全文获取类型
收费全文 | 3697篇 |
免费 | 21篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 3篇 |
综合类 | 3篇 |
化学工业 | 60篇 |
金属工艺 | 13篇 |
机械仪表 | 7篇 |
建筑科学 | 28篇 |
矿业工程 | 2篇 |
能源动力 | 8篇 |
轻工业 | 20篇 |
石油天然气 | 1篇 |
武器工业 | 2篇 |
无线电 | 30篇 |
一般工业技术 | 55篇 |
冶金工业 | 3437篇 |
自动化技术 | 50篇 |
出版年
2022年 | 7篇 |
2021年 | 3篇 |
2020年 | 6篇 |
2018年 | 5篇 |
2017年 | 4篇 |
2016年 | 13篇 |
2015年 | 3篇 |
2014年 | 7篇 |
2013年 | 21篇 |
2012年 | 7篇 |
2011年 | 29篇 |
2010年 | 9篇 |
2009年 | 6篇 |
2008年 | 9篇 |
2007年 | 8篇 |
2006年 | 7篇 |
2005年 | 7篇 |
2004年 | 10篇 |
2003年 | 13篇 |
2002年 | 6篇 |
2001年 | 7篇 |
2000年 | 10篇 |
1999年 | 123篇 |
1998年 | 1143篇 |
1997年 | 663篇 |
1996年 | 395篇 |
1995年 | 203篇 |
1994年 | 184篇 |
1993年 | 232篇 |
1992年 | 15篇 |
1991年 | 30篇 |
1990年 | 31篇 |
1989年 | 42篇 |
1988年 | 38篇 |
1987年 | 34篇 |
1986年 | 18篇 |
1985年 | 27篇 |
1984年 | 4篇 |
1983年 | 10篇 |
1982年 | 22篇 |
1981年 | 17篇 |
1980年 | 29篇 |
1979年 | 3篇 |
1978年 | 13篇 |
1977年 | 79篇 |
1976年 | 144篇 |
1973年 | 3篇 |
1971年 | 3篇 |
1970年 | 2篇 |
1955年 | 3篇 |
排序方式: 共有3719条查询结果,搜索用时 15 毫秒
101.
D Sch?fer O Bianchi W Greulich C Sch?fer T Sch?fer ME Schl?fke 《Canadian Metallurgical Quarterly》1996,146(13-14):296-298
Most information about the structures within the brain stem that modulate respiration and sleep are gathered from animal experiments. Therefore we examined 10 patients several weeks after an infarction of the brain stem by means of polysomnography and tested the chemosensitive drives of respiration. None of these patients complained about symptoms of sleep disordered breathing. In each case polysomnographic measurements and ventilatory response curves revealed pathologic findings. The respiratory response to CO2 was diminished or completely abolished in each patient. In some cases hypoventilation or disturbances of the respiratory rhythmicity could be seen. In several cases missing REM sleep, sleep fragmentation or the reduction of slow wave sleep were observed. The study indicates that on the base of results from animal research the comparison of morphological and pathophysiological data is helpful to gain a better understanding on the coupling of the respiratory system with sleep at the brain stem level as well as on the pathomechanism of sleep related breathing disorder. 相似文献
102.
S. SIMARD M. DROGOWSKA H. ME´NARD L. BROSSARD 《Journal of Applied Electrochemistry》1997,27(3):317-324
The electrochemical behaviour of 1024 mild steel electrodes is investigated in the presence of 0.05–0.5 M sodium bicarbonate in aqueous solution at pH 8.9 and 25°C. Voltammograms are obtained with a rotating gold ring-mild steel electrode and the effect of the NaHCO3 concentration, the potential limits and the rotation speed of the disc electrode is considered. The voltammograms display an oxidation peak current at low potentials, a passivity region and a transpassive region at high potentials for the potential sweep in the anodic direction. The oxidation current in the passivity region is practically independent of the applied potential and the NaHCO3 concentration. The rate-determining step of the oxidation reaction in both the oxidation peak current region and the transpassive region is determined. 相似文献
103.
