全文获取类型
收费全文 | 15077篇 |
免费 | 1744篇 |
国内免费 | 1199篇 |
专业分类
电工技术 | 353篇 |
综合类 | 1584篇 |
化学工业 | 1331篇 |
金属工艺 | 723篇 |
机械仪表 | 1010篇 |
建筑科学 | 3025篇 |
矿业工程 | 724篇 |
能源动力 | 266篇 |
轻工业 | 867篇 |
水利工程 | 626篇 |
石油天然气 | 1592篇 |
武器工业 | 431篇 |
无线电 | 819篇 |
一般工业技术 | 3115篇 |
冶金工业 | 433篇 |
原子能技术 | 792篇 |
自动化技术 | 329篇 |
出版年
2024年 | 98篇 |
2023年 | 244篇 |
2022年 | 580篇 |
2021年 | 612篇 |
2020年 | 557篇 |
2019年 | 465篇 |
2018年 | 512篇 |
2017年 | 589篇 |
2016年 | 635篇 |
2015年 | 611篇 |
2014年 | 833篇 |
2013年 | 924篇 |
2012年 | 892篇 |
2011年 | 1181篇 |
2010年 | 827篇 |
2009年 | 842篇 |
2008年 | 815篇 |
2007年 | 895篇 |
2006年 | 883篇 |
2005年 | 762篇 |
2004年 | 623篇 |
2003年 | 517篇 |
2002年 | 517篇 |
2001年 | 448篇 |
2000年 | 350篇 |
1999年 | 327篇 |
1998年 | 241篇 |
1997年 | 195篇 |
1996年 | 192篇 |
1995年 | 138篇 |
1994年 | 100篇 |
1993年 | 103篇 |
1992年 | 87篇 |
1991年 | 99篇 |
1990年 | 76篇 |
1989年 | 50篇 |
1988年 | 39篇 |
1987年 | 28篇 |
1986年 | 27篇 |
1985年 | 17篇 |
1984年 | 18篇 |
1983年 | 9篇 |
1982年 | 14篇 |
1980年 | 14篇 |
1979年 | 10篇 |
1966年 | 3篇 |
1965年 | 3篇 |
1964年 | 3篇 |
1959年 | 2篇 |
1957年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
用屏蔽暂堵技术封堵水平井裂缝性漏层 总被引:1,自引:1,他引:0
克拉玛依油田HW702水平井的大斜度段和水平段,将穿越纵向裂缝发育的二叠系佳木河组储层。为安全钻进和保护油层,用超细碳酸钙和磺化沥青复配后加入复合离子钻井液中成屏蔽暂堵的堵漏钻井液。室内用岩心试验,屏蔽暂堵后渗透率可降为0,暂堵深度小于3cm,可用酸化和射孔解堵。现场使用效果也很好,使HW702水平井顺利完钻,并获得工业油气流。 相似文献
32.
System reliability is evolving as an important design method for selecting components and topology. It should be used to investigate the original intact structure behavior as well as providing sufficient reserve capacity under likely accident and damage scenarios. Highway bridges are an area of special concern since effort to optimize the cost of construction may not provide adequate redundant capacity. The paper describes an example in which a typical girder bridge structure is optimized (both size and girder spacing) to achieve target system performance. System reliability constraints are imposed on the behavior of the intact structure under highway loads. Also, residual system reliability constraints are imposed to control safety under specified accident scenarios corresponding to damage and “lost” members due to corrosion, fatigue, fire or accidental collisions. An optimal design framework for controlling safety under all these life cycle situations is thus provided. 相似文献
33.
The application of irradiation in silicon crystal is introduced.The defects caused by irradiation are reviewed and some major ways of studying defects in irradiated silicon are summarized.Furthermore the problems in the investigation of irradiated silicon are discussed as well as its properties. 相似文献
34.
35.
The irradiation with high-energy (7.35 MeV) protons through a set of energy degraders was used to suppress leakage of the silicon power diodes subjected to local lifetime control. The aim was to modify the profile of recombination centers and to reduce production of vacancy complexes. The high-energy proton irradiation was compared with standard local lifetime killing by high-energy alphas. Recombination centers arising from irradiation were characterized after irradiation and subsequent annealing at 220 and 350 °C by deep level transient spectroscopy and I-V profiling. Static and dynamic parameters of irradiated diodes were also measured and compared. Results show that the applied irradiation with protons provides 3-10 times lower leakage compared to standard alphas for equivalent reduction of the reverse recovery current maximum. On the other hand, the excessive formation of hydrogen donors at high proton fluences and their diffusion during annealing at 350° decreases diode blocking capability. 相似文献
36.
葡北3-12注气井位于吐哈盆地葡北构造带中断葡北1号构造.井深为3610m。针对该区块地层承压能力低,易漏失,油气水窜严重,常规固井方法无法满足固井要求的问题,该井采用三段三凝制、常规水泥浆和泡沫水泥浆体系固井,并采用重钻井液顶替技术.降低施工压力。该技术能保证固井候凝过程中井底压力平衡,施工安全。现场应用表明,采用常规水泥浆和泡沫水泥浆固井技术.提高了低压易漏井、长封固井段的固井质量,解决了水泥返高不足的问题;并通过一次常规固井工艺实现了全井封固,简化了施工工艺,节约了成本,经济效益和社会效益十分显著。该井封固优质段累计达2600m,优质率达85%,固井结果良好。 相似文献
37.
38.
钢纤维聚合物混凝土抗压本构关系 总被引:2,自引:0,他引:2
钢纤维聚合物混凝土是由聚合物混凝土基体和钢纤维共同组成的纤维增强复合材料,它的力学行为不仅依赖于聚合物混凝土基体的行为,而且与钢纤维的掺量、分散特征以及钢纤维的几何尺寸有关,本文将基于损伤力学原理研究在不同纤维掺量下的钢纤维聚合物混凝土的全程压力-应变曲线及其本构模型。 相似文献
39.
An optical nondestructive strain measurement technique was performed to analyze the mechanical deformation induced by an electrical field within the insulating materials. Poly(ethylene naphthalene 2,6‐dicarboxylate) (PEN) films were then subjected to constant electrical fields right up to their electrical breakdown. The experimental technique made it possible to follow the various stages of the mechanical behavior of PEN in real time. The final breakdown occurred in the observation zone and the related mechanical deformation was captured. A “margarita” structure was observed with a hole at the center. The experimental results indicated that the level of the induced‐mechanical deformations depended on the local environment. We defined two different zones representing the inside and the outside of the damaged area. The induced‐deformations were larger in the damaged zone. It was also observed that deformations increased when the sample had a lower degree of crystallinity. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
40.
Tooru Tanaka Toshiyuki Yamaguchi Akihiro Wakahara Akira Yoshida Ryoichi Taniguchi Yatsuka Matsuda Masatoshi Fujishiro 《Solar Energy Materials & Solar Cells》2003,75(1-2):115-120
Radiation damages due to 8 MeV electron irradiation in electrical properties of CuInSe2 thin films have been investigated. The n-type CuInSe2 films in which the carrier concentration was about 3×1016 cm−3, were epitaxially grown on a GaAs(0 0 1) substrate by RF diode sputtering. No significant change in the electrical properties was observed under the electron fluence <3×1016 e cm−2. As the electron fluence exceeded 1017 e cm−2, both the carrier concentration and Hall mobility slightly decreased. The carrier removal rate was estimated to be about 0.8 cm−1, which is slightly lower than that of III–V compound materials. 相似文献