全文获取类型
收费全文 | 149770篇 |
免费 | 8275篇 |
国内免费 | 4108篇 |
专业分类
电工技术 | 6409篇 |
技术理论 | 8篇 |
综合类 | 7368篇 |
化学工业 | 21127篇 |
金属工艺 | 8817篇 |
机械仪表 | 7250篇 |
建筑科学 | 7658篇 |
矿业工程 | 2910篇 |
能源动力 | 3134篇 |
轻工业 | 7820篇 |
水利工程 | 2868篇 |
石油天然气 | 3694篇 |
武器工业 | 799篇 |
无线电 | 17087篇 |
一般工业技术 | 23515篇 |
冶金工业 | 5428篇 |
原子能技术 | 1165篇 |
自动化技术 | 35096篇 |
出版年
2024年 | 370篇 |
2023年 | 1328篇 |
2022年 | 2773篇 |
2021年 | 3636篇 |
2020年 | 2744篇 |
2019年 | 2092篇 |
2018年 | 16608篇 |
2017年 | 15774篇 |
2016年 | 12194篇 |
2015年 | 3918篇 |
2014年 | 4203篇 |
2013年 | 4864篇 |
2012年 | 8343篇 |
2011年 | 14830篇 |
2010年 | 12903篇 |
2009年 | 9886篇 |
2008年 | 10965篇 |
2007年 | 11560篇 |
2006年 | 3726篇 |
2005年 | 4175篇 |
2004年 | 3113篇 |
2003年 | 2611篇 |
2002年 | 1845篇 |
2001年 | 1149篇 |
2000年 | 1180篇 |
1999年 | 973篇 |
1998年 | 744篇 |
1997年 | 585篇 |
1996年 | 619篇 |
1995年 | 410篇 |
1994年 | 347篇 |
1993年 | 251篇 |
1992年 | 220篇 |
1991年 | 142篇 |
1990年 | 105篇 |
1989年 | 79篇 |
1988年 | 84篇 |
1987年 | 44篇 |
1986年 | 33篇 |
1968年 | 43篇 |
1967年 | 33篇 |
1966年 | 42篇 |
1965年 | 45篇 |
1960年 | 30篇 |
1959年 | 44篇 |
1958年 | 37篇 |
1957年 | 36篇 |
1956年 | 34篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
51.
52.
Peng Dangcong Jin Qiting 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1993,58(1):89-93
The anaerobic digestion of alkaline black liquor from a cereal straw pulping mill was studied in batch (serum bottles) and continuous systems (up-flow anaerobic sludge blanket reactor—UASB). The batch digestion studies confirmed that lignin and related compounds (LRC) in the alkaline black liquor were the main inhibitory substances and could not be decomposed by anaerobic bacteria. At organic loading rates of 5–10 kg COD m?3 day?1, the UASB reactor achieved 50–60% COD removal efficiencies. Gas production was 2–3 dm3 per dm3 of alkaline black liquor. Two different sludge types were examined in the reactor: granular and cluster-like sludges. Sludge in a cluster, which involved many small granules and flocs, tended to form larger aggregates and possessed good settling ability. 相似文献
53.
Many video service sites headed by YouTube know what content requires copyright protection. However, they lack a copyright
protection system that automatically distinguishes whether uploaded videos contain legal or illegal content. Existing protection
techniques use content-based retrieval methods that compare the features of video. However, if the video encoding has changed
in resolution, bit-rate or codec, these techniques do not perform well. Thus, this paper proposes a novel video matching algorithm
even if the type of encoding has changed. We also suggest an intelligent copyright protection system using the proposed algorithm.
This can serve to automatically prevent the uploading of illegal content. The proposed method has represented the accuracy
of 97% with searching algorithm in video-matching experiments and 98.62% with automation algorithm in copyright-protection
experiments. Therefore, this system could form a core technology that identifies illegal content and automatically excludes
access to illegal content by many video service sites. 相似文献
54.
