全文获取类型
收费全文 | 4038篇 |
免费 | 570篇 |
国内免费 | 470篇 |
专业分类
电工技术 | 283篇 |
综合类 | 360篇 |
化学工业 | 826篇 |
金属工艺 | 60篇 |
机械仪表 | 59篇 |
建筑科学 | 247篇 |
矿业工程 | 153篇 |
能源动力 | 90篇 |
轻工业 | 2284篇 |
水利工程 | 124篇 |
石油天然气 | 108篇 |
武器工业 | 2篇 |
无线电 | 35篇 |
一般工业技术 | 201篇 |
冶金工业 | 121篇 |
原子能技术 | 21篇 |
自动化技术 | 104篇 |
出版年
2024年 | 24篇 |
2023年 | 86篇 |
2022年 | 79篇 |
2021年 | 119篇 |
2020年 | 130篇 |
2019年 | 92篇 |
2018年 | 103篇 |
2017年 | 122篇 |
2016年 | 129篇 |
2015年 | 126篇 |
2014年 | 192篇 |
2013年 | 298篇 |
2012年 | 360篇 |
2011年 | 347篇 |
2010年 | 258篇 |
2009年 | 249篇 |
2008年 | 207篇 |
2007年 | 285篇 |
2006年 | 295篇 |
2005年 | 263篇 |
2004年 | 198篇 |
2003年 | 207篇 |
2002年 | 178篇 |
2001年 | 131篇 |
2000年 | 117篇 |
1999年 | 81篇 |
1998年 | 59篇 |
1997年 | 60篇 |
1996年 | 53篇 |
1995年 | 56篇 |
1994年 | 48篇 |
1993年 | 14篇 |
1992年 | 18篇 |
1991年 | 12篇 |
1990年 | 11篇 |
1989年 | 15篇 |
1988年 | 10篇 |
1987年 | 9篇 |
1986年 | 5篇 |
1985年 | 9篇 |
1984年 | 10篇 |
1983年 | 7篇 |
1982年 | 3篇 |
1980年 | 1篇 |
1977年 | 2篇 |
排序方式: 共有5078条查询结果,搜索用时 187 毫秒
1.
2.
For an effective optimization of pulp thermoforming and of the moulded pulp products manufactured by this process, a full understanding of the process physics combined with full knowledge of the pressing equipment is necessary. For this reason, in this Addendum, we clarify how the process parameters “Holding time,” “Vacuum time,” “Cycle time,” and “Temperature” were interpreted and subsequently defined for the analysis of the process and product‐related outputs of the thermoforming experiments. 相似文献
3.
以太阳纸业备料车间木片筛选碎料(筛余物)为原料,对其烧碱法半化学制浆的实验室工艺和生产试验进行了研究。结果表明,筛余物采用半化学法制浆可获得较高得率和环压强度的纸浆,且用碱量对纸浆性能有显著影响。相对8%NaOH (相对于绝干原料)化学预处理,采用14%NaOH化学预处理结合两段浆浓22%的高浓磨浆工艺,所制半化学浆抄造浆张的裂断长和环压指数分别达2.89 km和9.76 N·m/g,是前者的1.9倍和1.2倍,而且优于现用国内OCC废纸浆抄造浆张;生产试验得到的浆张性能指标与实验室相吻合,其中紧度和环压强度分别达到GB/T 13023—2008瓦楞芯(原)纸AA级和A级优等品要求。 相似文献
4.
5.
摘要:为研究溶解氧质量浓度对10Ni5CrMo钢在阴极极化条件下氢脆敏感性影响规律,对10Ni5CrMo钢进行了阴极极化下的电化学交流阻抗谱测试﹑并采用慢应变速率拉伸实验和断口分析方法研究了海水中溶解氧质量浓度变化和不同阴极极化下10Ni5CrMo钢的氢脆敏感性。结果表明:溶解氧质量浓度变化对10Ni5CrMo钢强度几乎没有影响;同一溶解氧质量浓度下,随极化电位负移,断裂时间、伸长率、断面收缩率明显降低,氢脆系数增加,氢脆敏感性显著提高,极化电位达到-1000mV时,氢脆系数已超过安全区允许的最高值25%,进入危险区;同一极化电位下,随着海水中溶解氧质量浓度减少,材料塑性变差,断裂时间、伸长率和断面收缩率不断降低,氢脆系数增加,氢脆敏感性提高。 相似文献
6.
