全文获取类型
收费全文 | 1583篇 |
免费 | 36篇 |
专业分类
电工技术 | 17篇 |
化学工业 | 287篇 |
金属工艺 | 25篇 |
机械仪表 | 30篇 |
建筑科学 | 82篇 |
矿业工程 | 17篇 |
能源动力 | 39篇 |
轻工业 | 134篇 |
水利工程 | 7篇 |
石油天然气 | 10篇 |
武器工业 | 1篇 |
无线电 | 113篇 |
一般工业技术 | 193篇 |
冶金工业 | 404篇 |
原子能技术 | 12篇 |
自动化技术 | 248篇 |
出版年
2022年 | 9篇 |
2021年 | 9篇 |
2020年 | 9篇 |
2019年 | 12篇 |
2018年 | 17篇 |
2017年 | 13篇 |
2016年 | 19篇 |
2015年 | 27篇 |
2014年 | 30篇 |
2013年 | 90篇 |
2012年 | 46篇 |
2011年 | 73篇 |
2010年 | 50篇 |
2009年 | 74篇 |
2008年 | 58篇 |
2007年 | 64篇 |
2006年 | 77篇 |
2005年 | 66篇 |
2004年 | 64篇 |
2003年 | 49篇 |
2002年 | 55篇 |
2001年 | 47篇 |
2000年 | 33篇 |
1999年 | 36篇 |
1998年 | 50篇 |
1997年 | 45篇 |
1996年 | 43篇 |
1995年 | 26篇 |
1994年 | 30篇 |
1993年 | 28篇 |
1992年 | 32篇 |
1991年 | 13篇 |
1990年 | 31篇 |
1989年 | 12篇 |
1988年 | 11篇 |
1987年 | 17篇 |
1986年 | 18篇 |
1985年 | 25篇 |
1984年 | 27篇 |
1983年 | 22篇 |
1982年 | 16篇 |
1981年 | 13篇 |
1980年 | 13篇 |
1979年 | 15篇 |
1978年 | 11篇 |
1977年 | 13篇 |
1976年 | 22篇 |
1975年 | 10篇 |
1974年 | 9篇 |
1973年 | 10篇 |
排序方式: 共有1619条查询结果,搜索用时 0 毫秒
11.
12.
Abstract— A contrast‐enhanced wide‐angle high‐speed polarization modulator for active‐retarder 3‐D displays is proposed. By using a double liquid‐crystal‐cell structure together with a dedicated driving scheme and an external quarter‐wave retarder, a high‐performance modulator can be realized, resulting in minimized brightness loss and low cross‐talk levels in fast‐refresh time‐multiplexed 3‐D displays. 相似文献
13.
Randy V. Bradley Renée M. E. Pratt Terry Anthony Byrd Christina N. Outlay Donald E. Wynn Jr. 《Information Systems Journal》2012,22(2):97-127
Despite the possible benefits of implementing healthcare information technologies, successful implementation of effective healthcare information technology is constrained by cultural and regulatory concerns and technical obstacles encountered when establishing or upgrading an organisation's enterprise infrastructure. In this paper, we advance Ross' four‐stage model of enterprise architecture maturity as a valuable IT resource for helping healthcare organisations sustain a competitive advantage. We use partial least squares (PLS) structural equation modelling to analyse survey data from 164 US hospitals at different stages of EA maturity. Our results provide evidence that enterprise architecture maturity directly influences the effectiveness of hospitals' IT resources for achieving strategic goals. Further, enterprise architecture maturity indirectly influences the effectiveness of IT resources when IT alignment is incorporated as a mediating variable. We discuss the implications of our findings for research and practice and suggest opportunities for future research. 相似文献
14.
Dietary stearic acid and risk of cardiovascular disease: Intake,sources, digestion,and absorption 总被引:1,自引:2,他引:1
Individual FA have diverse biological effects, some of which affect the risk of cardiovascular disease (CVD). In the context
of food-based dietary guidance designed to reduce CVD risk, fat and FA recommendations focus on reducing saturated FA (SFA)
and trans FA (TFA), and ensuring an adequate intake of unsaturated FA. Because stearic acid shares many physical properties with the
other long-chain SFA but has different physiological effects, it is being evaluated as a substitute for TFA in food manufacturing.
For stearic acid to become the primary replacement for TFA, it is essential that its physical properties and biological effects
be well understood. 相似文献
15.
On-line determination of supersaturation of a kcl-nacl aqueous solution based on density measurement
A method is developed for the calculation of the saturation temperature of a KCI-NaCI aqueous solution, based on the measurement of the density and temperature of a sample solution, and prior knowledge of the NaCl concentration. Experimental density and solubility data for solutions saturated with KCI in the temperature range of 299 to 321 K with concentrations of NaCl greater than 0.200 kg/kg H2O were used to develop the empirical correlation allowing the calculation of the solution saturation level. The method is applicable in the on-line determination of the level of supersaturation in a KCI crystallizer in which the NaCl concentration is known. Knowledge of the prevailing supersaturation is necessary for the control of crystal purity and crystal size distribution in industrial potash crystallizers. 相似文献
16.
