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101.
Ralph Schneider Wolfgang Marquardt 《Chemical engineering science》2002,57(10):1763-1792
Information technology has been becoming increasingly important in all areas of engineering during the last few years. Much of the progress achieved in chemical engineering would not have been possible without the enabling methods and tools provided by information technology. This trend will continue in the future but most likely with a considerably wider scope. While individual software tools and services have been in focus until recently, their integration into engineering work processes is an emerging and challenging area of research and development. This contribution attempts to highlight state of the art and future trends in supporting the activities during the life cycle of a chemical process by means of information technology. Emphasis will be largely on the process and plant design process rather than on procurement, manufacturing, and distribution of materials in the supply chain. 相似文献
102.
103.
概述了反射式光纤传感器的发展。讨论了这类光纤传感器理论分析中所采用的纤端出射光场光强径向均匀分布的假设。给出了纤端出射场的光通量分布函数,并以全光路补偿反射式光纤探头为例,建立了补偿机理的理论分析方法,给出了传感特性调制函数的解析表达式。最后,简要分析了这类光纤传感器的温度稳定性问题。 相似文献
104.
Impacts of spectral band difference effects on radiometric cross-calibration between satellite sensors in the solar-reflective spectral domain 总被引:2,自引:0,他引:2
In order for quantitative applications to make full use of the ever-increasing number of Earth observation satellite systems, data from the various imaging sensors involved must be on a consistent radiometric scale. This paper reports on an investigation of radiometric calibration errors due to differences in spectral response functions between satellite sensors when attempting cross-calibration based on near-simultaneous imaging of common ground targets in analogous spectral bands, a commonly used post-launch calibration methodology. Twenty Earth observation imaging sensors (including coarser and higher spatial resolution sensors) were considered, using the Landsat solar reflective spectral domain as a framework. Scene content was simulated using spectra for four ground target types (Railroad Valley Playa, snow, sand and rangeland), together with various combinations of atmospheric states and illumination geometries. Results were obtained as a function of ground target type, satellite sensor comparison, spectral region, and scene content. Overall, if spectral band difference effects (SBDEs) are not taken into account, the Railroad Valley Playa site is a “good” ground target for cross calibration between most but not all satellite sensors in most but not all spectral regions investigated. “Good” is defined as SBDEs within ± 3%. The other three ground target types considered (snow, sand and rangeland) proved to be more sensitive to uncorrected SBDEs than the RVPN site overall. The spectral characteristics of the scene content (solar irradiance, surface reflectance and atmosphere) are examined in detail to clarify why spectral difference effects arise and why they can be significant when comparing different imaging sensor systems. Atmospheric gas absorption features are identified as being the main source of spectral variability in most spectral regions. The paper concludes with recommendations on spectral data and tools that would facilitate cross-calibration between multiple satellite sensors. 相似文献
105.
During the second part of the 1990s the Nordic (Denmark, Finland, Norway and Sweden) countries have created a unique multinational market for electricity. This paper aims to analyse the degree of integration of the different national markets that constitute the Nordic electricity market. In particular the Norwegian and Swedish wholesale and retail electricity markets are analysed. The results suggest that the wholesale markets are well integrated. Thus prices differ significantly only during periods with unusually high or low supply of hydropower. However, the retail markets are not integrated to the same degree. Thus retail prices and trade margins differ significantly. Differences in the national electricity market legislation seem to be a key factor behind these differences. 相似文献
106.
107.
资源与目标一体化评价技术及其勘探意义 总被引:1,自引:0,他引:1
资源与目标一体化评价技术,主要对盆地、含油气系统、区带、圈闭以及勘探开发区块进行资源潜力评价和空间分布预测,并通过地质风险、工程、经济等方面的综合评价和决策分析,对有利目标进行评价和优选,对于提高勘探效率,降低勘探风险,实现油气资源动态管理具有重要意义。通过对该技术在国外研究和应用现状及发展趋势的分析,结合当前我国油气资源评价和勘探目标评价现状,指出了我国油气勘探评价存在着数据库建设滞后、各种评价参数积累不够、参数选择随意性大等问题,认为我国石油公司应坚持“以自主开发为主,适度引进”的思路,发展具有自主知识产权的核心勘探评价技术,以提高油气勘探水平,增强国际竞争力。 相似文献
108.
109.
掺镉纳米SnO2的热稳定性,电导及气敏性能 总被引:3,自引:0,他引:3
本文研究了CdO掺杂对纳米SnO2粉料的热稳定性,电导及气敏特性的影响。结果表明,以非晶状态均匀分散在SnO2颗粒表面的CdO能阻止SnO2之间的相互扩散,提高了纳米SnO2的热稳定性;固溶于SnO2昌粒中的CdO量(Cd/Sn〈0.05)很小,但对元件的电导影响显著;纳米级的晶粒尺寸(〈6nm)及CdO的掺杂大大改善了SnO2的气敏特性。 相似文献
110.
This paper deals with the development of computational schemes for the dynamic analysis of flexible, nonlinear multi-body systems. The focus of the investigation is on the derivation of unconditionally stable time integration schemes for these types of problem. At first, schemes based on Galerkin and time discontinuous Galerkin approximations applied to the equations of motion written in the symmetric hyperbolic form are proposed. Though useful, these schemes require casting the equations of motion in the symmetric hyperbolic form, which is not always possible for multi-body applications. Next, unconditionally stable schemes are proposed that do not rely on the symmetric hyperbolic form. Both energy preserving and energy decaying schemes are derived that both provide unconditionally stable schemes for nonlinear multi-body systems. The formulation of beam and flexible joint elements, as well as of the kinematic constraints associated with universal and revolute joints. An automated time step selection procedure is also developed based on an energy related error measure that provides both local and global error levels. Several examples of simulation of realistic multi-body systems are presented which illustrate the efficiency and accuracy of the proposed schemes, and demonstrate the need for unconditional stability and high frequency numerical dissipation. 相似文献