全文获取类型
收费全文 | 494435篇 |
免费 | 38090篇 |
国内免费 | 20295篇 |
专业分类
电工技术 | 28152篇 |
技术理论 | 63篇 |
综合类 | 34169篇 |
化学工业 | 80564篇 |
金属工艺 | 27772篇 |
机械仪表 | 31442篇 |
建筑科学 | 39778篇 |
矿业工程 | 15618篇 |
能源动力 | 13655篇 |
轻工业 | 31972篇 |
水利工程 | 9106篇 |
石油天然气 | 31126篇 |
武器工业 | 3839篇 |
无线电 | 55750篇 |
一般工业技术 | 55516篇 |
冶金工业 | 25465篇 |
原子能技术 | 5168篇 |
自动化技术 | 63665篇 |
出版年
2024年 | 739篇 |
2023年 | 6804篇 |
2022年 | 10670篇 |
2021年 | 17258篇 |
2020年 | 13514篇 |
2019年 | 11048篇 |
2018年 | 12982篇 |
2017年 | 14760篇 |
2016年 | 13402篇 |
2015年 | 18430篇 |
2014年 | 23554篇 |
2013年 | 28640篇 |
2012年 | 31099篇 |
2011年 | 34382篇 |
2010年 | 30454篇 |
2009年 | 29063篇 |
2008年 | 28755篇 |
2007年 | 27560篇 |
2006年 | 28391篇 |
2005年 | 24973篇 |
2004年 | 16976篇 |
2003年 | 15063篇 |
2002年 | 13923篇 |
2001年 | 12573篇 |
2000年 | 12546篇 |
1999年 | 13766篇 |
1998年 | 11144篇 |
1997年 | 9496篇 |
1996年 | 8819篇 |
1995年 | 7327篇 |
1994年 | 6087篇 |
1993年 | 4275篇 |
1992年 | 3362篇 |
1991年 | 2578篇 |
1990年 | 2030篇 |
1989年 | 1647篇 |
1988年 | 1347篇 |
1987年 | 850篇 |
1986年 | 639篇 |
1985年 | 444篇 |
1984年 | 296篇 |
1983年 | 231篇 |
1982年 | 237篇 |
1981年 | 144篇 |
1980年 | 147篇 |
1979年 | 79篇 |
1978年 | 42篇 |
1977年 | 48篇 |
1976年 | 67篇 |
1973年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
81.
根据煤矿井下综采工作面不同条件下起吊装运液压支架的需求,运用液压支架起吊装置,解决了在井下综采工作面巷道空间狭窄,顶板的平整度差等不利条件下,原有液压支架起吊装置安装困难,起吊平稳性和安全性差的技术性难题.通过对分体式液压支架起吊装置机构的组成及工作原理进行阐述,并对本装置的起吊状态进行了受力分析,验证了起吊液压支架的起吊能力,为进一步设计及油泵选型提供了参考. 相似文献
82.
83.
Grain refinement is critical for fabricating high-quality Al-Si casting components in the application of automobile and aerospace industries,while the well-known Si-poisoning effect makes it difficult.Nbbased refiners offer an effective method to refine Al-Si casting alloys,but their anti Si-poisoning capability is far from being understood.In this work,the grain refining mechanism and the anti Si-poisoning effect in the Al-10 Si/Al-5 Nb-B system were systematically investigated by combining transmission electron microscope,first-principles calculations,and thermodynamic calculations.It is revealed that NbB2provides the main nucleation site in the Al-10 Si ingot inoculated by 0.1 wt.%Nb Al-5 Nb-B refiner.The exposed Nb atoms on the(0001)NbB2and(1-100)NbB2surface can be substituted by Al to form(Al,Nb)B2intermedia layers.In addition,a layer of NbAl3-like compound(NbAl3')can cover the surface of NbB2with the orientation relation of(1-100)[11-20]NbB2//(110)[110]NbAl3'.Both of the(Al,Nb)B2and NbAl3'intermedia layers contribute to enhancing the nucleation potency of NbB2particles.These discoveries provide fundamental insight to the grain refining mechanism of the Nb-B based refiners for Al-Si casting alloys and are expected to guide the future development of stronger refiners for Al-Si casting alloys. 相似文献
84.
