全文获取类型
收费全文 | 3731篇 |
免费 | 104篇 |
国内免费 | 76篇 |
专业分类
电工技术 | 109篇 |
综合类 | 40篇 |
化学工业 | 1027篇 |
金属工艺 | 64篇 |
机械仪表 | 338篇 |
建筑科学 | 71篇 |
矿业工程 | 12篇 |
能源动力 | 355篇 |
轻工业 | 472篇 |
水利工程 | 5篇 |
石油天然气 | 23篇 |
武器工业 | 3篇 |
无线电 | 306篇 |
一般工业技术 | 332篇 |
冶金工业 | 50篇 |
原子能技术 | 199篇 |
自动化技术 | 505篇 |
出版年
2024年 | 1篇 |
2023年 | 52篇 |
2022年 | 101篇 |
2021年 | 102篇 |
2020年 | 103篇 |
2019年 | 48篇 |
2018年 | 78篇 |
2017年 | 80篇 |
2016年 | 135篇 |
2015年 | 115篇 |
2014年 | 205篇 |
2013年 | 328篇 |
2012年 | 237篇 |
2011年 | 325篇 |
2010年 | 291篇 |
2009年 | 231篇 |
2008年 | 197篇 |
2007年 | 158篇 |
2006年 | 122篇 |
2005年 | 118篇 |
2004年 | 102篇 |
2003年 | 73篇 |
2002年 | 75篇 |
2001年 | 79篇 |
2000年 | 69篇 |
1999年 | 50篇 |
1998年 | 74篇 |
1997年 | 45篇 |
1996年 | 37篇 |
1995年 | 49篇 |
1994年 | 35篇 |
1993年 | 16篇 |
1992年 | 32篇 |
1991年 | 38篇 |
1990年 | 24篇 |
1989年 | 14篇 |
1988年 | 13篇 |
1987年 | 10篇 |
1986年 | 8篇 |
1985年 | 14篇 |
1984年 | 11篇 |
1983年 | 5篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有3911条查询结果,搜索用时 24 毫秒
21.
毕远宏 《电脑与微电子技术》2012,(11):3-6
有限颗粒法是一种新的颗粒跟踪法,特别适合模拟污染物的运移过程。用有限颗粒法对多孔介质中纵向弥散度进行识别。纵向弥散度是表征含水层中介质弥散特征的重要参数.也是一个很难确定的参数。给出具体算例,并做进一步的讨论。 相似文献
22.
In recent years, there has been a considerable growth of application of group technology in cellular manufacturing. This has led to investigation of the primary cell formation problem (CFP), both in classical and soft-computing domain. Compared to more well-known and analytical techniques like mathematical programming which have been used rigorously to solve CFPs, heuristic approaches have yet gained the same level of acceptance. In the last decade we have seen some fruitful attempts to use evolutionary techniques like genetic algorithm (GA) and Ant Colony Optimization to find solutions of the CFP. The primary aim of this study is to investigate the applicability of a fine grain variant of the predator-prey GA (PPGA) in CFPs. The algorithm has been adapted to emphasize local selection strategy and to maintain a reasonable balance between prey and predator population, while avoiding premature convergence. The results show that the algorithm is competitive in identifying machine-part clusters from the initial CFP matrix with significantly less number of iterations. The algorithm scaled efficiently for large size problems with competitive performance. Optimal cluster identification is then followed by removal of the bottleneck elements to give a final solution with minimum inter-cluster transition cost. The results give considerable impetus to study similar NP-complete combinatorial problems using fine-grain GAs in future. 相似文献
23.
Cell处理器是一款异构多核处理器,拥有强大的计算能力。但是,在进行应用并行化时,却受到本地存储器容量、访存带宽和数据传输延时等的限制。DMA传输是隐藏长延时、提高存储带宽利用率的有效方法。本文在分析Cell处理器结构基础上,进行了一系列详细的DMA测试,并利用指数拟合技术得到DMA平均带宽模型,发现参与DMA传输的SPE数量和每次DMA传输规模是影响DMA访存带宽的主要因素。 相似文献
24.
Wenlu Song Rui Huang Hao Guo Chunguang Yin Chuanling Wang Jun Cheng Weijuan Yang 《中国化学工程学报》2021,37(9):114-120
Steam pretreatment was employed to disrupt microalgal cells for lipids extraction.Effects of steam pre-treatment on microstructure of microalgal cells were investigated through scanning electron microscopy(SEM) and transmission electron microscopy (TEM).Effect of treatment on lipid extraction was also stud-ied.Microalgal cell walls were distorted after steam pretreatment due to the hydrolysis of organic macro-molecules contained in cell wall.Maximum curvature was increased from 1.88 × 10-6 m-1 to 1.43 × 10-7 m-1 after treatment with the steam at 130 ℃.The fractal dimension of microalgal cells increased from 1.25 to 1.30 after pretreatment for 15 min,and further increased to 1.47 when the pre-treatment time was increased to 60 min.Increased steam pretreatment temperature and time enhanced the hydrolysis of organic macromolecules,and finally destroyed microalgal cell walls at pretreatment temperature of 130 ℃ and pretreatment time of 60 min.Lipid extracted from wet microalgal was signif-icantly increased (2.1-fold) after pretreatment. 相似文献
25.
