全文获取类型
收费全文 | 262316篇 |
免费 | 4874篇 |
国内免费 | 442篇 |
专业分类
电工技术 | 4421篇 |
综合类 | 267篇 |
化学工业 | 43389篇 |
金属工艺 | 9707篇 |
机械仪表 | 7859篇 |
建筑科学 | 6110篇 |
矿业工程 | 1438篇 |
能源动力 | 5601篇 |
轻工业 | 29435篇 |
水利工程 | 2729篇 |
石油天然气 | 5116篇 |
武器工业 | 33篇 |
无线电 | 25975篇 |
一般工业技术 | 48537篇 |
冶金工业 | 49584篇 |
原子能技术 | 6005篇 |
自动化技术 | 21426篇 |
出版年
2021年 | 2739篇 |
2020年 | 2084篇 |
2019年 | 2630篇 |
2018年 | 4598篇 |
2017年 | 4529篇 |
2016年 | 4837篇 |
2015年 | 3112篇 |
2014年 | 4914篇 |
2013年 | 12273篇 |
2012年 | 7734篇 |
2011年 | 9687篇 |
2010年 | 7678篇 |
2009年 | 8192篇 |
2008年 | 8605篇 |
2007年 | 8631篇 |
2006年 | 7473篇 |
2005年 | 6542篇 |
2004年 | 6284篇 |
2003年 | 6042篇 |
2002年 | 6033篇 |
2001年 | 5822篇 |
2000年 | 5592篇 |
1999年 | 5549篇 |
1998年 | 14011篇 |
1997年 | 9828篇 |
1996年 | 7437篇 |
1995年 | 5657篇 |
1994年 | 4981篇 |
1993年 | 4886篇 |
1992年 | 3745篇 |
1991年 | 3391篇 |
1990年 | 3595篇 |
1989年 | 3466篇 |
1988年 | 3301篇 |
1987年 | 2900篇 |
1986年 | 2937篇 |
1985年 | 3386篇 |
1984年 | 3226篇 |
1983年 | 2872篇 |
1982年 | 2724篇 |
1981年 | 2824篇 |
1980年 | 2725篇 |
1979年 | 2614篇 |
1978年 | 2680篇 |
1977年 | 3003篇 |
1976年 | 3959篇 |
1975年 | 2372篇 |
1974年 | 2243篇 |
1973年 | 2383篇 |
1972年 | 1959篇 |
排序方式: 共有10000条查询结果,搜索用时 406 毫秒
21.
Belov M. I. Anashin D. V. Kabdin N. E. Storchevoy V. F. Sudnik Yu. A. 《Russian Engineering Research》2022,42(11):1110-1116
Russian Engineering Research - The stability of robot-mower motion in a specific direction is considered. The direction is regulated by means of an angular sensor and a programmable controller... 相似文献
22.
Yang Hu Stephanie M. Sjoberg Chunpen Chen Amber L. Hauvermale Craig F. Morris Stephen R. Delwiche Ashley E. Cannon Camille M. Steber Zhiwu Zhang 《Comprehensive Reviews in Food Science and Food Safety》2022,21(3):2105-2117
This review examines the application, limitations, and potential alternatives to the Hagberg–Perten falling number (FN) method used in the global wheat industry for detecting the risk of poor end-product quality mainly due to starch degradation by the enzyme α-amylase. By viscometry, the FN test indirectly detects the presence of α-amylase, the primary enzyme that digests starch. Elevated α-amylase results in low FN and damages wheat product quality resulting in cakes that fall, and sticky bread and noodles. Low FN can occur from preharvest sprouting (PHS) and late maturity α-amylase (LMA). Moist or rainy conditions before harvest cause PHS on the mother plant. Continuously cool or fluctuating temperatures during the grain filling stage cause LMA. Due to the expression of additional hydrolytic enzymes, PHS has a stronger negative impact than LMA. Wheat grain with low FN/high α-amylase results in serious losses for farmers, traders, millers, and bakers worldwide. Although blending of low FN grain with sound wheat may be used as a means of moving affected grain through the marketplace, care must be taken to avoid grain lots from falling below contract-specified FN. A large amount of sound wheat can be ruined if mixed with a small amount of sprouted wheat. The FN method is widely employed to detect α-amylase after harvest. However, it has several limitations, including sampling variability, high cost, labor intensiveness, the destructive nature of the test, and an inability to differentiate between LMA and PHS. Faster, cheaper, and more accurate alternatives could improve breeding for resistance to PHS and LMA and could preserve the value of wheat grain by avoiding inadvertent mixing of high- and low-FN grain by enabling testing at more stages of the value stream including at harvest, delivery, transport, storage, and milling. Alternatives to the FN method explored here include the Rapid Visco Analyzer, enzyme assays, immunoassays, near-infrared spectroscopy, and hyperspectral imaging. 相似文献
23.
