全文获取类型
收费全文 | 53186篇 |
免费 | 5818篇 |
国内免费 | 2212篇 |
专业分类
电工技术 | 6412篇 |
技术理论 | 3篇 |
综合类 | 4229篇 |
化学工业 | 4865篇 |
金属工艺 | 1507篇 |
机械仪表 | 1402篇 |
建筑科学 | 8702篇 |
矿业工程 | 1299篇 |
能源动力 | 6196篇 |
轻工业 | 7190篇 |
水利工程 | 3072篇 |
石油天然气 | 2161篇 |
武器工业 | 258篇 |
无线电 | 3145篇 |
一般工业技术 | 4573篇 |
冶金工业 | 1468篇 |
原子能技术 | 269篇 |
自动化技术 | 4465篇 |
出版年
2024年 | 371篇 |
2023年 | 1231篇 |
2022年 | 1982篇 |
2021年 | 2285篇 |
2020年 | 2361篇 |
2019年 | 2134篇 |
2018年 | 1853篇 |
2017年 | 2051篇 |
2016年 | 2051篇 |
2015年 | 2139篇 |
2014年 | 3465篇 |
2013年 | 3115篇 |
2012年 | 3800篇 |
2011年 | 4065篇 |
2010年 | 2904篇 |
2009年 | 2946篇 |
2008年 | 2714篇 |
2007年 | 3216篇 |
2006年 | 2911篇 |
2005年 | 2338篇 |
2004年 | 2004篇 |
2003年 | 1637篇 |
2002年 | 1372篇 |
2001年 | 1155篇 |
2000年 | 955篇 |
1999年 | 773篇 |
1998年 | 632篇 |
1997年 | 508篇 |
1996年 | 437篇 |
1995年 | 328篇 |
1994年 | 312篇 |
1993年 | 210篇 |
1992年 | 196篇 |
1991年 | 113篇 |
1990年 | 83篇 |
1989年 | 95篇 |
1988年 | 74篇 |
1987年 | 60篇 |
1986年 | 49篇 |
1985年 | 70篇 |
1984年 | 44篇 |
1983年 | 31篇 |
1982年 | 27篇 |
1981年 | 19篇 |
1980年 | 32篇 |
1979年 | 12篇 |
1977年 | 8篇 |
1976年 | 8篇 |
1975年 | 8篇 |
1974年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
111.
112.
介绍湛江东兴炼油厂的重整装置由200kt/a扩能至300kt/a中有关催化重整反应动力学模拟计算软件的应用、反应工艺技术的改造、装置标定的情况。结合装置实际情况,采用两段装填、两段混氢技术提升了装置的技术水平。标定结果表明,改造后的装置达到了预期目的。 相似文献
113.
简要介绍了鞍钢现有人造富矿生产能力,分析了鞍钢生产1600万t/a生铁所需要的炉料数量、品种和质量,并提出了解决炉料缺口的方法和措施。 相似文献
114.
115.
The eye movements of young and older adults were tracked as they read sentences varying in syntactic complexity. In Experiment 1, cleft object and object relative clause sentences were more difficult to process than cleft subject and subject relative clause sentences; however, older adults made many more regressions, resulting in increased regression path fixation times and total fixation times, than young adults while processing cleft object and object relative clause sentences. In Experiment 2, older adults experienced more difficulty than young adults while reading cleft and relative clause sentences with temporary syntactic ambiguities created by deleting the that complementizers. Regression analyses indicated that readers with smaller working memories need more regressions and longer fixation times to process cleft object and object relative clause sentences. These results suggest that age-associated declines in working memory do affect syntactic processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
116.
一种三叉树的存储结构及其基本操作的实现 总被引:3,自引:0,他引:3
本文在文献[1]所给出的有关三叉树有其相关概念的基础上,提出了一种新的三叉树存储结构,即“儿子-兄弟链表”方法,并在这种结构下,对三叉树的基本操作的实现算法进行了较详细的讨论。 相似文献
117.
This paper presents a new computerized procedure for dealing with the design of horizontal ground heat exchangers (HGHE). The computer program is based on the transient model of coupled nonlinear partial differential equations governing heat and mass flow in soils. The model is two-dimensional and delineates the operation of ground heat storage with the HGHE and such phenomena as freezing/thawing and drying/rewetting of soil moisture. Comprehensive climatological data, such as ambient temperature, solar radiation, wind velocity, rainfall, snowfall, snow characterstics, and water vapour pressure is used to simulate conditions at the ground surface over any required length of time. The package can be applied to any geographical location by changing climatic and soil data input. The designer has the possibility of selecting any of 12 types of soils from sand to clay, 12 commercial heat pumps, nine different configurations of the HGHE, 16 plastic pipes for ground coils, and 13 ground coil fluids. The program, however, does not calculate the length of the HGHE but it evaluates the thermodynamic performance of a ground heat pump system and provides comprehensive data on thermal and hydraulic conditions in ground heat storage. The length of the ground heat exchanger is obtained from a line source theory model or from site dimensions and pipe spacing. Computed results for ground heat exchanger operation correlate fairly well with experimental data. Simulation of temperature and moisture content in the ground for natural conditions (no heat extraction/deposition) showed a fair agreement with field data. The entire computer program is user-friendly, interactive, menu-driven, and written in FORTRAN 77. 相似文献
118.
A cryo-specimen storage system for low-temperature scanning electron microscopy (LTSEM) specimens is described, which: liberates multi-specimen experiments from sampling restrictions imposed by the rate at which LTSEM specimens can be examined in the SEM; provides security against experiment loss resulting from breakdown of the SEM or cryo-system; enables collection of specimens in the field or in laboratories remote from the SEM laboratory; and facilitates international air transport of LTSEM specimens. The components of the system, which has a capacity of 98 stub-mounted specimens, are readily made in a laboratory workshop. The details of the design may be altered to suit particular specimen types or experimental approaches. 相似文献
119.
本文总结了近年冶金炉渣氮酸盐容量的研究方法,氮在炉渣中存在形态与炉渣氧分压的关系,炉渣氮化物容量与温度及炉渣成分的关系,并给出设计钢液脱氮渣系的基本原则。 相似文献
120.
ChangLIU HuimingCHENG 《材料科学技术学报》2002,18(2):124-126
Single=walled carbon nanotubes(SWNTs) were synthesized by a hydrogen arc discharge method.A high yield of gram quantity of SWNTs per hour was achieved.Tow kinds of SWNT products:web-like substancea and thin films in large slices were obtained. Results of resonant Raman scattering measurements indicate that the SWNTs prepared have a wider diameter distribution and a larger mean diameter.Hydrogen uptake measurements of the two kinds of SWNT samples(both as prepared and pretreated) were carried out using a high pressure volumetric method,respectively.And a hydrogen storage capacity of 4 wt pct could be repeatedly achieved for the suitably pretreated SWMNTs,whicb indicates that SWNTs may be a promising hydrogen storge material. 相似文献