Maud Lorentz  Peter Arhem 《Basic & clinical pharmacology & toxicology》1987,60(2):156-160
Abstract: Responses of NIE-115 neuroblastoma cells to application of carbachol were studied using intracellular recording techniques. Activation of muscarinic cholinergic receptors by carbachol resulted in a depolarization of the cells. The response was blocked by pirenzepine (1 μM) and by CoCl2 (5 mM), verapamil (10 μM) and gallopamil (10 μM), and prolonged by quinine (5 mM). It is suggested that muscarinic receptors increase the membrane calcium permeability, and that the influx of calcium activates calcium dependent potassium channels.  相似文献   
10.
Modifications of the hydrophilicity of heterocyclic methacrylate copolymers for protein release     
S. Downes  M. Patel  L. Di Silvio  H. Swai  K. Davy  M. Braden 《Biomaterials》1995,16(18):1417-1421
A series of copolymers comprising ethyl methacrylate (EM) and tetrahydrofurfuryl methacrylate (THFMA) gelled with either THFMA monomer or hydroxyethyl methacrylate (HEMA) monomer have been developed. In this paper, we examine the water uptake characteristics of the polymer systems and address the possibility of increasing the hydrophilicity of the systems by changing the ratios of the copolymers. We have investigated whether protein release from the polymers is related to the composition of the polymer systems. More protein was released from the polymers gelled with the more hydrophilic monomer (HEMA) than with THFMA. This was consistent with the calculated diffusion coefficients, which were 10 times greater for the polymers gelled with HEMA than those gelled with THFMA. Interestingly, the water uptake and protein release profiles were not dependent on the ratio of EM and THFMA in the copolymers. This is probably due to the conflicting roles of THFMA in the copolymer; it is both the more hydrophilic component as well as a cross-linking agent. In addition, it would appear that the structural and surface topography of these polymers had more significant effects on protein release than copolymer composition.  相似文献   
1 [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] 下一页 » 末  页»
  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   1991篇
  免费   168篇
  国内免费   8篇
耳鼻咽喉   10篇
儿科学   34篇
妇产科学   38篇
基础医学   392篇
口腔科学   48篇
临床医学   215篇
内科学   413篇
皮肤病学   34篇
神经病学   203篇
特种医学   50篇
外科学   188篇
综合类   13篇
一般理论   2篇
预防医学   186篇
眼科学   38篇
药学   117篇
中国医学   3篇
肿瘤学   183篇
  2024年   5篇
  2023年   21篇
  2022年   30篇
  2021年   46篇
  2020年   40篇
  2019年   61篇
  2018年   48篇
  2017年   51篇
  2016年   67篇
  2015年   73篇
  2014年   86篇
  2013年   117篇
  2012年   197篇
  2011年   159篇
  2010年   99篇
  2009年   111篇
  2008年   140篇
  2007年   120篇
  2006年   100篇
  2005年   105篇
  2004年   102篇
  2003年   102篇
  2002年   89篇
  2001年   16篇
  2000年   12篇
  1999年   19篇
  1998年   13篇
  1997年   7篇
  1996年   12篇
  1995年   14篇
  1994年   7篇
  1993年   8篇
  1992年   7篇
  1991年   9篇
  1990年   12篇
  1989年   3篇
  1988年   5篇
  1987年   3篇
  1986年   4篇
  1985年   6篇
  1984年   6篇
  1983年   7篇
  1982年   8篇
  1981年   5篇
  1980年   2篇
  1979年   2篇
  1978年   4篇
  1974年   3篇
  1970年   1篇
  1966年   2篇
排序方式: 共有2167条查询结果,搜索用时 15 毫秒
1.
