全文获取类型
收费全文 | 2104篇 |
免费 | 193篇 |
国内免费 | 14篇 |
学科分类
工业技术 | 2311篇 |
出版年
2023年 | 16篇 |
2022年 | 10篇 |
2021年 | 48篇 |
2020年 | 38篇 |
2019年 | 61篇 |
2018年 | 41篇 |
2017年 | 62篇 |
2016年 | 73篇 |
2015年 | 60篇 |
2014年 | 97篇 |
2013年 | 196篇 |
2012年 | 113篇 |
2011年 | 128篇 |
2010年 | 114篇 |
2009年 | 123篇 |
2008年 | 92篇 |
2007年 | 112篇 |
2006年 | 88篇 |
2005年 | 62篇 |
2004年 | 61篇 |
2003年 | 43篇 |
2002年 | 52篇 |
2001年 | 41篇 |
2000年 | 35篇 |
1999年 | 47篇 |
1998年 | 79篇 |
1997年 | 55篇 |
1996年 | 51篇 |
1995年 | 26篇 |
1994年 | 29篇 |
1993年 | 31篇 |
1992年 | 20篇 |
1991年 | 38篇 |
1990年 | 22篇 |
1989年 | 18篇 |
1988年 | 17篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 13篇 |
1984年 | 4篇 |
1983年 | 11篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1976年 | 11篇 |
1974年 | 3篇 |
1973年 | 6篇 |
排序方式: 共有2311条查询结果,搜索用时 187 毫秒
101.
Kuo-chung Chang Hung-Wei Yen Chih-Ching Chiang Neeraj Parolia 《International Journal of Project Management》2013
The extent of knowledge contribution is the key to the success of system development projects. Knowledge contribution refers to the knowledge that is provided to increase a team's efficiency and achieve its goal. This study proposes a research model exploring factors that influence the extent of knowledge contribution from a social cognitive perspective. These factors include the team relationship commitment, team relationship norms, and awareness of expertise location. Additionally, this study argues that a team's awareness of expertise location mediates the effects of affective commitment and relationship norms on knowledge contribution. The result shows that the awareness of expertise location plays a crucial mediating role in the relationships between the two socially prescribed motivations and knowledge contribution. Moreover, team relationship commitment has an important impact on team established relational norms. 相似文献
102.
Hsing Yuan Yen 《臭氧:科学与工程》2016,38(2):163-171
This study evaluated the feasibility of treating color filter effluent by H2O2/UV pre-oxidation and membrane postseparation for in-house reuse. The effluent qualities were TOC of 5.8–34 mg/L, color of 46–138 ADMI, and conductivity of 1020–3500 μS/cm. Although the RO separation could directly remove TOC, color, and conductivity effectively, the serious fouling problem still existed. Through H2O2/UV pre-oxidation (UV = 13 W, H2O2 = 200 mg/L), organic and biofouling were inhibited to increase the normalized flux decline from 5% to 77%. That is, H2O2/UV pre-oxidation could mitigate the permeate flux decline as well as to improve the water quality for water reuse. 相似文献
103.
从硫脲浸出液中活性炭负载洗脱金是比较困难的,目前在这方面发表的文献并不很多。本文着重研究并讨论了从负载活性炭上洗脱金的不同方法,包括酸性硫脲有机溶液和非有机洗脱液。研究了丙酮、乙腈、丁醇、乙二醚和乙醇5种有机溶剂。研究了不同的硫脲、硫酸和有机溶剂的浓度和温度对洗脱的影响。试验表明了这5种有机溶剂对金的洗脱能力按如下顺序排列: 丁醇>乙腈>乙二醚>乙醇>丙酮当采用5%丁醇,50~100g/L硫脲和50~100g/L硫酸,温度40~60℃时,金的洗脱率可达98~99%,此时活性炭含金降至0.10mg/g以下。对于非有机洗脱液,像硫化钠和硫代硫酸钠,研究表明金的洗脱率主要取决于溶液的浓度和温度,在室温时,1~2mol的硫化钠溶液可以洗脱99%的金。如果溶液的浓度降低至0.5mol,则温度需升至80℃以上才可能获得相同的洗脱率。 相似文献
104.
煤矿生产能力核定工作是当前煤炭行业一项重要的工作。通过对煤矿生产能力核定工作中存在的问题和不足之处提出针对性对策,为煤矿生产能力核定工作更好的开展、标准的更加完善提供科学依据。 相似文献
105.
