全文获取类型
收费全文 | 429534篇 |
免费 | 5570篇 |
国内免费 | 1358篇 |
专业分类
电工技术 | 8527篇 |
综合类 | 448篇 |
化学工业 | 60121篇 |
金属工艺 | 16605篇 |
机械仪表 | 12983篇 |
建筑科学 | 9610篇 |
矿业工程 | 1729篇 |
能源动力 | 10402篇 |
轻工业 | 34444篇 |
水利工程 | 3960篇 |
石油天然气 | 6314篇 |
武器工业 | 74篇 |
无线电 | 57404篇 |
一般工业技术 | 81453篇 |
冶金工业 | 88199篇 |
原子能技术 | 8268篇 |
自动化技术 | 35921篇 |
出版年
2021年 | 3067篇 |
2019年 | 3067篇 |
2018年 | 5188篇 |
2017年 | 5255篇 |
2016年 | 5506篇 |
2015年 | 3584篇 |
2014年 | 6224篇 |
2013年 | 18178篇 |
2012年 | 10218篇 |
2011年 | 14007篇 |
2010年 | 11163篇 |
2009年 | 12750篇 |
2008年 | 13710篇 |
2007年 | 13738篇 |
2006年 | 12450篇 |
2005年 | 11529篇 |
2004年 | 11262篇 |
2003年 | 10972篇 |
2002年 | 10502篇 |
2001年 | 10873篇 |
2000年 | 10300篇 |
1999年 | 10931篇 |
1998年 | 28356篇 |
1997年 | 19612篇 |
1996年 | 15159篇 |
1995年 | 11525篇 |
1994年 | 10105篇 |
1993年 | 10026篇 |
1992年 | 7423篇 |
1991年 | 6997篇 |
1990年 | 6807篇 |
1989年 | 6393篇 |
1988年 | 6004篇 |
1987年 | 5112篇 |
1986年 | 5083篇 |
1985年 | 5864篇 |
1984年 | 5387篇 |
1983年 | 4806篇 |
1982年 | 4512篇 |
1981年 | 4733篇 |
1980年 | 4336篇 |
1979年 | 4070篇 |
1978年 | 3936篇 |
1977年 | 4714篇 |
1976年 | 6021篇 |
1975年 | 3560篇 |
1974年 | 3503篇 |
1973年 | 3474篇 |
1972年 | 2835篇 |
1971年 | 2569篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Kumar S. Ganesh Sridhar S. S. Hussain Azham Manikanthan S. V. Padmapriya T. 《Multimedia Tools and Applications》2022,81(7):9091-9109
Multimedia Tools and Applications - Discovering the relevant web services for specific applications in the dynamically changing business world becomes very critical. Researchers have used many... 相似文献
32.
Belcher Calvin H. Zheng Baolong MacDonald Benjamin E. Langlois Eric D. Lehman Benjamin Pearce Charles Delaney Robert Apelian Diran Lavernia Enrique J. Monson Todd C. 《Journal of Materials Science》2022,57(9):5518-5532
Journal of Materials Science - For transformers and inductors to meet the world’s growing demand for electrical power, more efficient soft magnetic materials with high saturation magnetic... 相似文献
33.
Kruglikov S. S. Zagorskii D. L. Kolesnikov V. A. Doludenko I. M. Bedin S. A. 《Theoretical Foundations of Chemical Engineering》2021,55(5):942-951
Theoretical Foundations of Chemical Engineering - The effect of the electrolyte composition, mass-transfer conditions, pore diameter, interpore distance, and electric parameters on the formation of... 相似文献
34.
