全文获取类型
收费全文 | 747篇 |
免费 | 18篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 4篇 |
化学工业 | 174篇 |
金属工艺 | 78篇 |
机械仪表 | 10篇 |
建筑科学 | 46篇 |
矿业工程 | 1篇 |
能源动力 | 15篇 |
轻工业 | 101篇 |
水利工程 | 1篇 |
石油天然气 | 11篇 |
无线电 | 19篇 |
一般工业技术 | 130篇 |
冶金工业 | 108篇 |
自动化技术 | 69篇 |
出版年
2023年 | 5篇 |
2022年 | 18篇 |
2021年 | 16篇 |
2020年 | 18篇 |
2019年 | 15篇 |
2018年 | 20篇 |
2017年 | 12篇 |
2016年 | 18篇 |
2015年 | 14篇 |
2014年 | 23篇 |
2013年 | 40篇 |
2012年 | 27篇 |
2011年 | 41篇 |
2010年 | 35篇 |
2009年 | 46篇 |
2008年 | 36篇 |
2007年 | 34篇 |
2006年 | 21篇 |
2005年 | 16篇 |
2004年 | 25篇 |
2003年 | 23篇 |
2002年 | 17篇 |
2001年 | 15篇 |
2000年 | 15篇 |
1999年 | 12篇 |
1998年 | 15篇 |
1997年 | 9篇 |
1996年 | 14篇 |
1995年 | 5篇 |
1994年 | 15篇 |
1993年 | 10篇 |
1992年 | 6篇 |
1991年 | 11篇 |
1990年 | 8篇 |
1989年 | 12篇 |
1988年 | 8篇 |
1987年 | 10篇 |
1985年 | 7篇 |
1983年 | 4篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1973年 | 3篇 |
1972年 | 3篇 |
1971年 | 5篇 |
1970年 | 3篇 |
1969年 | 3篇 |
1944年 | 3篇 |
1943年 | 4篇 |
排序方式: 共有767条查询结果,搜索用时 10 毫秒
51.
Juan Alcalde Mansour Edraki Oscar Jerez Ursula Kelm David A. Rubinos 《Mine Water and the Environment》2020,39(1):135-149
An exploratory study demonstrated that subtle changes in solids and process water were caused by long-distance turbulent transport of tailings from the concentrator to the impoundment of a Cu (Mo) porphyry copper deposit. Slurry water chemical analysis was complemented by modelling potential phase precipitation or dissolution and speciation of dissolved metals. It was found that transport did not affect major insoluble mineral phases. However, the degrees of liberation of several phyllosilicates, as determined by automated mineralogy, were reduced close to the impoundment, which points to separation of clay particles from tectosilicate surfaces by the turbulence; this also was observed by SEM examination of micro-aggregate specimens. Reduction of maximum particle sizes, increased N2 monolayer adsorption, and resultant specific surface areas indicate that transport modified the micro-aggregates. Major element water chemistry is controlled by the presence of soluble mineral phases, such as gypsum, and reagents, such as lime, in the flotation process. Changes in the dissolved concentrations of some elements could potentially affect tailings deportment in the impoundment. Increased concentrations of Al may affect the clay settling behaviour, while Mo and As levels will require treatment prior to the discharge of water from the tailings impoundment. This study demonstrated that systematic scrutiny of tailings slurries leaving the concentrator and before entering the impoundment can be potentially useful, though care will have to be exercised to replicate sample handling and analytical conditions, during any long-term monitoring. 相似文献
52.
Jana Velde Ursula Kowalsky Tim Zümendorf Dieter Dinkler 《Computational Materials Science》2009,46(2):352-357
In order to describe the time-dependent inelastic behavior of steel structures up to failure, a material model is developed within the framework of thermodynamics considering viscoplastic material behavior, isotropic hardening, softening, and isotropic ductile damage. Since softening and damage lead to localization of deformations, the model is extended by a non-local implicit gradient formulation. An additional gradient equation is formulated for the local damage variable in order to achieve results independent of the finite-element discretization. The approach is verified by 3D-structural analysis of CT-specimens. 相似文献
53.
