全文获取类型
收费全文 | 10188篇 |
免费 | 1099篇 |
国内免费 | 950篇 |
专业分类
电工技术 | 1010篇 |
综合类 | 1085篇 |
化学工业 | 1426篇 |
金属工艺 | 812篇 |
机械仪表 | 284篇 |
建筑科学 | 806篇 |
矿业工程 | 493篇 |
能源动力 | 598篇 |
轻工业 | 634篇 |
水利工程 | 337篇 |
石油天然气 | 1552篇 |
武器工业 | 65篇 |
无线电 | 584篇 |
一般工业技术 | 993篇 |
冶金工业 | 517篇 |
原子能技术 | 188篇 |
自动化技术 | 853篇 |
出版年
2024年 | 44篇 |
2023年 | 176篇 |
2022年 | 342篇 |
2021年 | 377篇 |
2020年 | 342篇 |
2019年 | 352篇 |
2018年 | 303篇 |
2017年 | 367篇 |
2016年 | 405篇 |
2015年 | 385篇 |
2014年 | 544篇 |
2013年 | 680篇 |
2012年 | 678篇 |
2011年 | 780篇 |
2010年 | 557篇 |
2009年 | 612篇 |
2008年 | 550篇 |
2007年 | 618篇 |
2006年 | 587篇 |
2005年 | 533篇 |
2004年 | 497篇 |
2003年 | 340篇 |
2002年 | 338篇 |
2001年 | 261篇 |
2000年 | 219篇 |
1999年 | 204篇 |
1998年 | 151篇 |
1997年 | 159篇 |
1996年 | 133篇 |
1995年 | 124篇 |
1994年 | 101篇 |
1993年 | 101篇 |
1992年 | 74篇 |
1991年 | 56篇 |
1990年 | 52篇 |
1989年 | 41篇 |
1988年 | 34篇 |
1987年 | 21篇 |
1986年 | 28篇 |
1985年 | 13篇 |
1984年 | 9篇 |
1983年 | 6篇 |
1982年 | 7篇 |
1981年 | 11篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1960年 | 2篇 |
1955年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
Mingxin Yuan Sun-an Wang Canyang Wu Kunpeng Li 《Frontiers of Computer Science in China》2009,3(2):247-255
Inspired by the mechanism of Jerne’s idiotypic network hypothesis, a new adaptive immune network algorithm (AINA) is presented
through the stimulation and suppression between the antigen and antibody by taking the environment and robot behavior as antigen
and antibody respectively. A guiding weight is defined based on the artificial potential field (APF) method, and the guiding
weight is combined with antibody vitality to construct a new antibody selection operator, which improves the searching efficiency.
In addition, an updating operator of antibody vi-tality is provided based on the Baldwin effect, which results in a positive
feedback mechanism of search and accelerates the convergence of the immune network. The simulation and experimental results
show that the proposed algorithm is characterized by high searching speed, good convergence performance and strong planning
ability, which solves the path planning well in complicated environments. 相似文献
102.
Reports an error in the original article by M. A. Small and G. B. Melton (Professional Psychology: Research and Practice, 1994[August], Vol 25[3], 228–233). Footnote 1 incorrectly indicates that the Craig brief was written without the aid of private legal counsel. Though the brief in question was written with more APA member involvement than has been the case for other briefs, private legal counsel participated and was listed as a coauthor. (The following abstract of this article originally appeared in record 1994-43476-001.) States have passed legislation governing the procedures by which children may testify in cases of child abuse. In Maryland v. Craig (1990), the US Supreme Court reviewed the constitutionality of these procedures. As a result, psychologists may be asked to perform evaluations regarding the potential trauma a child faces in confronting a defendant in a criminal case. Specifically, opinions of psychologists may be sought as to the potential trauma a child may endure as a result of a face-to-face confrontation with a defendant. Research relevant to this assessment is reviewed, and it is suggested that psychologists may be of most help in preparing children to testify.… (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
103.
104.
105.
基于分子动力学方法,利用嵌入原子势(EAM)函数,在微观尺度下研究了影响单晶铜熔点的多种因素。首先利用势函数计算单晶铜的晶格常数和弹性常数,以此验证本研究所采用势函数的准确性,然后利用能量体积法、径向分布函数法和键对分析技术对模拟得到的结果进行分析,测得单晶铜熔点约为1 380K。分析了模型大小、升温速率、晶体缺陷对铜熔点的影响,研究发现模型大小、升温速率对熔点的影响不大,随着升温速率的增大,达到熔点所需的时间越短。晶体缺陷的存在使金属材料晶格点阵稳定性下降,熔化需要的热量减少,熔点相应降低,与实际熔点情况一致。 相似文献
106.
Pavement preservation (PP) is a planned set of construction and material interventions that can extend the pavement’s service life and may also impact sustainability through Heat Island (HI) mitigation. The HI mitigation potential can vary from location-to-location and with time. For agencies to widely adopt the PP, it is necessary to quantify the benefits based on the context of the project. A method to calculate the Global Warming Potential (GWP) for the HI effect was developed and illustrated for four cities in the US: Chicago, Austin, San Diego and Philadelphia, for hypothetical pavements with three preservation options: chip seals, a concrete inlay, and an asphalt concrete inlay. The use phase GWP with respect to HI was estimated for all cases given a 2-, 5-, 7- or 10-year service life. Overall, the HI in the use phase was found to dominate the total GWP relative to the materials and construction phases. The HI GWP savings increase over time, with the 10-year savings being greatest for San Diego using the concrete inlay (22.5?kg CO2-eq/m2) and smallest for Chicago with a chip seal (8.0?kg CO2-eq/m2). The savings were found to increase in areas that have a more pronounced HI and could offset GWP in the other phases. The proposed method allows agencies to estimate HI GWP for a specific preservation strategy, location and service life. 相似文献
107.
《材料科学技术学报》2019,35(8):1797-1802
A new insight into the promotion action of Co2+ on both particle and metal deposition in Ni-diamond composite electrodeposition system was analyzed according to electrochemical measurements. The results showed that the addition of Co2+ made particles content in deposits increased remarkably. The change of particles content in deposits was related inversely to the change of cathodic zero potential with the increase of the concentration of cobalt sulfate. Zero charge potential of cathode was shifted to much more negative region. The negative shift of the zero potential, combining with positive shift of the zeta potential, increased the electrostatic force between the particle-adsorbed metallic cations and the cathode. It not only benefits to the transportation of particles in solution towards cathode, but also shortens their residence time on cathodic surface. Meanwhile, entry of particles is also promoted. For metals deposition, reduction resistance of metallic cations rises greatly and deposition current at cathodic potentiodynamic polarization decreases after cobalt sulfate has been added into electrolyte. These factors are favorable for increasing particles content in deposits. In addition, physical model of diamond particles deposition state before and after the addition of Co2+ has been discussed. 相似文献
108.
大脑神经元的活动是在复杂的生理学环境下工作的,而生理学环境中的噪声来源于多个方面.如何定量地正确评估神经系统中的噪声环境是神经信息处理的基本问题.本文通过神经能量的计算给出了噪声对神经元膜电位及对应的能量波形产生显著影响的临界值的估计范围,从而定义了神经元赖以活动的生理学意义上的噪声环境. 相似文献
109.
110.
Potential phase diagrams, where the chemical potential of a compound is used as an axis, do not obey the usual rules for potential phase diagrams. Examples are presented in order to help the interpretation of such diagrams. The thermodynamic background of the special properties is examined. 相似文献