全文获取类型
收费全文 | 7216篇 |
免费 | 961篇 |
国内免费 | 144篇 |
专业分类
电工技术 | 153篇 |
综合类 | 334篇 |
化学工业 | 2146篇 |
金属工艺 | 668篇 |
机械仪表 | 126篇 |
建筑科学 | 387篇 |
矿业工程 | 461篇 |
能源动力 | 71篇 |
轻工业 | 1249篇 |
水利工程 | 48篇 |
石油天然气 | 109篇 |
武器工业 | 21篇 |
无线电 | 562篇 |
一般工业技术 | 1057篇 |
冶金工业 | 813篇 |
原子能技术 | 45篇 |
自动化技术 | 71篇 |
出版年
2024年 | 27篇 |
2023年 | 131篇 |
2022年 | 233篇 |
2021年 | 255篇 |
2020年 | 280篇 |
2019年 | 284篇 |
2018年 | 247篇 |
2017年 | 335篇 |
2016年 | 343篇 |
2015年 | 329篇 |
2014年 | 412篇 |
2013年 | 468篇 |
2012年 | 493篇 |
2011年 | 470篇 |
2010年 | 370篇 |
2009年 | 383篇 |
2008年 | 301篇 |
2007年 | 373篇 |
2006年 | 386篇 |
2005年 | 325篇 |
2004年 | 311篇 |
2003年 | 241篇 |
2002年 | 243篇 |
2001年 | 176篇 |
2000年 | 167篇 |
1999年 | 121篇 |
1998年 | 112篇 |
1997年 | 79篇 |
1996年 | 62篇 |
1995年 | 61篇 |
1994年 | 67篇 |
1993年 | 58篇 |
1992年 | 51篇 |
1991年 | 31篇 |
1990年 | 23篇 |
1989年 | 21篇 |
1988年 | 11篇 |
1987年 | 12篇 |
1986年 | 6篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1982年 | 3篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1974年 | 1篇 |
排序方式: 共有8321条查询结果,搜索用时 0 毫秒
1.
Nanofiber bundles of Ag2S, Ag2Se, and Ag have been successfully synthesized by making use of Ag2C2O4 template nanofiber bundles, utilizing both anion‐exchange and redox reactions. The obtained bundles were polycrystalline nanofibers composed of nanoparticles in which the precursor morphology was well‐preserved, indicating that Ag2C2O4 nanofiber bundles acted as a general sacrificial template for the synthesis of silver‐based semiconductor and metal nanofibers. Dispersing media and transforming reactants were found to be key factors influencing the chemical transformation in the system. In particular, separate single‐crystalline Ag nanofibers were obtained via a nontemplate route when ascorbic acid was used as a relatively weak reductant. An electrical transfer and switching device was built with the obtained Ag2S and Ag nanofiber bundles, utilizing the unique ion‐conductor nature of Ag2S and revealing their potential applications in electronics. 相似文献
2.
Hitoshi Kurokawa Taku Nakayama Yasunori Kobayashi Ken Suzuki Mutsumi Takahashi Seiichi Takami Momoji Kubo Naotsugu Itoh Parasuraman Selvam Akira Miyamoto 《Catalysis Today》2003,82(1-4):233-240
A modified Monte Carlo (MC) simulation was performed to investigate the hydrogen absorption behavior in Pd and Pd–Ag alloys of the composition PdxAg1−x (x=0.7–0.8) under H2 pressure (0.1 MPa) at different temperatures. The present method employed can consider the dissociative adsorption of hydrogen molecule and the subsequent absorption of hydrogen atom by formalizing the relationship between the pressure of hydrogen molecule and hydrogen atom. The potential parameters were determined to reproduce the solution enthalpy of hydrogen in pure metals. The results are in good agreement with experimental findings as well as previous theoretical studies. We confirmed that our method is useful to simulate the absorption of hydrogen in metals and alloys. 相似文献
3.
Javier M. Grau JosM. Bisang 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1992,53(1):105-110
This paper describes the parameters that are important in the industrial practice of silver removal from photographic fixers. The experiments were performed under potentiostatic control using synthetic solutions. The current efficiency was analysed as a function of the cathodic potential taking into account the deposit quality. A cathodic potential of ?0.5 V against a saturated calomel electrode is recommended. The conditions to prevent the darkening of the electrodeposit were investigated. The determination of silver concentration in the solution was made by direct potentiometry. The results obtained with synthetic fixers were corroborated by making the silver deposition from commercial fixers in an electrochemical reactor with rotating cylinder electrode intercalated in an electrolytic flow circuit in order to simulate practical conditions. 相似文献
4.
