全文获取类型
收费全文 | 3375篇 |
免费 | 205篇 |
国内免费 | 16篇 |
专业分类
电工技术 | 65篇 |
综合类 | 7篇 |
化学工业 | 756篇 |
金属工艺 | 79篇 |
机械仪表 | 84篇 |
建筑科学 | 115篇 |
矿业工程 | 3篇 |
能源动力 | 211篇 |
轻工业 | 316篇 |
水利工程 | 37篇 |
石油天然气 | 80篇 |
无线电 | 425篇 |
一般工业技术 | 639篇 |
冶金工业 | 123篇 |
原子能技术 | 13篇 |
自动化技术 | 643篇 |
出版年
2024年 | 12篇 |
2023年 | 118篇 |
2022年 | 233篇 |
2021年 | 275篇 |
2020年 | 182篇 |
2019年 | 179篇 |
2018年 | 223篇 |
2017年 | 168篇 |
2016年 | 177篇 |
2015年 | 110篇 |
2014年 | 138篇 |
2013年 | 277篇 |
2012年 | 180篇 |
2011年 | 195篇 |
2010年 | 137篇 |
2009年 | 138篇 |
2008年 | 107篇 |
2007年 | 72篇 |
2006年 | 80篇 |
2005年 | 70篇 |
2004年 | 55篇 |
2003年 | 37篇 |
2002年 | 41篇 |
2001年 | 32篇 |
2000年 | 25篇 |
1999年 | 30篇 |
1998年 | 38篇 |
1997年 | 20篇 |
1996年 | 25篇 |
1995年 | 15篇 |
1994年 | 19篇 |
1993年 | 22篇 |
1992年 | 19篇 |
1991年 | 8篇 |
1990年 | 8篇 |
1989年 | 16篇 |
1988年 | 16篇 |
1987年 | 6篇 |
1986年 | 12篇 |
1985年 | 11篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1978年 | 8篇 |
1977年 | 5篇 |
1976年 | 7篇 |
1974年 | 4篇 |
排序方式: 共有3596条查询结果,搜索用时 15 毫秒
961.
Mn3O4 nanoparticles were prepared by a simple solid state decomposition method. Four manganese benzoic acid complexes were synthesized through semi-solid phase reaction method as precursors for the preparation of Mn3O4 nanoparticles. The calcination temperature of the precursors was determined from thermal gravimetrical analyses (TGA). The resulting nanoparticles were characterized by XRD, SEM, STM and HRTEM. The obtained particle size is in the range 39–90 nm. HRTEM indicated the formation of spherical nanoparticles. The optical absorption measurements for the obtained nanoparticles showed that the fundamental absorption edge obeys Tauc's relation for the allowed direct transition. It was found that, the optical band gap (Eg) increases with the decrease of the particle size of the Mn3O4 nanoparticles. 相似文献
962.
Al-Qurabat Ali Kadhum M. Mohammed Zahraa A. Hussein Zahraa Jabbar 《Wireless Personal Communications》2021,119(3):2227-2237
Wireless Personal Communications - When dynamic nature, autonomous, self- configured types nodes are combined together and make contact with each other for the purpose of communication and data... 相似文献
963.
964.
Sayed Wafaa S. Tolba Mohammed F. Radwan Ahmed G. Abd-El-Hafiz Salwa K. 《Multimedia Tools and Applications》2019,78(12):16097-16127
Multimedia Tools and Applications - This paper proposes a generalized modified chaotic transition map with three independent parameters. A hardware speech encryption scheme utilizing this map along... 相似文献
965.
Alhayani Bilal Abbas Sara Taher Mohammed Husam Jasim Mahajan Hemant B. 《Wireless Personal Communications》2021,120(1):665-700
Wireless Personal Communications - Two-way image communication in a wireless channel needs to be viable with channel properties such as transfer speed, energy-effective, time usage, and security... 相似文献
966.
967.
