全文获取类型
收费全文 | 165358篇 |
免费 | 10262篇 |
国内免费 | 8656篇 |
专业分类
电工技术 | 8125篇 |
技术理论 | 70篇 |
综合类 | 16027篇 |
化学工业 | 14872篇 |
金属工艺 | 6125篇 |
机械仪表 | 16228篇 |
建筑科学 | 42845篇 |
矿业工程 | 5550篇 |
能源动力 | 4146篇 |
轻工业 | 5761篇 |
水利工程 | 5433篇 |
石油天然气 | 4945篇 |
武器工业 | 2118篇 |
无线电 | 9538篇 |
一般工业技术 | 17061篇 |
冶金工业 | 3929篇 |
原子能技术 | 789篇 |
自动化技术 | 20714篇 |
出版年
2024年 | 626篇 |
2023年 | 1915篇 |
2022年 | 2917篇 |
2021年 | 3821篇 |
2020年 | 4124篇 |
2019年 | 3117篇 |
2018年 | 3059篇 |
2017年 | 3808篇 |
2016年 | 4481篇 |
2015年 | 4820篇 |
2014年 | 12572篇 |
2013年 | 9518篇 |
2012年 | 11765篇 |
2011年 | 12593篇 |
2010年 | 10659篇 |
2009年 | 11029篇 |
2008年 | 10159篇 |
2007年 | 12142篇 |
2006年 | 10392篇 |
2005年 | 9257篇 |
2004年 | 7624篇 |
2003年 | 6724篇 |
2002年 | 5203篇 |
2001年 | 4312篇 |
2000年 | 3526篇 |
1999年 | 2756篇 |
1998年 | 2208篇 |
1997年 | 1844篇 |
1996年 | 1558篇 |
1995年 | 1234篇 |
1994年 | 1005篇 |
1993年 | 711篇 |
1992年 | 578篇 |
1991年 | 441篇 |
1990年 | 291篇 |
1989年 | 289篇 |
1988年 | 219篇 |
1987年 | 162篇 |
1986年 | 98篇 |
1985年 | 110篇 |
1984年 | 148篇 |
1983年 | 94篇 |
1982年 | 104篇 |
1981年 | 39篇 |
1980年 | 47篇 |
1979年 | 34篇 |
1978年 | 15篇 |
1977年 | 14篇 |
1959年 | 11篇 |
1951年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
73.
织金电视台通过对有线电视网络进行双向改造,为Internet宽带接入、数字电视、VOD等多媒体应用提供了运行平台,介绍织金县城区HFC双向网络设计方案。 相似文献
74.
介绍了柳钢新建120万t/a链篦机-回转窑氧化球团工程的主要设计特点。该工程是我国第一条自行设计、设备国产化和采用清洁气体能源的链篦机-回转窑生产线。它的顺利投产,标志着我国炼铁炉料生产技术有了一个新的进步。 相似文献
75.
大型往复式压缩机功率大、占地面积大,管道振动问题也更为突出。笔者结合实践经验,对大型往复式压缩机的配管设计进行探讨,说明了平面布置与管道防振设计的密切关系,并介绍了管道防振设计的方法和步骤,以及相对简单的复杂管系气柱固有频率的转移矩阵计算方法。 相似文献
76.
The focus of this paper lies in the practical aspects of voice over IP communication. VoIP configurations in the H.323 standard will be presented briefly. Following that, the fundamental protocol procedure of H.323 communication will be briefly explained. A further part of the paper will address the subject QoS (quality of service), and present the common measurement methods used in QoS. Results gained from experiments conducted in a VoIP environment will then follow. The investigations concentrate primarily on the load behavior of voice packets in relation to important parameters of this service. The results obtained are presented and evaluated in diagrams. The paper concludes with a summary. 相似文献
77.
An approach is presented to satisfy the demand for simple criteria, guidelines and models for the preliminary sizing of horizontal subsurface flow (SF) constructed wetland systems. This approach eliminates time-consuming calculations and iterations by providing graphical solutions for wetland system sizing. Therefore, it can be used for the preliminary assessment of new or performance evaluation of existing subsurface flow constructed wetland systems. The validity of this methodology is checked with data from existing systems and is found to be quite satisfactory. This methodology is combined with simple equations predicting the maximum wetland capacity in summer, so as to assist designers in sizing installations in tourist areas with increased summer populations. Furthermore, based on this methodology, a sensitivity analysis is performed of the area requirements for wastewaters of various strengths and various design conditions and performance criteria. The results provide a useful overview to engineers and further simplify the design methodology of new subsurface flow constructed wetland systems. 相似文献
78.
Requirements engineering in health care: the example of chemotherapy planning in paediatric oncology
Health care is characterized by highly complex processes of patient care that require unusual amount of communication between different health care professionals of different institutions. Sub-optimal processes can significantly impact on the patient’s health, increase the consumption of services and resources and in severe cases can lead to the patient death. For these reasons, requirements engineering for the development of information technology in health care is a complex process as well: without constant and rigorous evaluation, the impact of new systems on the quality of care is unknown and it is possible that badly designed systems significantly harm patients. To overcome these limitations, we present and discuss an approach to requirements engineering that we applied for the development of applications for chemotherapy planning in paediatric oncology. Chemotherapy planning in paediatric oncology is complex and time-consuming and errors must be avoided by all means. In the multi-hospital/multi-trial-centre environment of paediatric oncology, it is especially difficult and time-consuming to analyse requirements. Our approach combines a grounded theory approach with evolutionary prototyping based on the constant development and refinement of a generic domain model, in this case a domain model for chemotherapy planning in paediatric oncology. The prototypes were introduced in medical centres and final results show that the developed generic domain model is adequate. 相似文献
79.
石油化工可燃气体或蒸气排放系统的消防安全设计 总被引:1,自引:1,他引:0
石油化工生产装置大多是通过火炬燃烧排放易燃易爆气体或通过放空管将易爆气体直接排入大气中。文章分析了火炬系统和放空管的火灾危险因素,并从火炬的布置、高度、排放能力、自动监控装置以及放空管的气体排放浓度、安装位置、安全装置等方面,重点论述了火炬系统和放空管的消防安全设计要点。 相似文献
80.
A stochastic model for local disturbances, particularly for a temporal harmonic with random modulations in amplitude and/or phase, is proposed in this paper. Results for the second moment responses of a linear single-degree-of-freedom system to this type of stochastic loading demonstrate a significant change in response characteristics due to a small uncertainty. A local phenomenon may last much longer and resonance may be smeared to a broad range. Integrated with wavelet transform, the proposed approach may be used to model a random process with non-stationary frequency content. Especially, it can be effectively used for Monte Carlo simulation to generate large size of samples that have similar characteristics in time and frequency domains as a pre-selected mother sample has. The technique has a great potential for the case where uncertainty study is warranted but the available samples are limited. 相似文献