全文获取类型
收费全文 | 76242篇 |
免费 | 7573篇 |
国内免费 | 4144篇 |
专业分类
电工技术 | 4901篇 |
技术理论 | 3篇 |
综合类 | 5339篇 |
化学工业 | 11794篇 |
金属工艺 | 4677篇 |
机械仪表 | 5115篇 |
建筑科学 | 6090篇 |
矿业工程 | 2117篇 |
能源动力 | 2118篇 |
轻工业 | 5697篇 |
水利工程 | 1708篇 |
石油天然气 | 3604篇 |
武器工业 | 723篇 |
无线电 | 9127篇 |
一般工业技术 | 8808篇 |
冶金工业 | 4418篇 |
原子能技术 | 884篇 |
自动化技术 | 10836篇 |
出版年
2024年 | 310篇 |
2023年 | 1339篇 |
2022年 | 2724篇 |
2021年 | 3806篇 |
2020年 | 2784篇 |
2019年 | 2171篇 |
2018年 | 2289篇 |
2017年 | 2742篇 |
2016年 | 2411篇 |
2015年 | 3484篇 |
2014年 | 4343篇 |
2013年 | 5110篇 |
2012年 | 5499篇 |
2011年 | 6089篇 |
2010年 | 5264篇 |
2009年 | 5099篇 |
2008年 | 4957篇 |
2007年 | 4390篇 |
2006年 | 4027篇 |
2005年 | 3236篇 |
2004年 | 2110篇 |
2003年 | 1700篇 |
2002年 | 1597篇 |
2001年 | 1461篇 |
2000年 | 1220篇 |
1999年 | 1208篇 |
1998年 | 1284篇 |
1997年 | 1030篇 |
1996年 | 873篇 |
1995年 | 721篇 |
1994年 | 573篇 |
1993年 | 476篇 |
1992年 | 293篇 |
1991年 | 250篇 |
1990年 | 198篇 |
1989年 | 155篇 |
1988年 | 120篇 |
1987年 | 89篇 |
1986年 | 70篇 |
1985年 | 56篇 |
1984年 | 42篇 |
1983年 | 45篇 |
1982年 | 39篇 |
1981年 | 55篇 |
1980年 | 41篇 |
1979年 | 26篇 |
1978年 | 15篇 |
1977年 | 31篇 |
1976年 | 36篇 |
1975年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Qun Ren Haijun Su Jun Zhang Haifang Liu Weidan Ma Guangrao Fan Di Zhao Min Guo Lin Liu Hengzhi Fu 《Ceramics International》2019,45(6):6632-6638
Directionally solidified microstructures of Al2O3-Er3Al5O12 eutectic and off-eutectic in situ composite ceramics were explored under abrupt-change pulling rate conditions. Corresponding temperature distributions and interface locations were studied. In eutectic composition, fluctuation of eutectic spacing occurred when the pulling rate increased abruptly. A gradually increase or abrupt increase in eutectic spacing was observed when the pulling rate decreased abruptly. In hypoeutectic and hypereutectic compositions, formation of the primary phases were suppressed when the pulling rate increased abruptly from 10?µm/s to 100?µm/s, while primary phases precipitated when the pulling rate decreased abruptly from 100?µm/s to 10?µm/s. The interface altitude decreased after the pulling rate increased abruptly, but increased after the pulling rate decreased abruptly. The liquid composition restriction (around the eutectic composition) at the eutectic interface plays an important role in the suppression of the primary dendrite and coupled eutectic oxides can be obtained in off-eutectic compositions even under higher solidification rate conditions. 相似文献
52.
53.
54.
55.
