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   1164篇
  免费   66篇
  国内免费   37篇
耳鼻咽喉   20篇
儿科学   55篇
妇产科学   10篇
基础医学   112篇
口腔科学   32篇
临床医学   130篇
内科学   240篇
皮肤病学   12篇
神经病学   63篇
特种医学   172篇
外科学   157篇
综合类   18篇
预防医学   44篇
眼科学   30篇
药学   62篇
中国医学   2篇
肿瘤学   108篇
  2023年   7篇
  2022年   12篇
  2021年   20篇
  2020年   13篇
  2019年   13篇
  2018年   22篇
  2017年   13篇
  2016年   10篇
  2015年   21篇
  2014年   39篇
  2013年   47篇
  2012年   45篇
  2011年   70篇
  2010年   72篇
  2009年   57篇
  2008年   49篇
  2007年   47篇
  2006年   31篇
  2005年   32篇
  2004年   16篇
  2003年   21篇
  2002年   20篇
  2001年   23篇
  2000年   13篇
  1999年   16篇
  1998年   52篇
  1997年   49篇
  1996年   48篇
  1995年   44篇
  1994年   45篇
  1993年   27篇
  1992年   10篇
  1991年   16篇
  1990年   14篇
  1989年   28篇
  1988年   31篇
  1987年   19篇
  1986年   24篇
  1985年   14篇
  1984年   9篇
  1983年   11篇
  1982年   13篇
  1981年   9篇
  1980年   12篇
  1979年   8篇
  1978年   7篇
  1977年   11篇
  1976年   11篇
  1975年   7篇
  1969年   4篇
排序方式: 共有1267条查询结果,搜索用时 15 毫秒
71.
Squamous cell carcinoma of the head and neck region (HNSCC) is the sixth most frequent cancer worldwide. In the USA, 30,000 new cases and 8,000 deaths are reported each year. Differences between normal epithelium and cancer cells from the upper aerodigestive tract arise from alterations in expression of specific genes controlling proliferation and immortalization. The protein products of these genes include growth factor receptors, cell cycle regulators, and tumor suppressors which affect a variety of intracellular signaling pathways. To determine how altered expression of these gene products contribute to HNSCC progression, we examined expression of epidermal growth factor receptor (EGFR), cyclins, p16INK4A, c-myc, proliferating cell nuclear antigen (PCNA), and telomerase in archival pathology specimens by immunohistochemistry. A substantial majority of HNSCC tumors showed loss of p16INK4A expression and dramatic overexpression of EGFR. Overexpression of this receptor correlated with increased cyclin A levels and high mitotic index. EGFR, cyclins A, -B1, -E, and c-myc overexpression was significantly increased in stage III and IV tumors compared to early stage cancers. hTERT was expressed in all tumors and primarily in the basal layer cells of dysplastic epithelial lesions. Suprabasal expression of hTERT was found in a significantly higher number of HNSCC cases than in dysplastic lesions. These results indicate that overexpression of cell cycle regulatory proteins correlates with advanced tumor stage in HNSCC.  相似文献   
72.
Emergency physicians constantly have multiple ethical obligations in the emergency department. They must understand these sometimes conflicting obligations and learn to prioritize. A case discussion is presented that exemplifies the conflict between patient privacy and society's right to know. Specific aspects of HIV testing and obtaining patient consent are presented. Teaching physicians are encouraged to use such common cases for "ethics case discussion."  相似文献   
73.
Cardiovascular disease accounts for nearly 40% of all deaths annually in this country. Prevention management and advances in medical treatments have dramatically reduced the overall mortality rate due to heart disease. However, death due to chronic heart failure (HF) continues to rise, and effective therapy, particularly for end-stage HF, has been elusive. The myocardial beta-adrenergic receptor (betaAR) system is critical not only in chronic HF but also in acute settings where cardiac function is compromised. Adding to its importance is the fact that drugs that act by altering betaAR signal transduction are at the forefront of conventional HF therapeutic strategies. Accordingly, the ability to genetically manipulate betaAR signaling in the heart is of great interest since it may provide unique inotropic support and improve existing therapeutic strategies for HF.  相似文献   
74.
75.
76.
PURPOSE: To report ocular and renal findings specific to the inheritable entity called papillorenal (also known as renal-coloboma) syndrome and relate these to a common cause. DESIGN: Observational case series and genetic study. PARTICIPANTS: Two unrelated probands presenting with absent central retinal vessels and 11 available family members. TESTING: Doppler ultrasonographic imaging of the optic nerves and kidneys, fluorescein angiography, and genetic testing for PAX2 mutations were performed. In selected cases, indocyanine green angiography, scanning laser ophthalmoscope perimetry, Retinal Thickness Analyzer measurements, visual evoked potentials, and magnetic resonance imaging were also performed. MAIN OUTCOME MEASURES: Better defined characteristics of the papillorenal syndrome. RESULTS: Numerous cilioretinal vessels were present with rudimentary or absent central retinal vessels. Superonasal visual field defects, typical for papillorenal syndrome, corresponded to inferotemporal areas of anomalous retinal and choroidal perfusion and hypoplastic retina. Renal hypoplasia was discovered in two affected members of one family (with previously unsuspected renal failure in one case), and recurrent pyelonephritis was discovered in four affected members of the other family. No PAX2 mutations were detected. CONCLUSIONS: In the papillorenal syndrome, the hereditary absence of central retinal vessels may be missed, leading to confusion with isolated coloboma, low-tension glaucoma, and morning glory anomaly. Greater awareness of this syndrome will avoid unneeded glaucoma therapy, allow earlier recognition of renal diseases, and allow genetic counseling. We propose that the papillorenal syndrome is a primary dysgenesis that causes vascular abnormalities predominantly affecting the eye, kidney, and urinary tract, leading to hypoplasia of these structures. The absence of defects in the PAX2 gene in these families suggests that mutations in other genes may also be responsible for this syndrome.  相似文献   
77.
78.
The "at birth" system which is used in Sheffield to identify children likely to die unexpectedly in infancy, was tested retrospectively in Birmingham (83 cases) and in Newcastle upon Tyne (56 cases). The discrimination between cases and age-matched controls was poor in both cities. Analysis of the 8 factors used in the system showed that only 2 maintained significant case/control differences in Birmingham and Newcastle. Further investigation showed that other factors from maternity records showed significant case/control differences in these cities. Although the system used in Sheffield would not be of use in a prospective prevention programme in either Newcastle or Birmingham, the possibility of evolving an "at risk" system which might apply more widely is discussed.  相似文献   
79.
三尖杉树皮粗提取物中的一个新生物碱—高三尖杉酯碱酰胺(homoharringtonamide)的结构,经质谱—质谱分析,初步建议为16。类似的酰胺类生物碱,例如三尖杉碱酰胺(cephalotaxamide,6)、11-羟基三尖杉碱酰胺(11-hydroxycephalotaxamide,9)、三尖杉酯碱酰胺(harfingtonamide,14)或异三尖杉酯碱酰胺(isoharringtonamide,15)也可能存在,后三者(9,14,15)尚未见报道。  相似文献   
80.
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