全文获取类型
收费全文 | 22791篇 |
免费 | 1856篇 |
国内免费 | 1039篇 |
专业分类
电工技术 | 1183篇 |
技术理论 | 4篇 |
综合类 | 1470篇 |
化学工业 | 4313篇 |
金属工艺 | 1356篇 |
机械仪表 | 1281篇 |
建筑科学 | 1687篇 |
矿业工程 | 598篇 |
能源动力 | 573篇 |
轻工业 | 1530篇 |
水利工程 | 387篇 |
石油天然气 | 1396篇 |
武器工业 | 149篇 |
无线电 | 2527篇 |
一般工业技术 | 2888篇 |
冶金工业 | 1067篇 |
原子能技术 | 222篇 |
自动化技术 | 3055篇 |
出版年
2024年 | 109篇 |
2023年 | 437篇 |
2022年 | 670篇 |
2021年 | 909篇 |
2020年 | 708篇 |
2019年 | 630篇 |
2018年 | 645篇 |
2017年 | 756篇 |
2016年 | 618篇 |
2015年 | 872篇 |
2014年 | 1056篇 |
2013年 | 1304篇 |
2012年 | 1379篇 |
2011年 | 1490篇 |
2010年 | 1367篇 |
2009年 | 1364篇 |
2008年 | 1223篇 |
2007年 | 1195篇 |
2006年 | 1177篇 |
2005年 | 1050篇 |
2004年 | 723篇 |
2003年 | 695篇 |
2002年 | 708篇 |
2001年 | 582篇 |
2000年 | 557篇 |
1999年 | 658篇 |
1998年 | 506篇 |
1997年 | 425篇 |
1996年 | 389篇 |
1995年 | 345篇 |
1994年 | 301篇 |
1993年 | 200篇 |
1992年 | 161篇 |
1991年 | 132篇 |
1990年 | 87篇 |
1989年 | 99篇 |
1988年 | 55篇 |
1987年 | 31篇 |
1986年 | 20篇 |
1985年 | 14篇 |
1984年 | 13篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 8篇 |
1980年 | 5篇 |
1979年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
Aimin Xiang Zhongjie Du Qinghua Zeng Chen Zhang Hangquan Li 《Polymer International》2005,54(10):1366-1370
This paper presents recent efforts on the preparation of flexible polyhedral particles via concentrated emulsion templating polymerization in which the hydrophilic monomer (acrylamide) and hydrophobic monomer (butyl acrylate) are polymerized simultaneously in the continuous and dispersed phase, respectively. Such templating polymerization has been enhanced in our systems owing to the introduction of acrylamide monomer and their higher polymerization rate in continuous phase as compared with butyl acrylate in dispersed phase. Diffusion between the different phases was also inhibited. Furthermore, the stability of the concentrated emulsion and the molecular weight of the produced poly(butyl acrylate) were found to be significantly affected by the amount of redox initiator. The morphology of the particles could be controlled by varying the volume fraction of the dispersed phase and the polyhedral particles were achieved at higher volume fraction. Copyright © 2005 Society of Chemical Industry 相似文献
12.
曾春志 《信息安全与通信保密》2005,(10):38-39
前言随着电信市场竞争越来越激烈,各种电信业务资费呈下降趋势,因此大客户原来主要采用低速专线来组织其内部通信网的方式也发生变化,逐渐采用高速的2M电路或者LAN专线、VPN等IP电路进行组网。目前大客户主要分布在金融、政府、行政、外企、交通等行业,其采用运营商电路来组织其内部通信网络以满足中心网点与各个分支网点、分支机构的语音、数 相似文献
13.
Jianxin Wei Mark R Pickering Michael R Frater John F Arnold John A Boman Wenjun Zeng 《IEEE transactions on image processing》2005,14(8):1033-1042
It is well known that tile-boundary artifacts occur in wavelet-based lossy image coding. However, until now, their cause has not been understood well. In this paper, we show that boundary artifacts are an inescapable consequence of the usual methods used to choose tile size and the type of symmetric extension employed in a wavelet-based image decomposition system. This paper presents a novel method for reducing these tile-boundary artifacts. The method employs odd tile sizes (2N + 1 samples) rather than the conventional even tile sizes (2N samples). It is shown that, for the same bit rate, an image compressed using an odd tile length low-pass first (OTLPF) convention has significantly less boundary artifacts than an image compressed using even tile sizes. The OTLPF convention can also be incorporated into the JPEG 2000 image compression algorithm using extensions defined in Part 2 of this standard. 相似文献
14.
