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   11048篇
  免费   772篇
  国内免费   465篇
耳鼻咽喉   75篇
儿科学   122篇
妇产科学   239篇
基础医学   2160篇
口腔科学   621篇
临床医学   802篇
内科学   1754篇
皮肤病学   206篇
神经病学   810篇
特种医学   191篇
外国民族医学   2篇
外科学   986篇
综合类   1707篇
现状与发展   2篇
预防医学   316篇
眼科学   205篇
药学   959篇
  2篇
中国医学   419篇
肿瘤学   707篇
  2024年   7篇
  2023年   86篇
  2022年   141篇
  2021年   289篇
  2020年   199篇
  2019年   190篇
  2018年   168篇
  2017年   210篇
  2016年   221篇
  2015年   303篇
  2014年   516篇
  2013年   656篇
  2012年   534篇
  2011年   662篇
  2010年   549篇
  2009年   597篇
  2008年   645篇
  2007年   692篇
  2006年   664篇
  2005年   633篇
  2004年   576篇
  2003年   542篇
  2002年   493篇
  2001年   398篇
  2000年   351篇
  1999年   346篇
  1998年   293篇
  1997年   241篇
  1996年   258篇
  1995年   182篇
  1994年   129篇
  1993年   120篇
  1992年   95篇
  1991年   77篇
  1990年   41篇
  1989年   37篇
  1988年   26篇
  1987年   15篇
  1986年   12篇
  1985年   23篇
  1984年   18篇
  1983年   11篇
  1982年   6篇
  1981年   11篇
  1980年   7篇
  1979年   7篇
  1977年   4篇
  1976年   1篇
  1974年   1篇
  1973年   1篇
排序方式: 共有10000条查询结果,搜索用时 20 毫秒
31.
Expression of β-catenin was investigated in normal breast tissue and 66 breast carcinomas in conjunction with expression of epithelial cadherin (E-CD) and α-catenin. In normal mammary ducts and acini, intense β-catenin immunoreactivity was present at the basolateral surfaces of luminal epithelium and weak immunoreactivity was observed at the lateral borders of myoepithelial cells. No β-catenin was revealed at the myoepithelial basal surface. The intercellular expression of β-catenin, as well as of E-CD and α-catenin, was also observed in carcinoma tissues with varying staining intensity. Almost all of 10 intraductal carcinomas and approximately 70% of 41 invasive ductal carcinomas expressed the three molecules at the same level as in normal glands, whereas approximately 80% of 13 invasive lobular carcinomas showed severe deficiency of them. Two lobular carcinomas in situ showed complete absence of all of the proteins. Some of these findings were confirmed biochemically by immunoblotting analysis. In invasive ductal carcinomas, α-catenin was reduced more frequently in diffuse than in solid type tumours, whereas the level of expression of β-catenin and E-CD was unchanged between them. No correlation was present between reduced expression of the adhesion molecules and lymph node metastasis.  相似文献   
32.
Is it possible to prevent bacterial adhesion onto ureteric stents?   总被引:1,自引:0,他引:1  
The aim of this study was to determine whether the use of bactericidal coatings or immersion in antibiotic solution reduces or prevents bacterial adhesion onto ureteric stents. Precut segments of full silicone, silver-coated and hydrogel-coated ureteric stents were incubated with two uropathogenic bacterial strains with and without previous immersion in antibiotic solution. Tobramycin, ceftriaxone and ciprofloxacin solutions were used, as these antibiotics are commonly administered for the prophylaxis and treatment of urinary tract infection (UTI). Microbiological analysis showed that immersion of ureteric stents in ceftriaxone and ciprofloxacin yielded a significant reduction of bacterial adhesion, whereas immersion in tobramycin did not. The surface material of the stents had no direct influence on bacterial adhesion. In this experimental study, neither the silver nor the hydrogel coat reduced bacterial adhesion onto ureteric stents whereas immersion in a suitable antibiotic solution significantly reduced and even prevented this phenomenon, probably due to the adhesion of the antibiotic onto the stent surface. Prevention of bacterial adhesion onto ureteric stents is essential to reduce the risk of UTI in connection with these devices.  相似文献   
33.
