全文获取类型
收费全文 | 113690篇 |
免费 | 14281篇 |
国内免费 | 8257篇 |
专业分类
电工技术 | 27240篇 |
技术理论 | 4篇 |
综合类 | 10368篇 |
化学工业 | 11925篇 |
金属工艺 | 3294篇 |
机械仪表 | 4579篇 |
建筑科学 | 6340篇 |
矿业工程 | 3421篇 |
能源动力 | 4095篇 |
轻工业 | 4157篇 |
水利工程 | 2644篇 |
石油天然气 | 4822篇 |
武器工业 | 855篇 |
无线电 | 15510篇 |
一般工业技术 | 8193篇 |
冶金工业 | 4223篇 |
原子能技术 | 1382篇 |
自动化技术 | 23176篇 |
出版年
2024年 | 574篇 |
2023年 | 1802篇 |
2022年 | 3131篇 |
2021年 | 3611篇 |
2020年 | 4042篇 |
2019年 | 3422篇 |
2018年 | 3263篇 |
2017年 | 4172篇 |
2016年 | 4473篇 |
2015年 | 4977篇 |
2014年 | 7242篇 |
2013年 | 7498篇 |
2012年 | 8464篇 |
2011年 | 9050篇 |
2010年 | 6536篇 |
2009年 | 7300篇 |
2008年 | 7032篇 |
2007年 | 7695篇 |
2006年 | 6881篇 |
2005年 | 5648篇 |
2004年 | 4743篇 |
2003年 | 4204篇 |
2002年 | 3518篇 |
2001年 | 2991篇 |
2000年 | 2544篇 |
1999年 | 2088篇 |
1998年 | 1677篇 |
1997年 | 1431篇 |
1996年 | 1180篇 |
1995年 | 1020篇 |
1994年 | 903篇 |
1993年 | 681篇 |
1992年 | 533篇 |
1991年 | 397篇 |
1990年 | 327篇 |
1989年 | 253篇 |
1988年 | 189篇 |
1987年 | 132篇 |
1986年 | 96篇 |
1985年 | 112篇 |
1984年 | 102篇 |
1983年 | 75篇 |
1982年 | 80篇 |
1981年 | 17篇 |
1980年 | 21篇 |
1979年 | 16篇 |
1978年 | 8篇 |
1976年 | 8篇 |
1959年 | 12篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
《International Journal of Hydrogen Energy》2021,46(64):32480-32489
Based on that hydrogen energy is widely used in fuel cells, we focus our interests on the design and research of new complexes that catalyze the reaction in both directions, such as hydrogen evolution reactions (HERs) and hydrogen oxidation reactions (HORs). A highly efficient catalyst for both hydrogen evolution and oxidation, based on a nickel(II) complex, [Ni-en-P2](ClO4)2, has been designed and provided by the reaction of Ni(ClO4)2 with N,N′-bis[o-(diphenylphosphino)benzylidene]ethylenediamine (en-P2) in our group. Its structure has been determined by X-ray diffraction. [Ni-en-P2](ClO4)2 can electro-catalyze hydrogen evolution both from acetic acid and a neutral buffer (pH 7.0) with a turnover frequency (TOF) of 204 and 1327 mol of hydrogen per mole of catalyst per hour (H2/mol catalyst/h) under an overpotential (OP) of 914.6 mV and 836.6 mV, respectively. [Ni-en-P2](ClO4)2 also can electro-catalyze hydrogen oxidation with a TOF of 111.7 s−1 under an OP of 330 mV. The results can be attributed to that [NiII-en-P2](ClO4)2 has three good reversible redox waves at 1.01 (NiIII/II), −0.79 (NiII/I) and −1.38 V (NiI/0) versus Fc+/0, respectively. We hope these findings can afford a new method for the design of electrocatalysts for both H2 evolution and H2 oxidation. 相似文献
53.
A number of worms, named P2P (peer-to-peer) passive worms, have recently surfaced, which propagate in P2P file-sharing networks and have posed heavy threats to these networks. In contrast to the majority of Internet worms, it is by exploiting users’ legitimate activities instead of vulnerabilities of networks in which P2P passive worms propagate. This feature evidently slows down their propagation, which results in them not attracting an adequate amount of attention in literature. Meanwhile, this feature visibly increases the difficulty of detecting them, which makes it very possible for them to become epidemic. In this paper, we propose an analytical model for P2P passive worm propagation by adopting epidemiological approaches so as to identify their behaviors and predict the tendency of their propagation accurately. Compared with a few existing models, dynamic characteristics of P2P networks are taken into account. Based on this proposed model, the sufficient condition for the global stability of the worm free equilibrium is derived by applying epidemiological theories. Large scale simulation experiments have validated both the proposed model and the condition. 相似文献
54.
