全文获取类型
收费全文 | 11550篇 |
免费 | 1200篇 |
国内免费 | 798篇 |
专业分类
电工技术 | 675篇 |
技术理论 | 1篇 |
综合类 | 928篇 |
化学工业 | 1794篇 |
金属工艺 | 716篇 |
机械仪表 | 763篇 |
建筑科学 | 1034篇 |
矿业工程 | 284篇 |
能源动力 | 364篇 |
轻工业 | 440篇 |
水利工程 | 450篇 |
石油天然气 | 1078篇 |
武器工业 | 62篇 |
无线电 | 814篇 |
一般工业技术 | 1316篇 |
冶金工业 | 796篇 |
原子能技术 | 50篇 |
自动化技术 | 1983篇 |
出版年
2024年 | 37篇 |
2023年 | 123篇 |
2022年 | 223篇 |
2021年 | 286篇 |
2020年 | 330篇 |
2019年 | 337篇 |
2018年 | 276篇 |
2017年 | 381篇 |
2016年 | 447篇 |
2015年 | 438篇 |
2014年 | 725篇 |
2013年 | 642篇 |
2012年 | 786篇 |
2011年 | 874篇 |
2010年 | 579篇 |
2009年 | 764篇 |
2008年 | 631篇 |
2007年 | 803篇 |
2006年 | 771篇 |
2005年 | 575篇 |
2004年 | 509篇 |
2003年 | 486篇 |
2002年 | 435篇 |
2001年 | 353篇 |
2000年 | 308篇 |
1999年 | 272篇 |
1998年 | 218篇 |
1997年 | 163篇 |
1996年 | 131篇 |
1995年 | 122篇 |
1994年 | 84篇 |
1993年 | 57篇 |
1992年 | 46篇 |
1991年 | 35篇 |
1990年 | 38篇 |
1989年 | 30篇 |
1988年 | 14篇 |
1987年 | 12篇 |
1986年 | 13篇 |
1985年 | 13篇 |
1984年 | 15篇 |
1982年 | 12篇 |
1981年 | 10篇 |
1980年 | 10篇 |
1979年 | 16篇 |
1978年 | 8篇 |
1964年 | 12篇 |
1958年 | 7篇 |
1957年 | 11篇 |
1956年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
11.
在总结引黄南干线建设经验和面临的营运问题的基础上,文中提出在确定北干线设计规模时,重点要处理好供水区水资源供需平衡与调水工程规模的关系;外调水与当地水资源的关系;长远规划指标与近期实施规模的关系;以及高水价对用水需求的抑制作用,进行全面分析,综合比较。 相似文献
12.
多功能杀菌剂的合成及其性能研究 总被引:7,自引:1,他引:6
在现有季铵盐类杀菌灭藻剂上增加一个脂键,连接一个有机酸基团,合成一种兼具阻垢缓蚀功能的新型工业水处理用杀菌灭藻剂(多功能杀菌剂),经一系列评价实验表明:新型杀菌剂是较理想的杀菌剂,在较低浓度下,对硫酸盐还原菌(SRB)及腐生菌(TGB)均有很好的杀灭效果,优于1227杀菌剂,同时还具有较好的缓蚀阻垢效果。 相似文献
13.
14.
The present empirical investigation had a 3-fold purpose: (a) to cross-validate L. R. Offermann, J. K. Kennedy, and P. W. Wirtz's (1994) scale of Implicit Leadership Theories (ILTs) in several organizational settings and to further provide a shorter scale of ILTs in organizations; (b) to assess the generalizability of ILTs across different employee groups, and (c) to evaluate ILTs' change over time. Two independent samples were used for the scale validation (N1 = 500 and N2 = 439). A 6-factor structure (Sensitivity, Intelligence, Dedication, Dynamism, Tyranny, and Masculinity) was found to most accurately represent ELTs in organizational settings. Regarding the generalizability of ILTs, although the 6-factor structure was consistent across different employee groups, there was only partial support for total factorial invariance. Finally, evaluation of gamma, beta, and alpha change provided support for ILTs' stability over time. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
15.
16.
17.
介绍了中国石化茂名分公司 2 .0Mt/a渣油加氢脱硫装置中的 4M80 30 /2 2 2 0 0 BX型新氢压缩机的特点、技术特征及标定情况。采用国际通用标准对压缩机气体组成、容积流量、轴功率、进排气压力和进排气温度等指标进行了测定。标定表明 ,该机组设计方案合理 ,运转平稳 ,性能指标达到设计要求 ,较好的满足了工艺操作的需要 相似文献
18.
In the oxidation of TiAl alloys, the role of scale-growth stresses formed during oxidation has, thus far, been unknown. In the present paper the oxide-growth stresses were investigated by the deflection-test method in monofacial oxidation (DTMO) accompanied by acoustic-emission measurements. On unmodified surfaces the growth stresses are compressive and reach levels of around –100 MPa. At the same time, significant acoustic emission occurs indicating that even under isothermal conditions, stresses are relieved by a scale-cracking mechanism. For oxide scales on TiAl surfaces, which had been ion implanted with chlorine before oxidation, a very thin protective alumina layer is formed which, however, develops growth stresses in the range of several GPa, accompanied by intensive acoustic emission. In all stress–time curves, a dynamic situation is observed. This consists of phases of stress relief by scale microcracking and phases of stresses increase due to crack healing and further oxide growth. As a result, the level of stress as a function of oxidation time, is characterized by an oscillating course. 相似文献
19.
A probabilistic model for cleavage fracture with a length scale--parameter estimation and predictions of stationary crack experiments 总被引:1,自引:0,他引:1
This study presents a large experimental investigation in the transition temperature region on a modified A508 steel. Tests were carried out on single-edge-notch-bend specimens with three different crack depth over specimen width ratios to capture the strong constraint effect on fracture toughness. Three test temperatures were considered, covering a range of 85 °C. All specimens failed by cleavage fracture prior to ductile tearing. A recently proposed probabilistic model for the cumulative failure by cleavage was applied to the comprehensive sets of experimental data. This modified weakest link model incorporates a length scale, which together with a threshold stress reduce the scatter in predicted toughness distributions as well as introduces a fracture toughness threshold value. Model parameters were estimated by a robust procedure, which is crucial in applications of probabilistic models to real structures. The conformity between predicted and experimental toughness distributions, respectively, were notable at all the test temperatures. 相似文献
20.
In order to improve the physical properties and slag corrosion resistance of refractory materials for hot metal pretreatment, different contents of composite metal powders (CMP) were introduced into Al2O3-SiC-C refractory castables. The effect of CMP on the microstructure, physical properties and slag corrosion resistance of Al2O3-SiC-C refractory castables were studied. The results show that the multi scale reinforcing phases including flake crystals, rod shaped fibers, filamentous fibers and whiskers are in situ formed in the samples with addition of CMP, which result to the improvement of the cold modulus of rupture and cold crushing strength. When the addition of CMP is 6 wt.%, the high temperature modulus of rupture increases by 231%, the thermal shock resistance increases by 77% after thermal shock by water cooling 5 times and the percentage of the slag resistant area reduces by 37.2%. 相似文献