全文获取类型
收费全文 | 312篇 |
免费 | 13篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 14篇 |
化学工业 | 117篇 |
金属工艺 | 8篇 |
机械仪表 | 11篇 |
建筑科学 | 9篇 |
能源动力 | 12篇 |
轻工业 | 21篇 |
石油天然气 | 1篇 |
无线电 | 26篇 |
一般工业技术 | 52篇 |
冶金工业 | 5篇 |
原子能技术 | 12篇 |
自动化技术 | 40篇 |
出版年
2022年 | 1篇 |
2021年 | 3篇 |
2020年 | 2篇 |
2019年 | 6篇 |
2018年 | 2篇 |
2017年 | 12篇 |
2016年 | 7篇 |
2015年 | 10篇 |
2014年 | 10篇 |
2013年 | 20篇 |
2012年 | 14篇 |
2011年 | 16篇 |
2010年 | 21篇 |
2009年 | 21篇 |
2008年 | 20篇 |
2007年 | 15篇 |
2006年 | 6篇 |
2005年 | 8篇 |
2004年 | 13篇 |
2003年 | 8篇 |
2002年 | 9篇 |
2001年 | 8篇 |
2000年 | 3篇 |
1999年 | 12篇 |
1998年 | 7篇 |
1997年 | 10篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 8篇 |
1992年 | 7篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 7篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1973年 | 2篇 |
排序方式: 共有328条查询结果,搜索用时 15 毫秒
31.
32.
Kenji Iwase Kazuhiro Mori Akinori Hoshikawa Toru Ishigaki 《International Journal of Hydrogen Energy》2012
The crystal structure and hydrogenation properties of Ce2Ni7-type Gd2Ni7 were investigated by X-ray diffraction (XRD) and the hydrogen pressure–composition (P–C) isotherm. Ce2Ni7-type Gd2Ni7 was obtained by annealing at 1523 K for 12 h and quenching in ice water. Two superlattice reflections (002 and 004) of the Ce2Ni7-type were clearly observed at 2θ = 7.3° and 14.6° in the XRD profile. The refined lattice parameters were a = 0.49662(9) nm and c = 2.4255(3) nm, respectively. Two plateaus were clearly observed during the absorption–desorption process in the P–C isotherm. The first and second plateaus were at 0.015 and 0.13 MPa, respectively, in the first desorption. The maximum hydrogen capacity reached was 1.13 H/M. The enthalpy and entropy were calculated as −20 kJ/mol H2 and −80 J/mol H2 K, respectively, from the van’t Hoff plot. After the P–C isotherm, the GdNi5 cell expanded by 2.15%, but the Gd2Ni4 cell shrank by 2.83%. 相似文献
33.
Primbs T Simonich S Schmedding D Wilson G Jaffe D Takami A Kato S Hatakeyama S Kajii Y 《Environmental science & technology》2007,41(10):3551-3558
To estimate the emissions of anthropogenic semivolatile organic compounds (SOCs) from East Asia and to identify unique SOC molecular markers in Asian air masses, high-volume air samples were collected on the island of Okinawa, Japan between 22 March and 2 May 2004. Contributions from different source regions (China, Japan, the Koreas, Russia, and ocean/local) were estimated by use of source region impact factors (SRIFs). Elevated concentrations of hexachlorobenzene (HCB), hexachlorcyclohexanes (HCHs), dichlorodiphenyltrichloroethanes (DDTs), and particulate-phase polycyclic aromatic hydrocarbons (PAHs) were attributed to air masses from China. A large proportion of the variation in the current-use pesticides, gas-phase PAHs, and polychlorinated biphenyl (PCB) concentrations was explained by meteorology. Chlordanes showed a technical mixture profile and similar concentrations regardless of source region. alpha/gamma HCH and trans/cis chlordane ratios did not vary significantly with different source regions and had regional averages of 2.5 +/- 1.0 and 1.2 +/- 0.3, respectively. Particulate-phase PAH concentrations were significantly correlated (p value < 0.05) with other incomplete combustion byproduct concentrations, including elemental mercury (Hg0), CO, NOx, black carbon, submicrometer aerosols, and SO2. By use of measured PAH, CO, and black carbon concentrations and estimated CO and black carbon emission inventories, the emission of six carcinogenic particulate-phase PAHs was estimated to be 1518-4179 metric tons/year for Asia and 778-1728 metric tons/year for China, respectively. These results confirm that East Asian outflow contains significant emissions of carcinogenic particulate-phase PAHs. 相似文献
34.
The relation between the structure and the viscoelastic properties of seven kinds of epoxy resins was studied. Seven tetraglycidylethers were synthesized from four-nuclei novolacs in which the positions of methylene linkage or number of kind of substituents were different. These epoxy compounds were cured with diaminodiphenylmethane as a hardener. From the viscoelastic properties of the fully cured resins with the hardener, characteristic properties such as glass transition temperature (Tg), average molecular weight between crosslinking points (M̄c), and front factor (ϕ) were obtained. It was concluded that higher linearity in the main chain of epoxy resins gave a cured resin with a higher Tg, a smaller M̄c, and a larger ϕ. 相似文献
35.
36.
