全文获取类型
收费全文 | 1350篇 |
免费 | 45篇 |
国内免费 | 73篇 |
专业分类
电工技术 | 35篇 |
综合类 | 63篇 |
化学工业 | 68篇 |
金属工艺 | 226篇 |
机械仪表 | 82篇 |
建筑科学 | 54篇 |
能源动力 | 15篇 |
轻工业 | 464篇 |
水利工程 | 21篇 |
武器工业 | 1篇 |
无线电 | 56篇 |
一般工业技术 | 171篇 |
冶金工业 | 22篇 |
原子能技术 | 26篇 |
自动化技术 | 164篇 |
出版年
2022年 | 7篇 |
2021年 | 14篇 |
2020年 | 10篇 |
2019年 | 17篇 |
2018年 | 12篇 |
2016年 | 10篇 |
2015年 | 11篇 |
2014年 | 53篇 |
2013年 | 238篇 |
2012年 | 79篇 |
2011年 | 114篇 |
2010年 | 71篇 |
2009年 | 90篇 |
2008年 | 42篇 |
2007年 | 38篇 |
2006年 | 56篇 |
2005年 | 25篇 |
2004年 | 44篇 |
2003年 | 25篇 |
2002年 | 15篇 |
2001年 | 12篇 |
2000年 | 11篇 |
1999年 | 9篇 |
1998年 | 21篇 |
1997年 | 69篇 |
1996年 | 15篇 |
1995年 | 10篇 |
1994年 | 6篇 |
1993年 | 15篇 |
1992年 | 15篇 |
1991年 | 26篇 |
1990年 | 24篇 |
1989年 | 8篇 |
1988年 | 15篇 |
1987年 | 12篇 |
1986年 | 16篇 |
1985年 | 11篇 |
1984年 | 8篇 |
1983年 | 18篇 |
1982年 | 14篇 |
1981年 | 13篇 |
1980年 | 17篇 |
1979年 | 18篇 |
1978年 | 14篇 |
1977年 | 8篇 |
1976年 | 14篇 |
1975年 | 15篇 |
1974年 | 9篇 |
1957年 | 7篇 |
1956年 | 5篇 |
排序方式: 共有1468条查询结果,搜索用时 890 毫秒
41.
This empirical study utilized concrete financial/accounting data concerning measures of organizational performance, as reported in Standard & Poors Compustat, to examine the impact of Just-in-Time production on organizational performance. Matching groups of JIT implementing and non-implementing firms were formed from a cross sectional survey, and a comparative analysis was made for the two groups. The result of the study shows that JIT firms have not achieved better organizational performance in terms of sales in $/employee, operating profit margin, and return on investment than non-JIT firms; but achieved better performances in terms of finished goods inventory turnover, raw materials inventory turnover, and work in process inventory turnover. In addition, this study ascertained that JIT firms have achieved much better performance in terms of quality and flexibility than non-JIT firms. 相似文献
42.
43.
44.
The effect of addition of single and binary additives on the performance of dye-sensitized TiO2 solar cells based on electrolytes containing an ionic liquid (IL), 1,2-dimethyl-3-propylimidazolium iodide (DMPII) has been studied. Among the seven additives used, the addition of 2-(dimethylamino)-pyridine (DMAP) to IL resulted in best cell efficiency, which showed further enhancement with the addition of 5-chloro-1-ethyl-2-methylimidazole (CEMI) as second additive. The efficiency of the dye-sensitized solar cell (DSC) based on an electrolyte containing binary additives (DMAP and CEMI in equal molar ratios) has been found to increase by 62·5% from 4·35 to 7·07%. The dependence of different photovoltaic performance parameters (V oc, J sc, ff, η) of DSC upon temperature has been studied over a 30–120°C range and only a small decrease in conversion efficiency has been observed. The electrolyte containing binary additives (DMAP and CEMI) shows best cell performance up to 120°C. 相似文献
45.
A generalized transportation model is first formulated for the scheduling of Surface Mount Technology (SMT) production. Its dual form is next discussed. By specially coding the SMT scheduling problem, it is unnecessary to develop the constraint matrix for the dual. The simplex method is not applicable for this problem due to its sparse data structure. An efficient algorithm for the dual model is then developed from the idea of the revised simplex method. To illustrate the algorithm, a numeric example is presented. 相似文献
46.
IGOR VOJNOVIC ZEENAT KOTVAL‐K JIEUN LEE MINTING YE TIMOTHY LEDOUX PARIWATE VARNAKOVIDA JOSEPH MESSINA 《Journal of Urban Affairs》2014,36(2):225-255
The research explores the impact of socioeconomic and racial variables on accessibility to urban amenities and travel in compact urban built environments that have traditionally been viewed as improving access to daily destinations and promoting nonmotorized travel: urban environments characterized by high densities, mixed land uses, and high connectivity. The study focuses on six neighborhoods in the Detroit region. Two neighborhoods are within the city itself, and predominantly poor and Black, and four of the neighborhoods are in the region surrounding the city, and they are predominantly wealthy and White. This study at the neighborhood scale enables an analysis into how class and race affect accessibility and travel in neighborhoods experiencing urban disinvestment and decline. The research shows that the traditional relationship between high densities, mixed land uses, high connectivity, greater accessibility, and pedestrian activity is significantly weaker in declining inner cities. 相似文献
47.
Wetting phenomena between MgO C and CaO SiO2 slags were investigated by varying carbon content.A sessile drop technique was adopted to study the wetting phenomena in conjunction with a high speed camera for the observation of intrinsic wetting phenomena.The results show that the high content of SiO2 and the presence of Al2O3 in slags enhance the diffusion of Mg2+,leading to the promotion of reactive wetting.The carbon in MgO C refractory impedes the penetration of slags by repelling the slag and slowing the diffusion of Mg2+.This accounts for the non-wetting behavior of the slag on MgO C refractory with 17% (mass fraction) carbon similar to that of graphite. 相似文献
48.
49.
50.
The crystallization process of the eutectic composition of GdAlO_3-Al_2O_3 from the amorphous phase prepared by rapid-quenching of melt that leads to the formation of a cantaloupe skin-like microstructure was investigated using focused ion-beam scanning electron microscopy (FIB-SEM) and high-resolution transmission electron microscopy (HR-TEM).The amorphous films were heat-treated at temperatures between 1000 °C and 1500 °C for up to 30min to form the eutectic phases of GdAlO_3 and Al_2O_3.The GdAlO_3 and Al_2O_3 crystal phases that formed from the amorphous phase were identified by FIB-SEM and HR-TEM.Both components began to crystallize and grow from the amorphous phase separately at different temperatures.The formation process of these crystal phases was different from that of the ordinary eutectic microstructure solidified from the GdAlO_3-Al_2O_3 system.Therefore,the observed structure is termed "eutectic-like" for distinction.The microstructures formed from the amorphous phases at sufficiently high temperatures consisted of ultra-fine microstructures of individually crystallized components and were similar to ordinary eutectic microstructures.By heat-treating the amorphous films at 1500 °C for either 2 min,8min or 30min,the ultra-fine components of GdAlO_3 and Al_2O_3 were found to crystallize following a eutectic-like stage after 8min of heat treatment. 相似文献