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   3334篇
  免费   79篇
  国内免费   9篇
电工技术   108篇
综合类   1篇
化学工业   622篇
金属工艺   120篇
机械仪表   54篇
建筑科学   51篇
能源动力   77篇
轻工业   247篇
水利工程   12篇
石油天然气   5篇
武器工业   1篇
无线电   363篇
一般工业技术   596篇
冶金工业   923篇
原子能技术   86篇
自动化技术   156篇
  2023年   10篇
  2022年   45篇
  2021年   47篇
  2020年   14篇
  2019年   18篇
  2018年   36篇
  2017年   41篇
  2016年   48篇
  2015年   34篇
  2014年   66篇
  2013年   106篇
  2012年   94篇
  2011年   128篇
  2010年   89篇
  2009年   114篇
  2008年   110篇
  2007年   114篇
  2006年   101篇
  2005年   94篇
  2004年   99篇
  2003年   97篇
  2002年   97篇
  2001年   62篇
  2000年   60篇
  1999年   63篇
  1998年   385篇
  1997年   215篇
  1996年   153篇
  1995年   96篇
  1994年   124篇
  1993年   95篇
  1992年   42篇
  1991年   45篇
  1990年   47篇
  1989年   42篇
  1988年   40篇
  1987年   35篇
  1986年   33篇
  1985年   44篇
  1984年   15篇
  1983年   20篇
  1982年   26篇
  1981年   14篇
  1980年   17篇
  1979年   17篇
  1978年   14篇
  1977年   14篇
  1976年   44篇
  1975年   13篇
  1972年   9篇
排序方式: 共有3422条查询结果,搜索用时 15 毫秒
71.
In this paper, we propose that the urinary toxins from the wastewater be adsorbed on an adsorbent such as spherical activated carbon and the latter be regenerated by subjecting it to high temperatures to recycle activated carbon and also to recycle the water used in dialysis. We studied the adsorption of artificial waste dialysate, which is a mixed solution of urea, creatinine, and uric acid, and the separate solutions for each of these and found that their extents of adsorption onto the spherical activated carbon material were nearly identical. The amount of adsorption was approximately 1.4 mg·g-1 for urea, 18 mg·g-1 for creatinine, and 20 mg·g-1 for uric acid. The urea, creatinine, and uric acid adsorbed onto the spherical activated carbon decomposed on heat treatment at 500℃, and the adsorption capacity of the spherical activated carbon was regenerated. Our study successfully demonstrated that the spherical activated carbon can be recycled in the waste dialysate treatment process.  相似文献   
72.
Inhalational anesthetics was previously reported to suppress glioma cell malignancy but underlying mechanisms remain unclear. The present study aims to investigate the effects of sevoflurane and desflurane on glioma cell malignancy changes via microRNA (miRNA) modulation. The cultured H4 cells were exposed to 3.6% sevoflurane or 10.3% desflurane for 2 h. The miR-138, -210 and -335 expression were determined with qRT-PCR. Cell proliferation and migration were assessed with wound healing assay, Ki67 staining and cell count kit 8 (CCK8) assay with/without miR-138/-210/-335 inhibitor transfections. The miRNA downstream proteins, hypoxia inducible factor-1α (HIF-1α) and matrix metalloproteinase 9 (MMP9), were also determined with immunofluorescent staining. Sevoflurane and desflurane exposure to glioma cells inhibited their proliferation and migration. Sevoflurane exposure increased miR-210 expression whereas desflurane exposure upregulated both miR-138 and miR-335 expressions. The administration of inhibitor of miR-138, -210 or -335 inhibited the suppressing effects of sevoflurane or desflurane on cell proliferation and migration, in line with the HIF-1α and MMP9 expression changes. These data indicated that inhalational anesthetics, sevoflurane and desflurane, inhibited glioma cell malignancy via miRNAs upregulation and their downstream effectors, HIF-1α and MMP9, downregulation. The implication of the current study warrants further study.  相似文献   
73.
This paper presents original research results of automatic polishing on curved surfaces of aluminium alloy moulds at constant pressure. The automatic polishing of aluminium alloy material is achieved. A parameter S is defined, which can express the comprehensive influential factors in the automatic polishing process and give a relationship among the polishing quality and the various machining variables. Based on this, a new method for comprehensive control of polishing quality is suggested.  相似文献   
74.
