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   527篇
  免费   90篇
  国内免费   34篇
电工技术   16篇
综合类   10篇
化学工业   152篇
金属工艺   38篇
机械仪表   31篇
建筑科学   34篇
矿业工程   1篇
能源动力   3篇
轻工业   46篇
水利工程   120篇
石油天然气   2篇
无线电   32篇
一般工业技术   69篇
冶金工业   7篇
原子能技术   42篇
自动化技术   48篇
  2025年   4篇
  2024年   5篇
  2023年   14篇
  2022年   26篇
  2021年   33篇
  2020年   15篇
  2019年   14篇
  2018年   17篇
  2017年   37篇
  2016年   52篇
  2015年   31篇
  2014年   51篇
  2013年   56篇
  2012年   32篇
  2011年   42篇
  2010年   37篇
  2009年   14篇
  2008年   24篇
  2007年   16篇
  2006年   19篇
  2005年   12篇
  2004年   18篇
  2003年   11篇
  2002年   6篇
  2001年   7篇
  2000年   15篇
  1999年   4篇
  1998年   7篇
  1997年   4篇
  1996年   7篇
  1995年   2篇
  1994年   3篇
  1993年   3篇
  1992年   1篇
  1991年   1篇
  1990年   2篇
  1989年   1篇
  1988年   2篇
  1986年   2篇
  1983年   3篇
  1974年   1篇
排序方式: 共有651条查询结果,搜索用时 15 毫秒
101.
Although ischemic stroke has higher incidence and severity in aged than in young humans, the age factor is generally neglected in ischemia animal models. This study was aimed at comparing age-dependent effects at early stages of transient global cerebral ischemia (TGCI) in rats. TGCI was induced in two groups of rats (3–6 and 20–24 months old, respectively) by exposure to 15% oxygen and 15 min occlusion of the two common carotid arteries. Brains were analysed in vivo by MRI–apparent diffusion coefficient (ADC) and T2 maps–at 1–3 h post-TGCI and in vitro by histochemical examination of triphenyltetrazolium chloride (TTC)-stained slices. At 1–3 h post-TGCI, a higher incidence of lesions was found in aged than in young rats especially in the hippocampus and cortex (occipital plus parietal) but not in the thalamus. The lesioned regions showed lower ADC values in aged than in younger rats. The most substantial ADC decreases were associated with enhanced spin-spin relaxation and lower TTC staining. The different responses of the two age groups support the use of aged animals for investigations on different ischemia models. Our model of brain ischemia appears appropriate for further studies including drug effects.  相似文献   
102.
目的制备新生牛肝活性肽并评价其安全性。方法采用膜法分离制备新生牛肝活性肽。将3批制品于37~40℃,75%相对湿度条件下存放3个月,以多肽含量为指标观察其稳定性,并进行急性毒性试验、小鼠骨髓细胞微核试验、Ames试验、小鼠精子畸形试验和大鼠喂养试验。结果制备的3批新生牛肝活性肽存放3个月后,多肽含量无明显下降,质量稳定。小鼠和大鼠经口灌人大于20.0g/kg体重的新生牛肝活性肽,均无急性毒性。3种致突变试验均未显示出致突变性,大鼠喂养试验各项指标均未见明显毒性。结论新生牛肝活性肽未表现出明显毒性。  相似文献   
103.
