全文获取类型
收费全文 | 25069篇 |
免费 | 2045篇 |
国内免费 | 857篇 |
专业分类
电工技术 | 1321篇 |
技术理论 | 1篇 |
综合类 | 1379篇 |
化学工业 | 4503篇 |
金属工艺 | 1317篇 |
机械仪表 | 1318篇 |
建筑科学 | 1861篇 |
矿业工程 | 578篇 |
能源动力 | 884篇 |
轻工业 | 1635篇 |
水利工程 | 339篇 |
石油天然气 | 1342篇 |
武器工业 | 118篇 |
无线电 | 3108篇 |
一般工业技术 | 3239篇 |
冶金工业 | 1438篇 |
原子能技术 | 314篇 |
自动化技术 | 3276篇 |
出版年
2024年 | 84篇 |
2023年 | 407篇 |
2022年 | 699篇 |
2021年 | 1022篇 |
2020年 | 719篇 |
2019年 | 674篇 |
2018年 | 694篇 |
2017年 | 808篇 |
2016年 | 758篇 |
2015年 | 923篇 |
2014年 | 1239篇 |
2013年 | 1583篇 |
2012年 | 1574篇 |
2011年 | 1723篇 |
2010年 | 1397篇 |
2009年 | 1442篇 |
2008年 | 1341篇 |
2007年 | 1238篇 |
2006年 | 1349篇 |
2005年 | 1163篇 |
2004年 | 841篇 |
2003年 | 759篇 |
2002年 | 760篇 |
2001年 | 541篇 |
2000年 | 521篇 |
1999年 | 601篇 |
1998年 | 572篇 |
1997年 | 462篇 |
1996年 | 446篇 |
1995年 | 345篇 |
1994年 | 280篇 |
1993年 | 190篇 |
1992年 | 174篇 |
1991年 | 117篇 |
1990年 | 92篇 |
1989年 | 72篇 |
1988年 | 88篇 |
1987年 | 48篇 |
1986年 | 44篇 |
1985年 | 25篇 |
1984年 | 33篇 |
1983年 | 19篇 |
1982年 | 27篇 |
1981年 | 12篇 |
1980年 | 10篇 |
1979年 | 15篇 |
1977年 | 4篇 |
1976年 | 9篇 |
1975年 | 4篇 |
1965年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
洼60-H26水平井套铣打捞技术 总被引:3,自引:1,他引:2
洼60-H26井是一口中曲率水平井,设计井深1 922 m,由于地面条件的限制,设计采用三维井眼轨道。该井水平段在钻至井深1 801 m时,发生卡钻事故。在卡钻事故处理过程中,采用测卡、爆炸松扣技术取出上部钻具后,应用了不同规格的套铣管对被卡钻具进行套铣,采用间歇式套铣方式实现了大斜度井段(45°-90°)的安全套铣,采用短套铣管完成了时水平井段内φ215.0 mm稳定器的套铣,采用φ228.6 mm套铣管成功套铣水平井段被卡LWD仪器,最后通过震击器震击成功解卡。详细介绍了洼60-H26水平井卡钻事故的处理过程,分析了在水平段处理卡钻事故的难点。该井处理卡钻事故的经验,对以后水平井施工中处理井下事故、打捞贵重仪器具有借鉴价值。 相似文献
42.
本工艺是对原有工艺的改进,突破了原有布帮鞋不能采用无浆贴合的局限性,对原有工艺中的不足有了很大的改进,提高了生产效率,改善了鞋子外观质量,增加了鞋子的美观性。 相似文献
43.
This paper proposes a method to reduce the vibration of the three-phase HB-type stepping motor with cogging torque by the feedforward compensation control. The compensation signal to suppress the vibration of the motor frame is obtained by the repetitive controller installing an online Fourier transformer and utilizing an acceleration sensor attached to the motor frame or an acoustic sensor such as a microphone placed close to the frame. The sensor is used only for the acquisition of the feedforward compensation data. The feedforward compensation signal at an arbitrary operating point is derived from the amplitude and phase data of the frequency components and the operating point data. Compensation data obtained by the repetitive controller is applied to the operating point changed by reference frequency and load condition in steady state. The compensation signal for the new operating point will be generated from compensation data utilizing polynomial equation approximation and linear interpolation method. The effectiveness of this proposed method is confirmed by the experimental results. 相似文献
44.
