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   491篇
  免费   23篇
  国内免费   2篇
电工技术   2篇
化学工业   118篇
金属工艺   8篇
机械仪表   11篇
建筑科学   25篇
矿业工程   1篇
能源动力   39篇
轻工业   31篇
水利工程   4篇
石油天然气   2篇
无线电   27篇
一般工业技术   98篇
冶金工业   57篇
原子能技术   3篇
自动化技术   90篇
  2024年   2篇
  2023年   7篇
  2022年   3篇
  2021年   14篇
  2020年   14篇
  2019年   23篇
  2018年   25篇
  2017年   24篇
  2016年   21篇
  2015年   19篇
  2014年   19篇
  2013年   48篇
  2012年   35篇
  2011年   35篇
  2010年   24篇
  2009年   21篇
  2008年   23篇
  2007年   20篇
  2006年   19篇
  2005年   13篇
  2004年   10篇
  2003年   3篇
  2002年   5篇
  2000年   6篇
  1999年   4篇
  1998年   14篇
  1997年   5篇
  1996年   8篇
  1995年   6篇
  1994年   2篇
  1993年   2篇
  1989年   3篇
  1986年   1篇
  1985年   2篇
  1984年   2篇
  1983年   2篇
  1982年   1篇
  1981年   2篇
  1980年   6篇
  1979年   4篇
  1978年   1篇
  1977年   2篇
  1976年   5篇
  1975年   1篇
  1974年   1篇
  1973年   2篇
  1968年   1篇
  1967年   2篇
  1957年   1篇
  1955年   1篇
排序方式: 共有516条查询结果,搜索用时 1 毫秒
41.
Nonalcoholic fatty liver disease (NAFLD) is strongly associated to the features of metabolic syndrome which can progress to cirrhosis, liver failure and hepatocellular carcinoma. However, the most common cause of mortality in people with NAFLD is not liver-related but stems from atherosclerotic cardiovascular disease (CVD). The prevalence of NAFLD is on the rise, mainly as a consequence of its close association with two major worldwide epidemics, obesity and type 2 diabetes (T2D). The exact pathogenesis of NAFLD and especially the mechanisms leading to disease progression and CVD have not been completely elucidated. Human fetuin-A (alpha-2-Heremans Schmid glycoprotein), a glycoprotein produced by the liver and abundantly secreted into the circulation appears to play a role in insulin resistance, metabolic syndrome and inflammation. This review discusses the links between NAFLD and CVD by specifically focusing on fetuin-A’s function in the pathogenesis of NAFLD and atherosclerotic CVD.  相似文献   
42.
Journal of Applied Electrochemistry - In this study, within the defined orthogonal array of Taguchi design, the hydrothermal process parameters have been optimized for fabricating the smallest...  相似文献   
43.
We have cloned from murine erythroleukemia (MEL) cells, thymus, and stomach the cDNA encoding the Ca2+-gated K+ (KCa) channel, mIK1, the mouse homolog of hIK1 (Ishii, T. M., Silvia, C., Hirschberg, B., Bond, C. T., Adelman, J. P., and Maylie, J. (1997) Proc. Natl. Acad. Sci.(U. S. A. 94, 11651-11656). mIK1 mRNA was detected at varied levels in many tissue types. mIK1 KCa channel activity expressed in Xenopus oocytes closely resembled the Kca of red cells (Gardos channel) and MEL cells in its single channel conductance, lack of voltage-sensitivity of activation, inward rectification, and Ca2+ concentration dependence. mIK1 also resembled the erythroid channel in its pharmacological properties, mediating whole cell and unitary currents sensitive to low nM concentrations of both clotrimazole (CLT) and its des-imidazolyl metabolite, 2-chlorophenyl-bisphenyl-methanol, and to low nM concentrations of iodocharybdotoxin. Whereas control oocytes subjected to hypotonic swelling remained swollen, mIK1 expression conferred on oocytes a novel, Ca2+-dependent, CLT-sensitive regulatory volume decrease response. Hypotonic swelling of voltage-clamped mIK1-expressing oocytes increased outward currents that were Ca2+-dependent, CLT-sensitive, and reversed near the K+ equilibrium potential. mIK1 mRNA levels in ES cells increased steadily during erythroid differentiation in culture, in contrast to other KCa mRNAs examined. Low nanomolar concentrations of CLT inhibited proliferation and erythroid differentiation of peripheral blood stem cells in liquid culture.  相似文献   
44.
This study replicates preliminary findings reporting a quantitative electroencephalographic (QEEG) profile of crack cocaine dependence in abstinence. All subjects (n = 52) met criteria for DMS-III-R cocaine dependence (in the form of crack), and were residing in a drug-free therapeutic community. Baseline QEEG evaluations were conducted at intake (5-10 days after last use of crack, and at follow-up (1 month after last reported use). Previous findings of significant excess of relative alpha power and deficit of absolute and relative delta and theta power were replicated in this expanded group. Abnormalities were greater in anterior than posterior regions, and disturbances in interhemispheric relationships were also observed. Further, QEEG showed little change in the interval between the first and second evaluations. This QEEG profile may reflect persistent alterations in neurotransmission as a possible consequence of chronic cocaine exposure.  相似文献   
45.