Mohammed A. Quader Dhiren Kumar Keyur B. Shah Yahya I. Fatani Gundars Katlaps Vigneshwar Kasirajan 《Hemodialysis international. International Symposium on Home Hemodialysis》2014,18(1):205-209
Dialysis centers adopt a cautious approach when it comes to performing intermittent hemodialysis (HD) on patients with continuous flow (CF) left ventricular assist devices (LVADs) because of the potential for volume flux‐related complications and absence of pulsatile blood pressure for monitoring. Many patients have to remain hospitalized because of the inability of the dialysis centers to accept them for outpatient dialysis. In this study, the effect of HD was observed in such patients. Between June 2009 and October 2012, 139 patients received LVADs, of which 10 patients (7%) required intermittent HD postoperatively. The mean age of the patients was 53 ± 14 years and 90% were men. A total of 281 dialysis sessions were administered amounting to 1025 hours of dialysis. The mean systolic blood pressure monitored with Doppler device was 97 ± 18 mmHg. Dialysis durations averaged 218 ± 18 minutes. Mean blood flow rate was 334 ± 38 cc/min, and 2.6 ± 1.1 L was ultrafiltrated during each session. Only 15 (5.3%) sessions were interrupted or terminated in six patients. The reasons for termination were symptomatic hypotension—6 (2.1%), asymptomatic hypotension—3 (1%), ventricular tachycardia—1 (0.36%), dialysis machine malfunction—2 (0.7%), low phosphorus—2 (0.7%), and abdominal cramps—1 (0.36%). Volume expansion was necessary on three occasions. Low‐flow device alarms were registered during two (0.71%) sessions. The results showed no serious adverse effects or deaths. 相似文献
968.
969.
R. Saidur G. BoroumandJaziS. Mekhilef H.A. Mohammed 《Renewable & Sustainable Energy Reviews》2012,16(2):1217-1222
Renewable energy sources can be a good substitute of the fossil fuels which are being terminated fast. Nowadays biomass and biofuels are considered because of their environment friendly characteristics and their ability of supplying much more energy. An alternative means to select the most efficient and convenient biomass, is exergy analysis. The present paper has reviewed the existent surveys on the exergy analysis of different kind of biomass included the woody biomass, herbaceous and agricultural biomass, aquatic biomass, contaminated biomass and industrial biomass. The most common thermochemical processes are investigated and the efficiency of the different process and various kinds of biomass are determined. 相似文献
970.
Experimental Study of Sand and Slurry Jets in Water 总被引:1,自引:0,他引:1
Neil Hall Mohammed Elenany David Z. Zhu N. Rajaratnam 《Canadian Metallurgical Quarterly》2010,136(10):727-738
This paper presents the results of an experimental study of turbulent sand jets and sand-water slurry jets impinging vertically into a stagnant water body. The jets contained silica sand with a median diameter D50 of 206?μm, and with an initial concentration 0.60 by volume for the sand jets, and 0.055–0.124 by volume for the slurry jets. The jets had densimetric Froude numbers between 2.0 and 5.94. The sand concentration and velocity profiles were measured simultaneously using a novel fiber optical probe, up to a distance of 130do for sand jets, and 65do for slurry jets, where do is the jet diameter at the water surface. The jets were found to have self-similar Gaussian profiles. The centerline sand concentration within the jets was found to decrease rapidly, following trends similar to single phase plumes. The centerline sand velocity profile decreased significantly before reaching a plateau region. The “terminal” centerline sand velocity within this region varies somewhat depending upon sand mass flux, and is between 0.32 and 0.43 m/s. The spreading rates of the jets were found to vary with the particle Froude number. Within the sand jets and the higher Froude number slurry jet, the sand concentration had a smaller spreading rate than the velocity. The other slurry jets had equal concentration/velocity spreading rates. The momentum flux of the sand within the jets was found to decrease sharply, followed by a constant flux below a depth of 25 to 30 jet diameters. 相似文献