全文获取类型
收费全文 | 239935篇 |
免费 | 25299篇 |
国内免费 | 15519篇 |
专业分类
电工技术 | 17284篇 |
技术理论 | 5篇 |
综合类 | 26552篇 |
化学工业 | 25050篇 |
金属工艺 | 21495篇 |
机械仪表 | 23394篇 |
建筑科学 | 39288篇 |
矿业工程 | 11656篇 |
能源动力 | 10434篇 |
轻工业 | 5395篇 |
水利工程 | 11362篇 |
石油天然气 | 10336篇 |
武器工业 | 5026篇 |
无线电 | 12799篇 |
一般工业技术 | 30909篇 |
冶金工业 | 8144篇 |
原子能技术 | 2875篇 |
自动化技术 | 18749篇 |
出版年
2024年 | 664篇 |
2023年 | 2947篇 |
2022年 | 5789篇 |
2021年 | 6951篇 |
2020年 | 7322篇 |
2019年 | 5915篇 |
2018年 | 5902篇 |
2017年 | 7671篇 |
2016年 | 8815篇 |
2015年 | 9541篇 |
2014年 | 15341篇 |
2013年 | 14408篇 |
2012年 | 18554篇 |
2011年 | 19863篇 |
2010年 | 14895篇 |
2009年 | 15463篇 |
2008年 | 13854篇 |
2007年 | 17494篇 |
2006年 | 15499篇 |
2005年 | 12791篇 |
2004年 | 10604篇 |
2003年 | 8856篇 |
2002年 | 7319篇 |
2001年 | 6249篇 |
2000年 | 5368篇 |
1999年 | 4423篇 |
1998年 | 3498篇 |
1997年 | 3026篇 |
1996年 | 2399篇 |
1995年 | 2138篇 |
1994年 | 1703篇 |
1993年 | 1251篇 |
1992年 | 1022篇 |
1991年 | 734篇 |
1990年 | 645篇 |
1989年 | 501篇 |
1988年 | 347篇 |
1987年 | 199篇 |
1986年 | 145篇 |
1985年 | 99篇 |
1984年 | 99篇 |
1983年 | 62篇 |
1982年 | 79篇 |
1981年 | 31篇 |
1980年 | 61篇 |
1979年 | 67篇 |
1978年 | 14篇 |
1977年 | 17篇 |
1959年 | 43篇 |
1951年 | 37篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
This paper presents a stochastic performance modelling approach that can be used to optimise design and operational reliability of complex chemical engineering processes. The framework can be applied to processes comprising multiple units, including the cases where closed form process performance functions are unavailable or difficult to derive from first principles, which is often the case in practice. An interface that facilitates automated two-way communication between Matlab® and process simulation environment is used to generate large process responses. The resulting constrained optimisation problem is solved using both Monte Carlo Simulation (MCS) and First Order Reliability Method (FORM); providing a wide range of stochastic process performance measures. Adding such capabilities to traditional deterministic process simulators provides a more informed basis for selecting optimum design factors; giving a simple way of enhancing overall process reliability and cost-efficiency. Two case study systems are considered to highlight the applicability and benefits of the approach. 相似文献
72.
This paper introduces the potential feasibility that ELID (electrolytic in-process dressing) grinding replaces superfinishing in bearing manufacturing, but ELID grinding will bring new challenges. Different regions present distinguish surface profile due to the non-uniform contact in ELID groove grinding. However, few reports explaining the non-uniform contact are available. This article explores the mechanisms of the non-uniform contact during ELID groove grinding. Experiments on the non-uniform contact between bearing raceway and grinding wheel have been carried out under different conditions. The results show that non-uniform contact exists in ELID groove grinding process and it exerts influence on the profile of the raceway surface. Non-uniform contact influences the Rsk and Rku value all the time, but it influences the Ra value occasionally. Improvement strategies of eliminating the non-uniform contact are also discussed based on the experimental study. 相似文献
73.
74.
氢工质在新能源与动力、航天推进、化工材料等领域有着广泛应用。通过开展高温氢工质热力学与输运性质研究,建立了原子态氢、分子态氢、热解平衡态氢的热物理性质计算模型,开发了热物性计算程序Prop_H_H2,适用范围为温度100~3 500 K、压力104~5×107 Pa 。验证表明,Prop_H_H2在适用范围内计算氢工质的物性参数合理可靠,在温度200~3 000 K、压力104~107 Pa范围内,程序预测值更加准确,相对偏差在±5%左右。本研究可为氢工质相关的航天推进、应用物理学、能源动力等行业的科研和应用提供支持借鉴。 相似文献
75.
76.
Izyan Najwa Mohd Norsham Siti Nor Atika Baharin Muggundha Raoov Syed Shahabuddin Jaroon Jakmunee Kavirajaa Pandian Sambasevam 《Polymer Engineering and Science》2020,60(12):3170-3182
A simple, cost-effective, and novel chemical sensor for ammonia (NH3) gas detection was developed from polyaniline (PANI)/quail eggshell (QES) composites. QES is a natural waste enriched in calcium carbonate. In this work, pure PANI was synthesized from chemical oxidation method and PANI/QES composites were prepared from physical mixing of QES with the synthesized PANI at different mass ratio. A series of complementary techniques including Fourier transform infrared and ultraviolet-visible spectrometers, scanning electron microscope with energy dispersive detection coupled with mapping, thermogravimetric analysis, and X-ray diffractometer were used to characterize the physicochemical and textural properties of the biocomposites. From the results, PANI/QES composite with a mass ratio of 1 exhibited the lowest NH3 detection limit of 5.24 ppm with a linear correlation coefficient (R2) of close to unity (0.9932) between the signal and NH3 gas concentration. As a whole, the PANI/QES biocomposites synthesized from this work exhibited excellent selectivity toward NH3 gas even in the presence of other gas impurities, such as acetone, ethanol, and hexane. For the sensor reusability, the PANI/QES biocomposites can be reused in the application of NH3 gas detection for at least 4 cycles. 相似文献
77.
《Journal of the European Ceramic Society》2020,40(13):4403-4418
Crack initiation and propagation in three braided SiC/SiC composite tubes with different braiding angles are investigated by in situ tensile tests with synchrotron micro-computed tomography. Crack networks are precisely detected after an image subtraction procedure based on Digital Volume Correlation. FFT based simulations are performed on the full-resolution 3D images to assess elastic stress/strain fields. Quantitative measurements of the crack geometries are performed using a novel method based on grey levels. The results show that braiding angle has no obvious effect on the location of crack onsets (initiation always occurs at tow interfaces), whereas it significantly affects the paths of crack propagation. This work provides an explicit demonstration of the crack propagation scenarios with respect to the mesoscopic fibre architectures. 相似文献
78.
79.
Coupled large eddy simulation and the discrete element method are applied to study turbulent particle–laden flows, including particle dispersion and agglomeration, in a channel. The particle–particle interaction model is based on the Hertz–Mindlin approach with Johnson–Kendall–Roberts cohesion to allow the simulation of van der Waals forces in a dry air flow. The influence of different particle surface energies, and the impact of fluid turbulence, on agglomeration behaviour are investigated. The agglomeration rate is found to be strongly influenced by the particle surface energy, with a positive relationship observed between the two. Particle agglomeration is found to be enhanced in two separate regions within the channel. First, in the near-wall region due to the high particle concentration there driven by turbophoresis, and secondly in the buffer region where the high turbulence intensity enhances particle–particle interactions. 相似文献
80.