全文获取类型
收费全文 | 180666篇 |
免费 | 9386篇 |
国内免费 | 4659篇 |
专业分类
电工技术 | 6390篇 |
技术理论 | 6篇 |
综合类 | 8401篇 |
化学工业 | 27633篇 |
金属工艺 | 10791篇 |
机械仪表 | 9871篇 |
建筑科学 | 10217篇 |
矿业工程 | 3938篇 |
能源动力 | 3995篇 |
轻工业 | 9767篇 |
水利工程 | 2913篇 |
石油天然气 | 7661篇 |
武器工业 | 813篇 |
无线电 | 19703篇 |
一般工业技术 | 27383篇 |
冶金工业 | 7479篇 |
原子能技术 | 1278篇 |
自动化技术 | 36472篇 |
出版年
2024年 | 457篇 |
2023年 | 1787篇 |
2022年 | 3128篇 |
2021年 | 4262篇 |
2020年 | 3334篇 |
2019年 | 2705篇 |
2018年 | 16874篇 |
2017年 | 16260篇 |
2016年 | 12685篇 |
2015年 | 4715篇 |
2014年 | 5147篇 |
2013年 | 6031篇 |
2012年 | 9376篇 |
2011年 | 15923篇 |
2010年 | 13864篇 |
2009年 | 10909篇 |
2008年 | 11999篇 |
2007年 | 12732篇 |
2006年 | 5517篇 |
2005年 | 5902篇 |
2004年 | 4087篇 |
2003年 | 3980篇 |
2002年 | 3191篇 |
2001年 | 2511篇 |
2000年 | 2505篇 |
1999年 | 2696篇 |
1998年 | 2134篇 |
1997年 | 1757篇 |
1996年 | 1748篇 |
1995年 | 1424篇 |
1994年 | 1169篇 |
1993年 | 745篇 |
1992年 | 657篇 |
1991年 | 462篇 |
1990年 | 350篇 |
1989年 | 302篇 |
1988年 | 236篇 |
1987年 | 150篇 |
1986年 | 122篇 |
1985年 | 70篇 |
1984年 | 53篇 |
1983年 | 44篇 |
1982年 | 41篇 |
1968年 | 43篇 |
1966年 | 42篇 |
1965年 | 45篇 |
1959年 | 37篇 |
1958年 | 37篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 16 毫秒
111.
Fenton氧化法去除酱油生产废水中焦糖色素的研究 总被引:1,自引:0,他引:1
着重考察了Fenton试剂对水中焦糖色素降解的影响因素.从试验中得出,这些影响因素包括pH、催化剂的投加方式、催化剂与氧化剂的化学计量数以及反应时间等.Fenton反应中,pH4的条件下处理效果最好,反应进行40min时去除率达到90%. 相似文献
112.
Wang Xuping Wang Jiyang Hu Xiaobo Zhang Jianxiu Zhao Hongyang Huang Wanxia Zhu Peiping 《中国稀土学报(英文版)》2006,24(Z1)
Langasite single crystal was grown by the Czochralski method and its perfection was assessed by white beam synchrotron radiation topography. It is found that the growth core and the growth striations are the primary growth defects and they show strong X-ray kinematical contrast in the topographs. Another typical defect in LGS crystal is dislocation. The formation mechanisms of these growth defects in LGS crystals were discussed. 相似文献
113.
Gert Schubring 《NTM》2003,11(2):90-99
Enno Heeren Dirksen (1788–1850) was one of several mathematicians originating from Eastern Frisia at the end of the eighteenth
century to acquire prominence in neohumanist reformed Prussia. While striving—like so many of his contemporaries—for more
rigour in the foundations of calculus, his work is significant due to his unusual emphasis on the semiotic aspects of the
basic concepts. As a clear-sighted propagator of Cauchy's conceptual innovations in Germany, his achievements in improving
sign expressions of such concepts enabled him to clarify hitherto not differentiated multiple limit processes—although less
successfully in constructive concept formation itself.
The contribution is based on the analysis of Dirksen's published texts and on the numerous texts which remained drafts for
his projected voluminousOrganon der gesamten Analysis.
Menso Folkerts zum 60. Geburtstag gewidmet 相似文献
Menso Folkerts zum 60. Geburtstag gewidmet 相似文献
114.
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
115.
