全文获取类型
收费全文 | 42912篇 |
免费 | 6318篇 |
国内免费 | 4596篇 |
专业分类
电工技术 | 4768篇 |
技术理论 | 1篇 |
综合类 | 5811篇 |
化学工业 | 3441篇 |
金属工艺 | 1813篇 |
机械仪表 | 4332篇 |
建筑科学 | 5378篇 |
矿业工程 | 1764篇 |
能源动力 | 1363篇 |
轻工业 | 946篇 |
水利工程 | 1712篇 |
石油天然气 | 1383篇 |
武器工业 | 970篇 |
无线电 | 3545篇 |
一般工业技术 | 5014篇 |
冶金工业 | 1144篇 |
原子能技术 | 206篇 |
自动化技术 | 10235篇 |
出版年
2024年 | 300篇 |
2023年 | 771篇 |
2022年 | 1348篇 |
2021年 | 1456篇 |
2020年 | 1613篇 |
2019年 | 1329篇 |
2018年 | 1363篇 |
2017年 | 1670篇 |
2016年 | 1954篇 |
2015年 | 2003篇 |
2014年 | 2746篇 |
2013年 | 2741篇 |
2012年 | 3543篇 |
2011年 | 3447篇 |
2010年 | 2736篇 |
2009年 | 2719篇 |
2008年 | 2665篇 |
2007年 | 3204篇 |
2006年 | 2760篇 |
2005年 | 2286篇 |
2004年 | 1821篇 |
2003年 | 1525篇 |
2002年 | 1253篇 |
2001年 | 1140篇 |
2000年 | 1023篇 |
1999年 | 794篇 |
1998年 | 655篇 |
1997年 | 568篇 |
1996年 | 458篇 |
1995年 | 393篇 |
1994年 | 338篇 |
1993年 | 250篇 |
1992年 | 196篇 |
1991年 | 161篇 |
1990年 | 135篇 |
1989年 | 133篇 |
1988年 | 84篇 |
1987年 | 44篇 |
1986年 | 24篇 |
1985年 | 25篇 |
1984年 | 33篇 |
1983年 | 22篇 |
1982年 | 20篇 |
1981年 | 10篇 |
1980年 | 20篇 |
1979年 | 18篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1959年 | 4篇 |
1955年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
Stefan Kasapis 《International Journal of Food Science & Technology》2002,37(4):403-413
The structural properties of mixtures of pectin, oxidized starch and glucose syrup were investigated using small deformation dynamic oscillation. In the absence of added calcium, preparations of low methoxy pectin with glucose syrup formed viscous solutions, which remained crystal-free at subzero temperatures. Samples of oxidized starch and glucose syrup, on the other hand, exhibited solid-like behaviour because of the crystalline nature of the amylose-like helices. Mixtures of the two polysaccharides with the co-solute clearly showed phase inversion from liquid to solid-like behaviour with increasing amounts of starch in the formulation. The transformation was reflected in the textural properties of samples, which varied from thick solutions to firm gels. The viscoelasticity of the system was modified further by the introduction of high methoxy pectin. Preparations of high methoxy pectin and glucose syrup formed rubbery gels whose amorphous nature underwent a glass transition during cooling. 相似文献
43.
Shu-Chu Ren Nelson N. Hsu Donald G. Eitzen 《Journal of research of the National Institute of Standards and Technology》2002,107(5):445-473
Pulsed ultrasonic techniques can be and have been used to examine the interface conditions of a bonded structure. To provide a theoretical basis for such testing techniques we model the structure as a layer on top of a half-space, both of different elastic properties, with various interface bonding conditions. The exact dynamic Green’s tensor for such a structure is explicitly derived from the three-dimensional equations of motion. The final solution is a series. Each term of the series corresponds to a successive arrival of a “generalized ray” and each is a definite line integral along a fixed path which can be easily computed numerically. Willis’ method is used in the derivation. A new scheme of automatic generation of the arrivals and ray paths using combinatorial analysis, along with the summation of the corresponding products of reflection coefficients is presented. A FORTRAN code is developed for computation of the Green’s tensor when both the source and the detector are located on the top surface. The Green’s tensor is then used to simulate displacements due to pulsed ultrasonic point sources of known time waveform. Results show that the interface bonding conditions have a great influence on the transient displacements. For example, when the interface bonding conditions vary, some of the first few head waves and regular reflected rays change polarities and amplitudes. This phenomenon can be used to infer the quality of the interface bond of materials in ultrasonic nondestructive evaluation. In addition the results are useful in the study of acoustic microscopy probes, coatings, and geo-exploration. 相似文献
44.
动态光散射法研究海藻酸钠凝胶松弛行为 总被引:5,自引:0,他引:5
在前文的基础上,用相关函数轮廓分析的方法剖析了运动模型模式的复杂性。通过海藻酸钠水溶液在0.1mol/LCaCl2水溶液透析凝胶化过程中交联网络的松弛时间谱表明它不是单一的峰,有两上特征运动模式,并随透析向更慢的运动模式发展,这很慢的运动模式估计与区域的结构的生成有关。 相似文献
45.
热释电系数的测量方法 总被引:2,自引:0,他引:2
描述热释电系数的两种测量方法。其一为电荷积分法,测试系统简单,测量数据准确,且能满足零电场条件下的测量。其二为动态电流法,采用调制热源技术,研究在特定温度条件下热释电材料的动态热释电响应。 相似文献
46.
47.
48.
Aggregates of carbon black (CB) in a polymer matrix have a tendency to form a CB network. The dynamic mechanical properties of binary systems of chlorinated polyethylene (CPE) and CB or 3,9‐bis{1,1‐dimethyl‐2[β‐(3‐tert‐butyl‐4‐hydroxy‐5‐methylphenyl)propionyloxy]ethyl}‐2,4,8,10‐tetraoxaspiro[5,5]‐undecane (AO‐80) and their ternary systems were investigated. It was found that the dynamic mechanical properties of those systems depend on the colloidal properties, surface oxides, and surface modification of CB. For binary systems of CPE and CB, oxidized CB gives a high modulus at low strain amplitude and a large Payne effect compared with untreated CB. In contrast, the reverse effect was observed for their ternary systems. Consequently, a good micro‐dispersion is obtainable by surface modification due to physical adsorption of AO‐80 on oxidized CB particles via hydrogen bonds. © 2003 Society of Chemical Industry 相似文献
49.
本文为了克服精馏塔静态仿真不易收敛和初值难以给定等难题,巧妙地利用隐含数值积分方法的特点,将稳态与动态数学模型耦合起来,用以求解高难度的非理想精馏塔静态仿真问题。所得静动态混俣模型大大提高了精馏塔静态仿真的鲁棒性,对于高度非理想精馏塔的仿真尤为有效。通过对某丙烯腈萃取精馏塔的静态仿真,充分证明了这种混合模型化方法的可行性。 相似文献
50.
预测控制算法的统一格式及其在电加热炉的应用 总被引:4,自引:0,他引:4
本文根据常用的两类预测控制算法推出一种新型预测控制算法。并将其应用于一双输入/双输出的力学持久机电加热炉的温度控制系统上,获得了满意的结果:控温精度为±1.5℃/300℃,且适用于非最小相位系统。 相似文献