全文获取类型
收费全文 | 1860篇 |
免费 | 55篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 112篇 |
综合类 | 4篇 |
化学工业 | 509篇 |
金属工艺 | 38篇 |
机械仪表 | 30篇 |
建筑科学 | 33篇 |
矿业工程 | 3篇 |
能源动力 | 70篇 |
轻工业 | 174篇 |
水利工程 | 3篇 |
石油天然气 | 2篇 |
无线电 | 165篇 |
一般工业技术 | 272篇 |
冶金工业 | 304篇 |
原子能技术 | 56篇 |
自动化技术 | 143篇 |
出版年
2021年 | 36篇 |
2019年 | 17篇 |
2018年 | 34篇 |
2017年 | 23篇 |
2016年 | 32篇 |
2015年 | 30篇 |
2014年 | 25篇 |
2013年 | 92篇 |
2012年 | 59篇 |
2011年 | 79篇 |
2010年 | 62篇 |
2009年 | 69篇 |
2008年 | 64篇 |
2007年 | 82篇 |
2006年 | 81篇 |
2005年 | 59篇 |
2004年 | 49篇 |
2003年 | 45篇 |
2002年 | 37篇 |
2001年 | 42篇 |
2000年 | 41篇 |
1999年 | 42篇 |
1998年 | 105篇 |
1997年 | 66篇 |
1996年 | 55篇 |
1995年 | 40篇 |
1994年 | 50篇 |
1993年 | 48篇 |
1992年 | 31篇 |
1991年 | 19篇 |
1990年 | 17篇 |
1989年 | 28篇 |
1988年 | 22篇 |
1987年 | 18篇 |
1986年 | 13篇 |
1985年 | 19篇 |
1984年 | 13篇 |
1983年 | 14篇 |
1982年 | 18篇 |
1980年 | 14篇 |
1979年 | 15篇 |
1978年 | 13篇 |
1977年 | 13篇 |
1976年 | 22篇 |
1972年 | 15篇 |
1971年 | 13篇 |
1961年 | 12篇 |
1960年 | 12篇 |
1958年 | 12篇 |
1957年 | 13篇 |
排序方式: 共有1918条查询结果,搜索用时 15 毫秒
101.
Guoqing Guan Katsuki Kusakabe Haruka Ozono Masatsugu Taneda Masato Uehara Hideaki Maeda 《Journal of Materials Science》2007,42(24):10196-10202
Three-dimensionally (3D) well-ordered carbon microparticle assemblies with different particle morphologies were fabricated
by infiltration of phenolic resin solution into SiO2 inverse opal structures and subsequent carbonization. The effect of the phenolic resin solution concentration and the carbonization
temperature on the morphology of the fabricated carbon microparticles was investigated. At a carbonization temperature of
1000 °C, carbon microparticles with interlocked bridges were obtained when the concentration of phenolic resin solution is
40 wt% and hollow carbon microparticles with opened window channels were obtained at a concentration of 30–35 wt%. When the
carbonization temperature was decreased to 500 °C, carbon microparticles with interlocked bridges also were observed, even
when the phenolic resin concentration was 30 wt%. The structures and properties of the carbon microparticles and their assemblies
were characterized using SEM, XRD, and N2 adsorption. 相似文献
102.
Takashi Kojima Yasuki Mori Masahiro Kamiya Ryo Sasai Hideaki Itoh 《Journal of Materials Science》2007,42(15):6056-6061
Capability of the recycling of high strength and high fracture toughness yttria-stabilized tetragonal zirconia polycrystalline
(Y-TZP) sintered body utilizing “low-temperature annealing degradation” phenomenon was investigated. Hydrothermal treatment
was employed to induce the phase transformation from tetragonal to monoclinic zirconia and to disintegrate the Y-TZP sintered
body. 3 mol% Y2O3–ZrO2 specimens sintered at 1,550 °C and more were disintegrated without leaving the original appearances when the treatment temperature
was between 200 °C and 400 °C. The size of the disintegrated fragments of Y-TZP sintered body was much affected by hydrothermal
treatment conditions. Only with hydrothermal treatment and simple ball milling, the sintered body was pulverized into the
primary particle level. This technique is expected to apply to a sustainable recycling system for the zirconia ceramics, which
restrains an energy consumption compared to crushing zirconia using mechanical procedures. 相似文献
103.
This paper proposes a mechanism that adjusts mechanical stiffness around a robot joint and utilizes whole elastic energy of an elastic element. The proposed mechanism consists of a lead screw mechanism, a linear spring, and wires. The lead screw mechanism moves a nut of the lead screw mechanism to change a bending point of the wire, which connects the linear spring and the lead screw mechanism. Then, moment arm and ratio of joint rotation to extension of the spring are varied. As a result, joint stiffness is adjusted. Because this mechanism does not apply tension to the spring for the stiffness adjustment, whole elastic energy of the spring can be utilized for joint rotation. This utilization can minimize weight and size of the elastic element. Additional advantages of the proposed mechanism are mechanical simplicity, wide range of adjustable stiffness, and no energy consumption for keeping constant stiffness. We analyze characteristics of the proposed mechanism and compare with other mechanisms in detail. Device development and experimental results are provided for demonstrating the effectiveness of the proposed mechanism. 相似文献
104.
