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   324篇
  免费   16篇
电工技术   2篇
化学工业   130篇
金属工艺   10篇
机械仪表   6篇
建筑科学   7篇
轻工业   41篇
水利工程   2篇
无线电   19篇
一般工业技术   64篇
冶金工业   35篇
原子能技术   1篇
自动化技术   23篇
  2022年   21篇
  2021年   41篇
  2020年   13篇
  2019年   9篇
  2018年   3篇
  2017年   13篇
  2016年   10篇
  2015年   6篇
  2014年   15篇
  2013年   18篇
  2012年   18篇
  2011年   17篇
  2010年   10篇
  2009年   14篇
  2008年   17篇
  2007年   11篇
  2006年   12篇
  2005年   10篇
  2004年   7篇
  2003年   6篇
  2002年   6篇
  2001年   3篇
  2000年   2篇
  1999年   3篇
  1998年   9篇
  1997年   7篇
  1996年   9篇
  1995年   8篇
  1994年   3篇
  1993年   3篇
  1992年   4篇
  1991年   1篇
  1990年   1篇
  1989年   1篇
  1988年   1篇
  1986年   1篇
  1985年   1篇
  1981年   1篇
  1980年   1篇
  1978年   1篇
  1977年   1篇
  1976年   2篇
排序方式: 共有340条查询结果,搜索用时 15 毫秒
61.
The corrosion mechanisms of Al–Cr–Fe and Al–Cu–Fe–Cr complex metallic alloys have been investigated by potentiodynamic and potentiostatic polarization. Very good passivation of the Al–Cr–Fe surface is exhibited from 1 M H2SO4 to 1 M NaOH solutions, which was confirmed by ICP-OES analysis over a period of 273 days. Potentiostatically formed passive films analysed by XPS revealed chromium enrichment in the outermost layer of the aluminium oxy-hydroxide film. Although Al–Cu–Fe–Cr showed passivation during potentiodynamic polarization, heavy active corrosion at OCP was revealed by ICP-OES. For the Al–Cu–Fe–Cr alloy, the 10% content of Cr is insufficient to maintain a protective “chemically stable” Cr oxide/hydroxide.  相似文献   
62.
The rheological and instrumental textural properties of the butters, margarines and spreads were determined in this study. Three factors affected on the rheology and the instrumental texture of the examined yellow fat products: temperature of the measurement, origin and the content of the fat. The results obtained at 5 and 20°?C showed significant differences (p ≤ 0.05) in spreadability and hardness. The highest hardness and the lowest spreadability values were recorded for the butters and mixed fat products with high fat content. Generally, milk fat content caused a significant increase of hardness and decrease of spreadability. The best spreadability was measured for the spreads with the lowest fat content. Adhesiveness and cohesiveness analysis revealed that the most adhesive and less cohesive were the products with high fat content, less adhesive and the most cohesive were spreads with the lowest content of lipids. All of the samples exhibited thixotropic and shear-thinning behavior. High correlation was found between spreadability and hardness. Apparent viscosity did not correlate with spreadability and hardness.  相似文献   
63.
The article presents results of structural studies of polycrystalline diamond thin films deposited by hot filament CVD on silicon substrates. The films were characterized using Scanning Electron Microscopy (SEM), Raman Spectroscopy (RS), Electron Backscattered Diffraction (EBSD), Energy Dispersive Spectroscopy (EDS) and Secondary Ion Mass Spectroscopy (SIMS). Both the EBSD patterns and Raman spectra confirm that the grains visible in the electron micrographs are diamond micro-crystallites. The residual stress in the films is found to be in the range between −4.29 GPa and −0.56 GPa depending on the sample thickness. No evidence of lonsdalite and graphite has been registered in the polycrystalline material of the investigated samples. Evidence of the existence of silicon carbide at the diamond/silicon interface is presented. It is also suggested that an amorphous carbonaceous film covers the silicon surface in the regions of holes in the thin diamond layers.  相似文献   
64.
The 36-item, self-report Holden Psychological Screening Inventory (HPSI; R. R. Holden, 1996) and the Psychopathy Checklist–Revised (PCL–R; R. D. Hare, 1991) were administered to 214 male, adult prison inmates in Canadian federal correctional facilities. The 12-item HPSI Social Symptomatology scale, a measure of antisocial behavior, demonstrated a large effect size in significantly differentiating between PCL–R-identified psychopaths and nonpsychopaths. HPSI scales not theoretically related to psychopathic behavior showed no such significant effects. Findings are interpreted as supporting the criterion validity of the Social Symptomatology scale and suggest that this brief, self-report screen has research and clinical merit. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
65.
The Investigation of Demage Monolith Ceiling Slab In recent years the monolith structures are cracked frequently, particularly in concrete walls and reinforced ceiling slab. Usually, the cracks are not the effect of the exterior loads. The reason of that situation lies in the material and in the processes, which occur in concrete during the bond. The paper presents this problem as an example of ceiling slab made of concrete with fly ashes. The large usefulness of nondestructive tests to diagnostics of damaged construction was underlined.  相似文献   
66.
Mathematical modeling of signaling pathways and regulatory networks has been supporting experimental research for some time now. Sensitivity analysis, aimed at finding model parameters whose changes yield significantly altered cellular responses, is an important part of modeling work. However, sensitivity methods are often directly transplanted from analysis of technical systems, and thus, they may not serve the purposes of analysis of biological systems. This paper presents a novel sensitivity analysis method that is particularly suited to the task of searching for potential molecular drug targets in signaling pathways. Using two sample models of pathways, p53/Mdm2 regulatory module and IFN-β-induced JAK/STAT signaling pathway, we show that the method leads to biologically relevant conclusions, identifying processes suitable for targeted pharmacological inhibition, represented by the reduction of kinetic parameter values. That, in turn, facilitates subsequent search for active drug components.  相似文献   
67.