Humidity Sensor Characteristics of Woodceramics   总被引:9,自引:0,他引:9  
The humidity sensor characteristics of Woodceramics were investigated. The Woodceramics used in this experiment were prepared at 650–900°C. The size of specimens selected was 1 × 1 × 10 mm . One was used as-cut and the other was polished. Above 700°C, the resistance of the specimen was below 50 and the decrease of resistance with increasing relative humidity was small. The specimen prepared at 650°C had a resistance of about 1 k. The resistance of as-cut specimens decreased with increase in relative humidity, but that of the polished specimen did not change significantly. The difference between as-cut and polished samples was explained by the differences in surface micro-structure.  相似文献   
75.
Bi0.5Na0.5TiO3 (BNT) and 0.94Bi0.5Na0.5TiO3·0.06BaTiO3 (BNT–BT) bulk ceramics with extensive 〈100〉 texture were prepared by the reactive-templated grain growth method, using platelike Bi4Ti3O12 (BIT) particles as templates for BNT. Calcined compacts were composed of matrix grains with random orientation and 〈100〉-oriented grains transformed from aligned BIT particles, and the texture developed by the growth of oriented grains during sintering. Ceramics with extensive texture were obtained by using the starting mixture containing the maximum concentration of platelike BIT to form the maximum volume fraction of oriented grains.  相似文献   
76.
77.
Yo Jin Kim 《Electrochimica acta》2004,49(19):3227-3234
Palladinized Nafion™ was prepared via ion-exchange and chemical reduction method. Palladium precursors and solvent systems determined the efficiency of the incorporation and distribution of nanoparticles. The tortuous thin Pd film was formed on the surface of membrane when Na+-Nafion™ and water were used. Pd nanoparticles enhanced the water uptake of Nafion™ and reduced its methanol uptake. And dispersed Pd nanoparticles in Nafion™ disturbed the proton conduction and methanol permeation simultaneously in Nafion™ cluster. In order to reduce methanol permeation of Nafion™ and keep its high conductivity, it was more efficient for Pd nanoparticles to distribute near the surface of membrane. Palladinized Nafion™ improved the performance of DMFC single cell operation by reducing the methanol permeation.  相似文献   
78.
The internal structure of spray-dried alumina granules was characterized by optical microscopy by immersing them in a liquid having a refractive index close to that of alumina. This method provides a unique technique for the detailed analysis of the internal structure of spray-dried granules.  相似文献   
79.
To model the molten globule structure of -lactalbumin, moleculardynamics (MD) simulations were carried out for the protein inexplicit water at high temperature. In these simulations, long-rangeCoulomb interactions were evaluated explicitly with an originalmethod (particle–particle and particle–cell: PPPC)to avoid artifacts caused by the cut-off. The MD simulationswere started from two initial conditions to verify that similarresults would be obtained. From the last 150 ps trajectoriesof the two MD simulations, two partially unfolded average structureswere obtained. These structures had the following common structuralfeatures which are characteristic of the molten globule state.The radii of gyration for these conformations were 7.4 and 9.6%larger than that of the native state. These values were almostthe same as the experimental value (9.6%) observed recentlyby small-angle X-ray scattering (Kataoka,M., Kuwajima,K., Tokunaga,F.and Goto,Y., 1997, Protein Sci., 6, 422–430). Furthermore,aromatic residues of clusters I and II in these structures werefar apart from each other except for Try103–Trp104. Thisresult is in good agreement with NMR experimental results forthe acid-denatured molten globule state (Alexandrescu et al.,1992, 1993); that is, NOE signals between the aromatic residueswere not observed, except for that of Try103–Trp104 inthe molten globule state. Other structural features of thesemodels for the molten globule state are discussed with referenceto native state structures.  相似文献   
80.
Effects of superficial gas velocities to a draft tube, to an annulus section and particle size on the solid circulation rate (G,) have been determined in an internally circulating fluidized bed (0.28 m I.D. × 2m high) with an orifice type draft tube. The solid circulation rate from the draft tube to an annulus section increases with increasing gas velocities to the draft tube(U d ) and annulus section (Ua) and consequent increase in pressure drop across the orifice (ΔPor). However, the values ofG s decrease by 7–21% with increasing particle size from 86 to 288 μm. The pressure drop across the orifice increases with increasingU d andU a . However, ΔPor decreases by 5–23% with increasing particle size. To predictG s in an internally circulating fluidized bed, a correlation is proposed as a function of ΔPor This paper is dedicated to Professor Dong Sup Doh on the occasion of his retirement Korea University.  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