In this study, human umbilical vein and human saphenous vein endothelial cells were seeded on glass and exposed to fluid shear in a parallel-plate flow chamber. Cell retention, morphology and migration were studied as a function of shear stress and of adhesion time prior to exposure to shear. Three-hour and 24-h adhesion times gave rise to comparable cell retention values after 2 h of flow for both cell types. Cell retention decreased from 85 to 20% as shear stress increased from 88 to 264 dynes cm−2 (8.8 to 26 Pa). Mean spreading areas decreased after the onset of flow, but subsequently stabilized to plateau values, which were smaller at higher shear stresses. Shape factors increased faster to higher values as cells were exposed to higher shear stresses, without any obvious preference in orientation of the cells with respect to the direction of flow. Migration was unidirectional with flow and linear with time. Migration was faster for cells which had adhered for 24 h than for cells which had adhered for 3 h and was accompanied by the presence of fibrillar structures left behind on the surface upstream of migrating cells. It is concluded that after 3 h adhesion to glass, cells have adhered with an adhesion strength that does not substantially increase during the next 21 h. However, during this time changes in cell-substratum interactions seem to occur judging by the differences in, e.g., migration rates.  相似文献   
34.
35.
Background We previously found that glomerular epithelial cells play an important role in the formation of adhesive lesions. Glomerular sclerotic lesions develop after the inital adhesive lesions. Methods Two series of experiments were done with spontaneously diabetic WBN/Kob rats. These rats develop segmental glomerular sclerotic lesions with aging. The first series of experiments was intended to clarify the kinetics of glomerular cells on progressive glomerular damage in these rats. The second series of experiments was designed to study the relationship between proliferation (judged by % bromodeoxyuridine-positive cells) of glomerlar epithelial cells and sclerotic lesions with adhesions. Results In the first series, rats having increased proteinuria showed segmental glomerular sclerotic lesions with adhesions. At the same time, increased labeling indices of tuft cells and epithelial cells of Bowman's capsule were observed. In the second series, no significant increase in the labeling indices of tuft cells with sclerotic lesions was observed, compared to tuft cells without sclerotic lesions. In sclerotic lesions with adhesion, bromodeoxyurdine-positive cells were observed that were not distinguishable as podocytes or epithelial cells of Bowman's capsule. The highest labelling index was noted in the epithelial cells of Bowman's capsules with sclerosis. Conclusion This study shows that the proliferation of glomerular epithelial cells (mainly epithelial cells of Bowman's capsule) occurs in glomerular sclerotic lesions with adhesions.  相似文献   
36.
Objective To investigate the prevention of intestines adhesion about sodium hyaluronic acid in postoperative intestines adhesion.Methods Eighteen cases of adhesive intestine obstruction were done intestinal release or bowel resection.2~4mL sodium hyaluronic acid was put to the wound,anastigmatic and rough surface of peritoneal.Gastrointestinal decompression,anti-infective and infusion were taken after oper-ations.Followed up 8~24 months.Results Obstructive symptoms haven't happened,the effective rate is 100%.Only 2 cases have intermittent abdominal pain without obstruction,the incidence was 11%.Conclu-sion Sodium hylauronic acid is effective to prevent the adhesion of postoperative intestines adhesion,simp-ler use,fewer side-effects and great value to appliance.  相似文献   
37.
