全文获取类型
收费全文 | 115061篇 |
免费 | 13209篇 |
国内免费 | 5134篇 |
专业分类
电工技术 | 12000篇 |
技术理论 | 7篇 |
综合类 | 11911篇 |
化学工业 | 10966篇 |
金属工艺 | 8986篇 |
机械仪表 | 11418篇 |
建筑科学 | 7838篇 |
矿业工程 | 5980篇 |
能源动力 | 7041篇 |
轻工业 | 1862篇 |
水利工程 | 4368篇 |
石油天然气 | 5904篇 |
武器工业 | 3392篇 |
无线电 | 10101篇 |
一般工业技术 | 11170篇 |
冶金工业 | 3024篇 |
原子能技术 | 1742篇 |
自动化技术 | 15694篇 |
出版年
2025年 | 1098篇 |
2024年 | 2993篇 |
2023年 | 2912篇 |
2022年 | 3726篇 |
2021年 | 4211篇 |
2020年 | 4526篇 |
2019年 | 3712篇 |
2018年 | 3435篇 |
2017年 | 4207篇 |
2016年 | 4906篇 |
2015年 | 5179篇 |
2014年 | 7312篇 |
2013年 | 7198篇 |
2012年 | 8646篇 |
2011年 | 9129篇 |
2010年 | 6654篇 |
2009年 | 6578篇 |
2008年 | 6247篇 |
2007年 | 7535篇 |
2006年 | 6413篇 |
2005年 | 5187篇 |
2004年 | 4349篇 |
2003年 | 3355篇 |
2002年 | 2698篇 |
2001年 | 2242篇 |
2000年 | 1770篇 |
1999年 | 1444篇 |
1998年 | 1116篇 |
1997年 | 919篇 |
1996年 | 817篇 |
1995年 | 637篇 |
1994年 | 538篇 |
1993年 | 364篇 |
1992年 | 281篇 |
1991年 | 243篇 |
1990年 | 184篇 |
1989年 | 157篇 |
1988年 | 103篇 |
1987年 | 52篇 |
1986年 | 66篇 |
1985年 | 32篇 |
1984年 | 33篇 |
1983年 | 27篇 |
1982年 | 27篇 |
1981年 | 15篇 |
1980年 | 25篇 |
1979年 | 19篇 |
1977年 | 7篇 |
1959年 | 22篇 |
1951年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
本文用计算机数字模拟方法研究了电活性分子多层Z型L-B膜修饰电极的循环伏安行为。计算了电极与修饰L-B膜分子第一层之间的电荷转移速度常数K_o,L-B膜分子层间的电荷转移速度常数k_i;对峰电位差△E_p及阳极峰面积Q的影响,以及在不同条件下各层分子的氧化态分数随扫描时间的变化。为研究和设计电活性分子修饰电极的实际体系提供了大量数据和信息。 相似文献
2.
In order to cumpare the peformance of different supply diffuers of ventilation air, the airflow passern, temperature stratifiation and contaminant dispersion in a furnitured office ventilated by three kinds of air diffuer were numerically investigated. The air diffuers studied in this paper are a quarter-cylinder displacement diffuer on the floor and mixing diffuers (linear and vortex diffuers) on the ceiling. The heat sources in the of-fice are considered to be 50% convective and 50% radiative. The k-? two-equatwn model of turbulence is employed to predict the turbulent diffusion. The results show that the displacement diffuser provides a rather uniform flow field with low velocify in most areas, and the vertical temperature difference from floor to ceiling is as high as 6 K. With the linear diffuser, the air velociry is high, and the temperature is uniform both horizontally and vertically. The air velocity generated by the vortex diffuser is moderate. The distributions of the temperature and the contaminant are rather uniform. 相似文献
3.
M. J. O'sullivan 《国际能源研究杂志》1985,9(3):319-332
This paper is intended to be a state of the art review of geothermal reservoir simulation. Its recent application to the modelling of real geothermal reservoirs is described and put in the context of an emerging general approach to reservoir modelling. The use of computer simulation for geothermal well test analysis is described. One of the main recent uses of reservoir simulators has been for conducting numerical experiments aimed at improving the understanding of geothermal reservoir physics. Such studies on fractured reservoirs, the thermal structure of reservoirs and the effects of non-condensable gases and dissolved salts are outlined. 相似文献
4.
