全文获取类型
收费全文 | 14842篇 |
免费 | 1033篇 |
国内免费 | 34篇 |
专业分类
电工技术 | 240篇 |
综合类 | 34篇 |
化学工业 | 3737篇 |
金属工艺 | 468篇 |
机械仪表 | 768篇 |
建筑科学 | 286篇 |
矿业工程 | 7篇 |
能源动力 | 674篇 |
轻工业 | 1077篇 |
水利工程 | 47篇 |
石油天然气 | 26篇 |
武器工业 | 1篇 |
无线电 | 2670篇 |
一般工业技术 | 2979篇 |
冶金工业 | 977篇 |
原子能技术 | 137篇 |
自动化技术 | 1781篇 |
出版年
2023年 | 128篇 |
2022年 | 199篇 |
2021年 | 318篇 |
2020年 | 261篇 |
2019年 | 335篇 |
2018年 | 426篇 |
2017年 | 388篇 |
2016年 | 500篇 |
2015年 | 460篇 |
2014年 | 654篇 |
2013年 | 990篇 |
2012年 | 959篇 |
2011年 | 1039篇 |
2010年 | 830篇 |
2009年 | 894篇 |
2008年 | 772篇 |
2007年 | 634篇 |
2006年 | 625篇 |
2005年 | 523篇 |
2004年 | 486篇 |
2003年 | 497篇 |
2002年 | 477篇 |
2001年 | 347篇 |
2000年 | 330篇 |
1999年 | 309篇 |
1998年 | 515篇 |
1997年 | 313篇 |
1996年 | 238篇 |
1995年 | 192篇 |
1994年 | 161篇 |
1993年 | 143篇 |
1992年 | 104篇 |
1991年 | 97篇 |
1990年 | 85篇 |
1989年 | 90篇 |
1988年 | 57篇 |
1987年 | 74篇 |
1986年 | 58篇 |
1985年 | 48篇 |
1984年 | 50篇 |
1983年 | 46篇 |
1982年 | 22篇 |
1981年 | 32篇 |
1980年 | 22篇 |
1978年 | 26篇 |
1977年 | 23篇 |
1976年 | 37篇 |
1975年 | 15篇 |
1973年 | 18篇 |
1971年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Bong Keun Kim Wan Kyun Chung 《Industrial Electronics, IEEE Transactions on》2003,50(6):1207-1216
Disturbance-observer (DOB)-based controller design is one of the most popular methods in the field of motion control. In this paper, the generalized disturbance compensation framework, named the robust internal-loop compensator (RIC) is introduced and an advanced design method of a DOB is proposed based on the RIC. The mixed sensitivity optimization problem, which is the main issue of DOB design, is also solved through the parametrization of the DOB in the RIC framework. Differently from conventional methods, the Q-filter is separated from the mixed sensitivity optimization problem and a systematic design law for the DOB is proposed. This guarantees the robustness and optimality of the DOB and enables the design for unstable plants. 相似文献
2.
Wastewater discharge from coal refining plants contains a number of biologically toxic compounds; 2000-2500 mg/l of COD of which 40% is composed of phenol, 100-400 mg/l of thiocyanate, 10-40 mg/l of cyanide, 100-250 mg/l of NH4+-N and 150-300 mg/l of total nitrogen. In order to treat this kind of high strength wastewater, we have developed a high performance biofilm process using fluidizing bio-carriers of the tube chip type. The fluidizing biofilm carriers are made of a composite of polyethylene and several inorganic materials, whose density is controlled at 0.97-0.98 g/ml. The fluidizing biofilm carriers show sound fluidization characteristics inside bioreactors. The wastewater is treated using three consecutive series reactors in oxic-anoxic-oxic arrangement. Each reactor is charged with the fluidizing biofilm carriers of 50 vol%. Furthermore, newly cultured active microorganisms for the thiocyanate biodegradation are added in the biofilm process. At total hydraulic retention time of 2.2 days, this process can achieve steady state removal efficiencies: COD, 99%; thiocyanate, 99%; NH4+-N, 99% and total nitrogen, 90%. 相似文献
3.
ZnO thin film was deposited on various metal electrodes by reactive sputtering, and c-axis preferred orientation of the film has been studied. ZnO, which has high piezoelectricity, is promising for oscillators or filter devices such as surface acoustic wave (SAW) device, gas sensor, and film bulk acoustic resonator (FBAR). But, for the application of ZnO film for these devices, the film should be grown with c-axis normal to the electrode. In this study, Pt, Al, and Au were deposited on Si wafer, and the surface roughness and crystal structure of the ZnO film on the electrode were investigated using AFM, scanning electron microscopy (SEM), and X-ray diffraction (XRD). Columnar structures of ZnO films were grown with c-axis normal to all electrodes, and among them Pt electrode showed the highest preferred orientation of ZnO film. 相似文献
4.
