全文获取类型
收费全文 | 91185篇 |
免费 | 11667篇 |
国内免费 | 7279篇 |
专业分类
电工技术 | 10658篇 |
技术理论 | 3篇 |
综合类 | 9440篇 |
化学工业 | 7115篇 |
金属工艺 | 5308篇 |
机械仪表 | 11638篇 |
建筑科学 | 4532篇 |
矿业工程 | 3463篇 |
能源动力 | 3844篇 |
轻工业 | 4734篇 |
水利工程 | 2443篇 |
石油天然气 | 4480篇 |
武器工业 | 1358篇 |
无线电 | 7061篇 |
一般工业技术 | 8079篇 |
冶金工业 | 2706篇 |
原子能技术 | 575篇 |
自动化技术 | 22694篇 |
出版年
2024年 | 719篇 |
2023年 | 1839篇 |
2022年 | 3250篇 |
2021年 | 3452篇 |
2020年 | 3878篇 |
2019年 | 3268篇 |
2018年 | 2964篇 |
2017年 | 3736篇 |
2016年 | 4117篇 |
2015年 | 4546篇 |
2014年 | 6390篇 |
2013年 | 6348篇 |
2012年 | 7144篇 |
2011年 | 7338篇 |
2010年 | 5220篇 |
2009年 | 5539篇 |
2008年 | 5057篇 |
2007年 | 5968篇 |
2006年 | 5185篇 |
2005年 | 4223篇 |
2004年 | 3500篇 |
2003年 | 2906篇 |
2002年 | 2445篇 |
2001年 | 1997篇 |
2000年 | 1699篇 |
1999年 | 1241篇 |
1998年 | 1075篇 |
1997年 | 955篇 |
1996年 | 752篇 |
1995年 | 683篇 |
1994年 | 572篇 |
1993年 | 389篇 |
1992年 | 367篇 |
1991年 | 299篇 |
1990年 | 260篇 |
1989年 | 195篇 |
1988年 | 135篇 |
1987年 | 75篇 |
1986年 | 64篇 |
1985年 | 32篇 |
1984年 | 53篇 |
1983年 | 38篇 |
1982年 | 43篇 |
1981年 | 35篇 |
1980年 | 34篇 |
1979年 | 32篇 |
1978年 | 20篇 |
1977年 | 17篇 |
1959年 | 8篇 |
1951年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
21.
本文阐述对贵冶动力车间二期反渗透进行改造的成功实践 ,主要从反渗透系统设计、反渗透系统中容易出现的问题及解决方法等进行介绍。 相似文献
22.
论述了重构轮式工程机械轮边减速器优化设计数学模型的必要性,给出了精确化的目标函数,全面化和准确化的设计变量、基于并行设计的约束条件;介绍了对优化解适用性评价的方法和手段。巧妙地解决了优化解中离散变量的圆整问题,提供了基于MATLAB的求解反渐开线函数的M文件。 相似文献
23.
In this study, crisp and fuzzy multiple-goal optimization approaches are respectively introduced to design an optimal biocompatible solvent to a two-stage extractive fermentation with cell recycling for ethanol production. When designing a biocompatible solvent for the extractive fermentation process, many issues, such as extractive efficiency, conversion, amount of solvent utilized and so on, have to be considered. An interactive multiple-goal design procedure is introduced to determine a trade-off result in order to satisfy such contradicted goals. Both approaches could be iterated to solve the interactive multiple-goal design problem in order to yield a trade-off result. However, the crisp optimization design is a tedious task that requires the designer to provide various pairs of the upper bounds for the design problem to obtain the corresponding solution. The fuzzy optimization approach is able to be trade-off several goals simultaneously and to yield the overall satisfactory grade for the product/process design problem. 相似文献
24.
Camelia Betianu Florentina A Caliman Maria Gavrilescu Igor Cretescu Corneliu Cojocaru Ioannis Poulios 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(11):1454-1465
BACKGROUND: Heterogeneous photocatalysis is influenced by a number of parameters involving synergistic effects; hence, an experimental strategy design that considers interactions between the main variables is needed. The response surface methodology was applied for the investigation of photodegradation of 20 mg L?1 Orange II in aqueous solutions and for optimization of color removal efficiency. Preliminary studies were performed to identify the parameters to be selected for optimization. RESULTS: The input variables considered for experimental design were: solution initial pH, oxidizing agent (H2O2) initial concentration and UV‐A irradiation time. The multivariate experimental design allowed the development of a quadratic response surface model to be used for the prediction of color removal efficiency over the full range of the experimental region. Under the optimum conditions established in the region of experimentation (pH = 6.9, [H2O2]0 = 183 mg L?1 and t = 32 min), a 100% color removal efficiency was obtained in experiments. CONCLUSIONS: It was found that the variables considered have important effects on color removal efficiency. The results demonstrate that the use of experimental design strategy is indispensable for successful investigation and adequate modeling of the process because the interdependence of the reaction parameters cannot be neglected. Copyright © 2008 Society of Chemical Industry 相似文献
25.
