全文获取类型
收费全文 | 101304篇 |
免费 | 8070篇 |
国内免费 | 4489篇 |
专业分类
电工技术 | 2403篇 |
技术理论 | 5篇 |
综合类 | 7617篇 |
化学工业 | 12510篇 |
金属工艺 | 18647篇 |
机械仪表 | 4529篇 |
建筑科学 | 18201篇 |
矿业工程 | 1492篇 |
能源动力 | 1331篇 |
轻工业 | 8083篇 |
水利工程 | 1143篇 |
石油天然气 | 2429篇 |
武器工业 | 569篇 |
无线电 | 8135篇 |
一般工业技术 | 10888篇 |
冶金工业 | 13672篇 |
原子能技术 | 540篇 |
自动化技术 | 1669篇 |
出版年
2024年 | 233篇 |
2023年 | 1005篇 |
2022年 | 2431篇 |
2021年 | 2752篇 |
2020年 | 2876篇 |
2019年 | 2281篇 |
2018年 | 1951篇 |
2017年 | 3076篇 |
2016年 | 3172篇 |
2015年 | 3657篇 |
2014年 | 5957篇 |
2013年 | 5642篇 |
2012年 | 7310篇 |
2011年 | 8016篇 |
2010年 | 6170篇 |
2009年 | 6396篇 |
2008年 | 5283篇 |
2007年 | 7030篇 |
2006年 | 6549篇 |
2005年 | 5561篇 |
2004年 | 4564篇 |
2003年 | 3841篇 |
2002年 | 3367篇 |
2001年 | 2809篇 |
2000年 | 2337篇 |
1999年 | 1912篇 |
1998年 | 1447篇 |
1997年 | 1310篇 |
1996年 | 1092篇 |
1995年 | 860篇 |
1994年 | 768篇 |
1993年 | 558篇 |
1992年 | 465篇 |
1991年 | 347篇 |
1990年 | 253篇 |
1989年 | 197篇 |
1988年 | 118篇 |
1987年 | 56篇 |
1986年 | 33篇 |
1985年 | 29篇 |
1984年 | 23篇 |
1983年 | 20篇 |
1982年 | 21篇 |
1981年 | 16篇 |
1980年 | 46篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1975年 | 3篇 |
1959年 | 11篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
《Oil and Energy Trends》2019,44(8):58-60
Currency exchanges rates – updated monthly. Economic indicators of industrial production. Countries included: France, Germany, Italy, the United Kingdom, the United States, Canada, Japan (Total G-7), Eurozone and Total EU-28 (Total OECD). Updated monthly. Economic indicators of car registration in the United States, Canada, France, Germany, Italy, Poland, Spain, Turkey, the United Kingdom, Japan, Republic of Korea and Other OECD (Total OECD-30). Updated monthly. Monthly averages of crude steel production in thousand metric tons for the United States, Canada, Brazil, Mexico, Austria, Belgium, Czech Republic, France, Germany, Italy, Netherlands, Poland, Spain, Sweden, Turkey, the United Kingdom, Russia, Ukraine, South Africa, Iran, China, India, Japan, Republic of Korea, Taiwan and Australia. 相似文献
52.
53.
《International Journal of Hydrogen Energy》2020,45(7):4054-4064
The feasibility of microbial hydrogen consumption to mitigate the hydrogen embrittlement (HE) under different cathodic potentials was evaluated using the Devanathan-Stachurski electrochemical test and the hydrogen permeation efficiency η. The hydrogen permeation efficiency η in the presence of strain GA-1 was lower than that in sterile medium. The cathodic potential inhibited the adherence of strain GA-1 to AISI 4135 steel surface, thereby reducing the hydrogen consumption of strain GA-1. The adherent GA-1 cells were capable of consuming ‘cathodic hydrogen’ and reducing the proportions of absorbed hydrogen, indicating that it is theoretically possible to control HE by hydrogen-consuming microbes. 相似文献
54.
