全文获取类型
收费全文 | 267363篇 |
免费 | 20230篇 |
国内免费 | 10470篇 |
专业分类
电工技术 | 14838篇 |
技术理论 | 24篇 |
综合类 | 15457篇 |
化学工业 | 45711篇 |
金属工艺 | 13731篇 |
机械仪表 | 15555篇 |
建筑科学 | 21364篇 |
矿业工程 | 6629篇 |
能源动力 | 7555篇 |
轻工业 | 17496篇 |
水利工程 | 4406篇 |
石油天然气 | 14367篇 |
武器工业 | 1828篇 |
无线电 | 32635篇 |
一般工业技术 | 33863篇 |
冶金工业 | 14079篇 |
原子能技术 | 2751篇 |
自动化技术 | 35774篇 |
出版年
2024年 | 1146篇 |
2023年 | 4192篇 |
2022年 | 7619篇 |
2021年 | 10399篇 |
2020年 | 7734篇 |
2019年 | 6511篇 |
2018年 | 7169篇 |
2017年 | 8045篇 |
2016年 | 7469篇 |
2015年 | 9678篇 |
2014年 | 12466篇 |
2013年 | 15758篇 |
2012年 | 16050篇 |
2011年 | 18095篇 |
2010年 | 15120篇 |
2009年 | 14827篇 |
2008年 | 14191篇 |
2007年 | 13560篇 |
2006年 | 13834篇 |
2005年 | 12273篇 |
2004年 | 8490篇 |
2003年 | 7489篇 |
2002年 | 6840篇 |
2001年 | 6149篇 |
2000年 | 6432篇 |
1999年 | 7471篇 |
1998年 | 6854篇 |
1997年 | 5638篇 |
1996年 | 5237篇 |
1995年 | 4366篇 |
1994年 | 3707篇 |
1993年 | 2828篇 |
1992年 | 2208篇 |
1991年 | 1636篇 |
1990年 | 1323篇 |
1989年 | 1155篇 |
1988年 | 886篇 |
1987年 | 636篇 |
1986年 | 493篇 |
1985年 | 409篇 |
1984年 | 271篇 |
1983年 | 235篇 |
1982年 | 206篇 |
1981年 | 176篇 |
1980年 | 163篇 |
1979年 | 109篇 |
1978年 | 69篇 |
1977年 | 72篇 |
1976年 | 89篇 |
1973年 | 46篇 |
排序方式: 共有10000条查询结果,搜索用时 32 毫秒
11.
陈国龙 《计算机辅助设计与图形学学报》1994,6(2):136-142
本文介绍了一种在微机上实现的印制板自动布线方法──多级线探索法及其编程方法。这种方法是基于完备布线算法的概念,通过分析李氏算法和传统线探索法的不足之处而得到的。虽然它也是一种线探索法,但有较传统线探索法更强的探索能力,不需要结合李氏算法而能单独完成布线任务,是一种较理想的算法,通过实验获得了较为满意的效果。 相似文献
12.
Fuzzy controller design by using neural network techniques 总被引:2,自引:0,他引:2
Cheng-Liang Chen Wen-Chih Chen 《Fuzzy Systems, IEEE Transactions on》1994,2(3):235-244
This paper investigates the relationship between the piecewise linear fuzzy controller (PLFC), in which the membership functions for fuzzy variables and the associated inference rules are all in piecewise linear forms, and a Gaussian potential function network based controller (GPFNC), in which the network output is a weighted summation of hidden responses from a series of Gaussian potential function units (GPFU's). Systematic procedures are proposed for transformation from a PLFC to its GPFNC counterpart, and vice versa. Based on these transformation principles, a series of systematic and feasible steps is presented for the design of an optimized PLFC (PLFC*) by using neural network techniques. In the design procedures, the simplified PLFC is used as the initial controller structure, then a GPFNC, which gives the approximate control response to the initially given PLFC, is found for further optimization. A neutralization process is used to demonstrate the feasibility and the potential applicability of these intelligent controllers on the regulation of highly nonlinear chemical processes 相似文献
13.