研究和讨论了图像质量评估方法,提出一种基于模糊推理的块效应评估标准。假设图像由平滑区域、边缘区域以及纹理区域等组成,而且不同的区域应采用不同的方法进行质量评估。在此基础上,给出了三个分别适用于不同区域的图像质量评估因子,并提出了一个灵活的模糊图像质量评估方法。此方法把块效应和图像本身具有的边缘分开,防止了边缘会被误认为是块效应。仿真结果表明,提出的标准对于不同的图像具有鲁棒性,有一般图像质量评价标准的性能。 相似文献
104.
Correlation between a dithering signal and the prediction error has been used for detecting model mismatch in univariate model based control systems. This paper extends that approach to MIMO control systems. A closed-loop cross-correlation method is presented to detect which specific input-output pairings of a model-based controller are mismatched. This method may be used in screening the complete set of models and in selecting candidate models for re-identification. The method first finds the rows and columns of the transfer function matrix that contain mismatch, and then the candidates are found by the intersection of the said rows and columns. Placing the system under partial control, whereby one or more of the manipulated variables are held constant, can be used to further reduce the set of candidate models. 相似文献
105.
Long-range correlation properties of coding and noncoding DNA sequences: GenBank analysis 总被引:1,自引:0,他引:1
SV Buldyrev AL Goldberger S Havlin RN Mantegna ME Matsa CK Peng M Simons HE Stanley 《Canadian Metallurgical Quarterly》1995,51(5):5084-5091
An open question in computational molecular biology is whether long-range correlations are present in both coding and noncoding DNA or only in the latter. To answer this question, we consider all 33301 coding and all 29453 noncoding eukaryotic sequences--each of length larger than 512 base pairs (bp)--in the present release of the GenBank to dtermine whether there is any statistically significant distinction in their long-range correlation properties. Standard fast Fourier transform (FFT) analysis indicates that coding sequences have practically no correlations in the range from 10 bp to 100 bp (spectral exponent beta=0.00 +/- 0.04, where the uncertainty is two standard deviations). In contrast, for noncoding sequences, the average value of the spectral exponent beta is positive (0.16 +/- 0.05) which unambiguously shows the presence of long-range correlations. We also separately analyze the 874 coding and the 1157 noncoding sequences that have more than 4096 bp and find a larger region of power-law behavior. We calculate the probability that these two data sets (coding and noncoding) were drawn from the same distribution and we find that it is less than 10(-10). We obtain independent confirmation of these findings using the method of detrended fluctuation analysis (DFA), which is designed to treat sequences with statistical heterogeneity, such as DNA's known mosaic structure ("patchiness") arising from the nonstationarity of nucleotide concentration. The near-perfect agreement between the two independent analysis methods, FFT and DFA, increases the confidence in the reliability of our conclusion. 相似文献
106.
107.
108.
Georg Menge Hannes Lorenz Zongwen Fu Franziska Eichhorn Florian Schader Kyle G. Webber Tobias Fey Peter Greil Nahum Travitzky 《Advanced Engineering Materials》2018,20(7)
109.
An exploratory, comparative survey design was used to describe and compare similarities and differences in perception of caring behaviors between hospitalized antepartum and short-stay postpartum patients. Forty-two patients completed the 63-item Caring Behavior Assessment instrument (CBA). The scale, based on Watson's theory of caring, contains seven categories. There were no statistically significant differences in age, education, gravida, or para between the two groups. Significantly more women in the postpartum group were married. There were no statistically significant differences or correlations in the total CBA scores and the demographic variables. No statistically significant differences in total CBA scores were found between antepartum participants and postpartum participants. These findings corroborate the results of "caring" studies in other patient populations, that satisfying basic needs--that is, evidence of technical knowledge and skills--is more important to patients than meeting higher order needs. 相似文献
110.
Pancreatic cancer is a dismal disease. The 5-year overall survival ranges from 1% to 5%. Surgery is the only curative treatment available for this cancer, but it is indicated only in selected patients with a less than 4 cm tumor. In these patients, survival rate is about 30%. We have considered several aspects: the very difficult early diagnosis, the correct diagnostic flow chart, actual surgical procedures and new trends in biologic and genetic research. It is likely that better results can be achieved by defining an "early pancreatic cancer" and establishing how to detect it. This could be the wrigth one way is to significantly improve the survival of these patients. 相似文献