全文获取类型
收费全文 | 1734篇 |
免费 | 121篇 |
国内免费 | 33篇 |
专业分类
电工技术 | 407篇 |
综合类 | 41篇 |
化学工业 | 184篇 |
金属工艺 | 51篇 |
机械仪表 | 37篇 |
建筑科学 | 76篇 |
矿业工程 | 15篇 |
能源动力 | 486篇 |
轻工业 | 5篇 |
水利工程 | 85篇 |
石油天然气 | 4篇 |
无线电 | 55篇 |
一般工业技术 | 155篇 |
冶金工业 | 27篇 |
原子能技术 | 20篇 |
自动化技术 | 240篇 |
出版年
2024年 | 15篇 |
2023年 | 126篇 |
2022年 | 50篇 |
2021年 | 65篇 |
2020年 | 123篇 |
2019年 | 111篇 |
2018年 | 23篇 |
2017年 | 82篇 |
2016年 | 150篇 |
2015年 | 150篇 |
2014年 | 106篇 |
2013年 | 127篇 |
2012年 | 81篇 |
2011年 | 75篇 |
2010年 | 63篇 |
2009年 | 91篇 |
2008年 | 19篇 |
2007年 | 59篇 |
2006年 | 63篇 |
2005年 | 43篇 |
2004年 | 15篇 |
2003年 | 17篇 |
2002年 | 27篇 |
2001年 | 28篇 |
2000年 | 18篇 |
1999年 | 17篇 |
1998年 | 14篇 |
1997年 | 8篇 |
1996年 | 5篇 |
1995年 | 7篇 |
1994年 | 7篇 |
1993年 | 14篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 6篇 |
1989年 | 1篇 |
1988年 | 11篇 |
1987年 | 27篇 |
1986年 | 19篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1976年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有1888条查询结果,搜索用时 15 毫秒
51.
This paper proposes a practical formulation for the non-convex economic dispatch problem to consider multi-fuel options, ramp rate limits, valve loading effect, prohibited operating zones and spinning reserve. A new optimization algorithm based on the θ-bat algorithm (θ-BA) is suggested to solve the problem. The θ-BA converts the Cartesian search space into the polar coordinates such that more search ability would be achieved. According to the complex, nonlinear, and constrained nature of the problem, a new self-adaptive modification method is proposed. The proposed modified θ-BA (θ-MBA) is constructed based on the roulette wheel mechanism to effectively increase the convergence of the algorithm. The high ability and satisfying performance of the proposed optimization method is examined on IEEE 15-unit, 40-unit and 100-unit test systems. 相似文献
52.
Candida Antarctica lipase B (CALB), a specific enzyme to catalyze the hydrolysis of esters, can be a good candidate for acetylcholine (ACh) hydrolysis instead of acetylcholinesterase. The catalytic mechanism of the CALB acylation, as the first stage in the hydrolysis reaction, with ACh and methylcaprylate (MEC) has been examined by using density functional theory technique. The significant emphasis of this article is on the free energy barriers for the acylation step of hydrolysis reactions. Computed free energy barriers of the first step are 9.2 and 15.9 kcal mol−1, but for the second step are 7.9 and 11.6 kcal mol−1 for MEC and ACh respectively. Activation free energies are in the comparable and acceptable range and imply both of two reactions are theoretically possible. The stability role of the adjacent amino acids was examined by using two applied tools. It is exposed that the oxyanion hole residues decrease energy barriers by stabilizing the transition state structures. 相似文献
53.
In this paper, a novel sequential scenario reduction framework for general optimization problem is proposed. The proposed method extends the previous work (Li and Floudas, 2014) and aims to tackle optimization problems with a large number of uncertain parameters and a huge number of scenarios generated from the factorial combination. The proposed method first ranks the uncertain parameters based on their effects on the optimal objective using global sensitivity analysis. Then, the parameters are sequentially considered in generating uncertainty scenarios. This method can essentially reduce the computational efforts needed for evaluating the objective values of all scenarios, which is often impractical for a huge number of scenarios. Criteria for quantifying the quality of scenario reduction are also proposed based on robust optimization and scenario optimization. Case studies are presented to illustrate the sequential scenario reduction framework and the results verify the efficiency of the proposed approach. 相似文献
54.
《低温学》2016
A centrifugal cryogenic pump has been designed at Argonne National Laboratory to circulate liquid nitrogen (LN2) in a closed circuit allowing the recovery of excess fluid. The pump can circulate LN2 at rates of 2–10 L/min, into a head of 0.5–3 m. Over four years of laboratory use the pump has proven capable of operating continuously for 50–100 days without maintenance. 相似文献
55.
The use of process bus modern technology in accordance with the IEC 61850 protocol allows performing modern measurement and improving the protection automation system. It also allows for the integration and complex building of functional automation and control systems based on network devices in Ethernet technology. The paper presents measuring tests of a process bus equipment and the operation of protection functions based on measurements. 相似文献
56.
