全文获取类型
收费全文 | 987篇 |
免费 | 24篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 130篇 |
化学工业 | 207篇 |
金属工艺 | 15篇 |
机械仪表 | 23篇 |
建筑科学 | 15篇 |
矿业工程 | 2篇 |
能源动力 | 35篇 |
轻工业 | 99篇 |
石油天然气 | 2篇 |
无线电 | 110篇 |
一般工业技术 | 148篇 |
冶金工业 | 132篇 |
原子能技术 | 26篇 |
自动化技术 | 68篇 |
出版年
2023年 | 4篇 |
2022年 | 10篇 |
2021年 | 20篇 |
2020年 | 6篇 |
2019年 | 14篇 |
2018年 | 14篇 |
2017年 | 10篇 |
2016年 | 14篇 |
2015年 | 21篇 |
2014年 | 15篇 |
2013年 | 57篇 |
2012年 | 35篇 |
2011年 | 48篇 |
2010年 | 47篇 |
2009年 | 41篇 |
2008年 | 47篇 |
2007年 | 47篇 |
2006年 | 48篇 |
2005年 | 29篇 |
2004年 | 23篇 |
2003年 | 42篇 |
2002年 | 27篇 |
2001年 | 19篇 |
2000年 | 24篇 |
1999年 | 23篇 |
1998年 | 68篇 |
1997年 | 33篇 |
1996年 | 28篇 |
1995年 | 26篇 |
1994年 | 9篇 |
1993年 | 19篇 |
1992年 | 14篇 |
1991年 | 8篇 |
1990年 | 11篇 |
1989年 | 10篇 |
1988年 | 9篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1982年 | 9篇 |
1981年 | 9篇 |
1980年 | 3篇 |
1978年 | 6篇 |
1977年 | 8篇 |
1976年 | 9篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1972年 | 4篇 |
排序方式: 共有1012条查询结果,搜索用时 31 毫秒
951.
Various biological reaction models have been proposed which estimate concentrations of soluble and insoluble components in effluent of sewage treatment plants. These models should be effective to develop a better operation system and plant design, but their formulas consist of nonlinear equations, and there are many model constants, which are not easy to calibrate. A technique has been proposed to decide the model constants by precise experiments, but it is not practical for design engineers or process operators to perform these experiments regularly. Other approaches which calibrate the model constants by mathematical techniques should be used. In this paper, the optimal regulator method of modern control theory is applied as a mathematical technique to calibrate the model constants. This method is applied in a small sewage treatment testing facility. Calibration of the model constants is examined to decrease the deviations between calculated and measured concentrations. Results show that calculated values of component concentrations approach measured values and the method is useful for actual plants. 相似文献
952.
Amano K Uchikawa K Kuriki I 《Journal of the Optical Society of America. A, Optics, image science, and vision》2002,19(8):1501-1514
To study the characteristics of color memory for natural images, a memory-identification task was performed with differing color contrasts; three of the contrasts were defined by chromatic and luminance components of the image, and the others were defined with respect to the categorical colors. After observing a series of pictures successively, subjects identified the pictures using a confidence rating. Detection of increased contrasts tended to be harder than detection of decreased contrasts, suggesting that the chromaticness of pictures is enhanced in memory. Detecting changes within each color category was more difficult than across the categories. A multiple mechanism that processes color differences and categorical colors is briefly considered. 相似文献
953.
N Furuumi D Amano YJ Xu K Samejima M Niitsu A Shirahata 《Canadian Metallurgical Quarterly》1998,265(2):253-259
It has been reported that glutamate-induced neurotoxicity is related to an increase in nitric oxide (NO) concentration. An NO-sensitive electrode has been developed to measure NO concentration directly. Using this electrode, we examined NO concentration and neuronal survival after glutamate application in rat cultured cortical neurons. We also examined the effects of NMDA receptor antagonists, MK-801 and ketamine, and the NO synthetase inhibitor, L-NMMA on NO production and neuronal death. After 7 days in culture, application of glutamate (1 mM) or L-arginine (0.3 mM) to the cultured medium increased NO concentration, and decreased the number of anti-microtubule-associated protein 2 positive neurons. Both pretreatment with MK-801 (300 microns) and ketamine (300 microns) prevented glutamate-, but not L-arginine-induced increase in NO concentration and neuronal death. L-NMMA prevented both glutamate- and L-arginine-induced NO production and neuronal death. The nitric oxide donor, S-nitroso-N-acetyl-D,L-penicillamine (SNAP) also caused neuronal death, and MK-801, ketamine and L-NMMA did not prevent SNAP-induced toxicity. We have demonstrated excitatory amino acid-induced changes of NO concentration and the parallel relationship between changes of NO concentration and neuronal death. In conclusion, an increase in NO concentration does induce neuronal death, and the inhibition of the production of NO prevents glutamate-induced neuronal death. 相似文献
954.
955.
