全文获取类型
收费全文 | 63429篇 |
免费 | 8773篇 |
国内免费 | 6034篇 |
专业分类
电工技术 | 6964篇 |
技术理论 | 1篇 |
综合类 | 8485篇 |
化学工业 | 3846篇 |
金属工艺 | 2639篇 |
机械仪表 | 7778篇 |
建筑科学 | 6218篇 |
矿业工程 | 2384篇 |
能源动力 | 1660篇 |
轻工业 | 1230篇 |
水利工程 | 2046篇 |
石油天然气 | 1755篇 |
武器工业 | 1547篇 |
无线电 | 7841篇 |
一般工业技术 | 6997篇 |
冶金工业 | 1553篇 |
原子能技术 | 374篇 |
自动化技术 | 14918篇 |
出版年
2024年 | 390篇 |
2023年 | 1030篇 |
2022年 | 1844篇 |
2021年 | 1977篇 |
2020年 | 2255篇 |
2019年 | 1821篇 |
2018年 | 1884篇 |
2017年 | 2381篇 |
2016年 | 2804篇 |
2015年 | 2943篇 |
2014年 | 4006篇 |
2013年 | 3896篇 |
2012年 | 5153篇 |
2011年 | 5027篇 |
2010年 | 3921篇 |
2009年 | 3974篇 |
2008年 | 3890篇 |
2007年 | 4724篇 |
2006年 | 4111篇 |
2005年 | 3381篇 |
2004年 | 2691篇 |
2003年 | 2343篇 |
2002年 | 1908篇 |
2001年 | 1727篇 |
2000年 | 1534篇 |
1999年 | 1176篇 |
1998年 | 949篇 |
1997年 | 848篇 |
1996年 | 702篇 |
1995年 | 603篇 |
1994年 | 517篇 |
1993年 | 374篇 |
1992年 | 287篇 |
1991年 | 238篇 |
1990年 | 192篇 |
1989年 | 202篇 |
1988年 | 133篇 |
1987年 | 70篇 |
1986年 | 34篇 |
1985年 | 41篇 |
1984年 | 48篇 |
1983年 | 31篇 |
1982年 | 29篇 |
1981年 | 24篇 |
1980年 | 30篇 |
1979年 | 23篇 |
1978年 | 8篇 |
1977年 | 14篇 |
1959年 | 6篇 |
1955年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
We analyze specific features of the design of equipment used for mechanical testing of sheet structural materials under the conditions of biaxial static, cyclic, or dynamic loading. We propose original solutions of the problems related to the fatigue testing of crosslike specimens performed without using complex hydraulic systems and their dynamic testing carried out by using very simple testing machines for uniaxial tension–compression. 相似文献
42.
硫化胶交联结构及其性能 总被引:3,自引:0,他引:3
综合讨论了聚合物/聚合物之间的交联结构及聚合物/填料之间的偶联结构对硫化胶抗硫化返牟性,抗氧老化性及动态疲劳性能的影响。 相似文献
43.
本文级出了在PC机上对一个自己开发CNC系统插祉和轴伺服控制进行仿真的结果。它包含按插补原理对直线、圆和渐开线的插补以及对轴伺服控制中的位置环和前馈控制的仿真。轴伺服马达通过一个二阶连续系统模型来仿真,最后得出对伺服进行前馈控制补偿可显著改善系统的输出。 相似文献
44.
45.
46.
47.
Let us consider n data measurements of a univariate process that have been altered by random errors. We assume that an underlying model function has a substantially smaller number of turning points than the observed ones. We propose algorithms that make least the sum of the moduli of the errors by requiring k monotonic sections, alternately increasing and decreasing, in the sequence of the smoothed values. The main difficulty in this calculation is that the optimal positions of the joins of the monotonic sections have to be found automatically among so many combinations that it is impossible to test each one separately. Moreover, the calculation seems to be very intractable to general optimization techniques because O(nk ) local minima can occur. It is shown that dynamic programming can be used for separating the data into optimal disjoint sections of adjacent data, where each section requires a single L1 monotonic calculation. This procedure is highly efficient, requiring at most O(kn2 ) computer operations and O(n) best L1 monotonic calculations to subranges of data for a global minimum. 相似文献
48.
The crystallization of poly(phenylene sulfide) (PPS) in a polymer–magnetic Nd—Fe—B powder suspension was studied. Isothermal crystallization behavior was analyzed by way of differential scanning calorimetry, and the kinetics were described via the Avrami equation. The Avrami parameters and the crystallization times were strongly affected by both the particle size and the presence of a coupling agent coated on the filler particles. The small Nd—Fe—B particles exhibited long induction and half‐times, whereas the large particles tended to have short crystallization times. Particles ranging from 38 to 150 μ appeared to have similar crystallization times and to have no significant change in the value of Avrami index with melt crystallization temperature. As a result of these analyses, the dynamic mechanical properties were determined to correlate the fundamental polymer crystallization characteristics and the physical properties of the PPS binder. The enhancement of the wetting of the filler to the binder was promoted through the coupling agent, as confirmed by dynamic mechanical testing performed on the samples. The storage modulus typically decreased because of the presence of the uncoated small particles. Conversely, the loss modulus was enhanced because of the presence of the coated small particles in the PPS binder. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1091–1102, 2002 相似文献
49.
采用DSC对不同分子量的聚醚酰亚胺的等温及动态热焓松弛行为进行了研究,并以KWW方程对实验数据进行了非线性拟合。结果表明,分子量对热焓松弛的影响是由高分子端基引起自由体积的差异所致。不同分子量的聚醚酰亚胺分子具有不同数量的端基,淬冷时端基数目的差异将产生不同数量的过剩自由体积,从而影响松弛热焓及松弛速率、低分子量的聚醚酰亚胺松弛相对较快,且起始热焓高,松弛的表观活化能亦较小。 相似文献
50.
This paper presents an efficient method which provides the optimal generation mix and the optimal generation construction process. The approximation method in which the dynamic programming technique and gradient method are combined is applied to determine the optimal generation mix with hydropower generation technologies. The successive approximations dynamic programming (SADP) technique, which is very suitable for high-dimensional multistage decision process problems, is used for obtaining the optimal generation construction process. The effectiveness and feasibility of the developed technique are demonstrated on a practical power system model which has five types of generation technologies including a hydropower generation technology. 相似文献