全文获取类型
收费全文 | 41688篇 |
免费 | 5886篇 |
国内免费 | 5367篇 |
专业分类
化学 | 23617篇 |
晶体学 | 430篇 |
力学 | 1720篇 |
综合类 | 342篇 |
数学 | 3342篇 |
物理学 | 10333篇 |
无线电 | 13157篇 |
出版年
2024年 | 156篇 |
2023年 | 870篇 |
2022年 | 1229篇 |
2021年 | 1499篇 |
2020年 | 1437篇 |
2019年 | 1485篇 |
2018年 | 1223篇 |
2017年 | 1325篇 |
2016年 | 1659篇 |
2015年 | 1879篇 |
2014年 | 2402篇 |
2013年 | 2962篇 |
2012年 | 3429篇 |
2011年 | 3569篇 |
2010年 | 2711篇 |
2009年 | 2588篇 |
2008年 | 2954篇 |
2007年 | 2649篇 |
2006年 | 2485篇 |
2005年 | 2084篇 |
2004年 | 1586篇 |
2003年 | 1405篇 |
2002年 | 1375篇 |
2001年 | 1199篇 |
2000年 | 952篇 |
1999年 | 851篇 |
1998年 | 681篇 |
1997年 | 566篇 |
1996年 | 584篇 |
1995年 | 473篇 |
1994年 | 385篇 |
1993年 | 292篇 |
1992年 | 287篇 |
1991年 | 272篇 |
1990年 | 222篇 |
1989年 | 172篇 |
1988年 | 144篇 |
1987年 | 101篇 |
1986年 | 127篇 |
1985年 | 99篇 |
1984年 | 81篇 |
1983年 | 64篇 |
1982年 | 44篇 |
1981年 | 39篇 |
1980年 | 35篇 |
1978年 | 26篇 |
1977年 | 27篇 |
1976年 | 29篇 |
1974年 | 29篇 |
1973年 | 31篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
Ching-Hsue Cheng 《Microelectronics Reliability》1994,34(12)
In this paper, we propose a new method to analyze fuzzy consecutive-k-out-of-n:F system reliability using fuzzy GERT. The triangular fuzzy numbers are used to fuzzify probabilities of the consecutive-k-out-of-n:F system and the interval arithmetic, α-cuts and an index of optimism λ are applied to compute fuzzy consecutive-k-out-of-n:F system reliability on fuzzy the GERT network. Futhermore, we can obtain all computation results by “MATHEMATICA” package. 相似文献
82.
Ying Wang Chaudhuri S.K. Safavi-Naeini S. 《Antennas and Propagation, IEEE Transactions on》2002,50(11):1598-1604
A novel method of studying wave penetration through inhomogeneous walls using the hybrid technique based on combining finite-difference time-domain (FDTD) and ray tracing methods is presented . The FDTD method is used to analyze the transmission characteristics of inhomogeneous walls. Using the knowledge of the tangential electric and magnetic field distributions along the borders of the FDTD computation domain, rays are sent out to cover the rest of the environment so that prediction of signal coverage can be made more efficiently without compromising the accuracy. Numerical results of the method have been compared and shown to agree very well with those of measurement and those of full wave analysis. Examples have shown the inadequacy of the traditional ray tracing method in the presence of walls made of concrete blocks. However, the proposed method can accurately predict signal coverage by taking into account the scattered fields by the inhomogeneity inside the walls. The method does not add much to computational complexity. Reduction in computation time is even more significant when the incident waves can be approximated to be plane waves and the wall structure is periodic. 相似文献
83.
84.
85.
86.
87.
88.
89.
Compact miniaturized hairpin resonators are used to design cross-coupled filters with a dual-passband response of elliptic function type. The hairpin resonators are treated as a stepped impedance resonator (SIR) in analysis. In a filter, two different hairpin resonators are used to establish proper couplings required for the two design frequencies. Two filters are fabricated and measured. The results show a good agreement with the simulation. 相似文献
90.
本文讨论了温度、相变、应力间的耦合关系,给出了铸坯在考虑相变时的热弹塑性蠕变的本构关系,以及计算铸坯内应力的有限元迭代公式。 相似文献