全文获取类型
收费全文 | 17899篇 |
免费 | 1863篇 |
国内免费 | 2377篇 |
专业分类
电工技术 | 289篇 |
技术理论 | 2篇 |
综合类 | 829篇 |
化学工业 | 1615篇 |
金属工艺 | 3121篇 |
机械仪表 | 1221篇 |
建筑科学 | 499篇 |
矿业工程 | 1610篇 |
能源动力 | 508篇 |
轻工业 | 65篇 |
水利工程 | 47篇 |
石油天然气 | 87篇 |
武器工业 | 67篇 |
无线电 | 760篇 |
一般工业技术 | 2659篇 |
冶金工业 | 3747篇 |
原子能技术 | 48篇 |
自动化技术 | 4965篇 |
出版年
2024年 | 103篇 |
2023年 | 568篇 |
2022年 | 787篇 |
2021年 | 796篇 |
2020年 | 838篇 |
2019年 | 839篇 |
2018年 | 775篇 |
2017年 | 798篇 |
2016年 | 908篇 |
2015年 | 794篇 |
2014年 | 1107篇 |
2013年 | 1342篇 |
2012年 | 1563篇 |
2011年 | 1477篇 |
2010年 | 1144篇 |
2009年 | 1433篇 |
2008年 | 871篇 |
2007年 | 1162篇 |
2006年 | 1037篇 |
2005年 | 455篇 |
2004年 | 277篇 |
2003年 | 240篇 |
2002年 | 250篇 |
2001年 | 215篇 |
2000年 | 277篇 |
1999年 | 320篇 |
1998年 | 295篇 |
1997年 | 233篇 |
1996年 | 224篇 |
1995年 | 184篇 |
1994年 | 135篇 |
1993年 | 67篇 |
1992年 | 44篇 |
1991年 | 37篇 |
1990年 | 41篇 |
1989年 | 23篇 |
1988年 | 70篇 |
1987年 | 105篇 |
1986年 | 87篇 |
1985年 | 31篇 |
1984年 | 34篇 |
1983年 | 15篇 |
1982年 | 16篇 |
1981年 | 14篇 |
1980年 | 19篇 |
1979年 | 17篇 |
1978年 | 18篇 |
1977年 | 11篇 |
1976年 | 9篇 |
1972年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 12 毫秒
1.
调度作为计划层和执行层的纽带,是智能型工厂的主要组成部分.对此,从炼油生产装置调度的角度,对炼油调度问题进行综述与分析.首先对炼油生产调度建模问题的研究现状进行阐述,介绍目前该领域建模方面考虑的因素;其次,对炼油生产调度的各种优化方法进行总结综述;最后,结合目前的信息技术和智能制造的发展趋势,分析炼油生产调度所面临的挑战和未来的研究方向. 相似文献
2.
3.
《International Journal of Hydrogen Energy》2022,47(22):11658-11668
In an attempt to optimize the properties of FeCoNi coating for planar solid oxide fuel cell (SOFC) interconnect application, the coating composition is modified by increasing the ratio of Fe/Ni. An Fe1·5CoNi0.5 (Fe:Co:Ni = 1.5:1:0.5, atomic ratio) metallic coating is fabricated on SUS 430 stainless steel by magnetron sputtering, followed by oxidation in air at 800°C. The Fe1·5CoNi0.5 coating is thermally converted to (Fe,Co,Ni)3O4 and (Fe,Co,Mn,Ni)3O4 without (Ni,Co)O particles. After oxidation for 1680 h, no further migration of Cr is detected in the thermally converted coating region. A low oxidation rate of 5.9 × 10?14 g2 cm?4 s?1 and area specific resistance of 12.64 mΩ·cm2 is obtained for Fe1·5CoNi0.5 coated steels. 相似文献
4.
《Ceramics International》2022,48(16):23504-23509
KTaO3 and KTa0.9M0.1O3-α (M = Ti, Hf, Zr) were prepared by solid state reaction at 1330 °C for 2 h and characterized by x-ray diffraction. The AC impedance technique was used to analyze the sintered solid electrolytes in 1%H2/Ar and dry air atmosphere. Among KTa0.9M0.1O3-α (M = Ti, Hf, Zr), KTa0.9Zr0.1O3-α displays the highest conductivity in 1%H2/Ar atmosphere. The carriers transport numbers of solid electrolytes were measured by concentration cell method. The results show KTa0.9Zr0.1O3-α is a pure proton conductor below 525 °C. Stability tests show that KTa0.9Zr0.1O3-α has good chemical stability against CO2 and H2O. 相似文献
5.
