全文获取类型
收费全文 | 3897篇 |
免费 | 319篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 49篇 |
综合类 | 1篇 |
化学工业 | 1223篇 |
金属工艺 | 151篇 |
机械仪表 | 118篇 |
建筑科学 | 89篇 |
矿业工程 | 19篇 |
能源动力 | 172篇 |
轻工业 | 753篇 |
水利工程 | 15篇 |
石油天然气 | 12篇 |
武器工业 | 1篇 |
无线电 | 174篇 |
一般工业技术 | 712篇 |
冶金工业 | 90篇 |
原子能技术 | 14篇 |
自动化技术 | 628篇 |
出版年
2023年 | 40篇 |
2022年 | 130篇 |
2021年 | 245篇 |
2020年 | 135篇 |
2019年 | 155篇 |
2018年 | 220篇 |
2017年 | 208篇 |
2016年 | 241篇 |
2015年 | 193篇 |
2014年 | 257篇 |
2013年 | 427篇 |
2012年 | 264篇 |
2011年 | 214篇 |
2010年 | 177篇 |
2009年 | 201篇 |
2008年 | 148篇 |
2007年 | 131篇 |
2006年 | 88篇 |
2005年 | 60篇 |
2004年 | 68篇 |
2003年 | 65篇 |
2002年 | 51篇 |
2001年 | 27篇 |
2000年 | 35篇 |
1999年 | 21篇 |
1998年 | 27篇 |
1997年 | 17篇 |
1996年 | 12篇 |
1995年 | 17篇 |
1994年 | 11篇 |
1993年 | 12篇 |
1992年 | 9篇 |
1990年 | 19篇 |
1989年 | 10篇 |
1988年 | 10篇 |
1987年 | 14篇 |
1986年 | 13篇 |
1985年 | 21篇 |
1984年 | 32篇 |
1983年 | 32篇 |
1982年 | 23篇 |
1981年 | 22篇 |
1980年 | 24篇 |
1979年 | 21篇 |
1978年 | 7篇 |
1977年 | 11篇 |
1976年 | 8篇 |
1975年 | 7篇 |
1974年 | 7篇 |
1973年 | 10篇 |
排序方式: 共有4221条查询结果,搜索用时 9 毫秒
131.
132.
133.
In this work, we aim at quantifying quantum channel output similarity. In order to achieve this, we introduce the notion of quantum channel superfidelity, which gives us an upper bound on the quantum channel fidelity. This quantity is expressed in a clear form using the Kraus representation of a quantum channel. As examples, we show potential applications of this quantity in the quantum control field. 相似文献
134.
135.
136.
137.
Ultrastructural and developmental toxicity of potato and tomato leaf extracts to beet armyworm,Spodoptera exigua (lepidoptera: noctuidae) 下载免费PDF全文
Zbigniew Adamski Katarzyna Radtke Agnieszka Kopiczko Szymon Chowański Paweł Marciniak Monika Szymczak Marta Spochacz Patrizia Falabella Filomena Lelario Laura Scrano Sabino A. Bufo 《Microscopy research and technique》2016,79(10):948-958
Beet Armyworm, Spodoptera exigua is a herbivorous moth and a serious pest of many economically important plants, which are used as food sources. Because of rigorous standards of food quality, usage of synthetic insecticides in crop protection, against pests, is limited. Solanaceae plant extracts may be a relatively cheap source of efficient natural insecticides that can limit usage of synthetic substances. Their biological activity is not fully known. In particular, ultrastructural studies, using transmission electron microscopy, are not usual. In the present article we describe the effects of sublethal concentrations of tomato and potato leaf extracts against S. exigua. Acute lethal effects were not observed. Both extracts exerted similar effects within midgut and fat body cells. Midgut cells were not significantly altered while fat body cells showed prominent swelling of nuclear envelope and endoplasmic reticulum, vacuolization of mitochondria and fusion of fat droplets. These changes were much more intensive within groups exposed to potato than tomato extracts at highest concentration at least. Light microscopy was used to observe and document developmental alterations of S. exigua exposed to potato and tomato leaf extracts. Potato leaf extracts significantly decreased hatching success and caused morphological malformations of imagoes. Among them, malformations of wings were the most prominent. Interestingly, these effects were not observed within populations exposed to tomato extracts at highest concentration at least. 相似文献
138.
The issue of computing (co)homology generators of a cell complex is gaining a pivotal role in various branches of science. While this issue may be rigorously solved in polynomial time, it is still overly demanding for large scale problems. Drawing inspiration from low-frequency electrodynamics, this paper presents a physics inspired algorithm for first cohomology group computations on three-dimensional complexes. The algorithm is general and exhibits orders of magnitude speed up with respect to competing ones, allowing to handle problems not addressable before. In particular, when generators are employed in the physical modeling of magneto-quasistatic problems, this algorithm solves one of the most long-lasting problems in low-frequency computational electromagnetics. In this case, the effectiveness of the algorithm and its ease of implementation may be even improved by introducing the novel concept of lazy cohomology generators. 相似文献
139.
The finite satisfiability problem for guarded fixpoint logic is decidable and complete for 2ExpTime (resp. ExpTime for formulas of bounded width). 相似文献
140.
Effects of the spray drying conditions of chokeberry (Aronia melanocarpa L.) juice concentrate on the physicochemical properties of powders 下载免费PDF全文
Jolanta Gawałek Ewa Domian Antoni Ryniecki Sławomir Bakier 《International Journal of Food Science & Technology》2017,52(9):1933-1941
A semi‐industrial spray drying process of chokeberry juice concentrate using maltodextrin was analysed. The influence of the content and dextrose equivalent (DE) of maltodextrin, inlet air temperature and rotary disc atomiser speed was studied on the physicochemical properties of the obtained powders. The size and structure of the powder particles, bulk density, moisture content, flowability, yield and total polyphenol content were analysed. An increase in carrier content from 50% to 70% caused a 4.9% increase in total polyphenol retention, better flowability (Hausner ratio decrease of 0.17) and greater yield of the powder (60%). An increase in the drying temperature (150–170 °C) caused larger particle size and improved powder flowability but also resulted in greater loss of total polyphenols. A decrease in rotary atomiser speed (11 000–15 000 rpm) had a moderate influence on particle size and improvement in flowability but had no effect on polyphenol retention. Changes in the DE (8–22) of maltodextrin as a carrier indicated a moderate growing dependence on particle size and worse flowability. 相似文献