Dr. Li Di Prof. Per Artursson Dr. Alex Avdeef Prof. Leslie Z. Benet Prof. J. Brian Houston Dr. Manfred Kansy Edward H. Kerns Prof. Hans Lennernäs Dr. Dennis A. Smith Prof. Kiyohiko Sugano 《ChemMedChem》2020,15(20):1862-1874
Passive permeability is a key property in drug disposition and delivery. It is critical for gastrointestinal absorption, brain penetration, renal reabsorption, defining clearance mechanisms and drug-drug interactions. Passive diffusion rate is translatable across tissues and animal species, while the extent of absorption is dependent on drug properties, as well as in vivo physiology/pathophysiology. Design principles have been developed to guide medicinal chemistry to enhance absorption, which combine the balance of aqueous solubility, permeability and the sometimes unfavorable compound characteristic demanded by the target. Permeability assays have been implemented that enable rapid development of structure-permeability relationships for absorption improvement. Future advances in assay development to reduce nonspecific binding and improve mass balance will enable more accurately measurement of passive permeability. Design principles that integrate potency, selectivity, passive permeability and other ADMET properties facilitate rapid advancement of successful drug candidates to patients. 相似文献
56.
57.
从硬件和软件两个角度出发,介绍基于DSP的多元数据同步采集与存储系统的组成、工作模式以及功能的测试。系统主要由上位机和数字采集与存储单元组成,其中数字采集与存储单元的硬件部分包括电源模块,值班电路模块,数据采集模块,数据存储模块,时钟同步模块。系统采用DSP作为中央处理芯片,利用经过同步后的秒脉冲作为触发信号,实现同步数据采集。以CF卡作为存储介质,实现数据自容式存储。软件部分实现自检、同步、数据采集存储功能。经过测试,系统工作稳定,功能正常,同步精度在100ns以内。 相似文献
58.
Timothy Zurrer Kenneth Wong Jonathan Horlyck Emma C. Lovell Joshua Wright Nicholas M. Bedford Zhaojun Han Kang Liang Jason Scott Rose Amal 《Advanced functional materials》2021,31(9):2007624
The vast chemical and structural tunability of metal–organic frameworks (MOFs) are beginning to be harnessed as functional supports for catalytic nanoparticles spanning a range of applications. However, a lack of straightforward methods for producing nanoparticle-encapsulated MOFs as efficient heterogeneous catalysts limits their usage. Herein, a mixed-metal MOF, NiMg-MOF-74, is utilized as a template to disperse small Ni nanoclusters throughout the parent MOF. By exploiting the difference in Ni O and Mg O coordination bond strength, Ni2+ is selectively reduced to form highly dispersed Ni nanoclusters constrained by the parent MOF pore diameter, while Mg2+ remains coordinated in the framework. By varying the ratio of Ni to Mg in the parent MOF, accessible surface area and crystallinity can be tuned upon thermal treatment, influencing CO2 adsorption capacity and hydrogenation selectivity. The resulting Ni nanoclusters prove to be an active catalyst for CO2 methanation and are examined using extended X-ray absorption fine structure and X-ray photoelectron spectroscopy. By preserving a segment of the Mg2+-containing MOF framework, the composite system retains a portion of its CO2 adsorption capacity while continuing to deliver catalytic activity. The approach is thus critical for designing materials that can bridge the gap between carbon capture and CO2 utilization. 相似文献
59.
Francesco Di Girolamo Andrea Masotti Isabella Lante Margherita Scapaticci Cosima Damiana Calvano Carlo Zambonin Maurizio Muraca Lorenza Putignani 《International journal of molecular sciences》2015,16(9):20896-20912
Extra virgin olive oil (EVOO) with its nutraceutical characteristics substantially contributes as a major nutrient to the health benefit of the Mediterranean diet. Unfortunately, the adulteration of EVOO with less expensive oils (e.g., peanut and corn oils), has become one of the biggest source of agricultural fraud in the European Union, with important health implications for consumers, mainly due to the introduction of seed oil-derived allergens causing, especially in children, severe food allergy phenomena. In this regard, revealing adulterations of EVOO is of fundamental importance for health care and prevention reasons, especially in children. To this aim, effective analytical methods to assess EVOO purity are necessary. Here, we propose a simple, rapid, robust and very sensitive method for non-specialized mass spectrometric laboratory, based on the matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS) coupled to unsupervised hierarchical clustering (UHC), principal component (PCA) and Pearson’s correlation analyses, to reveal corn oil (CO) adulterations in EVOO at very low levels (down to 0.5%). 相似文献
60.
通过对粉煤灰砖抗折强度测量结果不确定度的评定,分析出影响试验结果的各种因素,为提高检测水平和精确度提供指导。 相似文献