全文获取类型
收费全文 | 135226篇 |
免费 | 8948篇 |
国内免费 | 4462篇 |
专业分类
电工技术 | 7200篇 |
技术理论 | 7篇 |
综合类 | 12109篇 |
化学工业 | 9157篇 |
金属工艺 | 5315篇 |
机械仪表 | 14588篇 |
建筑科学 | 28563篇 |
矿业工程 | 3982篇 |
能源动力 | 2985篇 |
轻工业 | 5022篇 |
水利工程 | 3647篇 |
石油天然气 | 4127篇 |
武器工业 | 1509篇 |
无线电 | 10577篇 |
一般工业技术 | 13013篇 |
冶金工业 | 2924篇 |
原子能技术 | 683篇 |
自动化技术 | 23228篇 |
出版年
2024年 | 243篇 |
2023年 | 1240篇 |
2022年 | 2021篇 |
2021年 | 2730篇 |
2020年 | 2971篇 |
2019年 | 2296篇 |
2018年 | 2302篇 |
2017年 | 2931篇 |
2016年 | 3408篇 |
2015年 | 3809篇 |
2014年 | 9672篇 |
2013年 | 7707篇 |
2012年 | 9785篇 |
2011年 | 10493篇 |
2010年 | 8944篇 |
2009年 | 9197篇 |
2008年 | 8445篇 |
2007年 | 10134篇 |
2006年 | 8383篇 |
2005年 | 7495篇 |
2004年 | 6013篇 |
2003年 | 5641篇 |
2002年 | 4443篇 |
2001年 | 3681篇 |
2000年 | 2968篇 |
1999年 | 2284篇 |
1998年 | 1822篇 |
1997年 | 1505篇 |
1996年 | 1284篇 |
1995年 | 1050篇 |
1994年 | 829篇 |
1993年 | 592篇 |
1992年 | 461篇 |
1991年 | 380篇 |
1990年 | 244篇 |
1989年 | 243篇 |
1988年 | 185篇 |
1987年 | 138篇 |
1986年 | 82篇 |
1985年 | 95篇 |
1984年 | 124篇 |
1983年 | 83篇 |
1982年 | 95篇 |
1981年 | 32篇 |
1980年 | 35篇 |
1979年 | 27篇 |
1978年 | 13篇 |
1977年 | 11篇 |
1959年 | 11篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
Victoria R.C. Sieck Fletcher G.W. Christensen 《Quality and Reliability Engineering International》2021,37(7):3018-3033
When developing a product, it is important to consider product performance from a user perspective. This type of evaluation can be done through operational testing—assessing the ability of representative users to satisfactorily accomplish tasks with the product in operationally representative environments. This process can be expensive and time-consuming, but is critical to understanding whether the product can adequately do the job for which it was designed. We show how an existing design of experiments (DOEs) process for operational testing can be leveraged to construct a Bayesian adaptive design. This design, nested within the larger design created by the DOE process, allows interim analyses to stop testing early for success or futility. Representative simulations are presented to demonstrate how these interim analyses can be used in an operational test setting, and reductions in necessary test events are shown. The application of Bayesian-adaptive design methods will allow future operational testing to be conducted in less time and at less expense, on average, without compromising the ability of the existing process to verify the product meets the user's needs. 相似文献
82.
The consumption of healthful foods is relevant for the well-being of society. However, understanding healthfulness may be difficult because, in some cultures (i.e., the U.S.), individuals assume that unhealthy equals tasty, an association that does not hold in other contexts (i.e., France). Auditory cues could serve to inform consumers about the expected experience with food and thus could signal the sensory experience of a healthy product. This research contributes to the literature on the use of sound symbolism for analysis of the influence of onomatopoeias as packaging information that influences the expected healthfulness of a bottled drink. The study is a 4 × 4 mixed-model experiment. Grouping was done according to onomatopoeia variables as follows: “Fizz,” “Glup,” “Ahhh,” and control. Beverage color, a within-subject variable, was grouped as green, yellow, red, and control. Results show that the healthful concept is defined in two dimensions: fulfilling and light. Onomatopoeias motivated the experience of a less fulfilling beverage, which had the strongest effect on “Fizz” condition. For the light dimension, “Ahhh” diminishes the perception of light, thus creating the idea that the drink is high in calories. This study reaches out to food industries on the need to find the most consistent and pleasurable sound associated with their products. This will enable food industries to provide information to consumers as well as ascertain how much they enjoy the product. 相似文献
83.
