全文获取类型
收费全文 | 140435篇 |
免费 | 5626篇 |
国内免费 | 2980篇 |
专业分类
电工技术 | 4361篇 |
技术理论 | 3篇 |
综合类 | 6155篇 |
化学工业 | 20811篇 |
金属工艺 | 8054篇 |
机械仪表 | 6793篇 |
建筑科学 | 6691篇 |
矿业工程 | 2378篇 |
能源动力 | 2768篇 |
轻工业 | 7319篇 |
水利工程 | 2290篇 |
石油天然气 | 4265篇 |
武器工业 | 524篇 |
无线电 | 15352篇 |
一般工业技术 | 22985篇 |
冶金工业 | 5202篇 |
原子能技术 | 830篇 |
自动化技术 | 32260篇 |
出版年
2024年 | 262篇 |
2023年 | 1041篇 |
2022年 | 1772篇 |
2021年 | 2429篇 |
2020年 | 1949篇 |
2019年 | 1577篇 |
2018年 | 15925篇 |
2017年 | 15098篇 |
2016年 | 11481篇 |
2015年 | 2872篇 |
2014年 | 3180篇 |
2013年 | 3482篇 |
2012年 | 6682篇 |
2011年 | 13323篇 |
2010年 | 11667篇 |
2009年 | 8717篇 |
2008年 | 9899篇 |
2007年 | 10679篇 |
2006年 | 3174篇 |
2005年 | 3753篇 |
2004年 | 2947篇 |
2003年 | 2778篇 |
2002年 | 2135篇 |
2001年 | 1483篇 |
2000年 | 1466篇 |
1999年 | 1580篇 |
1998年 | 1333篇 |
1997年 | 1144篇 |
1996年 | 1046篇 |
1995年 | 835篇 |
1994年 | 676篇 |
1993年 | 488篇 |
1992年 | 432篇 |
1991年 | 285篇 |
1990年 | 212篇 |
1989年 | 165篇 |
1988年 | 130篇 |
1987年 | 82篇 |
1986年 | 68篇 |
1985年 | 44篇 |
1984年 | 35篇 |
1968年 | 43篇 |
1966年 | 42篇 |
1965年 | 45篇 |
1959年 | 36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 0 毫秒
51.
旋风燃烧器冷态模型内颗粒运动轨迹计算 总被引:2,自引:0,他引:2
在冷态模型流场内,考虑气流对粉煤颗粒的气动阻力,建立其运动微分方程式。通过计算,得到九种粒径的颗粒在流场中的运动轨迹、停留时间、着膜位置和气-固相相对速度与该燃烧器几何参数和气动参数的关系,为燃烧器的深入研究提出了建议。 相似文献
52.
53.
本文从流变学的观点出发,分析粘合剂在配制及粘结过程中,反映出不同的流变特性,而粘合剂本身的流动、粘度、触变性与涂胶及其粘合的质量关系重大。 相似文献
54.
人体内微量元素含量平衡与否与人体健康状态有着密切关系已为大量实践所证实。人体血液中微量元素的正常值测定是研究人体健康与微量元素关系的一项基础性工作,本文提供了天津市正常人全血及血清中几种微量元素含量的数据。 相似文献
55.
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
56.
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
57.
Sun Zijun He Xiong Liu Jinghua Liu Baosheng Li Hongda Jia Xiaobo Yu Zhiqiang Chang Haixin 《Catalysis Letters》2021,151(11):3135-3144
Catalysis Letters - Hematite (α-Fe2O3) is a potential photoanode material for photoelectrochemical (PEC) water splitting, but its short hole diffusion length and low water oxidation kinetics... 相似文献
58.
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
59.
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
60.