Jian Zhou 《Electrochimica acta》2003,48(18):2571-2582
The effect on cycle capacity is reported of cathode material (metal oxide, carbon, and current collector) in lithium/metal oxide cells cycled with fumed silica-based composite electrolytes. Three types of electrolytes are compared: filler-free electrolyte consisting of methyl-terminated poly(ethylene glycol) oligomer (PEGdm, Mw=250)+lithium bis(trifluromethylsufonyl)imide (LiTFSI) (Li:O=1:20), and two composite systems of the above baseline liquid electrolyte containing 10-wt% A200 (hydrophilic fumed silica) or R805 (hydrophobic fumed silica with octyl surface group). The composite electrolytes are solid-like gels. Three cathode active materials (LiCoO2, V6O13, and LixMnO2), four conducting carbons (graphite Timrex® SFG 15, SFG 44, carbon black Vulcan XC72R, and Ketjenblack EC-600JD), and three current collector materials (Al, Ni, and carbon fiber) were studied. Cells with composite electrolytes show higher capacity, reduced capacity fade, and less cell polarization than those with filler-free electrolyte. Among the three active materials studied, V6O13 cathodes deliver the highest capacity and LixMnO2 cathodes render the best capacity retention. Discharge capacity of Li/LiCoO2 cells is affected greatly by cathode carbon type, and the capacity decreases in the order of Ketjenblack>SFG 15>SFG 44>Vulcan. Current collector material also plays a significant role in cell cycling performance. Lithium/vanadium oxide (V6O13) cells deliver increased capacity using Ni foil and carbon fiber current collectors in comparison to an Al foil current collector. 相似文献
26.
Chanho Pak Seung Jae Lee Seol-Ah Lee Hyuk Chang 《Korean Journal of Chemical Engineering》2005,22(2):214-218
To reduce the effect of methanol permeated from the anode, the structure of the cathode was modified from a single layer with
Pt black catalyst to two-layer with PtRh black and Pt black catalysts, respectively. The current density of the direct methanol
fuel cell (DMFC) using the two-layer cathode was improved to 228 mA/cm-2 compared to that (180 mA/cm-2) of the DMFC using the single layer cathode at 0.3 V and 303 K. From the cyclic voltammograms (CVs), it is indicated that
the amount of adsorbates on the metal catalyst in the two-layer cathode is less than that of adsorbates in the single layer
cathode after methanol test. In addition, the adsorbates were removed very rapidly by electrochemical oxidation from the two-layer
cathode. It is suggested fromex situ X-ray absorption near edge structure analysis that the d-electron vacancy of Pt atom in the two-layer cathode is not changed
by the methanol test. Thus, Pt is not covered with the adsorbates, which agrees well with the results of CV. 相似文献
27.
Effect of Mode of Drying on Microstructure of Potato 总被引:2,自引:0,他引:2
Potato v. Irga was subjected to blanching, and thereafter was dried by convection, puff-drying, and freeze-drying. Microstructure of raw, blanched, and dried tissue was analyzed under the light microscope using computer image analysis. It was found that the tissue of the investigated variety is built up from cells much smaller than those described in literature for other cultivars. Blanching caused starch gelatinization and increase of cross-sectional area of cells. There was no evidence of broken cell walls. Convective drying resulted in cell shrinkage and some breaking of cell walls. It was estimated that some 12% of cells lost integrity during drying. Limited disintegration of the tissue caused by convective drying is attributed to small size of cells, large contact area, and high cohesive forces between cells. Puff-drying damaged the tissue much more than the convective drying. The most devastating to tissue microstructure was freeze-drying, probably freezing per se. 相似文献
28.
29.
Electrochemical cell current requirements for toxic organic waste destruction in Ce(IV)-mediated electrochemical oxidation process 总被引:1,自引:0,他引:1
Vasily V. Kokovkin Sang Joon Chung Subramanian Balaji Manickam Matheswaran Il-Shik Moon 《Korean Journal of Chemical Engineering》2007,24(5):749-756
The electrochemical cell for cerium oxidation and reactor for organic destruction are the most important operation units for
the successful working mediated electrochemical oxidation (MEO) process. In this study, electrochemical cells with DSA electrodes
of two types, single stack and double stack connected in series, were used. The performances towards the electrochemical generation
of Ce(IV) in nitric acid media at 80 °C were studied. The current-voltage curves and cerium electrolysis kinetics showed the
dependence on number of cell stacks needed to be connected in series for the destruction of a given quantity of organic pollutant.
The presence of an optimum region for Ce(III) oxidation with a contribution of oxygen evolution, especially at low Ce(III)
concentration (high conversion ratios), was found. The cells were applied for the Ce(IV) regeneration during the organic destruction.
The cell and reactor processes were fitted in a simple model proposed and used to calculate the current needed in terms of
Ce(III) oxidation rate and the number of cell stacks required for maintaining Ce(IV)/Ce(III) ratio at the same level during
the organic destruction. This consideration was based on the kinetic model previously developed by us for the organic destruction
in the MEO process. 相似文献
30.
The first use of nickel foam (NF) as electrocatalytic negative electrode in a polysulfide/bromine battery (PSB) is described. The performance of a PSB employing NF and polyacrylonitrile (PAN)-based carbon felt (CF) as negative and positive electrode materials, respectively, was evaluated by constant current charge-discharge tests in a single cell. Charge/discharge curves of the cell, positive and negative electrodes show that the rapid fall in cell voltage is due to the drop of positive potential caused by depletion of Br2 dissolved in the catholyte at the end of discharge. Cell voltage efficiency was limited by the relatively high internal ohmic resistance drop (iR drop). Polarization curves indicated that both NF and CF have excellent catalytic activity for the positive and negative redox reactions of PSB. The average energy efficiency of the single cell designed in this work could be as high as 77.2% at 40 mA cm−2 during 48 charge-discharge cycles. 相似文献