全文获取类型
收费全文 | 244篇 |
免费 | 14篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 2篇 |
化学工业 | 75篇 |
金属工艺 | 2篇 |
机械仪表 | 4篇 |
建筑科学 | 6篇 |
能源动力 | 4篇 |
轻工业 | 53篇 |
水利工程 | 2篇 |
石油天然气 | 3篇 |
无线电 | 18篇 |
一般工业技术 | 36篇 |
冶金工业 | 35篇 |
原子能技术 | 1篇 |
自动化技术 | 19篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 19篇 |
2020年 | 4篇 |
2019年 | 8篇 |
2018年 | 4篇 |
2017年 | 7篇 |
2016年 | 16篇 |
2015年 | 6篇 |
2014年 | 6篇 |
2013年 | 13篇 |
2012年 | 12篇 |
2011年 | 8篇 |
2010年 | 14篇 |
2009年 | 11篇 |
2008年 | 11篇 |
2007年 | 10篇 |
2006年 | 12篇 |
2005年 | 10篇 |
2004年 | 5篇 |
2003年 | 9篇 |
2002年 | 7篇 |
2001年 | 2篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 7篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1969年 | 1篇 |
1968年 | 3篇 |
1963年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有260条查询结果,搜索用时 15 毫秒
101.
102.
Mosselhi A. N. Mosselhi Magda A. Abdallah Sayed M. Riyadh Abdelhamid E. Harhash Ahmad S. Shawali 《Advanced Synthesis \u0026amp; Catalysis》1998,340(2):160-164
The acid dissociation constants (Ka) of a series of 3,4-diaryl-1H-1,2,4-triazole-5-thiones ( 1 ) were determined and were found to correlated linearly with Hammett substituent constants; log Ka = 1.06 σx − 11.01. Such a result indicates that 1 exists essentially in one tautomeric form namely the thione form. Reactions of 1 with hydrazonoyl chlorides 2 gave the thiohydrazides 5 . Similiar reaction of 3-phenyl-1H(4H)- 1,2,4-triazole-5-thione 1g with 2a gave the thiohydrazide 5h which was converted into 1,3,5-triphenyl-1,2,4-triazolo[3,4-c]-1,2,4-triazole ( 9 ). The latter was also prepared from 3-phenyl-5-methylthio-4H-1,2,4-triazole ( 6 ) and 2a . The mechanism of the reaction of 1 with 2 is discussed. 相似文献
103.
104.
In this paper, the effects of digital transmission errors on H.263 codecs are analyzed and the transmission of H.263 coded video over a TDMA radio link is investigated. The impact of channel coding and interleaving on video transmission quality is simulated for different channel conditions. Fading on radio channels causes significant transmission errors and H.263 coded bit streams are very vulnerable to erros. Powerful Forward Error Correction (FEC) codes are therefore necessary to protect the data so that it can be successfully transmitted at acceptable signal power levels. FEC, however, imposes a high bandwidth overhead. In order to make best use of the available channel bandwidth and to alleviate the overall impact of errors on the video sequence, a twolayer data partitioning and unequal error protection scheme based on H.263 is also studied. The scheme can tolerate more transmission errors and leads to more graceful degradation in quality when the channel SNR decreases. In lossy environments, it can improve the video transmission quality at no extra bandwidth cost.Part of this paper was presented at IS&T/SPIE Symposium on Electronic Imaging, San Jose, CA, USA, January 1996. 相似文献
105.
106.
The changes in the volatile components of three butter samples were studied during freeze storage for 7.5 months. The amount of carbonyl increased and reached a maximum after 4.5 months of storage. Afterwards the carbonyl decreased. The lactons reached its maximum after storage of 3 month. The increase of the carbonyls caused by peroxidation of unsaturated fatty acids was taken as indication for the deterioration of the butter samples during storage. 相似文献
107.
Measurement Techniques - 相似文献
108.
