全文获取类型
收费全文 | 49962篇 |
免费 | 6965篇 |
国内免费 | 4796篇 |
专业分类
电工技术 | 4979篇 |
技术理论 | 10篇 |
综合类 | 6904篇 |
化学工业 | 1055篇 |
金属工艺 | 543篇 |
机械仪表 | 2585篇 |
建筑科学 | 2861篇 |
矿业工程 | 1415篇 |
能源动力 | 636篇 |
轻工业 | 875篇 |
水利工程 | 1445篇 |
石油天然气 | 743篇 |
武器工业 | 1114篇 |
无线电 | 7610篇 |
一般工业技术 | 2534篇 |
冶金工业 | 1548篇 |
原子能技术 | 181篇 |
自动化技术 | 24685篇 |
出版年
2024年 | 103篇 |
2023年 | 693篇 |
2022年 | 1353篇 |
2021年 | 1528篇 |
2020年 | 1689篇 |
2019年 | 1246篇 |
2018年 | 1163篇 |
2017年 | 1363篇 |
2016年 | 1638篇 |
2015年 | 1956篇 |
2014年 | 3608篇 |
2013年 | 3255篇 |
2012年 | 4115篇 |
2011年 | 4216篇 |
2010年 | 3252篇 |
2009年 | 3535篇 |
2008年 | 3807篇 |
2007年 | 4094篇 |
2006年 | 3575篇 |
2005年 | 3157篇 |
2004年 | 2630篇 |
2003年 | 2284篇 |
2002年 | 1649篇 |
2001年 | 1335篇 |
2000年 | 1058篇 |
1999年 | 692篇 |
1998年 | 469篇 |
1997年 | 390篇 |
1996年 | 321篇 |
1995年 | 264篇 |
1994年 | 239篇 |
1993年 | 178篇 |
1992年 | 141篇 |
1991年 | 108篇 |
1990年 | 70篇 |
1989年 | 73篇 |
1988年 | 51篇 |
1987年 | 39篇 |
1986年 | 31篇 |
1985年 | 39篇 |
1984年 | 49篇 |
1983年 | 42篇 |
1982年 | 28篇 |
1981年 | 21篇 |
1980年 | 28篇 |
1979年 | 22篇 |
1977年 | 15篇 |
1975年 | 11篇 |
1965年 | 10篇 |
1964年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
引入句法依存信息到原方面术语,提出一种新的方面术语表示方法,利用Glove词向量表示单词以及单词与单词之间的依存关系,构造出包含句法依存信息的依存关系邻接矩阵和依存关系表示矩阵,利用图卷积神经网络和多头注意力机制将句法依存信息融入到方面术语中,使得方面术语表达与上下文结构高度相关。将改进后的方面词术语表示替换到现有模型后,模型泛化能力得到有效提升。对比试验和分析结果表明:该方法具有有效性和泛化性。 相似文献
2.
Gheorghita Menghiu Vasile Ostafe Radivoje Prodanovi Rainer Fischer Raluca Ostafe 《International journal of molecular sciences》2021,22(6)
Chitinases catalyze the degradation of chitin, a polymer of N-acetylglucosamine found in crustacean shells, insect cuticles, and fungal cell walls. There is great interest in the development of improved chitinases to address the environmental burden of chitin waste from the food processing industry as well as the potential medical, agricultural, and industrial uses of partially deacetylated chitin (chitosan) and its products (chito-oligosaccharides). The depolymerization of chitin can be achieved using chemical and physical treatments, but an enzymatic process would be more environmentally friendly and more sustainable. However, chitinases are slow-acting enzymes, limiting their biotechnological exploitation, although this can be overcome by molecular evolution approaches to enhance the features required for specific applications. The two main goals of this study were the development of a high-throughput screening system for chitinase activity (which could be extrapolated to other hydrolytic enzymes), and the deployment of this new method to select improved chitinase variants. We therefore cloned and expressed the Bacillus licheniformis DSM8785 chitinase A (chiA) gene in Escherichia coli BL21 (DE3) cells and generated a mutant library by error-prone PCR. We then developed a screening method based on fluorescence-activated cell sorting (FACS) using the model substrate 4-methylumbelliferyl β-d-N,N′,N″-triacetyl chitotrioside to identify improved enzymes. We prevented cross-talk between emulsion compartments caused by the hydrophobicity of 4-methylumbelliferone, the fluorescent product of the enzymatic reaction, by incorporating cyclodextrins into the aqueous phases. We also addressed the toxicity of long-term chiA expression in E. coli by limiting the reaction time. We identified 12 mutants containing 2–8 mutations per gene resulting in up to twofold higher activity than wild-type ChiA. 相似文献
3.
