全文获取类型
收费全文 | 182172篇 |
免费 | 16220篇 |
国内免费 | 8612篇 |
专业分类
电工技术 | 11574篇 |
技术理论 | 13篇 |
综合类 | 12012篇 |
化学工业 | 29724篇 |
金属工艺 | 10104篇 |
机械仪表 | 11477篇 |
建筑科学 | 13905篇 |
矿业工程 | 5560篇 |
能源动力 | 5362篇 |
轻工业 | 12938篇 |
水利工程 | 3362篇 |
石油天然气 | 10788篇 |
武器工业 | 1459篇 |
无线电 | 21908篇 |
一般工业技术 | 21746篇 |
冶金工业 | 8826篇 |
原子能技术 | 1949篇 |
自动化技术 | 24297篇 |
出版年
2024年 | 907篇 |
2023年 | 3447篇 |
2022年 | 6420篇 |
2021年 | 8601篇 |
2020年 | 6491篇 |
2019年 | 5106篇 |
2018年 | 5807篇 |
2017年 | 6483篇 |
2016年 | 5769篇 |
2015年 | 7732篇 |
2014年 | 9611篇 |
2013年 | 11485篇 |
2012年 | 12553篇 |
2011年 | 13168篇 |
2010年 | 11290篇 |
2009年 | 10671篇 |
2008年 | 10226篇 |
2007年 | 9361篇 |
2006年 | 9532篇 |
2005年 | 8159篇 |
2004年 | 5436篇 |
2003年 | 4532篇 |
2002年 | 4034篇 |
2001年 | 3627篇 |
2000年 | 3565篇 |
1999年 | 4155篇 |
1998年 | 3455篇 |
1997年 | 2932篇 |
1996年 | 2741篇 |
1995年 | 2213篇 |
1994年 | 1799篇 |
1993年 | 1298篇 |
1992年 | 1044篇 |
1991年 | 785篇 |
1990年 | 568篇 |
1989年 | 465篇 |
1988年 | 367篇 |
1987年 | 252篇 |
1986年 | 209篇 |
1985年 | 129篇 |
1984年 | 116篇 |
1983年 | 86篇 |
1982年 | 86篇 |
1981年 | 68篇 |
1980年 | 62篇 |
1979年 | 29篇 |
1978年 | 25篇 |
1977年 | 24篇 |
1976年 | 26篇 |
1975年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Arturo J. Hernndez-Maldonado Gongshin Qi Ralph T. Yang 《Applied catalysis. B, Environmental》2005,61(3-4):212-218
Monolayer CuCl/γ-Al2O3 sorbent was studied for desulfurization of a commercial jet fuel (364.3 ppmw S) and a commercial diesel (140 ppmw S). The sorbent was prepared by means of spontaneous monolayer dispersion methods. Deep desulfurization (sulfur levels of <1 ppmw) was accomplished with this sorbent using a fixed-bed adsorber. The CuCl/γ-Al2O3 sorbent was capable of removing 6.4 and 11.2 mg of sulfur per gram for jet fuel at breakthrough (at <1 ppmw S) and saturation, respectively. The same sorbent was capable of removing 0.94 and 1.8 mg of sulfur per gram for BP diesel at breakthrough and saturation, respectively. The difference in sulfur capacities for jet fuel and diesel was apparently caused by the difference in concentrations of strongly binding compounds, such as nitrogen heterocycles, heavy (polynuclear) aromatics and fuel additives. In comparison with CuCl/γ-Al2O3, Cu(I)Y zeolite has higher sulfur capacities but is less stable and can be easily oxidized to Cu(II)Y by fuel additives (such as oxygenates) and moisture and consequently loses π-complexation ability. However, all these cuprous π-complexation sorbents selectively adsorb thiophenic compounds over aromatics and olefins (as predicted by the high separation factors), which resulted in the observed desulfurization capability. A feasibility study is shown for efficient regeneration of CuCl/γ-Al2O3 using ultrasound at ambient temperature. Possible problems associated with desulfurization using π-complexation sorbents for commercial fuels are discussed. 相似文献
992.
A fall detection method based on depth image analysis is proposed in this paper. As different from the conventional methods, if the pedestrians are partially overlapped or partially occluded, the proposed method is still able to detect fall events and has the following advantages: (1) single or multiple pedestrian detection; (2) recognition of human and non-human objects; (3) compensation for illumination, which is applicable in scenarios using indoor light sources of different colors; (4) using the central line of a human silhouette to obtain the pedestrian tilt angle; and (5) avoiding misrecognition of a squat or stoop as a fall. According to the experimental results, the precision of the proposed fall detection method is 94.31% and the recall is 85.57%. The proposed method is verified to be robust and specifically suitable for applying in family homes, corridors and other public places. 相似文献
993.
采用酸溶法测定并比较几种典型的火山灰质掺合料的火山灰活性,探讨其火山灰反应程度对浆体强度的影响。试验结果表明,硅灰的火山灰活性最大,明显高于煤矸石和粉煤灰;煤矸石和Ⅱ级磨细粉煤灰的火山灰活性比Ⅰ级分选粉煤灰较大;酸溶法测定的煤矸石或硅灰的火山灰活性误差较大,活性偏低;掺合料火山灰的活性与其浆体强度有一定相关性。 相似文献
994.
介绍了第十九届中国国际塑料橡胶工业展览会(Chinaplas2005)与第八届亚太国际橡塑工业展览会(APPlas2005)展出的树脂、助剂等的新产品、新技术等。 相似文献
995.
