全文获取类型
收费全文 | 48021篇 |
免费 | 2704篇 |
国内免费 | 1303篇 |
专业分类
电工技术 | 1505篇 |
技术理论 | 4篇 |
综合类 | 2897篇 |
化学工业 | 11479篇 |
金属工艺 | 6542篇 |
机械仪表 | 1287篇 |
建筑科学 | 6601篇 |
矿业工程 | 2224篇 |
能源动力 | 1041篇 |
轻工业 | 4255篇 |
水利工程 | 1875篇 |
石油天然气 | 1793篇 |
武器工业 | 155篇 |
无线电 | 891篇 |
一般工业技术 | 3487篇 |
冶金工业 | 4901篇 |
原子能技术 | 266篇 |
自动化技术 | 825篇 |
出版年
2024年 | 168篇 |
2023年 | 453篇 |
2022年 | 1113篇 |
2021年 | 1335篇 |
2020年 | 1258篇 |
2019年 | 881篇 |
2018年 | 893篇 |
2017年 | 1137篇 |
2016年 | 1188篇 |
2015年 | 1325篇 |
2014年 | 2540篇 |
2013年 | 2412篇 |
2012年 | 3231篇 |
2011年 | 3480篇 |
2010年 | 2947篇 |
2009年 | 3071篇 |
2008年 | 2319篇 |
2007年 | 3229篇 |
2006年 | 3181篇 |
2005年 | 2693篇 |
2004年 | 2312篇 |
2003年 | 2147篇 |
2002年 | 1762篇 |
2001年 | 1394篇 |
2000年 | 1103篇 |
1999年 | 883篇 |
1998年 | 702篇 |
1997年 | 554篇 |
1996年 | 428篇 |
1995年 | 407篇 |
1994年 | 283篇 |
1993年 | 209篇 |
1992年 | 202篇 |
1991年 | 154篇 |
1990年 | 92篇 |
1989年 | 120篇 |
1988年 | 69篇 |
1987年 | 66篇 |
1986年 | 47篇 |
1985年 | 45篇 |
1984年 | 43篇 |
1983年 | 35篇 |
1982年 | 18篇 |
1981年 | 5篇 |
1980年 | 5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
21.
胜科1井钻井事故的预防与处理 总被引:2,自引:1,他引:1
胜科1井设计井深7 000 m,完钻井深7 026 m。在该井钻井过程中,针对上部大尺寸钻头破岩效率低、大井眼井壁稳定性差、大段盐膏层、膏岩层的塑性蠕变和塑性流动造成井眼复杂、超深井高温高压给钻井液性能的控制和水泥浆调控等带来的一系列技术难题,制定了一整套预防井下事故和复杂情况的技术措施,从而确保了该井的钻探成功。该井在钻井过程发生了2次断钻具事故和1次卡钻事故,根据超深井的特点,采取了较为稳妥的处理措施,同时,有针对性地研制了高效铣环和PDC钻头专用打捞器,3次事故处理均获得了成功,共耗时38.5 d。详细介绍了该井所采取的预防和处理钻井事故的技术措施,可为其他超深井的钻井施工提供一定的借鉴。 相似文献
22.
《Materials and Manufacturing Processes》2007,22(1):5-8
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
23.
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
24.
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
25.
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
26.
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
27.
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
28.
29.
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
30.
O'Farrell Timothy J.; Fals-Stewart William; Murphy Marie; Murphy Christopher M. 《Canadian Metallurgical Quarterly》2003,71(1):92
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