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   677篇
  免费   40篇
  国内免费   14篇
耳鼻咽喉   3篇
儿科学   7篇
妇产科学   4篇
基础医学   86篇
口腔科学   19篇
临床医学   38篇
内科学   82篇
皮肤病学   16篇
神经病学   65篇
特种医学   15篇
外科学   52篇
综合类   63篇
预防医学   36篇
眼科学   10篇
药学   162篇
中国医学   40篇
肿瘤学   33篇
  2023年   4篇
  2022年   7篇
  2021年   16篇
  2020年   18篇
  2019年   12篇
  2018年   9篇
  2017年   15篇
  2016年   19篇
  2015年   28篇
  2014年   33篇
  2013年   64篇
  2012年   36篇
  2011年   46篇
  2010年   37篇
  2009年   24篇
  2008年   18篇
  2007年   23篇
  2006年   15篇
  2005年   25篇
  2004年   16篇
  2003年   19篇
  2002年   16篇
  2001年   18篇
  2000年   8篇
  1999年   13篇
  1998年   12篇
  1997年   12篇
  1996年   14篇
  1995年   13篇
  1994年   17篇
  1993年   6篇
  1992年   16篇
  1991年   9篇
  1990年   6篇
  1989年   8篇
  1988年   3篇
  1987年   10篇
  1986年   5篇
  1985年   11篇
  1984年   7篇
  1983年   5篇
  1982年   7篇
  1981年   6篇
  1980年   10篇
  1979年   3篇
  1978年   6篇
  1976年   2篇
  1975年   1篇
  1972年   1篇
  1968年   1篇
排序方式: 共有731条查询结果,搜索用时 46 毫秒
1.
目的:研究CD10蛋白在结直肠癌组织中的表达及其与结直肠癌的各临床病理指标之间的关系,探讨其在结直肠癌发生、发展中的作用。方法:收集78例结直肠癌组织标本及22例癌旁正常组织样本,运用免疫组化EliVision法检测CD10蛋白的表达,并采用卡方检验分析其表达强度及分布比例与结直肠癌临床病理指标的关系。结果:CD10蛋白在结直肠癌组织和正常结肠黏膜组织中的阳性表达率分别为46.2%(36/78)和0,差异有统计学意义(P < 0.01)。结直肠癌组织中CD10蛋白表达比例与各临床病理指标均无明显相关(P > 0.05)。结直肠癌组织中CD10蛋白表达强度与患者性别、年龄、肿瘤部位、分化程度、浸润深度无明显相关(P > 0.05),而与肿瘤的临床分期、有无脉管侵犯及淋巴结转移有关(P < 0.05),中晚期结直肠癌CD10蛋白表达强度高于早期肿瘤(P=0.033),周围淋巴结转移阳性的结直肠癌CD10蛋白表达强度高于淋巴结阴性病例(P=0.023),存在脉管受侵犯的结直肠癌CD10蛋白表达强度高于无脉管受侵病例(P=0.004)。结论:CD10蛋白在结直肠癌组织中呈高表达,且表达强度与肿瘤的临床分期、有无脉管侵犯及淋巴结转移有关,可能有促进结直肠癌发展和浸润转移的作用。  相似文献   
2.
3.
The objective was to develop a laboratory procedure to validate American Urological Association (AUA) Guideline on vasectomy success when nonmotile spermatozoa are found in the post-vasectomy ejaculate. The neutral α-glucosidase (NAG) an epididymal protein assay modified to determine the activity at 30 and 90 min of incubation from 24 pre- and 47 post-vasectomy ejaculates. The difference between the two points in the relative activity was calculated and if the difference was nonsignificant will confirm vasectomy success. The mean differences in the relative NAG activity were significantly different in pre- and post-vasectomy ejaculates, respectively. The mean differences in the relative NAG activity were similar in post-vasectomy ejaculates with and without nonmotile spermatozoa. No difference in relative NAG activity in post-vasectomy ejaculates between two time points of incubation may be a reliable method to confirm occlusion of the vas deferens. It also validates the recommendation by AUA Guideline on vasectomy success in the presence of few nonmotile spermatozoa.  相似文献   
4.