Ha Vu Thi Thu Nguyen Manh B. Tam Tran Nhu Thu Vu Thi Yen Pham Thi Hai Phong Pham Hong Nhiem Dao Ngoc Hung Le Quoc Hai Tran Quang 《Journal of Applied Electrochemistry》2022,52(3):607-616
Journal of Applied Electrochemistry - In this study, a sensitive and selective electrochemical sensor based on a zirconia oxide-decorated gold nanoflake nanocomposite-modified glassy carbon... 相似文献
106.
Poly(ethylene terephthalate)/poly(ethylene glycol‐co‐1,3/1,4‐cyclohexanedimethanol terephthalate)/clay nanocomposites: Mechanical properties,optical transparency,and barrier properties 下载免费PDF全文
Poly(ethylene terephthalate) (PET)/clay, PET/poly(ethylene glycol‐co‐1,3/1,4‐cyclohexanedimethanol terephthalate) (PETG), and PET/PETG/clay nanocomposites were fabricated using the twin‐screw extrusion technique. The spherulitic morphologies, thermomechanical, mechanical, and gas‐barrier properties, as well as the effect of clay on the transparency of the resulting nanocomposites were identified. The clay induced the heterogeneous nucleation of the nanocomposites during the cold crystallization process, thereby increasing the crystallinities and melting temperatures of the resulting nanocomposites. The incorporation of clay increased the storage moduli, Young's moduli, impact strengths, and barrier properties of the PET, PETG, and PET/PETG blend. Regarding the optical transparency, the inclusion of clay can make the crystallizable PET matrix crystalline opaque. However, the amorphous PETG maintained its transparency. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39869. 相似文献
107.
Bonnie Yen Ping Tay Zulina Maurad Halimah Muhammad 《Journal of the American Oil Chemists' Society》2014,91(7):1103-1110
During the ethoxylation of fatty alcohol, 1,4-dioxane, a toxic by-product may be formed. A simple and rapid method using gas chromatography with a flame ionization detector was developed for detection of 1,4-dioxane in commercial palm-based fatty alcohol ethoxylate (FAEO). The method involved spiking the 1,4-dioxane into FAEO samples, and directly injecting the spiked samples into GC with no clean-up steps. The method was validated in terms of linearity, accuracy, intra-day precision and inter-day precision, selectivity, limit of detection and limit of quantification. In terms of linearity, a calibration curve with a correlation coefficient of 0.9999 was obtained. The accuracy of the method was indicated by recovery obtained for spiked 1,4-dioxane samples at 5 levels of spiking, i.e. at 30, 60, 100, 200 and 500 μg/g, where recoveries were within 99–105 % with relative standard deviation (RSD) of <4.0 %. The RSD values of the intra-day and inter-day precision were <1.0 %. The limit of detection and quantification was 10 and 30 μg/g, respectively. The selectivity of the method was indicated by its ability to analyze commercial FAEO samples with different average moles of ethylene oxide (EO). The GC profiles of these FAEO with varying numbers of moles of EO were similar, and there were no other peaks interfering with the 1,4-dioxane peak. 相似文献
108.
109.
Upward-closed sets of integer vectors enjoy the merit of having a finite number of minimal elements, which is behind the decidability of a number of Petri net related problems. In general, however, such a finite set of minimal elements may not be effectively computable. In this paper, we develop a unified strategy for computing the sizes of the minimal elements of certain upward-closed sets associated with Petri nets. Our approach can be regarded as a refinement of a previous work by Valk and Jantzen (in which a necessary and sufficient condition for effective computability of the set was given), in the sense that complexity bounds now become available provided that a bound can be placed on the size of a witness for a key query. The sizes of several upward-closed sets that arise in the theory of Petri nets as well as in backward-reachability analysis in automated verification are derived in this paper, improving upon previous decidability results shown in the literature. 相似文献
110.
The temporal effect of hydrograph on local scour depth is investigated under clear-water scour condition. By analyzing the characteristics of scour-depth evolutions at bridge piers for different rising hydrographs, a relation for estimating the maximum scour depth in uniform sediment is proposed. In the relation, the flow unsteadiness effect is taken into account by an unsteady flow parameter combining the peak-flow intensity and time-to-peak factors. For nonuniform sediment with d84 employed as the effective sediment size, this relation can yield reasonably good results of the maximum scour depth under rising hydrograph. 相似文献