Laughing at oneself is considered a core component of the sense of humor in the theories of several authors. In McGhee's (1996) eight-step-training program of the sense of humor, laughing at oneself constitutes one of the most difficult levels. However, until now, only little empirical evidence on laughing at oneself exists. Using a multimethod approach, in the current study, 70 psychology students and a total of 126 peers filled in the Sense of Humor Scale (SHS, McGhee, 1996), containing as a subscale “Laughing at oneself”. In addition, the participants answered the Trait and State forms of the State-Trait-Cheerfulness-Inventory (STCI, Ruch, K?hler, & van Thriel, 1996; Ruch, K?hler, & van Thriel, 1997). They then were confronted with six distorted images of themselves. Facial responses of the participants were videotaped and analyzed using the Facial Action Coding System (FACS, Ekman, Friesen, & Hager, 2002). Four indicators of exhilaration were examined: (a) experienced funniness, (b) AU12 smiles, (c) Duchenne displays, and (d) laughter. Furthermore, fake and masking smiles were studied. Results demonstrated that self- and peer reports of “laughing at oneself” converged moderately. All four indicators of exhilaration were shown, but funniness and laughter seemed to be the most strongly related indicators. Trait cheerfulness and (low) seriousness, and a cheerful mood state formed further characteristics of persons who laugh at themselves. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
54.
A. M. Al-Mukhtar H. Biermann P. Hübner S. Henkel 《Journal of Materials Engineering and Performance》2010,19(9):1225-1234
In this work, the parameters stress intensity factor (SIF), initial and final crack lengths (a
i and a
f), crack growth parameters (C and m), and fatigue strength (FAT) are investigated. The determination of initial crack length seems to be the most serious factor
in fatigue life and strength calculations for welded joints. A fracture mechanics approach was used in these calculations
based on SIF which was calculated with the finite element method (FEM). The weld toe crack was determined to be equal to 0.1 mm,
whereas the weld root crack’s length was varied depending on the degree of the weld penetration. These initial crack length
values are applicable for all types of joints which have the same crack phenomenon. As based on the above calculated parameters,
the new limits of FAT for new geometries which are not listed yet in recommendations can be calculated according to the current
approach. 相似文献
55.
The choice of statistical distributions characterising microbial counts is essential in risk assessment and risk management. While the lognormal distribution has been long used to directly model the microbial data obtained from food samples, it does not allow for complete absence of microorganisms in a sample. Within a heterogeneous Poisson theoretical interpretation, a gamma or a lognormal population distribution for the unknown microbial concentration and a Poisson measurement distribution produces a discrete Poisson-gamma (λ, 1/k) or a Poisson-lognormal (μ,σ) distribution of observed plate counts. The capability of both distributions to deal with clustering was compared using six data sets of variable proportion of zero counts: total viable counts, coliforms and Escherichia coli on pre-chill and post-chill beef carcasses. Whereas the Poisson-lognormal distribution fitted better to the high counts data sets, the Poisson-gamma distribution represented the low counts data sets (13–81% zero counts) by far better than the Poisson-lognormal – which invariably tended to have a longer tail, an overestimated mean log and a lower predicted probability of zero counts. The inverse close relationship between the observed proportion of zero counts in the data set and the fitted dispersion factor 1/k suggested the possibility of obtaining a first approximation of 1/k by this means. Finally, in absence of zero counts, it was demonstrated that fitting a Poisson-lognormal to the observed plate count data can be closely approximated by the common practice of fitting a simple normal distribution to the back-calculated ‘unobserved’ mean concentrations in log CFU/g. 相似文献
56.
