全文获取类型
收费全文 | 1012篇 |
免费 | 62篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 18篇 |
综合类 | 4篇 |
化学工业 | 207篇 |
金属工艺 | 12篇 |
机械仪表 | 30篇 |
建筑科学 | 12篇 |
能源动力 | 49篇 |
轻工业 | 91篇 |
水利工程 | 6篇 |
石油天然气 | 1篇 |
无线电 | 145篇 |
一般工业技术 | 189篇 |
冶金工业 | 92篇 |
原子能技术 | 6篇 |
自动化技术 | 218篇 |
出版年
2024年 | 3篇 |
2023年 | 11篇 |
2022年 | 40篇 |
2021年 | 70篇 |
2020年 | 48篇 |
2019年 | 49篇 |
2018年 | 58篇 |
2017年 | 53篇 |
2016年 | 45篇 |
2015年 | 43篇 |
2014年 | 38篇 |
2013年 | 67篇 |
2012年 | 55篇 |
2011年 | 46篇 |
2010年 | 35篇 |
2009年 | 40篇 |
2008年 | 45篇 |
2007年 | 37篇 |
2006年 | 29篇 |
2005年 | 22篇 |
2004年 | 12篇 |
2003年 | 12篇 |
2002年 | 17篇 |
2001年 | 6篇 |
2000年 | 16篇 |
1999年 | 8篇 |
1998年 | 14篇 |
1997年 | 20篇 |
1996年 | 17篇 |
1995年 | 8篇 |
1994年 | 5篇 |
1993年 | 13篇 |
1992年 | 4篇 |
1991年 | 10篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 7篇 |
1985年 | 8篇 |
1984年 | 8篇 |
1983年 | 8篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 6篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 11篇 |
1974年 | 2篇 |
1972年 | 3篇 |
排序方式: 共有1080条查询结果,搜索用时 156 毫秒
61.
Heavy metal accumulation in vegetables irrigated with water from different sources 总被引:12,自引:0,他引:12
Monu Arora Bala Kiran Shweta Rani Anchal Rani Barinder Kaur Neeraj Mittal 《Food chemistry》2008,111(4):811-815
The present study was carried out to assess levels of different heavy metals like iron, manganese, copper and zinc, in vegetables irrigated with water from different sources. The results indicated a substantial build-up of heavy metals in vegetables irrigated with wastewater. The range of various metals in wastewater-irrigated plants was 116–378, 12–69, 5.2–16.8 and 22–46 mg/kg for iron (Fe), manganese (Mn), copper (Cu) and zinc (Zn), respectively. The highest mean levels of Fe and Mn were detected in mint and spinach, whereas the levels of Cu and Zn were highest in carrot. The present study highlights that both adults and children consuming vegetables grown in wastewater-irrigated soils ingest significant amount of these metals. However, the values of these metals were below the recommended maximum tolerable levels proposed by the [Joint FAO/WHO Expert Committee on Food Additives (1999). Summary and conclusions. In 53rd Meeting, Rome, June 1–10, 1999]. However, the regular monitoring of levels of these metals from effluents and sewage, in vegetables and in other food materials is essential to prevent excessive build-up of these metals in the food chain. 相似文献
62.
Gaurav Gupta 《Carbon》2005,43(7):1400-1406
A computational modeling study of texture formation in carbon-carbon composites based on carbon fibers and carbonaceous mesophase precursors is presented. The modeling predictions on texture formation and disclination structures are quantitatively validated with extensive experimental data. The number and type of disclinations displayed by the carbonaceous mesophase matrix is shown to be governed by the elasticity of the mesophase, the carbon fiber-mesophase interfacial energy, the size of the fibers, and positional arrangement of the fibers. The simulations provide new insights on the fundamental principles that govern texturing and disclination nucleation, and on how to control the structure of carbon-carbon composites through fiber concentration, fiber cross-section, and fiber-matrix interaction. 相似文献
63.
We consider a homogeneous product market and the incentive for oligopolists to share item-level product information with their customers. Enabled by Radio Frequency Identification technology, each firm has the option to record and reveal item-level information of a proportion of its products. We consider a two-stage game where each firm first decides its production plan and then determines its level of information revelation. With a constant clearance discount rate, we derive pure strategy equilibria that are subgame perfect and demonstrate that complete information sharing is the unique Nash equilibrium for the game when the common demand is volatile and that no information revelation is the unique Nash equilibrium when demand is not volatile. Furthermore, we show that the Nash equilibrium is the same with a decreasing clearance discount rate and that neither complete information revelation nor zero information revelation is consistent with an equilibrium with an increasing discount rate. Results are similar in a duopoly non-homogeneous product market scenario. 相似文献
64.
