全文获取类型
收费全文 | 102552篇 |
免费 | 10835篇 |
国内免费 | 5040篇 |
专业分类
电工技术 | 20833篇 |
技术理论 | 4篇 |
综合类 | 7035篇 |
化学工业 | 16420篇 |
金属工艺 | 5960篇 |
机械仪表 | 4514篇 |
建筑科学 | 6647篇 |
矿业工程 | 2076篇 |
能源动力 | 13002篇 |
轻工业 | 7432篇 |
水利工程 | 1874篇 |
石油天然气 | 3770篇 |
武器工业 | 1167篇 |
无线电 | 6730篇 |
一般工业技术 | 10369篇 |
冶金工业 | 3897篇 |
原子能技术 | 1047篇 |
自动化技术 | 5650篇 |
出版年
2024年 | 450篇 |
2023年 | 2030篇 |
2022年 | 3086篇 |
2021年 | 3798篇 |
2020年 | 3946篇 |
2019年 | 3433篇 |
2018年 | 3050篇 |
2017年 | 3678篇 |
2016年 | 3595篇 |
2015年 | 3804篇 |
2014年 | 6427篇 |
2013年 | 6054篇 |
2012年 | 7380篇 |
2011年 | 7631篇 |
2010年 | 5475篇 |
2009年 | 5608篇 |
2008年 | 5001篇 |
2007年 | 6453篇 |
2006年 | 6113篇 |
2005年 | 4977篇 |
2004年 | 4436篇 |
2003年 | 3842篇 |
2002年 | 3156篇 |
2001年 | 2830篇 |
2000年 | 2363篇 |
1999年 | 1855篇 |
1998年 | 1394篇 |
1997年 | 1219篇 |
1996年 | 995篇 |
1995年 | 782篇 |
1994年 | 648篇 |
1993年 | 479篇 |
1992年 | 475篇 |
1991年 | 360篇 |
1990年 | 287篇 |
1989年 | 260篇 |
1988年 | 211篇 |
1987年 | 135篇 |
1986年 | 112篇 |
1985年 | 120篇 |
1984年 | 110篇 |
1983年 | 106篇 |
1982年 | 84篇 |
1981年 | 42篇 |
1980年 | 28篇 |
1979年 | 12篇 |
1975年 | 13篇 |
1974年 | 10篇 |
1959年 | 11篇 |
1951年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
41.
氢工质在新能源与动力、航天推进、化工材料等领域有着广泛应用。通过开展高温氢工质热力学与输运性质研究,建立了原子态氢、分子态氢、热解平衡态氢的热物理性质计算模型,开发了热物性计算程序Prop_H_H2,适用范围为温度100~3 500 K、压力104~5×107 Pa 。验证表明,Prop_H_H2在适用范围内计算氢工质的物性参数合理可靠,在温度200~3 000 K、压力104~107 Pa范围内,程序预测值更加准确,相对偏差在±5%左右。本研究可为氢工质相关的航天推进、应用物理学、能源动力等行业的科研和应用提供支持借鉴。 相似文献
42.
43.
44.
45.
Qiaozhi Zhang Yanbo Wang Linglin Fu 《Comprehensive Reviews in Food Science and Food Safety》2020,19(5):2559-2587
Dietary advanced glycation end products (dAGEs) are complex and heterogeneous compounds derived from nonenzymatic glycation reactions during industrial processing and home cooking. There is mounting evidence showing that dAGEs are closely associated with various chronic diseases, where the absorbed dAGEs fuel the biological AGEs pool to exhibit noxious effects on human health. Currently, due to the uncertain bioavailability and rapid renal clearance of dAGEs, the relationship between dAGEs and biological AGEs remains debatable. In this review, we provide the most updated information on dAGEs including their generation in processed foods, analytical and characterization techniques, metabolic fates, interaction with AGE receptors, implications on human health and reducing strategies. Available evidence demonstrating a relevance between dAGEs and food allergy is also included. AGEs are ubiquitous in foods and their contents largely depend on the reactivity of carbonyl and amino groups, along with surrounding condition mainly pH and heating procedures. Once being digested and absorbed into the circulation, two separate pathways can be involved in the deleterious effects of dAGEs: an AGE receptor‐dependent way to stimulate cell signals, and an AGE receptor‐independent way to dysregulate proteins via forming complexes. Inhibition of AGEs formation during food processing and reduction in the diet are two potent approaches to restrict health‐hazardous dAGEs. To elucidate the biological role of dAGEs toward human health, the following significant perspectives are raised: molecular size and complexity of dAGEs; interactions between unabsorbed dAGEs and gut microbiota; and roles played by concomitant compounds in the heat‐processed foods. 相似文献
46.
The intermittent wind power in isolated hybrid distributed generation (IHDG) may cause serious problems associated with frequency (f) and power (P) fluctuation. Energy storage devices such as battery, super capacitor, and superconducting magnetic energy storage (SMES) may be used to reduce these fluctuations associated with f and P. This paper presents a study of IHDG power system for improving both f and P deviation profiles with the help of SMES. The studied IHDG power system is consisted of wind turbine generator and diesel engine generator. Both f and P control problems of the studied power system model are addressed in presence or absence of SMES. Fuzzy logic based proportional–integral–derivative (PID) controller with SMES is used for the purpose of minimization of f and P deviations. The different tunable parameters of the PID controller and those of the SMES are tuned by a novel quasi-oppositional harmony search algorithm. Performance study of the IHDG power system model is carried out under different perturbation conditions. The results demonstrate minimum f and P deviations may be achieved by using the proposed fuzzy logic based PID controller along with SMES. 相似文献
47.
Isaac Isarn Leïla Bonnaud Lluís Massagus ngels Serra Francesc Ferrando 《Polymer International》2020,69(3):280-290
The enhancement of the thermal conductivity, keeping the electrical insulation, of epoxy thermosets through the addition of pristine and oxidized carbon nanotubes (CNTs) and microplatelets of boron nitride (BN) was studied. Two different epoxy resins were selected: a cycloaliphatic (ECC) epoxy resin and a glycidylic (DGEBA) epoxy resin. The characteristics of the composites prepared were evaluated and compared in terms of thermal, thermomechanical, rheological and electrical properties. Two different dispersion methods were used in the addition of pristine and oxidized CNTs depending on the type of epoxy resin used. Slight changes in the kinetics of the curing reaction were observed in the presence of the fillers. The addition of pristine CNTs led to a greater enhancement of the mechanical properties of the ECC composite whereas the oxidized CNTs presented a greater effect in the DGEBA matrix. The addition of CNTs alone led to a marked decrease of the electrical resistivity of the composites. Nevertheless, in the presence of BN, which is an electrically insulating material, it was possible to increase the proportion of pristine CNTs to 0.25 wt% in the formulation without deterioration of the electrical resistivity. A small but significant synergic effect was determined when both fillers were added together. Improvements of about 750% and 400% in thermal conductivity were obtained in comparison to the neat epoxy matrix for the ECC and DGEBA composites, respectively. © 2019 Society of Chemical Industry 相似文献
48.
介绍机械制造厂燃煤锅炉的烟尘特点,分析滤料失效的原因,提出一套针对该工况的滤料解决方案。介绍针对复杂工况条件所选用的纤维种类以及复合面层原料成分配比的确定,最终选用针刺工艺加工并对该新产品的基本性能进行了测试分析。 相似文献
49.
50.