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
24.
Vanessa Modelski Schatkoski Thaís Larissa do Amaral Montanheiro Beatriz Rossi Canuto de Menezes Raissa Monteiro Pereira Karla Faquine Rodrigues Renata Guimarães Ribas Diego Morais da Silva Gilmar Patrocínio Thim 《Ceramics International》2021,47(3):2999-3012
Studies related to biomaterials that stimulate the repair of living tissue have increased considerably, improving the quality of many people's lives that require surgery due to traumatic accidents, bone diseases, bone defects, and reconstructions. Among these biomaterials, bioceramics and bioactive glasses (BGs) have proved to be suitable for coating materials, cement, scaffolds, and nanoparticles, once they present good biocompatibility and degradability, able to generate osteoconduction on the surrounding tissue. However, the role of biomaterials in hard tissue engineering is not restricted to a structural replacement or for guiding tissue regeneration. Nowadays, it is expected that biomaterials develop a multifunctional role when implanted, orchestrating the process of tissue regeneration and providing to the body the capacity to heal itself. In this way, the incorporation of specific metal ions in bioceramics and BGs structure, including magnesium, silver, strontium, lithium, copper, iron, zinc, cobalt, and manganese are currently receiving enhanced interest as biomaterials for biomedical applications. When an ion is incorporated into the bioceramic structure, a new category of material is created, which has several unique properties that overcome the disadvantages of primitive material and favors its use in different biomedical applications. The doping can enhance handling properties, angiogenic and osteogenic performance, and antimicrobial activity. Therefore, this review aims to summarize the effect of selected metal ion dopants into bioceramics and silicate-based BGs in bone tissue engineering. Furthermore, new applications for doped bioceramics and BGs are highlighted, including cancer treatment and drug delivery. 相似文献
25.
26.
L.J. Espinoza-Pérez S. Esquivel-Medina E. López-Honorato 《Ceramics International》2021,47(11):15527-15532
The influence of the microstructure on the corrosion rate of three monolithic SiC samples in FLiNaK salt at 900 °C for 250 h was studied. The SiC samples, labeled as SiC-1, SiC-2, and SiC-3, had corrosion rates of 0.137, 0.020, and 0.043 mg/cm2h, respectively. Compared with grain size and the presence of special grain boundaries (i.e., Σ3), the content of high-angle grain boundaries (HAGBs) appeared to have the strongest influence on the corrosion rate of SiC in FLiNaK salt, since the corrosion rate increased six times as the concentration of high-angle grain boundaries increased from 19 to 32% for SiC-2 and SiC-1, respectively. These results stress the importance of controlling the content of HAGBs during the production process of SiC. 相似文献
27.
Andrade R. G. S. A. de Oliveira A. E. Guerra V. G. 《Theoretical Foundations of Chemical Engineering》2022,56(4):504-512
Theoretical Foundations of Chemical Engineering - The corona onset voltage is an important operating parameter in the electrostatic precipitation of nanoparticulate, however, its experimental... 相似文献
28.
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
29.
Golubev N. V. Ignat’eva E. S. Maurus A. A. Ziyatdinova M. Z. Lopatina E. V. Lorenzi R. Paleari A. Sigaev V. N. 《Glass and Ceramics》2021,77(11-12):415-418
Glass and Ceramics - The influence of Al2O3 as an additive and the heat-treatment regime on the luminescence spectra of gallate glass-ceramics was investigated. It is shown that its luminescence... 相似文献
30.
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