全文获取类型
收费全文 | 1664篇 |
免费 | 56篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 14篇 |
综合类 | 1篇 |
化学工业 | 597篇 |
金属工艺 | 48篇 |
机械仪表 | 18篇 |
建筑科学 | 38篇 |
能源动力 | 106篇 |
轻工业 | 105篇 |
水利工程 | 10篇 |
石油天然气 | 7篇 |
无线电 | 113篇 |
一般工业技术 | 336篇 |
冶金工业 | 94篇 |
原子能技术 | 24篇 |
自动化技术 | 214篇 |
出版年
2024年 | 6篇 |
2023年 | 18篇 |
2022年 | 43篇 |
2021年 | 60篇 |
2020年 | 42篇 |
2019年 | 44篇 |
2018年 | 77篇 |
2017年 | 59篇 |
2016年 | 71篇 |
2015年 | 24篇 |
2014年 | 51篇 |
2013年 | 117篇 |
2012年 | 81篇 |
2011年 | 115篇 |
2010年 | 75篇 |
2009年 | 68篇 |
2008年 | 81篇 |
2007年 | 66篇 |
2006年 | 66篇 |
2005年 | 47篇 |
2004年 | 35篇 |
2003年 | 26篇 |
2002年 | 37篇 |
2001年 | 15篇 |
2000年 | 20篇 |
1999年 | 19篇 |
1998年 | 20篇 |
1997年 | 14篇 |
1996年 | 13篇 |
1995年 | 22篇 |
1994年 | 14篇 |
1993年 | 23篇 |
1992年 | 21篇 |
1991年 | 15篇 |
1990年 | 26篇 |
1989年 | 15篇 |
1988年 | 15篇 |
1987年 | 21篇 |
1986年 | 16篇 |
1985年 | 19篇 |
1984年 | 15篇 |
1983年 | 18篇 |
1982年 | 17篇 |
1981年 | 21篇 |
1980年 | 10篇 |
1979年 | 8篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1967年 | 2篇 |
排序方式: 共有1725条查询结果,搜索用时 15 毫秒
21.
The influence of the electron beam modification of a dual‐phase filler on the dynamic mechanical properties of styrene‐butadiene rubber (SBR) is investigated in the presence and absence of trimethylol propane triacrylate or triethoxysilylpropyltetrasulfide. Electron beam modification of the filler results in reduction of the tan δ at 70°C, a parameter for rolling resistance, and an increase in the tan δ at 0°C, a parameter for wet skid resistance of SBR vulcanizates. These modified fillers give significantly better overall performance in comparison with the control dual‐phase filler. This variation in properties is explained in terms of filler parameters such as the filler structure that leads to rubber occlusion and filler networking. These results are further corroborated using the master curves obtained by the time–temperature superposition principle. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2992–3004, 2003 相似文献
22.
Carl C. Gryte Christopher Koroneos Anil Agarwal Arie Hochberg 《Polymer Engineering and Science》1980,20(7):478-484
Graft copolymers were prepared by irradiation of poly(oxyethylene), PEO, aqueous solutions in presence of acrylic acid. Chain transfer to PEO controls the graft length, the measured chain transfer constant of the acrylic acid radicals to PEO being 4.11 × 10?4 at 25°C. The drag reduction characteristics of the graft copolymers were measured in the Reynolds number range 104–105 in a smooth-walled tube, 0.635 cm inside diameter. The drag reduction falls to near zero as the solution pH is lowered to 3, evidence of the formation of a PEO-poly(acrylic acid) coacervate. 相似文献
23.
The organic-inorganic hybrid nanocomposites comprising of poly(iminohexamethyleneiminoadipoyl), better known as Polyamide-6,6 (abbreviated henceforth as PA66), and silica (SiO2) were synthesized through sol-gel technique at ambient temperature. The inorganic phase was generated in situ by hydrolysis-condensation of tetraethoxysilane (TEOS) in different concentrations, under acid catalysis, in presence of the organic phase, PA66, dissolved in formic acid. Infrared (IR) spectroscopy was used to monitor the microstructural evolution of the silica phase in the PA66 matrix. Wide angle X-ray scattering (WAXS) studies showed that the crystallinity in PA66 phase decreased with increasing silica content. Atomic force microscopy (AFM) of the nanocomposite films revealed the dispersion of SiO2 particle with dimensions of <100 nm in the form of network as well as linear structure. X-ray silicon mapping further confirmed the homogeneous dispersion of the silica phase in the bulk of the organic phase. The melting peak temperatures slightly decreased compared to neat PA66, while an improvement in thermal stability by about 20 °C was achieved with hybrid nanocomposite films, as indicated by thermogravimetric analysis (TGA). Dynamic mechanical analysis (DMA) exhibited significant improvement in storage modulus (E′) for the hybrid nanocomposites over the control specimen. An increase in Young's modulus and tensile strength of the hybrid films was also observed with an increase in silica content, indicating significant reinforcement of the matrix in the presence of nanoparticles. Some properties of the in situ prepared PA66-silica nanocomposites were compared with those of conventional composites prepared using precipitated silica as the filler by solution casting from formic acid. 相似文献
24.
