全文获取类型
收费全文 | 1309篇 |
免费 | 61篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 17篇 |
综合类 | 1篇 |
化学工业 | 470篇 |
金属工艺 | 33篇 |
机械仪表 | 39篇 |
建筑科学 | 27篇 |
矿业工程 | 2篇 |
能源动力 | 67篇 |
轻工业 | 129篇 |
水利工程 | 10篇 |
石油天然气 | 13篇 |
无线电 | 128篇 |
一般工业技术 | 203篇 |
冶金工业 | 68篇 |
原子能技术 | 7篇 |
自动化技术 | 164篇 |
出版年
2024年 | 5篇 |
2023年 | 22篇 |
2022年 | 45篇 |
2021年 | 63篇 |
2020年 | 35篇 |
2019年 | 36篇 |
2018年 | 66篇 |
2017年 | 59篇 |
2016年 | 57篇 |
2015年 | 44篇 |
2014年 | 60篇 |
2013年 | 98篇 |
2012年 | 75篇 |
2011年 | 64篇 |
2010年 | 64篇 |
2009年 | 56篇 |
2008年 | 46篇 |
2007年 | 35篇 |
2006年 | 25篇 |
2005年 | 28篇 |
2004年 | 19篇 |
2003年 | 23篇 |
2002年 | 25篇 |
2001年 | 14篇 |
2000年 | 12篇 |
1999年 | 18篇 |
1998年 | 26篇 |
1997年 | 16篇 |
1996年 | 18篇 |
1995年 | 11篇 |
1994年 | 7篇 |
1993年 | 16篇 |
1992年 | 12篇 |
1991年 | 9篇 |
1990年 | 8篇 |
1989年 | 15篇 |
1988年 | 7篇 |
1987年 | 9篇 |
1986年 | 14篇 |
1985年 | 8篇 |
1984年 | 15篇 |
1983年 | 9篇 |
1982年 | 12篇 |
1981年 | 10篇 |
1980年 | 14篇 |
1979年 | 6篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1976年 | 8篇 |
1975年 | 5篇 |
排序方式: 共有1378条查询结果,搜索用时 15 毫秒
41.
Laminar flame speeds and extinction limits of conventional and alternative jet fuels 总被引:7,自引:0,他引:7
Experimental results of laminar flame speeds and extinction stretch rates for the conventional (Jet-A) and alternative (S-8) jet fuels are acquired and compared to the results from our earlier studies for neat hydrocarbon surrogate components, including n-decane and n-dodecane. Specifically, atmospheric pressure laminar flame speeds are measured using a counterflow twin-flame configuration for Jet-A/O2/N2 and S-8/O2/N2 mixtures at preheat temperatures of 400, 450, and 470 K and equivalence ratios ranging from 0.7 to 1.4. The flow field is recorded using digital particle image velocimetry. Linear extrapolation is then applied to determine the unstretched laminar flame speed. Experimental data for the extinction stretch rates of the nitrogen diluted jet fuel/oxidizer mixtures as a function of equivalence ratio are also obtained. In addition, the experimental data of Jet-A are compared to the computed values using a chemical kinetic mechanism for a kerosene surrogate reported in literature. A sensitivity analysis is further performed to identify the key reactions affecting the laminar flame speed and extinction stretch rate for this kerosene surrogate. 相似文献
42.
M. Kamal Warshi Vikash Mishra Vinayak Mishra Rajesh Kumar P.R. Sagdeo 《Ceramics International》2018,44(12):13507-13512
Rare-earth orthoferrites (RFeO3) are well-known for the antiferromagnetic ground state. However, some of the recent experimental results suggest that the few members of RFeO3 family possess ferromagnetism. In the present investigation we report the possible origin of ferromagnetism in antiferromagnetic YFeO3 using density functional theory. For this purpose, we have considered pure as well as self-doping in YFeO3 i.e. by considering the point defect at Y, Fe and O sites. Our finding suggests that the point defects in YFeO3 results in the mixed-valence state of Fe, which may result in ferromagnetism through Zener double exchange mechanism. 相似文献
43.
44.
Astrid Ahlinder Tiziana Fuoco Álvaro Morales-López Mohammed A. Yassin Kamal Mustafa Anna Finne-Wistrand 《应用聚合物科学杂志》2020,137(15):48550
Although additive manufacturing through melt extrusion has become increasingly popular as a route to design scaffolds with complex geometries the technique if often limited by the reduction in molecular weight and the viscoelastic response when degradable aliphatic polyesters of high molecular weight are used. Here we use a melt extruder and fused filament fabrication printer to produce a reliable nondegradative route for scaffold fabrication of medical grade copolymers of L-lactide, poly(ε-caprolactone-co-L-lactide), and poly(L-lactide-co-trimethylene carbonate). We show that degradation is avoided using filament extrusion and fused filament fabrication if the process parameters are deliberately chosen based upon the rheological behavior, mechanical properties, and polymer composition. Structural, mechanical, and thermal properties were assessed throughout the process to obtain comprehension of the relationship between the rheological properties and the behavior of the medical grade copolymers in the extruder and printer. Scaffolds with a controlled architecture were achieved using high-molecular-weight polyesters exhibiting a large range in the elastic response causing negligible degradation of the polymers. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48550. 相似文献
45.
