全文获取类型
收费全文 | 20198篇 |
免费 | 1132篇 |
国内免费 | 1538篇 |
学科分类
工业技术 | 22868篇 |
出版年
2024年 | 2篇 |
2023年 | 36篇 |
2022年 | 78篇 |
2021年 | 122篇 |
2020年 | 170篇 |
2019年 | 105篇 |
2018年 | 121篇 |
2017年 | 199篇 |
2016年 | 284篇 |
2015年 | 346篇 |
2014年 | 864篇 |
2013年 | 860篇 |
2012年 | 1205篇 |
2011年 | 1476篇 |
2010年 | 1355篇 |
2009年 | 1448篇 |
2008年 | 1654篇 |
2007年 | 1878篇 |
2006年 | 1915篇 |
2005年 | 1655篇 |
2004年 | 1447篇 |
2003年 | 1281篇 |
2002年 | 1013篇 |
2001年 | 881篇 |
2000年 | 710篇 |
1999年 | 502篇 |
1998年 | 385篇 |
1997年 | 242篇 |
1996年 | 202篇 |
1995年 | 147篇 |
1994年 | 76篇 |
1993年 | 67篇 |
1992年 | 40篇 |
1991年 | 34篇 |
1990年 | 9篇 |
1989年 | 24篇 |
1988年 | 11篇 |
1987年 | 7篇 |
1986年 | 2篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1982年 | 4篇 |
1979年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
《Ceramics International》2022,48(17):24157-24191
Great progress in the development of low-cost ceramic membranes from alternative materials have been achieved recently towards various application especially water and wastewater treatment. However, their significance has not been fully recognized and understood especially in term of their microstructural analysis such as formation of grain growth and microcracks. This review paper summarizes fabrication method, alternative materials, microstructure, wettability, mechanical properties and application of low-cost ceramic membrane. The fabrication method including slip casting, tape casting, extrusion, pressing method and phase inversion technique are described. Alternative materials used in low-cost ceramic membrane fabrication are discussed and categorized into clays, agricultural waste, industrial waste and animal bone waste. The mechanisms of morphology formation, microstructure and wettability properties are analysed. Modification strategies for the surface of low-cost ceramic membrane are discussed, and classified into modification for separation application, modification for photocatalytic application and modification for membrane distillation and membrane contactor system. Modification improves the membrane structure by changing the pore size, porosity and wettability properties of low-cost ceramic membranes. Mechanical properties of low-cost ceramic membranes are also discussed in detail towards several mechanism, like grain growth phenomenon and formation of microcracks which also considered as membrane defects. Grain growth phenomenon can be divided into normal and abnormal grain growth. Meanwhile, formation of microcracks could be occurred in single-phase polycrystalline ceramics that have anisotropic grains or biphasic polycrystalline grains. The application of low-cost ceramic membrane in seawater desalination, oily wastewater treatment, heavy metal adsorption, textile separation and photocatalytic application are reviewed. Finally, some possible opportunities and challenges for further development of low-cost ceramic membrane are pointed out. 相似文献
3.
ABSTRACTNonprofit organizations (NPOs) are strategically using their own personal website to present themselves to the public and share information. Despite the potential benefits of enhanced public confidence and trust, reduced operating costs, improved donor decision making, and increased donations, many nonprofit organizations have resisted the adoption of web disclosure. Informed by the literature on information systems (IS) adoption and technological innovation, this study examines the primary factors that influence the adoption and resistance of web disclosure. Our sample consisted of 176 survey responses from an initial group of 3,323 U.S. NPOs. The statistical results indicate that attitude toward disclosure, compatibility of disclosure with current practices, and financial readiness have a positive influence on web disclosure adoption. The findings have implications for research and practice. 相似文献
4.
5.
巷道掘进超前探查一般采用钻探方法的开展工作,常规回转钻进由于受钻进工艺等影响,存在钻孔施工长度短、影响正常掘进、施工精度较差等问题。而采用长距离掩护式定向钻进工艺开展超前探放水工作,可对掘进头600m范围内进行超前探查,钻孔施工长度较常规回转钻进孔长度增大3~4倍,在不影响掘进的前提下,可通过随钻测斜仪器实时对钻孔轨迹进行调整、监控,从而达到高精度、长距离对掘进前方进行超前探查,较常规超前探放水具有较大的优势[1]。 相似文献
6.
以智能家居系列产品中的无线遥控开关为例,介绍了在“大众创业、万众创新”背景下三维打印技术对产品设计和制造阶段的影响,分析了数模处理、切片、后处理等三维打印工艺,并对三维打印技术未来的发展进行了展望。 相似文献
7.
Feeling thermometer questions are widely used in political science research to estimate people’s attitudes and feelings toward a political object, like a political figure or an organization. Given the popularity of the feeling thermometer question in population surveys, more work is needed to explore the measurement of this question type. This study examines the data collection mode effect on feeling thermometers. Using the 2012 American National Election Studies, we find that the measurement of feeling thermometers is not exactly comparable between face-to-face and Web surveys. Face-to-face respondents tend to provide warmer feelings, while Web respondents give relatively more reliable responses in comparison. In both survey modes, respondents are most likely to select the response options that are verbally labeled although the effect is more striking in face-to-face than Web survey. The item nonresponse between these two modes does not differ in a meaningful way. This study ends by discussing future research directions on feeling thermometer questions. 相似文献
8.
9.
为满足简便检测塑料产品抗冲击强度的需求,研制了垂直冲击试验机。对垂直冲击试验机的结构进行了设计,基于力学原理进行了受力计算,并对工作原理与相对基准设定问题进行了分析。介绍了垂直冲击试验机的操作方法,并进行了规格校验。 相似文献
10.
温拌沥青在使用的过程中可以节省20%~30%的燃料,而且也可以减少污染气体的排放,温拌沥青在使用的过程中拌和温度和摊铺温度都比热拌沥青有所降低,非常适合在寒冷地区的使用,可以缩短施工的时间,延长路面的使用寿命。而作为温拌沥青的上游原材料,辽河石化沥青又有着得天独厚的优势。介绍了温拌沥青的技术特点、温拌沥青的优良性能以及辽河石化沥青的特点等。 相似文献