全文获取类型
收费全文 | 14518篇 |
免费 | 1514篇 |
国内免费 | 629篇 |
专业分类
电工技术 | 1564篇 |
综合类 | 1292篇 |
化学工业 | 1507篇 |
金属工艺 | 786篇 |
机械仪表 | 1009篇 |
建筑科学 | 1644篇 |
矿业工程 | 251篇 |
能源动力 | 2393篇 |
轻工业 | 511篇 |
水利工程 | 361篇 |
石油天然气 | 537篇 |
武器工业 | 90篇 |
无线电 | 668篇 |
一般工业技术 | 1945篇 |
冶金工业 | 512篇 |
原子能技术 | 377篇 |
自动化技术 | 1214篇 |
出版年
2024年 | 43篇 |
2023年 | 207篇 |
2022年 | 492篇 |
2021年 | 579篇 |
2020年 | 531篇 |
2019年 | 471篇 |
2018年 | 442篇 |
2017年 | 519篇 |
2016年 | 627篇 |
2015年 | 582篇 |
2014年 | 919篇 |
2013年 | 1025篇 |
2012年 | 931篇 |
2011年 | 1231篇 |
2010年 | 815篇 |
2009年 | 824篇 |
2008年 | 717篇 |
2007年 | 846篇 |
2006年 | 741篇 |
2005年 | 654篇 |
2004年 | 578篇 |
2003年 | 490篇 |
2002年 | 435篇 |
2001年 | 343篇 |
2000年 | 251篇 |
1999年 | 265篇 |
1998年 | 188篇 |
1997年 | 157篇 |
1996年 | 149篇 |
1995年 | 122篇 |
1994年 | 97篇 |
1993年 | 65篇 |
1992年 | 61篇 |
1991年 | 46篇 |
1990年 | 43篇 |
1989年 | 32篇 |
1988年 | 20篇 |
1987年 | 24篇 |
1986年 | 18篇 |
1985年 | 16篇 |
1984年 | 22篇 |
1983年 | 6篇 |
1982年 | 13篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1979年 | 6篇 |
1963年 | 1篇 |
1959年 | 1篇 |
1956年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
以某一新型二代水泥技术的7 000 t/d熟料生产线为例,单纯的采用汽水朗肯循环,存在热量回收不彻底,部分低品位余热资源无法有效回收等问题。采用汽水朗肯循环及有机朗肯循环联合发电系统的方案,结果表明:联合朗肯循环系统发电功率提高了614 kW,吨熟料发电量增加了2.1 kWh/kg,提高了8%;净发电功率提高了511 kW,净发电量实际提高了7.1%,提高了水泥余热回收的效率。 相似文献
102.
利用金属原位分析技术和钻孔化学分析方法对高淬透性轴承钢GCr15SiMn的Φ450 mm连铸圆坯和Φ130 mm圆钢的C、Si、Mn、Cr元素横截面的分布情况进行分析。采用推力片式接触疲劳试验机进行了材料的接触疲劳寿命测试。结果表明:GCr15SiMn连铸圆坯C元素的偏析倾向较大,易产生中心正偏析,而Cr、Si、Mn元素的偏析倾向较小。通过采取稳定低过热度浇铸、三段强电磁搅拌等措施,铸坯的中心碳偏析得以改善。采用(1240±20)℃×5 h高温扩散、初轧首道次变形量≥90 mm大变形轧制的Φ130 mm圆钢的碳偏析可以得到进一步的改善,试验钢在5.3GPa高应力负载下的接触疲劳额定寿命L10达到3.58×106次,接近电渣重熔钢的水平。 相似文献
103.
104.
研究了快淬工艺对无钴AB5型LaxMm1-x(NiMnSiAlFe)4.9(x=0,0.45,0.75,1.0)合金微观结构及电化学循环稳定性的影响.结果表明快淬处理显著改善合金的成分均匀性,使晶粒细化,并显著提高合金的循环稳定性.当淬速从0m/s增加到28 m/s时,经300次充放循环后,x=0.45合金的容量衰减率D从0.28 mAh/g·c-1(c代表一次循环)下降到0.13mAh/g·c-1;x=1.0合金的容量衰减率D从0.3mAh/g·c-1下降到0.14mAh/g·c-1. 相似文献
105.
