全文获取类型
收费全文 | 37289篇 |
免费 | 3511篇 |
国内免费 | 1802篇 |
专业分类
电工技术 | 2719篇 |
综合类 | 2504篇 |
化学工业 | 8882篇 |
金属工艺 | 6718篇 |
机械仪表 | 1612篇 |
建筑科学 | 3760篇 |
矿业工程 | 1087篇 |
能源动力 | 1248篇 |
轻工业 | 2430篇 |
水利工程 | 833篇 |
石油天然气 | 1227篇 |
武器工业 | 267篇 |
无线电 | 2066篇 |
一般工业技术 | 4366篇 |
冶金工业 | 1879篇 |
原子能技术 | 260篇 |
自动化技术 | 744篇 |
出版年
2024年 | 208篇 |
2023年 | 761篇 |
2022年 | 1503篇 |
2021年 | 1662篇 |
2020年 | 1455篇 |
2019年 | 1143篇 |
2018年 | 1075篇 |
2017年 | 1495篇 |
2016年 | 1395篇 |
2015年 | 1409篇 |
2014年 | 1975篇 |
2013年 | 2054篇 |
2012年 | 2465篇 |
2011年 | 2784篇 |
2010年 | 1920篇 |
2009年 | 2243篇 |
2008年 | 1815篇 |
2007年 | 2148篇 |
2006年 | 2139篇 |
2005年 | 1762篇 |
2004年 | 1478篇 |
2003年 | 1287篇 |
2002年 | 1058篇 |
2001年 | 927篇 |
2000年 | 767篇 |
1999年 | 702篇 |
1998年 | 561篇 |
1997年 | 475篇 |
1996年 | 359篇 |
1995年 | 365篇 |
1994年 | 300篇 |
1993年 | 203篇 |
1992年 | 161篇 |
1991年 | 139篇 |
1990年 | 93篇 |
1989年 | 81篇 |
1988年 | 56篇 |
1987年 | 44篇 |
1986年 | 24篇 |
1985年 | 12篇 |
1984年 | 15篇 |
1983年 | 11篇 |
1982年 | 16篇 |
1981年 | 7篇 |
1980年 | 12篇 |
1979年 | 5篇 |
1961年 | 2篇 |
1960年 | 3篇 |
1959年 | 6篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Yoshiyuki Uno Akira Okada Kensuke Uemura Purwadi Raharjo Toshihiko Furukawa Kosaku Karato 《Precision Engineering》2005,29(4):171-455
A new finishing process for metal molds by large-area electron beam (EB) irradiation is proposed in this study. In the large-area EB irradiation equipment used here, an EB with high-energy density is irradiated without focusing the beam, and so the EB with a maximum diameter of 60 mm can be used for melting or evaporating metal surface instantly. Experimental results show that the surface roughness decreases from 6 μmRz to less than 1 μmRz in just a few minutes under proper machining conditions. The corrosion resistance of metal mold surface also could be greatly improved by large-area EB irradiation. Furthermore, the surface roughness of tilting surface close to 90° could be well improved. Therefore, large-area EB irradiation method has a possibility to become a high-efficiency finishing process for metal molds. 相似文献
82.
83.
制备了导电聚苯胺锂基润滑脂(简称PANI脂)和铜基银镀层材料(简称银层材料)。采用摩擦磨损试验机考察在无载流、载流及边界润滑条件下,铜基体材料(简称铜基材料)和银层材料的摩擦磨损性能。采用X射线衍射(XRD)、扫描电子显微镜(SEM)和电子能谱(EDS)对银层材料晶相及其表面磨斑形貌进行表征。结果表明,载流条件下,PANI脂润滑试验时的银层材料不仅具有良好的减摩抗磨性能,而且导电能力更强,其优异的减摩和抗磨性能归功于摩擦表面的保护膜和电流热效应引起的表面软化双重作用。 相似文献
84.
V. K. Voronin S. A. Evdokimov A. I. Leviush A. L. Trofimov 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2006,40(3):190-195
Disturbance of the grounding of the shaft of a turboset or its absence for technical reasons can result in failure, misoperation,
limitation of the operating zone, errors or limitation of the sensitivity of devices for control and protection of exciting
circuits from single-point leakage, and electroerosion of elements of the turboset structure. Measures for increasing the
reliability of the grounding of the shaft are discussed.
__________
Translated from élektricheskie Stantsii, No. 3, March 2006, pp. 61–66. 相似文献
85.