This study evaluated the shear bond strength (SBS) and internal marginal adaptation of pulp‐capping materials to dentin. Flat occlusal deep dentin surfaces were produced and randomly assigned to two groups (sound or artificial caries‐affected dentin). The specimens in each group were assigned to one of seven subgroups according to the materials used: Biodentine, Theracal LC, Ultra‐Blend plus, Calcimol LC, ApaCal ART, EQUIA Forte, and Ionoseal. Buildups (3‐mm inner diameter and 2‐mm deep) were made over the dentin surfaces. The bonded specimens were tested under shear forces at a crosshead speed of 0.8 mm/min and fracture modes were determined using a stereomicroscope at 25× magnification. The materials were applied to the pulp floor of prepared Class I cavities and then the cavities were restored with composite resin. Restored molar teeth were subjected to 5,000 thermocycles and sectioned in a bucco–lingual direction. Resin replicas were made to determine the adaptation at the pulp floor with scanning electron microscopy. Significant differences were determined among both bond strengths and gap formations of the materials. EQUIA Forte applied to both dentin substrates had a significantly higher SBS than the other materials. The bond strength of each material was not influenced by the dentin condition. Biodentine (3.03%), EQUIA Forte (7.83%), and Theracal LC (13.37%) had lower gap formations compared to other materials but were not significantly different from each other. 相似文献
7.
8.
Luis Dias Miguel Ribeiro Armando Leitão Luis Guimarães Leonel Carvalho Manuel A. Matos Ricardo J. Bessa 《Quality and Reliability Engineering International》2021,37(6):2834-2852
Electrical utilities apply condition monitoring on power transformers (PTs) to prevent unplanned outages and detect incipient faults. This monitoring is often done using dissolved gas analysis (DGA) coupled with engineering methods to interpret the data, however the obtained results lack accuracy and reproducibility. In order to improve accuracy, various advanced analytical methods have been proposed in the literature. Nonetheless, these methods are often hard to interpret by the decision-maker and require a substantial amount of failure records to be trained. In the context of the PTs, failure data quality is recurrently questionable, and failure records are scarce when compared to nonfailure records. This work tackles these challenges by proposing a novel unsupervised methodology for diagnosing PT condition. Differently from the supervised approaches in the literature, our method does not require the labeling of DGA records and incorporates a visual representation of the results in a 2D scatter plot to assist in interpretation. A modified clustering technique is used to classify the condition of different PTs using historical DGA data. Finally, well-known engineering methods are applied to interpret each of the obtained clusters. The approach was validated using data from two different real-world data sets provided by a generation company and a distribution system operator. The results highlight the advantages of the proposed approach and outperformed engineering methods (from IEC and IEEE standards) and companies legacy method. The approach was also validated on the public IEC TC10 database, showing the capability to achieve comparable accuracy with supervised learning methods from the literature. As a result of the methodology performance, both companies are currently using it in their daily DGA diagnosis. 相似文献
9.
Lu Lin Ran Li Jing-jie Feng Ying-han Huang Xiao-dong Yong Yang-ming Ou You-quan Yuan 《水科学与水工程》2021,14(1):80-86
Supersaturation of dissolved gases in natural water, due to spillage from high dams and other factors, may cause fish mortality. In previous experiments, the dissipation coefficient has been used to denote the degassing process of total dissolved gas(TDG) saturation. These experiments mainly analyzed supersaturated TDG dissipation from a macroscopic view. To precisely clarify the mechanism of supersaturated TDG release, this study investigated bubble adsorption at a wall surface from a microscopic view. The experiment was conducted in a Plexiglas-wall container filled with supersaturated TDG water. A model that calculates the adsorption flux of supersaturated TDG by a solid wall, and helps describe construction for a contact angle at a three-phase intersection, was developed according to Young's equation. This model was used to investigate the formation process of bubbles adsorbed on a solid polymethyl methacrylate(PMMA) surface in supersaturated TDG water. The adsorption effect of a solid wall on TDG release was analyzed based on the experimental data. The modeling results were compared with observations under different wall area conditions, and it was found that TDG release tended to increase with wall area. This study helps improve our understanding of the mechanisms of supersaturated TDG release and provides an important theoretical method for accurate calculation of the release process. The adsorption flux model of the solid wall provides mitigation measures to combat the adverse effects of TDG supersaturation,which will be beneficial to the protection of aquatic organisms in hydropower-regulated rivers. 相似文献
10.
The pre-hydrolysis liquor (PHL) of the kraft-based dissolving pulp production process is currently sent to the recovery boiler and incinerated. However, PHL contains about 5–8% lignocelluloses that can be utilized in the production of value-added chemicals. In this study, a process for producing xylitol from hemicelluloses in PHL is developed. This process involves several acidification, neutralization, adsorption (along with reactivation) and evaporation stages. The mass balance indicates that 533 kg/h xylitol (with 99% purity), 187 kg/h lignin, 806 kg/h basic ferric acetate, and 1600 kg/h gypsum can be produced from 41,670 kg/h PHL. The energy balance shows that the evaporators are the largest consumers of energy, while the reactivation kiln, acidification, neutralization, and precipitation processes generate some heat. Overall, 41% conversion of xylose to xylitol is achieved. 相似文献