全文获取类型
收费全文 | 8585篇 |
免费 | 240篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 69篇 |
综合类 | 2篇 |
化学工业 | 1428篇 |
金属工艺 | 85篇 |
机械仪表 | 198篇 |
建筑科学 | 315篇 |
矿业工程 | 18篇 |
能源动力 | 162篇 |
轻工业 | 961篇 |
水利工程 | 77篇 |
石油天然气 | 33篇 |
无线电 | 631篇 |
一般工业技术 | 1109篇 |
冶金工业 | 2792篇 |
原子能技术 | 80篇 |
自动化技术 | 869篇 |
出版年
2022年 | 110篇 |
2021年 | 142篇 |
2020年 | 109篇 |
2019年 | 106篇 |
2018年 | 117篇 |
2017年 | 118篇 |
2016年 | 117篇 |
2015年 | 108篇 |
2014年 | 162篇 |
2013年 | 430篇 |
2012年 | 242篇 |
2011年 | 348篇 |
2010年 | 273篇 |
2009年 | 276篇 |
2008年 | 310篇 |
2007年 | 307篇 |
2006年 | 252篇 |
2005年 | 250篇 |
2004年 | 215篇 |
2003年 | 207篇 |
2002年 | 228篇 |
2001年 | 167篇 |
2000年 | 157篇 |
1999年 | 203篇 |
1998年 | 571篇 |
1997年 | 400篇 |
1996年 | 289篇 |
1995年 | 179篇 |
1994年 | 171篇 |
1993年 | 177篇 |
1992年 | 107篇 |
1991年 | 90篇 |
1990年 | 90篇 |
1989年 | 114篇 |
1988年 | 110篇 |
1987年 | 94篇 |
1986年 | 92篇 |
1985年 | 101篇 |
1984年 | 108篇 |
1983年 | 71篇 |
1982年 | 92篇 |
1981年 | 80篇 |
1980年 | 79篇 |
1979年 | 70篇 |
1978年 | 78篇 |
1977年 | 103篇 |
1976年 | 156篇 |
1975年 | 45篇 |
1974年 | 60篇 |
1973年 | 51篇 |
排序方式: 共有8829条查询结果,搜索用时 17 毫秒
71.
Nelson Douglas L.; Keelean Patricia D.; Negrao Maura 《Canadian Metallurgical Quarterly》1989,15(3):388
In four experiments we evaluated aspects of the hypothesis that word-fragment completion depends on the results of lexical but not semantic search. Experiment 1 showed that the number of meaningful associates linked to a studied word does not affect its recovery when the test cue consists of letters and spaces for missing letters. Experiments 2 and 3 showed retroactive interference effects in fragment completion when words in a second list were lexically related to words in a first list but not when the words in the second list were meaningfully related. Experiment 4 indicated that for studied words, instructions to search at the word level facilitated completion performance and that instructions to generate letters to fill missing spaces had no effect. Other findings indicate that completion was affected by the number of words lexically related to the fragment and by the number of letters missing from the fragment. In general, experimental manipulations that focused on lexical characteristics were effective, and those that focused on semantic characteristics were ineffective. The findings support the conclusion that word fragments engender a lexical search process that does not depend on retrieving encoded meaning. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
72.
Lada E.K. Jye-Chyi Lu Wilson J.R. 《Semiconductor Manufacturing, IEEE Transactions on》2002,15(1):79-90
To detect faults in a time-dependent process, we apply a discrete wavelet transform (DWT) to several independently replicated data sets generated by that process. The DWT can capture irregular data patterns such as sharp "jumps" better than the Fourier transform and standard statistical procedures without adding much computational complexity. Our wavelet coefficient selection method effectively balances model parsimony against data reconstruction error. The few selected wavelet coefficients serve as the "reduced-size" data set to facilitate an efficient decision-making method in situations with potentially large-volume data sets. We develop a general procedure to detect process faults based on differences between the reduced-size data sets obtained from the nominal (in-control) process and from a new instance of the target process that must be tested for an out-of-control condition. The distribution of the test statistic is constructed first using normal distribution theory and then with a new resampling procedure called "reversed jackknifing" that does not require any restrictive distributional assumptions. A Monte Carlo study demonstrates the effectiveness of these procedures. Our methods successfully detect process faults for quadrupole mass spectrometry samples collected from a rapid thermal chemical vapor deposition process 相似文献
73.
74.
S. J. Pearton K. P. Lee M. E. Overberg C. R. Abernathy N. Theodoropoulou A. F. Hebard R. G. Wilson S. N. G. Chu J. M. Zavada 《Journal of Electronic Materials》2002,31(5):336-339
High concentrations (0.1–5 at.%) of Mn or Fe were introduced into the near-surface region (≤2000 Å) of 6H-SiC substrates by direct implantation at ~300°C. After annealing at temperatures up to 1000°C, the structural properties were examined by transmission electron microscopy (TEM) and selected-area diffraction pattern (SADP) analysis. The magnetic properties were examined by SQUID magnetometry. While the Mn-implanted samples were paramagnetic over the entire dose range investigated, the Fe-implanted material displayed a ferromagnetic contribution present at <175 K for the highest dose conditions. No secondary phases were detected, at least not to the sensitivity of TEM or SADP. 相似文献
75.
76.
Carl A. Soderstrom Patricia C. Dischinger Gordon S. Smith J.Richard Hebel David R. McDuff David A. Gorelick Timothy J. Kerns Shiu M. Ho Kathleen M. Read 《Accident; analysis and prevention》1997,29(6):715-721
A structured in-depth interview employing standardized criteria was used to determine the prevalence of lifetime and current alcohol dependence (alcoholism) in unselected consecutive patients admitted to a regional Level I trauma center. Of 629 patients, 157 (25.0%) were current alcoholics at the time of injury. An additional 87 (13.8%) were diagnosed as lifetime non-current alcoholics. There was no significant difference in the rates of current alcohol dependence among patients injured in vehicular crashes (23.5%), other unintentional trauma victims (29.3%), and those injured as a result of violence (24.6%). Of BAC + (blood alcohol concentration positive) patients, 54.5% were current alcoholics. However, 14.4% of alcohol-negative patients were also diagnosed as alcohol dependent. 相似文献
77.
Magnetorheological materials have been used in many applications in recent years. To develop new materials, polyurethane and silicone polymer gels were investigated. Rheology is qualitatively controlled for each system by controlling the concentration of reactants and diluents. The resulting polymers have solid, gel, or liquid states, depending on the crosslinking and dilution. The gels were characterized through kinetic analysis. Differential scanning calorimetry (DSC) was used with analysis methods to find the kinetic properties for diluted and undiluted polyurethane systems. Heat of reaction, order of reaction, preexponential constant, and activation energy were obtained from the experimental DSC data. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2733–2742, 2002 相似文献
78.
79.
The settling rates and adsorption isotherms produced by a variety of suites of cationic polyelectrolytes in 3% kaolin suspensions were measured. Settling rates increased with molar mass even for low-mass, high-charge polymers. The very high settling rates produced by cationic copolymers of acrylamide decreased as the charge density of the polymer used increased. Hydrolysis of unbuffered polymers occurred over time and produced large changes in the effectiveness of the polymers. This is attributed to conformational changes. © 1994 John Wiley & Sons, Inc. 相似文献
80.
Several samples of exhaust diesel soot are investigated by inverse gas chromatography and linear solvation energy relationship (LSER) modelling according to their soluble organic fraction content and their time of exposure in oxidative conditions. The results demonstrate the evolution of the adsorptive properties of the studied materials towards volatile compounds during the oxidation under NO2. 相似文献