Stefan Kwiatkowski Ursula Thielen Phyllis Glenney Colm Moran 《Journal of the Institute of Brewing》2009,115(2):151-158
Much research has been carried out over the years examining cell wall glucans from Saccharomyces cerevisiae and this study further examines aspects of the binding of (1r?4)‐α‐D‐glucan in the yeast cell wall, using a number of isolation techniques as well as monoclonal antibodies able to recognize a mixed (1r?4)‐α‐D‐glucan/(1r?6)‐β‐D‐glucan. Extraction of purified glucan, from S. cerevisiae cell wall, with 0.1N HCl, at 80°C for 6 h, released into the solution (1r?4)‐α‐D‐glucan and (1r?6)‐β‐D‐glucan as the major polysaccharides, along with an insoluble pellet highly enriched in (1r?3)‐β‐D‐glucan. The released (1r?4)‐α‐D‐glucan was composed of a high molecular size >100 kDa fraction (7.2% w/w) and a medium 5–50 kDa polysaccharide (10.2% w/w), with the (1r?4)‐α‐D‐glucan covalently bound to the (1r?6)‐β‐D‐glucan. The average molar ratio of the α:β glucan was 47: 53 in this mixed polysaccharide. The structure of this polysaccharide was different from the structure of plant starch or animal glycogen as monoclonal antibodies specific to yeast (1r?4)‐α‐D‐glucan/(1r?6)‐β‐D‐glucan did not recognize the plant starch or animal glycogen standards. 相似文献
57.
本文介绍了新一代IHM.B具备更强机械性能的高功率IGBT模块,其融合了最新的设计、材料、焊接和安装技术。首批IHMB模块将搭载最新的、采用沟槽栅单元设计的3.3kV IGBT3芯片,在保持机械兼容性的同时,极大地提高了器件的热效率和电气效率。本文还对宇宙射线以及功率循环试验进行了研究。 相似文献
58.
Observed 72 infants aged 12, 18, and 24 mo in the presence of their mothers and 2 adult female strangers to assess their willingness to initiate proximal interaction (PI) with unfamiliar adults. Mothers and strangers were asked to be warmly responsive to infant overtures but not to invite interaction from the infant. A majority of the infants at the 3 ages initiated PI with one or both strangers, often repeatedly. For those who engaged in 2 or more PI bouts with the strangers, a significant upward trend in bout duration and intensity was noted. Older infants gave more toys to the strangers and initiated more mutual play. Stranger–mother distance affected amount of proximity, not PI. Mother–stranger conversation was associated with less PI with the conversing stranger. At all ages infants sought more PI with their mothers than with the strangers. Although infants initiated an appreciable amount of PI with the strangers during the 40-min observation, comparison with other studies indicates that a stranger who takes the initiative by inviting play can establish more rapport much sooner. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
59.
Anisotropic in-plane strain arises in quantum-well systems by design or unintentionally. We propose two methods of measuring the in-plane strain anisotropy based on the optical polarization anisotropy that arises with anisotropic in-plane strain. One method uses purely optical means to determine the strain anisotropy in quantum wells under a compressive strain that is spatially varying. A second approach, applicable to quantum wells under tensile strain or with strain that does not vary with position, requires the application of a uniaxial in-plane stress. Although the second method is experimentally more difficult, it allows analysis of systems that would otherwise be inaccessible. 相似文献
60.
Christofi N Aspichueta E Dalzell D De la Sota A Etxebarria J Fernandes T Gutierrez M Morton J Obst U Schmellenkamp P 《Water research》2003,37(1):177-187
A laboratory model nitrifying activated sludge plant treating OECD synthetic sewage was designed and constructed by each of three laboratories in Germany, Scotland and Spain in order to produce a sludge inoculum for 5 rapid toxicity bioassays. The plants were run for 3 years and produced sludge for the microbially based bioassays Vibrio fischeri bioluminescence, ATP luminescence and respiration, and, nitrification and enzyme inhibition. Although the initial sludge inoculum for the plants differed, as did some of the running conditions such as temperature regime, the sludge produced within the different countries had similar characteristics with respect to sludge age, total suspended solids and volatile suspended solids. Nitrification was generally maintained over the 3-year period although there were occasions when the process was inconsistent. Nitrification recovery was afforded by reseeding with a nitrifying sludge from a local wastewater treatment works (WWTW) or imposition of starvation conditions for a period of time. The sludge produced was used to carry out toxicity testing and results compared well with those using sludge from a WWTW. Overall, the use of sludge generated in the laboratory could be used for toxicity testing negating the need to resort to the use of natural WWTW sludge, which may contain a range of toxic substances due to uncontrolled industrial and domestic inputs and an unbalanced microbial consortium. 相似文献