Electric nanogenerators that directly convert the energy of moving drops into electrical signals require hydrophobic substrates with a high density of static electric charge that is stable in “harsh environments” created by continued exposure to potentially saline water. The recently proposed charge-trapping electric generators (CTEGs) that rely on stacked inorganic oxide–fluoropolymer (FP) composite electrets charged by homogeneous electrowetting-assisted charge injection (h-EWCI) seem to solve both problems, yet the reasons for this success have remained elusive. Here, systematic measurements at variable oxide and FP thickness, charging voltage, and charging time and thermal annealing up to 230 °C are reported, leading to a consistent model of the charging process. It is found to be controlled by an energy barrier at the water-FP interface, followed by trapping at the FP-oxide interface. Protection by the FP layer prevents charge densities up to −1.7 mC m−2 from degrading and the dielectric strength of SiO2 enables charge decay times up to 48 h at 230 °C, suggesting lifetimes against thermally activated discharging of thousands of years at room temperature. Combining high dielectric strength oxides and weaker FP top coatings with electrically controlled charging provides a new paradigm for developing ultrastable electrets for applications in energy harvesting and beyond. 相似文献
85.
Ping Xiao Jue Wang Lei Fang Zitong Zhao Xiangshi Sun Xiaochen Liu Haiqiang Cao Pengcheng Zhang Dangge Wang Yaping Li 《Advanced functional materials》2021,31(36):2104068
Neoantigen vaccines and adoptive dendritic cell (DC) transfer are major clinical approaches to initiate personalized immunity in cancer patients. However, the immunization efficacy is largely limited by the in vivo trajectory including neoantigens’ access to resident DCs and DCs’ access to lymph nodes (LNs). Herein, an innovative strategy is proposed to improve personalized immunization through neoantigen-loaded nanovaccines synergized with adoptive DC transfer. It is found that it enables selective delivery of neoantigens to resident DCs and macrophages by coating cancer cell membranes onto neoantigen-loaded nanoparticles. In addition, the nanovaccines promote the secretion of chemokine C-C motif ligand 2 (CCL2), CCL3, and C-X-C motif ligand 10 from macrophages, thus potentiating the access of transferred DCs to LNs. This immunization strategy enables coordinated delivery of identified neoantigens and autologous tumor lysate-derived undefined antigens, leading to initiation of antitumor T cell immunity in a personalized manner. It significantly inhibits tumor growth in prophylactic and established mouse tumor models. The findings provide a new vision for potentiating adoptive cell transfer by nanovaccines, which may open the door to a transformative possibility for improving personalized immunization. 相似文献
86.
87.
Wireless Personal Communications - Web citation analysis is primarily used to examine the impact of an author, an article or a publication by counting the amount of intervals that has been cited by... 相似文献
88.
多普勒测风激光雷达通过分析系统回波信号的多普勒频移反演出风速,为提高风场探测精度,从稳频技术方面展开研究。在稳频过程中,分别采取措施消除激光频率的长期漂移和短期抖动。针对激光频率的长期漂移,设计并研制了种子激光器温控箱,通过水浴的控温方式大大减小了激光频率的长期漂移,将激光频率稳定在±50 MHz以内;针对激光频率的短期抖动,采用以碘分子吸收池为核心器件的稳频系统,通过半导体控温方式对碘分子吸收池精确控温,控温精度达0.03 ℃,提高了稳频精度,将激光频率进一步稳定在±8 MHz以内,满足±10 MHz以内的设计精度要求。通过搭建多普勒测风激光雷达系统,对发射激光稳频装置进行系统验证,连续4组风场观测结果表明:系统探测高度为17 km,绝大部分方差在4 m/s以下,满足测风激光雷达测量指标的要求。 相似文献
89.
针对泥浆脉冲系统发生的孔内压杆的情况,分析压杆原因,提出一种区别于无法完成压杆打捞的传统打捞方法的打捞工艺,并详细分析其打捞工具、打捞过程、打捞注注意事项,在此基础上给出孔内压杆的防范措施. 相似文献
90.
长平煤矿机掘三队针对53031巷掘进期间工作面安装的SSJ-800型带式输送机经常出现跑偏打滑现象,导致输送机运行负荷大、煤矸运输效率低等,通过技术研究,对输送机安装了一套电液防打滑张紧装置.通过实际应用效果来看,该装置具有动作保护灵敏、故障率低、防打滑效果好等优点,输送机采用该装置后打滑事故率降低了7%,取得了显著应用效果. 相似文献