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   997篇
  免费   25篇
  国内免费   1篇
电工技术   72篇
综合类   5篇
化学工业   234篇
金属工艺   24篇
机械仪表   44篇
建筑科学   14篇
能源动力   88篇
轻工业   74篇
无线电   80篇
一般工业技术   188篇
冶金工业   49篇
原子能技术   45篇
自动化技术   106篇
  2023年   5篇
  2022年   15篇
  2021年   15篇
  2020年   11篇
  2019年   8篇
  2018年   12篇
  2017年   15篇
  2016年   19篇
  2015年   17篇
  2014年   25篇
  2013年   57篇
  2012年   34篇
  2011年   56篇
  2010年   45篇
  2009年   54篇
  2008年   64篇
  2007年   53篇
  2006年   34篇
  2005年   45篇
  2004年   49篇
  2003年   43篇
  2002年   25篇
  2001年   29篇
  2000年   21篇
  1999年   22篇
  1998年   17篇
  1997年   28篇
  1996年   27篇
  1995年   20篇
  1994年   15篇
  1993年   4篇
  1992年   9篇
  1991年   11篇
  1990年   3篇
  1989年   8篇
  1988年   13篇
  1987年   10篇
  1986年   13篇
  1985年   13篇
  1984年   11篇
  1983年   9篇
  1982年   5篇
  1981年   5篇
  1980年   6篇
  1979年   4篇
  1978年   6篇
  1977年   4篇
  1976年   3篇
  1974年   3篇
  1968年   1篇
排序方式: 共有1023条查询结果,搜索用时 15 毫秒
51.
Polyacene capacitors   总被引:2,自引:0,他引:2  
We fabricated two types of polyacene capacitor with extremely stable polyacenic semiconductor (PAS) as the positive and negative electrodes. The first one is a coin-type PAS capacitor (six different sizes), which possesses large capacity with high reliability. Its capacity is much larger than that of the conventional electric double-layer capacitor which uses activated carbon as electrode. PAS capacitor can maintain more than 70% of the initial capacity even after 100 000 cycles. Moreover, this capacitor can be charged and discharged in a few minutes as well as at low rate. The second one is a cylinder-type PAS capacitor (diameter: 18 mm, height: 65 mm) which shows high capacity of 100 F and can discharge at the extremely high rate of 80 C. The coin-type PAS capacitor is currently used for memory back-up of electrical and communication equipment, and the cylinder-type is considered to be useful as power back-up for starting drive parts of electric equipment which needs high power density.  相似文献   
52.
53.
In present study, the collapse of void bubble in liquid has been simulated using moving particle semi-implicit (MPS) code. The liquid is described using moving particles and the bubble–liquid interface was set to be vacuum pressure boundary without interfacial heat mass transfer. The topological shape of bubble can be traced according to the motion and location of interfacial particles. The time dependent bubble diameter, interfacial velocity and bubble collapse time were obtained under wide parametric range. The comparison with Rayleigh and Zababakhin's prediction showed a good agreement which validates the applicability and accuracy on MPS method in solving present momentum problems. The potential void induced water hammer pressure pulse was also evaluated which is instructive for further material erosion study. The bubble collapse with non-condensable gas has been further simulated and the rebound phenomenon was successfully captured which is similar with vapor-filled cavitation phenomenon. The present study exhibits some fundamental characteristics of void bubble hydrodynamics and it is also expected to be instructive for further applications of MPS method to complicated bubble dynamics problems.  相似文献   
54.
Effects of incorporation of ionic groups and ionic interactions to a model polypeptide, poly(γ-benzyl-L-glutamate) (PBLG), are studied. Partial conversion of γ-benzyl-L-glutamate residues to glutamic acid residues does not change molecular conformation (α-helix) and shows little change in properties. By contrast, partial conversion to sodium glutamates (ionic groups) leads to conversion from a rigid rod to a semi-flexible rod at low ion contents and causes significant changes in thermal stability and birefringence. In solution, lyotropic liquid crystalline behavior of PBLG is lost at ion content as low as 3.2 mol %. In solid, birefringence is still observed at this ion content, suggesting thermotropic liquid crystallinity of this ionic PBLG. Molecular composites made of ionic PBLG as a reinforcer and poly(4-vinylpyridine) (PVP) as a matrix polymer show significant enhancement in strength and toughness as a result of ion-dipole interactions between the component polymers.  相似文献   
55.