Terry Carolyn J.; Blake Colin C. F. 《Protein engineering, design & selection : PEDS》1992,5(6):505-510
The structure of cleaved thyroxine-binding globulin (TBG) hasbeen modelled on the crystal structure of cleaved 1-antitrypsin(a member of the serine proteinase inhibitor, serpin, superfamily)based on the high sequence homology exhibited by the two proteins.Particular attention was paid to the identification and modelledcharacteristics of the thyroxine binding site. The primary aimof the study was to compare the site qualitatively with thecrystallographically determined binding site of transthyretin,the other major transporter of thyroxine, in an attempt to explainthe higher binding affinity of the site compared with the knownthyrox ine binding site in transthyretin (1010 versus 108 M1).The proposed binding site shares some similar characteristicswith the transthyretin binding site but also includes a clusterof aromatic residues which are entirely absent in transthyretin.It is proposed that this might account for the substantial differencein binding affinities. 相似文献
17.
Meadowfoam fatty acids, when treated with mineral acid catalysts in the presence of polar nonparticipating solvents, undergo
a facile ring closure to form δ-lactones. Perchloric and sulfuric acids catalyze the cyclization at concentrations of 0.6–13
mole equivalents, both neat and in the presence of solvent. Under constant acid concentrations, methylene chloride was found
to increase the rate of reaction, the regioselectivity for the formation of δ-lactone, and the overall yield. In the absence
of solvent, increased acid concentration improved the yield of lactone but reduced regioselectivity for the δ-isomer. Solvent
polarity plays a significant role in the regioselectivity of the cyclization for δ-lactone, with solvents of higher dielectric
strength providing larger δ/γ ratios (38:1) and higher yields up to 92%. 相似文献
18.
Keiichiro Oh-ishi John Boydon Terry R. McNelley 《Journal of Materials Engineering and Performance》2004,13(6):710-719
The importance of grain size refinement in enabling superplasticity is reviewed, and the current understanding of grain boundary
characteristics is summarized. The application of orientation-imaging microscopy (OIM) methods to the processing response
and the deformation and failure modes in superplastic aluminum alloys are illustrated through microtexture analysis and determination
of grain boundary characteristics in selected commercial materials. Continuous and discontinuous recrystallization reactions
exhibit distinct microtextures and grain boundary characteristics. The application of OIM and microtexture analysis to the
evaluation of both deformation and failure mechanisms during superplastic forming is illustrated.
This paper was presented at the International Symposium on Superplasticity and Superplastic Forming, sponsored by the Manufacturing
Critical Sector at the ASM International AeroMat 2004 Conference and Exposition, June 8–9, 2004, in Seattle, WA. The symposium
was organized by Daniel G. Sanders, The Boeing Company. 相似文献
19.
Terry C. Lowe Ruslan Z. Valiev 《JOM Journal of the Minerals, Metals and Materials Society》2004,56(10):64-68
Severe plastic deformation (SPD) has emerged as a promising method to produce ultrafine-grained materials with attractive
properties. Today, SPD techniques are rapidly developing and are on the verge of moving from lab-scale research into commercial
production. This paper discusses new trends in the development of SPD techniques suchas high-pressure torsion and equal-channel
angle pressing, as well as new alternative techniques for introducing SPD. The paper also contains a comparative analysis
of SPD techniques in terms of their relative capabilities for grain refinement, enhancement of properties, and potential to
economically produce ultrafine-grained metals and alloys.
For more information, contact Terry C. Lowe, Science and Technology Base Programs, Los Alamos National Laboratory, Los Alamos,
NM 87545; (505) 667-7824; fax (505) 665-3199; e-mail tlowe@lanl.gov. 相似文献
20.
Testing Forecast Accuracy of Foreign Exchange Rates: Predictions from Feed Forward and Various Recurrent Neural Network Architectures 总被引:3,自引:1,他引:2
In this research, we work with data of futures contracts on foreign exchange rates for British pound (BP), Canadian dollar
(CD), and Japanese yen (JY) that are traded at the Chicago Mercantile Exchange (CME) against US dollars. We model relationships
between exchange rates in these currencies using linear models, feed forward artificial neural networks (ANN), and three versions
of recurrent neural networks (RNN1, RNN2 and RNN3) for predicting exchange rates in these currencies against the US dollar.
Our results on forecast evaluations based on AGS test the tests of forecast equivalence between any two competing models among
the entire models employed for each of the series show that ANN and the three versions of RNN models offer superior forecasts
for predicting BP, CD and JY exchange rates although the forecast evaluations based on MGN test are in sharp contrast. On
the other hand forecast based on SIGN test shows that ANN and all the versions of RNN models offer superior forecasts for
BP and CD in exception of JY exchange rates. The results for forecast evaluation for all the models for each of the series
based on summary measures of forecast evaluations show that RNN3 model appears to offer the most accurate predictions of BP
and RNN1 for JP exchange rates. However, none of the RNN models appear to be statistically superior to the benchmark (i.e.,
linear model) for predicting CD exchange rates.
相似文献