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   491708篇
  免费   34820篇
  国内免费   11609篇
耳鼻咽喉   6122篇
儿科学   9257篇
妇产科学   11189篇
基础医学   66208篇
口腔科学   13595篇
临床医学   45419篇
内科学   94956篇
皮肤病学   9658篇
神经病学   33167篇
特种医学   18039篇
外国民族医学   159篇
外科学   72013篇
综合类   30171篇
现状与发展   41篇
一般理论   69篇
预防医学   25141篇
眼科学   12703篇
药学   42781篇
  95篇
中国医学   9175篇
肿瘤学   38179篇
  2023年   2634篇
  2022年   6148篇
  2021年   8898篇
  2020年   6331篇
  2019年   6656篇
  2018年   8551篇
  2017年   7040篇
  2016年   6952篇
  2015年   9311篇
  2014年   12179篇
  2013年   13049篇
  2012年   18302篇
  2011年   19370篇
  2010年   11985篇
  2009年   10373篇
  2008年   15300篇
  2007年   16018篇
  2006年   15830篇
  2005年   14989篇
  2004年   12476篇
  2003年   11921篇
  2002年   11105篇
  2001年   30582篇
  2000年   31255篇
  1999年   26396篇
  1998年   7038篇
  1997年   6202篇
  1996年   5338篇
  1995年   4926篇
  1994年   4345篇
  1993年   3612篇
  1992年   16911篇
  1991年   15474篇
  1990年   14734篇
  1989年   14466篇
  1988年   13021篇
  1987年   12416篇
  1986年   11395篇
  1985年   10542篇
  1984年   7004篇
  1983年   5663篇
  1982年   2764篇
  1979年   5522篇
  1978年   3347篇
  1977年   2971篇
  1975年   2641篇
  1974年   3065篇
  1973年   2865篇
  1972年   2828篇
  1971年   2773篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
92.
目的探讨儿童过敏性紫癜的影像学特点及其临床价值。方法回顾性分析32例过敏性紫癜并发肠套叠患儿的临床及影像学资料。结果出现并发症之前过敏性紫癜的腹部X线主要表现为局限性小肠充气扩张,粘膜增粗,肠间隙增宽,可伴有液平;B超显示为不同程度的多发节段性肠壁水肿增厚,肠管狭窄等表现;出现并发症后,其X线表现加重,部分病例伴有肠穿孔;B超及X线监视下空气灌肠可以明确是否并发肠套叠,部分病例可通过空气灌肠达到复位治疗的目的。结论影像学检查的重要临床价值在于能与需要手术治疗的其他急腹症相鉴别,同时可以了解其是否并发常见的并发症,为临床确定治疗方案提供可靠的信息。  相似文献   
93.
经尿道前列腺电切气化术治疗前列腺增生568例报告   总被引:13,自引:0,他引:13  
目的 :进一步探讨前列腺增生 (BPH)的有效手术新方法。方法 :采用经尿道前列腺电切术和气化术治疗BPH患者 5 6 8例。结果 :疗效满意 ,术后 3~ 6个月随访 ,国际前列腺症状评分 (IPSS) 8.5± 1.5分 ;最大尿流率 (Q max) 2 0 .5± 4 .5ml s,剩余尿量 2 9.1± 14 .2ml,未出现严重并发症。结论 :将电切和气化相结合行经尿道前列腺切除术是一种安全性高、并发症少、疗效确切的新手术方法 ,具有操作易掌握、出血少、速度快、安全可靠等优点。  相似文献   
94.
目的:探讨准分子激光角膜切削术(PRK)后转化生长因子β1(TGF-β1)在角膜伤口愈合和解膜雾状混浊发病机制中的作用。方法:将24只新西兰大白兔(24只眼)随机分为正常组(n=4)和手术组(n=20)。手术组每只左眼行PRK术,术中采用准分子激光器,角膜中央激光去上皮,然后按-10.00D近视进行切削,分别于术后第7d,14d,28d和3月于裂隙灯下观察记录角膜haze的变化并处死动物,将角膜组织制成石蜡切片,应用原位杂交技术检测角膜缲TGF-β1mRNA的表达。结果:①从术后第7d开始,术眼均不同程度地发生了角膜haze,严重者可达3级,haze高峰约在术后第28d。②正常角膜上皮中TGF-β1mRNA有低水平表达,PRK术后第7d,14d和28d,角膜上皮TGF-β1mRNA表达明显增高。术后3月已开始降低;正常组角膜基质中未检测出TGF-β1mRNA,术后第7d,14,和28d,角膜基质中TGF-β1mRNA表达明显增高,术后3月已开始降低。结论:TGF-β1可能参与了PRK术后的伤口愈合,它可能通过促进角膜基质细胞的增殖和细胞外基质的合成而促进角膜haze的发生。  相似文献   
95.
