全文获取类型
收费全文 | 34811篇 |
免费 | 3687篇 |
国内免费 | 1824篇 |
专业分类
电工技术 | 2280篇 |
技术理论 | 1篇 |
综合类 | 3778篇 |
化学工业 | 2360篇 |
金属工艺 | 548篇 |
机械仪表 | 1588篇 |
建筑科学 | 7743篇 |
矿业工程 | 895篇 |
能源动力 | 998篇 |
轻工业 | 4869篇 |
水利工程 | 1040篇 |
石油天然气 | 4678篇 |
武器工业 | 310篇 |
无线电 | 1620篇 |
一般工业技术 | 3568篇 |
冶金工业 | 1242篇 |
原子能技术 | 550篇 |
自动化技术 | 2254篇 |
出版年
2024年 | 169篇 |
2023年 | 603篇 |
2022年 | 1409篇 |
2021年 | 1603篇 |
2020年 | 1575篇 |
2019年 | 1337篇 |
2018年 | 1197篇 |
2017年 | 1322篇 |
2016年 | 1443篇 |
2015年 | 1522篇 |
2014年 | 2118篇 |
2013年 | 2146篇 |
2012年 | 2953篇 |
2011年 | 3074篇 |
2010年 | 1960篇 |
2009年 | 1956篇 |
2008年 | 1728篇 |
2007年 | 1871篇 |
2006年 | 1695篇 |
2005年 | 1474篇 |
2004年 | 1154篇 |
2003年 | 1021篇 |
2002年 | 768篇 |
2001年 | 671篇 |
2000年 | 512篇 |
1999年 | 480篇 |
1998年 | 417篇 |
1997年 | 310篇 |
1996年 | 243篇 |
1995年 | 238篇 |
1994年 | 219篇 |
1993年 | 171篇 |
1992年 | 159篇 |
1991年 | 116篇 |
1990年 | 114篇 |
1989年 | 79篇 |
1988年 | 54篇 |
1987年 | 42篇 |
1986年 | 29篇 |
1985年 | 32篇 |
1984年 | 28篇 |
1983年 | 16篇 |
1982年 | 22篇 |
1980年 | 51篇 |
1979年 | 27篇 |
1965年 | 15篇 |
1964年 | 19篇 |
1963年 | 15篇 |
1959年 | 14篇 |
1957年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
961.
A multi-response robust parameter design (RPD) problem-solving technique based on desirability functions is presented in which the means and variances of all responses are placed on a level playing field. The proposal allows a decision maker to integrate their preferences for the individual means and variances. It is shown that the ensuing operating point is a system setting that produces a mutually robust set of responses. In addition, this article offers an approach to assess several RPD strategies via quality indices. The measures presented here allow for a more knowledgeable and comprehensive evaluation of the competing RPD strategies. 相似文献
962.
A new automated workflow based computationally efficient hydrologic modeling application is developed for soil moisture and runoff simulation. The spatially distributed conceptual framework underpinning the Soil Moisture And Runoff simulation Toolkit (SMART) resolves water balance in large upland catchments where topography and land cover are significant drivers of rainfall-runoff transformations. SMART's computational efficiency is achieved by delineation of contiguous and topologically connected hydrologic response units and solving the water balance equation on spatially representative Equivalent Cross-Sections (ECSs). ECSs are formulated by aggregating topographic and physiographic properties of the complete or part of the first order Strahler sub-basins, thereby reducing the number of computational elements. Water balance simulations across the ECSs in two sub-basins illustrated little loss of accuracy compared to the distributed cross section delineations and soil moisture observations. A 2-dimensional Richards' equation based hydrologic model in SMART can be augmented with additional functionalities or replaced with other model structures. 相似文献
963.
To ensure the stability of the power grid, backup capacities are called upon when electricity supply does not meet demand due to unexpected changes in the grid. As part of the demand response efforts in recent years, large electricity consumers are encouraged by financial incentives to provide such operating reserve in the form of load reduction capacities (interruptible load). However, a major challenge lies in the uncertainty that one does not know in advance when load reduction will be requested. In this work, we develop a scheduling model for continuous industrial processes providing interruptible load. An adjustable robust optimization approach, which incorporates recourse decisions using linear decision rules, is applied to model the uncertainty. The proposed model is applied to an illustrative example as well as a real-world air separation case. The results show the benefits from selling interruptible load and the value of considering recourse in the decision-making. 相似文献
964.