Guilherme Pepplow Piuzzi Hugo Carlos Scheuermann Filho Joe Arnaldo Villena Del Carpio Nilo Cesar Consoli 《Geotextiles and Geomembranes》2021,49(3):864-870
Asphalt concrete is the prevailing material used for road surface construction. Its adequate characteristics in providing stability, durability and driving safety are controlled by complex interactions between its components. Thus, it is important to estimate the sensitivity of asphalt concrete mechanical properties as a function of its volumetrics. For this study, different combinations between asphalt content (3.5, 5 and 7.5%) and porosity values (above 4%) were used in order to disassociate these properties. The influence of mixing in fiberglass (0.5%) was also analyzed. It was found that porosity is significantly more relevant than the asphalt content in the prediction of tensile strength and resilient modulus of fiber-free asphalt concretes. In fiber-reinforced mixtures, the mechanical properties are improved by increasing the asphalt content, which suggests a better bonding between fibers and aggregates. For both cases, decreasing porosity is beneficial. By grouping both sets of results, it was possible to create a unique theoretical curve for both the tensile strength (qt) and the resilient modulus (RM). The RM/qt ratio was 5800 for the fiber-free group, and 3900 for the fiber-reinforced group - suggesting a better fatigue life indicator for asphalt concretes when fibers are added. 相似文献
84.
The colour of the background on which products are presented may affect their perceived attractiveness. In order to find out on which type of background various fresh food products look most attractive, we presented five different vegetables (tomato, carrot, yellow bell pepper, eggplant, mushroom) on five different backgrounds with neutral grey colours varying in degree of blackness: 5, 30, 50, 65, and 90%. Forty-six participants provided colour matches for the vegetables and evaluated them on 10 attributes.Overall, the blackness of the backgrounds had little or no effect on the perceived colour of the vegetable. Only for carrots we found a small but significant difference, mainly between the 5% and 90% blackness backgrounds. On the darkest background, the carrot would be perceived as a bit lighter, more saturated, and more yellow rather than red, compared to the lightest background.Differences in perceived attractiveness on the grey backgrounds varied between 0.3 and 1.0 units on a 9-point scale. Attractiveness and expensiveness ratings for most vegetables were highest on the 90% blackness background. In comparison to our previous study where we presented vegetables on hued backgrounds, differences between mean attractiveness ratings were smaller. Because mean attractiveness ratings in the current study were higher, we expect that grey backgrounds are more likely to present vegetable assortments with a variety of hues in an attractive way than hued backgrounds. 相似文献
85.
针对高速率通信网络和Round-Robin(RR)协议影响下网络化时变系统的有限时域[H∞]控制问题,考虑到系统中存在乘性噪声、随机时滞和量化效应,提出了一种基于观测器的有限时域[H∞]控制器的设计方法。利用李雅普诺夫稳定性理论和线性矩阵不等式(Linear Matrix Inequality,LMI)技术得到有限时域[H∞]控制器存在的充分条件。基于锥补线性化(Cone Complementarity Linearization,CCL)方法通过求解一组递归矩阵不等式得到观测器和控制器参数。所设计的控制器保证闭环网络化时变系统在给定的时域内稳定,且满足预定的[H∞]性能指标。数值仿真验证了所提方法的有效性。 相似文献
86.
Joseph O'Donnell Pierre-André Cazade Sarah Guerin Ahmed Djeghader Ehtsham Ul Haq Kai Tao Ehud Gazit Eiichi Fukada Christophe Silien Tewfik Soulimane Damien Thompson Syed A. M. Tofail 《Advanced functional materials》2021,31(28):2100884
Controlling the electromechanical response of piezoelectric biological structures including tissues, peptides, and amino acids provides new applications for biocompatible, sustainable materials in electronics and medicine. Here, the piezoelectric effect is revealed in another class of biological materials, with robust longitudinal and shear piezoelectricity measured in single crystals of the transmembrane protein ba3 cytochrome c oxidase from Thermus thermophilus. The experimental findings from piezoresponse force microscopy are substantiated using a range of control measurements and molecular models. The observed longitudinal and shear piezoelectric responses of ≈ 2 and 8 pm V−1, respectively, are comparable to or exceed the performance of commonly used inorganic piezoelectric materials including quartz, aluminum nitride, and zinc oxide. This suggests that transmembrane proteins may provide, in addition to physiological energy transduction, technologically useful piezoelectric material derived entirely from nature. Membrane proteins could extend the range of rationally designed biopiezoelectric materials far beyond the minimalistic peptide motifs currently used in miniaturized energy harvesters, and the finding of robust piezoelectric response in a transmembrane protein also raises fundamental questions regarding the molecular evolution, activation, and role of regulatory proteins in the cellular nanomachinery, indicating that piezoelectricity might be important for fundamental physiological processes. 相似文献
87.
