全文获取类型
收费全文 | 3042篇 |
免费 | 70篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 82篇 |
综合类 | 9篇 |
化学工业 | 575篇 |
金属工艺 | 77篇 |
机械仪表 | 45篇 |
建筑科学 | 144篇 |
矿业工程 | 14篇 |
能源动力 | 34篇 |
轻工业 | 320篇 |
水利工程 | 18篇 |
石油天然气 | 5篇 |
无线电 | 235篇 |
一般工业技术 | 388篇 |
冶金工业 | 875篇 |
原子能技术 | 22篇 |
自动化技术 | 274篇 |
出版年
2020年 | 28篇 |
2019年 | 30篇 |
2018年 | 32篇 |
2017年 | 30篇 |
2016年 | 50篇 |
2015年 | 42篇 |
2014年 | 49篇 |
2013年 | 144篇 |
2012年 | 70篇 |
2011年 | 103篇 |
2010年 | 78篇 |
2009年 | 89篇 |
2008年 | 85篇 |
2007年 | 97篇 |
2006年 | 99篇 |
2005年 | 94篇 |
2004年 | 79篇 |
2003年 | 77篇 |
2002年 | 73篇 |
2001年 | 56篇 |
2000年 | 45篇 |
1999年 | 64篇 |
1998年 | 90篇 |
1997年 | 85篇 |
1996年 | 66篇 |
1995年 | 52篇 |
1994年 | 52篇 |
1993年 | 57篇 |
1992年 | 48篇 |
1991年 | 32篇 |
1990年 | 38篇 |
1989年 | 49篇 |
1988年 | 43篇 |
1987年 | 34篇 |
1986年 | 33篇 |
1985年 | 47篇 |
1984年 | 55篇 |
1983年 | 51篇 |
1982年 | 41篇 |
1981年 | 41篇 |
1980年 | 40篇 |
1979年 | 33篇 |
1978年 | 44篇 |
1977年 | 39篇 |
1976年 | 60篇 |
1975年 | 36篇 |
1974年 | 30篇 |
1972年 | 34篇 |
1971年 | 27篇 |
1966年 | 29篇 |
排序方式: 共有3117条查询结果,搜索用时 31 毫秒
1.
2.
3.
Zhao M. Shea J. D. Hagness S. C. van der Weide D. W. 《Microwave and Wireless Components Letters, IEEE》2006,16(12):675-677
We present a 3-12 GHz compact mixer-based reflectometer (CMR) and horn antenna system, and demonstrate its use in detecting backscatter signals with a free space calibration procedure. We evaluate the frequency-domain performance of the CMR-antenna system for measuring the complex reflection coefficient of a dielectric slab and compare it with that of a commercial vector network analyzer (VNA)-antenna setup. Time-domain responses are also investigated, and show the effectiveness of this calibration method. This low-cost, compact system eliminates the need for traditional mechanical standards and a VNA, is effective in reducing reflection artifacts, and allows for flexibility in the placement of reference planes; thus it is well suited for array-based imaging applications 相似文献
4.
We report for the first time optical signal-to-noise penalties which lead to performance degradations in single-fiber long-reach optical access networks when compared to identical dual-fiber systems. A simplified architecture, with reduced optical amplifier count compared to previous work, for single-fiber operation of a symmetrical 10-Gb/s, 1024-way split, 110-km long-reach optical access network is presented and demonstrated. In addition, a possible solution to remove the optical signal-to-noise penalty is suggested 相似文献
5.
We present the design of E-kernel, an embedding kernel on the Victor V256 message-passing partitionable multiprocessor, developed for the support of program mapping and network reconfiguration. E-kernel supports the embedding of a new network topology onto Victor's 2D mesh and also the embedding of a task graph onto the 2D mesh network or the reconfigured network. In the current implementation, the reconfigured network can be a line or an even-size ring, and the task graphs meshes or tori of a variety of dimensions and shapes or graphs with similar topologies. For application programs having these task graph topologies and that are designed according to the communication model of E-kernel, they can be run without any change on partitions connected by the 2D mesh, line, or ring. Further, E-kernel attempts the communication optimization of these programs on the different networks automatically, thus making both the network topology and the communication optimization attempt completely transparent to the application programs. Many of the embeddings used in E-kernel are optimal or asymptotically optimal (with respect to minimum dilation cost). The implementation of E-kernel translated some of the many theoretical results in graph embeddings into practical tools for program mapping and network reconfiguration in a parallel system. E-kernel is functional on Victor V256. Measurements of E-kernel's performance on V256 are also included 相似文献
6.
7.
8.
Hans-Jürgen Odenthal Herbert Pfeifer Ina Lemanowicz Rainer Gorissen 《Metallurgical and Materials Transactions B》2002,33(2):163-172
The present work describes quantitative digital particle image velocimetry measurements of a full-scale water model of a thin
slab mold. Different casting speeds and two submerged entry nozzles with one and two outlet ports have been investigated.
The flow pattern of the single-port nozzle shows a counterclockwise-rotating double vortex that is nearly steady-state but
leads to high stationary surface waves. The flow jets out of the two-port nozzle oscillate and produce a transient flow pattern
with low wave amplitudes. The amplitudes for the one-port nozzle show a linear variation with the volumetric flow rate. The
experimental results lead to a good interpretation of the flow phenomena and are used to validate steady-state numerical simulations
with the commercial program, CFX, on the basis of the Reynolds equations. To describe anisotropic turbulence effects, the
Reynolds stress model (RSM) is used for the flat single-port nozzle and the standard k-ɛ model for the mold flow. The calculated mean velocities and wave amplitudes, predicted from pressure distribution at the
water surface, are generally in the consensus of the experimental data.
An erratum to this article is available at . 相似文献
9.
10.
The vicissitudes of the Israeli-Palestinian peace process since 1967 are analyzed using attitudes and related concepts where relevant. The 1967 war returned the two peoples' zero-sum conflict around national identity to its origin as a conflict within the land both peoples claim. Gradually, new attitudes evolved regarding the necessity and possibility of negotiations toward a two-state solution based on mutual recognition, which became the building stones of the 1993 Oslo agreement. Lacking a commitment to a final outcome, the Oslo-based peace process was hampered by reserve options, which increased avoidance at the expense of approach tendencies as the parties moved toward a final agreement. The resulting breakdown of the process in 2000 produced clashing narratives, reflecting different anchors for judgment and classical mirror images. Public support for violence increased, even as public opinion continued to favor a negotiated two-state solution. Reviving the peace process requires mutual reassurance about the availability of a partner for negotiating a principled peace based on a historic compromise that meets the basic needs and validates the identities of both peoples. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献