    
Interleukin 6 (IL-6) is a prominent proinflammatory cytokine. Neuroinflammation in general, and IL-6 signaling in particular, appear to play a major role in the pathobiology and pathophysiology of aneurysm formation and aneurysmal subarachnoid hemorrhage (SAH). Most importantly, elevated IL-6 CSF (rather than serum) levels appear to correlate with delayed cerebral ischemia (DCI, “vasospasm”) and secondary (“vasospastic”) infarctions. IL-6 CSF levels may also reflect other forms of injury to the brain following SAH, i.e., early brain damage and septic complications of SAH and aneurysm treatment. This would explain why many researchers have found an association between IL-6 levels and patient outcomes. These findings clearly suggest CSF IL-6 as a candidate biomarker in SAH patients. However, at this point, discrepant findings in variable study settings, as well as timing and other issues, e.g., defining proper clinical endpoints (i.e., secondary clinical deterioration vs. angiographic vasospasm vs. secondary vasospastic infarct) do not allow for its routine use. It is also tempting to speculate about potential therapeutic measures targeting elevated IL-6 CSF levels and neuroinflammation in SAH patients. Corticosteroids and anti-platelet drugs are indeed used in many SAH cases (not necessarily with the intention to interfere with detrimental inflammatory signaling), however, no convincing benefit has been demonstrated yet. The lack of a robust clinical perspective against the background of a relatively large body of data linking IL-6 and neuroinflammation with the pathophysiology of SAH is somewhat disappointing. One underlying reason might be that most relevant studies only report correlative data. The specific molecular pathways behind elevated IL-6 levels in SAH patients and their various interactions still remain to be delineated. We are optimistic that future research in this field will result in a better understanding of the role of neuroinflammation in the pathophysiology of SAH, which in turn, will translate into the identification of suitable biomarkers and even potential therapeutic targets.  相似文献   
104.
    
The acute toxicity and the genotoxicity of four colored smokes were studied by an in vitro method based on the exposure of human bronchial epithelial cell cultures to the smokes. All smoke formulations consisted of the oxidizer fuel mixture (potassium chlorate/lactose), talcum and the following dyes: 1,4‐dihydroxy anthraquinone (orange), 1‐(p‐tolylamino)‐4‐hydroxy anthraquinone (violet), 1‐methylamino anthraquinone (red) and 4,4′‐methylidyne‐bis‐3‐methyl‐1‐phenyl‐2‐pyrazolin‐5‐one (yellow). The experiments were carried out in a laboratory scale chamber and in a large container. The toxicity was compared to that of hexachloroethane (HC)‐based reference smoke with known toxicity. All the colored smokes displayed acute toxicity. The order of toxicity in the laboratory scale tests was orange>violet≈red>HC>yellow and in the container tests orange>violet≈yellow>red. The orange smoke appeared genotoxic in all the tests. With the yellow and the violet smokes, the genotoxicity could not be totally excluded. The red smoke showed evidence of weak genotoxicity only in one test series at the highest concentration level.  相似文献   
105.
Ischemic and hemorrhagic strokes are associated with severe functional disability and high mortality. Except for recombinant tissue plasminogen activator, therapies targeting the underlying pathophysiology of central nervous system (CNS) ischemia and hemorrhage are strikingly lacking. Sur1-regulated channels play essential roles in necrotic cell death and cerebral edema following ischemic insults, and in neuroinflammation after hemorrhagic injuries. Inhibiting endothelial, neuronal, astrocytic and oligodendroglial sulfonylurea receptor 1–transient receptor potential melastatin 4 (Sur1–Trpm4) channels and, in some cases, microglial KATP (Sur1–Kir6.2) channels, with glibenclamide is protective in a variety of contexts. Robust preclinical studies have shown that glibenclamide and other sulfonylurea agents reduce infarct volumes, edema and hemorrhagic conversion, and improve outcomes in rodent models of ischemic stroke. Retrospective studies suggest that diabetic patients on sulfonylurea drugs at stroke presentation fare better if they continue on drug. Additional laboratory investigations have implicated Sur1 in the pathophysiology of hemorrhagic CNS insults. In clinically relevant models of subarachnoid hemorrhage, glibenclamide reduces adverse neuroinflammatory and behavioral outcomes. Here, we provide an overview of the preclinical studies of glibenclamide therapy for CNS ischemia and hemorrhage, discuss the available data from clinical investigations, and conclude with promising preclinical results that suggest glibenclamide may be an effective therapeutic option for ischemic and hemorrhagic stroke.  相似文献   
106.
