全文获取类型
收费全文 | 29617篇 |
免费 | 2806篇 |
国内免费 | 1925篇 |
专业分类
电工技术 | 1522篇 |
技术理论 | 1篇 |
综合类 | 3735篇 |
化学工业 | 1975篇 |
金属工艺 | 1054篇 |
机械仪表 | 1515篇 |
建筑科学 | 4102篇 |
矿业工程 | 1165篇 |
能源动力 | 653篇 |
轻工业 | 1039篇 |
水利工程 | 1246篇 |
石油天然气 | 1019篇 |
武器工业 | 210篇 |
无线电 | 2225篇 |
一般工业技术 | 2603篇 |
冶金工业 | 1475篇 |
原子能技术 | 609篇 |
自动化技术 | 8200篇 |
出版年
2024年 | 59篇 |
2023年 | 236篇 |
2022年 | 507篇 |
2021年 | 619篇 |
2020年 | 736篇 |
2019年 | 687篇 |
2018年 | 626篇 |
2017年 | 823篇 |
2016年 | 995篇 |
2015年 | 1087篇 |
2014年 | 2003篇 |
2013年 | 2001篇 |
2012年 | 2298篇 |
2011年 | 2161篇 |
2010年 | 1745篇 |
2009年 | 1976篇 |
2008年 | 1828篇 |
2007年 | 2008篇 |
2006年 | 1792篇 |
2005年 | 1576篇 |
2004年 | 1284篇 |
2003年 | 1165篇 |
2002年 | 988篇 |
2001年 | 962篇 |
2000年 | 796篇 |
1999年 | 650篇 |
1998年 | 452篇 |
1997年 | 394篇 |
1996年 | 295篇 |
1995年 | 308篇 |
1994年 | 222篇 |
1993年 | 167篇 |
1992年 | 149篇 |
1991年 | 117篇 |
1990年 | 117篇 |
1989年 | 125篇 |
1988年 | 87篇 |
1987年 | 41篇 |
1986年 | 24篇 |
1985年 | 25篇 |
1984年 | 20篇 |
1983年 | 17篇 |
1982年 | 15篇 |
1981年 | 16篇 |
1980年 | 16篇 |
1979年 | 13篇 |
1964年 | 12篇 |
1963年 | 11篇 |
1961年 | 13篇 |
1957年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
1.
Atsuki Yamaguchi Kazuki Fukui Yuki Fujiwara Shingo Tamaki Sachie Kusaka Fuminobu Sato 《Journal of Nuclear Science and Technology》2021,58(1):80-86
ABSTRACT It is important to perform neutron transport simulations with accurate nuclear data in the neutronics design of a fusion reactor. However, absolute values of large-angle scattering cross sections vary among nuclear data libraries even for well-examined nuclide of iron. Benchmark experiments focusing on large-angle scattering cross sections were thus performed to confirm the correctness of nuclear data libraries. The series benchmark experiments were performed at a DT neutron source facility, OKTAVIAN of Osaka University, Japan, by the unique experimental system established by the authors’ group, which can extract only the contribution of large-angle scattering reactions. This system consists of two shadow bars, target plate (iron), and neutron detector (niobium). Two types of shadow bars were used and four irradiations were conducted for one experiment, so that contribution of room-return neutrons was effectively removed and only large-angle scattering neutrons were extracted from the measured four Nb reaction rates. The obtained experimental results were compared with calculations for five nuclear data libraries including JENDL-4.0, JEFF.-3.3, FENDL-3.1, ENDF/B- VII, and recently released ENDF/B-VIII. It was found from the comparison that ENDF/B-VIII showed the best result, though ENDF/B-VII showed overestimation and others are in large underestimation at 14 MeV. 相似文献
2.
3.
《International Journal of Hydrogen Energy》2022,47(19):10747-10761
To obtain the mixing enhancement mechanism of H2–Water combined jets in supersonic crossflows in a combustor with expanded section for rotating detonation ramjet, the flow field shape and spray structure were studied by experimental and numerical methods. The Eulerian–Lagrangian method was used to investigate the diffusion mechanism and H2–Water interaction law of combined jets with different sequences. At the same time, high-speed photography and the schlieren technique were used to capture the flow field. The effects of jet pressure drop, orifice diameter, orifice spacing, incoming Mach number, and other parameters on the penetration depth of water jets were studied. The results of experiment and simulation show that using H2–Water combined jets, the penetration depth of the jet spray can be greatly increased and the jet mixing effect can be significantly improved, which will contribute to the engine's ignition and stable combustion. In the case of pre-water/post-H2, the penetration depth of the hydrogen jet is greater. In the case of pre-H2/post-water, the hydrogen jet raises the water spray mainly by protecting the integrity of the water column. 相似文献
4.