In this paper we have proposed a dynamic pricing scheme for the contributing peers in the Video on Demand (VoD) system. The
scheme provides an effective mechanism to maximize the profit through the residual resources of the contributing peers. A
utilization function is executed for each contributing peer to estimate the utility factor based on the parameters such as
initial setup cost, holding cost, chaining cost and salvage cost. In this paper, we urge an effective dynamic pricing algorithm
that efficiently utilizes a range of parameters with a varying degree of complexity. The key findings of the algorithm are
(i) each contributing peers are benefitted by the monetary based on its resource contributions to the VoD system and (ii)
a high degree of social optimum is established by proficiently aggregating the contributing peer’s resources with the overall
resources of the VoD system. We validate our claim by simulating the proposed dynamic pricing scheme with other standard pricing
schemes such as altruism, cost model and game theory perspective. The result of our dynamic pricing scheme shows the best
utility factor than other standard pricing schemes. 相似文献
55.
Qiu Jun Wang Yueting Wu Peng Jiang Shan Cui Kaibo Chen Guowei Liu Dongliang Cui Guangwen 《Journal of Porous Materials》2021,28(6):1675-1687
Journal of Porous Materials - The dynamics and thermodynamics of adsorption of hexadecyl ammonium with different numbers of carbon chains in montmorillonite (Mt) with different layer charge density... 相似文献
56.
57.
Distortion as a result of the quenching process is predominantly due to the thermal gradient and phase transformations within
the component. Compared with traditional liquid quenching, the thermal boundary conditions during gas quenching are relatively
simple to control. By adjusting the gas-quenching furnace pressure, the flow speed, or the spray nozzle configuration, the
heat-transfer coefficients can be designed in terms of both the component geometry and the quenching time. The purpose of
this research is to apply the optimization methodology to design the gas-quenching process. The design objective is to minimize
the distortion caused by quenching. Constraints on the average surface hardness, and its distribution and residual stress
are imposed. The heat-transfer coefficients are used as design variables. DEFORM-HT is used to predict material response during
quenching. The response surface method is used to obtain the analytical models of the objective function and constraints in
terms of the design variables. Once the response surfaces of the objective and constraints are obtained, they are used to
search for the optimum heat-transfer coefficients. This process is then used instead of the finite-element analysis. A one-gear
blank case study is used to demonstrate the optimization scheme. 相似文献
58.
Jaspreet S. Gandhi William J. van Ooij 《Journal of Materials Engineering and Performance》2004,13(4):475-480
Organofunctional silanes recently have emerged as outstanding, environmentally friendly corrosion protectors for metal substrates,
compared with conventional chromate treatments. A simple immersion technique is typically used to coat the metal surface with
silane films. However, the thickness and uniformity of the films are uncontrolled in this process. This paper proposes a new
deposition technique for the silane films on the metal surface, i.e., by electrodeposition. Hydrolyzed silanes are water-soluble,
ionized molecules, so they can be deposited on metals by electrodeposition. Various combinations of silane mixtures were tested
at different voltages, pH values, bath concentrations, and exposure times on panels of alloy aluminum and mirror-polished
ferro-plate. The surface structure was characterized by scanning electron microscopy (SEM) and ellipsometry. The resistance
of the film to corrosion was investigated by direct current (DC) polarization and electrochemical impedance spectroscopy (EIS)
techniques. Electrodeposition results in a more organized and uniform film with fewer pores, compared with immersed or dipped
films.
This paper was presented at the 2nd International Surface Engineering Congress sponsored by ASM International, on September
15–17, 2003, in Indianapolis, Indiana, and appears on pp. 320–26 of the Proceedings. 相似文献
59.
新型钢包翻包机是九十年代从国外引进的一种专用设备,其以高效、安全、便捷等特点越来越多的应用于大型钢铁厂.本文介绍了160 t翻包机结构与功能. 相似文献
60.
During the last ten years, techniques have been developed to measure the distribution of grain boundaries in polycrystals
as a function of both lattice misorientation and grain boundary plane orientation. This paper presents a brief overview of
the techniques used for these measurements and the principle findings of studies implementing these techniques. The most significant
findings are that grain boundary plane distributions are anisotropic, that they are scale invariant during normal grain growth,
that the most common grain boundary planes are those with low surface energies, that the grain boundary populations are inversely
correlated with the grain boundary energy, and that the coincident site lattice number is a poor predictor of the grain boundary
energy and population. 相似文献