T.V. Vakalova L.P. Devyashina Sh.M. Sharafeev N.P. Sergeev 《Ceramics International》2021,47(11):15282-15292
One of the drawbacks of fusible clays is the narrow sintering interval due to a sharp increase in the amount of iron-silicate melt at a temperature of 1000–1100 °C, which hardens in the form of a glass phase upon cooling. This leads to a relatively low mechanical strength of the calcined samples and causes the danger of melting the granular material surface from such clays during the firing process. To increase the strength of samples of fusible clays, the influence of diabase and granitoid rocks was considered. It was found that the strengthening effect of diabase and granitoid rock additives in an amount of 20–50% in a mixture with fusible clay is due to an increase of total content of the crystalline phase (mullite, cristobalite and residual quartz) from 18–20% in clays without additives to 22–28 % - in mixtures with diabase and to 28–34% - with granitoid additives) at a temperature of 1050–1100 °C. This increase is due to the activation of synthesis processes of secondary mullite and crystallization from alkali-rich feldspar melt of amorphous silica, released from the structure of clay minerals. The established influence of the igneous rocks used made it possible to develop compositions and propose process flow sheet for producing aluminosilicate proppants based on fusible clays. The use of granitoid and diabase rocks in an amount of 20–70% with fusible clays produces lightweight aluminosilicate proppants with bulk density of 1.40–1.46 g/cm3 at temperature range of 1050–1100 °C, which can endure destructive pressures up to 34.5–52 MPa. 相似文献
35.
Margarita A. Sazonova Vasily V. Sinyov Anastasia I. Ryzhkova Marina D. Sazonova Tatiana V. Kirichenko Victoria A. Khotina Zukhra B. Khasanova Natalya A. Doroschuk Vasily P. Karagodin Alexander N. Orekhov Igor A. Sobenin 《International journal of molecular sciences》2021,22(2)
Chronic stress is a combination of nonspecific adaptive reactions of the body to the influence of various adverse stress factors which disrupt its homeostasis, and it is also a corresponding state of the organism’s nervous system (or the body in general). We hypothesized that chronic stress may be one of the causes occurence of several molecular and cellular types of stress. We analyzed literary sources and considered most of these types of stress in our review article. We examined genes and mutations of nuclear and mitochondrial genomes and also molecular variants which lead to various types of stress. The end result of chronic stress can be metabolic disturbance in humans and animals, leading to accumulation of reactive oxygen species (ROS), oxidative stress, energy deficiency in cells (due to a decrease in ATP synthesis) and mitochondrial dysfunction. These changes can last for the lifetime and lead to severe pathologies, including neurodegenerative diseases and atherosclerosis. The analysis of literature allowed us to conclude that under the influence of chronic stress, metabolism in the human body can be disrupted, mutations of the mitochondrial and nuclear genome and dysfunction of cells and their compartments can occur. As a result of these processes, oxidative, genotoxic, and cellular stress can occur. Therefore, chronic stress can be one of the causes forthe occurrence and development of neurodegenerative diseases and atherosclerosis. In particular, chronic stress can play a large role in the occurrence and development of oxidative, genotoxic, and cellular types of stress. 相似文献
36.
Multicomponent Diamond-Like Semiconductors Based on the InBV–CdS System: Bulk and Surface Properties
Semiconductors - According to developed methods, in the fields of the mutual solubility of initial binary compounds (InP, InSb, and CdS), solid solutions of the InP–CdS and InSb–CdS... 相似文献
37.
Ivashchuk O. A. Ivashchuk O. D. Fedorov V. I. Shtana A. I. 《Russian Engineering Research》2020,40(11):970-972
Russian Engineering Research - Models based on regression analysis for predicting the operational efficiency of high-pressure roller crushers are considered. A systematized and structured... 相似文献
38.
Popov N. N. Presnyakov D. V. Lar’kin V. F. 《Journal of Machinery Manufacture and Reliability》2020,49(3):232-236
Journal of Machinery Manufacture and Reliability - A device based on smart alloys has been designed for use in machine building items, in particular, in nuclear engineering, for preventing... 相似文献
39.
Klimis?S.?NtalianisEmail author Anastasios?D.?Doulamis Nikolaos?D.?Doulamis Nikos?E.?Mastorakis Athanasios?S.?Drigas 《Journal of Signal Processing Systems》2015,80(2):153-161
In this paper, we present a novel memory access reduction scheme (MARS) for two-dimension fast cosine transform (2-D FCT). It targets programmable DSPs with high memory-access latency. It reduces the number of memory accesses by: 1) reducing the number of weighting factors and 2) combining butterflies in vector-radix 2-D FCT pruning diagram from two stages to one stage with an efficient structure. Hardware platform based on general purpose processor is used to verify the effectiveness of the proposed method for vector-radix 2-D FCT pruning implementation. Experimental results validate the benefits of the proposed method with reduced memory access, less clock cycle and fewer memory space compared with the conventional implementation. 相似文献
40.