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   577篇
  免费   37篇
  国内免费   22篇
耳鼻咽喉   1篇
儿科学   37篇
妇产科学   3篇
基础医学   32篇
口腔科学   26篇
临床医学   47篇
内科学   71篇
皮肤病学   10篇
神经病学   23篇
特种医学   122篇
外科学   58篇
综合类   31篇
预防医学   36篇
眼科学   31篇
药学   75篇
肿瘤学   33篇
  2023年   5篇
  2021年   3篇
  2020年   6篇
  2019年   11篇
  2018年   12篇
  2017年   2篇
  2016年   5篇
  2015年   9篇
  2014年   9篇
  2013年   13篇
  2012年   10篇
  2011年   14篇
  2010年   11篇
  2009年   14篇
  2008年   21篇
  2007年   37篇
  2006年   38篇
  2005年   14篇
  2004年   13篇
  2003年   5篇
  2002年   11篇
  2001年   21篇
  2000年   15篇
  1999年   18篇
  1998年   36篇
  1997年   21篇
  1996年   27篇
  1995年   28篇
  1994年   21篇
  1993年   26篇
  1992年   12篇
  1991年   9篇
  1990年   15篇
  1989年   6篇
  1988年   11篇
  1987年   9篇
  1986年   20篇
  1985年   14篇
  1984年   10篇
  1983年   7篇
  1982年   8篇
  1981年   7篇
  1980年   15篇
  1979年   3篇
  1978年   4篇
  1977年   4篇
  1976年   4篇
  1975年   1篇
  1955年   1篇
排序方式: 共有636条查询结果,搜索用时 15 毫秒
51.
Pulmonary histiocytosis X: comparison of radiographic and CT findings   总被引:6,自引:0,他引:6  
The authors retrospectively evaluated radiographs, computed tomographic (CT) scans, and results of pulmonary function tests (when available) for 17 patients with biopsy-proved pulmonary histiocytosis X. In 11 patients, high-resolution CT was used. In 12 patients, CT demonstrated cystic air spaces, usually less than 10 mm in diameter. In three of these 12, cysts were the only abnormality, but in six others, nodules (usually less than 5 mm in diameter) were also present. Two patients had only nodules and one, only emphysema. CT showed that many lesions that appeared reticular on plain radiographs were actually cysts. CT showed no central or peripheral concentration of lesions, but it did reveal that many small nodules were distributed in the centers of secondary lobules around small airways. CT findings correlated better with the diffusing capacity (rho = -0.71) than did the plain radiographic findings (rho = -0.57). Thus, CT was better than radiography at showing the morphology and distribution of lung abnormalities.  相似文献   
52.
不同孔径纳米羟基磷灰石人工骨修复兔桡骨缺损效果比较   总被引:4,自引:7,他引:4  
目的:纳米级的羟基磷灰石材料与人体内组织成分更为相似,具有更佳的生物性能。评价不同孔径的多孔纳米羟基磷灰石人工骨的骨缺损修复能力,从而筛选出适合的孔径以达到骨传导功能与生物力学性能的良好统一。方法:实验于2005-10/2006-10在深圳市第二人民医院中心实验室完成。①实验材料:纳米羟基磷灰石人工骨以硝酸钙和磷酸二氢铵为原料,采用溶胶-絮凝法制备粉体,运用压力成型、木模成型和浸渍成型分别制得孔隙分布均匀的孔径分别为50~150μm、100~250μm和300~500μm的多孔纳米羟基磷灰石人工骨。②实验动物:雄性新西兰大白兔60只随机分为植入50~150μm孔径材料组、植入100~250μm孔径材料组、植入300~500μm孔径材料组、空白对照组,每组15只。实验过程中对动物处置符合动物伦理学要求。③实验方法:制备双侧桡骨骨缺损动物模型,然后用3种不同孔径的纳米羟基磷灰石人工骨材料植入骨缺损处进行修复,空白对照组不植入任何材料。④实验评估:术后4,8和12周分别行大体标本观察、X射线片观察、扫描电镜观察及生物力学测试,比较各组材料修复骨缺损的能力。结果:实验动物均进入结果分析。①X射线片检查结果:术后4周、8周、12周,植入100~250μm孔径材料组X射线评分高于植入50~150μm,300~500μm孔径材料组,差异有显著性意义(P<0.05)。②生物力学检测结果:术后4周、8周、12周,植入100~250μm孔径材料组生物力学强度高于植入50~150μm,300~500μm孔径材料组,差异有显著性意义(P<0.05)。③扫描电镜观察结果:植入100~250μm孔径材料组成骨效果明显优于植入50~150μm,300~500μm孔径材料组和空白对照组。结论:纳米羟基磷灰石人工骨具有良好的成骨能力,但其骨修复能力受孔径因素的影响,孔径100~250μm的纳米羟基磷灰石人工骨材料成骨能力较好。  相似文献   
53.
