全文获取类型
收费全文 | 119013篇 |
免费 | 13746篇 |
国内免费 | 8275篇 |
专业分类
电工技术 | 10024篇 |
技术理论 | 1篇 |
综合类 | 11800篇 |
化学工业 | 14804篇 |
金属工艺 | 7315篇 |
机械仪表 | 7226篇 |
建筑科学 | 8432篇 |
矿业工程 | 4628篇 |
能源动力 | 3191篇 |
轻工业 | 13367篇 |
水利工程 | 3658篇 |
石油天然气 | 4216篇 |
武器工业 | 1837篇 |
无线电 | 11285篇 |
一般工业技术 | 9905篇 |
冶金工业 | 12091篇 |
原子能技术 | 1708篇 |
自动化技术 | 15546篇 |
出版年
2024年 | 867篇 |
2023年 | 2346篇 |
2022年 | 4980篇 |
2021年 | 6328篇 |
2020年 | 4506篇 |
2019年 | 3196篇 |
2018年 | 3471篇 |
2017年 | 3892篇 |
2016年 | 3444篇 |
2015年 | 5256篇 |
2014年 | 6465篇 |
2013年 | 7556篇 |
2012年 | 9103篇 |
2011年 | 9388篇 |
2010年 | 8754篇 |
2009年 | 8084篇 |
2008年 | 8182篇 |
2007年 | 7899篇 |
2006年 | 6857篇 |
2005年 | 5375篇 |
2004年 | 3964篇 |
2003年 | 2946篇 |
2002年 | 2745篇 |
2001年 | 2508篇 |
2000年 | 1935篇 |
1999年 | 1166篇 |
1998年 | 3026篇 |
1997年 | 1788篇 |
1996年 | 1195篇 |
1995年 | 728篇 |
1994年 | 624篇 |
1993年 | 626篇 |
1992年 | 183篇 |
1991年 | 176篇 |
1990年 | 163篇 |
1989年 | 151篇 |
1988年 | 116篇 |
1987年 | 99篇 |
1986年 | 97篇 |
1985年 | 62篇 |
1983年 | 25篇 |
1982年 | 48篇 |
1981年 | 48篇 |
1980年 | 81篇 |
1979年 | 23篇 |
1977年 | 158篇 |
1976年 | 286篇 |
1975年 | 16篇 |
1959年 | 40篇 |
1951年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
11.
13.
14.
Lindsey Yue Alicia Bayon Wojciech Lipiński 《American Institute of Chemical Engineers》2021,67(8):e17267
The effects of particle size and carbon dioxide concentration on chemical conversion in engineered spherical particles undergoing calcium oxide looping are investigated. Particles are thermochemically cycled in a furnace under different carbon dioxide concentrations. Changes in composition due to chemical reactions are measured using thermogravimetric analysis. Gas composition at the furnace exit is evaluated with mass spectroscopy. A numerical model of thermal transport phenomena developed previously is adapted to match the physical system investigated in the present study. The model is used to elucidate effects of reacting medium characteristics on particle temperature and reaction extent. Experimental and numerical results show that (1) an increase in particle size results in a decrease in carbonation extent, and (2) the carbonation step consists of fast and slow reaction regimes. The reaction rates in the fast and slow carbonation regimes increase with increasing carbon dioxide concentration. The effect of carbon dioxide concentration and the distinction between the fast and slow regimes become more pronounced with increasing particle size. 相似文献
15.
17.
Xueye Chen Yue Tian 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2020,95(3):806-812
Since the beginning of the 21st Century, the development of microfluidic chip technology has been very rapid and has attracted the attention of more and more scholars. As an important part of the microfluidic chip, the performance of the micromixer is critical. The fractal structure in the microchannels helps to improve the mixing performance of the micromixer and improve the mixing efficiency of the micromixer. The research results of other scholars are of great significance to the research of the present paper, which mainly studies the effect of changing the baffle state on the mixing efficiency of the micromixer based on the Koch fractal principle. Through simulation analysis, it was found that the mixing efficiency of the baffles distributed on both sides of the microchannel was higher than the mixing efficiency of the baffles distributed on the microchannel side. When the distance between adjacent baffles was divided into 0.15, 0.25 and 0.35 mm, simulated data suggested that the baffle distance of 0.15 mm was best. Increasing the number of baffles from six to eight groups increased the mixing path of the fluid in the microchannel and improved mixing efficiency. A comparison of mixing efficiencies of the 0°, 15° and 30° baffle angles revealed that very significant improvement in mixing efficiency was obtained at 30°. © 2019 Society of Chemical Industry 相似文献
18.