AIMS: Type 2 diabetes mellitus (DM) and coronary artery disease (CAD) are both associated with endothelial dysfunction and elevated oxidative and inflammatory state. We examined the effect of vitamin C on endothelial function and levels of soluble vascular cell adhesion molecule (sVCAM-1), interleukin-6 (IL-6) and tumour necrosis factor (TNF-alpha), in DM patients with or without CAD and in non-diabetic subjects. METHODS: Thirty-seven patients with DM + CAD, 17 patients with DM without CAD and 21 non-diabetic subjects were divided into groups receiving vitamin C 2 g/day or no anti-oxidant for 4 weeks. Forearm blood flow was determined using venous occlusion gauge-strain plethysmography. Forearm vasodilatory response to reactive hyperemia was considered as index of endothelium-dependent dilation. RESULTS: Baseline levels of IL-6 and TNF-alpha were significantly higher in patients with DM + CAD compared with patients with DM (P < 0.01) or non-diabetic subjects (P < 0.01). IL-6 and TNF-alpha levels were also higher in DM compared with non-diabetic subjects (P < 0.05). sVCAM-1 levels were lower in non-diabetic controls compared with DM + CAD (P < 0.05) or DM (P < 0.05). Reactive hyperaemia was higher in non-diabetic controls compared with DM + CAD (P < 0.001) or DM (P < 0.001). Vitamin C significantly increased reactive hyperaemia only in the DM + CAD group, while it had no effect on serum levels of sVCAM-1, TNF-alpha and IL-6 in any of the groups. CONCLUSIONS: Type 2 diabetes mellitus is associated with impaired endothelial function and increased levels of TNF-alpha, IL-6 and sVCAM-1, especially in patients with DM and CAD. Vitamin C significantly increased forearm vasodilatory response to reactive hyperaemia only in patients with combined DM and CAD.  相似文献   
38.
为筛选出操作方法简便,结果稳定可控的大鼠创伤性肠粘连模型,观察中药复方黄厚排气颗粒对其粘连程度的影响,选用SD大鼠,手术造成肠粘连模型,用中药复方2.5、5.0、10.0g/kg连续治疗7d后观察肠粘连程度。结果表明,以盲肠型动物模型的制备较为理想,手术易于操作,结果稳定可控。用中药复方治疗后模型动物的肠粘连程度得到明显改善。提示黄厚排气颗粒对术后肠粘连有一定的预防作用。  相似文献   
39.
目的探讨妊高征(PIH)合并胎儿宫内发育迟缓(IUGR)时胎盘病理改变与胎盘组织中血管细胞粘附分子-1(VCAM-1)表达水平变化的关系。方法选取本院2001年1~9月分娩的妊高征合并IUGR患者(实验组)胎盘30例、单纯IUGR(IUGR组)28例、单纯PIH(PIH组)25例、正常妊娠(正常妊娠组)30例,常规HE染色及PAS染色,观察胎盘形态学变化。利用免疫组化方法对胎盘组织切片染色,观察子宫蜕膜层中螺旋动脉、绒毛组织滋养细胞及绒毛中毛细血管的VCAM-1表达。结果实验组中22例(73.33%)胎盘有明显病理改变,有病理改变的胎盘蜕膜组织内血管内皮细胞及胎盘绒毛毛细血管内皮VCAM-1的表达显著高于无病理改变者(P<0.001);而绒毛上皮组织滋养层细胞VCAM-1的表达则显著低于无病理改变者(P=0.019)。结论妊高征合并IUGR时胎盘发生了明显的病理改变,这种病理改变与胎盘中VCAM-1的异常表达密切相关。  相似文献   
40.
目的探讨白细胞的粘附在初发期急性肾小管坏死(ATN)的病理生理学过程中所起的作用。方法Wistar雄性大鼠32只,随机分为4组。肌肉注射甘油制作ATN动物模型,应用细胞间粘附分子-1单抗防治初发期大鼠ATN,观察其肾脏病理学及血尿素氮和血肌酐变化。结果给药24 h后治疗组血肌酐值[(412.31±94.42)μmol/L]明显低于CD3对照组血肌酐[(990.21±171.25)μmol/L](P<0.05)。模型组与CD3对照组可见明显肾小管坏死,而治疗组仅2例出现较轻的坏死灶。结论白细胞的粘附在ATN发病过程中具有重要作用,应用细胞间粘附分子-1单抗阻断白细胞的粘附能明显减轻肾脏病理改变。  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