One requirement in designing and operating and operating system is to minimize the moisture change in stored grain. Moisture transfer during the aeration process is generally believed to be caused by the partial pressure difference between water in grain and water in air (P3-P4). A mathematical model was developed for rough rice, which predicts the partial pressure difference under various grain and ambient conditions. Observations of moisture change over 10 aeration tests confirmed the good correlation between sorption phenomena and partial pressure differences. Studies indicated that air relative humidity, air temperature, grain temperature and grain moisture are significant factors influencing the partial pressure differences and, thus, affecting 相似文献
5.
Since electronic switching systems usually require very strict reliability requirements as well as good performance objectives, we need to jointly analyse the performance and reliability of switching systems. In this paper, we compare conventional time–space–time switches with single space switches with those with multiple separated space switches, from the viewpoints of reliability and performance. We consider time–space–time switching networks which consist of N incoming time switches, i.e. one NxN space switch, two (N/2)x(N/2) space switches, and four (N/4)x(N/4) space switches. We introduce a Markov reliability model to study the effect of failures and analyse the reliability and performance of three different types of switching networks in terms of average blocking probability and the mean time to unreliable operation, as we vary the offered traffic. As a result, T–S–T switching networks with multiple separated space switches exhibit better performance and reliability than those with single space switches. 相似文献
6.
S J Chung S Balaji M Matheswaran T Ramesh I S Moon 《Water science and technology》2007,55(1-2):261-266
This study investigates the hybrid mediated electrochemical oxidation (HMEO) technology, which is a newly developed non thermal electrochemical oxidation process for organic destruction. A combination of ozone and ultrasonication processes to the mediated electrochemical oxidation (MEO) process is termed as hybrid mediated electrochemical oxidation. The electrochemical cell was developed in this laboratory. In the present study, several organic compounds, such as phenol, benzoquinone and ethylenediaminetetraacetic acid (EDTA), were chosen as the model organic pollutants to be destructed by the hybrid process. The organic destruction was monitored based on the CO2 generation and total organic carbon (TOC) reduction. The HMEO process was found to be extremely effective in the destruction of all the target organics chosen in this study. The information obtained from this study will provide an insight in adopting this technique for dealing with more recalcitrant organics (POPs). 相似文献
7.
For multi-step heterogeneous consecutive reactions affected entirely by interphase diffusion under isothermal condition, the
equations for the effectiveness factors, the surface concentrations and the point yields were derived in terms of the Damkoehler
numbers or the measurables from the mass balances set up on the assumption that the mass-transfer rate balances the surface-reaction
rate at steady state.
From the analyses of the equations derived, the effectiveness factors for the intermediate steps and the surface concentrations
of intermediates were understood to be enhanced by the measurables inclusive of the concentrations and the mass-transfer coefficients.
Then the effect of the concentrations was concluded to be most significant. The effects of these measurables to the effectiveness
factors and the surface concentrations were qualitatively discussed for simple consecutive reactions and also for additive
consecutive reactions. Especially, as for two-step additive consecutive reactions, the effects of measurables η Da and the
concentrations to the effectiveness factors were examined with graphical presentations.
Finally, the brief discussion of the dependency of the Damkoehler number upon reaction time and the effect of the Renolds
number and diffusivity to the extent of the mass-transfer resistance were presented. 相似文献
8.
A systematic study of wall effects on the shear viscosity of short glass fiber-filled polypropylene and polystyrene is presented. The dependence of these effects on capillary radius, shear rate, temperature, and polymer matrix is examined. The “true” viscosity curves of these materials (free from wall effects) can be obtained by an extrapolation procedure. Breakage of glass fibers in the high shear-rate processes of extrusion and injection molding lead to an appreciable reduction of the viscosity of these materials and is probably the more important effect to take into account in these processes. 相似文献
9.
Shye Lin Wu Chung Len Lee Tan Fu Lei Chen C.F. Chen L.J. Ho K.Z. Ling Y.C. 《Electron Device Letters, IEEE》1994,15(4):120-122
In this study, it is demonstrated that the incorporation of fluorine can enhance poly-Si/Si interfacial oxide break-up in the poly-Si emitter contacted p+-n shallow junction formation. The annealing temperature for breaking up the poly-Si/Si interfacial oxide has been found to be as low as 900°C. As a result, the junction depth of the BF2-implanted device is much larger than that of the boron-implanted device 相似文献
10.
Tahui Wang Chimoon Huang Chou P.C. Chung S.S.-S. Tse-En Chang 《Electron Devices, IEEE Transactions on》1994,41(9):1618-1622
A two-dimensional numerical simulation including a new interface state generation model has been developed to study the performance variation of a LDD MOSFET after a dc voltage stress. The spatial distribution of hot carrier induced interface states is calculated with a breaking silicon-hydrogen bond model. Mobility degradation and reduction of conduction charge due to interface traps are considered. A 0.6 μm LDD MOSFET was fabricated. The drain current degradation and the substrate current variation after a stress were characterized to compare the simulation. A reduction of the substrate current at Vg ≃0.5 Vd in a stressed device was observed from both the measurement and the simulation. Our study reveals that the reduction is attributed to a distance between a maximum channel electric field and generated interface states 相似文献