Immunoglobulin A1 (IgA1) concentration in the plasma of patients with IgA nephropathy (IgAN) as the cause of renal failure is higher than that in the plasma of normal controls. IgA1 with abnormal sugars is considered to deposit in the glomerular mesangium, aggravating nephritis in IgAN. Jacalin is a lectin that recognizes sugars on IgA1. However, its selective-recognition for normal-type (ST type, NeuAc-α(2,3)-Gal-β(1,3)-GalNAc) and abnormal-type (T type, Gal-β(1,3)-GalNAc; Tn type, GalNAc; STn type, NeuAc-α(2,6)-GalNAc) sugars α-O-linked to serine/threonine in IgA1 is weak. Therefore, jacalin cannot be used for recognizing specific sugar types on IgA1. We attempted to develop a new recognition method for specific sugar types on IgA1 by utilizing the multirecognition capability of jacalin. Its binding abilities were regulated by heat denaturation with suitable template sugar (galactose or N-acetylgalactosamine). Further, we successfully prepared denatured-jacalin derivatives, which recognized ST-/T-type sugars on IgA1, by sugar-immobilized affinity chromatography. Enzyme-linked immunosorbent assay of denatured-jacalin derivatives, showed the ratios of abnormal sugars on IgA1 in the plasma of IgAN patients and normal controls to be approximately 60% and 20%, respectively. The results proved that profiling of sugar types in IgAN can successfully be performed by solely using jacalin derivatives.  相似文献   
56.
The magnetic susceptibility and the pressure-composition isotherm were measured simultaneously for Pd–Rh–H and Pd–Ag–H systems in order to clarify the effect of Rh or Ag substitution on the hydrogen uptake from viewpoint of the electronic band structure. The magnetic susceptibility of all Pd binary alloys prepared decreased monotonically with increasing hydrogen content. At high hydrogen contents, the magnetic susceptibility became approximately zero for Pd–Rh–H and Pd–Ag–H system, and the hydrogen content at which the magnetic susceptibility gives zero corresponded with the terminal of the plateau region in the isotherm curve. The results indicated that the magnetic susceptibility of hydride phase was almost zero for all Pd binary alloys. On the basis of the band structure of Pd metal, we concluded that atom substitution only affected shift of the energy at Fermi level, and the amount of the hydrogen uptake was dominated by the number of unoccupied d-band in the alloys.  相似文献   
57.
Power characteristics of an unbaffled aerated agitated vessel with unsteadily forward‐reverse rotating impellers, ie a new type of gas–liquid agitator named ‘AJITER’, treating viscous Newtonian liquids were studied experimentally. Measurements were first made on the agitation torque, ie the torque on the drive shaft on which forward–reverse rotating impellers with four delta‐type blades were attached, and the data obtained were analyzed by fitting them to an equation consisting of two terms with respect to the resistance of the fluid, one due to viscous drag and the other due to added moment of inertia. The effects of operating conditions and physical properties of liquids on the drag and added moment of inertia coefficients were then evaluated, and empirical relationships which estimate values of these coefficients, useful to predict the unsteady behavior and magnitude of agitation torque, were presented. Furthermore, equations were developed for estimating the average and maximum power consumptions as a function of the drag and added moment of inertia coefficients. Prediction of respective power levels in AJITER by these equations was also discussed. © 2001 Society of Chemical Industry  相似文献   
58.
Atomic resolution high voltage electron microscopy was applied in investigations of the atomic structure of [112] sigma3 CSL grain boundary of silicon. Images of the grain boundary, viewed in the < 110 > direction, showed two types of dark spots. One type was rod shaped, which represented an atomic pair aligned in the < 111 > direction. The other was a small round spot, which represented a single atomic column in the grain boundary. The atomic structure of [112] sigma3 CSL grain boundary was directly shown from the atomic-structure image.  相似文献   
59.
This paper proposes a novel and general method of glare generation based on wave optics. A glare image is regarded as a result of Fraunhofer diffraction, which is equivalent to a 2D Fourier transform of the image of given apertures or obstacles. In conventional methods, the shapes of glare images are categorized according to their source apertures, such as pupils and eyelashes and their basic shapes (e.g. halos, coronas, or radial streaks) are manually generated as templates, mainly based on statistical observation. Realistic variations of these basic shapes often depend on the use of random numbers. Our proposed method computes glare images fully automatically from aperture images and can be applied universally to all kinds of apertures, including camera diaphragms. It can handle dynamic changes in the position of the aperture relative to the light source, which enables subtle movement or rotation of glare streaks. Spectra can also be simulated in the glare, since the intensity of diffraction depends on the wavelength of light. The resulting glare image is superimposed onto a given computer‐generated image containing high‐intensity light sources or reflections, aligning the center of the glare image to the high‐intensity areas. Our method is implemented as a multipass rendering software. By precomputing the dynamic glare image set and putting it into texture memory, the software runs at an interactive rate.  相似文献   
60.
Abstract— A novel emitting vinyl polymer, poly[4‐(7‐{4‐[N,N‐bis(9,9‐dimethylfluoren‐2‐yl)amino]phenyl}‐2,1,3‐benzothiadiazol‐4‐yl)phenylethylene] (PVFABT), was designed and synthesized. The new vinyl polymer was found to form smooth amorphous films with a high glass‐transition temperature of 199°C. The polymer possesses bipolar character with both electron‐donating and accepting properties. It undergoes reversible anodic oxidation and cathodic reduction to give stable cation and anion radicals. It exhibits intense orange fluorescence in solution and as film. A multilayer organic electroluminescent device using PVFABT as an emitting material emitted orange light, exhibiting high performance.  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