全文获取类型
收费全文 | 96145篇 |
免费 | 9562篇 |
国内免费 | 5706篇 |
专业分类
电工技术 | 6274篇 |
技术理论 | 6篇 |
综合类 | 7904篇 |
化学工业 | 14878篇 |
金属工艺 | 5441篇 |
机械仪表 | 6012篇 |
建筑科学 | 6946篇 |
矿业工程 | 2620篇 |
能源动力 | 2682篇 |
轻工业 | 10517篇 |
水利工程 | 2304篇 |
石油天然气 | 3985篇 |
武器工业 | 863篇 |
无线电 | 11418篇 |
一般工业技术 | 10890篇 |
冶金工业 | 3773篇 |
原子能技术 | 1038篇 |
自动化技术 | 13862篇 |
出版年
2024年 | 575篇 |
2023年 | 1814篇 |
2022年 | 3501篇 |
2021年 | 4612篇 |
2020年 | 3616篇 |
2019年 | 2722篇 |
2018年 | 3043篇 |
2017年 | 3371篇 |
2016年 | 3123篇 |
2015年 | 4407篇 |
2014年 | 5582篇 |
2013年 | 6557篇 |
2012年 | 7397篇 |
2011年 | 8000篇 |
2010年 | 7073篇 |
2009年 | 6566篇 |
2008年 | 6429篇 |
2007年 | 5798篇 |
2006年 | 5219篇 |
2005年 | 4212篇 |
2004年 | 3019篇 |
2003年 | 2585篇 |
2002年 | 2576篇 |
2001年 | 2183篇 |
2000年 | 1569篇 |
1999年 | 1343篇 |
1998年 | 920篇 |
1997年 | 721篇 |
1996年 | 667篇 |
1995年 | 483篇 |
1994年 | 388篇 |
1993年 | 275篇 |
1992年 | 245篇 |
1991年 | 163篇 |
1990年 | 134篇 |
1989年 | 113篇 |
1988年 | 74篇 |
1987年 | 58篇 |
1986年 | 54篇 |
1985年 | 29篇 |
1984年 | 25篇 |
1983年 | 20篇 |
1982年 | 22篇 |
1981年 | 25篇 |
1980年 | 30篇 |
1979年 | 16篇 |
1977年 | 8篇 |
1976年 | 10篇 |
1959年 | 8篇 |
1951年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
This paper addresses the problem of power control in a multihop wireless network supporting multicast traffic. We face the problem of forwarding packet traffic to multicast group members while meeting constraints on the signal-to-interference-plus-noise ratio (SINR) at the intended receivers. First, we present a distributed algorithm which, given the set of multicast senders and their corresponding receivers, provides an optimal solution when it exists, which minimizes the total transmit power. When no optimal solution can be found for the given set of multicast senders and receivers, we introduce a distributed, joint scheduling and power control algorithm which eliminates the weak connections and tries to maximize the number of successful multicast transmissions. The algorithm allows the other senders to solve the power control problem and minimize the total transmit power. We show that our distributed algorithm converges to the optimal solution when it exists, and performs close to centralized, heuristic algorithms that have been proposed to address the joint scheduling and power control problem. 相似文献
12.
To determine three‐dimensional fiber orientation states in injection‐molded short‐fiber composites, a confocal laser scanning microscope (CLSM) is used. Since the CLSM optically sections the specimen, more than two images of the cross sections on and below the surface of the composite can be obtained. Three‐dimensional fiber orientation states can be determined by using geometric parameters of fiber images obtained from two parallel cross sections. For experiments, carbon‐fiber‐reinforced polystyrene is examined by the CLSM and geometric parameters of fibers on each cross‐sectional plane are measured by an image analysis. In order to describe fiber orientation states compactly, orientation tensors are determined at different positions of the prepared specimen. Three‐dimensional orientation states are obtained without any difficulty by determining the out‐of‐plane angles utilizing fiber images on two parallel planes acquired by the CLSM. Orientation states are different at different positions and show the shell–core structure along the thickness of the specimen. Fiber orientation tensors are predicted by a numerical analysis and the numerically predicted orientation states show good agreement with measured ones. However, some differences are found at the end of cavity. They may result from the fountain flow effects, which are not considered in the numerical analysis. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 500–509, 2003 相似文献
13.
14.
国际上许多标准化组织都在对自动交换光网络的相关技术和标准规范进行研究。本文介绍了ITU-T、IETF和OIF等几个主要的标准化组织在自动交换光网络标准方面的进展情况。 相似文献
15.
Ki Hyun Kim Yong Hoon Kang Byoungho Lee 《Photonics Technology Letters, IEEE》1997,9(12):1610-1612
A photorefractive volume hologram was recorded and probed using light diffracted from a tapered optical fiber as a reference beam. A single-mode fiber (SMF) was chemically etched and tapered to give a complicated beam pattern, and it is shown that the tapered optical fiber can be utilized to increase the storage density of the volume hologram. Spatial selectivity of the volume hologram with this method was increased by two times compared to the normal SMF referencing, which is due to the fact that the complicated beam pattern has little correlation with its shifted version 相似文献
16.
禹门口提水工程干渠上的十几座大型钢筋混凝土渡槽采用现浇混凝土施工方案。经过十几座渡槽的施工及通水检验,证明现浇施工技术与工艺已经成熟。本文就施工中遇到的高大排架外形与垂直度控制、槽身模板制做与固定、模具的空中支撑、运输与入仓办法等做以简单介绍。 相似文献
17.
This article deals with the kinetics of two-step anionic polymerization by way of a non-steady state method. Several molecular parameters can be evaluated using the formulae developed. A bimodal molecular weight distribution function for the resulting polymer is derived from the set of kinetic differential equations, which is in agreement with the experimental data reported. 相似文献
18.
19.
本文提出一种关于DMT系统传输纯数据流业务的最佳的功率分配算法,该算法使用了一种有效的表格查手工艺工和拉格朗日乘法器对分搜索办法,能够较快的收敛到最佳的功率点。同时,易于用硬件和软件实现。 相似文献
20.