目的根据产后子宫超声影像学数据建模,探讨产后出血情况的评测。方法通过经腹超声动态观测60例产妇的产后24h内及产后6周,测量采集子宫肌壁厚度、宫腔分离大小及子宫体长、宽、厚等数据,并记录产后24h内的出血量。结果经数据分析表明产后24h内的出血量与胎盘娩出后宫腔分离大小及产后6周的子宫复旧成正相关性(P<0.05),而与胎盘娩出后胎盘附着面宫壁厚度之间无明显的相关性(P>0.05)。结论监测产后的宫腔分离和子宫体复旧情况有助于动态分析产后出血的发展及转归,并为临床采取相应措施提供有力的依据。  相似文献   
107.
目的探讨庆大霉素(Gentamycin,GM)诱导急性肾损伤大鼠模型肾损伤分子-1(Kidney injury molecule-1,KIM-1)的表达。方法建立GM诱导大鼠急性肾损伤模型;检测各组大鼠血、尿各项生化指标;取大鼠肾组织,进行病理组织学观察;ELISA法检测各组大鼠尿液中KIM-1的分泌;RT-PCR法检测各组大鼠肾组织KIM-1mRNA的表达;免疫组织化学SP法检测各组大鼠肾组织KIM-1、α-平滑肌肌动蛋白(α-SMA)、波形蛋白(Vimentin)的表达。结果与对照组比较,模型组大鼠血、尿各项生化指标及病理组织学观察均出现不同程度的病变;ELISA检测显示,大鼠尿液中KIM-1的含量显著增高(P<0.05);RT-PCR检测显示,肾组织KIM-1mRNA表达上调(P<0.05),且呈时间依赖性;免疫组化法检测显示,KIM-1表达量随肾损伤加重而显著升高,且呈时间依赖性。结论 KIM-1具有良好的敏感性和特异性,可作为GM所致肾小管损伤的早期诊断标志物。  相似文献   
108.
将小白鼠随机分组,用四氯化碳(CCl4)造成急性肝损伤模型,以sHGF进行治疗。结果sHGF治疗组的小鼠血清GPT水平比肝损伤组明显降低(P<0.001);肝细胞变性、坏死等病理损伤也比肝损伤组明显减轻,可见大量的新生肝细胞;肝细胞超微结构提示,治疗组肝细胞核及胞浆内各种细胞器的损伤程度,比肝损伤组明显减轻,尤以线粒体和粗面内质网更为明显。  相似文献   
109.
We previously reported that Antp-TPR hybrid peptide inhibited the interaction of Hsp90 with TPR2A and had selective cytotoxic activity discriminating between normal and cancer cells to induce cancer cell death. In this study, we investigated the cytotoxic activity of Antp-TPR peptide toward acute myeloid leukemia (AML) cells. It was demonstrated that Antp-TPR peptide induced AML cell death in cell lines such as U937, K562, THP-1, and HL-60 via activation of caspases 3 and 7, and disruption of mitochondrial membrane potential. Conversely, Antp-TPR peptide did not reduce the viability of normal cells including peripheral blood mononuclear cells (PBMCs), although both geldanamycin and 17-AAG, small-molecule inhibitors of Hsp90, mediated cytotoxicity to these normal cells at low concentrations. In addition, mutation analysis of TPR peptide demonstrated that the highly conserved amino acids Lys and Arg were critical to the cytotoxic activity. These results indicated that Antp-TPR hybrid peptide would provide potent and selective therapeutic options in the treatment of AML.  相似文献   
110.
刘颖 《现代仪器》2006,12(6):13-14
目的评价急性胰腺炎患者的心电图变化对其预后及诊疗的价值。方法收集2001年1月—2006年1月在天津市南开医院确诊的新发急性胰腺炎患者(230例)的心电图,并进行回顾性分析,综合评价。结果230例急性胰腺炎患者,95例出现心电图异常(41.31%),其中:急性水肿性胰腺炎(MAP)174例,出现心电图异常为61例(35.06%);出血坏死性胰腺炎(SAP)56例,出现心电图异常为34例(60.71%)。结论心电图的变化对急性胰腺炎预后及诊疗均具有一定的临床意义。  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