全文获取类型
收费全文 | 26820篇 |
免费 | 3285篇 |
国内免费 | 1554篇 |
专业分类
电工技术 | 1898篇 |
技术理论 | 1篇 |
综合类 | 1722篇 |
化学工业 | 4175篇 |
金属工艺 | 1939篇 |
机械仪表 | 1906篇 |
建筑科学 | 2168篇 |
矿业工程 | 804篇 |
能源动力 | 743篇 |
轻工业 | 1767篇 |
水利工程 | 597篇 |
石油天然气 | 1573篇 |
武器工业 | 289篇 |
无线电 | 3245篇 |
一般工业技术 | 3084篇 |
冶金工业 | 1338篇 |
原子能技术 | 477篇 |
自动化技术 | 3933篇 |
出版年
2024年 | 205篇 |
2023年 | 576篇 |
2022年 | 1118篇 |
2021年 | 1452篇 |
2020年 | 1102篇 |
2019年 | 934篇 |
2018年 | 932篇 |
2017年 | 1074篇 |
2016年 | 966篇 |
2015年 | 1456篇 |
2014年 | 1741篇 |
2013年 | 1900篇 |
2012年 | 2063篇 |
2011年 | 1966篇 |
2010年 | 1759篇 |
2009年 | 1582篇 |
2008年 | 1452篇 |
2007年 | 1398篇 |
2006年 | 1397篇 |
2005年 | 1106篇 |
2004年 | 744篇 |
2003年 | 638篇 |
2002年 | 635篇 |
2001年 | 523篇 |
2000年 | 460篇 |
1999年 | 436篇 |
1998年 | 344篇 |
1997年 | 269篇 |
1996年 | 271篇 |
1995年 | 194篇 |
1994年 | 159篇 |
1993年 | 115篇 |
1992年 | 106篇 |
1991年 | 75篇 |
1990年 | 64篇 |
1989年 | 49篇 |
1988年 | 43篇 |
1987年 | 31篇 |
1986年 | 40篇 |
1985年 | 22篇 |
1984年 | 17篇 |
1983年 | 12篇 |
1982年 | 13篇 |
1981年 | 18篇 |
1980年 | 13篇 |
1979年 | 10篇 |
1977年 | 10篇 |
1976年 | 23篇 |
1975年 | 10篇 |
1974年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
Scaffold‐guided tissue engineering based on synthetic and natural occurring polymers has gained many interests in recent year. In this study, the development of a chitosan‐heparin artificial extracellular matrix (AECM) is reported. Three‐dimensional, macroporous composite AECMs composed of heparin (Hep) and chitosan (Chito) were prepared by an interpolyelectrolyte complex/lyophilization method. The Chito‐Hep composite AECMs were, respectively, crosslinked with glutaraldehyde, as well as cocrosslinked with N,N‐(3‐dimethylaminopropyl)‐N′‐ethyl carbodiimide (EDC/NHS) and N‐hydroxysuccinimide (NHS). The crosslinking reactions were examined by FT‐IR analysis. In physiological buffer solution (PBS), the EDC/NHS‐crosslinked Chito‐Hep composite AECM showed a relative lower water retention ratio than its glutaraldehyde‐crosslinked counterparts. The EDC/NHS‐crosslinked Chito‐Hep composite AECMs showed excellent biocompatibility, according to the results of the in vitro cytotoxic test. This result suggested that the EDC/NHS‐crosslinked Chito‐Hep composite AECMs might be a potential biomaterial for scaffold‐guided tissue engineering applications. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
112.
Alpass Fiona; Flett Ross; Humphries Steve; Massey Claire; Morriss Stuart; Long Nigel 《Canadian Metallurgical Quarterly》2004,11(3):270
Previous studies have identified a number of different farm stressors and have reported gender and age differences in levels of stress. This study aimed to determine stress experienced by New Zealand dairy farmers, particularly in relation to adoption of new technology and its relationship to age and gender. Measures of farm stress and adoption of technology were completed by 985 dairy farmers. The highest levels of stress were reported for time pressures, machinery breakdown, weather, and government policies. Stress related to new technologies occurred rarely. Women reported more stress and higher levels of stress for understanding new technologies. There was also an increase in severity of stress with age related to new technologies. Overall, stress levels were moderate and may reflect favorable economic conditions. The findings suggest a need to tailor stress interventions to meet specific needs. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
113.