Redundancy allocation problem (RAP) is one of the best-developed problems in reliability engineering studies. This problem follows to optimize the reliability of a system containing s sub-systems under different constraints, including cost, weight, and volume restrictions using redundant components for each sub-system. Various solving methodologies have been used to optimize this problem, including exact, heuristic, and meta-heuristic algorithms. In this paper, an efficient multi-objective meta-heuristic algorithm based on simulated annealing (SA) is developed to solve multi-objective RAP (MORAP). This algorithm is knowledge-based archive multi-objective simulated annealing (KBAMOSA). KBAMOSA applies a memory matrix to reinforce the neighborhood structure to achieve better quality solutions. The results analysis and comparisons demonstrate the performance of the proposed algorithm for solving MORAP. 相似文献
5.
In this paper, a modified particle swarm optimization (PSO) algorithm is developed for solving multimodal function optimization problems. The difference between the proposed method and the general PSO is to split up the original single population into several subpopulations according to the order of particles. The best particle within each subpopulation is recorded and then applied into the velocity updating formula to replace the original global best particle in the whole population. To update all particles in each subpopulation, the modified velocity formula is utilized. Based on the idea of multiple subpopulations, for the multimodal function optimization the several optima including the global and local solutions may probably be found by these best particles separately. To show the efficiency of the proposed method, two kinds of function optimizations are provided, including a single modal function optimization and a complex multimodal function optimization. Simulation results will demonstrate the convergence behavior of particles by the number of iterations, and the global and local system solutions are solved by these best particles of subpopulations. 相似文献
6.
Rectangular section control technology(RSCT)was introduced to achieve high-precision profile control during silicon steel rolling.The RSCT principle and method were designed,and the whole RSCT control strategy was developed.Specifically,RSCT included roll contour design,rolling technology optimization,and control strategy development,aiming at both hot strip mills(HSMs)and cold strip mills(CSMs).Firstly,through the high-performance variable crown(HVC)work roll optimization design in the upper-stream stands and the limited shifting technology for schedule-free rolling in the downstream stands of HSMs,a hot strip with a stable crown and limited wedge,local spot,and single wave was obtained,which was suitable for cold rolling.Secondly,an approximately rectangular section was obtained by edge varying contact(EVC)work roll contour design,edge-drop setting control,and closed loop control in the upper-stream stands of CSMs.Moreover,complex-mode flatness control was realized by coordinating multiple shape-control methods in the downstream stands of CSMs.In addition,the RSCT approach was applied in several silicon-steel production plants,where an outstanding performance and remarkable economic benefits were observed. 相似文献
7.
对鞍钢股份无缝钢管厂连轧机前毛管坯横移装置存在的设计缺陷进行了分析,并提出改进方案,将原横移装置由高架轨道横移机构及上下升降链传动装置,改进为地面轨道横移系统及同步旋转臂实现取管、放管过程。实施后消除了生产故障,缩短了轧制周期,降低生产成本。 相似文献
8.
Georgios Tsaparlis 《Israel journal of chemistry》2019,59(6-7):478-492
Numerous conceptual difficulties and misconceptions have been reported in the science and chemistry education literature about electrochemistry concepts such as electrolytes, redox equations, and about electrochemical (galvanic and electrolytic) cells. Other studies have considered teaching approaches aimed at improving learning and at overcoming misconceptions. This paper reviews these studies and considers strategies and approaches for the effective teaching of electrochemistry. Then, the review focuses on problem solving in equilibrium electrochemistry, especially problems involving the Nernst equation. The main findings of four studies with Greek university chemistry students, dealing with: (i) algorithmic problem‐solving ability; (ii) practice on problem solving; (iii) the effect of the format of a problem; and (iv) the construction and evaluation of a website devoted to electrochemistry problem solving, are reported. 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.
The Vehicle Routing Problem with Simultaneous Pickup and Delivery (VRPSPD) is an extension to the classical Vehicle Routing Problem (VRP), where customers may both receive and send goods simultaneously. The Vehicle Routing Problem with Mixed Pickup and Delivery (VRPMPD) differs from the VRPSPD in that the customers may have either pickup or delivery demand. However, the solution approaches proposed for the VRPSPD can be directly applied to the VRPMPD. In this study, an adaptive local search solution approach is developed for both the VRPSPD and the VRPMPD, which hybridizes a Simulated Annealing inspired algorithm with Variable Neighborhood Descent. The algorithm uses an adaptive threshold function that makes the algorithm self-tuning. The proposed approach is tested on well-known VRPSPD and VRPMPD benchmark instances derived from the literature. The computational results indicate that the proposed algorithm is effective in solving the problems in reasonable computation time. 相似文献