全文获取类型
收费全文 | 596篇 |
免费 | 21篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 59篇 |
化学工业 | 124篇 |
金属工艺 | 14篇 |
机械仪表 | 8篇 |
建筑科学 | 23篇 |
能源动力 | 17篇 |
轻工业 | 35篇 |
水利工程 | 1篇 |
无线电 | 39篇 |
一般工业技术 | 87篇 |
冶金工业 | 139篇 |
原子能技术 | 27篇 |
自动化技术 | 50篇 |
出版年
2022年 | 8篇 |
2021年 | 17篇 |
2020年 | 3篇 |
2019年 | 8篇 |
2018年 | 21篇 |
2017年 | 7篇 |
2016年 | 16篇 |
2015年 | 9篇 |
2014年 | 10篇 |
2013年 | 27篇 |
2012年 | 23篇 |
2011年 | 35篇 |
2010年 | 20篇 |
2009年 | 20篇 |
2008年 | 24篇 |
2007年 | 16篇 |
2006年 | 20篇 |
2005年 | 18篇 |
2004年 | 12篇 |
2003年 | 12篇 |
2002年 | 8篇 |
2001年 | 4篇 |
2000年 | 9篇 |
1999年 | 12篇 |
1998年 | 54篇 |
1997年 | 28篇 |
1996年 | 26篇 |
1995年 | 13篇 |
1994年 | 12篇 |
1993年 | 9篇 |
1992年 | 7篇 |
1991年 | 9篇 |
1990年 | 10篇 |
1989年 | 6篇 |
1988年 | 12篇 |
1987年 | 5篇 |
1986年 | 14篇 |
1985年 | 8篇 |
1984年 | 2篇 |
1982年 | 2篇 |
1981年 | 5篇 |
1980年 | 12篇 |
1979年 | 5篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1975年 | 2篇 |
1974年 | 5篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1957年 | 1篇 |
排序方式: 共有623条查询结果,搜索用时 781 毫秒
81.
82.
Toshihiro Itoh Toshitake Tamura Taro Matsumoto 《Journal of the American Oil Chemists' Society》1973,50(8):300-303
The unsaponifiables from 19 vegetable oils were divided into 4-methylsterol fraction, triterpene alcohol fraction and two
other fractions by thin layer chromatography. The 4-methylsterol and triterpene alcohol fractions were analyzed by gas liquid
chromatography, and identification of major components was carried out by gas liquid chromatography and combined gas chromatography-mass
spectrometry. Gramisterol(24-methylenelophenol), citrostadienol and obtusifoliol were present in all oils, and the presence
of a 4-methylsterol, presumably cycloeucalenol, was indicated in most of the oils. Cycloartenol and 24-methylenecycloartanol
were found as common triterpene alcohols in all oils, and the occurrence of cyclobranol(24-methylcycloartenol), cycloartanol,
and α- and β-amyrins was demonstrated in most of the oils. 相似文献
83.
Large amounts of smoke and toxic gases, generated at the beginning of a fire and spreading rapidly through a building, result in the death of individuals. In order to keep casualties to the minimum, it is necessary to prevent the diffusion of smoke or toxic gas. Fire-doors or fire-screens are available for this purpose, but these create obstructions to exits.In this paper, the air shutter, dependent upon the push-pull principle, which has the effect of controlling the air flow of the surrounding area, is suggested as a means of defence against fire. The function of the air shutter is closely examined, and a theoretical and experimental investigation of the effect of smoke flow on the shutter has been undertaken.As a consequence of this investigation, it is clear that the air shutter is very effective in excluding smoke or toxic gas, and it might prove to be a practical proposition. 相似文献
84.
85.
DW Cramer MG Muto JK Reichardt H Xu WR Welch B Valles WG Ng 《Canadian Metallurgical Quarterly》1994,74(4):1309-1317
BACKGROUND: Galactose metabolism may be a risk factor for ovarian cancer based upon evidence that galactose causes ovarian failure and that ovarian cancer arises from premature ovarian failure. This study examines galactose-1-phosphate uridyl transferase (GALT) activity in women with a family history of ovarian cancer (FOC) to determine if low GALT activity occurs in women who are at risk for but in whom ovarian cancer has not yet developed. METHODS: The authors studied 106 premenopausal women (FOC patients) with one primary or two second-degree relatives with ovarian cancer compared with 116 age matched control subjects without a family history of ovarian cancer (FOC controls). All women completed questionnaires and had blood drawn to measure GALT activity and genotype. RESULTS: Mean erythrocyte GALT activity, in micromoles of hexose conversion per hour per gram of hemoglobin was 21.5 in FOC patients, significantly lower than the mean of 23.1 observed in FOC control subjects, (P = 0.001). FOC patients more frequently displayed the Duarte variant of galactosemia as detected by electrophoresis. In a subset of 87 patients and 113 control subjects for whom DNA was available, the allelelic frequency of the Duarte variant based upon molecular genetic detection of the N314D mutation that is associated with the Duarte variant was 15.5% among FOC cases compared with 7.5% among control subjects (P < 0.02). Galactose consumption did not differ between FOC patients and control subjects. CONCLUSION: Galactose metabolism differs between women with and without a family history of ovarian cancer, suggesting that it may be a genetic risk factor for ovarian cancer, possibly mediated through oocyte toxicity from galactose. 相似文献
86.