Power quality affects teacher wellbeing and student behavior in three Minnesota Schools 总被引:1,自引:0,他引:1
BACKGROUND: Poor power quality (dirty electricity) is ubiquitous especially in schools with fluorescent lights and computers. Previous studies have shown a relationship between power quality and student behavior/teacher health. OBJECTIVES: The purpose of this study is to determine the ability of power line filters to reduce dirty electricity in a school environment and to document changes in health and behavior among teachers and students. METHOD: We installed Graham Stetzer filters and dummy filters and measured power quality in three Minnesota Schools. Teachers completed a daily questionnaire regarding their health and the behavior of their students for an 8-week period. Teachers were unaware of which filters were installed at any one time (single blind study). RESULTS: Dirty electricity was reduced by more than 90% in the three schools and during this period teacher health improved as did student behavior in the middle/elementary schools. Headaches, general weakness, dry eyes/mouth, facial flushing, asthma, skin irritations, overall mood including depression and anxiety improved significantly among staff. Of the 44 teachers who participated 64% were better, 30% were worse, and 6% did not change. Behavior of high school students did not improve but elementary/middle school students were more active in class; more responsive, more focused; had fewer health complaints; and had a better overall learning experience. CONCLUSIONS: Dirty electricity in schools may be adversely affecting wellbeing of teachers and behavior of their students, especially younger students in middle and elementary school. Power line filters improve power quality and may also protect those who are sensitive to this energy. Work on electric and magnetic field metrics with and without Stetzer filters urgently needs to be carried out to determine just what characteristics of the dirty electricity may be interacting with the people. 相似文献
109.
Gardini D Dondi M Costa AL Matteucci F Blosi M Galassi C Baldi G Cinotti E 《Journal of nanoscience and nanotechnology》2008,8(4):1979-1988
Nano-sized ceramic inks suitable for ink-jet printing have been developed for the four-colours CMYK (cyan, magenta, yellow, black) process. Nano-inks of different pigment composition (Co(1-x)O, Au(0), Ti(1-x-y)Sb(x)Cr(y)O2, CoFe2O4) have been prepared with various solid loadings and their chemicophysical properties (particle size, viscosity, surface tension, zeta-potential) were tailored for the ink-jet application. The pigment particle size is in the 20-80 nm range. All these nano-suspensions are stable for long time (i.e., several months) due to either electrostatic (high zeta-potential values) or steric stabilization mechanisms. Both nanometric size and high stability avoid problems of nozzle clogging from particles agglomeration and settling. Nano-inks have a Newtonian behaviour with relatively low viscosities at room temperature. More concentrated inks fulfil the viscosity requirement of ink-jet applications (i.e., < 35 mPa x s) for printing temperatures in between 30 and 70 degrees C. Surface tension constraints for ink-jet printing are fulfilled by nano-inks, being in the 35-45 mN x m(-1) range. The nano-sized inks investigated behave satisfactorily in preliminary printing tests on several unfired industrial ceramic tiles, developing saturated colours in a wide range of firing temperatures (1000-1200 degrees C). 相似文献
110.
Milena Rondón-Lagos Victoria E. Villegas Nelson Rangel Magda Carolina Sánchez Peter G. Zaphiropoulos 《International journal of molecular sciences》2016,17(8)
17β-Estradiol (E2) plays a pivotal role in the development and progression of breast cancer. As a result, blockade of the E2 signal through either tamoxifen (TAM) or aromatase inhibitors is an important therapeutic strategy to treat or prevent estrogen receptor (ER) positive breast cancer. However, resistance to TAM is the major obstacle in endocrine therapy. This resistance occurs either de novo or is acquired after an initial beneficial response. The underlying mechanisms for TAM resistance are probably multifactorial and remain largely unknown. Considering that breast cancer is a very heterogeneous disease and patients respond differently to treatment, the molecular analysis of TAM’s biological activity could provide the necessary framework to understand the complex effects of this drug in target cells. Moreover, this could explain, at least in part, the development of resistance and indicate an optimal therapeutic option. This review highlights the implications of TAM in breast cancer as well as the role of receptors/signal pathways recently suggested to be involved in the development of TAM resistance. G protein—coupled estrogen receptor, Androgen Receptor and Hedgehog signaling pathways are emerging as novel therapeutic targets and prognostic indicators for breast cancer, based on their ability to mediate estrogenic signaling in ERα-positive or -negative breast cancer. 相似文献