全文获取类型
收费全文 | 14308篇 |
免费 | 1023篇 |
国内免费 | 472篇 |
专业分类
电工技术 | 162篇 |
综合类 | 1001篇 |
化学工业 | 1226篇 |
金属工艺 | 4149篇 |
机械仪表 | 4043篇 |
建筑科学 | 297篇 |
矿业工程 | 500篇 |
能源动力 | 179篇 |
轻工业 | 277篇 |
水利工程 | 140篇 |
石油天然气 | 459篇 |
武器工业 | 164篇 |
无线电 | 259篇 |
一般工业技术 | 1805篇 |
冶金工业 | 776篇 |
原子能技术 | 31篇 |
自动化技术 | 335篇 |
出版年
2024年 | 106篇 |
2023年 | 321篇 |
2022年 | 413篇 |
2021年 | 467篇 |
2020年 | 498篇 |
2019年 | 433篇 |
2018年 | 479篇 |
2017年 | 622篇 |
2016年 | 568篇 |
2015年 | 505篇 |
2014年 | 597篇 |
2013年 | 625篇 |
2012年 | 742篇 |
2011年 | 807篇 |
2010年 | 641篇 |
2009年 | 725篇 |
2008年 | 616篇 |
2007年 | 908篇 |
2006年 | 946篇 |
2005年 | 692篇 |
2004年 | 666篇 |
2003年 | 521篇 |
2002年 | 457篇 |
2001年 | 398篇 |
2000年 | 327篇 |
1999年 | 271篇 |
1998年 | 242篇 |
1997年 | 263篇 |
1996年 | 212篇 |
1995年 | 186篇 |
1994年 | 120篇 |
1993年 | 79篇 |
1992年 | 79篇 |
1991年 | 55篇 |
1990年 | 47篇 |
1989年 | 45篇 |
1988年 | 40篇 |
1987年 | 24篇 |
1986年 | 6篇 |
1985年 | 15篇 |
1984年 | 14篇 |
1983年 | 8篇 |
1982年 | 13篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1963年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
121.
对Ni-P-Si3N4复合镀层的显微硬工、耐磨性及结合强度进行了测试。结果表明:化学沉积Ni-P-Si3N4合金是一种值得推广应用的新耐磨镀层。 相似文献
122.
Friction and wear resistance are two vital tribological properties of polymer-based materials but optimization of both is rarely attempted. We have investigated blends of 70 wt% poly(vinylidene fluoride) (PVDF)+30% ultra high molecular weight polyethylene, the latter either un-irradiated or else γ-irradiated. Each sample contained varying amounts of carbon black (CB) and also had a varied degree of crosslinking and irradiation dose. We have determined static and dynamic friction, scratch resistance, and sliding wear in multiple scratching tests. Effects of the irradiation dose and CB concentration have been quantified. The electric conductivity threshold is reflected in a drop of static friction; formation of a continuous phase of the lubricant affects tribology as well as electrical properties—both for irradiated and for un-irradiated samples. The scratch resistance as represented by the residual (healing) depth is affected by crosslinking, by the stage at which irradiation is applied (before or after blending) and by CB addition. Crosslinking by moderate amounts of irradiation provides shallower residual depths while higher doses cause adverse results. Similarly, the CB lubricant can either improve or worsen the scratch resistance. A combination of both approaches produces either better or else worse results than crosslinking alone. Lower friction seems accompanied by higher scratch resistance. A combination of a specific irradiation dose and an optimized CB concentration lowers the sliding wear significantly. Strain hardening in sliding wear determination takes place for all materials studied, irrespective of the extent or radiation-induced crosslinking and of the presence and concentration of carbon black. 相似文献
123.
ABSTRACTUnderstanding the cut and chip (CC) effect in rubber is important for successful product development for tires used in off-road or poor road conditions and for other demanding applications of rubber. This research describes a laboratory testing method for characterising the CC fracture behaviour of rubber using a device that controls and records multiple applied loads and displacements during cyclic impact to the surface of a solid rubber specimen to mimic and quantify the CC damage experienced by tire tread compounds. To study the capabilities of the instrument, three model compounds were studied that are based on carbon black reinforced compounds of common elastomers used in tire treads: natural rubber (NR), styrene-butadiene rubber (SBR), and butadiene rubber (BR). These polymers have well-established CC tendencies in field performance of tire treads, with NR exhibiting the best CC resistance followed by SBR and finally BR. The same trend was found with the rubber impact testing approach that allowed the CC behaviour to be quantified using a new physical parameter which is the CC propensity (P). The relative ranking for CC resistance for the three compounds followed the fatigue crack growth resistances of the materials but was exactly opposite to the ranking of DIN abrasion resistance. This provides evidence that CC damage from impact by mm-scale asperities and abrasion of rubber against μm-scale asperities exhibit distinct characteristics in rubber. 相似文献
124.