This paper considers a novel distributed iterative learning consensus control algorithm based on neural networks for the control of heterogeneous nonlinear multiagent systems. The system's unknown nonlinear function is approximated by suitable neural networks; the approximation error is countered by a robust term in the control. Two types of control algorithms, both of which utilize distributed learning laws, are provided to achieve consensus. In the provided control algorithms, the desired reference is considered to be an unknown factor and then estimated using the associated learning laws. The consensus convergence is proven by the composite energy function method. A numerical simulation is ultimately presented to demonstrate the efficacy of the proposed control schemes. 相似文献
55.
Mani Balamurugan Hui‐Yun Jeong Venkata Surya Kumar Choutipalli Jung Sug Hong Hongmin Seo Natarajan Saravanan Jun Ho Jang Kang‐Gyu Lee Yoon Ho Lee Sang Won Im Venkatesan Subramanian Sun Hee Kim Ki Tae Nam 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(25)
The electrochemical reduction of carbon dioxide (CO2) to hydrocarbons is a challenging task because of the issues in controlling the efficiency and selectivity of the products. Among the various transition metals, copper has attracted attention as it yields more reduced and C2 products even while using mononuclear copper center as catalysts. In addition, it is found that reversible formation of copper nanoparticle acts as the real catalytically active site for the conversion of CO2 to reduced products. Here, it is demonstrated that the dinuclear molecular copper complex immobilized over graphitized mesoporous carbon can act as catalysts for the conversion of CO2 to hydrocarbons (methane and ethylene) up to 60%. Interestingly, high selectivity toward C2 product (40% faradaic efficiency) is achieved by a molecular complex based hybrid material from CO2 in 0.1 m KCl. In addition, the role of local pH, porous structure, and carbon support in limiting the mass transport to achieve the highly reduced products is demonstrated. Although the spectroscopic analysis of the catalysts exhibits molecular nature of the complex after 2 h bulk electrolysis, morphological study reveals that the newly generated copper cluster is the real active site during the catalytic reactions. 相似文献
56.
In this study, we have proposed an automated classification approach to identify meaningful patterns in wind field data. Utilizing an extensive simulated wind database, we have demonstrated that the proposed approach can identify low‐level jets, near‐uniform profiles, and other patterns in a reliable manner. We have studied the dependence of these wind profile patterns on locations (eg, offshore vs onshore), seasons, and diurnal cycles. Furthermore, we have found that the probability distributions of some of the patterns depend on the underlying planetary boundary layer schemes in a significant way. The future potential of the proposed approach in wind resource assessment and, more generally, in mesoscale model parameterization improvement is touched upon in this paper. 相似文献
57.
Yejun Wu Bowen Yan Juan Zhou Huizhang Lian Xiaojun Yu Jianxin Zhao Hao Zhang Wei Chen Daming Fan 《Journal of food science》2020,85(10):3282-3292
58.
《Microelectronics Journal》2015,46(11):1012-1019
This paper presents a voltage reference generator architecture and two different realizations of it that have been fabricated within a standard 0.18 μm CMOS technology. The architecture takes the advantage of utilizing a sampled-data amplifier (SDA) to optimize the power consumption. The circuits achieve output voltages on the order of 190 mV with temperature coefficients of 43 ppm/°C and 52.5 ppm/°C over the temperature range of 0 to 120°C without any trimming with a 0.8 V single supply. The power consumptions of the circuits are less then 500 nW while occupying an area of 0.2 mm2 and 0.08 mm2, respectively. 相似文献
59.
This paper addresses the multi-objective optimization problem arising in the operation of heat integrated batch plants, where makespan and utility consumption are the two conflicting objectives. A new continuous-time MILP formulation with general precedence variables is proposed to simultaneously handle decisions related to timing, product sequencing, heat exchanger matches (selected from a two-stage superstructure) and their heat loads. It features a complex set of timing constraints to synchronize heating and cooling tasks, derived from Generalized Disjunctive Programming. Through the solution of an industrial case study from a vegetable oil refinery, we show that major savings in utilities can be achieved while generating the set of Pareto optimal solutions through the ɛ-constraint method. 相似文献
60.
Lin Gao Stefano Selleri Giorgio Battistelli Luigi Chisci Giuseppe Pelosi 《国际射频与微波计算机辅助工程杂志》2020,30(9)
This paper presents a novel approach to the localization of moving targets in a complex environment based on the measurement of the perturbations induced by the target presence on an independently‐generated time‐varying electromagnetic field. Field perturbations are measured via a set of sensors deployed over the domain of interest and used to detect and track a possible target by resorting to a particle Bernoulli filter (PBF). To comply with real‐time operation, the PBF works along with an artificial neural network (ANN) model of the environment trained offline via finite elements (FEs). The performance of the proposed algorithm is assessed via simulation experiments. 相似文献