全文获取类型
收费全文 | 6858篇 |
免费 | 554篇 |
国内免费 | 196篇 |
专业分类
电工技术 | 225篇 |
综合类 | 251篇 |
化学工业 | 1158篇 |
金属工艺 | 279篇 |
机械仪表 | 227篇 |
建筑科学 | 400篇 |
矿业工程 | 114篇 |
能源动力 | 199篇 |
轻工业 | 532篇 |
水利工程 | 215篇 |
石油天然气 | 113篇 |
武器工业 | 74篇 |
无线电 | 537篇 |
一般工业技术 | 1010篇 |
冶金工业 | 1217篇 |
原子能技术 | 81篇 |
自动化技术 | 976篇 |
出版年
2024年 | 17篇 |
2023年 | 86篇 |
2022年 | 185篇 |
2021年 | 284篇 |
2020年 | 198篇 |
2019年 | 177篇 |
2018年 | 208篇 |
2017年 | 192篇 |
2016年 | 214篇 |
2015年 | 251篇 |
2014年 | 368篇 |
2013年 | 469篇 |
2012年 | 473篇 |
2011年 | 537篇 |
2010年 | 392篇 |
2009年 | 393篇 |
2008年 | 378篇 |
2007年 | 381篇 |
2006年 | 297篇 |
2005年 | 226篇 |
2004年 | 201篇 |
2003年 | 148篇 |
2002年 | 155篇 |
2001年 | 94篇 |
2000年 | 64篇 |
1999年 | 89篇 |
1998年 | 188篇 |
1997年 | 135篇 |
1996年 | 93篇 |
1995年 | 60篇 |
1994年 | 47篇 |
1993年 | 55篇 |
1992年 | 21篇 |
1990年 | 22篇 |
1989年 | 23篇 |
1988年 | 18篇 |
1987年 | 16篇 |
1986年 | 21篇 |
1985年 | 26篇 |
1984年 | 21篇 |
1983年 | 21篇 |
1982年 | 25篇 |
1981年 | 31篇 |
1980年 | 17篇 |
1979年 | 27篇 |
1978年 | 21篇 |
1977年 | 33篇 |
1976年 | 57篇 |
1975年 | 19篇 |
1974年 | 18篇 |
排序方式: 共有7608条查询结果,搜索用时 281 毫秒
121.
针对化学链燃烧气固反应速率的影响因素复杂未知的问题,本文建立了碳粒与CaSO4载氧体颗粒在水蒸气气氛下的数理模型,并利用Fluent进行数值计算,从微观上分析了温度和压力的改变,对颗粒间化学链燃烧反应速率、CO2生成速率以及载氧体表面固相生成物沉积速率的影响。分析结果表明,提高反应器内的温度和压力,均加快了CaSO4载氧体颗粒表面CaS的沉积速率,且压力的提高在很大程度上促进了沉积速率的增加,而沉积覆盖在载氧体表面上的CaS导致了反应速率的下降。该研究有利于高纯度CO2气体的捕集,从而达到减排的目的,对化学链反应速率的控制具有重要意义。 相似文献
122.
Xiaonan Lu Joelle T. Reiser Benjamin Parruzot Lu Deng Igor M. Gussev Jörg C. Neuefeind Trent R. Graham Hongshen Liu Joseph V. Ryan Seong H. Kim Nancy Washton Maik Lang Jincheng Du John D. Vienna 《Journal of the American Ceramic Society》2021,104(1):183-207
High-alumina containing high-level waste (HLW) will be vitrified at the Waste Treatment Plant at the Hanford Site. The resulting glasses, high in alumina, will have distinct composition-structure-property (C-S-P) relationships compared to previously studied HLW glasses. These C-S-P relationships determine the processability and product durability of glasses and therefore must be understood. The main purpose of this study is to understand the detailed structural changes caused by Al:Si and (Al + Na):Si substitutions in a simplified nuclear waste model glass (ISG, international simple glass) by combining experimental structural characterizations and molecular dynamics (MD) simulations. The structures of these two series of glasses were characterized by neutron total scattering and 27Al, 23Na, 29Si, and 11B solid-state nuclear magnetic resonance (NMR) spectroscopy. Additionally, MD simulations were used to generate atomistic structural models of the borosilicate glasses and simulation results were validated by the experimental structural data. Short-range (eg, bond distance, coordination number, etc) and medium-range (eg, oxygen speciation, network connectivity, polyhedral linkages) structural features of the borosilicate glasses were systematically investigated as a function of the degree of substitution. The results show that bond distance and coordination number of the cation-oxygen pairs are relatively insensitive to Al:Si and (Al + Na):Si substitutions with the exception of the B-O pair. Additionally, the Al:Si substitution results in an increase in tri-bridging oxygen species, whereas (Al + Na):Si substitution creates nonbridging oxygen species. Charge compensator preferences were found for Si-[NBO] (Na+), [3]B-[NBO] (Na+), [4]B (mostly Ca2+), [4]Al (nearly equally split Na+ and Ca2+), and [6]Zr (mostly Ca2+). The network former-BO-network former linkages preferences were also tabulated; Si-O-Al and Al-O-Al were preferred at the expense of lower Si-O-[3]B and [3]B-O-[3]B linkages. These results provide insights on the structural origins of property changes such as glass-transition temperature caused by the substitutions, providing a basis for future improvements of theoretical and computer simulation models. 相似文献
123.
