全文获取类型
收费全文 | 800篇 |
免费 | 36篇 |
专业分类
电工技术 | 12篇 |
化学工业 | 179篇 |
金属工艺 | 12篇 |
机械仪表 | 22篇 |
建筑科学 | 56篇 |
能源动力 | 30篇 |
轻工业 | 124篇 |
水利工程 | 13篇 |
石油天然气 | 3篇 |
无线电 | 70篇 |
一般工业技术 | 86篇 |
冶金工业 | 58篇 |
原子能技术 | 2篇 |
自动化技术 | 169篇 |
出版年
2023年 | 4篇 |
2022年 | 9篇 |
2021年 | 20篇 |
2020年 | 7篇 |
2019年 | 13篇 |
2018年 | 15篇 |
2017年 | 18篇 |
2016年 | 22篇 |
2015年 | 21篇 |
2014年 | 20篇 |
2013年 | 44篇 |
2012年 | 51篇 |
2011年 | 76篇 |
2010年 | 65篇 |
2009年 | 59篇 |
2008年 | 58篇 |
2007年 | 52篇 |
2006年 | 33篇 |
2005年 | 37篇 |
2004年 | 31篇 |
2003年 | 25篇 |
2002年 | 26篇 |
2001年 | 11篇 |
2000年 | 4篇 |
1999年 | 13篇 |
1998年 | 13篇 |
1997年 | 8篇 |
1996年 | 10篇 |
1995年 | 9篇 |
1994年 | 4篇 |
1993年 | 8篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 7篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 5篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有836条查询结果,搜索用时 218 毫秒
91.
Internal combustion engines′ fuel economy is an important role for engine designers,engine manufacturers over the past 30 years,especially passenger car motor oils.In heavy duty diesel engine,over the past 20 years,fuel economy has in some cases been sacrificed for exhaust gas emission optimizations.Now,Heavy Duty Automotive and the related industries have strong interest in fuel economy and the lubricants.It is driven by competitive market forces as well as government mandates and new emission regulations.Japan was the first country in the world to establish and implement heavy duty trucks and buses fuel economy standards.Other countries also have followed either by establishing direct fuel economy standards or greenhouse gas(GHG) emissions standards which are directly tied to fuel economy.This paper is discussing that heavy duty diesel engine lubricants can contribute on fuel economy.The contribution of various aspects of engine oil formulations on fuel economy will be discussed such as lubricant viscosity grade,lubricant additives and friction modifiers.In this paper,the evaluation discussions are based on fuel economy measurements in some bench tests,standardized laboratory engine tests and field tests. 相似文献
92.
93.
Sivakumar Palanivelu Wim Van PaepegemJoris Degrieck Bruno ReymenJean-Marie Ndambi John VantommeDimitrios Kakogiannis Jan WastielsDanny Van Hemelrijck 《Engineering Structures》2011,33(6):1966-1987
This article deals with the experimental and numerical blast study on a single empty recyclable metal beverage can. The idea is to make a macro-foam (sacrificial cladding structure) out of these cans to protect the main load bearing members of civil engineering structures from the air blast load. Close-range free air blast tests have been conducted to understand the crushing behaviour and the energy absorption of a single empty beverage can in detail. To conduct such an air blast test a special small-scale test set-up was designed and manufactured. The effect of skin plate surface area and its nature on the blast parameters is studied. Furthermore, the effect of inertia of the skin plate on the crushing performance of the beverage can is evaluated. Tests have been conducted with different plates (made of aluminium and sandwich composite materials) with different masses which represent the skin plate of the proposed sacrificial structure. The measured blast parameters from the experimental tests were compared with ConWep predicted data. Furthermore, the influence of the finite surface area of the skin plate on the clearing of the reflected pressure waves was also studied. The deformation behaviour and the corresponding energy absorption of empty beverage cans were captured. During the experimental blast tests it was observed that a part of the total reflected impulse (∼30%) was lost before it transfers to the non-sacrificial structure. Hence, in order to investigate this phenomenon Eulerian-Lagrangian coupled analyses were conducted using Hydrocodes. The results from these analyses showed that the diffraction and ground reflected pressure wave caused the loss in impulse. The results from the numerical studies have been compared and validated with the experimental results. 相似文献
94.
Successful new product development requires input from the market throughout the product development process, from identification of opportunities via screening of ideas, development of concepts, development of physical prototypes and to launch. Drawing on work done in the EU FP6 projects PROSAFEBEEF and Q-PORKCHAINS and a Danish project, all dealing with new product development in the meat sector, it is shown how the use of consumer insight techniques can a) support the identification of market opportunities, b) make sure that technologies applied are acceptable to consumers, c) aid the selection and optimisation of new product concepts and related communication, and d) be used to test product prototypes before final launch. 相似文献
95.
Stephan Schöttl Richard Rusby Henri Godfrin Matthias Meschke Valérie Goudon Sebastien Triqueneaux Andrea Peruzzi Martin J. de Groot Reyer Jochemsen Wim Bosch Yves Hermier Laurent Pitre Céline Rives Bernd Fellmuth Jost Engert 《Journal of Low Temperature Physics》2005,138(3-4):941-946
No Heading Recently, a superconductive reference device, SRD1000, with ten reference materials has been developed to enable simplified in situ calibration of interpolating thermometers. We report on the evaluation of SRD1000 prototypes at various laboratories. The devices were built and tested by HDL and KOL, calibrated at NMi-VSL and then distributed to other partners where they were re-calibrated against the local realisations of the PLTS-2000 or laboratory scales. As a result, we obtained data on the superconductive transition temperatures, widths and shapes for four different devices. Reproducibility, sharpness of the transitions, supercooling and sensitivity to magnetic fields are evaluated. This leads to estimates of the uncertainty in determination of the transition midpoint and temperature.PACS numbers: 07.20.Dt, 07.20.Mc, 74.62.–c, 74.70.Ad 相似文献
96.
