全文获取类型
收费全文 | 111701篇 |
免费 | 8127篇 |
国内免费 | 4190篇 |
专业分类
电工技术 | 5842篇 |
技术理论 | 11篇 |
综合类 | 6582篇 |
化学工业 | 18940篇 |
金属工艺 | 5799篇 |
机械仪表 | 6666篇 |
建筑科学 | 8623篇 |
矿业工程 | 3075篇 |
能源动力 | 3095篇 |
轻工业 | 6620篇 |
水利工程 | 1710篇 |
石油天然气 | 6210篇 |
武器工业 | 691篇 |
无线电 | 13953篇 |
一般工业技术 | 14232篇 |
冶金工业 | 5893篇 |
原子能技术 | 1237篇 |
自动化技术 | 14839篇 |
出版年
2024年 | 431篇 |
2023年 | 1749篇 |
2022年 | 2880篇 |
2021年 | 3984篇 |
2020年 | 3043篇 |
2019年 | 2586篇 |
2018年 | 2982篇 |
2017年 | 3368篇 |
2016年 | 2930篇 |
2015年 | 3852篇 |
2014年 | 4882篇 |
2013年 | 6247篇 |
2012年 | 6551篇 |
2011年 | 7172篇 |
2010年 | 6241篇 |
2009年 | 6158篇 |
2008年 | 6156篇 |
2007年 | 5743篇 |
2006年 | 6034篇 |
2005年 | 5407篇 |
2004年 | 3690篇 |
2003年 | 3194篇 |
2002年 | 2847篇 |
2001年 | 2753篇 |
2000年 | 2869篇 |
1999年 | 3380篇 |
1998年 | 2911篇 |
1997年 | 2547篇 |
1996年 | 2286篇 |
1995年 | 1921篇 |
1994年 | 1552篇 |
1993年 | 1220篇 |
1992年 | 964篇 |
1991年 | 739篇 |
1990年 | 600篇 |
1989年 | 501篇 |
1988年 | 390篇 |
1987年 | 294篇 |
1986年 | 206篇 |
1985年 | 176篇 |
1984年 | 108篇 |
1983年 | 81篇 |
1982年 | 87篇 |
1981年 | 57篇 |
1980年 | 46篇 |
1979年 | 32篇 |
1978年 | 25篇 |
1977年 | 25篇 |
1976年 | 40篇 |
1973年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
H Wu 《Canadian Metallurgical Quarterly》1996,14(6):328-30, 365-8
A universal EPR simulation program has been created by the author, which is based on the following spin Hamiltonian equation: [equation: see text] where D and E are the axial and rhombic zero-field splitting parameters, respectively. The program can be used for simulation of EPR spectra with half-integer electronic spin (S = n/2, n = 3, 5, 7, 9) systems. In this article, the integer spin (S = n/2, n = 2, 4) systems are also considered. The EPR simulation results show that when D > frequency, no EPR signal can be seen from EPR simulation; when D approximately frequency, whichever X/Q/W-band is used, the EPR signal can be seen on the basis of the simulated EPR results presented. 相似文献
33.
It is common knowledge today that application of sound manufacturing concepts and techniques will only provide cost-effective, long-term return when manufacturing functions are totally integrated with the operators, maintenance engineers and other associated personnel. This paper presents a human-centred methodology and its associated knowledge-based tool, to utilize equipment failure information for the purpose of machine down-time minimization. Based upon a structured and rigorous assessment of each breakdown, and combined with total employee participation, continuous improvement of maintenance function and operational effectiveness of equipment can be made a reality. 相似文献
34.
就5500m^3/min高炉鼓风机动,静叶片损坏事故发生的经过以及有关资料,从几个方面详细分析了事故发生的原因。 相似文献
35.