B. Kwakye‐Awuah I. Radecka M. A. Kenward C. D. Williams 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(9):1255-1260
BACKGROUND: Metal‐exchanged zeolites have been reported to have significant limitations on cayalytic activity, such as counterbalancing the negative framework charges and limitation of active space. Alternative methods of incorporating silver ions into the framework of zeolites are therefore necessary. This paper reports on a technique for producing silver doped analcime by isomorphous substitution of silver ion into the framework of analcime. The amount of aluminium in the gel composition was reduced by a factor of 5%, 10% and 20% and an equivalent amount of silver was added to the gel and treated in a conventional manner for zeolite crystallisation. Some of the aluminium in the reaction gel was replaced with the silver. The silver‐doped analcime samples where characterised by X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X‐rays (EDX), Fourier transform infrared (FTIR) spectroscopy and inductively coupled plasma‐atomic emission spectroscopy (ICP‐AES) analysis. RESULTS: The amount of silver ions loaded for each reduction of aluminium as determined by EDX were found to be (w/w) 0.29%, 1.41% and 2.10%, respectively. XRD pattern SEM images of the silver‐doped analcime showed the presence of zeolite P in addition to analcime. CONCLUSION: Silver‐doped analcime was successfully produced with different silver loadings and may exhibit higher anti‐microbial activities than silver‐exchanged counterparts. Copyright © 2008 Society of Chemical Industry 相似文献
5.
6.
Under the applied high reaction temperatures (900 K) the Ag surface is restructured and a tightly held oxygen species is formed on the surface (O) apart from O atoms dissolved in the bulk (O). Methanol oxidation to formaldehyde proceeds through this O species as demonstrated by application of a variety of spectroscopic techniques. 相似文献
7.
通过实验,发现络合滴定用的指示剂——偶氮胂—Ⅲ,可用作本测定中的沉淀滴定指示剂。根据标准 AgNO_3溶液同 MoO_4~(2-)的定量反应,计算出以硅钼黄 Hg[Si(Mo_2O_7)_6]形式存在的MoO_4~(2-)量,再据以算出硅酸盐中 SiO_2的含量。 相似文献
8.
B. P. Aduev É. D. Aluker A. G. Krechetov A. Yu. Mitrofanov 《Combustion, Explosion, and Shock Waves》2003,39(6):701-703
The velocity of the chain explosivedecomposition reaction in silver azide whiskes has been measured (1500 m/sec). The measured velocity is identified as the propagation velocity of the diffusion front of holes generated in the course of explosive decomposition. 相似文献
9.
非金属电镀用导电漆的研制 总被引:1,自引:0,他引:1
介绍了导电漆、作为导电填料的片状镀银铜粉的制备工艺流程。分别研究了漆膜表面单位电阻与镀银铜粉的含量及其粒径以及钛酸酯偶联剂的含量之间的关系。结果表明,当镀银铜粉的粒径为400目、质量分数在57%~65%之间,钛酸酯偶联剂的质量分数为10%时,所得涂膜的导电性能最佳。加入含C-18的油酸可以使导电漆长期贮存而电阻值不变。经检测,所得涂膜具有良好的性能:附着力1级,硬度1 H,柔韧性1 mm,冲击强度50 kg/cm2,膜厚10~15μm,漆膜表面每厘米电阻0.15Ω,每分米电阻0.47Ω。指出了导电漆应用过程中的注意事项。 相似文献
10.
Impedance spectroscopy study of hardened Portland cement paste 总被引:3,自引:0,他引:3
In this paper, the differential impedance analysis (DIA) has been applied to the study of the dielectric properties of hardened Portland cement paste. Two time constants are found in the impedance spectra obtained in the frequency region form 100 kHz to 15 MHz. One time constant has been attributed to the solid matrix and the other one to the liquid phase filling the pores. The effect of the cement paste-electrodes interface has been quantified using two different experimental set-ups. Measurements using direct contact between electrodes and cement paste have been compared with measurements using an air gap technique in which the specimen “floats” between the electrodes. The two referred time constants have been found in both types of measurements. The influence of drying on the dielectric parameters is also studied. 相似文献