Yu Zhao Zhigang Xu Zongshi Li Weihong Qiao Lubai Cheng 《Petroleum Science and Technology》2006,24(7):821-827
Heavy alkyl benzene sulfonates (HABS) were synthesized, and their interfacial tensions were measured and compared with those of petroleum sulfonates ORS-41. Effects of their coupling with lignosulfonate were also studied. The results showed that HABS exhibited good interfacial activities and the system of HABS blending with LS displayed better interfacial activities than ORS-41 and therefore reduced the prime cost. Their best proportions of synergism were from 3:1 to 4:1. HABS might be a more promising alkali-surfactant-polymer (ASP) flooding agent. 相似文献
116.
Zhao M. Shea J. D. Hagness S. C. van der Weide D. W. 《Microwave and Wireless Components Letters, IEEE》2006,16(12):675-677
We present a 3-12 GHz compact mixer-based reflectometer (CMR) and horn antenna system, and demonstrate its use in detecting backscatter signals with a free space calibration procedure. We evaluate the frequency-domain performance of the CMR-antenna system for measuring the complex reflection coefficient of a dielectric slab and compare it with that of a commercial vector network analyzer (VNA)-antenna setup. Time-domain responses are also investigated, and show the effectiveness of this calibration method. This low-cost, compact system eliminates the need for traditional mechanical standards and a VNA, is effective in reducing reflection artifacts, and allows for flexibility in the placement of reference planes; thus it is well suited for array-based imaging applications 相似文献
117.
用于制备膨体颗粒调剖剂的含油污泥除油技术研究 总被引:1,自引:0,他引:1
利用含油污泥制备膨体颗粒调剖剂用于调剖堵水是一种新的污泥资源化技术,研究了含油污泥的预处理方法,尤其是除油技术。分别使用热水酸洗、热水酸洗/除油剂对污泥进行了除油试验,并以干泥含油率为指标考察了pH值、水与泥质量比、除油剂用量对除油效果的影响。试验结果表明,在水与泥质量比为2.0、pH值为6.0、45℃条件下,用矿化水热水酸洗可使干泥含油率从31.5%降至19.4%。同样条件下,除油剂用量为40.0mg/L时,热水酸洗/除油剂处理能使干泥含油率进一步降至11.2%。聚合试验结果表明,经热水酸洗/除油剂处理后的污泥能够聚合得到胶块强度高、膨胀倍数高的膨体颗粒调剖剂。 相似文献
118.
Ferrite particles coated with biocompatible phases can be used for hyperthermia treatment of cancer. We have synthesized substituted
calcium hexaferrite, which is not stable on its own but is stabilized with small substitution of La. Hexaferrite of chemical
composition (CaO)0.75(La203)0.20(Fe2O3)6 was prepared using citrate gel method. Hydroxyapatite was prepared by precipitating it from aqueous solution of Ca(NO3)2 and (NH4)2HPO4 maintaining pH above 11. Four different methods were used for coating of hydroxyapatite on ferrite particles. SEM with EDX
and X-ray diffraction analysis shows clear evidence of coating of hydroxyapatite on ferrite particles. These coated ferrite
particles exhibited coercive field up to 2 kOe, which could be made useful for hysteresis heating in hyperthermia. Studies
by culturing BHK-21 cells and WBC over the samples show evidence of biocompatibility. SEM micrographs and cell counts give
clear indication of cell growth on the surface of the sample. Finally coated ferrite particle was implanted in Kasaulli mouse
to test its biocompatibility. The magnetic properties and biocompatibility studies show that these hydroxyapatite coated ferrites
could be useful for hyperthermia. 相似文献
119.
Xue‐Yong Liu Xiao‐Bin Ding Zhao‐Hui Zheng Yu‐Xing Peng Albert S
C Chan C
W Yip Xin‐Ping Long 《Polymer International》2003,52(2):235-240
Amphiphilic magnetic microspheres ranging in diameter from 5 to 100 µm were prepared by dispersion copolymerization of styrene and poly(ethylene oxide) vinylbenzyl (PEO‐VB) macromonomer (MPEO) in the presence of Fe3O4 magnetic fluid. The effects of various polymerization parameters on the average particle size were systematically investigated. The average particle size was found to increase with increasing styrene concentration and initiator concentration. It also increased with decreasing stabilizer concentration and molecular weight of MPEO. The content of the hydroxyl groups localized in the microspheres ranged from 0.01 to 0.2 mmol g?1. © 2003 Society of Chemical Industry 相似文献
120.
针对石油化工生产的特点,从物料特性、上艺装置、工艺控制参数、防火防爆安全装置、作业性质和消防安全设施等几方面综合分析其火灾危险性,并提出相应的防范措施,为消防安全评价提供依据。 相似文献