This paper presents a regression based daily peak load forecasting method with a transformation technique. In order to forecast the load precisely through a year, one should consider seasonal load change, annual load growth and the latest daily load change. To deal with these characteristics in the load forecasting, a transformation technique is presented. This technique consists of a transformation function with translation and reflection methods. The transformation function is estimated with the previous year's data points, in order that the function converts the data points into a set of new data points with preservation of the shape of temperature-load relationships in the previous year. Then, the function is slightly translated so that the transformed data points will fit the shape of temperature-load relationships in the year. Finally, multivariate regression analysis, with the latest daily loads and weather observations, estimates the forecasting model. Large forecasting errors caused by the weather-load nonlinear characteristic in the transitional seasons such as spring and fall are reduced. Performance of the technique which is verified with simulations on actual load data of Tokyo Electric Power Company is also described 相似文献
87.
Hiromichi Akahori Stéphane Guindon Sumio Yoshizaki Yoshinori Muto 《International journal of molecular sciences》2015,16(12):28472-28485
Ten-eleven translocation (TET) proteins, a family of Fe2+- and 2-oxoglutarate-dependent dioxygenases, are involved in DNA demethylation. They also help regulate various cellular functions. Three TET paralogs have been identified (TET1, TET2, and TET3) in humans. This study focuses on the evolution of mammalian TET genes. Distinct patterns in TET1 and TET2 vs. TET3 were revealed by codon-based tests of positive selection. Results indicate that TET1 and TET2 genes have experienced positive selection more frequently than TET3 gene, and that the majority of codon sites evolved under strong negative selection. These findings imply that the selective pressure on TET3 may have been relaxed in several lineages during the course of evolution. Our analysis of convergent amino acid substitutions also supports the different evolutionary dynamics among TET gene subfamily members. All of the five amino acid sites that are inferred to have evolved under positive selection in the catalytic domain of TET2 are localized at the protein’s outer surface. The adaptive changes of these positively selected amino acid sites could be associated with dynamic interactions between other TET-interacting proteins, and positive selection thus appears to shift the regulatory scheme of TET enzyme function. 相似文献
88.
DRY MACHINING is a keyword for manufacturingand production science in the twenty-first century,which requires significant reduction of environmentalburden and COi emission11.In the modern high-speedwet and semi-dry machining processes,huge amountsof lubricants and cleansing agents are wasted in dailyproduction2).Among various proposals aiming at thedry machining3"5>,in-situ formation of tribo-filrns mustbe an important concept to make dry machining tools.Authors have pointed out the impor… 相似文献
89.
Taro Kurit Yasumasa Nakatsugawa 《International Journal of Software and Informatics》2009,3(2):343-355
We have applied the formal speci.cation language in the development of the .rmware of the smart card IC chip for embedding in mobile phone. We report on an in-dustrial application of formal methods to the development of a complex system, namely the .rmware for the “Mobile FeliCa” smart card IC chip. The use of formal techniques, specif-ically the Vienna Development Method (VDM), was aimed at raising the quality of system speci.cations by reducing ambiguity and improving communications between engineers. De-velopment data gathered during the life cycle con.rm the e.ectiveness of a lightweight formal method in contributing to the quality of the deliverables in early development stages. No software speci.cation problems have, to date, been reported since .rst release (over 100 million mobile phones have the chip embedded). 相似文献
90.
Baffled membrane bioreactor (BMBR) for efficient nutrient removal from municipal wastewater 总被引:5,自引:0,他引:5
Submerged membrane bioreactors (MBRs) are now widely used for various types of wastewater treatment. One drawback of submerged MBRs is the difficulty in removing nitrogen because intensive aeration is usually carried out in the tank and the MBRs must therefore be operated under aerobic conditions. In this study, the feasibility of treating municipal wastewater by a baffled membrane bioreactor (BMBR), particularly in terms of nitrogen removal, was examined. Simultaneous nitrification/denitrification in a single and small reaction tank was possible by inserting baffles into a normal submerged MBR as long as wastewater was fed in the appropriate way. To examine the applicability of the BMBR, pilot-scale experiments were carried out using real municipal wastewater. Although neither external carbon addition nor mixed liquor circulation was carried out in the operation of the BMBR, average removal rates of total organic carbon (TOC), total phosphorus (T-P) and total nitrogen (T-N) reached 85%, 97% and 77%, respectively, with the hydraulic retention time (HRT) of 4.7h. Permeability of the membrane could be maintained at a high level throughout the operation. It was found that denitrification was the limiting step in removal of nitrogen in the BMBR in this study. Various types of monitoring carried out in the BMBR also demonstrated the possibility of further improvements in its performance. 相似文献