全文获取类型
收费全文 | 2782篇 |
免费 | 134篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 32篇 |
化学工业 | 527篇 |
金属工艺 | 39篇 |
机械仪表 | 66篇 |
建筑科学 | 159篇 |
矿业工程 | 11篇 |
能源动力 | 150篇 |
轻工业 | 236篇 |
水利工程 | 24篇 |
石油天然气 | 2篇 |
无线电 | 246篇 |
一般工业技术 | 576篇 |
冶金工业 | 183篇 |
原子能技术 | 15篇 |
自动化技术 | 653篇 |
出版年
2024年 | 5篇 |
2023年 | 21篇 |
2022年 | 47篇 |
2021年 | 65篇 |
2020年 | 51篇 |
2019年 | 61篇 |
2018年 | 63篇 |
2017年 | 76篇 |
2016年 | 97篇 |
2015年 | 72篇 |
2014年 | 110篇 |
2013年 | 196篇 |
2012年 | 197篇 |
2011年 | 250篇 |
2010年 | 160篇 |
2009年 | 154篇 |
2008年 | 174篇 |
2007年 | 151篇 |
2006年 | 123篇 |
2005年 | 109篇 |
2004年 | 94篇 |
2003年 | 79篇 |
2002年 | 73篇 |
2001年 | 54篇 |
2000年 | 38篇 |
1999年 | 31篇 |
1998年 | 35篇 |
1997年 | 33篇 |
1996年 | 21篇 |
1995年 | 29篇 |
1994年 | 19篇 |
1993年 | 7篇 |
1992年 | 15篇 |
1991年 | 13篇 |
1990年 | 14篇 |
1989年 | 9篇 |
1988年 | 11篇 |
1987年 | 8篇 |
1986年 | 12篇 |
1985年 | 12篇 |
1984年 | 16篇 |
1983年 | 14篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1980年 | 9篇 |
1979年 | 11篇 |
1977年 | 11篇 |
1976年 | 8篇 |
1975年 | 11篇 |
1973年 | 6篇 |
排序方式: 共有2919条查询结果,搜索用时 15 毫秒
101.
当LED应用于工作照明时,其在细节方面存在一些困扰。工作照明长期以来都被人们认为是一个可以达到适当照明水平以满足个人需要和喜好的实用方法。但是,传统的工作照明解决方案常常不能完全符合各项设计标准,它仅仅是能够达到适当的照明水平而已。具体而言,传统的工作照明能源相 相似文献
102.
103.
In this article, we explore a concept-driven approach to interaction design research with a specific focus on theoretical advancements. We introduce this approach as a complementary approach to more traditional, and well-known, user-centered interaction design approaches. A concept-driven approach aims at manifesting theoretical concepts in concrete designs. A good concept design is both conceptually and historically grounded, bearing signs of the intended theoretical considerations. In the area of human–computer interaction and interaction design research, this approach has been quite popular but not necessarily explicitly recognized and developed as a proper research methodology. In this article, we demonstrate how a concept-driven approach can coexist, and be integrated with, common user-centered approaches to interaction design through the development of a model that makes explicit the existing cycle of prototyping, theory development, and user studies. We also present a set of basic principles that could constitute a foundation for concept driven interaction research, and we have considered and described the methodological implications given these principles. For the field of interaction design research we find this as an important point of departure for taking the next step toward the construction and verification of theoretical constructs that can help inform and guide future design research projects on novel interaction technologies. 相似文献
104.