The present study aimed at identifying the neural responses associated with the incidental processing of the emotional valence of single words using event-related functional magnetic resonance imaging (fMRI). Twenty right-handed participants performed a visual lexical decision task, discriminating between nouns and orthographically and phonologically legal nonwords. Positive, neutral and negative word categories were matched for frequency, number and frequency of orthographic neighbors, number of letters and imageability. Response times and accuracy data differed significantly between positive and neutral, and positive and negative words respectively, thus, replicating the findings of a pilot study. Words showed distributed, mainly left hemisphere activations, indicating involvement of a neural network responsible for semantic word knowledge. The neuroimaging data further revealed areas in left orbitofrontal gyrus and bilateral inferior frontal gyrus with greater activation to emotional than to neutral words. These brain regions are known to be involved in processing semantic and emotional information. Furthermore, distinct activations associated with positive words were observed in bilateral middle temporal and superior frontal gyrus, known to support semantic retrieval, and a distributed network, namely anterior and posterior cingulate gyrus, lingual gyrus and hippocampus when comparing positive and negative words. The latter areas were previously associated with explicit and not incidental processing of the emotional meaning of words and emotional memory retrieval. Thus, the results are discussed in relation to models of processing semantic and episodic emotional information.  相似文献   
5.
目的:观察乳腺癌细胞系MCF7细胞中,钙激活中性蛋白酶2(calpain-2)对整合素(integrin)β4水解的影响。方法:利用"短发夹"RNA(shRNA)和微小RNA(mirRNA)技术结合的calpain-2基因沉默(gene silencing)慢病毒质粒(GIPZ lentiviral shRNAmir)转染乳腺癌细胞株MCF7,嘌呤霉素筛选稳定沉默calpain-2基因的细胞株,细胞株传4代,用荧光显微镜观察转染效率,用蛋白质印迹(Western blot)实验检测calpain-2基因沉默效率及integrinβ4水解的情况。结果:嘌呤霉素筛选、细胞传4代,荧光显微镜下观察显示转染和筛选后,EGFP表达阳性的MCF7细胞的比例分别达到(95.6±2.6)%(空shRNAmir载体)、(97.1±1.7)%(Calpain-2 shRNAmir1)和(97.7±0.2)%(Calpain-2 shRNAmir 2),差异无统计学意义(P>0.05);Western blot结果显示,基因沉默的MCF7细胞中calpain-2的表达被明显抑制,相对于空shRNAmir载体转染的MCF7细胞,差异有统计学意义(P<0.01),calpain-2的表达下调到21.5%(Calpain-2 shRNAmir 1)和18.8%(Calpain-2 shRNAmir 2),空shRNAmir载体转染的MCF7细胞中calpain-2的表达与未转染的MCF7细胞比较,差异无统计学意义(P>0.05);比较calpain-2基因沉默和空shRNAmir载体转染的MCF7细胞,发现integrinβ4均被水解,水解片段的分子量主要有200 k D、130和95 k D;calpain-2基因沉默后,calpain-2基因沉默MCF7细胞中200 k D的水解片段比空shRNAmir载体转染的MCF7细胞减少(P<0.01)。结论:在乳腺癌细胞MCF7中,calpain-2可能参与integrinβ4的200 k D片段的形成,从而参与调整integrinβ4的构象变化。  相似文献   
6.
目的:探讨油酸型急性肺损伤模型中IL‐8与RhoA的相关性。方法建立大鼠油酸急性肺损伤模型,检测各组大鼠肺湿/干重比及肺泡灌洗液(BALF)中中性粒细胞比例,比较肺组织病理学改变;采用聚合酶链反应检测肺组织匀浆RhoA表达,酶联免疫吸附法(ELISA )测定大鼠IL‐8的变化。结果肺W/D损伤组在2、6、12、24 h均较正常组明显升高,并且损伤组2 h比值最高;损伤组各时间点BALF中中性粒细胞计数比例明显高于正常组,24 h中性粒细胞细胞比例达峰值;损伤组个时间点血浆及BALF中IL‐8较正常组明显升高,两者具有相关性;损伤组各时间点RhoA的表达明显高于正常组。结论油酸型急性肺损伤大鼠中存在RhoA的高表达,RhoA表达增加可致IL‐8的表达增加,进而引起炎症细胞浸润。  相似文献   
7.