For sea water conversion in single-purpose plants, reverse osmosis (RO) is shown to be more economical than multistage flash (MSF) desalination over a wide range of unit size and fuel cost. Attention is focussed on vertical tube evaporation/vapor compression (VTE/VC) a self-contained, low-energy consuming thermal process which is potentially competitive with RO. 相似文献
46.
Capillary viscometers have been used extensively, because of their simplicity and reliability, to measure the viscosity of fluids over a wide range of shear rates. However, in capillary flow, the shear rate is not uniform throughout the capillary, a pressure gradient is established in the direction of flow, and the temperature of the fluid is nonuniform due to viscous dissipation. In the present work, a general, simple and practical method is proposed for correcting for the effects of pressure variation and viscous dissipation in determining the viscosity of polymer melts at high pressures. The method essentially involves the estimation of temperature, pressure, shear rate, and shear stress under a variety of experimental conditions at a predetermined point in the capillary. As such, it may be considered as a generalized extension of the classical Rabinowitsch-Mooney method for estimating true viscosity in capillary flow. 相似文献
47.
48.
M. R. Kamal N. R. Demarquette R. A. Lai-Fook T. A. Price 《Polymer Engineering and Science》1997,37(5):813-825
The commonly used thermodynamic theories (mean field theory and the square gradient theory) to predict interfacial tension between polymers have been modified. The results of these theoretical developments have not yet been fully tested and compared to experimental data. In this paper, experimental data for the effects of temperature, molecular weight, and molecular weight dispersity on interfacial tension for polypropylene/polystyrene polymer pairs are compared with the predictions of the new versions of the above theories. To evaluate these theories, it is necessary to know the Flory-Huggins interaction parameter for the polymer pairs studied. The relation correlating the Flory-Huggins interaction parameter to the Hildebrand solubility parameter was not suitable for evaluating the theoretical predictions of interfacial tension. Instead, the Flory Huggins interaction parameter was expressed as the sum of an enthalpic contribution, χH, and entropic contribution, χs. In the absence of reliable experimental values, a method was developed to evaluate the two contributions, based on interfacial tension data. The procedure provided an interaction parameter that is allowed to depend on molecular weight. When this approach was used, the predictions of only the new version of the square gradient theory were in good agreement with the experimental data for the influence of temperature and molecular weight on interfacial tension. However, the theory predicted the effect of polydispersity on interfacial tension only at high temperatures. 相似文献
49.
Mahsa Majzoobi Bahareh Sabery Asgar Farahnaky Taewee Tongdang Karrila 《Iranian Polymer Journal》2012,21(8):513-522
Starch in its native form, may not be able to provide functional properties such as high or low temperatures and shear forces bearings expected in modern industries. Therefore, it is usually modified to make it compatible for different applications. The main aim of this research was to study the effects of dual modification using cross-linking and annealing on physicochemical properties of wheat starch. Therefore, starch was first cross-linked using different levels of POCl3 (0, 0.1, 0.2, 0.4?%, w/w, starch basis) and then annealed at 40?°C for 72?h. Scanning electron micrographs showed the presence of some spots on the granules of the dual-modified samples. The results of differential scanning calorimetry showed that the onset, peak and conclusion temperatures and enthalpy increased upon dual modification. The X-ray diffraction pattern of the modified samples remained unchanged while water solubility and swelling decreased. The results of rapid visco analyzing showed lower peak, setback, breakdown and final viscosities for the dual-modified samples. These samples produced stronger gels as determined using a texture analyzer. In total, annealing of the cross-linked starch could enhance some of its functional properties for further applications. 相似文献
50.
Hesam Ghasemi Pierre J. Carreau Musa R. Kamal Seyed H. Tabatabaei 《Polymer Engineering and Science》2012,52(2):420-430
Polyethylene terephthalate (PET) nanocomposite films were prepared by cast extrusion followed by uniaxial stretching, using chill rolls. Transmission electron microscopy (TEM) and wide angle X‐ray diffraction (WAXD) showed that the clay layers were aligned in the machine direction (MD) in the PET/clay nanocomposite (PCN) films. Differential scanning calorimetry (DSC) showed that PCN films have higher crystallinity than the neat PET films, possibly due to the nucleating role of the silicate layers. The PCN films became hazier as the clay content increased, but the film transparency remained in the acceptable range. Oxygen permeability of the PCN films decreased by 23% compared to the neat PET film. This is comparable with predictions of models proposed in the literature. Silicate incorporation brought about 20% increase in the tensile modulus, while the puncture and tear propagation resistance were reduced, due to brittleness of the PCN films. The measured modulus (1.7 GPa) was somewhat smaller than the values predicted using the Pseudoinclusion model (2.1 GPa). POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers 相似文献