Potential for widespread transmission of HIV/AIDS among American Indian (AI) adolescents exists, yet no evidence-based interventions (EBIs) have been adapted and evaluated with this population. Intensive psychoeducation may improve knowledge and decision-making which could potentially translate to reductions in HIV risk behaviors. A peer group randomized controlled comparison of an adapted EBI vs. control was delivered over an eight-day summer basketball camp in one reservation-based tribal community to adolescents ages 13–19. Outcome data were gathered immediately post-camp and at 6 and 12 months follow-up. Self-selected peer groups were randomized to intervention (n = 138) or control (n = 129) conditions for a total sample of 267 participants (56.2% female), mean age 15.1 years (SD = 1.7). Intervention participants had better condom use self-efficacy post-camp (Adjusted Mean Difference [AMD] = ?0.75, p < 0.005) and at 6 (AMD = ?0.44, p < 0.005) and 12 months (AMD = ?0.23, p < 0.05) follow-up. Intervention participants also had higher HIV prevention and transmission knowledge (post-camp: AMD = 0.07, p < 0.01; 6 months: AMD = 0.06, p < 0.01) were more likely to believe condoms prevent sexually transmitted infections (post-camp: RR = 1.41, p < 0.005; 6 months: RR = 1.34, p < 0.05), to talk with an adult about HIV/AIDS (post-camp: RR=1.78, p < 0.005; 6 months: RR = 1.14, p < 0.005), had higher partner negotiation efficacy related to substance use during sex (post-camp: AMD = 0.37, p < 0.01), and were more likely to intend to use a condom (post-camp: RR = 1.39, p < 0.01). The adapted intervention had short- and medium-term impacts on AI adolescent risk for HIV/AIDS, but attenuated at 12 months. Intervention delivery through a community-based camp is feasible and acceptable with strong retention. Additional study is needed to evaluate the adapted intervention's impact on sexual risk behaviors and if booster sessions and parent involvement translate to long-term impacts.  相似文献   
2.
3.
4.
Growth of malignant tumors is dependent on sufficient blood supply. Thus, inhibition of tumor angiogenesis is emerging as a promising target in the treatment of malignancies. Human angiostatin (hANG) is one of the most potent inhibitors of endothelial cell proliferation, angiogenesis, and tumor growth in vivo. However, its mechanisms operating in vivo are not well understood. METHODS: To obtain more information about functional changes in the angiogenic process, we established Morris hepatoma (MH3924A) cell lines expressing hANG (hANG-MH3924A). The effects of hANG expression on proliferation and apoptosis of human umbilical vein endothelial cells (HUVECs) were measured in coculture experiments in vitro. To evaluate changes in tumor perfusion and blood volume, H2 15O and 68Ga-DOTA-albumin (DOTA is 1,4,7,10-tetraazacyclododecane-N,N',N',N'-tetraacetic acid) were used for PET studies in vivo. Additionally, immunohistologic quantification of vascularization, apoptosis, and proliferation as well as gene array analyses were performed. RESULTS: Our in vitro experiments demonstrate reduced proliferation and increased apoptosis in HUVECs when being cocultured with hANG-MH3924A. In support, tumor growth of hANG-MH3924A is diminished by 95% in vivo. However, tumor perfusion and blood volume are increased in hANG-MH3924A corresponding to an increased microvessel density. Furthermore, hANG-transfected tumors show changes in expression of genes related to apoptosis, stress, signal transduction, and metabolism. CONCLUSION: hANG expression leads to inhibition of tumor growth, increased apoptosis, and changes in the expression of multiple genes involved in stress reactions, signal transduction, and apoptosis, which indicates a multifactorial reaction of tumors. An enhanced microvessel density is seen as part of these reactions and is associated with increased perfusion as measured by PET.  相似文献   
5.
Many behavioral, immunological, and physiological consequences of brief maternal separation in bonnet (Macaca radiata) and pigtail monkeys (Macaca nemistrina) have been documented. However, the impact of social separation on plasma cortisol and growth hormone is unknown for these particular species. In the present study, the behavioral and endocrinological consequences of a 2-week maternal separation in socially housed infant bonnet and pigtail monkeys were followed. In seven pairs (separated and matched control) of bonnet and six pairs of pigtail infants, plasma was obtained under baseline, separated, and reunion conditions twice weekly for the duration of the study. Blood samples were obtained from both infants of the pair in approximately 10 min. Plasma total cortisol, free cortisol, and growth hormone were measured in these samples. Focal animal behavioral observations were made on all subjects twice daily throughout the study period. In both species, total cortisol and free cortisol rose immediately following maternal separation in comparison to the matched nonseparated controls and returned to basal levels (e.g., that of matched non-separted controls) following reunion with the mother. In contrast, plasma growth hormone rose only in the pigtail infants over a time course that peaked around the time of reunion. Multiple regression techniques indicated for the first week of separation, in the separated but not control subjects, that mean plasma free and total cortisol was positively related to distress behaviors (vocalization and postural slouch) observed during this week and negatively related to social behaviors (play and proximity to others) noted during the same period. In contrast, plasma growth hormone was related to both species and sex of the subjects but unrelated to behavioral variables. © 1995 John Wiley & Sons, Inc.  相似文献   
6.
7.
   Introduction
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