Ambreen Nisar Tyler Dolmetsch Tanaji Paul Cheng Zhang Benjamin Boesl Arvind Agarwal 《Journal of the American Ceramic Society》2021,104(6):2483-2494
The application of ultra-high-temperature ceramics (UHTCs) demands effective ways of joining in overcoming the problems associated with the fabrication of complex-shaped components. In this study, we choose to investigate a new method of rapidly joining pre-sintered TaC and HfC ceramics without any filler material using the spark plasma sintering (SPS) technique. A well-bonded TaC–HfC interface was observed with no apparent cracking and porosity at the joint. The joining mechanisms were predominantly driven by solid-state diffusion and localized plastic deformation. The nanomechanical properties of the TaC-HfC joint are better than the HfC while comparable to that of the TaC. High-load indentation (up to 200 N) results suggest that the TaC–HfC interface is stronger than the parent UHTCs with no crack propagating at the interface. Upon comparison with the parent UHTCs, the damaged area and the average crack length at the interface, reduced up to ~94% and ~56%, respectively. This study shows that the SPS technique can also apply to joining other UHTCs without any filler, resulting in the new field of developing complex components for the thermal protection system (TPS). 相似文献
124.
Tuberculosis (TB) is one of the deadliest diseases known to man and ranks among the top ten global causes of fatalities. Children often develop a paucibacillary form of this disease which makes diagnosis arduous even with the aid of sophisticated techniques. In these cases, the concentration of bacteria in their sputum falls below the lowest limit of detection for sputum smear microscopy, the technique predominantly used in developing countries. In this study we aim to test the hypothesis that modifying a polymer, often used in buccal swabs, could assist in creating a capturing and concentrating oral swab for Mycobacterium tuberculosis (Mtb), the pathogenic bacterial species responsible for TB. Such a device will assist in meeting the detection limit and allow for rapid detection of the disease. The polymer used was a micro fibrous form of poly(ethylene terephthalate) (PET) which was surface functionalized with Concanavalin A (Con A), a lectin based adhesin with an affinity for the mannose groups on the Mtb cell wall. The functionalization was mediated with glutaraldehyde as bioconjugate molecule and found to produce a surface uniformly covered with Con A. Affinity studies between the modified fibers and the Mycobacterium bovis bacillus Calmette-Guérin (BCG), as Mtb mimic, were conducted to evaluate the capturing abilities of the substrate. The results indicate that the fibers avidly captured BCG and that the fibrous matrix aided in its function. Dilution studies showed successful capturing of the bacterial species at concentrations characteristic of paucibacillary cases. In this study a commercial polymeric material was successfully surface modified with a biological entity to create a substrate to which Mtb could adhere and accordingly be captured. 相似文献
125.
126.
介绍了包钢CSP厂通过成分调整和工艺优化,研究出适合冷轧生产的热轧低碳钢带生产工艺。IM时通过严格加热炉热工制度和换辊制度等,解决了CSP工艺生产的冷轧用低碳钢热带的表面质量问题,用其生产的冷带成形性能优良,可作为深冲、超深冲使用。 相似文献
127.
铍青铜形变时效工艺的优化 总被引:4,自引:1,他引:4
用正交试验的方法 ,对铍青铜形变时效工艺进行了优选。试验表明 ,控制冷变形度、时效温度和时效时间 ,可获得高的硬度 ,优化后的铍青铜形变时效工艺为 :37%冷变形 + 2 90℃× 2h。 相似文献
128.
ZA27合金的微观组织 总被引:35,自引:2,他引:35
用SEM和TEM对金属型铸造并经 18个月自然时效的ZA2 7合金的微观组织进行了观察。结果表明 :ZA2 7合金凝固的初生相为富Al的树枝状α′相 ,随后在α′相周围形成一层富Zn的包晶 β相 ,最后剩余液体发生共晶反应 ,共晶 β优先依附于包晶 β相形核、长大 ,而共晶 η则在包晶 β相间形成一层薄膜 ,在有些区域则形成棒状共晶组织 ;在随后的冷却及时效过程中 ,β发生胞状分解形成规则的共析α η层片组织或不规则的复杂形状组织 ,共析胞以共晶 η相为基形核 ,并向枝晶中心生长 ,使α′相也分解为层片α η组织 ,当其生长被α′中心的连续分解所阻挡时 ,致使其芯部形成细小的α η颗粒组织 ;富Cu的ε相存在于所有 η相中 相似文献
129.
130.