This paper presents a novel process for the fabrication of pultruded polyurethane (PU) composites. The effects of the processing parameters on the mechanical properties (flexural strength and flexural modulus, etc.) and thermal properties (HDT) of the fibre reinforced PU composites by pultrusion have been studied. The processing parameters investigated include pulling rate (in-line speed), die temperature, filler type and content, and post-cure time and temperature. Results show that the composites possessed various optimum pulling rates at different die temperatures. On the basis of the DSC diagram, the swelling ratio, the mechanical properties and the thermal properties of composites, the optimum die temperature can be determined. It is found that the mechanical and thermal properties increase with filler content for various types of filler. The mechanical and thermal properties increase at a suitable post-cure temperature and time. Furthermore, the properties which decreased due to the degradation of composite materials for a long post-cure time will be discussed. 相似文献
26.
Motonobu Yoshikawa Hiroshi Nakajima Takeshi Inada Yasushi Harada Masahiko Amano Yuji Nakata 《Electrical Engineering in Japan》1995,115(7):29-39
A new practical method is proposed which gives a quasi-optimal solution of the dynamic load-dispatching problem formulated by a multiconstraint multiobjective optimization problem. Here, the multiple constraints are rate reserve constraints and power flow ones, and the multiple objectives are fuel cost and CO2 emission. The proposed method is an integration of the following three techniques: (1) “Group Dispatch Scheme,” which is developed by the authors, is used to satisfy a violated constraint easily. This scheme consists of three steps. The first step is to classify all generators into two groups. One is the group which should be more loaded to satisfy the violated constraint, and the other is the should-be less loaded group. The second step is to add some load to the former group, and to subtract the same load from the latter. The third step is to dispatch each group load to each groups generators, respectively; (2) the dynamic load-dispatching algorithm is used which provides, in practical time, quasi-optimal generation trajectories; (3) the conventional weighting parametric method is used to obtain a Pareto optimal solution of multiobjective problems. The effectiveness of the method is clarified by a computer simulation on the actual power system of Kansai Electric Power Company. 相似文献
27.
Distortion as a result of the quenching process is predominantly due to the thermal gradient and phase transformations within
the component. Compared with traditional liquid quenching, the thermal boundary conditions during gas quenching are relatively
simple to control. By adjusting the gas-quenching furnace pressure, the flow speed, or the spray nozzle configuration, the
heat-transfer coefficients can be designed in terms of both the component geometry and the quenching time. The purpose of
this research is to apply the optimization methodology to design the gas-quenching process. The design objective is to minimize
the distortion caused by quenching. Constraints on the average surface hardness, and its distribution and residual stress
are imposed. The heat-transfer coefficients are used as design variables. DEFORM-HT is used to predict material response during
quenching. The response surface method is used to obtain the analytical models of the objective function and constraints in
terms of the design variables. Once the response surfaces of the objective and constraints are obtained, they are used to
search for the optimum heat-transfer coefficients. This process is then used instead of the finite-element analysis. A one-gear
blank case study is used to demonstrate the optimization scheme. 相似文献
28.
29.
30.
Multi-criteria ABC inventory classification (MCIC), which aims to classify inventory items by considering more than one criterion, is one of the most widely employed techniques for inventory control. This paper suggests a cross-evaluation-based weighted linear optimization (CE-WLO) model for MCIC that incorporates a cross-efficiency evaluation method into a weighted linear optimization model for finer classification (or ranking) of inventory items. The present study demonstrated the inventory-management-cost effectiveness and advantages of the proposed model using a simulation technique to conduct a comparative experiment with the previous, related investigations. We established that the proposed model enables more accurate classification of inventory items and better inventory management cost effectiveness for MCIC, specifically by mitigating the adverse effect of flexibility in the choice of weights and yielding a unique ordering of inventory items. 相似文献