86.
Identification of critical erosion prone areas in the small agricultural watershed using USLE,GIS and remote sensing 总被引:10,自引:1,他引:9
In the present study, Karso watershed of Hazaribagh, Jharkhand State, India was divided into 200 × 200 grid cells and average
annual sediment yields were estimated for each grid cell of the watershed to identify the critical erosion prone areas of
watershed for prioritization purpose. Average annual sediment yield data on grid basis was estimated using Universal Soil
Loss Equation (USLE). In general, a major limitation in the use of hydrological models has been their inability to handle
the large amounts of input data that describe the heterogeneity of the natural system. Remote sensing (RS) technology provides
the vital spatial and temporal information on some of these parameters. A recent and emerging technology represented by Geographic
Information System (GIS) was used as the tool to generate, manipulate and spatially organize disparate data for sediment yield
modeling. Thus, the Arc Info 7.2 GIS software and RS (ERDAS IMAGINE 8.4 image processing software) provided spatial input
data to the erosion model, while the USLE was used to predict the spatial distribution of the sediment yield on grid basis.
The deviation of estimated sediment yield from the observed values in the range of 1.37 to 13.85 percent indicates accurate
estimation of sediment yield from the watershed. 相似文献
87.
Rinji Akada Yoshirou Shimizu Yuji Matsushita Miho Kawahata Hisashi Hoshida Yoshinori Nishizawa 《Yeast (Chichester, England)》2002,19(1):17-28
Drug-resistance markers for yeast transformation are useful because they can be applied to strains without auxotrophic mutations. However, they are susceptible to technical difficulties, namely lower transformation efficiency and the appearance of drug-resistant mutants without the marker. To avoid these problems, we have constructed a phosphoglycerate kinase (PGK) promoter-driven YAP1 expression cassette, called PGKp-YAP1. Yeast cells containing PGKp-YAP1 were resistant to cycloheximide, a protein synthesis inhibitor, and also to cerulenin, a fatty acid synthesis inhibitor, but not to other drugs tested. The transformation efficiency of PGKp-YAP1 using cerulenin selection was comparable to that using a URA3 auxotrophic marker when low concentrations of cerulenin were used. Non-transformed drug-resistant colonies did appear on the low-concentration cerulenin plates. However, these non-transformed colonies could easily be identified, based on their cycloheximide sensitivity and/or their resistance to aureobasidin A to which the transformants were sensitive. Therefore, the dual drug resistance of PGKp-YAP1 could be used as an effective selection for PGKp-YAP1 recipient cells. The PGKp-YAP1 marker was used to disrupt the LYS2 gene and to transform an industrial yeast strain, indicating that this marker can be used for efficient and reliable gene manipulations in any Saccharomyces cerevisiae strain. 相似文献
88.
89.
Different qualities of concrete have been fire tested using different geometries of the specimens as well as different load levels and load configurations. The main objective with the study was to examine a test methodology consisting of a full‐scale test and different small scale‐tests for determining the probability of spalling and the amount of spalling of fire exposed concrete structures. A reference specimen was defined as a one‐sided fire exposed slab with the dimensions 1800 × 1200 mm2 giving an exposed area of 1500 × 1200 mm2. A number of concrete qualities with different probabilities for spalling, were tested using the reference specimen. These tests showed that the reference specimens worked well giving the expected test results. Small specimens were manufactured in different shapes with the same concrete as the one used in the reference tests. These small specimens were tested either at the same time as the reference specimens in the large furnace or afterwards on a small‐scale furnace where the fire exposed surface was 450 × 360 mm2. The test results clearly show the increased probability and the increased amount of spalling by using external compressive loading. The results also show that by using pre‐stress through bars or wires the load can be lost due to heating of the bars/wires which results in a decreased amount of spalling. The boundary of the specimen also affects the amount of spalling. The spalling around the edges was in all tests less than the spalling on the central parts of the exposed area. It could also be noted that the spalling did not pass completely through any of the specimens. The reason for this is probably that the water/vapour could migrate out from the unexposed surface of the specimen. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
90.
关于差阻式仪器的几个技术问题 总被引:1,自引:0,他引:1
本文对差阻式仪器的几个重要问题,如差阻式仪器的国家标准、监测数据的质量控制、长期埋设仪器的现场鉴定、仪器测值异常的分析处理等进行了讨论,并提出了自己的意见,供有关科研人员进一步研究和参考. 相似文献