Spatial and Temporal Analysis of Hydrological Provision Ecosystem Services for Watershed Conservation Planning of Water Resources 总被引:1,自引:0,他引:1
Spatial planning for sustainable water resources development requires precise information on the local potential for providing water yield in a watershed. For water resource conservation, we analyzed spatial and temporal patterns of hydrological provision ecosystem services in the upper Teshio watershed of northernmost Japan. The Soil and Water Assessment Tool (SWAT) was applied to simulate hydrologic processes and determine parameters affecting the water cycle. The spatial increase of water yield at flat area near river channel in winter was explained by low field capacity of soil water, absence of water uptake by crops and gentle topography. The spatial patterns of snowmelt and rainfall were important drivers of the spatial pattern in water yield during other periods. The zonation model was applied to investigate dynamic changes in spatial conservation prioritization of hydrological provision ecosystem services, according to simulated water yields in February, April and October. The results showed that the conservation priority ranking dynamically changed spatially and temporally. Our economic assessment of hydrological provisioning services (irrigation, electricity production and household usage) indicated that the spatial pattern of the priority for water resources was different from that of economic value of the provisioning services. Our results indicated that a combination of hydrologic and cost zonation models would improve sustainable management planning of water resources and their hydrological ecosystem services have great spatiotemporal fluctuation. 相似文献
105.
Future networks must offer extremely high levels of reliability because information has become critical to the continued well-being of society. This article shows the approaches to the survivable ATM network. The reliability requirements of future networks are discussed first. Development results of three typical restoration architectures (automatic protection switch (APS), self-healing network (SHN), and failure-resistant virtual path (FRVP)) for ATM networks are then shown. Next, we describe current progress in standardization activities. They also discuss open issues that must be resolved in future studies 相似文献
106.
Hideki Yamamoto Kimito Kawamura Kazunobu Omura Shogo Tokudome 《International Journal of Thermophysics》2010,31(11-12):2361-2379
A compact-sized falling needle rheometer with rapid operation and automatic flow analysis has been developed for viscometry of fresh human blood without anticoagulant. The volume of a fresh blood sample only needs to be 3 mL, and the measuring time is within 2 min after taking a blood sample from the human body. Measured flow properties of human blood are evaluated as a flow curve, that is, the relationship between the shear stress (τ) and shear rate (γ). Observed flow curves of fresh human blood show three typical fluid regions, that is, the Casson fluid region for a low shear rate range of 0 < γ > 140 s?1, the transition region for a shear rate near 140 s?1 < γ < 160 s?1, and the Newtonian fluid region for a high shear rate range of 160 s?1 < γ > 400 s?1. Flow properties of human blood such as the yield stress (τ y) in the Casson fluid region and the apparent viscosity (μ) in the Newtonian fluid region are measured, and they are compared between male and female blood. It is found that the range of human blood viscosity for males is (5.5 to 6.4) mPa · s, and for females is (4.5 to 5.3) mPa · s. The viscosities of male blood without anticoagulant show higher values than those of female blood. Human blood viscosities with anticoagulant show a lower value than that without anticoagulant. A linear relationship between the hematocrit value, that is, the volume percentage of red corpuscles in the human blood, and the apparent viscosity are observed for both male and female blood. This article is concerned with the flow analysis of fresh human blood viscosity without anticoagulant using a newly developed compact-sized falling needle rheometer. 相似文献
107.
Yuzo Nishida Satoshi Nishino Li Li Guo Mami Kunita Hideaki Matsushima Tadashi Tokii 《Inorganic chemistry communications》1999,2(12):160
We have observed that binuclear cobalt(II) compounds with H(HPTP), Co2(HPTP)(CH3COO)(ClO4)2 and Co2(HPTP)Cl(ClO4)2, react with oxygen molecules when DNA is present in the solution, cleaving the DNA (H(HPTP) denotes N,N,N′,N′-tetrakis(2-pyridylmethyl)-1,3-diaminopropane-2- ol). 相似文献
108.
Hideaki Yamashita 《IIE Transactions》2001,33(10):889-895
We study automated guided vehicle systems that contain multiple vehicles. Each vehicle transports an item from a certain point to its destination. The inter-arrival time of items to each node is assumed to be independently and geometrically distributed. Each node has an infinite buffer capacity, and thus no item is lost. The deadhead time of the empty vehicle and the transportation time of the loaded vehicle are assumed to be arbitrarily distributed. We propose two empty vehicle dispatching policies, and numerically calculate the waiting time distributions of the items for each policy using a state-space reduction technique for Markov chains. Several examples are given to demonstrate the advantages and disadvantages of each policy. 相似文献
109.
Room-temperature excitonic resonances in the optical absorption spectrum of InGaP/lnGaAlP multiquantum wells (MQWs) are observed for the first time. Well resolved heavyhole and light-hole excitons are observed at 100K. From the step-like structure of the absorption spectrum, the conduction-band discontinuity ?Ec is estimated to be 0.46 of the bandgap difference ?Eg. 相似文献
110.