实验研究了以工业硫酸亚铁及废硫酸为原料,分别采用NaClo_3、KClO_3、H_2O_2及(o_2+NaNO_2)为氧化剂成聚硫酸铁的条件。在以(O_2+NaNO_2)为氧化剂的合成过程中,发现添加微量助催化剂(型号为HG-1、HG-2和HG-3),对提高合成速度及反应过程的稳定性具有重大作用。 相似文献
14.
Temperature control offers benefits in land‐based marine aquaculture: stock growth rates may be enhanced by heating in winter; mortality rates in summer may be reduced by cooling. However, if the plant is not well designed, temperature control may create very large energy demands. This paper describes the application of temperature control in abalone aquaculture in New Zealand, with a focus on energy considerations in plant design. An abalone farm using a semi‐closed water conditioning system is used as a case study for which an energy model, based on a heat pump system, is developed. The model is used to determine the impact of plant design and tank conditions on the economics of the operation. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
15.
16.
17.
Tsu-Hua Ai Jiann-Fuh Chen Tsorng-Juu Liang 《Industrial Electronics, IEEE Transactions on》2002,49(3):595-597
To overcome the problem of unequal switching loss in power switches, in conventional hybrid pulse width modulation (HPWM) full-bridge inverters, a random switching method for HPWM full-bridge inverters is proposed. The proposed method equalizes switching losses of the four switches, while also providing good output performance 相似文献
18.
Some methods determine the non-indolyl glucosinolates content in rapeseed as their hydrolysates: the isothiocyanates and the
oxazolidinethiones. These methods in their present form underestimate the amount of the glucosinolates content. In this investigation,
a modified method was developed to give a better quantitative estimate, indicating a glucosinolate level five times that obtained
by a typical existing method. 相似文献
19.
A novel series of temperature‐sensitive poly[(N‐isopropylacrylamide)‐co‐(ethyl methacrylate)] (p(NIPAM‐co‐EMA)) microgels was prepared by the surfactant‐free radical polymerization of N‐isopropylacrylamide (NIPAM) with ethyl methacrylate (EMA). The shape, size dispersity and volume‐phase transition behavior of the microgels were investigated by transmission electron microscopy (TEM), ultraviolet–visible (UV–Vis) spectroscopy, dynamic light scattering (DLS) and differential scanning calorimetry (DSC). The transmission electron micrographs and DLS results showed that microgels with narrow distributions were prepared. It was shown from UV–Vis, DLS and DSC measurements that the volume‐phase transition temperature (VPTT) of the p(NIPAM‐co‐EMA) microgels decreased with increasing incorporation of EMA, but the temperature‐sensitivity was impaired when more EMA was incorporated, causing the volume‐phase transition of the microgels to become more continuous. It is noteworthy that incorporation of moderate amounts of EMA could not only lower the VPTT but also enhance the temperature‐sensitivity of the microgels. The reason for this phenomenon could be attributed to changes in the complicated interactions between the various molecules. Copyright © 2004 Society of Chemical Industry 相似文献
20.
Poly[2‐methoxy‐5‐(2′‐ethyl‐hexyloxy)‐para‐phenylene vinylene] (MEH‐PPV)/silica nanoparticle hybrid films were prepared and characterised. Three kinds of materials were compared: parent MEH‐PPV, MEH‐PPV/silica (hybrid A films), and MEH‐PPV/coupling agent MSMA/silica (hybrid B films), in which MSMA is 3‐(trimethoxysilyl) propyl methacrylate. It was found that the hybrid B films could significantly prevent macrophase separation, as evidenced by scanning electron and fluorescence microscopy. Furthermore, the thermal characteristics of the hybrid films were largely improved in comparison with the parent MEH‐PPV. The UV‐visible absorption spectra suggested that the incorporation of MSMA‐modified silica into MEH‐PPV could confine the polymer chain between nanoparticles and thus increase the conjugation length. The photoluminescence (PL) studies also indicated enhancement of the PL intensity and quantum efficiency by incorporating just 2 wt% of MSMA‐modified silica into MEH‐PPV. However, hybrid A films did not show such enhancement of optoelectronic properties as the hybrid B films. The present study suggests the importance of the interface between the luminescent organic polymers and the inorganic silica on morphology and optoelectronic properties. Copyright © 2004 Society of Chemical Industry 相似文献