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排序方式: 共有514条查询结果,搜索用时 31 毫秒
41.
Iulian Riposan Mihai Chisamera Stelian Stan Pavel Toboc Geir Grasmo Douglas White Chris Ecob Cathrine Hartung 《Journal of Materials Engineering and Performance》2011,20(1):57-64
Two main chemistry systems of micro-inclusions can be identified in ductile iron: Ca-S-X and Mg-Si-O-X with the majority of
the inclusions regardless of treatment type and location being of the second type, silicates. Laboratory investigations have
shown that simple silicates were present in the matrix, while more complex silicates were present in conjunction with graphite,
probably acting as graphite nucleation sites. In these more complex silicates, elevated levels of Al, Ca, Ce and La were typical.
Comparing micro-particles embedded in iron matrix and graphite nodules of iron treated with pure Mg-metal and iron treated
with MgFeSi alloy showed a higher amount of complex silicates with elevated Al-levels in the iron treated with MgFeSi. Further
laboratory investigation was undertaken to explore which source of Al and which range of residual Al would have a favorable
impact on the graphite nucleation in ductile iron. The work showed that a residual aluminum of 0.005 to 0.020 wt.% appears
to be beneficial for improving ductile iron solidification characteristics without the incidence of pinholes. Greatest benefits
were achieved when introducing the Al into the iron via an inoculant late during processing or via a pre-conditioner to the
base iron. Al added via the MgFeSi provided less benefit. Some case studies illustrating the effect of Al in ductile iron
are also presented, as Al-containing pre-conditioner or/and Al-bearing, FeSi inoculant application. 相似文献
42.
Digital dermatitis is a serious problem in dairy production in many countries. In many settings, it is important to evaluate the digital dermatitis status of individual cows or an entire dairy herd. Such an evaluation has traditionally been done in a hoof trimming chute. An evaluation in the milking parlor can take place without disturbing the cows to a large extent, it can be done using less labor compared with an evaluation in a hoof trimming chute, and is cheaper than using a chute. The objective was to evaluate the sensitivity and specificity of a rapid screening method for digital dermatitis in the milking parlor, without using any specialized tools and taking approximately 15 s/cow. All lactating cows in 3 commercial Danish dairy herds were included. Cows were first scored for the presence of digital dermatitis during milking and the next day all cows were scored during hoof trimming. A 6-point nominal scoring system based on a visual inspection of the digital dermatitis lesions was used. For the analysis, the scores were dichotomized (digital dermatitis positive or digital dermatitis negative). Additionally, lesions were classified as small (diameter ≤ 2 cm) or large (diameter >2 cm). Sensitivity and specificity were calculated using observations from the hoof trimming chute as the “gold standard” and observations during milking as the diagnostic test. Relatively large variation was found between herds with an overall sensitivity of 0.65 (95% confidence interval: 0.59 to 0.72) and a specificity of 0.84 (0.81 to 0.87). The sensitivity increased to 0.69 (0.62 to 0.76), when only large lesions were assessed. The method has several advantages compared with evaluation in a chute and may be a useful tool in the daily hoof health management in dairy herds. 相似文献
43.
Hans Erhorn Tomasz Mroz Ove Mørck Fritz Schmidt Lorenz Schoff Kirsten Engelund Thomsen 《Energy and Buildings》2008,40(4):419-428
Educational buildings such as kindergartens, schools and universities display many similar design, operation and maintenance features in most countries. The two most noteworthy similarities amongst these building types are the high energy consumption and the necessity for retrofitting many buildings within this sector. However, studies have shown that during retrofit, energy saving measures are only rarely applied, because the decision-makers lack knowledge of investments and the efficiency of potential energy saving measures. The main goal of the International Energy Agency ECBCS Annex 36 is to provide the educational building decision-makers with sufficient data, information and tools to improve their learning and teaching environments by improving the energy efficiency of their buildings. 相似文献
44.
A 27-year-old woman was admitted with an abdominal mass in the right hypochondrium. Ultrasound, intravenous urography and scintigraphy revealed a giant non-functioning hydronephrosis. Because she refused surgery, a percutaneous aspiration with instillation of doxycycline was performed. One year thereafter, the patient was still without recurrence of any symptoms or hydronephrosis. 相似文献
45.
Late psychosocial improvement in a case of severe head injury with bilateral fronto-orbital lesions.