Fe替代Co对AB5型贮氢合金循环稳定性的影响 总被引:2,自引:0,他引:2
用铸造及快淬的方法制备了稀土基AB5型Mm(NiMnSiAl)4.3Co0.6-xFex(x=0,0.1,0.2,0.3,0.4,0.5,0.6)贮氢合金,用XRD。TEM及SEM观测了铸态及快淬态的微观结构,测试了合金在铸态及快淬态下的电化学循环稳定性。研究了Fe替代Co对铸态及快淬态贮氢合金微观结构及循环稳定性的影响。研究结果表明,Fe替代Co对铸态及快淬态合金的相结构没有明显影响,但对合金的循环稳定性产生显著影响。Fe替代Co能不同程度地改善铸态及快淬态合金的循环稳定性,但对快淬态合金循环寿命的改善更加显著,导致这一结果的主要原因是Fe替代Co使快淬态合金的微观组织显著细化。 相似文献
106.
为了提高低钴AB5型贮氢合金的电化学循环稳定性,在低钴AB5型贮氢合金中加入微量的硼,用真空快淬工艺制备了稀土系低钴AB5型MmNi3.8Co0.4Mn0.6Al0.2Bx(x=0,0.1,0.2,0.3,0.4)贮氢合金,分析测试了铸态及快淬态合金的电化学性能及微观结构,研究了硼对铸态及快淬态合金微观结构及循环寿命的影响。结果表明,硼能大幅度提高铸态及快淬态低钴AB5型贮氢合金的电化学循环稳定性,但其作用机理是完全不同的。 相似文献
107.
Weighting model is the only valuation model of life cycle impact assessment(LCIA) profile now. It simplifies evaluation function into linear function, and makes the determination of weighting factor complicated. Therefore the valuation of LCIA profile is the most critical and controversial step in life cycle assessment(LCA). Development on valuation models, which are understood easily and accepted widely, is urgently needed in the field of LCA.The modeling approaches for the linear evaluation function were summed up. The modeling approaches for the nonlinear evaluation function were set up by function approximation theory, which include choosing preference products, forming preference data, establishing artificial neural network(ANN) and training ANN by preference data.By selecting 7 material products as preference product, experience was done with modeling approaches of the nonlinear evaluation function. The results show that the modeling approaches and valuation model of the nonlinear evaluation function are more practical than the weighting model. 相似文献
108.
High cycle fatigue behaviour of Ti–6Al–4V alloy was studied at 623 K and 723 K. Fatigue strength decreased at elevated temperatures compared with at ambient temperature. In the short life regime, fatigue strength was lower at 723 K than at 623 K, but in the long life regime it was nearly the same at both temperatures. At elevated temperatures, cracks were generated earlier at applied stresses below the fatigue limit at ambient temperature, indicating lowered crack initiation resistance. Small cracks grew faster at elevated temperatures than at ambient temperature, which became more noticeable with increasing temperature. After allowing for the elastic modulus, small cracks still grew faster at elevated temperatures. 相似文献
109.
The application of a new approach, design for performance, for high-temperature alloy development, design analysis, and remaining
life assessment, based on short-time high-precision testing, is described in this paper. The material tested was a directionally
solidified nickel-base alloy, GTD111. It was found that the creep strength at 850 °C was indeed superior to that of a competitive
alloy, IN738, but was not necessarily enhanced by the preferred alignment of grain boundaries and crystal orientation. In
contrast, the fracture resistance at 800 °C was improved in the longitudinal direction compared with transverse and diagonal
orientations in terms of susceptibility to gas phase embrittlement (GPE) by oxygen. Specimens cut transversely and diagonally
to the growth direction were more sensitive to GPE than specimens taken from conventionally cast IN738. The new conceptual
framework allows account to be taken of GPE and other embrittling phenomena, which may develop in service, leading to rational
life management decisions for gas turbine users. Additionally, straightforward design analysis procedures can be developed
from the test data, which for the first time allow separate measurements of creep strength and fracture resistance to be used
for performance evaluation. 相似文献
110.
E. Westkämper 《CIRP Annals》2003,52(2):579-588
Industrial companies change the paradigms of business operations from optimisation of manufacturing processes to optimisation of products life cycles in order to activate the value of products, taking into account the potentials of product services in all phases of each product's life. From design to the end of their life capital intensive products, like manufacturing or assembly systems, are linked to a manufacturer network by global communication systems. This network allows special services even in the phases of usage and recycling. For this new paradigm it is necessary to develop strategies, methods and technologies to manage the business processes and the information and knowledge required in all phases of a product's life and to industrialise the processes of design, assembly, usage, service and remanufacturing by disassembly and recycling. It is the objective of this paper to define the processes for management of life cycle with a focus on assembly, service and disassembly of capital intensive products. 相似文献