全文获取类型
收费全文 | 131200篇 |
免费 | 10542篇 |
国内免费 | 5743篇 |
专业分类
电工技术 | 7714篇 |
技术理论 | 10篇 |
综合类 | 8667篇 |
化学工业 | 22012篇 |
金属工艺 | 7206篇 |
机械仪表 | 8605篇 |
建筑科学 | 9644篇 |
矿业工程 | 3677篇 |
能源动力 | 3868篇 |
轻工业 | 8940篇 |
水利工程 | 2175篇 |
石油天然气 | 7785篇 |
武器工业 | 938篇 |
无线电 | 15027篇 |
一般工业技术 | 16786篇 |
冶金工业 | 6256篇 |
原子能技术 | 1478篇 |
自动化技术 | 16697篇 |
出版年
2024年 | 527篇 |
2023年 | 2093篇 |
2022年 | 3684篇 |
2021年 | 5145篇 |
2020年 | 3822篇 |
2019年 | 3408篇 |
2018年 | 3814篇 |
2017年 | 4213篇 |
2016年 | 3808篇 |
2015年 | 5077篇 |
2014年 | 6278篇 |
2013年 | 7675篇 |
2012年 | 8090篇 |
2011年 | 9013篇 |
2010年 | 7937篇 |
2009年 | 7386篇 |
2008年 | 7319篇 |
2007年 | 6920篇 |
2006年 | 6963篇 |
2005年 | 6195篇 |
2004年 | 4321篇 |
2003年 | 4032篇 |
2002年 | 4099篇 |
2001年 | 3505篇 |
2000年 | 3292篇 |
1999年 | 3326篇 |
1998年 | 2793篇 |
1997年 | 2273篇 |
1996年 | 2178篇 |
1995年 | 1866篇 |
1994年 | 1537篇 |
1993年 | 1150篇 |
1992年 | 866篇 |
1991年 | 684篇 |
1990年 | 511篇 |
1989年 | 403篇 |
1988年 | 353篇 |
1987年 | 212篇 |
1986年 | 177篇 |
1985年 | 134篇 |
1984年 | 95篇 |
1983年 | 56篇 |
1982年 | 63篇 |
1981年 | 51篇 |
1980年 | 41篇 |
1979年 | 21篇 |
1977年 | 7篇 |
1976年 | 16篇 |
1975年 | 11篇 |
1970年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
介绍一种自行设计、开发的一机多控视频点播系统,讲述了系统组成及设计方案,它具有服务功能多,操作方便、性能价格比高等特点。 相似文献
52.
Tien-Hsiang Sun Chao-Weng Cheng Li-Chen Fu 《Industrial Electronics, IEEE Transactions on》1994,41(6):593-601
In this paper, a timed-place Petri net (TPPN) model for flexible manufacturing systems (FMSs) is constructed, which contains two major submodels: the stationary transportation model; and the variable process flow model. For multiple automated guided vehicle (AGV) systems, the authors embed a simple rule and introduce a push-AGV strategy in a TPPN model to solve the collision and traffic jam problems of such vehicles. Since a firing sequence of the TPPN from the initial marking to the final marking can be seen as a schedule of the modeled FMS, by using an A* based search algorithm, namely, the limited-expansion A algorithm, an effective schedule of the part processing can be obtained. To show the promising potential of the proposed work, a prototype FMS is used as a target system for implementation. The experiment results assert that the job-shop scheduling problem can always be satisfactorily solved 相似文献
53.
The fabric and faces of threat, and the expediency and efficiency in the communication of threat, are examined with a threat appraisal model. This model is empirically tested on an ongoing communication challenge, the issuance of terror alerts by the United States' Department of Homeland Security (DHS), focusing on how threat is appraised by both the conservative and liberal audiences. Findings showed a shared view by the DHS and conservative audiences on the levels and nature of threats; liberal audiences thought otherwise. Though there appeared to be a consensus between the conservative and liberal audiences on the efficacy of threat communication, more internal consistency within DHS is needed to optimise its effectiveness. 相似文献
54.
BaTiO3 multilayer capacitors with a nominal capacitance of 3.5nF have been carefully measured using the thermally stimulated current (TSC) technique. When a 300V polarization voltage is applied at room temperature, a new TSC peak appeared in defective sample A after it has been immersed in water. No new peak was found in good-quality sample B after a similar treatment. The accelerated life test shows that sample A hasa much shorter life than sample B in terms of insulation resistance. 相似文献
55.
Hong Jin Mohammad S. Uddin Yu L. Huang Wah K. Teo 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1994,59(1):67-72
High level expression of recombinant human tumour necrosis factor β (rh TNF-β) in Escherichia coli results in the formation of two portions of protein, namely soluble active protein and insoluble protein which is inactive and aggregates in the form of inclusion bodies (IBs). In this study, a procedure for purification and renaturation of rh TNF-β from inclusion bodies has been designed and verified experimentally with a product purity of more than 90% and a recovery of about 30%. The procedure includes washing of IBs with specific wash buffer (Triton X-100/EDTA/lysozyme/PMSF), their solubilization with 8 mol dm?3 alkaline urea, purification with ion-exchange columns, refolding with renaturation buffer and finally concentration and desalination with an ultrafiltration membrane. The characteristics of the renatured protein were identical with those of purified protein from the soluble fraction as demonstrated by (1) SDS-PAGE, (2) cytotoxic activity on mouse L929 cells, (3) N-terminal amino acid sequence, and (4) gel filtration chromatography. 相似文献
56.
山洪灾害预警准确度与及时度研究 总被引:1,自引:0,他引:1
山洪灾害预警准确度与及时度是一对相互矛盾而又联系的重要指标。文章通过对这两项指标的研究和对引发灾害的降雨强度、降雨以及灾害发生的时间资料进行分析,从而获取预警系统建设的基本技术要点和参数,对把握山洪灾害预警系统的设计定位、启用时机和作用评估具有重要作用和意义。 相似文献
57.
58.
报道了以茈为荧光探针,探讨小剂量~(60)Co γ射线照射后小鼠胸腺细胞膜流动性的变化。结果表明,剂量在0.25-1.00Gy范围,胸腺细胞膜流动性降低与剂量之间呈明显线性关系。从0.50Gy起,辐照组荧光强度比值I_1/I_2与I_3/I_2与对照组的比较存有显著差异(P<0.05)。提示淋巴细胞膜流动性的变化可作为小剂量辐照早期效应的敏感指标。 相似文献
59.
60.
In CFD simulation of diesel combustion, the predictive capabilities of the spray model play the most important role. Consequently, under the strict guidelines of the V&V, a method to adjust parameters of diesel spray model WAVE to accompany with the in-cylinder physical progress has been investigated in this paper. Moreover, the simulation of the spray has been validated by high-speed photography experiments and verified by the equation proposed by Hiroyasu. Finally, a modified setup for the WAVE spray model has been proposed and applied in the spray and combustion simulation for Deutz1013 diesel in different engine speed. 相似文献