Background: The impact of a low-glucose peritoneal dialysis (PD) regimen on biomarkers of peritoneal inflammation, fibrosis and membrane integrity remains to be investigated.♦ Methods: In a randomized, prospective study, 80 incident PD patients received either a low-glucose regimen comprising Physioneal (P), Extraneal (E) and Nutrineal (N) (Baxter Healthcare Corporation, Deerfield, IL, USA) (PEN group), or Dianeal (control group) for 12 months, after which both groups continued with Dianeal dialysis for 6 months. Serum and dialysate levels of vascular endothelial growth factor (VEGF), decorin, hepatocyte growth factor (HGF), interleukin-6 (IL-6), macrophage migration inhibitory factor (MIF), hyaluronan (HA), adiponectin, soluble-intracellular adhesion molecule (s-ICAM), vascular cell adhesion molecule-1 (VCAM-1) and P-selectin, and dialysate cancer antigen 125 (CA125), were measured after 12 and 18 months. This paper focuses on results after 12 months, when patients in the PEN group changed to glucose-based PD fluid (PDF).♦ Results: At the end of 12 months, effluent dialysate levels of CA125, decorin, HGF, IL-6, adiponectin and adhesion molecules were significantly higher in the PEN group compared to controls, but all decreased after patients switched to glucose-based PDF. Macrophage migration inhibitory factor level was lower in the PEN group but increased after changing to glucose-based PDF and was similar to controls at 18 months. Serum adiponectin level was higher in the PEN group at 12 months, but was similar in the 2 groups at 18 months. Body weight, residual renal function, ultrafiltration volume and total Kt/V did not differ between both groups. Dialysate-to-plasma creatinine ratio at 4 h was higher in the PEN group at 12 months and remained so after switching to glucose-based PDF.♦ Conclusion: Changes in the biomarkers suggest that the PEN PD regimen may be associated with better preservation of peritoneal membrane integrity and reduced systemic vascular endothelial injury.  相似文献   
8.
Aflatoxins, a group of extremely toxic mycotoxins produced by Aspergillus flavus, A. parasiticus and A. nomius, can occur as natural contaminants of certain agricultural commodities, particularly maize. These toxins have been shown to be hepatotoxic, carcinogenic, mutagenic and cause severe human and animal diseases. The effectiveness of neutral electrolyzed oxidizing water (NEW) on aflatoxin detoxification was investigated in HepG2 cells using several validation methodologies such as the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, the induction of lipid peroxidation, the oxidative damage by means of glutathione modulation, the Ames test and the alkaline Comet assay. Our results showed that, after the aflatoxin-contaminated maize containing 360 ng/g was soaked in NEW (60 mg/L available chlorine, pH 7.01) during 15 min at room temperature, the aflatoxin content did not decrease as confirmed by the immunoaffinity column and ultra performance liquid chromatography methods. Aflatoxin fluorescence strength of detoxified samples was similar to untreated samples. However, aflatoxin-associated cytotoxicity and genotoxicity effects were markedly reduced upon treatment. According to these results, NEW can be effectively used to detoxify aflatoxin-contaminated maize.  相似文献   
9.
DNA double-strand breaks in mouse kidney cells with age   总被引:4,自引:0,他引:4  
A Biojector device fitted with a CO2 cartridge was used to prepare single cellsuspensions from kidneys of 12-month-(middle-aged) and 24-month-old (old) C57Bl/6mice. Microgel electrophoresis of DNA fromthese cells revealed a modest but significant7.3% increase (P = 0.04) in DNA double-strand breaks in old mice. This increase is equivalent to the DNA damage induced by 0.1 Gray of X-rays (5 double-strand breaks) in kidney cells of 10-month-old mice, as determined by a standard calibration curve. Greater DNA damage with aging was also positively correlated with higher levels of pathology in the kidneys.  相似文献   
10.
Summary Rats with streptozotocin-induced chronic diabetes mellitus develop a glomerulopathy functionally manifested by proteinuria. The ability of the glomerular capillary wall to retard filtration of macromolecules was examined in 5 chronically diabetic Munich-Wistar rats exhibiting excessive proteinuria (39±7mg/24h, mean±SEM) and 5 age-matched normal Munich-Wistar rats without increased proteinuria (4.7±0.2 mg/24 h). Urinary albumin excretion was not increased in the diabetic rats (2.0±0.6 mg/24h vs 1.6±0.3 mg/24h) suggesting that the normal net electronegative charge of the glomerular capillary wall was not altered. Fractional clearances of macromolecular neutral dextrans were similar in diabetic and normal rats throughout a wide range of molecular size (18–42 Å). Glomerular filtration rate was the same in the two groups of rats (2.77±0.16ml/min in diabetics and 2.72±0.11ml/ min in normals) suggesting that renal haemodynamic factors did not influence fractional clearances of neutral dextrans in diabetic rats. We conclude that the proteinuria exhibited by these chronically diabetic rats is not attributable to alterations of size-selective properties of the glomerular capillary wall, such as increases in the size or the number of pores.  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