全文获取类型
收费全文 | 51692篇 |
免费 | 5858篇 |
国内免费 | 1841篇 |
专业分类
电工技术 | 2579篇 |
综合类 | 4060篇 |
化学工业 | 10071篇 |
金属工艺 | 5500篇 |
机械仪表 | 2567篇 |
建筑科学 | 5798篇 |
矿业工程 | 992篇 |
能源动力 | 8530篇 |
轻工业 | 2932篇 |
水利工程 | 512篇 |
石油天然气 | 2361篇 |
武器工业 | 365篇 |
无线电 | 1480篇 |
一般工业技术 | 5968篇 |
冶金工业 | 3488篇 |
原子能技术 | 1096篇 |
自动化技术 | 1092篇 |
出版年
2024年 | 222篇 |
2023年 | 698篇 |
2022年 | 1432篇 |
2021年 | 1626篇 |
2020年 | 1748篇 |
2019年 | 1403篇 |
2018年 | 1251篇 |
2017年 | 1478篇 |
2016年 | 1787篇 |
2015年 | 1785篇 |
2014年 | 3117篇 |
2013年 | 3223篇 |
2012年 | 3632篇 |
2011年 | 3842篇 |
2010年 | 2838篇 |
2009年 | 2932篇 |
2008年 | 2330篇 |
2007年 | 3265篇 |
2006年 | 2959篇 |
2005年 | 2633篇 |
2004年 | 2290篇 |
2003年 | 2020篇 |
2002年 | 1906篇 |
2001年 | 1551篇 |
2000年 | 1320篇 |
1999年 | 1069篇 |
1998年 | 874篇 |
1997年 | 770篇 |
1996年 | 617篇 |
1995年 | 543篇 |
1994年 | 434篇 |
1993年 | 359篇 |
1992年 | 307篇 |
1991年 | 203篇 |
1990年 | 165篇 |
1989年 | 170篇 |
1988年 | 109篇 |
1987年 | 80篇 |
1986年 | 66篇 |
1985年 | 50篇 |
1984年 | 73篇 |
1983年 | 56篇 |
1982年 | 54篇 |
1981年 | 14篇 |
1980年 | 15篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1959年 | 30篇 |
1951年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Molecular structure and granule morphology of native and heat‐moisture‐treated pinhão starch 下载免费PDF全文
Vania Z. Pinto Khalid Moomand Nathan L. Vanier Rosana Colussi Franciene A. Villanova Elessandra R. Zavareze Loong‐Tak Lim Alvaro R. G. Dias 《International Journal of Food Science & Technology》2015,50(2):282-289
Pinhão seed is an unconventional source of starch and the pines grow up in native forests of southern Latin America. In this study, pinhão starch was adjusted at 15, 20 and 25% moisture content and heated to 100, 110 and 120 °C for 1 h. A decrease in λ max (starch/iodine complex) was observed as a result of increase in temperature and moisture content of HMT. The ratio of crystalline to amorphous phase in pinhão starch was determined via Fourier transform infra red by taking 1045/1022 band ratio. A decrease in crystallinity occurred as a result of HMT. Polarised light microscopy indicated a loss of birefringence of starch granules under 120 °C at 25% moisture content. Granule size distribution was further confirmed via scanning electron microscopy which showed the HMT effects. These results increased the understanding on molecular and structural properties of HMT pinhão starch and broadened its food and nonfood industrial applications. 相似文献
2.
Xiaopo Wu Yangming Shi Weibo Meng Xiaofei Ma Nian Fang 《International Journal of Satellite Communications and Networking》2019,37(3):283-291
Electromagnetic signal emitted by satellite communication (satcom) transmitters are used to identify specific individual uplink satcom terminals sharing the common transponder in real environment, which is known as specific emitter identification (SEI) that allows for early indications and warning (I&W) of the targets carrying satcom furnishment and furthermore the real time electromagnetic situation awareness in military operations. In this paper, the authors are the first to propose the identification of specific transmitters of satcom by using probabilistic neural networks (PNN) to reach the goal of target recognition. We have been devoted to the examination by exploring the feasibility of utilizing the Hilbert transform to signal preprocessing, applying the discrete wavelet transform to feature extraction, and employing the PNN to perform the classification of stationary signals. There are a total of 1000 sampling time series with binary phase shift keying (BPSK) modulation originated by five types of satcom transmitters in the test. The established PNNs classifier implements the data testing and finally yields satisfactory accuracy at 8 dB(±1 dB) carrier to noise ratio, which indicates the feasibility of our method, and even the keen insight of its application in military. 相似文献
3.
G. Inglese 《Inverse Problems in Science & Engineering》2019,27(4):439-459
We deal with the mathematical model of the incremental degradation of the internal coating (e.g. a polymeric material) of a metallic pipe in which a fluid flows relatively fast. The fluid drags solid impurities so that longitudinal scratches, inaccessible to any direct inspection procedure, are produced on the coating. Time evolution of this kind of defects can be reconstructed from the knowledge of a sequence of temperature maps of the external surface. The time-varying orthogonal section of this damaged interface is determined as a function of time and polar angle through the identification of a suitable effective heat transfer coefficient by means of Thin Plate Approximation. 相似文献
4.
Nilesh P. Vanikar Shantipal S. Ohol Saeede Goldar 《International Journal of Cast Metals Research》2018,31(4):249-259
Bottom pour ladles with stopper rod systems are commonly used in the metal casting industry. However, stopper rod bottom-pouring systems have not yet been developed for the lower thermal masses of alloys typically used in the investment casting industry. Large thermal masses used with bottom pour systems are typically limited for ladles larger than 700 kg and to certain alloys with higher fluidity and longer solidification time like cast iron, aluminum alloys etc. In this study, bottom pour ladle designs and low thermal mass refractory systems have been developed and evaluated in production investment foundry trials with 300 kg pouring ladle. The ladles system and pouring practices used will be described along with the results from the pouring trials for SS304 that represents typical alloys used in Investment casting industries. Optimization of the variables used in an experimentation using Genetic algorithm is also explained. 相似文献
5.
采用四组分法从辽河减压渣油中分离出胶质、沥青质,分别考察了它们在分散型催化剂作用下的临氢热反应行为。结果表明,胶质、沥青质一方面要裂化生成较轻的产物;另一方面也要发生缩合反应生成较重的反应产物以及甲苯不溶物。渣油在临氢热反应过程中,沥青质是生焦的主要来源,其次才是胶质。比较了热反应生成的沥青质与原生沥青质之间以及热反应生成的胶质与原生胶质之间化学组成的区别,结果表明,反应生成的沥青质和胶质较原生的沥青质和胶质分子结构缩合程度高,并且反应苛刻度越高,缩合程度也越高。 相似文献
6.
7.
8.
600 A IGBT开关电路及其散热系统设计 总被引:1,自引:0,他引:1
采用IGBT开关电路,对大功率电阻带进行直流脉宽调制控制,实现了内燃机车大功率直流发电机负载实验中的负载大小的连续调节。为了避免在实验过程中IGBT器件的温度过高,采用独特的双管IGBT结构和双向强迫风冷的散热系统。实验表明该电路运行稳定、可靠。 相似文献
9.
10.
通过氟塑料-石墨板式换热器在化纤生产中高温强腐蚀换热工况中的实际应用,并与常规换热器的使用情况的对比分析,阐述了这种新型换热设备的特点。 相似文献