A coiled quartz tubular reactor has been designed to measure the intrinsic reaction kinetics for homogeneous reactions at high temperatures up to 1100°C. Actual gas residence times were less than 100 ms. A simple and well‐studied test reaction (i.e., the decomposition of nitrous oxide, N2O), with published intrinsic kinetics, was used to verify the operation of the experimental reactor. For this system, Peclet numbers (Pe = uL/DL) computed from experimental conversion data were greater than 1000, indicating that the plug flow assumption could be used with this reactor system to determine intrinsic rate expressions with errors of less than 5% for the conditions studied. 相似文献
25.
Chlorinated ground rubber tire (Cl‐GRT) particles were used as filler in a plasticized polyvinylchloride (PVC) to develop a melt‐processable rubber composition. Physical properties of the Cl‐GRT‐filled PVC compound showed improvement compared to the nonchlorinated counterpart. Interaction between Cl‐GRT and PVC was examined on the basis of results of stress relaxation, dynamic mechanical thermal analysis, and solvent swelling studies. The Cl‐GRT could be loaded upto 40 parts per hundred parts of PVC, and the composition still retains the elastomeric characteristics. The Cl‐GRT‐filled composite was found to be reprocessable like the unfilled PVC compound. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 622–631, 2002; DOI 10.1002/app.10352 相似文献
26.
27.
28.
In mobile commerce, companies provide location based services to mobile users, who report their locations with a certain level of granularity to maintain a degree of anonymity. This level of granularity depends on their perceived risk as well as the incentives they receive in the form of monetary benefits or improved mobile services. This paper formulates a quantitative model in which information theoretic metrics such as entropy, quantify the anonymity level of mobile users. The individual perceived risks of users and the benefits they obtain are defined as functions of their chosen location information granularity. The interaction between the mobile commerce company and its users is investigated using mechanism design techniques as a privacy game. The user best responses and optimal strategies for the company are derived under budgetary constraints on incentives, which are provided to users in order to convince them to share their private information at the desired level of granularity. Information limitations in the system are analyzed to capture more realistic scenarios where the companies do not have access to user utility functions. Iterative distributed algorithm and regression learning methods are investigated to design mechanisms that overcome these limitations. The results obtained are demonstrated with a numerical example and simulations based on real GPS data. 相似文献
29.
Anil?Kumar?Karanam Kenneth?E.?JansenEmail author Christian?H.?Whiting 《Engineering with Computers》2008,24(1):17-26
The pre-processing stage of finite element analysis of the Navier–Stokes equations is becoming increasingly important as the
desire for more general boundary conditions, as well as applications to parallel computers increases. The set up of general
boundary conditions and communication structures for parallel computations should be accomplished during the pre-processing
phase of the analysis, if possible, to ensure efficient computations for large scale problems in computational fluid dynamics.
This paper introduces a general methodology for geometry based boundary condition application and pre-computing of parallel
communication tasks.
A. K. Karanam was supported by NSF Grant No. 9985340.
C. H. Whiting was supported by a grant from NASA LaRC. 相似文献
30.
The role of the vertebral arteries in delaying loss of sensibility following neck sticking in slaughter calves was investigated. Vertebral artery blood flow was measured using probes before, during and after electrical stunning and slaughter. Systemic blood pressure, electrocorticogram, visually evoked responses and the occurrence of carotid occlusions were also recorded. When carotid occlusion occurred, the time to onset of brain failure was delayed based on the development of an isoelectric state. In addition, when carotid occlusion occurred the mean arterial blood pressure was sustained for longer following slaughter, and concurrently vertebral artery blood flow could be maintained at about 30% of its initial level for up to 3 min. In some animals vertebral artery flow increased substantially following sticking. When chest sticking was used no occlusion of vessels occurred, mean arterial blood pressure fell promptly (within 8 s) and the onset of an isoelectric state did not extend beyond one minute. In addition, visually evoked responses were not present after 5 s following chest sticking. 相似文献