全文获取类型
收费全文 | 276481篇 |
免费 | 21368篇 |
国内免费 | 13815篇 |
专业分类
电工技术 | 17538篇 |
技术理论 | 51篇 |
综合类 | 37588篇 |
化学工业 | 30746篇 |
金属工艺 | 10786篇 |
机械仪表 | 14951篇 |
建筑科学 | 40912篇 |
矿业工程 | 15608篇 |
能源动力 | 8188篇 |
轻工业 | 15686篇 |
水利工程 | 14565篇 |
石油天然气 | 11753篇 |
武器工业 | 2638篇 |
无线电 | 17486篇 |
一般工业技术 | 19359篇 |
冶金工业 | 16435篇 |
原子能技术 | 2957篇 |
自动化技术 | 34417篇 |
出版年
2024年 | 859篇 |
2023年 | 2611篇 |
2022年 | 5059篇 |
2021年 | 6100篇 |
2020年 | 6503篇 |
2019年 | 5460篇 |
2018年 | 5112篇 |
2017年 | 6316篇 |
2016年 | 7475篇 |
2015年 | 8319篇 |
2014年 | 15416篇 |
2013年 | 14071篇 |
2012年 | 18301篇 |
2011年 | 19450篇 |
2010年 | 15481篇 |
2009年 | 16158篇 |
2008年 | 15017篇 |
2007年 | 19775篇 |
2006年 | 18692篇 |
2005年 | 16343篇 |
2004年 | 13958篇 |
2003年 | 12569篇 |
2002年 | 10403篇 |
2001年 | 8775篇 |
2000年 | 7443篇 |
1999年 | 6075篇 |
1998年 | 4551篇 |
1997年 | 4001篇 |
1996年 | 3692篇 |
1995年 | 3156篇 |
1994年 | 2790篇 |
1993年 | 2057篇 |
1992年 | 1839篇 |
1991年 | 1368篇 |
1990年 | 1193篇 |
1989年 | 1067篇 |
1988年 | 847篇 |
1987年 | 585篇 |
1986年 | 435篇 |
1985年 | 361篇 |
1984年 | 343篇 |
1983年 | 247篇 |
1982年 | 219篇 |
1981年 | 172篇 |
1980年 | 141篇 |
1979年 | 112篇 |
1978年 | 64篇 |
1977年 | 74篇 |
1976年 | 58篇 |
1975年 | 56篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
冶金坑内矿多级机站通风系统设计 总被引:2,自引:0,他引:2
本文简要论述了冶金坑内矿多级机站通风系统设计的基本原则及计算方法,并给出一个设计实例。 相似文献
92.
康山金矿地质地球化学特征及其成因 总被引:3,自引:1,他引:2
康山金矿产在豫西熊耳山古隆起区的结晶基底太华群和盖层中元古界熊耳群地层接触界面附近,矿体严格受构造破碎蚀变带控制。流体包裹体,稳定同位素等研究表明,成矿物质来自太华群变质岩,成矿流体的性质与变质热液截然不同,而与花岗岩浆热液相近似。该矿床的形成与燕山期发生的同构造-花岗岩浆期热液活动有关,金沉淀成矿阶段有大气水的混入。 相似文献
93.
Isolation and preliminary characterization of Pichia pinus mutants insensitive to glucose repression
A new method for the isolation of glucose repression-insensitive mutants in the methylotrophic yeast Pichia pinus was developed. The method is based on screening of small suspension samples derived from 2-deoxyglucose-resistant colonies for alcohol oxidase activity. Alcohol oxidase activity was evaluated by determination of formaldehyde excreted by cells. Mutants with glucose non-repressible alcohol oxidase and catalase synthesis were obtained. All mutants grew poorly on D -xylose compared to the wild type, whereas growth on L -arabinose was similar to the wild type. Changes in the glucose transport system were suggested to be responsible for altered growth characteristics and defective glucose repression. 相似文献
94.
