全文获取类型
收费全文 | 8323篇 |
免费 | 739篇 |
国内免费 | 291篇 |
专业分类
电工技术 | 383篇 |
技术理论 | 3篇 |
综合类 | 511篇 |
化学工业 | 1562篇 |
金属工艺 | 351篇 |
机械仪表 | 472篇 |
建筑科学 | 678篇 |
矿业工程 | 267篇 |
能源动力 | 222篇 |
轻工业 | 645篇 |
水利工程 | 148篇 |
石油天然气 | 435篇 |
武器工业 | 57篇 |
无线电 | 727篇 |
一般工业技术 | 1087篇 |
冶金工业 | 610篇 |
原子能技术 | 77篇 |
自动化技术 | 1118篇 |
出版年
2024年 | 30篇 |
2023年 | 129篇 |
2022年 | 227篇 |
2021年 | 362篇 |
2020年 | 280篇 |
2019年 | 242篇 |
2018年 | 266篇 |
2017年 | 292篇 |
2016年 | 267篇 |
2015年 | 350篇 |
2014年 | 404篇 |
2013年 | 522篇 |
2012年 | 498篇 |
2011年 | 576篇 |
2010年 | 465篇 |
2009年 | 440篇 |
2008年 | 389篇 |
2007年 | 396篇 |
2006年 | 399篇 |
2005年 | 372篇 |
2004年 | 262篇 |
2003年 | 269篇 |
2002年 | 264篇 |
2001年 | 200篇 |
2000年 | 215篇 |
1999年 | 213篇 |
1998年 | 136篇 |
1997年 | 107篇 |
1996年 | 131篇 |
1995年 | 105篇 |
1994年 | 78篇 |
1993年 | 57篇 |
1992年 | 56篇 |
1991年 | 48篇 |
1990年 | 43篇 |
1989年 | 35篇 |
1988年 | 22篇 |
1987年 | 20篇 |
1986年 | 16篇 |
1985年 | 9篇 |
1984年 | 15篇 |
1983年 | 13篇 |
1982年 | 9篇 |
1981年 | 10篇 |
1979年 | 9篇 |
1978年 | 8篇 |
1975年 | 9篇 |
1974年 | 9篇 |
1972年 | 6篇 |
1970年 | 6篇 |
排序方式: 共有9353条查询结果,搜索用时 15 毫秒
111.
Han Mo Jeong Shang Hoon Lee Kwang Jae Cho Young Tae Jeong Kap Ku Kang Jae Kwon Oh 《应用聚合物科学杂志》2002,84(9):1709-1715
The block copolymer of poly(1‐hexadecene) (PHD) and polypropylene (PP) was effectively synthesized by the sequential polymerization of propylene and 1‐hexadecene by using highly isospecific TiCl3/Cp2Ti(CH3)2 (Cp = cyclopentadienyl). The block copolymers had two separate melting temperatures of constituent blocks. The modulus of PHD–PP block copolymer was enhanced as the content of sequentially polymerized PP block was increased. The elongation at break showed positive deviation at the intermediate compositions from the simple additive values of constituent homopolymers. Shape memory effect which utilizes the crystalline PHD block as a reversible phase and the crystalline PP block as a fixed structure was examined. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1709–1715, 2002; DOI 10.1002/app.10551 相似文献
112.
In addition to 2-methyl-4-heptanone, 6-methyl-5-hepten-2-one, and iridodials, the anal gland exudate of the dolichoderine ant,Tapinoma simrothi, contains 4-heptanone and 4-hydroxy-4-methyl-2-pentanone. The secretion functions as an alarm pheromone. 相似文献
113.
吴尚 《网络安全技术与应用》2014,(12):145-145
近年来,网络攻击事件时有发生,给社会和企业带来巨大威胁和损失,对于网络安全评估方法的研究成为了热点,文中介绍了网络安全评估方法的研究现状,分析了网络安全评估相关技术,进而探析了网络安全评估方法。 相似文献
114.
