全文获取类型
收费全文 | 145313篇 |
免费 | 6651篇 |
国内免费 | 3253篇 |
专业分类
电工技术 | 4318篇 |
技术理论 | 2篇 |
综合类 | 6305篇 |
化学工业 | 21754篇 |
金属工艺 | 8412篇 |
机械仪表 | 7021篇 |
建筑科学 | 6781篇 |
矿业工程 | 2673篇 |
能源动力 | 2781篇 |
轻工业 | 7507篇 |
水利工程 | 2334篇 |
石油天然气 | 4204篇 |
武器工业 | 528篇 |
无线电 | 16751篇 |
一般工业技术 | 23680篇 |
冶金工业 | 5567篇 |
原子能技术 | 878篇 |
自动化技术 | 33721篇 |
出版年
2024年 | 278篇 |
2023年 | 1082篇 |
2022年 | 1690篇 |
2021年 | 2547篇 |
2020年 | 1929篇 |
2019年 | 1733篇 |
2018年 | 16028篇 |
2017年 | 15224篇 |
2016年 | 11654篇 |
2015年 | 3042篇 |
2014年 | 3232篇 |
2013年 | 3794篇 |
2012年 | 7156篇 |
2011年 | 13713篇 |
2010年 | 11837篇 |
2009年 | 8984篇 |
2008年 | 10056篇 |
2007年 | 10990篇 |
2006年 | 3777篇 |
2005年 | 4234篇 |
2004年 | 3229篇 |
2003年 | 2946篇 |
2002年 | 2115篇 |
2001年 | 1542篇 |
2000年 | 1740篇 |
1999年 | 1759篇 |
1998年 | 1562篇 |
1997年 | 1292篇 |
1996年 | 1186篇 |
1995年 | 959篇 |
1994年 | 842篇 |
1993年 | 569篇 |
1992年 | 434篇 |
1991年 | 385篇 |
1990年 | 253篇 |
1989年 | 210篇 |
1988年 | 188篇 |
1987年 | 110篇 |
1986年 | 92篇 |
1985年 | 56篇 |
1968年 | 43篇 |
1967年 | 33篇 |
1966年 | 42篇 |
1965年 | 45篇 |
1959年 | 35篇 |
1958年 | 38篇 |
1957年 | 36篇 |
1956年 | 34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 390 毫秒
81.
入侵检测是保障网络安全的重要手段,针对现有入侵检测系统中告警数量多、协调性差等问题,论文提出了一种具有告警融合与关联功能的告警处理系统模型,该模型冗余告警量少、整体检测能力强,并能进行攻击企图的预测,能有效提高入侵检测的效率,有助于进一步增强网络的健壮性。 相似文献
82.
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
83.
84.
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
85.
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
86.
87.
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
88.
Chloride doped polyaniline conducting polymer films have been prepared in a protic acid medium (HCl) by potentiodynamic method
in an electrochemical cell and studied by cyclic voltammetry and FTIR techniques. The FTIR spectra confirmed Cl- ion doping in the polymers. The polymerization rate was found to increase with increasing concentration of aniline monomer.
But the films obtained at high monomer concentration were rough having a nonuniform flaky polyaniline distribution. Results
showed that the polymerization rate did not increase beyond a critical HCl concentration. Cyclic voltammetry suggested that,
the oxidation-reduction current increased with an increase in scan rate and that the undoped polyaniline films were not hygroscopic
whereas chloride doped polyaniline films were found to be highly hygroscopic. 相似文献
89.
90.
西气东输放空系统的设计与研究 总被引:1,自引:0,他引:1
论述了石油天然气行业中的放空系统工作原理,研究了西气东输采用的放空点火系统特点,讨论了放空立管的计算模型,提出了比较符合实际情况的计算模型,指出在桅杆结构的计算分析中,应该考虑钢丝绳的弹性支撑作用。钢丝绳的弹性支撑作用对结构的周期计算、风荷载导算、地震作用的计算都有较大的影响。 相似文献