蛇床子水提取液抑瘤作用的实验研究   总被引:13,自引:0,他引:13  
目的 :研究蛇床子水提取液的体内抗肿瘤作用。方法 :通过 S180 肉瘤移植建立荷瘤小鼠模型 ,给予不同剂量蛇床子水提取液后观察 S180 荷瘤小鼠肿瘤生长曲线、血清唾液酸 (SA)、瘤重及小鼠生存天数的变化。结果 :蛇床子水提取液能明显抑制肿瘤生长 ,降低荷瘤小鼠血清 SA水平 ,0 .0 6mg/(g· d) ,0 .1 1 mg/(g· d)、0 .2 1 mg/(g· d)剂量组平均瘤重低于肿瘤对照组 (P<0 .0 5 ) ,抑瘤率依次为 2 3 .2 %、2 9.1 %和 2 4 .8%,且能延长荷瘤小鼠生存天数 (P<0 .0 1 ) ,动物生命延长率依次为 :2 6 .9%、3 4 .8%和 2 6 .6 %。结论 :蛇床子水提取液具有较强的抗肿瘤效应 ,有很好的利用前景 ,值得对其进行深入研究。  相似文献   
96.
BACKGROUND: Gastric cancer (GC) is the leading cause of cancer deaths in China. Our study prospectively evaluated the impact of repeated endoscopic screens on GC mortality in a high-risk population in China. METHODS: Between 1989 and 1999, a population-based gastroscopic screening was conducted in 4,394 residents of Linqu County, China, a region with the highest rates of GC worldwide. Residents ages 35 to 64 years received initial gastroscopies with biopsies in 1989. Repeated endoscopies were performed in 1994 and 1999. Cancer occurrences and deaths were actively monitored throughout the entire period until July 2000. Mortality from GC was compared with expected values based on mortality rates obtained for Linqu in the 1990-1992 Chinese Cancer Mortality Survey. RESULTS: Between March 1989 and July 2000, 39,303 person-years were accumulated; 85 new GCs occurred, 29 (34.5%) were in early stage. Fifty-eight cases (68%) were identified at one of the screens. The number of observed deaths from GC (37) was close to the expected (36.8). The standardized mortality ratio was 1.01 (95% CI 0.72-1.37) for the entire cohort, 1.13 (95% CI 0.77-1.57) for males, and 0.65 (95% CI 0.26-1.32) for females. CONCLUSIONS: Despite high population coverage with repeated screens, no reduction in GC mortality was observed in this high-risk population in China.  相似文献   
97.
A nationwide survey of transient hyperammonemia in newborns was carried out in Japan. A total of 18 patients, consisting of 12 male and 6 female infants, were reported from 11 facilities. These neonates exhibited hyperammonemia with plasma ammonia levels in the range from 124 to 6256 micrograms/dl. Four newborn infants of the 18 died in the neonatal period, and an additional one died in the early infancy. Among the 13 infants who were alive at the time of this survey, 6 had neurological sequelae, including mental retardation, spastic quadriplegia and epilepsy. The multivariate analysis revealed that the Apgar score at 1 minute, peak plasma ammonia concentration, birth weight and sex were significant factors affecting the prognosis of life.  相似文献   
98.
One of the consequences of increased intracellular calcium in response to a variety of physiological stimuli is the calcium activation of cytosolic proteases. Unlike lysosomal proteases with broad specificity, these calcium-activated neutral proteases show limited proteolysis of a restricted set of substrate proteins suggesting they may play a regulatory role in cellular physiology. In this study we show that the neural cell adhesion molecules NCAM-180 and N-cadherin are substrates for such endogenous calcium-activated neutral proteases. In contrast, a third neural cell adhesion molecule G4/L1 was not susceptible to calcium-activated proteolysis. The threshold for activation of NCAM and N-cadherin proteolysis is in the micromolar range of calcium suggesting that NCAM and N-cadherin are substrates for a mu-type calpain (calpain I). The site recognized by this protease is within intracellular domains of NCAM-180 and N-cadherin which are important for their interaction with cytoskeletal components. These results suggest that calcium-activated proteolysis at these sites in vivo could disrupt the linkage between extracellular ligand binding to these adhesion molecules and the normal intracellular effectors of such extracellular binding events.  相似文献   
99.
We report an 80-year-old Japanese male with four primary malignant tumors: malignant melanoma, prostatic cancer, malignant lymphoma, and renal cell carcinoma, which occurred in that respective order. The combination of malignant melanoma and malignant lymphoma is rare. The patient was treated with BCG after an operation for malignant melanoma. He was also treated with cobalt 60 irradiation after an operation for prostatic cancer. We also discuss other reports of multiple malignant tumors and suggest some possible causes of this patient's primary malignant tumors.  相似文献   
100.
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