Keisuke Kurita Hirofumi Akao Masayuki Kobayashi Tomonori Mori Yasuhiro Nishiyama 《Polymer Bulletin》1997,39(5):543-549
β-d-Galactoside branches have been introduced into chitosan and chitin regioselectively through a series of controlled modification
reactions based on N-phthaloyl-chitosan. The glycosylation reaction between a chitosan derivative having a reactive group only at C-6 and an orthoester
of d-galactose proceeded efficiently to give a protected product with a degree of substitution up to about 0.5. Deprotection gave
a branched chitosan, and the subsequent N-acetylation afforded a branched chitin. Unlike chitosan and chitin, the resulting nonnatural branched polysaccharides were
characterized by high affinity for solvents and readily soluble in neutral water. Furthermore, branched chitin was easily
degraded by lysozyme.
Received: 31 July 1997/Revised: 2 September 1997/Accepted: 19 September 1997 相似文献
956.
A new sample preparation technique is proposed for evaluating image resolution in a high magnification range of SEM. The proposed reference samples are uniformly distributed nanometer-scale Au particles on HOPG substrate. The samples are fabricated using the conventional ion sputter coater. The grain size and granularity are controlled by reducing the sputter-induced damage in the top layers of HOPG. The sample heating prior to SEM imaging is essential to suppress beam induced contamination. The heating time and temperature are selected to inhibit large increases in the grain sizes of Au particles. The sputter coated Au particles on the freshly cleaved HOPG substrate are superior in the deviations of particle sizes to the vacuum evaporated Au particles on the plasma etched substrates. The granularity and homogeneous distribution of Au particles on HOPG are demonstrated at a magnification range of x180k to x800k. The average grain size of 3.2 nm and the standard deviation of 1.3 nm are obtained under the condition of an annealing temperature of 180 degrees C for 7 min after sputter coating an average thickness of 0.7 nm. 相似文献
957.
Adaptive shaping of time-dependent polarization pulses is performed by reference to the analyzed results of dual-channel spectral interferometry. The desired pulses can be generated only by use of such a polarization-characterization technique. We demonstrate the generation of shaped femtosecond pulses whose ellipticity increases at a constant rate. The relative error between the shaped pulse and the target pulse is less than 6% over the main part of the pulse. Shaped time-dependent polarization pulses have many potential applications. 相似文献
958.
Contents and its change during storage of alpha-solanine and alpha-chaconine in potatoes 总被引:1,自引:0,他引:1
Shindo T Ushiyama H Kan K Yasuda K Saito K 《Shokuhin eiseigaku zasshi. Journal of the Food Hygienic Society of Japan》2004,45(5):277-282
Contents of alpha-solanine and alpha-chaconine in native species of potato (May Queen, Danshaku and Waseshiro), and in species (Jagakids Red '90 (Red) and Jagakids Purple '90 (Purple)) on the market, and their change during storage at room temparature were investigated. alpha-Solanine and alpha-chaconine were extracted from potatoes with methanol, cleaned up by using a Sep-Pak Plus C18 cartridge, and then subjected to HPLC. The recoveries of alpha-solanine and alpha-chaconine from potatoes were both more than 96%, and the quantitation limits were both 2 microg/g. alpha-Solanine and alpha-chaconine were detected in periderm in all samples at the levels of 260-320 microg/g in May Queen,190-240 microg/g in Danshaku, 43-63 microg/g in Waseshiro, 140-200 microg/g in Red and 84-130 microg/g in Purple, respectively. alpha-Solanine and alpha-chaconine were detected in the cortex in all samples of May Queen and Danshaku at the levels of 2.7-12 microg/g and 5.8-31 microg/g, respectively. Contents of alpha-solanine and alpha-chaconine in the cortex of May Queen and Danshaku were less than 10% of those in the periderm. When potatoes were stored for 90 days at room temparature in a dark place, no marked change in the contents of alpha-solanine and alpha-chaconine was observed in any of the potato samples. 相似文献
959.
Nakano M Komatsu J Kurita H Yasuda H Katsura S Mizuno A 《Journal of Bioscience and Bioengineering》2005,100(2):216-218
The adaptor polymerase chain reaction (PCR) permits the amplification of DNA fragments with arbitrary sequences. In this paper, we describe the successful amplification of plasmid-derived single molecule DNAs digested by a restriction enzyme. By using adaptors made of short and long oligonucleotides, nonspecific interactions during PCR were suppressed. The method will be applicable to the detection of single molecule DNA fragments even if their sequence is unknown. 相似文献
960.
Komaba T. Kanai K. Yoshida S. Shigetoshi I. Amano K. 《Power Delivery, IEEE Transactions on》1992,7(4):1706-1712
The authors have developed a flexible dimensionally flush joint for 500 kV aluminum-sheathed oil-filled cables with handling characteristics similar to the cable itself so that it may be readily drawn into ducts in the same way as the cable without suffering damage. The process and characteristics are outlined. This joint is intended for use at intermediate points on long bridges or tunnels where local assembly and installation of conventional joints would be difficult. In developing the joint, various novel techniques have been used, including the flexible flush jointing of segmental conductors, the flexible jointing of paper insulation by a combination of wrapping-back and stepping methods, and on-site aluminum sheath corrugating and sealing methods 相似文献