Describes the results of a 19-yr follow-up study of a head-injured female patient. At age 17 yrs, the S sustained a blunt head trauma with bilateral fronto-orbital lesions verified by late regional cerebral blood flow. The S presented an extreme state of regression for many months after injury. During the first posttraumatic years no behavioral disorders were reported, but after the 5th yr lack of control, including sexual disinhibition, and lack of motivation became severe problems. More than 10 yrs after the accident, a partner applied a simple program of behavioral modification to the S. After 2 yrs of rigid training, an unexpected improvement in psychosocial adaptation took place. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
46.
Van Gils M. Rosenfalck A. White S. Prior P. Gade J. Senhadji L. Thomsen C. Ghosh I.R. Longford R.M. Jensen K. 《IEEE engineering in medicine and biology magazine》1997,16(6):56-63
Methods for analyzing and displaying EEG signals are discussed. The increasing availability and affordability of powerful computer equipment makes possible the use of ever more sophisticated signal processing techniques, which extract relevant (but not readily discernible) information from long-term EEG recordings and can easily identify important features in the EEG. Whether these techniques are actually taken up in clinical practice is heavily dependent on how well they match clinical requirements. This article concentrates on requirements set in the context of long-term recordings in the ICU that demand the ability to process short-term discrete events as well as long-term trend information. A huge range of potentially useful signal processing techniques exists. This article illustrates the value of some of these techniques for ICU signals using the EEG recordings collected during the IMPROVE project 相似文献
47.
We compare the performance of a digital receiver operating with both a fixed and adaptive decision threshold in response to gain transients arising from network operation of an optically gain-clamped erbium-doped fiber amplifier. An optical burst switching link, based on a recirculating transmission loop, is used to study the effect of transients accumulated across a number wavelength-routing nodes linked by amplified fiber spans where bursts are added and dropped at each node. The use of an adaptive threshold reduces the amount of optical feedback required by a factor of 6 and, in some cases, allows for unclamped operation. 相似文献
48.
Lead (Pb) is well known as an environmental pollutant: it can accumulate in various media, so actual lead exposure reflects both historical and present contaminations. Two main challenges then emerge: obtaining updated information to gain an overall picture of the sources of exposure, and predicting the resulting internal body exposure levels and effects that occur under long-term exposure conditions. In this paper, a modeling approach is used to meet these challenges with reference to Danish exposure conditions. Levels of lead content in various media have been coupled with data for lead intake and absorption in the human body, for both children and adults. An age-dependent biokinetic model allows then for determination of the blood lead levels resulting from chronic exposure. The study shows that the actual intake of lead is up to 27% of the Provisional Tolerable Daily Intake (PTDI) for children and around 8% for adults. It is confirmed that the critical route of exposure is via ingestion, accounting for 99% of total lead intake, while inhalation contributes only to 1% of total lead intake. The resulting lead levels in the blood after 2 years of exposure to actual contamination conditions have been estimated as up to 2.2 μg/dl in children and almost 1 μg/dl in adults. Impacts from lead can occur even at such levels. The role of historical and present sources to lead in the environment is discussed, and, for specific child and adult exposure scenarios, external-internal concentration relationships for the direct linkage between lead in environmental media and resulting concentrations of lead in blood are then presented. 相似文献
49.
A.E. Lewis J. Nathoo K. Thomsen H.J. Kramer G.J. Witkamp S.T. Reddy D.G. Randall 《Chemical Engineering Research and Design》2010
Complex, hypersaline brines originating from the mining and extractive metallurgical industries have the potential to be treated using Eutectic Freeze Crystallization (EFC). Although EFC has been shown to be effective in separating a single salt and water, it has yet to be applied to the complex hypersaline brines that are typical of reverse osmosis retentates in South Africa. This paper focuses on the application of EFC for the purification of a typical brine containing high levels of sodium, chlorine, sulphate and ammonia that cannot be achieved with other separation techniques. The presence of ammonia prevents the application of membrane technology to treat the brine, leaving only cooling or evaporation as other possible options. Evaporation produces a mixed salt that requires further treatment. Modelling tools were applied to describe the phase behaviour of the complex saline systems under different process conditions and were experimentally validated. The results showed that Eutectic Freeze Crystallization could be used to selectively recover the sodium as a sodium sulphate salt. The simulation tools were especially useful in the design and optimisation of the process. 相似文献
50.
I. Miloševi? N. Kep?ijaE. Dobard?i? M. Damnjanovi?M. Mohr J. MaultzschC. Thomsen 《Materials Science and Engineering: B》2011,176(6):510-511
Symmetry based analysis of the Kohn anomaly is performed. Kohn phonon frequencies and displacements are calculated by force constant method. It is shown that Kohn phonon vibrations cause electronic band gap opening. 相似文献