全文获取类型
收费全文 | 21030篇 |
免费 | 1419篇 |
国内免费 | 706篇 |
专业分类
电工技术 | 565篇 |
综合类 | 2053篇 |
化学工业 | 5779篇 |
金属工艺 | 1101篇 |
机械仪表 | 868篇 |
建筑科学 | 1523篇 |
矿业工程 | 1181篇 |
能源动力 | 230篇 |
轻工业 | 1926篇 |
水利工程 | 327篇 |
石油天然气 | 832篇 |
武器工业 | 147篇 |
无线电 | 655篇 |
一般工业技术 | 2463篇 |
冶金工业 | 1901篇 |
原子能技术 | 140篇 |
自动化技术 | 1464篇 |
出版年
2024年 | 79篇 |
2023年 | 186篇 |
2022年 | 380篇 |
2021年 | 470篇 |
2020年 | 480篇 |
2019年 | 372篇 |
2018年 | 353篇 |
2017年 | 424篇 |
2016年 | 533篇 |
2015年 | 561篇 |
2014年 | 1030篇 |
2013年 | 1035篇 |
2012年 | 1523篇 |
2011年 | 1486篇 |
2010年 | 1176篇 |
2009年 | 1242篇 |
2008年 | 1062篇 |
2007年 | 1556篇 |
2006年 | 1412篇 |
2005年 | 1291篇 |
2004年 | 1088篇 |
2003年 | 1067篇 |
2002年 | 900篇 |
2001年 | 712篇 |
2000年 | 553篇 |
1999年 | 463篇 |
1998年 | 323篇 |
1997年 | 271篇 |
1996年 | 232篇 |
1995年 | 169篇 |
1994年 | 147篇 |
1993年 | 96篇 |
1992年 | 86篇 |
1991年 | 60篇 |
1990年 | 32篇 |
1989年 | 45篇 |
1988年 | 34篇 |
1987年 | 27篇 |
1986年 | 15篇 |
1985年 | 22篇 |
1984年 | 21篇 |
1983年 | 7篇 |
1982年 | 14篇 |
1981年 | 24篇 |
1980年 | 8篇 |
1965年 | 7篇 |
1964年 | 6篇 |
1963年 | 7篇 |
1957年 | 8篇 |
1955年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
ZnO压敏陶瓷最佳掺杂含量的理论计算 总被引:3,自引:0,他引:3
从对电子薄膜材料研究中得到的最佳掺杂含量定量理论推广到ZnO陶瓷材料。该理论建立了电子薄膜材料的某一物理性能与晶体结构、制备方法和掺杂剂含量之间的联系,给出了一个能够拟合实验曲线的具有确定物理意义的抛物线方程。该方程的极值点确定了最佳掺杂含量与晶体结构和制备方法之间的定量关系,进而得到了一个掺杂最佳含量的表达式。系统地分析了ZnO压敏陶瓷的掺杂改性的实验结果,应用此表达式定量计算了ZnO压敏陶瓷的最佳掺杂含量,定量计算的结果与实验数据相符合。该理论也适用于其他薄膜材料最佳掺杂含量的理论计算。 相似文献
52.
53.
54.
Effects of home preparation on pesticide residues in cabbage 总被引:4,自引:0,他引:4
Experiment was carried out to evaluate the pesticides (chlorpyrifos, p,p-DDT, cypermethrin, chlorothalonil) residue levels in cabbage in the process of home preparation by washing with different concentrations of acetic acid and sodium chlorine, and tap water, preserving in refrigerator, and stir-frying for different time. Results showed that washing by tap water and/or detergent solution for cooking are necessary to decrease the concentration of pesticide residues in cabbage. Washing with acetic acid solutions (at 10% concentration for 20 min) caused 79.8%, 65.8%, 74.0% and 75.0% loss of the above pesticides, respectively. Washing with NaCl solutions (at 10% concentration for 20 min) produced 67.2%, 65.0%, 73.3% and 74.1% loss, respectively, and washing by tap water (for 20 min) were 17.6%, 17.1%, 19.1% and 15.2% loss, respectively. The reductions due to the refrigeration (for 48 h) were 3.4%, 2.6%, 3.1% and 3.6%, respectively, and those due to the stir-frying (for 5 min) were 86.6%, 67.5%, 84.7% and 84.8%, respectively. The data indicated that washing by detergent solutions and stir-frying of cabbage are the most effective home preparations for the elimination of pesticide residues. 相似文献
55.
Acceptance, the willingness to experience thoughts, feelings, and physiological sensations without having to control them or let them determine one's actions, is a major individual determinant of mental health and behavioral effectiveness in a more recent theory of psychopathology. This 2-wave panel study examined the ability of acceptance also to explain mental health, job satisfaction, and performance in the work domain. The authors hypothesized that acceptance would predict these 3 outcomes 1 year later in a sample of customer service center workers in the United Kingdom (N = 412). Results indicated that acceptance predicted mental health and an objective measure of performance over and above job control, negative affectivity, and locus of control. These beneficial effects of having more job control were enhanced when people had higher levels of acceptance. The authors discuss the theoretical and practical relevance of this individual characteristic to occupational health and performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
56.
阐述静态电子轨道衡诸多优点;工作原理、允许误差及误差分配;轨道衡的结构组成部分、解析各部分的工作特性及技术指标要求;合理选配及推荐实例. 相似文献
57.
将富于变化的女红工艺与单调的针织服装相结合,会使针织服装由平淡变为丰富,由呆板变为活泼。文章论述了在针织服装中运用女红图案、色彩、材料、针法的原理。 相似文献
58.
液体酚型抗氧剂的制备及性能评定 总被引:1,自引:0,他引:1
以2,6-二叔丁基苯酚和丙烯酸酯为主要原料制备出一种液体酚型抗氧剂新产品羟基苯基丙酸酯化合物(LA0)。对制备的LAO的结构、组成及理化性能特别是抗氧化性能进行了分析评定。结果表明:LAO具有油溶性好、使用方便、特别是高温抗氧化能力强等优点,质量达到国外同类优质产品水平,并具有良好的环保性。 相似文献
59.
Preparation of Compound Ultrafine CeO2 by Wet-Solid-Phase Mechanochemical Modification 总被引:1,自引:0,他引:1
To satisfy practical requirements from industrial applications, an alternate route for synthesis compound ultrafine CeO2 powders by wet-solid-phase mechanochemical modification using industrial grade hydrated cerium carbonate as raw material was proposed.The effect of modifier reaction percentage, reaction time, calcining temperature and modifier amount on particle size, density, suspensibility, and hardness of compound CeO2 powder was investigated.The phase evolutions of preparation process were characterized by XRD.SEM micrograph of the final product shows that compound CeO2 powders obtained are well-dispersed, spherically-shaped, uniformly-sized and submicron-sized particles.The method is readily available in raw material, low in cost, simple in process, and has great potential for industrialization.The compound CeO2 powders of different physical properties can be synthesized by controlling the above-mentioned influence factors in preparation process. 相似文献
60.