全文获取类型
收费全文 | 3672篇 |
免费 | 421篇 |
国内免费 | 209篇 |
学科分类
工业技术 | 4302篇 |
出版年
2024年 | 44篇 |
2023年 | 109篇 |
2022年 | 191篇 |
2021年 | 277篇 |
2020年 | 197篇 |
2019年 | 149篇 |
2018年 | 174篇 |
2017年 | 177篇 |
2016年 | 163篇 |
2015年 | 188篇 |
2014年 | 252篇 |
2013年 | 273篇 |
2012年 | 323篇 |
2011年 | 266篇 |
2010年 | 234篇 |
2009年 | 244篇 |
2008年 | 185篇 |
2007年 | 148篇 |
2006年 | 154篇 |
2005年 | 99篇 |
2004年 | 82篇 |
2003年 | 61篇 |
2002年 | 69篇 |
2001年 | 53篇 |
2000年 | 35篇 |
1999年 | 28篇 |
1998年 | 18篇 |
1997年 | 16篇 |
1996年 | 21篇 |
1995年 | 7篇 |
1994年 | 14篇 |
1993年 | 9篇 |
1992年 | 8篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 2篇 |
1962年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有4302条查询结果,搜索用时 15 毫秒
11.
研制一种由醋酸乙烯、丙烯酸丁酯、特种单体共聚而成的水性交联型环保胶粘剂以替代目前广泛使用的氨基树脂,适应绿色环保要求。 相似文献
12.
Two kinds of soluble polyimides from pyromellitic dianhydride with Congo red and 4-sulfanilamide were prepared, respectively. Their structures were characterized by IR and 1H-NMR, and the thermal properties were investigated by DSC and TG–DTA. © 1995 John Wiley & Sons, Inc. 相似文献
13.
14.
The influence of grinding technique on the liberation of clinker minerals and cement properties 总被引:1,自引:0,他引:1
This paper describes a study of the relationship between the physical, chemical and mineralogical parameters of cement products obtained by different grinding mechanisms namely high pressure grinding rolls (HPGR) and ball milling, and their effects upon the properties of cements prepared from the ground clinker. Samples were prepared as narrow size fractions and also as distribution samples. Characterization parameters were ascertained by using XRF, laser sizing, Blaine and BET surface area and image analysis methods. HPGR grinding resulted in higher degrees of liberation of clinker phases arising from the intergranular breakage along the grain boundaries compared to ball mill grinding. As for service properties, water demand of HPGR products was higher than ball mill products resulting from high micro fissured structure. Despite high liberation of particularly alite mineral in HPGR grinding, the compressive strength of ball mill products was slightly higher than HPGR products for narrow size samples. Finally, particle size distribution effect on strength was more obvious for distribution samples; generally ball milling gave higher strength values. 相似文献
15.
为了探究影响GH5家族β-甘露聚糖酶最适pH的各种因素,利用该酶的序列信息,构建了基于氨基酸组成的β-甘露聚糖酶理化性质与其最适pH的相关性模型。结果表明:该酶N端氨基酸序列是影响其最适pH的重要因素,在243个理化性质中有17个呈极显著相关,其中7个呈正相关。优化的转移能量参数相关性最高,为0.78:7个正相关的理化性质中,与螺旋相关的理化性质占3个。优化的转移能量参数和螺旋是影响pH稳定性的最重要的因素。所建立的模型为研究该酶酸碱适应性机理提供了一种简单有效的方法。 相似文献
16.
17.
In the present study, the effects of charge‐transfer complex formation and intramolecular fragmentation (side‐chain lactonization) in radical copolymerization of tert‐butyl vinyl ether (t‐BVE) with anhydrides of maleic (MA) and citraconic (CA) acids and the structure–thermal behavior relationships of the resulting copolymers were examined using the 1H‐NMR, FTIR, DSC, and TGA analysis methods. It was shown that copolymerization under the chosen conditions proceeded through intramolecular fragmentation with the formation of γ‐lactone units. Side‐chain fragmentation of t‐BVE–MA and t‐BVE–CA copolymers also was confirmed by TGA and DSC analysis. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2455–2463, 2006 2006 相似文献
18.
根据上海某超长盾构隧道工程监测的实践,介绍了盾构隧道监测的一般内容:地表沉降和地下管线安全监测;地面房屋沉降和倾斜观测;水位测试;土体水平位移监测和局部地段隧道沉降、净空收敛监测。并从几个方面对监测数据作了详细的分析,得出了盾构推进方向和隧道纵向的沉降变化及隧道横向沉降槽的变化规律,同时分析了盾构切口距建筑物沉降点距离和沉降量的关系,最后得出了盾构推进和地表沉降的变化规律,提出了地表沉降的5个阶段,即:前期沉降阶段;开挖面前的隆沉;通过期间沉降阶段;盾尾间隙沉降阶段和后期沉降阶段。 相似文献
19.
Coverage is a fundamental problem in sensor networks. Sensor coverage, which reflects how well a sensor network is monitored by sensors, is an important measure for the quality of service (QoS) that a sensor network can provide. In mobile sensor networks, the mobility of sensor nodes can be utilized to enhance the coverage of the network. Since the movement of sensor nodes will consume much energy, this mobility of sensor nodes should be properly managed by some pre-defined schemes or protocols. By noticing this issue, some existing works have proposed several movement-assisted sensor deployment schemes. These works assume that the target field is a 2-dimensional space. In this paper, we study a generalized case of this problem whereby the target field can be a space which ranges from 1-dimensional to 3-dimensional. Two variations of the movement-assisted sensor deployment problem with different optimization objectives were formulated. We identify a set of basic attributes which can be used as guidelines for designing movement-assisted sensor deployment schemes. Based on these attributes, we propose efficient algorithms for both variants of the movement-assisted sensor deployment problem. 相似文献
20.
Self-repairing systems are those that are able to reconfigure themselves following disruptions to bring them back into a defined normal state. In this paper we explore the self-repair ability of some cellular automata-like systems, which differ from classical cellular automata by the introduction of a local diffusion process inspired by chemical signalling processes in biological development. The update rules in these systems are evolved using genetic programming to self-assemble towards a target pattern. In particular, we demonstrate that once the update rules have been evolved for self-assembly, many of those update rules also provide a self-repair ability without any additional evolutionary process aimed specifically at self-repair. 相似文献