反应堆屏蔽计算中经常出现厚屏蔽、小探测器问题,常规蒙特卡罗方法难以有效解决。基于自动重要抽样(AIS)方法,本文提出了小探测器自动重要抽样(SDAIS)方法,并针对小探测器问题,优化了AIS方法的虚粒子赌分裂算法。该方法在自主开发的蒙特卡罗屏蔽程序MCShield上进行了实现。使用NUREG/CR-6115 PWR基准题验证该方法的正确性和计算效率。结果表明,SDAIS方法可有效地解决厚屏蔽小探测器问题,相比AIS方法及传统的重要性方法,计算效率提升1~2个量级。 相似文献
19.
目的:探索炎性疾病患者的乳酸林格氏液(Ringer's lactate,RL)液体动力学特征以及炎性生物标记物是否可以作为协变量影响RL分布和排泄。方法:本研究为前瞻性队列研究。选择40例美国麻醉医师分级(ASA)I-II级,腹腔镜下择期胆囊切除术(胆囊炎组,n=20)或者腹腔镜下急诊阑尾切除术(阑尾炎组,n=20)。所有患者麻醉诱导前开始输注RL,按15 mL/kg,35 min内输毕。采用酶联免疫(enzyme-linked immunosorbent assay,ELISA)方法测定血浆炎症(TNF-α,IL-10和CRP)或者内皮损伤生物标记物(syndecan-1,SDC-1);利用血红蛋白(Hb)稀释-时间曲线和尿量,使用Phoenix软件,采用非线性混合效应模型分析计算RL液体动力学参数和协变量的影响。结果:与胆囊炎组相比,阑尾炎组RL从组织间隙到血浆的转运速率常数(k21)显著降低(14×10-3min-1 versus 35×10-3min-1;P=0.012)。阑尾炎组C反应蛋白(CRP)升高[中位数38.1(1.8-143.6) μg/mL versus 1.3(0.1-159.0) μg/mL;P<0.001];与清醒状态相比,麻醉期间(输液开始后30~45 min),液体从中央室中到外周室的转运速率常数(k12)显著增加(57×10-3min-1 versus 32×10-3min-1;P<0.01)。清除速率常数(k10)降低90%(0.6×10-3min-1 versus 5.3×10-3min-1;P<0.001)。无论在清醒状态还是麻醉状态下低血压均能降低液体清除;炎症或者内膜损伤的生物标记物不能作为显著影响RL液体动力学参数的协变量。结论:阑尾炎或者胆囊炎患者术前输入液体后“炎症反应的生物标记物”不是RL的液体动力学的协变量,但是两组患者中,全身麻醉期间输入液体的清除率下降。 相似文献
20.
Amphotericin B (AMB) was often used in intra-articular injection administration for fungal arthritis, because it could often bring a satisfactory therapeutic efficacy and a minimum systemic toxic side effect. However, because of the multiple operations and the frequent injections, the compliance of the patients was bad. Therefore, to develop a long-term sustained-released preparation of AMB for mycotic arthritis intra-articular administration is of great significance. The purpose of present study was to develop a long-term sustained-released in situ gel of a water-insoluble drug AMB for mycotic arthritis intra-articular administration. Based on the evaluations of the in vitro properties of the formulations, the formulation containing 10% (w/w) ethanol, 15% (w/w) PG, 0.75% (w/w) HA, 5% (w/w) purified soybean oil, 0.03% (w/w) α-tocopherol, 15% (w/w) water and 55% (w/w) glyceryl monooleate was selected as a suitable intra-articular injectable in situ gel drug delivery system for water-insoluble drug AMB. Furthermore, the results of the in vivo study on rabbits showed that the selected formulation was a safe and effective long-term sustained-released intra-articular injectable AMB preparation. Therefore, the presented in situ AMB gel could reduce the frequency of the administration in the AMB treatment of fungal arthritis, and then would get a good patient compliance. 相似文献