Wu Ting M. Badaye T. Morishita N. Koshizuka S. Tanaka 《Journal of Superconductivity》1996,9(6):637-645
Recently, superconducting Nd1Ba2Cu3Oy (Ndl23) thin films with high superconducting transition temperature (T
c) have been successfully fabricated at our institute employing the standard laser ablation method. In this paper, we report the results of surface characterization of the Nd123 thin films using an ultrahigh vacuum scanning tunneling microscope/spectroscopy (UHV-STM/STS) and an atomic force microscope (AFM) system operated in air. Clear spiral pattern is observed on the surfaces of Nd123 thin films by STM and AFM, suggesting that films are formed by two-dimensional island growth mode. Contour plots of the spirals show that the step heights of the spirals are not always the integer or half-integer number of thec-axis parameter of the structure. This implies that the surface natural termination layer of the films may not be unique. This result is supported byI-V STS measurements. The surface morphology of the Nd123 thin films is compared with that of thec-axis-oriented Y1Ba2Cu3Sy thin films. Surface atomic images of the as-prepared Nd123 thin films are obtained employing both STM and AFM. STS measurements show that most of the surfaces are semiconductive. The results of STS measurements together with the fact that we are able to see the surface atomic images using scanning probe microscopes suggest that exposure to air does not cause serious degradation to the as-prepared surfaces of Nd123 thin films. 相似文献
36.
灾难备份的概念所谓“灾难备份”,是指利用技术、管理手段以及相关资源,确保已有的关键数据和关键业务在灾难发生后,在确定的时间内可以恢复和继续运营的过程。灾难备份建设是一项复杂的系统工程,涉及到灾难备份中心选点、灾难备份中心建设,机房建设、基础设施建设等,同时还涉及到灾难备份系统建设、专业运营队伍建设、灾难备份中心运营管理体制建设和灾难备份中心运营管理等工作。因此,建立灾难备份不仅需要投入大量人力、物力和财力,还需要考虑灾难备份系统实施所面临的技术难度和经验不足所带来的风险,以及长期运营管理方面的资金投入。… 相似文献
37.
The famous Antosik-Mikusinski convergent theorem on the Abel topological groups has very extensive applications in measure theory, summation theory and other analysis fields. In this paper, we establish the theorem on a class of effect algebras equipped with the ideal topology. This paper shows also that the ideal topology of effect algebras is a useful topology in studying the quantum logic the- ory. 相似文献
38.
39.
This study addresses the rolling and lifting probabilities for sediment entrainment by incorporating the probabilistic features of the turbulent fluctuation and bed grain geometry. The lognormally distributed instantaneous velocity and uniformly distributed initial grain position, along with a relation between lift coefficient and particle Reynolds number, are used to extend the theoretical formulation of the entrainment probabilities in smooth-bed flows. The two threshold conditions identified herein enable us to precisely define the probabilities of entrainment in the rolling and lifting modes. The results obtained in this study coincide well with the published data. The lifting probability increases monotonously with the dimensionless shear stress θ, which is consistent with the earlier results yet displays improved agreement with the experimental data. The maximum value of rolling probability, with a magnitude of 0.25, occurs at θ ≈ 0.15. For θ<0.05 (or θ>0.6), the rolling (or lifting) probability makes up more than 90% of the total entrainment probability and thus can be used as an approximation to the total probability of entrainment. The proposed rolling and lifting probabilities are further linked to the two separate criteria for incipient motion to explore the critical entrainment probabilities. The results reveal that a consistent probability corresponding to the critical state of sediment entrainment cannot be found. 相似文献
40.
Polyester‐based polyurethane/nano‐silica composites were obtained via in situ polymerization and investigated by Fourier‐transform infrared spectroscopy (FTIR), or FTIR coupled with attenuated total reflectance (FTIR‐ATR), Transmission electron microscopy (TEM), atomic force microscopy (AFM), an Instron testing machine, dynamic mechanical analysis (DMA) and ultraviolet‐visible spectrophotometry (UV‐vis). FTIR analysis showed that in situ polymerization provoked some chemical reactions between polyester molecules and nano‐silica particles. FTIR‐ATR, TEM and AFM analyses showed that both surface and interface contained nano‐silica particles. Instron testing and DMA data showed that introducing nano‐silica particles into polyurethane enhanced the hardness, glass temperature and adhesion strength of polyurethane to the substrate, but also increased the resin viscosity. UV‐vis spectrophotometry showed that nano‐silica obtained by the fumed method did not shield UV radiation in polyurethane films. Copyright © 2003 Society of Chemical Industry 相似文献