K. Erik J. Olofsson Anton Soppelsa Tommaso Bolzonella Giuseppe Marchiori 《Control Engineering Practice》2013,21(7):917-929
Input–output datasets from two magnetic confinement fusion (MCF) experiments of the reversed-field pinch (RFP) type are examined. The RFP datasets, which are samples of the distributed magnetic field dynamics, are naturally divided into many smaller batches due to the pulsed-plasma operation of the experiments. The two RFP experiments considered are (i) EXTRAP T2R (T2R) with 64 inputs and 64 outputs and (ii) RFX-mod (RFX) with 192 inputs and 192 outputs. Both T2R and RFX are magnetohydrodynamically unstable and operates under magnetic feedback with optional dither injection. Using subspace system identification techniques and randomised cross-validation (CV) methods to minimise the generalisation error, state-space orders of the empirical systems are suggested. These system orders are compared to “stabilisation diagrams” commonly used in experimental modal analysis practice. The relation of the CV system order to the decay of the singular values from the subspace method is observed. Both (i) stable vacuum diffusion and (ii) unstable plasma response datasets are analysed. Apparent simulation and prediction errors are quantified for both cases using a deviation-accounted-for index. These results are purely data-driven. A simple approach towards exploitation of the subspace techniques for finite-element model refinement and data confrontation is presented. 相似文献
105.
Housing preweaned dairy calves in pairs rather than individually has been found to positively affect behavioral responses in novel social and environmental situations, but concerns have been raised that close contact among very young animals may impair their health. In previous studies, the level of social contact permitted in individual housing has been auditory, visual, or physical contact. It is unclear how these various levels of social contact compare with each other and to pair housing, when their effects on behavior and health are considered, and whether the timing of pair housing has an effect. To investigate this, 110 Holstein calves (50 males, 60 females) in 11 blocks were paired according to birth date. Within 60 h of birth, each pair of calves was allocated to 1 of 5 treatments: individual housing with auditory contact (I), individual housing with auditory and visual contact (V), individual housing with auditory, visual, and tactile contact (T), pair housing (P), or individual housing with auditory and visual contact the first 2 wk followed by pair housing (VP). At 6 wk of age, calves were subjected to a social test and a novel environment test. In the social test, all pair-housed calves (P and VP) had a shorter latency to sniff an unfamiliar calf than did individually housed calves (I, V, and T), whereas calves with physical contact (T, P, and VP) sniffed the unfamiliar calf for longer than calves on the remaining treatments (I and V). In the novel environment test, calves with physical contact (T, P, and VP) had a lower heart rate, and more of these calves vocalized during the test compared with calves without physical contact (I and V). No effect of treatment was found for clinical scores, levels of the 5 most common pathogens in feces, or in development of serum antibodies against the 3 most common respiratory pathogens. Calves housed individually are more fearful of unfamiliar calves than are pair-housed calves. Contrary to common belief, the allowance of physical contact and pair housing had no effects on the health of the calves. 相似文献
106.
Mari K. N?ss Gabriella Tranell Jan Erik Olsen Nils Eivind Kamfjord Kai Tang 《Oxidation of Metals》2012,78(3-4):239-251
During oxidative ladle refining (OLR) of silicon, the metal surface is partly oxidized, resulting in the formation of a condensed silica fume (SiO2). This fugitive emission of silica represents a potential health hazard to the workers in the silicon and ferrosilicon industry. In the current work, industrial measurement campaigns aimed at recording the fume generation during OLR were performed at the Elkem Salten plant in Norway. The measured amounts of silica produced were 2.5–5.1?kg/h, depending on the gas flow rate in the refining process. The rate of silica production correlates with the total flow rate and amount of air in the purge gas, and increases as the flow rate increases. The results of this work suggest that fume generation during OLR primarily results from oxidation of the exposed metal surface, with oxygen transport from the surrounding atmosphere to the metal surface being the limiting factor. Other identified mechanisms of SiO2 formation were splashing of the metal and/or oxidation of SiO gas carried with the refining purge gas. 相似文献
107.
Marte A. Ramírez-Ortegón Lilia L. Ramírez-Ramírez Volker Märgner Ines Ben Messaoud Erik Cuevas Raúl Rojas 《Pattern recognition》2014
In this paper, we will present a mathematical analysis of the transition proportion for the normal threshold (NorT) based on the transition method. The transition proportion is a parameter of NorT which plays an important role in the theoretical development of NorT. We will study the mathematical forms of the quadratic equation from which NorT is computed. Through this analysis, we will describe how the transition proportion affects NorT. Then, we will prove that NorT is robust to inaccurate estimations of the transition proportion. Furthermore, our analysis extends to thresholding methods that rely on Bayes rule, and it also gives the mathematical bases for potential applications of the transition proportion as a feature to estimate stroke width and detect regions of interest. In the majority of our experiments, we used a database composed of small images that were extracted from DIBCO 2009 and H-DIBCO 2010 benchmarks. However, we also report evaluations using the original (H-)DIBCO?s benchmarks. 相似文献
108.