Nan Wu Xiaodong Li Mu Zhang Yi Ren Qi Zhu Haijun Peng Hongqiang Ru Xudong Sun 《Journal of the European Ceramic Society》2021,41(4):2898-2907
Refining ceramic microstructures to the nanometric range to minimize light scattering provides an interesting methodology for developing novel optical ceramic materials. In this work, we reported the fabrication and properties of a new nanocomposite optical ceramic of Gd2O3-MgO. The citric acid sol-gel combustion method was adopted to fabricate Gd2O3-MgO nanocomposites with fine-grain sizes, dense microstructures and homogeneous phase domains. Nanopowders with low agglomeration and improved sinterability can be obtained by elaborating Φ values. Further refining of the microstructure of the nanocomposites was achieved by elaborating the hot-pressing conditions. The sample sintered at 65 MPa and 1300 °C showed a quite high hardness value of 14.3 ± 0.2 GPa, a high transmittance of 80.3 %–84.7 % over the 3?6 μm wavelength range, due mainly to its extremely fine-grain size of Gd2O3 and MgO (93 and 78 nm, respectively) and high density. 相似文献
6.
Dan Ye Kaiyu Wang Haijiao Yang Xingang Zhao 《International Journal of Adaptive Control and Signal Processing》2020,34(11):1677-1696
In this article, an adaptive fuzzy output feedback control method is presented for nonlinear time-delay systems with time-varying full state constraints and input saturation. To overcome the problem of time-varying constraints, the integral barrier Lyapunov functions (IBLFs) integrating with dynamic surface control (DSC) are applied for the first time to keep the state from violating constraints. The effects of unknown time delays can be removed by using designed Lyapunov-Krasovskii functions (LKFs). An auxiliary design system is introduced to solve the problem of input saturation. The unknown nonlinear functions are approximated by the fuzzy logic systems (FLS), and the unmeasured states are estimated by a designed fuzzy observer. The novel controller can guarantee that all signals remain semiglobally uniformly ultimately bounded and satisfactory tracking performance is achieved. Finally, two simulation examples illustrate the effectiveness of the presented control methods. 相似文献
7.
Requirements Engineering - In software reuse, the reuse of UML class diagram produced in design phase has received more attention due to the important influence on the following developing process.... 相似文献
8.
Although hybrid Petri net (HPN) is a popular formalism in modelling hybrid production systems, the HPN model of large scale systems gets substantially complicated for analysis and control due to large dimensionality of such systems. To overcome this problem, a typical approach is to decompose the net into subnets and then control the plant through hierarchical or decentralized structures. Although this concept has been widely discussed in the literature for discrete PNs, there is a lack of research for HPNs. In this paper, a new method of decomposition of first-order hybrid Petri nets (FOHPNs) is proposed first and then the hierarchical control of the subnets through a coordinator is introduced. The advantage of using the proposed approach is validated by an existing example. A sugar milling case study is analysed by using a decomposed FOHPN model and the optimization results are compared against the results of the approaches presented in other papers. Simulation results show not only an improvement in production rate, but also show the ability to control the plant online. In addition, by using the hierarchical control structure for an FOHPN model, it is possible to reduce the cost of communication links, improve the reliability of the system, maintain the plant locally, and partially redesign the system. 相似文献
9.
The main purpose of this paper is to survey some recent progresses on control theory for stochastic distributed parameter systems, i.e., systems governed by stochastic differential equations in infinite dimensions, typically by stochastic partial differential equations. We will explain the new phenomenon and difficulties in the study of controllability and optimal control problems for one dimensional stochastic parabolic equations and stochastic hyperbolic equations. In particular, we shall see that both the formulation of corresponding stochastic control problems and the tools to solve them may differ considerably from their deterministic/finite-dimensional counterparts. More importantly, one has to develop new tools, say, the stochastic transposition method introduced in our previous works, to solve some problems in this field. 相似文献
10.
A steelmaking-continuous casting (SCC) scheduling problem is an example of complex hybrid flow shop scheduling problem (HFSSP) with a strong industrial background. This paper investigates the SCC scheduling problem that involves controllable processing times (CPT) with multiple objectives concerning the total waiting time, earliness/tardiness and adjusting cost. The SCC scheduling problem with CPT is seldom discussed in the existing literature. This study is motivated by the practical situation of a large integrated steel company in which the just-in-time (JIT) and cost-cutting production strategy have become a significant concern. To address this complex HFSSP, the scheduling problem is decomposed into two subproblems: a parallel machine scheduling problem (PMSP) in the last stage and an HFSSP in the upstream stages. First, a hybrid differential evolution (HDE) algorithm combined with a variable neighborhood decomposition search (VNDS) is proposed for the former subproblem. Second, an iterative backward list scheduling (IBLS) algorithm is presented to solve the latter subproblem. The effectiveness of this bi-layer optimization approach is verified by computational experiments on well-designed and real-world scheduling instances. This study provides a new perspective on modeling and solving practical SCC scheduling problems. 相似文献