For the design and optimization of CO2 recovery from alcoholic fermentation processes by distillation, models for vapor-liquid equilibria (VLE) are needed. Two such thermodynamic models, the Peng-Robinson equation of state (EOS) and a model based on Henry’s law constants, are proposed for the ternary mixture N2 + O2 + CO2. Pure substance parameters of the Peng-Robinson EOS are taken from the literature, whereas the binary parameters of the Van der Waals one-fluid mixing rule are adjusted to experimental binary VLE data. The Peng-Robinson EOS describes both binary and ternary experimental data well, except at high pressures approaching the critical region. A molecular model is validated by simulation using binary and ternary experimental VLE data. On the basis of this model, the Henry’s law constants of N2 and O2 in CO2 are predicted by molecular simulation. An easy-to-use thermodynamic model, based on those Henry’s law constants, is developed to reliably describe the VLE in the CO2-rich region. 相似文献
65.
Shilpi Gupta Gaurav Rajauria Nissreen Abu‐Ghannam 《International Journal of Food Science & Technology》2010,45(3):482-489
Brown Irish edible seaweeds, Himanthalia elongata, Laminaria sachharina and Laminaria digitata, were evaluated for the microbiota in raw and heat processed form. Raw seaweeds showed complete absence of aerobic mesophiles, halophiles, yeasts and molds. However, heating at 85 °C for 15 min resulted in spore germination. Bacterial counts as high as 107 were observed for aerobic mesophiles and halophiles. Heating above 95 °C for 15 min resulted in complete inactivation of surface microflora. Bacteria belonging to Bacillaceae, Paenibacillaceae, Moraxellaceae and Enterobacteriaceae family were identified by 16S rRNA sequencing. In vitro antimicrobial activity of the methanolic extracts of the seaweed on food pathogenic and food spoilage bacteria were also evaluated. The seaweeds in their raw state had almost 100% inhibition against Listeria monocytogenes; 98% and 93% inhibition was achieved against Pseudomonas aeruginosa by H. elongata and L. saccharina extracts, respectively. Heating the seaweeds resulted in the reduction of antimicrobial activity as compared to raw. The effect was more pronounced against Gram negative bacteria. 相似文献
66.
Jagjiwan Mittal Shih-Ming Kuo Yu-Wei Lin Kwang-Lung Lin 《Journal of Electronic Materials》2009,38(12):2436-2442
Reflow behavior of Sn-Zn solder on Ni/Cu substrate was investigated in an infrared (IR) reflow furnace using different heating
rates from 180 °C/min to 36 °C/min. Energy dispersive spectroscopy (EDX) studies of the reflowed samples showed increased
diffusion of Zn from the solder to the intermetallic compound (IMC) layer with a decrease in heating rate. Higher interfacial
activity and affinity of the Zn in the formation of the IMC with the lowering of the heating rate were further demonstrated
by electron probe microanalyzer (EPMA) results. The Zn diffusion behavior was related to its higher reactivity and smaller
size in comparison with Sn, phase separation during heating, and affinity of Zn to form Ni-Sn-Zn and Ni-Zn intermetallic compounds. 相似文献
67.
68.
Shekhar Tyagi V. G. Sathe Gaurav Sharma Velaga Srihari Himanshu Kumar Poswal 《Journal of Materials Science》2018,53(10):7224-7232
In the earlier pressure-dependent Raman spectroscopic studies, it has been reported that BaTiO3 undergoes a tetragonal to cubic phase transition above ~ 2 GPa, whereas pressure-dependent X-ray absorption, X-ray diffuse scattering studies and pair distribution function studies have reported the presence of a low-symmetry rhombohedral phase above ~ 2.3 GPa. In this report, we present our pressure-dependent Raman spectroscopic studies on polycrystalline BaTiO3 which shows that it first undergoes a transition from tetragonal to orthorhombic/rhombohedral phase above ~ 2.6 GPa and then finally goes to the cubic phase above 8.4 GPa. Pressure-dependent synchrotron X-ray diffraction (SXRD) studies have also been carried out that provided rate of change of volume as a function of pressure resulting in bulk modulus of 215 ± 9 GPa. 相似文献
69.
The problem of video classification can be viewed as discovering the signature patterns in the elemental features of a video
class. In order to solve this problem, a large and diverse set of video features is proposed in this paper. The contributions
of the paper further lie in dealing with high-dimensionality induced by the feature space and in presenting an algorithm based
on two-phase grid searching for automatic parameter selection for support vector machine (SVM). The framework thus is directed
to bridge the gap between low-level features and semantic video classes. The experimental results and comparison with state-of-the-art
learning tools on more than 5000 video segments show the effectiveness of our approach. 相似文献
70.
Srivastava Shekhar Agrawal Gaurav Pioro Michal Medhi Deep 《Network and Service Management, IEEE Transactions on》2005,2(1):9-18
An important traffic engineering problem for OSPF networks is the determination of optimal link weights. Certainly, this depends on the traffic engineering objective. Regardless, often a variety of performance measures may be of interest to a network provider due to their impact on the network. In this paper, we consider different objectives and discuss how they impact the determination of the link weights and different performance measures. In particular, we propose a composite objective function; furthermore, we present a Lagrangian relaxation-based dual approach to determine the link weight system. We then consider different performance measures and discuss the effectiveness of different objectives through computational studies of a variety of network topologies. We find that our proposed composite objective function with Lagrangian relaxation-based dual approach is very effective in meeting different performance measures and is computationally very fast. 相似文献