Keisuke Iizuka Masahito Ueda Takuya Takahashi Akinori Yoshimura Masahiro Nakayama 《Advanced Composite Materials》2019,28(1):73-85
A unidirectional carbon fiber reinforced plastic (CFRP) was scanned by an X-ray computed tomography (CT) system. Based on the X-ray CT images, a three-dimensional model with random fiber waviness was developed. Each fiber location was identified in a sectional CT image. Subsequently, the relative displacement of fibers between adjacent sectional CT images was obtained with a digital image correlation method. This procedure was repeated to obtain fiber waviness along the axial direction. The constructed three-dimensional fiber model showed random waviness of each fiber in the unidirectional CFRP. Finite element analysis was performed using the three-dimensional model. Simulation results showed bending and twisting deformations coupled with axial contractions during axial compression, which developed due to fiber waviness. A reduction of the fiber directional Young’s modulus due to fiber random waviness was quantitatively evaluated. 相似文献
37.
This article proposes a novel genetic algorithm (GA) which switches the expression of the solution from a redundant binary
number to a usual binary number. Furthermore, a GA which switches the expression from the Gray code to the usual binary number
is proposed and compared. Comparisons of the performances among five GAs (binary number, redundant binary number, Gray code,
switching from redundant binary number to binary number, switching from Gray code to binary number) are illustrated. The performances
are evaluated by solving some equations. It is confirmed that the proposed GA effectively decreases the error rate. 相似文献
38.
Wei Zhang Kenji Ochi Michiya Fujiki Masanobu Naito Masaaki Ishikawa Kei‐ichi Kaneto Wataru Takashima Akinori Saeki Shu Seki 《Advanced functional materials》2010,20(22):3941-3947
In this paper a simple, casting solution technique for the preparation of two‐dimensional (2D) arrays of very‐high molecular weight (MW) 1D‐Pc supramolecular inorganic polymers is described. The soluble fluoroaluminium tetra‐tert‐butylphthalocyanine (ttbPcAlF) is synthesized and characterized, which can be self‐assembled to form 2D arrays of very‐high‐MW 1D‐Pc supramolecular inorganic polymers. High‐resolution transmission electron microscopy (HRTEM) demonstrates that the 1D‐ttbPcAlF, having a cofacial ring spacing of ~0.36 nm and an interchain distance of ~1.7 nm, self‐assembles into 2D‐nanosheets (~140 nm in length, ~20 nm in width, and equivalent to MW of 3.2 × 105 g mol?1). The film cast from a 1,2‐dichloroethane (DCE) solution shows a minimum hole‐mobility of ~0.3 cm2 V?1 s?1 at room temperature by flash‐photolysis time‐resolved microwave conductivity (TRMC) measurements and a fairly high dark dc‐conductivity of ~1 × 10?3 S cm?1. 相似文献
39.
Kishine K. Fujimoto K. Kusanagi S. Ichino H. 《Solid-State Circuits, IEEE Journal of》2004,39(5):740-750
A design technique for an over-10-Gb/s clock and data recovery (CDR) IC provides good jitter tolerance and low jitter. To design the CDR using a PLL that includes a decision circuit with a certain phase margin affecting the pull-in performance, we derived a simple expression for the pull-in range of the PLL, which we call the "limited pull-in range," and used it for the pull-in performance evaluation. The method allows us to quickly and easily compare the pull-in performance of a conventional PLL with a full-rate clock and a PLL with a half-rate clock, and we verified that the half-rate PLL is advantageous because of its wider frequency range. For verification of the method, we fabricated a half-rate CDR with a 1:16 DEMUX IC using commercially available Si bipolar technology with f/sub T/=43 GHz. The half-rate clock technique with a linear phase detector, which is adopted to avoid using the binary phase detector often used for half-rate CDR ICs, achieves good jitter characteristics. The CDR IC operates reliably up to over 15 Gb/s and achieves jitter tolerance with wide margins that surpasses the ITU-T specifications. Furthermore, the measured jitter generation is less than 0.4 ps rms, which is much lower than the ITU-T specification. In addition, the CDR IC can extract a precise clock signal under harsh conditions, such as when the bit error rate of input data is around 2/spl times/10/sup -2/ due to a low-power optical input of -24 dBm. 相似文献
40.
A loop parameter optimization method for a phase-locked loop (PLL) used in wide area networks (WANs) is proposed as a technique for achieving good jitter characteristics. It is shown that the jitter characteristics of the PLL, especially jitter transfer and jitter generation, depend strongly on the key parameter ζωn (ζ is a damping factor and ωn is the natural angular frequency of the PLL), and that the optimization focusing on the ωn dependence of the jitter characteristics make it possible to comprehensively determine loop parameters and loop filter constants for a PLL that will fully comply with ITU-T jitter specifications. Using the optimization method with the low-jitter circuit design technique, a low-jitter and low-power 2.5-Gb/s optical receiver IC integrated with a limiting amplifier, clock and data recovery (CDR), and demultiplexer (DEMUX) is fabricated using 0.5-μm Si bipolar technology (fT = 40 GHz). The jitter characteristics of the IC meet all three types of jitter specifications given in ITU-T recommendation G.783. In particular, the measured jitter generation is 3.2 ps rms, which is lower than that of an IC integrated with only a CDR in our previous work. In addition, the pull-in range of the PLL is 50 MHz and the power consumption of the IC is only 0.68 W (limiting amplifier: 0.2 W, CDR (PLL): 0.3 W, DEMUX: 0.18 W) at a supply voltage of -3.3 V and only 0.35 W at a supply voltage of -2.5 V (without output buffers) 相似文献