《Ergonomics》2012,55(7):784-789
The purpose of this study was to determine the effect of load position in an internal frame backpack on physiological and perceptual variables. Ten female participants walked on a level treadmill for 10?min carrying 25% of their body weight in a high, central, or low position. The variables measured included oxygen consumption (VO2), heart rate (HR), respiratory exchange ratio (R), respiratory rate (RR), minute ventilation (VE), and rating of perceived exertion (RPE). VO2, VE, and RPE were significantly lower in the high position (18.6?±?2.3?ml/kg/min, 31.7?±?5.0?l/min, 2.8?±?0.8, respectively) compared to the low position (22.2?±?3.0?ml/kg/min, 38.6?±?7.5?l/min, 3.7?±?1.0, respectively). HR, R, and RR did not change significantly as the load was moved from the high (129.8?±?16.8, 0.89?±?0.06, 30.3?±?4.2, respectively) to the low position (136.0?±?25.3, 0.92?±?0.04, 33.8?±?5.2, respectively). The results of this study suggest that load placement is an important factor in the physiological and perceptual responses to load carriage, and that packing heavy items high in the backpack may be the most energy efficient method of carrying a load on the back. 相似文献
965.
《Soils and Foundations》2014,54(3):250-268
This paper presents a study of the influence of frame action on the response of buildings to deformations induced by deep excavations in soft clay. Using the finite element method, a building was modelled as a framed structure adjacent to a multi-propped excavation, firstly as a frame with continuous footings and then as a frame with individual footings. The geometry, location, and structural elements forming the frame models were varied to investigate the response of various frames. Using a structural analysis, parameters representing the stiffness of the frames in reducing deflection ratios and horizontal strains were derived. The influence of the frame action on the building stiffness can be quantified using the results from the finite element models. This makes it possible to estimate building modification factors from the relevant design charts so that induced deflection ratios and horizontal strains, caused by adjacent excavation and tunnelling activities, can be calculated. The approach gives a more realistic estimate of the tensile strains for assessing the potential damage caused to buildings. 相似文献
966.
Adel Alaeddini Kai Yang Alper Murat 《Quality and Reliability Engineering International》2013,29(2):241-258
Most preset response surface methodology (RSM) designs offer ease of implementation and good performance over a wide range of process and design optimization applications. These designs often lack the ability to adapt the design on the basis of the characteristics of application and experimental space so as to reduce the number of experiments necessary. Hence, they are not cost‐effective for applications where the cost of experimentation is high or when the experimentation resources are limited. In this paper, we present an adaptive sequential response surface methodology (ASRSM) for industrial experiments with high experimentation cost, limited experimental resources, and high design optimization performance requirement. The proposed approach is a sequential adaptive experimentation approach that combines concepts from nonlinear optimization, design of experiments, and response surface optimization. The ASRSM uses the information gained from the previous experiments to design the subsequent experiment by simultaneously reducing the region of interest and identifying factor combinations for new experiments. Its major advantage is the experimentation efficiency such that for a given response target, it identifies the input factor combination (or containing region) in less number of experiments than the classical single‐shot RSM designs. Through extensive simulated experiments and real‐world case studies, we show that the proposed ASRSM method outperforms the popular central composite design method and compares favorably with optimal designs. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
967.
Crises are common in today's unpredictable environment rising the importance of crisis response strategies. Two societies in Europe are chosen: Finland, where trust in society is generalized to institutions, and Spain, where trust in society remains on the level of individuals. Using the results of the European Communication Monitor 2013 survey on crisis communication, we explored three hypotheses: “certain types of crises are often met with certain types of strategies,” “cultural context makes some crises more likely than others,” and “cultural context makes some response strategies more likely than others.” We find evidence for all three hypotheses and discuss our findings about perceived differences in the two societies. The results show that the cultural context plays an important role for crisis communication. 相似文献
968.
969.
随着智能制造时代的到来,客户对数控转塔冲床的效率要求越来越高,而提高送料的加速度和最大速度是最好的方式。一般常见冲床的加速度均为固定不变的,导致机床在运行过程中无法完全发挥其应有的特性。本文通过循序渐进的方式对加速度的智能调节技术进行了分析研究。 相似文献
970.
To the purpose of marine seismic acquisition, new acoustic sources have been developed to reduce the environmental impact. The use of marine vibrators makes it possible to define emission frequency ranges, consequently allowing limitation of the frequencies that disturb marine animal life. Constructing marine vibrators with high efficiency and linear dynamics is however difficult, and the vibrators suffer from both friction, backlash and high-order harmonics. These nonlinear effects, in combination with drifting dynamics, make the required control a crucial and challenging problem. This paper presents a model-based iterative learning control solution, performed in the frequency-domain. Additionally, an adaptive reidentification algorithm is developed to cope with drifting dynamics. The proposed solutions are successfully evaluated in experiments with a marine vibrator. 相似文献