Similar to many other respiratory viruses, SARS-CoV-2 targets the ciliated cells of the respiratory epithelium and compromises mucociliary clearance, thereby facilitating spread to the lungs and paving the way for secondary infections. A detailed understanding of mechanism involved in ciliary loss and subsequent regeneration is crucial to assess the possible long-term consequences of COVID-19. The aim of this study was to characterize the sequence of histological and ultrastructural changes observed in the ciliated epithelium during and after SARS-CoV-2 infection in the golden Syrian hamster model. We show that acute infection induces a severe, transient loss of cilia, which is, at least in part, caused by cilia internalization. Internalized cilia colocalize with membrane invaginations, facilitating virus entry into the cell. Infection also results in a progressive decline in cells expressing the regulator of ciliogenesis FOXJ1, which persists beyond virus clearance and the termination of inflammatory changes. Ciliary loss triggers the mobilization of p73+ and CK14+ basal cells, which ceases after regeneration of the cilia. Although ciliation is restored after two weeks despite the lack of FOXJ1, an increased frequency of cilia with ultrastructural alterations indicative of secondary ciliary dyskinesia is observed. In summary, the work provides new insights into SARS-CoV-2 pathogenesis and expands our understanding of virally induced damage to defense mechanisms in the conducting airways.  相似文献   
68.
Immunotherapy has become increasingly important in the treatment of colorectal cancer (CRC). Currently, CD73, also known as ecto-5′-nucleotidase (NT5E), has gained considerable interest as a potential therapeutic target. CD73 is one of the key enzymes catalyzing the conversion of extracellular ATP into adenosine, which in turn exerts potent immune suppressive effects. However, the role of CD73 expression on various cell types within the CRC tumor microenvironment remains unresolved. The expression of CD73 on various cell types has been described recently, but the role of CD73 on B-cells in CRC remains unclear. Therefore, we analyzed CD73 on B-cells, especially on tumor-infiltrating B-cells, in paired tumor and adjacent normal tissue samples from 62 eligible CRC patients. The highest expression of CD73 on tumor-infiltrating B-cells was identified on class-switched memory B-cells, followed by naive B-cells, whereas no CD73 expression was observed on plasmablasts. Clinicopathological correlation analysis revealed that higher CD73+ B-cells infiltration in the CRC tumors was associated with better overall survival. Moreover, metastasized patients showed a significantly decreased number of tumor-infiltrating CD73+ B-cells. Finally, neoadjuvant therapy correlated with reduced CD73+ B-cell numbers and CD73 expression on B-cells in the CRC tumors. As promising new immune therapies are being developed, the role of CD73+ B-cells and their subsets in the development of colorectal cancer should be further explored to find new therapeutic options.  相似文献   
69.
Biosynthesis of melatonin by cholangiocytes is essential for maintaining the function of biliary epithelium. However, this cytoprotective mechanism appears to be impaired in primary biliary cholangitis (PBC). MiR-132 has emerged as a mediator of inflammation in chronic liver diseases. The effect of melatonin on oxidative stress and bile acid-induced apoptosis was also examined in cholangiocyes overexpressing miR506, as a PBC-like cellular model. In PBC patients the serum levels of melatonin were found increased in comparison to healthy controls. Whereas, in cholangiocytes within cirrhotic PBC livers the melatonin biosynthetic pathway was substantially suppressed even though the expressions of melatonin rate-limiting enzyme aralkylamine N-acetyltransferase (AANAT), and CK-19 (marker of cholangiocytes) were enhanced. In cholangiocytes exposed to mitochondrial oxidative stress melatonin decreased the expression of proapoptotic stimuli (PTEN, Bax, miR-34), which was accompanied by the inhibition of a pivotal mediator of inflammatory response Nf-κB-p65 and the activation of antiapoptotic signaling (miR-132, Bcl2). Similarly, melatonin reduced bile acid-induced proapoptotic caspase 3 and Bim levels. In summary, the insufficient hepatic expression of melatonin in PBC patients may predispose cholangiocytes to oxidative stress-related damage. Melatonin, via epigenetic modulation, was able to suppress NF-κB signaling activation and protect against biliary cells apoptotic signaling.  相似文献   
70.
TNF-related apoptosis-inducing ligand (TRAIL) is a type II transmembrane protein capable of selectively inducing apoptosis in cancer cells by binding to its cognate receptors. Here, we examined the anticancer efficacy of a recently developed chimeric AD-O51.4 protein, a TRAIL fused to the VEGFA-originating peptide. We tested AD-O51.4 protein activity against human colorectal cancer (CRC) models and investigated the resistance mechanism in the non-responsive CRC models. The quantitative comparison of apoptotic activity between AD-O51.4 and the native TRAIL in nine human colorectal cancer cell lines revealed dose-dependent toxicity in seven of them; the immunofluorescence-captured receptor abundance correlated with the extent of apoptosis. AD-O51.4 reduced the growth of CRC patient-derived xenografts (PDXs) with good efficacy. Cell lines that acquired AD-O51.4 resistance showed a significant decrease in surface TRAIL receptor expression and apoptosis-related proteins, including Caspase-8, HSP60, and p53. These results demonstrate the effectiveness of AD-O51.4 protein in CRC preclinical models and identify the potential mechanism underlying acquired resistance. Progression of AD-O51.4 to clinical trials is expected.  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