The sintering behavior of WC-Ni nanocomposite powder was evaluated through experimental and statistical approaches to study the contribution of involving parameters of chemical composition (Ni wt. %) and sintering temperature on sinterability of system by assessing the resulted densification and microhardness. The experimental process was designed based on factorial experimental design for independent effective parameters of Ni percentage (12, 18 and 23 wt %), and sintering temperature (8 different values within 1350–1485 °C). The resulted products of experimental testing after compaction and sintering were analyzed by FESEM and EDX to image the microstructure and evaluate the chemical composition and elemental distribution. The density and microhardness were measured as well. An artificial neural network (ANN) was applied to describe the corresponding individual and mutual impacts on sintering. The ANN model was developed by feed-forward back propagation network including topology 2:5:2 and trainlm algorithm to model and predict density and microhardness. A great agreement was observed between the predicted values by the ANN model and the experimental data for density and microhardness (regression coefficients (R2) of 0.9983 and 0.9924 for target functions of relative density and microhardness, respectively). Results showed that the relative importance of operating parameters on target functions (relative density and microhardness) was found to be 62% and 38% for sintering temperature and Ni percentage, respectively. Also, ANN model exhibited relatively high predictive ability and accuracy in describing nonlinear behavior of the sintering of WC-Ni nanocomposite powder. The experimental results confirmed that the appropriate sintering temperature was influenced by Ni content. The optimum parameters were found to be 12 wt % Ni sintered at 1460 °C with the highest microhardness and relative density. 相似文献
88.
目的针对社会文创设计出现的两种典型误区,以敦煌莫高窟第61窟女供养人文创设计为例进行设计研究实践,梳理出传统视觉形象的研究方法和创新设计方法,以此传承和保护中国传统文化。方法采用“图解法”对莫高窟第61窟东壁南侧女供养人的人物身份、妆容、发饰、服饰、色彩、局部等进行深入剖析,并将其作为文创衍生设计的根本来源,总结适用于当今社会的传统文化视觉元素创新设计方法,实现以传统文化为本源、艺术设计为手段、文创设计为载体的传统文化现代设计转译。结论依据“图解法”完成文创衍生设计,实现传统文化与现代设计的深度融合,有助于为不同传统文化题材的文创设计提供借鉴之意。 相似文献
89.
《Calphad》2021
Heat capacity data for compounds located in the binary CaO–SiO2, CaO–Al2O3 and MgO–Al2O3 systems are fitted by Debye-Einstein integrals. Starting from the fitted heat capacities, the standard values of the thermodynamic functions of these compounds are calculated. In almost all cases investigated, the derived standard entropies are within the uncertainties of the values provided in literature. The Debye-Einstein coefficients obtained in this thermodynamic assessment can be used to approximate the heat capacities, enthalpies and entropies of these compounds in the temperature range from 0 to 298.15 K. 相似文献
90.
This study proposes a multiperiod mixed integer linear programming model for the management of a single municipal solid waste (MSW) treatment plant with sustainability as the objective. Discrete and continuous variables define the capacity selections for diverse MSW technologies, and the operation of the MSW network, respectively. The economic target is considered to maximize the net present value. The environmental impact is the minimization of a normalized environmental objective function (NEOF). The social target is the maximization of jobs. An interesting feature about the research work is the requirement of biodrying technologies for MSW moisture content control. Due to the conflicted nature among the sustainability components, a multiobjective optimization (MO) is carried out to find the Pareto optimal solutions. The MO results show that the Pareto optimal solutions vary around profit range of $4.9–8.5 billion, NEOF impact range of 3.2–3.6 units, and social benefit range of 2700–4828 jobs. 相似文献