全文获取类型
收费全文 | 10697篇 |
免费 | 1082篇 |
国内免费 | 538篇 |
专业分类
电工技术 | 643篇 |
技术理论 | 1篇 |
综合类 | 792篇 |
化学工业 | 1741篇 |
金属工艺 | 792篇 |
机械仪表 | 715篇 |
建筑科学 | 748篇 |
矿业工程 | 343篇 |
能源动力 | 259篇 |
轻工业 | 771篇 |
水利工程 | 214篇 |
石油天然气 | 681篇 |
武器工业 | 99篇 |
无线电 | 1182篇 |
一般工业技术 | 1295篇 |
冶金工业 | 519篇 |
原子能技术 | 124篇 |
自动化技术 | 1398篇 |
出版年
2024年 | 57篇 |
2023年 | 246篇 |
2022年 | 381篇 |
2021年 | 534篇 |
2020年 | 393篇 |
2019年 | 319篇 |
2018年 | 381篇 |
2017年 | 464篇 |
2016年 | 322篇 |
2015年 | 461篇 |
2014年 | 604篇 |
2013年 | 657篇 |
2012年 | 754篇 |
2011年 | 718篇 |
2010年 | 725篇 |
2009年 | 644篇 |
2008年 | 591篇 |
2007年 | 598篇 |
2006年 | 606篇 |
2005年 | 473篇 |
2004年 | 331篇 |
2003年 | 276篇 |
2002年 | 281篇 |
2001年 | 230篇 |
2000年 | 213篇 |
1999年 | 200篇 |
1998年 | 170篇 |
1997年 | 132篇 |
1996年 | 104篇 |
1995年 | 91篇 |
1994年 | 87篇 |
1993年 | 59篇 |
1992年 | 60篇 |
1991年 | 40篇 |
1990年 | 23篇 |
1989年 | 17篇 |
1988年 | 19篇 |
1987年 | 9篇 |
1986年 | 18篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 11篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
The paramagnetic Meissner effect (PME) was observed on the field-cooled M-T curvesof melt-textured Y0.99Nd0.01Ba2Cu3O7-y in applied magnetic fields from 1kOe toJ0kOe. In the magnetic field below 1kOe, the sample undergoes the typical transi-tion from the normal state to the superconducting state when it was cooled down. Theapplied magnetic fields in which the PME occurs, are very high compared with thefields reported in literatures. We propose that the occurrence of the PME may be dueto a phase transition of flux vortices in the superconductors. 相似文献
42.
研究了在250℃、不同挤压比下挤压变形对Mg95 Zn4.3 Y0.7合金组织及性能的影响。结果表明,Mg95 Zn4.3 Y0.7经过挤压变形后,合金中晶界处的共晶相破碎,弥散分布至晶粒内部,并且晶粒显著细化。同时,随着挤压比的增大,晶粒细化程度增加,合金的力学性能单调增加。当挤压比为16时,合金晶粒尺寸为5-8μm,抗拉强度为288.9MPa,显微硬度HV值为117.8。 相似文献
43.
Prof. Ren-Xiao Wang Mi Zhou Hui-Lai Ma Prof. Yuan-Biao Qiao Prof. Qing-Shan Li 《ChemMedChem》2021,16(10):1576-1592
Chronic inflammation represents a long-term reaction of the body's immune system to noxious stimuli. Such a sustained inflammatory response sometimes results in lasting damage to healthy tissues and organs. In fact, chronic inflammation is implicated in the development and progression of various diseases, including cardiovascular diseases, respiratory diseases, metabolic diseases, neurodegenerative diseases, and even cancers. Targeting nonresolving inflammation thus provides new opportunities for treating relevant diseases. In this review, we will go over several chronic inflammation-associated diseases first with emphasis on the role of inflammation in their pathogenesis. Then, we will summarize a number of natural products that exhibit therapeutic effects against those diseases by acting on different markers in the inflammatory response. We envision that natural products will remain a rich resource for the discovery of new drugs treating diseases associated with chronic inflammation. 相似文献
44.