15.
16.
Interfacial hybridization kinetics of oligonucleotides immobilized onto fused silica surfaces 总被引:3,自引:0,他引:3
Jiang Zeng Amer Almadidy James Watterson Ulrich J. Krull 《Sensors and actuators. B, Chemical》2003,90(1-3):68-75
Fused silica optical fibers have been used in an intrinsic mode optical configuration as biosensors for fluorescence based detection of hybridization of nucleic acids. In this work, the kinetics of hybridization of single-stranded oligonucleotides that were covalently immobilized were studied. The probe DNA was dT20, and the target was Fluorescein-labeled non-complementary (dT20) or complementary (dA20) oligonucleotide. Chronofluorimetric monitoring of the adsorption and hybridization processes was used to investigate oligonucleotide films of different density, in different salt concentrations, at temperatures of 25 and 40 °C, with the concentration of the target DNA being 0.005–0.1 μM. Mathematical models based on first- and second-order Langmuir adsorption have been examined to describe both the adsorption and the hybridization processes. Experimental data were processed using the models, and the hybridization kinetics were calculated. Hybridization kinetics on these optical fiber DNA sensors was found to be up to three orders faster than results presented for a number of other experiments using different immobilization chemistries. 相似文献
17.
18.
Longjie Zhou A. Zimmermann Yu-Ping Zeng F. Aldinger 《Journal of Materials Science》2004,39(8):2675-2681
The bipolar electric fatigue behaviour of antiferroelectric ceramics with the composition of Pb0.88Ba0.10La0.02(Zr0.55Sn0.35Ti0.10)O3 was investigated under various cycling fields. The material exhibits a degradation in the maximum field induced strain, a diffuse AFE-FE phase transition and an enhancement in the diffusion character of the FE-AFE phase transition due to electric cycling. Those variations increase with cycle number, indicating a logarithmic fatigue up to 108 cycles. There is no indication for the variations to be recovered, and the symmetry of the negative and positive parts of the strain hysteresis loops still remains. Higher cycling field results in a stronger deterioration of the maximum field induced strain and a larger extent of diffusion in AFE-FE and FE-AFE phase transitions. The normalized maximum strain shows nearly the same scale of degradation when the materials are cycled at various electric fields. After a heat treatment at 500°C for 1 h, the variations in the AFE-FE and FE-AFE phase transition due to cycling disappear, whereas the maximum strain resumes almost to its original value. Electrochemical variations are considered to contribute to the main fatigue mechanism for the material under investigation. 相似文献
19.
An innovative method for modelling biological processes under anaerobic conditions is presented and discussed. The method is based on titrimetric and off-gas measurements. Titrimetric data is recorded as the addition rate of hydroxyl ions or protons that is required to maintain pH in a bioreactor at a constant level. An off-gas analysis arrangement measures, among other things, the transfer rate of carbon dioxide. The integration of these signals results in a continuous signal which is solely related to the biological reactions. When coupled with a mathematical model of the biological reactions, the signal allows a detailed characterisation of these reactions, which would otherwise be difficult to achieve. Two applications of the method to the enhanced biological phosphorus removal processes are presented and discussed to demonstrate the principle and effectiveness of the method. 相似文献
20.
一、概况南平市种猪场位于延平区浆甲村 ,距市区 13km ,地处 316国道旁 ,面临沙溪口库湾边。年存栏猪760 0头 ,其中母猪 60 0头 ,后备种猪 2 5 0 0头 ,商品猪 4 5 0 0头 ,是闽北集种猪、商品猪生产及科研繁育于一体的副食品基地之一。该场日排猪粪便污水约140t,未建沼气工程前 ,直接排入水库 ,严重污染水体。1999年 ,种猪场采用厌氧发酵技术 ,处理猪粪便污水 ,兴建 4× 2 0 0m3沼气工程 ,技术落后 ,基本属于农村户用水压式沼气池的简单放大 ,猪粪便污水直接进入厌氧发酵池 ,出水直接排入水库。工程设计的主要问题是 :1 不设前处理装置 ,冲洗… 相似文献