全文获取类型
收费全文 | 79316篇 |
免费 | 7401篇 |
国内免费 | 4250篇 |
专业分类
电工技术 | 4588篇 |
技术理论 | 3篇 |
综合类 | 5620篇 |
化学工业 | 12848篇 |
金属工艺 | 4647篇 |
机械仪表 | 5147篇 |
建筑科学 | 5822篇 |
矿业工程 | 2305篇 |
能源动力 | 1945篇 |
轻工业 | 7194篇 |
水利工程 | 1654篇 |
石油天然气 | 4047篇 |
武器工业 | 674篇 |
无线电 | 8930篇 |
一般工业技术 | 9279篇 |
冶金工业 | 3568篇 |
原子能技术 | 935篇 |
自动化技术 | 11761篇 |
出版年
2024年 | 394篇 |
2023年 | 1349篇 |
2022年 | 2454篇 |
2021年 | 3266篇 |
2020年 | 2568篇 |
2019年 | 2122篇 |
2018年 | 2486篇 |
2017年 | 2613篇 |
2016年 | 2496篇 |
2015年 | 3295篇 |
2014年 | 4134篇 |
2013年 | 5053篇 |
2012年 | 5632篇 |
2011年 | 6080篇 |
2010年 | 5508篇 |
2009年 | 5402篇 |
2008年 | 5132篇 |
2007年 | 4876篇 |
2006年 | 4702篇 |
2005年 | 3894篇 |
2004年 | 2701篇 |
2003年 | 2229篇 |
2002年 | 2064篇 |
2001年 | 1732篇 |
2000年 | 1505篇 |
1999年 | 1441篇 |
1998年 | 1077篇 |
1997年 | 943篇 |
1996年 | 820篇 |
1995年 | 664篇 |
1994年 | 529篇 |
1993年 | 413篇 |
1992年 | 304篇 |
1991年 | 250篇 |
1990年 | 177篇 |
1989年 | 152篇 |
1988年 | 118篇 |
1987年 | 86篇 |
1986年 | 76篇 |
1985年 | 37篇 |
1984年 | 34篇 |
1983年 | 27篇 |
1982年 | 35篇 |
1981年 | 13篇 |
1980年 | 14篇 |
1979年 | 12篇 |
1978年 | 9篇 |
1977年 | 10篇 |
1976年 | 13篇 |
1975年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
62.
Jong Min Kim Donghee Lee Sang Lyul Min Chong Sang Kim 《Information Processing Letters》2003,85(2):93-97
A new dynamic buffer allocation strategy based on the notion of marginal gains is presented for the buffer cache that is used by the operating system to store frequently accessed disk blocks in main memory, and the performance of the proposed strategy is compared with those of previous allocation strategies. In the proposed strategy, marginal gain values are predicted by exploiting functions that approximate the expected number of buffer hits per unit time. Experimental results from both trace-driven simulation and an actual implementation in the FreeBSD operating system show that the proposed strategy accurately predicts the marginal gain values for various workloads resulting in significantly improved buffer hit ratios. 相似文献
63.
Shijie Zhu Yutaka Kagawa Jian-Wu Cao Mineo Mizuno 《Metallurgical and Materials Transactions A》2004,35(9):2853-2859
Time-dependent deformation in an enhanced SiC/SiC composite has been studied under constant load at high temperatures of 1200
°C, 1300 °C, and 1400 °C. Creep damage evolution was evaluated by a Young’s-modulus change of partial unloading and microscopic
observation. The addition of the glassy phase in the matrix is very effective for protecting the composite from oxidation.
The transient creep is dominant in creep life at all the temperatures. An empirical equation is proposed to describe creep
behavior of the composite. It is found that creep activation energy increases with creep time at stresses lower than matrix
cracking stress, but the activation energy remains constant at stresses higher than the matrix cracking stress. The creep
strain rate of the composite is considered to be controlled by creep of fibers based on examining the time, strain, stress,
and temperature dependencies of creep strain rates. 相似文献
64.
65.
V. S. Bessmertnyi N. I. Min’ko P. S. Dyumina V. P. Krokhin S. V. Semenenko M. A. Lipko 《Glass and Ceramics》2005,62(11-12):386-387
A technology for the synthesis of synthetic minerals (using the example of spinels) using a low-temperature plasma flame is developed. The diagnostic properties of spinels are identified. 相似文献
66.
浅析包装中色彩运用的文化原则 总被引:1,自引:0,他引:1
从某种程度上讲,包装是对产品的一种定位和阐释。心理学有关研究表明,人的视觉器官,在观察物体时,最初的20秒内色彩感觉占80%,而形体感觉占20%:两分钟后色彩占60%,形体占40%;5分钟后各占一半,并且这种状态将继续保持。可见,包装给人的印象多么迅速、深刻、持久。国外学者曾有过一项研究,发现由广告媒体招徕的顾客中,有33%的人在销售现场会选择包装吸引人的品牌,包装重要性不言而喻。可以说,包装的素材、形式和色彩等因素综合在一起,将产品引伸至一个深层的文化氛围。 相似文献
67.
Aroused problems in the deposition of diamond-like carbon films by using the liquid phase electrodeposition technique 总被引:2,自引:0,他引:2
He-Sun Zhu Jin-Ting Jiu Qiang Fu Hao Wang Chuan-Bao Cao 《Journal of Materials Science》2003,38(1):141-145
Hydrogenated diamond-like carbon (DLC) films were prepared by using liquid phase electrodeposition technique. The effects of the applied potential and the carbon sources on the deposition process and film structures were studied. It has been found that the organic liquids with high dielectric constants, small viscosities and the methyl group bonding to the polar group are appropriate carbon sources. The increasing of potential improves the formation of sp3 carbon during the deposition process. In a high electric field, organic molecules are polarized and reacted on the surface of the electrode, turning out DLC and other products. It is believed that the reaction follows a polarization-reaction mechanism. 相似文献
68.
69.
对甲基丙烯酸三氟乙酰氧乙酯(TFAOEMA)的阴离子聚合及原予转移自由基聚合进行了研究。常用的阴离于引发剂如丁基锂、1,1-二苯基已基锂等很难引发TFAOEMA的阴离子聚合,而碱性较弱的引发剂如三乙基铝却容易引发,且产率较高。以氯化亚铜、五甲基二乙基三胺、溴代丙酸乙酯为引发体系的TFAOEMA的本体原子转移自由基聚合符合活性聚合特征。但在四氢呋喃为溶剂的原子转移自由基聚合中却存在活性中心失活现象。以末端含卤素的聚甲基丙烯酸甲酯为大分子引发剂,引发TFAOEMA的原子转移自由基聚合,得到了含氟双嵌段聚合物。 相似文献
70.
J. C. Clark G. G. Ihas M. Reghu C. O. Yoon A. J. Heeger Y. Cao 《Journal of Low Temperature Physics》1995,101(3-4):605-610
Advances in the synthesis of organic conducting polymer systems has increased the electrical conductivity of these systems by several orders of magnitude in the last decade. Several practical applications are envisioned for such systems, but a thorough understanding of the conduction mechanisms and identification of the charge carriers is lacking, making design and implementation for bulk synthesis difficult. In order to clarify our understanding of the electrical properties of these systems, the resistivity and magnetoresistivity of various polymers doped near the metal - insulator transition, such as polyaniline protonated by camphor sulfonic acid (PANi-CSA) and polypyrrole doped with PF6 (PPy-PF6), have been studied down to 25 mK in magnetic fields up to 16 T. 相似文献