Fatigue crack growth thresholds ΔKth were determined for friction stir welded butt joints made from aluminium alloys AA2024 and AA6013. Plotting the thresholds as a function of load ratio R showed distinctly higher amounts for welded joints as compared to those for parent material at small load ratios, but differences became smaller with increasing load ratio, until thresholds became finally identical for the highest R values. Applying Döker’s concept of two controlling parameters, namely ΔK and Kmax [1], and plotting ΔKth versus Kmax, however, revealed that the effective threshold ΔKth,eff determined at very high R ratios was nearly independent on the alloy and, simultaneously, was identical for parent material and respective welded joints. Thus, differences in threshold behaviour were only caused by the second threshold Kmax,th, which was significantly higher for welded joints as compared to parent material. Differences in Kmax,th coincided with compressive residual stresses determined by cut-compliance measurements in terms of stress intensity factors Krs acting at the crack tip. Based on the analytical approach described by Döker [1], only one characteristic Krs value was needed to calculate all thresholds of welded joints for 0 ⩽ R ⩽ 1 provided a base material master curve is available. 相似文献
57.
The doubly fed induction generator based wind turbine (DFIG-WT) has strong nonlinearities originated from the aerodynamics of the wind turbine and the coupled dynamic of the DFIG, and can operate under a time-varying and wide operation region. This paper investigates a feedback linearisation controller based on the detailed model of the DFIG-WT, the control objective is to maximize energy conversion for this system. The original nonlinear system is partially linearized to a third-order linear system and a remained second-order internal nonlinear system. Fully decoupled control of the external dynamics is achieved, and the stability of the remained internal dynamics is analyzed via Lyapunov stability method. Moreover, modal analysis is applied for the nonlinear system controlled by the proposed nonlinear controller to verify its global optimal performance and low-voltage ride-through (LVRT) capability over various wind operation range. Simulation studies verify that more accurate tracking and better LVRT capability can be achieved in comparison with conventional vector control (VC). 相似文献
58.
Cluster ensembles have been shown to be better than any standard clustering algorithm at improving accuracy and robustness across different data collections. This meta-learning formalism also helps users to overcome the dilemma of selecting an appropriate technique and the corresponding parameters, given a set of data to be investigated. Almost two decades after the first publication of a kind, the method has proven effective for many problem domains, especially microarray data analysis and its down-streaming applications. Recently, it has been greatly extended both in terms of theoretical modelling and deployment to problem solving. The survey attempts to match this emerging attention with the provision of fundamental basis and theoretical details of state-of-the-art methods found in the present literature. It yields the ranges of ensemble generation strategies, summarization and representation of ensemble members, as well as the topic of consensus clustering. This review also includes different applications and extensions of cluster ensemble, with several research issues and challenges being highlighted. 相似文献
59.
In 2013, the feed-in tariff (FIT) policy was issued in China to promote the investment in renewable technology, but then it was revised because this policy brought a heavy financial burden to the government. By considering the intermittence of renewable resources, we model the implemented Chinese FIT policies and analyze their impact on renewable energy investment in the power market. The open-loop model is employed to simulate the China's power market organized with Power Purchase Agreement, and the closed-loop game is used to characterize the spot power market. Meanwhile, the strategic capacity choices of power generators in two games are compared under four different policy schemes: (i) free competition, (ii) FIT via fixed subsidy, (iii) FIT via price premium and (iv) Chinese FIT by cross control (CFCC). The results show that the CFCC policy is a good alternative to well control the investment in renewable technology, as it can be seen as a comprise between free competition and FIT via fixed subsidy policy. Furthermore, compared with the other three policy schemes, the CFCC policy is capable of keeping renewable power generators from deviating the equilibrium, which implies higher robustness in regulating the electricity spot market. 相似文献
60.
Dry torrefaction and hydrothermal carbonization (HTC) are two thermal pretreatment processes for making homogenized, carbon rich, hydrophobic, and energy dense solid fuel from lignocellulosic biomass. Pellets made from torrefied biochar have poor durability compared to pellets of raw biomass. Durability, mass density, and energy density of torrefied biochar pellets decrease with increasing dry torrefaction temperature. Durable pellets of torrefied biochar may be engineered for high durability using HTC biochar as a binder. In this study, biomass dry torrefied for 1 h at 250, 275, 300, and 350 °C was pelletized with various proportions of biomass HTC treated at 260 °C for 5 min. During the pelletization of biochar blends, HTC biochar fills the void spaces and makes solid bridges between torrefied biochar particles, thus increasing the durability of the blended pellets. The engineered pellets' durability is increased with increasing HTC biochar fraction. For instance, engineered pellets of 90% Dry 300 and 10% HTC 260 are 82.5% durable, which is 33% more durable than 100% Dry 300 biochar pellets, and also have 7% higher energy density than 100% Dry 300 biochar pellets. 相似文献