Inflammatory bowel disease and the X chromosome   总被引:1,自引:0,他引:1  
A review of documented cases demonstrates a significant association of Turner's syndrome with Crohn's disease and ulcerative colitis; this association relates particularly to genetic constitutions comprising an abnormal rather than an absent X chromosome. The karyotype 46XiXq, in pure or mosaic form, appears to be a significant susceptibility factor for inflammatory bowel disease. This karyotype often gives rise to relatively weak phenotypic characteristics of Turner's syndrome, which may be overlooked in short females with inflammatory bowel disease. The association of inflammatory bowel disease with Turner's syndrome may reflect the presence on the X chromosome of genes involved in disease pathogenesis. Linkage analysis studies, involving microsatellite markers on the X chromosome, are being performed.   相似文献   
54.
Donor sepsis is not a contraindication to cadaveric organ donation   总被引:1,自引:0,他引:1  
Systemic donor infection is regarded as being an absolute contraindication to cadaveric organ donation for transplantation. This is largely due to fear of transmitting pathogenic organisms to the immunosuppressed recipient. However, due to the current shortage of organs available for transplantation, clinicians are faced with the option of using organs from 'non-ideal' donors, such as those patients with documented evidence of infection. We report the successful outcome of six orthotopic liver transplants, 11 renal transplants, one combined heart lung transplant and one simultaneous kidney and pancreas transplant with organs from eight donors in whom bacterial meningitis (n = 7) and acute bacterial epiglottitis (n = 1) were the antecedent causes of death.   相似文献   
55.
56.
57.
The present study examines the impact of including lessons on aging in a 12th grade social studies course on student perceptions of aging and older adults, working with older persons, and knowledge of "facts" on aging. Pre/post-test data were collected from approximately 650 upstate New York 12th grade students enrolled in a government class that included from five to ten lessons on aging issues. Over two-thirds of the semantic differential and four of five job-related questions showed a significant change to more positive views of aging. Changes on the "fact" questions were mixed but students uniformly reported that the interview with an older adult assignment changed their view of the older person with whom they talked and was the most popular activity in the unit. These findings suggest that including information on aging in a high school social studies course can lead to more positive student perceptions of aging and general attitudes toward working with older adults.  相似文献   
58.
59.
The in vivo occupancy of brain benzodiazepine binding sites by compounds A and B was measured using a [(3)H]Ro 15-1788 binding assay and related to plasma and brain drug concentrations. The plasma concentration associated with 50% occupancy was higher for compound A than compound B (73 and 3.7 nM, respectively), however, there was little difference in the brain concentrations required (73 and 63 nM). Both compounds showed a non-linear relationship between plasma and brain concentrations such that above brain concentrations of approximately 100 nM increasing plasma concentrations did not result in a concomitant increase in brain concentrations. This is consistent with brain concentrations being dependent on a saturable compartment which was postulated to be the benzodiazepine binding site-containing GABA(A) receptors. This hypothesis was tested in alpha1H101R mice, in which the alpha1 subunit of the GABA(A) receptor is rendered insensitive to benzodiazepine binding resulting in an approximate 50% reduction in the total benzodiazepine-containing GABA(A) receptor population. It was shown that the Occ(50) brain concentrations in the alpha1H101R animals was lower (17 nM) than in wild type mice (63 nM), as was the plateau concentration in the brain (105 and 195 nM, respectively). These data suggest measured concentrations of compounds A and B in brain tissue are dependent on receptor expression with a minimal contribution from unbound and non-specifically bound compound.  相似文献   
60.
Trenbolone acetate is a synthetic androgen that is currently used as a growth promoter in many meat-exporting countries. Despite industry laboratories classifying trenbolone as nonteratogenic, data showed that embryonic exposure to this androgenic chemical altered development of the immune system in Japanese quail. Trenbolone is lipophilic, persistent, and released into the environment in manure used as soil fertilizer. This is the first study to date to assess this chemical's immunotoxic effects in an avian species. A one-time injection of trenbolone into yolks was administered to mimic maternal deposition, and subsequent effects on the development and function of the immune system were determined in chicks and adults. Development of the bursa of Fabricius, an organ responsible for development of the humoral arm of the immune system, was disrupted, as indicated by lower masse, and smaller and fewer follicles at day 1 of hatch. Morphological differences in the bursas persisted in adults, although no differences in either two measures of immune function were observed. Total numbers of circulating leukocytes were reduced and heterophil-lymphocyte ratios were elevated in chicks but not adults. This study shows that trenbolone acetate is teratogenic and immunotoxic in Japanese quail, and provides evidence that the quail immune system may be fairly resilient to embryonic endocrine-disrupting chemical-induced alterations following no further exposure posthatch.  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