James Cheng Zechao Shang Hong Cheng Haixun Wang Jeffrey Xu Yu 《The VLDB Journal The International Journal on Very Large Data Bases》2014,23(2):227-252
We study the problem of answering k -hop reachability queries in a directed graph, i.e., whether there exists a directed path of length $k$ , from a source query vertex to a target query vertex in the input graph. The problem of $k$ -hop reachability is a general problem of the classic reachability (where $k=\infty $ ). Existing indexes for processing classic reachability queries, as well as for processing shortest path distance queries, are not applicable or not efficient for processing $k$ -hop reachability queries. We propose an efficient index for processing $k$ -hop reachability queries. Our experimental results on a wide range of real datasets show that our method is efficient and scalable in terms of both index construction and query processing. 相似文献
115.
A new kind of blend film was made by mixing the solutions of collagen, konjac glucommnnan (KGM), and sodium alginate. The structure of the blend film was characterized by FTIR, XRD, atomic absorption spectrophotometer, and SEM, respectively. The effects of weight ratio between the polymers on light transmittance, tensile strength, elongation at break, water permeability, and water absorption of the film were studied. The results showed that there were strong interactions and good compatibility between collagen, KGM, and sodium alginate in the film. The film possesses good mechanical properties. Therefore, it can be applied in biomedicine as a new type of biomaterial. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
116.
Helen E. Hermes Henrich Frielinghaus Wim Pyckhout-Hintzen Dieter Richter 《Polymer》2006,47(6):2147-2155
A new model is presented which can describe quantitatively the small angle neutron scattering from montmorillonite-type clay dispersions and polymer-clay nanocomposites. The model is shown to be able to describe well the data from a series of dilute montmorillonite in water dispersions in which the deuterium content of the water phase is varied. The fits combined with information from other techniques suggest strongly that H-D exchange occurs in the montmorillonite-water dispersions. Deviations from Q−2 behaviour often observed experimentally for clay dispersions are convincingly explained by the presence of a small proportion of tactoids. 相似文献
117.
118.
Xiongwei Qu Shurui Shang Guodong Liu Shengwen Zhang Yan Zhang Liucheng Zhang 《应用聚合物科学杂志》2004,91(3):1685-1697
Blends of poly(styrene‐co‐acylonitrile) (SAN) with ethylene–propylene–diene monomer (EPDM) rubber were investigated. An improved toughness–stiffness balance of the SAN/EPDM blend was obtained when an appropriate amount of acrylonitrile–EPDM–styrene (AES) graft copolymer was added, prepared by grafting EPDM with styrene–acrylonitrile copolymer, and mixed thoroughly with both of the two components of the blend. Morphological observations indicated a finer dispersion of the EPDM particles in the SAN/EPDM/AES blends, and particle size distribution became narrower with increasing amounts of AES. Meanwhile, it was found that the SAN/EPDM blend having a ratio of 82.5/17.5 by weight was more effective in increasing the impact strength than that of the 90/10 blend. From dynamic mechanic analysis of the blends, the glass‐transition temperature of the EPDM‐rich phase increased from ?53.9 to ?46.2°C, even ?32.0°C, for the ratio of 82.5/17.5 blend of SAN/EPDM, whereas that of the SAN‐rich phase decreased from 109.2 to 108.6 and 107.5°C with the additions of 6 and 10% AES copolymer contents, respectively. It was confirmed that AES graft copolymer is an efficient compatibilizer for SAN/EPDM blend. The compatibilizer plays an important role in connecting two phases and improving the stress transfer in the blends. Certain morphological features such as thin filament connecting and even networking of the dispersed rubber phase may contribute to the overall ductility of the high impact strength of the studied blends. Moreover, its potential to induce a brittle–ductile transition of the glassy SAN matrix is considered to explain the toughening mechanism. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1685–1697, 2004 相似文献
119.
120.
目的 针对全球大场景渲染中单精度浮点数的低精度导致的图像抖动和撕裂问题,提出了一套完整的解决方法。方法 首先,使用全球四叉树结构来寻找新的坐标原点,避免了现有算法需要频繁切换世界坐标原点的缺点;其次,在新坐标系下进行坐标转换和矩阵转换,解决了像素坐标计算的误差导致的抖动问题;最后,在GPU中使用基于对数的深度计算方式来提高深度的分辨率,解决了深度计算误差导致的Z-Fighting现象。结果 实验结果表明所提方法能很好的解决单精度浮点导致的渲染问题。结论 此方法具有适应性强、实现复杂度低、精度和效率可控等优点。 相似文献