全文获取类型
收费全文 | 20000篇 |
免费 | 2291篇 |
国内免费 | 1298篇 |
专业分类
电工技术 | 2746篇 |
综合类 | 2558篇 |
化学工业 | 1377篇 |
金属工艺 | 809篇 |
机械仪表 | 1706篇 |
建筑科学 | 2372篇 |
矿业工程 | 972篇 |
能源动力 | 963篇 |
轻工业 | 1427篇 |
水利工程 | 763篇 |
石油天然气 | 1283篇 |
武器工业 | 430篇 |
无线电 | 1781篇 |
一般工业技术 | 1550篇 |
冶金工业 | 785篇 |
原子能技术 | 318篇 |
自动化技术 | 1749篇 |
出版年
2024年 | 94篇 |
2023年 | 269篇 |
2022年 | 520篇 |
2021年 | 615篇 |
2020年 | 620篇 |
2019年 | 546篇 |
2018年 | 515篇 |
2017年 | 697篇 |
2016年 | 696篇 |
2015年 | 731篇 |
2014年 | 1095篇 |
2013年 | 1043篇 |
2012年 | 1421篇 |
2011年 | 1602篇 |
2010年 | 1176篇 |
2009年 | 1298篇 |
2008年 | 1219篇 |
2007年 | 1656篇 |
2006年 | 1443篇 |
2005年 | 1131篇 |
2004年 | 915篇 |
2003年 | 769篇 |
2002年 | 607篇 |
2001年 | 544篇 |
2000年 | 473篇 |
1999年 | 339篇 |
1998年 | 272篇 |
1997年 | 266篇 |
1996年 | 213篇 |
1995年 | 177篇 |
1994年 | 140篇 |
1993年 | 109篇 |
1992年 | 104篇 |
1991年 | 70篇 |
1990年 | 36篇 |
1989年 | 49篇 |
1988年 | 36篇 |
1987年 | 14篇 |
1986年 | 12篇 |
1984年 | 9篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 11篇 |
1977年 | 2篇 |
1964年 | 3篇 |
1959年 | 6篇 |
1955年 | 1篇 |
1954年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
E. Stenitzer H. Diestel Th. Zenker R. Schwartengräber 《Water Resources Management》2007,21(9):1567-1584
The performance of the water balance and crop growth model SIMWASER to estimate the water supply of a lawn by capillary rise
from shallow ground water was investigated by using lysimeter measurements with a sandy and a clayey soil. Moreover the robustness
of the model was evaluated by running it either with measured hydraulic soil parameters or with estimated pedotransfer functions
(PTFs) derived from texture and bulk density. Simulations were performed for the years 1996–1998 with input data from the
lysimeter station Berlin-Dahlem (Germany) for lysimeters containing undisturbed sandy or clayey soil monoliths, with groundwater
at 135 cm depth. Simulated evapotranspiration and percolation/capillary rise were in good agreement with the measured data
for all variants, while simulated soil water storage was acceptable only for the variants using hydraulic soil data based
on laboratory measurements or using PTFs derived from known soil class and bulk density. PTFs based on mean total pore volume
of the respective soil classes yielded soil water storages which were evidently too high; therefore they should be used with
care and must be avoided at all in simulating the soil water balance of arid sites with shallow groundwater. 相似文献
52.
Power devices with high capability have been developed. 8‐kV/3.5‐kA‐class light‐triggered thyristors have the highest capability among power devices. These devices are used in the Kii Channel HVDC transmission system in Japan. In this paper, we report the extracted problems of conventional testing methods of 8‐kV/3.5‐kA‐class light‐triggered thyristors among manufacturers, and the proposed unified testing methods on the basis of element characteristics and operating conditions in the Kii Channel HVDC system. Furthermore, we propose a figure of merit for power devices for the practical use, and try to extract elements used at the Kii Channel HVDC system with small margins and low withstand capabilities. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 140(3): 61–70, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10024 相似文献
53.
MV2000T智能变送器 总被引:1,自引:0,他引:1
较全面地介绍了ABB公司MV2 0 0 0T智能变送器的市场开发背景、工作原理、技术规格、性能特点及设计选型要点 相似文献
54.
In this paper, we consider the classical equations of the positive real lemma under the sole assumption that the state matrix A has unmixed spectrum: σ(A)∩σ(−A)=. Without any other system-theoretic assumption (observability, reachability, stability, etc.), we derive a necessary and sufficient condition for the solvability of the positive real lemma equations. 相似文献
55.
石英砂脱水性能的研究 总被引:1,自引:0,他引:1
通过大量试验结果 ,研究了各种粒度范围的石英砂的脱水性能 ,包括沉降特性、过滤性能、极限压缩浓度等 ,为进行此类产品的固液分离提供了重要的参考数据 相似文献
56.
Xin'an LIANG 《材料科学技术学报》2002,18(1):95-96
Skeletal form of KnbO3 crystals growing in Li2B4O7 solvent was in-situ observed at 900℃ and it was found that shallow depression started to develop on the surface of KnbO3 crystals when the crystal size exceeded several micron,typically 7 micron.Based on the quantitative criterion derived by Chernov,the estimated critical size of KNbO3 crystals was 1 micron,which was consistent with the experimental measurement.The kinetic coefficients,Kcorner and Kcr,in the criterion were experimentally obtained in the diffusive-convective and diffusive-advective flow states respectively. 相似文献
57.
A method based on cluster analysis techniques is proposed in order to obtain representative local wind patterns. Modeling renewable energy systems, in an accurate way which strongly depends on wind loads, requires reliable data to analyze their response and evaluate their performance. Otherwise poor agreement with the models may be obtained. In a case study for La Paz, Baja California Sur, Mexico, four different wind patterns were obtained from a one-year data set recorded at 10-min intervals. 相似文献
58.
长期以来 ,离心式水泵性能测定和曲线绘制工作无论是对生产厂家还是对用户都是很必要 ,但又是很繁杂的 .随着计算机技术的发展 ,数学正以其解决实际问题的卓越能力进入到各种领域 .从而使离心式水泵性能测定和曲线绘制工作得以简化 .MATLAB的出现又使离心式水泵的性能曲线的绘制达到了更加快速、准确、直观 . 相似文献
59.
本文重点介绍了方波依赖在音频测量,设备的维护检测及录音均衡自动调节等音频技术中的应用,并通过对方波信号的频谱特性和方波信号通过线性系统的频域特性的分析,简要说明了方波信号在应用电路中的基本工作原理。 相似文献
60.
新型并条胶辊套筒的特点及运用 总被引:1,自引:1,他引:0
为了解决常规并条胶辊套筒存在的易发热、易漏油,芯轴易弯曲磨损以及保养、能耗等问题,介绍了新型免加油并条胶辊套筒的性能特点并以实际生产数据进行对比;说明实际使用该新型并条胶辊套筒综合效果好,具有省工省时、降低消耗、质量稳定、使用寿命长、总投资少等优点。 相似文献