The major aim in search and rescue using mobile robots is to detect and reach trapped survivors and to support rescue operations through disaster environments. Our motivation is based on the fact that a search and rescue (SAR) robot can navigate within and penetrate a disaster area only if the area in question possesses connected voids. Traversability or penetrability of a disaster area is a primary factor that guides the navigation of a search and rescue (SAR) robot, since it is highly desirable that the robot, without hitting a dead end or getting stuck, keeps its mobility for its primary task of reconnaissance and mapping when searching the highly unstructured environment. We propose a novel percolation guidance that collaborates with entropy based SLAM under a switching control setting the priority to either position or map accuracy. This newly developed methodology has proven to combine the superiority of both percolator guidance and entropy based prioritization so that the active SLAM becomes speedy, with high coverage rate of the area as well as increased accuracy in localization. Our percolator guidance stems from a frontier based conditioning of a-posteriori occurrences of upcoming connected voids that uses the fact that every obstacle partially seen at the frontier of the explored domain has a spatial continuity into the unexplored area. The developed modular architecture is introduced in details and demonstrative examples are provided and discussed.  相似文献   
46.
MFI type inorganic carrier was used in two different cationic forms, hydrogen and calcium respectively. MFI-supported molybdenum and rhenium catalysts were prepared. The activities of the catalysts were compared for the aromatization reaction of methane. Higher activity values were attained with the catalysts supported on HZSM-5. Aromatics were also observed with the catalysts supported on CaZSM-5, despite their deficiency in acid sites. Highly dispersed rhenium is expected to be formed with the use of the inorganic carrier in calcium form. On the other hand, lower reaction rates were observed with rhenium supported on CaZSM-5, in spite of the improved dispersion of the active rhenium species on this catalyst. This was interpreted in terms of the critical role of the acid sites in the conversion of methane to aromatics, compared to the improved dispersion of the active metal.  相似文献   
47.
Melt rheology and crystallization behavior of polyamide 6 (PA 6) and microcrystalline cellulose (MCC) composites were systematically studied in this research. The incorporation of MCC into the PA 6 matrix resulted in higher complex viscosities (|η*|), storage modulus (G′), and shear viscosities than those of neat PA 6, especially at low frequencies. The orientation of rigid molecular chains in the composites introduced by the addition of MCC induced a strong shear thinning behavior with an increase in MCC loading. The non‐isothermal crystallization kinetics of PA 6 and MCC composites were investigated by differential scanning calorimetry. The Avrami and Tobin model were applied to describe the process of non‐isothermal crystallization and to determine the crystallization parameters of the composites. Analysis of the crystallization kinetics indicated that the Avrami (na) and Tobin exponent (nt) was altered by the MCC. It was also found that the Avrami and Tobin equations fit the empirical data well. POLYM. ENG. SCI., 54:739–746, 2014. © 2013 Society of Plastics Engineers  相似文献   
48.
SiAlONs are important materials for high-temperature applications and creep properties of SiAlONs are largely controlled by the amount and type of sintering additives. It has been established that heat treatment can reduce the amount of amorphous intergranular phase through crystallization. However, there is no study on the creep behavior of heat-treated SiAlON ceramics containing multication sintering additives. Therefore, the aim of the study was to investigate the effect of heat treatment on the creep properties of multication containing (Y-Sm-Ca oxides) α/β-SiAlON ceramics. The heat treatments of the sintered samples were carried out at 1600°C for 2 hours. The creep tests were carried out in the range 1300-1400°C under different loads (50-150 MPa). The existing phases and the microstructures of samples before and after creep were investigated using XRD and SEM techniques. It was found that heat treatment resulted in a better creep performance compared to as-sintered samples. The activation energy and stress exponent for heat-treated SiAlONs were also calculated as 708 ± 45 kJ/mol and 1.4, respectively. Compared to the sintered sample values, the results suggested that the acting creep mechanism of grain-boundary sliding and cavitation was reduced with the heat treatment.  相似文献   
49.
In this work, polyethylene glycol (PEG) as a phase change material (PCM) was incorporated with palygorskite (Pal) clay to develop a novel form-stable composite PCM (F-SCPCM). The Pal/PEG(40 wt%) composite was defined as F-SCPCM and characterized using SEM/EDS, FT-IR, XRD, DSC, and TGA techniques. The DSC results revealed that the F-SCPCM has a melting temperature of 32.5°C and latent heat capacity of 64.3 J/g for thermal energy storage (TES) applications. Thermal cycling test showed that the F-SCPCM had good cycling thermal/chemical stability after 500 cycles. The TGA data proved that that both cycled and non-cycled F-SCPCMs had considerable high thermal durability. Consequently, the created F-SCPCM could be considered as an additive material for production of green construction components with TES capability. POLYM. ENG. SCI., 60:909–916, 2020. © 2020 Society of Plastics Engineers  相似文献   
50.
Measurements of the internal geometry of a carbon fiber non-crimp 3D orthogonal woven composite are presented, including: waviness of the yarns, cross sections of the yarns, dimensions of the yarn cross sections, and local fiber volume fraction. The measured waviness of warp and fill yarns are well below 0.1%, which shows that the fabric termed here “non-crimp” has nearly straight in-plane fibers as-produced, and this feature is maintained after going through all steps of fabric handling and composite manufacturing. The variability of dimensions of the yarns is in the range of 4–8% for warp and fill directions, while the variability of the yarn spacing is in the range of 3–4%. These variability parameters are lower than respective ranges of variability of the yarn waviness and the cross-sectional dimensions in typical carbon 2D weave and 3D interlock weave composites, which are also illustrated in this work for comparison.  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