按照管道加工工艺的不同,管道可分为内径控制管和外径控制管。通过热轧工艺生产的外径控制无缝钢管,可满足火力发电厂汽水系统中绝大部分管道的使用要求。对于超(超)临界机组的主蒸汽和高温再热蒸汽管道采用的P91/P92材质的大口径厚壁无缝钢管,由于对材料性能和加工工艺有特殊要求,因此宜采用内径控制管。 相似文献
55.
In this paper, debonding phenomena between carbon fiber reinforced polymer (CFRP) strips and masonry support were investigated on the basis of single-lap shear tests, considering different dimensions of the bond length. To capture the post-peak response of the CFRP–masonry joint, the slip between the support and the reinforcement strip was controlled using a clip gauge positioned at the end of the reinforcement. The tests were simulated by means of a finite element model able to capture the post-peak snap-back behavior due to the failure process. The numerical model is based on zero-thickness interface elements and on a proper non-linear cohesive law. The comparison between experimental and numerical results was performed in terms of overall response, measured by both the machine stroke and the clip gauge positioned at the free end of the reinforcement. The cases of effective bond length greater and lesser than the minimum anchorage length, suggested by the CNR Italian recommendation, were considered. 相似文献
56.
以方竹笋中提取的膳食纤维为研究对象,采用动态高压微射流(dynamic high-pressure micro-fluidization, DHPM)在不同压力条件(0,50,100,150,200 MPa)下进行处理,探究其对竹笋膳食纤维(bamboo shoots dietary fiber, BSDF)理化和结构特性的影响。结果表明,随着处理压力的增大,BSDF粒径先增大后减小,当处理压力为150 MPa时,粒径最小,为(370±11) nm,此条件下BSDF的持水力、持油力和膨胀力达到最大,较对照组分别提高了47.74%,50.54%,61.27%,且差异显著(P<0.05)。红外光谱分析表明DHPM处理不会改变BSDF的官能团,但会使BSDF内部的部分氢键断裂和半纤维素、木质素等发生降解;X射线衍射和热重分析表明DHPM处理不会引起BSDF的晶体结构改变,但晶体有序度会下降,进而导致其热稳定性降低;微观结构分析显示DHPM处理会使BSDF颗粒尺寸减小、表面粗糙、组织松散,且当处理压力为200 MPa时,颗粒发生团聚。综上,DHPM可以有效改善BSDF的理化性质,在膳食纤维改性方面具有一定的应用价值。 相似文献
57.
The toughness of 31Mn2SiRE wear-resistance cast steel were increased by means of RE compound modification and high temperature austenitizing. The results show that the microstructures can be refined, needle and network ferrite are eliminated, the dislocation density and the quantity of dislocated martensite are increased remarkably, and the shape and distribution of inclusions are improved by the addition of RE. Therefore, the mechanical properties of the modified steel can be greatly increased, especially the toughness (αK) by 44%, yield strength (σs) by 10%, and elongation (δ5) by 42%. 相似文献
58.
光纤布拉格光栅的无源温度补偿 总被引:3,自引:1,他引:2
分析了通过施加应变补偿光纤布拉格光栅(FBG)中心波长随温度漂移的原理,给出了一种新型的无源温度补偿的方法和相应的实验结果。该方法采用了两种不同热膨胀系数的金属,对光栅先施加预应变。在0-60℃范围内,中心波长仅偏移了0.02nm。 相似文献
59.
60.
Yang Aiying Wang Ziyu Zhang Zhaoyi Chen Zhangyuan Wu Deming 《电子科学学刊(英文版)》2003,20(6):461-466
A 10Gbit/s recirculating system is configured with Chirped Fiber Bragg Grating (CFBG) for the dispersion compensation. For the first time, the transmission distance in the loop reaches 1000km with bit error rate of 10-9. The effect of the group delay ripple of the fiber grating is also investigated in the recirculating systems, and it is shown that the transmission distance is limited to 4 cycles (4×167.1km ) in the loop with the power penalty fluctuation below 1.0dB. Thus the group delay ripple should be reduced to allow for the wavelength drift of±5GHz. At the end of this letter, the principles are given for designing long haul recirculating systems with dispersion compensation CFBG. 相似文献