Micrometer and nanometer TiO2 particle‐filled poly(phthalazine ether sulfone ketone) (PPESK) composites with various filler volume fractions from 0.5 to 7.5 vol % were prepared by heating compression molding. The friction and wear behaviors of the PPESK composites were evaluated using the block‐on‐ring test rig by sliding PPESK‐based composite blocks against a mild carbon steel ring under dry friction conditions. The wear debris and the worn surfaces of the PPESK composites filled with micrometer and nanometer TiO2 particles were investigated by using a scanning electron microscope (SEM), while the structures of PPESK composites and wear debris were analyzed with IR spectra. Experimental results show that antiwear properties of the PPESK composites can be improved greatly by filling nanometer TiO2 particles, and the friction coefficient decreases when the filler volume fraction is below 2.5%, but when the filler volume fraction is above 2.5% the friction coefficient increases gradually with increasing filler volume fraction. In the case of micrometer TiO2 filler, wear rates increase with increasing filler volume fractions under identical test conditions, and the friction coefficients are less sensitive to the filler volume fraction. It was also found that the wear mechanism of micrometer TiO2 particle‐filled PPESK is mainly severe adhesion and abrasive wear, while that of nanometer TiO2 particle‐filled PPESK is mainly slight abrasive wear. In the former case, there are no transfer film formed on the surface of the counterpart steel, and wear debris are in the form of long and large ribbon. While in the latter case, the wear debris was granule and their size was about 10 μm. In case of 1 vol % nanometer TiO2 particle‐filled PPESK composites, the transfer film was fairly thinner and smoother, and the transfer film provided better coverage on the surface of steel ring, while that of 7.5 vol % was thicker and discrete. These account for the different friction and wear behavior of micrometer and nanometer TiO2 particle‐filled PPESK composite. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 906–914, 2004 相似文献
125.
本文叙述了制备透明、耐磨有机硅树脂的方法;水解催化剂、烷氧基硅烷组成、添加二氧化硅、溶剂成分、促粘和固化催化剂的研究进展 相似文献
126.
费青 《辽东学院学报(自然科学版)》2010,17(2):143-150
文章系统研究分析了针布的衰退,针布磨损与梳理作用、产品质量的关系,详细系统介绍了磨损的种类及其机理,并介绍和分析了针布钢丝材质和热处理工艺的研究及改进,特别论述了采用高碳低合金钢和采用某些合金元素、稀土元素对针布齿(针)尖的金相组织、耐磨性能的作用,将使针布在制造、开发、研究、质量提高和销售服务中发挥更大的作用。 相似文献
127.
Given that fretting wear causes failure in steel wires, we carried out tangential fretting wear tests of steel wires on a self-made fretting wear test rig under contact loads of 9 and 29 N and fretting amplitudes ranging from 5 to 180 μm. We observed morphologies of fretted steel wire surfaces on an S-3000N scanning electron microscope in order to analyze fretting wear mecha-nisms. The results show that the fretting regime of steel wires transforms from partial slip regime into mixed fretting regime and gross slip regime with an increase in fretting amplitudes under a given contact load. In partial slip regime, the friction coefficient has a relatively low value. Four stages can be defined in mixed fretting and gross slip regimes. The fretting wear of steel wires in-creases obviously with increases in fretting amplitudes. Fretting scars present a typical morphology of annularity, showing slight damage in partial slip regime. However, wear clearly increases in mixed fretting regime where wear mechanism is a combination of plastic deformation, abrasive wear and oxidative wear. In gross slip regime, more severe degradation is present than in the other regimes. The main fretting wear mechanisms of steel wires are abrasive wear, surface fatigue and friction oxidation. 相似文献
128.
阐述循环流化床锅炉炉内受热面的磨损机理,从运行参数和床料特性两方面分析引起受热面磨损的原因,提出超音速电弧喷涂技术对炉内水冷壁进行处理的有效措施。文中详细介绍了超音速电弧喷涂的材料、喷涂工艺、涂层基本参数,并计算出由于喷涂技术的采用而对35 t/h、75 t/h和130 t/h的循环流化床锅炉产生的经济效益。 相似文献
129.
为了提高定期维修的刀具所加工的产品质量,减少停机时间和生产成本.考虑生产过程中工件尺寸的残差是时间的函数,利用Glejser检验方法,拟合工件尺寸残差符合的递增型异方差模型,提出了刀具磨损过程的过程能力指数计算方法;使用Bernstein概率密度函数描述刀具寿命和刀具磨损过程的一般特征,在每一个维修周期内均满足顾客要求的最小过程能力指数基础上,考虑质量损失、换刀成本、由刀具的突然失效引发的惩罚成本及维修刀具所需的成本,将过程能力与成本相结合,提出了用于确定最佳刀具初始状态和维修周期的模型.该模型为实际生产提供了一种离线的刀具管理方法. 相似文献
130.
在大量的现场试验与理论研究的基础上,充分考虑到冷轧生产过程中的设备与工艺特点,将磨损机理与轧制过程中实际磨损数据的测量结果有机结合,建立了一套既考虑机理又考虑工况、不但适用于对称磨损而且适用于不对称磨损的工作辊预报模型,并将其应用到宝钢冷轧薄板厂1220五机架冷连轧机的生产实践,有效的保证了工作辊磨损的预报精度,为辊型设计、板形控制奠定了坚实的理论基础,提高了产品的板形质量,为企业创造了较大的经济效益,具有进一步推广应用的价值。 相似文献