The design of software-intensive service systems involves and affects numerous stakeholders including software engineers, legal and business experts as well as a potentially large number of consumers. In consequence, the challenge arises to adequately represent the interests of these groups with respect to service design decisions. Specifically, shared service design artifacts and participatory methods for influencing their development in consensus are required, which are not yet state of the art in software service engineering. To this end, we present service feature modeling. Using a modeling notation based on feature-oriented analysis, our approach can represent and interrelate diverse service design concerns and capture their potential combinations as service design alternatives. We further present a method that allows stakeholders to rank service design alternatives based on their preferences. The ranking can support service engineers in selecting viable alternatives for implementation. To exploit this potential, we have implemented a toolkit to enable both modeling and participative ranking of service design alternatives. It has been used to apply service feature modeling in the context of public service design and evaluate the approach in this context. 相似文献
109.
Christian Clement Yde Jeroen Jasper Jansen Peter Kappel Theil Hanne Christine Bertram Knud Erik Bach Knudsen 《European Food Research and Technology》2012,235(5):939-949
In the present study, a novel method of measuring the uptake of nutrients by 1H NMR spectroscopy was performed to determine dietary effects. Six pigs catheterized in the portal vein and mesenteric artery were fed breads made from whole-wheat grain (WWG), wheat aleurone flour (WAF; 19?% aleurone of bread) or rye aleurone flour (RAF; 15?% aleurone of bread) in a repeated 3?×?3 crossover design. Three meals were provided daily (at 0, 5 and 10?h), and each period comprised of 1?week. Portal and arterial blood samples were collected at fasting (?30?min) on day 4–7, and on day 7, pooled blood samples were collected at 0–2.5, 2.5–5, 5–7.5 and 7.5–10?h after first (0?h) daily meal. Using the arterial-venous difference and ANOVA–simultaneous component analysis, plasma betaine was found to accumulate during the experimental period. On day 7, plasma betaine concentrations was 20–40?% higher than when feeding the WAF diet compared with RAF and WWG (P?=?0.001), whereas the content of betaine in the WAF diet was about twice as high. The arterial-venous difference showed a tendency (P?=?0.078) for the diet–time interaction of betaine absorption in the absorption phases but there was no diet effect (P?=?0.31), which indicates a steady-state absorption has been reached on day 7. Furthermore, high plasma betaine levels correlated with low plasma creatine of endogenous origin. In conclusion, the explorative method revealed that the plasma concentration and absorption of betaine were differentially modified by the diets. 相似文献
110.
Erik Prins 《International journal of remote sensing》2018,39(3):854-878
Machine-learning algorithms (MLA) are coming of age within satellite remote sensing (SRS). This study compares the performance of a number of MLAs with more traditional indices and algorithms to map annual agro-pastoralist farming activity in southern Sudan. Two Landsat images from the early dry season 2014 and 2015 were analysed thoroughly and evaluated by interpretation of farming cover from very high resolution (VHR) images on Google Earth (GE). Traditional SRS indices based upon red and near infrared (NIR) bands used for monitoring rangelands did not perform well for the wet rangeland conditions compared to the use of blue and shortwave infrared (SWIR) bands. The species distribution model programme, MaxEnt, was used to produce a continuous farming activity indices using only Landsat-derived variables. Compared to other SRS classification approaches, maximum entropy (MaxEnt) showed the best overall performance to map farming activity followed by classification tree analysis (CTA). Overall mapping agreement >95.0% was reached for most methodologies, with MaxEnt showing very high mapping agreement (≥98.5%) for both years. When the result of MaxEnt’s good performance is put together in a 2014–15 or a 1999–2002 change detection scenario, it corroborates ground reports on massive human abuses that have taken place in Unity state of southern Sudan. 相似文献