时移地震非一致性影响研究与互均衡效果验证 总被引:6,自引:0,他引:6
用地震子波对时移地震非一致性造成影响进行了模拟。将影响因素概括为4种形式,即时移、相位变化、振幅量级不一致,频宽不一致。采用互均衡技术对以上4种情况进行校正,达到了理想的效果。为实际资料的处理和方法研究奠定了理论基础。 相似文献
114.
115.
This research used a weight-of-evidence approach to evaluate sources of contaminants in a drinking water watershed that serves as part of the City of Boston's water supply. The approach incorporated land use analysis using GIS, sanitary surveys, traditional water quality monitoring and microbial source tracking (MST) tools. Case-study tributaries were selected based on elevated faecal coliform counts. Land use analysis and sanitary surveys were used to identify suspected microbial sources, including residential septic systems, agricultural animal operations, commercial/industrial operations and wildlife activity. Sampling sites were selected to hydrologically isolate potential contamination sources. Samples were collected seasonally over 1 year and analysed for traditional and MST parameters. Results demonstrated that both septic systems and a horse stable were contributing microbial loads in the first tributary. In the second tributary, septic systems from the townhouses were contributing microbial loads while a plant nursery was contributing organic matter. This evidence was used to evaluate best management practices to mitigate the contamination. 相似文献
116.
Yong Chen Xiaofeng Liao Kwok-Wo Wong 《Circuits and Systems II: Express Briefs, IEEE Transactions on》2006,53(7):527-529
An encryption system with discretized skew tent map has been proposed recently by N. Masuda . However, there is a fundamental weakness with this chaotic cryptographic scheme. In this paper, a chosen plaintext attack requiring only two plaintexts is proposed. An improved version of this attack that narrows the key space need to be searched is also suggested. The test results demonstrate that this encryption cryptosystem is easily broken under the proposed chosen plaintext attack. 相似文献
117.
李海龙 《消防技术与产品信息》2007,(10):31-32,90
根据地下公共娱乐场所的结构特点和火灾特点,结合某地下娱乐场所的防排烟设计,探讨如何进行防排烟设计。 相似文献
118.
119.
超滤膜的改性研究及应用 总被引:14,自引:0,他引:14
随着超滤膜技术的发展,人们对超滤膜提出了各种各样的特性要求,其中解决膜表面的污染问题变得越来越紧迫.超滤膜改性,尤其是在膜表面引入亲水性基团是解决问题的关键.本文从这点出发,结合自身的工作,总结了近年高分子超滤膜改性方面的研究进展,包括表面活性剂在膜表面的吸附改性、等离子体改性、辐照改性、高分子合金和表面化学反应等几种改性方法. 相似文献
120.
Lee Y. Wangi Jung-Sheng Wu Sheng-Mao Tseng Chang-Shu Kuo Kuo-Huang Hsieh Wen-Bin Liau Long Y. Chiang 《Journal of Polymer Research》1996,3(1):1-10
Utilization of polyhydroxylated C60 (fullerenols) in a condensation reaction with diisocyanated oligo(tetramethylene oxide) led to the successful fabrication of elastomeric poly (urethane-ether) networks. These polymer networks exhibit interesting thermal behavior at low temperatures, improved tensile strength and elongation at ambient temperatures, and enhanced thermal mechanical stability at high temperatures, as compared with those of the parent linear polyurethane analogues; or with the conventional oligo (tetramethylene oxide)-derived polyurethane elastomers cross-linked by trihydroxylated reagents (1,I,1-trismethylol propane) or tetrahydroxylated reagents (pentaerythritol). The presence of a limited quantity of water molecules in the condensation reaction of fullerenols with diisocyanated prepolymers modified the physical properties of the resulting elastomeric products with a notable increase in tensile strength, modulus, and Ts over those of elasotmers prepared under anhydrous conditions. These water molecules contributed effectively to the increase of the number of cross-linking centers during the reaction. 相似文献