对我国酱油酿造几项新技术应用之浅见 总被引:3,自引:0,他引:3
本文概述了三十年来我国酿造酱油工业开展研究的六项新技术在现阶段的投产可行性,及进一步研究方向的看法。 相似文献
95.
多孔粒状铵油炸药在边坡预裂爆破中的应用 总被引:3,自引:0,他引:3
通过工程实践,介绍了利用多孔粒状铵油炸药进行边坡预裂爆破的设计原理及施工工艺。该技术能确保预裂爆破质量。简化施工工序,大幅度降低爆破成本。技术经济指标优越。 相似文献
96.
Sang Cheol Lee Won Kook Lee 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1992,55(3):251-261
The extraction of penicillin G from simulated media was performed by water/oil/water (w/o/w) emulsion liquid membranes (ELMs) and studied under various operational conditions in a batch system. The degree of extraction achieved was between 80% and 95% under specific conditions. A concentration of greater than nine times the initial concentration of penicillin G in the external phase was obtained in the internal phase. The pH of the internal aqueous solution, containing a basic salt, was theoretically calculated on the basis of the amount of penicillin G transported into the internal phase. The calculated results agreed with the experimental data well and were used to select a suitable type and concentration of a basic salt in the internal phase to give a pH within the range 5 to 8 where penicillin G was stable after the termination of extraction. The extraction of penicillin G was successfully performed by the ELM process with sodium carbonate in the internal phase. 相似文献
97.
����ѡ������Ļ�ɫ���߷��� 总被引:2,自引:0,他引:2
本文根据灰色系统理论中的灰色决策原理,提出了一种合理选择钻机的新方法,并通过了实例验证。结果表明,这种方法切实可行。 相似文献
98.
本文研究了在以电子加速器的电子射线为辐射源时,剂量率对PTFE辐射裂解的影响。在剂量相同的条件下,剂量率从1.44×10~4 rad/s增至5.75×10~4 rad/s,裂解效率提高3.3倍。剂量率和各断裂参数(单位剂量裂解度a_0,G(s)值等)均成线性关系。当裂解度一定时,剂量率与剂量成反变关系。 相似文献
99.
D. P. Dreoni D. Pinelli F. Trifirò Z. Tvaruzkova H. Habersberger P. Jiru 《Catalysis Letters》1991,11(3-6):285-294
The catalyst behaviour of titanium silicalite, which was found the most active and selective catalyst for liquid-phase ammoximation of cyclohexanone to the corresponding oxime with hydrogen peroxide, was investigated in the gas-phase ammoximation with molecular oxygen in and compared with those of pure silicalite and samples of vanadium and chromium silicalites. The results showed that Ti-silicalite is a selective catalyst not only in the reaction with hydrogen peroxide but also in the reaction with molecular oxygen. However, a big limitation was found in the poor activity of the silicalites which do not allow to reach high oxime yields. 相似文献
100.
Safe and Economic Operation of Power Plants – Research Results in the Field of Materials, Design and Maintenance Components of power plants which undergo high temperatures are subjected to complex loading situations. The requirements on the used materials result from the special operation conditions of the plants and have to be adjusted to the steadily growing requirements on higher efficiency of the complete power plant as well as to those of safe and economic operation. The expenses for control and downtimes are directly connected with economic efficiency and availability. However, in case of new procedures or components it is not possible to revert to the existing know‐how. Different failure mechanisms than known before can occur. The same goes for the load situation. Therefore the knowledge base has to be extended to in‐advance or even parallely running scientific examinations that life assessment and maintenance strategies can be applied which guarantee the operational reliability and the efficiency of the plant. The main emphasis of these F&E works has to be put on condition monitoring based on actual operational data, the standard materials’ and component’s behaviour (deformation, damage and failure behaviour) in connection with design of components and the related material laws. In the framework of applied AVIF projects, following problems are handled:. – qualification of materials by determinating parameters related to practise. – optimal design of components by making available material laws and numerical tools. – economic manufacturing of components by qualifying processing methods such as welding. – The results can be transferred to concepts for safe and economic operation of power plants, especially for newly introduced materials for which there is no operational experience available. 相似文献