首页 | 官方网站   微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   49610篇
  免费   2910篇
  国内免费   1416篇
工业技术   53936篇
  2024年   175篇
  2023年   456篇
  2022年   1129篇
  2021年   1340篇
  2020年   1267篇
  2019年   881篇
  2018年   905篇
  2017年   1180篇
  2016年   1236篇
  2015年   1404篇
  2014年   2617篇
  2013年   2502篇
  2012年   3354篇
  2011年   3594篇
  2010年   3043篇
  2009年   3157篇
  2008年   2430篇
  2007年   3342篇
  2006年   3294篇
  2005年   2827篇
  2004年   2416篇
  2003年   2250篇
  2002年   1824篇
  2001年   1429篇
  2000年   1154篇
  1999年   934篇
  1998年   722篇
  1997年   590篇
  1996年   469篇
  1995年   404篇
  1994年   306篇
  1993年   220篇
  1992年   213篇
  1991年   157篇
  1990年   111篇
  1989年   134篇
  1988年   82篇
  1987年   70篇
  1986年   50篇
  1985年   55篇
  1984年   49篇
  1983年   39篇
  1982年   20篇
  1981年   7篇
  1980年   6篇
  1979年   5篇
  1966年   9篇
  1965年   7篇
  1964年   9篇
  1959年   7篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
The technological properties of the hot-work tool steels depend on their microstructural quality induced by the production process and the heat treatment. One of the frequently applied methods to improve microstructure is preheat treatment. The treatment of carbonitriding X37CrMoV5-1 steel has been investigated in fluidized bed furnaces. Thickness and phase composition have been conducted using optical microscopy Neophot 32 and scanning microscopy, JEOL 5400, after etching in nital.  相似文献   
32.
节能降耗提高矿山效益   总被引:1,自引:0,他引:1  
节能降耗是每一个矿山提高经济效益的有效途径。我们采取提高球磨机处理能力,降低单耗;利用“分时计价”政策,采用“避峰作业”;使用新设备等措施节能降耗,提高矿山经济效益。  相似文献   
33.
李长智  郭杰 《纺织器材》2003,30(5):46-49
论述了普通胶辊表面不处理的性能特点和存在问题,技术措施和合理工艺参数,提高了成纱条干水平,减少缠绕和磨损。  相似文献   
34.
化学成分和固溶温度对1Cr17Mn9Ni4N不锈钢组织和性能的影响   总被引:3,自引:1,他引:2  
为提高1Crl7Mn9Ni4N钢固溶处理后的力学性能(特别是钢的强度),研究了化学成分及固溶处理温度对其组织和性能的影响。结果表明,1000—1125℃固溶处理后,该钢的组织为单相奥氏体。在标准成分范围内,随着镍、锰含量的增加,该钢的强度降低,塑性有所改善。氮明显提高该钢的强度。根据试验结果,每增加0.01%的氮钢的室温强度可提高大约5MPa,且塑性基本上不受影响。当合金成分(质量分数,%)控制在C0.08—0.12、Crl6.5—17.5、Ni3.5—4.2、Mn8.0—9.0、N0.22—0.28时,1Crl7Mn9Ni4N钢经1050—1100℃固溶处理后强度较高、塑性好,室温强度σ0.2和σb可分别达到400MPa和800MPa。  相似文献   
35.
The rationale for utilizing filial therapy as a treatment intervention with child witnesses of domestic violence while residing with their mothers in a shelter facility is explored and the effectiveness of an intensive 12-session filial therapy parent training group, conducted within 2-3 weeks, is described (n=11; aged 4-10 yrs). Results of analysis of covariance revealed that child witnesses in the experimental group significantly reduced behavior problems prevalent in child witnesses and significantly increased their self-concept as compared to child witnesses in the non-treatment comparison group. In addition, t-test results showed that mothers who facilitated treatment of the experimental group scored significantly higher after training on both their attitudes of acceptance and their empathic behavior. Comparative analysis revealed that intensive filial therapy as facilitated by the children's mothers was as effective in reducing behavior problems as was intensive individual play therapy and intensive sibling group play therapy as facilitated by professionally trained therapists. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
36.
Effects of austenitizing treatment temperatures on aqueous corrosion properties of martensitic stainless steels were investigated by electrochemical tests (potentiodynamic test, potentiostatic test and electrochemical impedance spectroscopy), and surface analyses (optical microscopy and XRD). The results of potentiodynamic test revealed that the breakdown potential increased with the increased austenitizing temperature, indicating increased relative resistance to initiation of localized corrosion. EIS measurements showed that MSS3 (1030 °C) exhibits larger polarization resistance value than MSS1 (970 °C) and MSS2 (1000 °C) at passive and breakdown states. This was caused by decreasing the amount of Cr-rich M23C6 carbide which acts as preferential sites for pitting corrosion.  相似文献   
37.
换填法建筑地基处理的工程实录   总被引:2,自引:0,他引:2  
结合某工程的地基处理,对换填法的应用作了较详细的阐述。  相似文献   
38.
Corrosion rates were measured at the exposed spots of rebars near three corners of Muddy Creek Bridge located in northern West Virginia using a 3LP device. Also, chloride contents of the concrete samples taken from the vicinity of the spots were analyzed using a wet chemical method that had been developed in this study. The average corrosion rate over the three spots was 4.66 mA/m2, which is in the range of corrosion damage possible in 10–15 years. The average chloride content of the concrete over the three spots was 703 parts per million (ppm), which is well above the threshold limit value of 260 ppm. Although the corrosion rate measurement method using a 3LP device is by manual operation, it is found to be reliable and effective, and, thus, recommended for future studies of this kind of research. The wet chemical method developed in this study is found to be effective.  相似文献   
39.
This study examined partner violence in the year before and the year after individually based, outpatient alcoholism treatment for 301 married or cohabiting male alcoholic patients and used a demographically matched nonalcoholic comparison sample. In the year before treatment, 56% of the alcoholic patients had been violent toward their female partner, 4 times the rate of 14% in the comparison sample. In the year after treatment, violence decreased significantly to 25% of the alcoholic sample but remained higher than in the comparison group. Among remitted alcoholics after treatment, violence prevalence of 15% was nearly identical to the comparison sample and half the rate among relapsed patients (32%). Thus, partner violence decreased after alcoholism treatment, and clinically significant violence reductions occurred for patients whose alcoholism was remitted after treatment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
40.
黄玲 《冶金动力》2003,(6):49-51
通过高炉鼓风机扩压叶片断裂事故,从化学分析、物理检验,结合使用情况对扩压叶片断裂原因进行了详细分析,并提出了改进措施。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司    京ICP备09084417号-23

京公网安备 11010802026262号