Kaiguang Yang 《Desalination》2005,175(3):297-304
DNA-encapsulated polyethersulfone (PES) hollow microspheres are fabricated by means of a liquid-liquid phase separation technique; the hollow microspheres are then used to remove environmental pollutant organic compounds and heavy metal ions. The amounts of DNA encapsulated in the microspheres are dependent on the PES concentration, the DNA concentration used to prepare the particles, and the diameter of the syringe needle. The hollow microspheres can be used to remove harmful organic compounds including ethidium bromide (EB), acridine orange (AO) and endocrine disruptors. With the increase of the DNA amount encapsulated into the hollow microspheres, the removal ratios of these compounds increased. Additionally, the DNA-encapsulated PES hollow microspheres can selectively accumulate and remove heavy metal ions such as Ag+, Cu2+ and Zn2+ These results suggested that the DNA-encapsulated PES hollow microspheres have a potential to be used in environmental applications. 相似文献
996.
Experimental Study of an EMG-Controlled 5-DOF Anthropomorphic Prosthetic Hand for Motion Restoration
Dapeng Yang Li Jiang Qi Huang Rongqiang Liu Hong Liu 《Journal of Intelligent and Robotic Systems》2014,76(3-4):427-441
In this paper, we attempted to evaluate the performance of an electromyography (EMG)-controlled 5-DOF prosthetic hand on ten transradial amputees. The proposed prosthesis is composed of a five-fingered hand, a passive wrist, and a customized socket for each subject. The EMG control methods included both a commonly used pattern recognition-based scheme (DD-SVM) and a novel digital encoding strategy (double-channel template matching (DCTM)). A virtual 3D hand platform was developed for training the subjects and rapidly testing the control methods. For each subject, the performance of the EMG control methods was firstly measured by off-line classification accuracy; then, according to the accuracy, a particular control method was selected and embedded in the EMG controller for further validation on ordinary daily life activities. Our experiments were conducted to test not only the hand’s grasp ability but also other multifinger cooperation skills. The result indicated that the subjects of rich control experience can accomplish several intuitive motion control over their hands. However, the kinds of the motions and their relative recognition accuracy may depend on some individual differences, such as the amputation level, the activity of the residual nerve-muscle system, and the richness of control experience. Meanwhile, the proposed digital encoding method, DCTM, which only utilized two channels of EMG, was necessary for those amputees with few available control signals. This paper suggested that the EMG control method should be differently considered according to the particular condition of each subject. 相似文献
997.
Data flow acyclic directed graphs (digraph) are widely used to describe the data dependency of mesh-based scientific computing. The parallel execution of such digraphs can approximately depict the flowchart of parallel computing. During the period of parallel execution, vertex priorities are key performance factors. This paper firstly takes the distributed digraph and its resource-constrained parallel scheduling as the vertex priorities model, and then presents a new parallel algorithm for the solution of vertex priorities using the well-known technique of forward–backward iterations. Especially, in each iteration, a more efficient vertex ranking strategy is proposed. In the case of simple digraphs, both theoretical analysis and benchmarks show that the vertex priorities produced by such an algorithm will make the digraph scheduling time converge non-increasingly with the number of iterations. In other cases of non-simple digraphs, benchmarks also show that the new algorithm is superior to many traditional approaches. Embedding the new algorithm into the heuristic framework for the parallel sweeping solution of neutron transport applications, the new vertex priorities improve the performance by 20 % or so while the number of processors scales up from 32 to 2048. 相似文献
998.
Quanxi Feng Sanyang Liu Jianke Zhang Guoping Yang Longquan Yong 《Applied Intelligence》2014,41(2):563-581
Biogeography-based optimization (BBO) is a new emerging population-based algorithm that has been shown to be competitive with other evolutionary algorithms. However, there are some insufficiencies in solving complex problems, such as poor population diversity and slow convergence speed in the later stage. To overcome these shortcomings, we propose an improved BBO (IBBO) algorithm integrating a new improved migration operator, Gaussian mutation operator, and self-adaptive clear duplicate operator. The improved migration operator simultaneously adopts more information from other habitats, maintains population diversity, and preserves exploitation ability. The self-adaptive clear duplicate operator can clear duplicate or almost identical habitats, while also preserving population diversity through a self-adaptation threshold within the evolution process. Simulation results and comparisons from the experimental tests conducted on 23 benchmark functions show that IBBO achieves excellent performance in solving complex problems compared with other variants of the BBO algorithm and other evolutionary algorithms. The performance of the improved migration operator is also discussed. 相似文献
999.
Dynamic time warping (DTW) is a state-of-the-art time series similarity measure method, which warps time axes to match the same shape between two time series with different lengths. However, its quadratic time and space complexity is an obstacle to its applications in the large time series data mining. To address this problem, some lower-bound functions for DTW, fast methods to approximately measure the distance between time series, are used to prune the dissimilar objects from time series database so as to retain the candidates for further measuring their similarity with DTW. So far, the existing lower-bound functions for DTW have been widely accepted for time series similarity search and indexing. In this paper, we propose the extensions of two existing lower-bound functions and discuss the relationships among them. The extensions are improved with high tightness and without much time cost. At the same time, we theoretically prove that these extensions satisfy lower-bound requirement and are better than their old versions respectively. The experimental results demonstrate that in most cases the quality of the proposed extensions of lower-bound functions for DTW outperforms the original versions except for a slightly higher time cost. 相似文献
1000.