Shunsuke Ohashi 《Electrical Engineering in Japan》2005,150(1):71-77
Magnetic bearing using pinning force of a permanent magnet and a high‐temperature superconductor has been developed. Additional permanent magnet is introduced to increase the levitation force of the magnetic bearing. In this hybrid magnetic bearing system, levitation force is mainly given by the repulsive force of the permanent magnets, and stability for the lateral direction is given by pinning force of the superconductor. The experimental device is developed. A ring‐type superconductor and a bulk one are examined. Levitation characteristics of the hybrid magnetic bearing are measured. The bulk superconductor shows better characteristics of both levitation and lateral stability than the ring one. Levitation force of the hybrid system becomes about twice as large as that of the nonhybrid one. Although, the repulsive force of the permanent magnet decreases the lateral stability of the system, its influence becomes small by choosing an adequate position of the permanent magnets and the superconductor. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(1): 71–77, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10350 相似文献
5.
Kotaro Matsuuchi Tadashi Fukami Nobuyuki Naoe Ryoichi Hanaoka Shinzo Takata Toshio Miyamoto 《Electrical Engineering in Japan》2005,150(2):43-49
This paper presents a method of predicting the steady‐state performance of a new hybrid‐excitation synchronous machine (HESM) theoretically. The field pole of this HESM is axially divided into two parts; one is an excitation part and the other a permanent‐magnet (PM) part. A nonlinear equivalent circuit, which can include the saliency of the rotor and the magnetic saturation due to the iron core, is derived. Based on this equivalent circuit, the steady‐state performance of the HESM is calculated, and the results are confirmed through experiments. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(2): 43–49, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20033 相似文献
6.
Hitoshi Kurokawa Taku Nakayama Yasunori Kobayashi Ken Suzuki Mutsumi Takahashi Seiichi Takami Momoji Kubo Naotsugu Itoh Parasuraman Selvam Akira Miyamoto 《Catalysis Today》2003,82(1-4):233-240
A modified Monte Carlo (MC) simulation was performed to investigate the hydrogen absorption behavior in Pd and Pd–Ag alloys of the composition PdxAg1−x (x=0.7–0.8) under H2 pressure (0.1 MPa) at different temperatures. The present method employed can consider the dissociative adsorption of hydrogen molecule and the subsequent absorption of hydrogen atom by formalizing the relationship between the pressure of hydrogen molecule and hydrogen atom. The potential parameters were determined to reproduce the solution enthalpy of hydrogen in pure metals. The results are in good agreement with experimental findings as well as previous theoretical studies. We confirmed that our method is useful to simulate the absorption of hydrogen in metals and alloys. 相似文献
7.
《Drying Technology》2007,25(11):1803-1808
Malting is a very intensive, energy-consuming process and, from the point of view of energy, green malt drying is one of the most important operations. Double-deck kiln drying, a variant of single-deck kiln drying, is the most commonly used process, but it is usually manually controlled under empirical control actions. These are the reasons why a research project was carried out based on the computer modeling of these process operations including a software tool named CIMFOOD. A knowledge-based system (KBS) allowing the entire processing-plant dynamic behavior simulation and scheduling concerning thermal energy requirements was developed. 相似文献
8.
This article presents a two-dimensional transient model for gas-solids flow and heat transfer through pipes using the coupled Computational Fluid Dynamics and Discrete Element Method approach. Numerical simulations have been conducted to examine the modification of fluid thermal structure due to the presence of particles in a pneumatic transport pipeline. Modeled results have demonstrated the key role of transversal motion of rebounding particles in the pipe cross section in altering fluid temperature. Further implementation of this modeling technique in air-drying processes is discussed and possible experimental methods for the measurement of in situ particle and fluid motion and temperature profile are cited. 相似文献
9.
本文利用简便的滴定过程模型,确立了微机模拟处理实验数据,方便、准确地求解络合滴定等当点的方法。设计了最佳实验条件模拟估计程序。该法测定Zn~(2+),Pb~(2+),Cu~(2+),Fe~(3+)结果的相对误差Δ<1%。pH=6-7时,测定Ca~(2+)的相对误差为-1.61%;σ<0.001mmol,(N=5)。 相似文献
10.
Quenching with gases rather than oil or other liquid media has the advantages of reducing the risks concerning health and environment, while simultaneously homogenizing the quenching results and minimizing distortion due to a wide range of possible process parameter variations and the pure convective heat transfer. In this contribution, a coupled solution for increasing homogenization of quenching results within high pressure gas quenching will be presented. In the first stage, an experimental test facility was set up for flow investigations and in the second stage a numerical simulation model was generated. The numerical and experimental results of the flow through the chamber were compared for several boundary conditions. Finally, after complete verification of the simulation, the model may be used to assist in parameter variation for optimization of homogeneous high pressure gas quenching. 相似文献