射频板条CO_2激光器并联谐振技术的研究 总被引:1,自引:0,他引:1
本文利用周期性网络模型计算了射频板条CO2激光器电极的纵向电压分布.探讨了并联谐振技术在板条器件中获得成功运用的原因.提出了利用并联谐振技术进一步提高电压分布均匀性的两个途径. 相似文献
45.
HDPE/PS/HDPE-g-PS合金的相容性和力学性能研究 总被引:1,自引:0,他引:1
用自制接枝共聚物GR-Ⅰ、GR-Ⅱ相容剂研究其对HDPE/PS共混物相容性和力学性能的影响。通过SEM、DMA、DSC和力学性能测试表征,表明在HDPE/PS共混中加入这些相容剂其相容性和力学性能有一定提高 相似文献
46.
小剂量辐射对肿瘤细胞K_(562)及肿瘤病人天然杀伤细胞(NK)活性的影响 总被引:2,自引:0,他引:2
已知小剂量辐射可增强机体免疫功能。从对高本底地区的调查发现,该地区居民肿瘤死亡率及某些肿瘤发病率有所降低(1)。NK细胞能直接杀伤肿瘤细胞,在肿瘤免疫中起着重要的作用。本文观察小剂量辐射对肿瘤病人和正常人外周血淋巴细胞NK活性的相对效应以及对人红白血病细胞(K(562)细胞)的影响,以期从体外买验来探索较小剂量辐射对肿瘤治疗的影响 相似文献
47.
48.
49.
Following up on recent studies of the Zn-rich corners of the Zn-Fe-Ni and Zn-Fe-Si ternary systems, a 450 °C isothermal section
of the Zn-Fe-Ni-Si quaternary phase diagram with the Zn composition being fixed at 93 at.% was determined experimentally using
optical microscopy, scanning electron microscopy (SEM) coupled with energy dispersive x-ray spectroscopy (EDS), and x-ray
diffractometry (XRD). FeSi was found to be in equilibrium with almost all phases in the section, including the T, ζ, Ni-δ,
NiSi2, and FeSi2 phases, as well as the liquid phase (L). Silicon solubilities in the T, ζ, and Ni-δ phases were rather limited. However,
the solubilities of Fe and Zn in the NiSi2 phase, at 4.5 at.% and 7.2 at.%, respectively, were appreciable. The existence of the (L+NiSi2+Ni-δ) three-phase equilibrium state apparently prevents other Ni-Si compounds from entering equilibrium with the liquid at
450 °C. No true quaternary compound was found in the study. 相似文献
50.
ABSTRACT: :
Soybeans ( Glycine max ) were soaked and ground to obtain soymilk. The soymilk was cooked in an open tank and held at 85 to 90 deg;C. Yuba films were picked up in 20 min intervals and dried for 20 min. Yuba films were soaked in chicken-flavor solutions (25% and 35%), and baking soda (BS) solutions (0%, 1%, 2%, and 3% BS), and cooked at 100 °C for 30 min, 60 min, and 90 min. TIA decreased (p < 0.05) with the increase of heating time and BS concentration. In vitro protein digestibility (IVPD) decreased with heating time and BS concentration (p < 0.05). Sensory characteristics were affected by flavor concentration. By using 0% BS, 25% of the chicken flavor concentration, and a short heating time method, meat-like products with low TIA, high IVPD, and good sensory characteristics were obtained. 相似文献
Soybeans ( Glycine max ) were soaked and ground to obtain soymilk. The soymilk was cooked in an open tank and held at 85 to 90 deg;C. Yuba films were picked up in 20 min intervals and dried for 20 min. Yuba films were soaked in chicken-flavor solutions (25% and 35%), and baking soda (BS) solutions (0%, 1%, 2%, and 3% BS), and cooked at 100 °C for 30 min, 60 min, and 90 min. TIA decreased (p < 0.05) with the increase of heating time and BS concentration. In vitro protein digestibility (IVPD) decreased with heating time and BS concentration (p < 0.05). Sensory characteristics were affected by flavor concentration. By using 0% BS, 25% of the chicken flavor concentration, and a short heating time method, meat-like products with low TIA, high IVPD, and good sensory characteristics were obtained. 相似文献