Shishan Xue Guanfei Liu Jingjuan Lai Peng An Yang Liu Yuanpeng Wu Yu Wang Zhiyong Ye Qiao Tang Hongwei Zhou 《大分子材料与工程》2021,306(11):2100415
Self-healing hydrogels often possess poor mechanical properties which largely limits their applications in many fields. In this work, boron nitride nanosheets are introduced into a network of the poly(vinyl alcohol)/borax (PVA/borax) hydrogels to enhance the mechanical properties of the hydrogel without compromising the self-healing abilities. The obtained hydrogels exhibit excellent mechanical properties with a tensile strength of 0.410 ± 0.007 MPa, an elongation at break of 1712%, a Young's Modulus of 0.860 ± 0.023 MPa, and a toughness of 3.860 ± 0.075 MJ m−3. In addition, the self-healing efficiency of the hydrogels is higher than 90% within 10 min at room temperature. Benefiting from the excellent self-healing properties, the shapeability of the hydrogel fragments is observed using different molds. In addition, the hydrogels display rapid pH-driven shape memory effects and can recover to their original shape within 260 s. Overall, this work provides a new approach to hydrogels with integrated excellent mechanical properties, self-healing abilities, and rapid pH-driven shape memory effects. 相似文献
45.
为了满足制造升级的需要,传统的电气控制技术通过与现代信息技术、现代控制技术、现代驱动控制技术、组态技术的结合产生了新的技术——现代电气,它提升了制造设备的自动化程度,是实现装备制造产业升级的关键技术.现代电气设备包含了电气控制系统、可编程控制器、电机及控制器、变频器、HMI等.我们通过电气系统与多项工业控制技术的结合,改造旧的生产设备,提升生产效率,降低劳动密集程度. 相似文献
46.
Stress corrosion cracking (SCC) of α-brass in ammonia solution was studied under mode III loading. The results showed that SCC occurred on the principal stress planes where shear stresses are zero. No SCC occurred on the maximum shear stress plane. Ammonia concentration affected fracture behaviour. When the concentration was low, many cracks with spacing of 10–150 μm were found on 45 ° planes, i.e., the principal stress planes. When the concentration was high, the cracks on 45 ° planes were not clearly visible because of serious general corrosion. 相似文献
47.
采用熔模精密铸造工艺,生产中空螺旋状不锈钢冷却水喷头,其工艺要点是,采用热型重力浇注,在高温下进行自由浇注。同时采用先慢后快,流量由小到大的浇注方法。结果表明:铸件表面光洁,无砂眼、气孔等缺陷,铸件合格率高于90%;在实际使用中,雾化区域直径大于1.5m,雾化率大于90%,喷雾效果稳定良好;盐雾试验2000h没有锈蚀,具有优良的耐磨性和耐腐蚀性。 相似文献
48.
Y. H. Cheng X. L. Qiao J. G. Chen Y. P. Wu C. S. Xie Y. Q. Wang D. S. Xu S. B. Mo Y. B. Sun 《Surface & coatings technology》2002,160(2-3)
Carbon nitride films were deposited by direct current plasma assisted pulsed laser ablation of a graphite target under a nitrogen atmosphere at room temperature. The surface morphology, composition and bonding structure of the deposited films were characterized by atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectroscopy, Raman, and X-ray photoelectron spectroscopy (XPS). The effect of laser fluences in the range 0.5–3 J/cm2 on the surface morphology, composition and bonding structure of the carbon nitride films were systematically studied. As laser fluence is increased, AFM results show a great decrease in the surface roughness of carbon nitride films. FTIR and XPS results indicate an increase in the N/C ratio and the content of N atoms bonded to sp3 C, as well as a decrease in the content of H atoms and the content of N atoms boned to sp2 C in the deposited films, and Raman spectra indicate an increase in the content of disordered sp2 C atoms and the sp2 cluster size. The increase in the film density and the decrease in the particle fraction contribute to the decrease of surface roughness with increasing laser fluence. 相似文献
49.
非稳态轧制时轧机振动稳定性的数值分析 总被引:2,自引:0,他引:2
利用轧制理论方程和机械振动理论的能量判据 ,给出了一个较精确的分析轧机传动系统扭转振动稳定性的数值计算方法 相似文献
50.
复合助剂对低温常压烧结AIN性能的影响 总被引:1,自引:0,他引:1
研究了Y2O3,LiO2,CaO烧结助剂对AlN陶瓷常压烧结致密度和性能的影响。结果发现,同时添加Y2O3,LiO2,CaO作为助剂,在1600℃低温烧结就能获得具有高致密度、较小的晶粒尺寸(1μm~4μm)、较高的抗弯强度(331MPa)、断裂韧性(3.8MPa·m1/2)及导热率(118W·m-1·K-1)的AlN陶瓷。 相似文献