G. Paul H. Van Heusden Wim J. De Koning Quirina J. M. Van Der Aart Johan A. Van Den Berg H. Yde Steensma 《Yeast (Chichester, England)》1993,9(10):1107-1110
The nucleotide sequence was determined of a 2·1 kb DNA fragment located at approximately 35 kb to the right of the centromere of chromosome VI from Saccharomyces cerevisiae. Analysis revealed the presence of a tRNAGLy gene, part of a delta element and a remarkable palindromic sequence. The longest open reading frame found encodes a putative protein of 195 amino acids. Although the fragment was isolated by hybridization to a human diacylglycerol kinase cDNA, no evidence was obtained for the presence of a gene encoding diacylglycerol kinase. 相似文献
97.
Raul Jimenez Zambrano Francisco A. Rubinelli Wim M. Arnoldbik Jatindra K. Rath Ruud E. I. Schropp 《Solar Energy Materials & Solar Cells》2004,81(1):73-86
A new band gap profile (exponential profile) for the active layer of the a-SiGe:H single junction cell has been designed and experimentally demonstrated. By computer simulations we show how bending the grading of the band gap in the i-layer contributes to the enhancement of the carrier collection, improving the fill factor and efficiency. The differences observed between experiments and simulations are studied using Rutherford Backscattering Spectrometry (RBS). The results highlight weak points during the deposition process, whose control enables us to bring together experimental and computational results. 相似文献
98.
Wim H. Hesselink 《Formal Aspects of Computing》1990,2(1):139-166
Girard's recent system of linear logic is presented in a way that avoids the two-level structure of formulae and sequents, and that minimises the number of primitive function symbols. A deduction theorem is proved concerning the classical implication as embedded in linear logic. The Hilbert-style axiomatisation is proved to be equivalent to the sequent formalism. The axiomatisation leads to a complete class of algebraic models. Various models are exhibited. On the meta-level we use Dijkstra's method of explicit equational proofs. 相似文献
99.
Wim P. Krijnen 《Computational statistics & data analysis》2006,51(2):481-489
Several models in data analysis are estimated by minimizing the objective function defined as the residual sum of squares between the model and the data. A necessary and sufficient condition for the existence of a least squares estimator is that the objective function attains its infimum at a unique point. It is shown that the objective function for Parafac-2 need not attain its infimum, and that of DEDICOM, constrained Parafac-2, and, under a weak assumption, SCA and Dynamals do attain their infimum. Furthermore, the sequence of parameter vectors, generated by an alternating least squares algorithm, converges if it decreases the objective function to its infimum which is attained at one or finitely many points. 相似文献
100.
Edward M.W. Smeets André P.C. FaaijIris M. Lewandowski Wim C. Turkenburg 《Progress in Energy and Combustion Science》2007
In this article, a model for estimating bioenergy production potentials in 2050, called the Quickscan model, is presented. In addition, a review of existing studies is carried out, using results from the Quickscan model as a starting point. The Quickscan model uses a bottom-up approach and its development is based on an evaluation of data and studies on relevant factors such as population growth, per capita food consumption and the efficiency of food production. Three types of biomass energy sources are included: dedicated bioenergy crops, agricultural and forestry residues and waste, and forest growth. The bioenergy potential in a region is limited by various factors, such as the demand for food, industrial roundwood, traditional woodfuel, and the need to maintain existing forests for the protection of biodiversity. Special attention is given to the technical potential to reduce the area of land needed for food production by increasing the efficiency of food production. Thus, only the surplus area of agricultural land is included as a source for bioenergy crop production. A reference scenario was composed to analyze the demand for food. Four levels of advancement of agricultural technology in the year 2050 were assumed that vary with respect to the efficiency of food production. Results indicated that the application of very efficient agricultural systems combined with the geographic optimization of land use patterns could reduce the area of land needed to cover the global food demand in 2050 by as much as 72% of the present area. A key factor was the area of land suitable for crop production, but that is presently used for permanent grazing. Another key factor is the efficiency of the production of animal products. The bioenergy potential on surplus agricultural land (i.e. land not needed for the production of food and feed) equaled 215–1272 EJ yr−1, depending on the level of advancement of agricultural technology. The bulk of this potential is found in South America and Caribbean (47–221 EJ yr−1), sub-Saharan Africa (31–317 EJ yr−1) and the C.I.S. and Baltic States (45–199 EJ yr−1). Also Oceania and North America had considerable potentials: 20–174 and 38–102 EJ yr−1, respectively. However, realization of these (technical) potentials requires significant increases in the efficiency of food production, whereby the most robust potential is found in the C.I.S. and Baltic States and East Europe. Existing scenario studies indicated that such increases in productivity may be unrealistically high, although these studies generally excluded the impact of large scale bioenergy crop production. The global potential of bioenergy production from agricultural and forestry residues and wastes was calculated to be 76–96 EJ yr−1 in the year 2050. The potential of bioenergy production from surplus forest growth (forest growth not required for the production of industrial roundwood and traditional woodfuel) was calculated to be 74 EJ yr−1 in the year 2050. 相似文献