4.
为解决沧州市涉地税源管理手段单一等问题,文中提出以测绘地理信息技术为支撑,通过对多源数据组织管理,建立风险分析指标,采用多种GIS空间分析方法构建了涉地风险税源识别模式并在沧州进行应用。结果表明:该模式能有效识别多种涉地风险,为涉地税源管理提供了支撑。 相似文献
5.
Oblivious polynomial evaluation (OPE) is a two-party protocol that allows a receiver, R to learn an evaluation f(α), of a sender, S's polynomial f(x), whilst keeping both α and f(x) private. This protocol has attracted a lot of attention recently, as it has wide ranging applications in the field of cryptography.
In this article we review some of these applications and, additionally, take an in-depth look at the special case of information theoretic OPE. Specifically, we provide a current and critical review of the existing information theoretic OPE protocols in the literature. We divide these protocols into two distinct cases (three-party and distributed OPE) allowing for the easy distinction and classification of future information theoretic OPE protocols. In addition to this work, we also develop several modifications and extensions to existing schemes, resulting in increased security, flexibility and efficiency. Lastly, we also identify a security flaw in a previously published OPE scheme. 相似文献
6.
7.
8.
如何在互联网时代打造一个信息化的管理模式,已经成为广大学校图书管理发展过程中亟待处理的问题。文章就互联网时代下的高职图书管理信息化建设进行了详细探讨,以期能够给广大同仁提供一些借鉴参考,共同为图书管理工作的现代化改革和发展贡献力量。 相似文献
9.
文章首先对智能化电子信息技术进行了深入的研究,而后分析了该技术在应用过程中出现的问题,最后结合该技术的相关特点给出了相应的问题解决措施,希望能够对智能化电子信息技术的发展提供帮助。 相似文献
10.
《International Journal of Hydrogen Energy》2022,47(58):24569-24583
Hydrogen generation from renewable energy resources is considered as a suitable solution to solve the problems related to the energy sector and the reduction of greenhouse gases. The aim of this study is to provide an integrated framework for identifying suitable areas for the construction of wind farms to produce hydrogen. For this purpose, a combined method of Geographic Information System (GIS) and multi-criteria decision making (MCDM) has been used to locate the power plant in Yazd province. The GIS method in the present study consisted of two parts: constraints and criteria. The constraint section included areas that were unsuitable for the construction of wind farms to produce power and hydrogen. In the present study, various aspects such as physical, economic and environmental had been considered as constraints. In the criteria section, eight different criteria from technical aspects (including average wind speed, hydrogen production potential, land slope) and economic aspects (including distance to electricity grid, distance to urban areas, distance to road, distance to railway and distance to centers of High hydrogen consumption) had been investigated. The MCDM tool had been used to weigh the criteria and identify suitable areas. Analytic Hierarchy Process (AHP) technique was used for weighting the criteria. The results of AHP weighting method showed that economic criteria had the highest importance with a value of 0.681. The most significant sub-criterion was the distance to urban areas and the least significant sub-criterion was the distance to power transmission lines. The results of GIS-MCDM analysis had shown that the most proper areas were in the southern and central sectors of Yazd province. In addition, the feasibility of hydrogen production from wind energy had shown that this province had the capacity to generate hydrogen at the rate of 53.6–128.6 tons per year. 相似文献