全文获取类型
收费全文 | 25093篇 |
免费 | 2652篇 |
国内免费 | 1540篇 |
专业分类
电工技术 | 3472篇 |
综合类 | 2914篇 |
化学工业 | 2078篇 |
金属工艺 | 728篇 |
机械仪表 | 2117篇 |
建筑科学 | 2145篇 |
矿业工程 | 938篇 |
能源动力 | 1427篇 |
轻工业 | 1735篇 |
水利工程 | 754篇 |
石油天然气 | 1157篇 |
武器工业 | 287篇 |
无线电 | 1801篇 |
一般工业技术 | 2032篇 |
冶金工业 | 857篇 |
原子能技术 | 182篇 |
自动化技术 | 4661篇 |
出版年
2024年 | 93篇 |
2023年 | 283篇 |
2022年 | 573篇 |
2021年 | 712篇 |
2020年 | 786篇 |
2019年 | 623篇 |
2018年 | 614篇 |
2017年 | 759篇 |
2016年 | 930篇 |
2015年 | 987篇 |
2014年 | 1543篇 |
2013年 | 1576篇 |
2012年 | 1825篇 |
2011年 | 2100篇 |
2010年 | 1484篇 |
2009年 | 1442篇 |
2008年 | 1437篇 |
2007年 | 1777篇 |
2006年 | 1495篇 |
2005年 | 1338篇 |
2004年 | 1083篇 |
2003年 | 970篇 |
2002年 | 831篇 |
2001年 | 689篇 |
2000年 | 627篇 |
1999年 | 475篇 |
1998年 | 402篇 |
1997年 | 303篇 |
1996年 | 261篇 |
1995年 | 234篇 |
1994年 | 209篇 |
1993年 | 146篇 |
1992年 | 138篇 |
1991年 | 99篇 |
1990年 | 79篇 |
1989年 | 60篇 |
1988年 | 63篇 |
1987年 | 33篇 |
1986年 | 22篇 |
1985年 | 23篇 |
1984年 | 18篇 |
1983年 | 17篇 |
1982年 | 17篇 |
1981年 | 7篇 |
1980年 | 9篇 |
1979年 | 11篇 |
1964年 | 9篇 |
1962年 | 7篇 |
1958年 | 6篇 |
1957年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
基于有线电视网络平台视频点播技术的实现 总被引:1,自引:1,他引:0
通过对有线电视网络的频带划分、拓扑结构的介绍以及真视频点播 (T -VOD)技术对通信网络要求的分析 ,深入剖析T -VOD技术在有线电视网上的实现策略 ;另外通过对T -VOD系统以及N -VOD系统典型实现的体系结构和性能特点的分析 ,全面地总结了有线电视网上视频点播技术的实现方案 ,并最终提出有线电视网上实现双向数字业务的一种构想 相似文献
112.
The main problems in estimating the uncertainty due to the presence of impurities in the material: the absence in the documents of a unique definition of the quantity being measured – the fixed point temperature, the lack of agreed methods of realizing the fixed points and the insufficient justification of the equations used for the estimate, are analyzed. The results of a measurement of the melting point of gallium are presented, which differ in the conditions in which they were realized – with one and two liquid-solid interfaces and different solidification conditions, are presented. The reasons for the considerable difference between the values of the temperatures obtained in these experiments are discussed. 相似文献
113.
114.
Hakan Boyaci 《Sadhana》2006,31(1):1-8
A simply supported damped Euler-Bernoulli beam with immovable end conditions are considered. The concept of non-ideal boundary
conditions is applied to the beam problem. In accordance, the boundaries are assumed to allow small deflections and moments.
Approximate analytical solution of the problem is found using the method of multiple scales, a perturbation technique. 相似文献
115.
变权组合预测模型在大坝安全监测中的应用 总被引:1,自引:1,他引:0
简要介绍了组合预测模型的基本原理,该模型改进了单一模型考虑因素的片面性,但常规的组合预测模型的权系数是固定的。考虑到各种模型的预测精度的变化,以及大坝安全监测数据存在的突变、时效等因素,固定权系数的组合预测模型有待进一步改进。文中提出了变权系数组合预测模型,并将其用于实际的大坝安全监测工程。结果表明,变权组合预测模型的预报精度高于其他模型。是一种值得推广的方法。 相似文献
116.
117.
ABSTRACT: We evaluated the effect of growth environment on morphology and fatty acid (FA) profiles of 2 strains of C ampylobacter jejuni (ATCC 29428 and 33560) grown under various gaseous conditions. Viable counts were determined by plate count and percentages of coccoid cells. FA profiles were measured by gas chromatography. Plate counts were lowest when cultures were grown in air and highest in CO2 (10%), O2 (5%), and N2 (85%). For 29428, percentages of coccoid cells did not differ among treatments. For 33560, percentages of coccoid cells were greater than for 29428 and varied among treatments (13% to 87%). There were no significant ( P > 0.05) relationships between percentages of coccoid cells and amounts of individual or combinations of FA either between or within strains. 相似文献
118.
Sarrazin Jean-Christophe; Giraudo Marie-Dominique; Pailhous Jean; Bootsma Reinoud J. 《Canadian Metallurgical Quarterly》2004,30(3):411
In 3 experiments, the authors studied the organization of spatiotemporal information in memory. Stimuli consisted of configurations of dots, presented sequentially. The stimuli were either proportional, with interdot distances corresponding to interdot durations, or not proportional, with interdol distances not corresponding to interdot durations. After a learning phase, participants reproduced the spatial (Experiment 1), temporal (Experiment 2), or spatial and temporal (Experiment 3) characteristics of the target 60 times in succession. In the nonproportional conditions, effects of variable interdot durations or distances on the reproduction of, respectively, constant distances (tau effect) or durations (kappa effect) were observed, whereas no such effects were observed when variable distances or durations were to be produced. Tau and kappa effects influenced the accuracy but not the variability of responses. The results are discussed in light of the distinction between properties of the stabilized mental image and the process of stabilization. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
119.
介绍龙门铣床的直流调速控制系统的改造方案,根据龙门铣床工作台运动过程及原直流电机的容量来选择交流电机和变频器并对变频器的功能进行设定。 相似文献
120.
The macroscopic deformation behavior of a fiber-reinforced aluminum-boron composite is investigated. Different periodic and random arrangements of the microstructure are considered with macroscopic hardening behavior due to the evolution of plastic zones on the microscale being taken into account.
For the solution of the initial boundary value problem, a non-standard algorithm is applied. It consists of the direct solution of the whole set of equations, treating all variables as global quantities. Together with a higher order time integration method (BDF2), an automatic step size control is used in the FEM calculations. 相似文献