全文获取类型
收费全文 | 5800篇 |
免费 | 160篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 208篇 |
综合类 | 3篇 |
化学工业 | 1115篇 |
金属工艺 | 139篇 |
机械仪表 | 136篇 |
建筑科学 | 110篇 |
矿业工程 | 2篇 |
能源动力 | 151篇 |
轻工业 | 492篇 |
水利工程 | 27篇 |
石油天然气 | 8篇 |
无线电 | 566篇 |
一般工业技术 | 1021篇 |
冶金工业 | 1384篇 |
原子能技术 | 167篇 |
自动化技术 | 440篇 |
出版年
2023年 | 41篇 |
2022年 | 24篇 |
2021年 | 137篇 |
2020年 | 78篇 |
2019年 | 80篇 |
2018年 | 110篇 |
2017年 | 80篇 |
2016年 | 117篇 |
2015年 | 84篇 |
2014年 | 118篇 |
2013年 | 303篇 |
2012年 | 194篇 |
2011年 | 283篇 |
2010年 | 185篇 |
2009年 | 213篇 |
2008年 | 226篇 |
2007年 | 183篇 |
2006年 | 184篇 |
2005年 | 161篇 |
2004年 | 151篇 |
2003年 | 163篇 |
2002年 | 141篇 |
2001年 | 102篇 |
2000年 | 95篇 |
1999年 | 141篇 |
1998年 | 509篇 |
1997年 | 347篇 |
1996年 | 252篇 |
1995年 | 136篇 |
1994年 | 135篇 |
1993年 | 150篇 |
1992年 | 62篇 |
1991年 | 59篇 |
1990年 | 60篇 |
1989年 | 54篇 |
1988年 | 49篇 |
1987年 | 32篇 |
1986年 | 53篇 |
1985年 | 59篇 |
1984年 | 40篇 |
1983年 | 45篇 |
1982年 | 41篇 |
1981年 | 49篇 |
1980年 | 42篇 |
1979年 | 27篇 |
1978年 | 19篇 |
1977年 | 28篇 |
1976年 | 50篇 |
1975年 | 13篇 |
1973年 | 14篇 |
排序方式: 共有5969条查询结果,搜索用时 46 毫秒
31.
R. Dinesh T. Fujiwara T. Watanabe K. Byrappa M. Yoshimura 《Journal of Materials Science》2006,41(5):1541-1546
A well-crystallized AMO4 (A=Ba, Ca, Sr; M=W, Mo) films have been prepared at room temperature through a simple solution reaction in respective alkaline
solution at higher pH ranging from 12–14. Adopting the corrosion principle for oxidation of metal substrate, these double
oxide films were carried out in presence of chemical driving force without any special apparatus or devices. Hydrogen peroxide
was used to enhance the dissolution rate of metal substrates. The driving force for the film formation and growth were high
concentration of A2+, MO42− ions with high pH conditions. Average grain sizes of 8–10 μm with bipyramidal shaped particle were grown to the thickness
of about 10–14 μm after 3–6 hours treatment. The crystallization of AMO4 was characterized by three-dimensional nucleation. This work demonstrates the possibility of fabrication of functional ceramic
films directly from the aqueous solution in a single step by solution reactions. 相似文献
32.
A three-dimensional pin power reconstruction method was proposed and verified by applying to the axially heterogeneous region problem of the BWR core calculation. Because the production assembly calculation has been carried out by two-dimensional deterministic calculation methods like current coupling collision probability or the method of characteristics, it has been difficult to predict the detailed three-dimensional heterogeneous pin power distribution of the axially heterogeneous region. Consequently, only radial intranodal homogeneous power distributions have been considered, and axial intranodal homogeneous power distributions have not been considered in the estimation of linear-heat-generation-ratio at common BWR core calculations. 相似文献
33.
Assistant Professor T. Watanabe 《Acta Mechanica》1987,65(1-4):41-50
Summary The purpose of the paper is to consider theoretically the characteristics of steady two-dimensional magnetohydrodynamic boundary layer flow past a flat plate with pressure gradient in the presence of transverse magnetic field and its stability problem. The boundary layer equation is transformed into a non-similar one and numerical solutions are obtained by the difference-differential method. The neutral stability curves for wavelike disturbances of Tollmien-Schlichting type are then presented for the velocity profiles obtained above. Numerical results for the magnetic parameter and pressure gradient parameter are given for the velocity profiles, coefficient of skin friction, displacement thickness and the critical Reynolds number.With 10 Figures 相似文献
34.
35.
J. Okabayashi M. Watanabe H. Toyao T. Yamaguchi J. Yoshino 《Journal of Superconductivity and Novel Magnetism》2007,20(6):443-446
We have investigated the current pulse width dependence on current-driven magnetization reversal in double-barrier structures
using GaMnAs-based magnetic tunneling junctions (MTJ) in order to clarify the origin of low threshold current density for
current-driven magnetization reversal. Comparing with the case of single-barrier MTJ, the pulse-width dependence reveals that
threshold current density is reduced by double-barrier MTJ. We confirmed that the threshold current density in the order of
104 A/cm2 is estimated considering the effect of current pulse width. 相似文献
36.
A compact, high-resolution analog-to-digital converter (ADC) especially for sensors is presented. The basic structure is a completely digital circuit including a ring-delay-line with delay units (DUs), along with a frequency counter, latch, and encoder. The operating principles are: (1) the delay time of the DU is modulated by the analog-to-digital (A/D) conversion voltage and (2) the delay pulse passes through a number of DUs within a sampling (= integration) time and the number of DUs through which the delay pulse passes is output as conversion data. Compact size and high resolution were realized with an ADC having a circuit area of 0.45 mm/sup 2/ (0.8-/spl mu/m CMOS) and a resolution of 12 /spl mu/V (10 kS/s). Its nonlinearity is /spl plusmn/0.1% FS per 200-mV span (1.8-2.0 V), for 14-b resolution. Sample holds are unnecessary and a low-pass filter function removes high-frequency noise simultaneously with A/D conversion. Thus, the combination of this ADC and a digital filter that follows can eliminate an analog prefilter to prevent the aliasing before A/D conversion. Also, both this ADC can be shrunk and operated at low voltages, so it is an ideal means to lower the cost and power consumption. Drift errors can be easily compensated for by digital processing. 相似文献
37.
It is necessary to determine the accurate reflectance of painted surfaces for the review of paint finishes by computer graphics (CG) before actual painting of the exterior color of automobiles, and for quality control during production and inspection processes. We have optimized a method for measuring reflectance by using a statistical technique. We have found that the reflectance of a painted surface is best measured at an incident angle of 60° and at five aspecular angles of 10°, 18°, 28°, 40°, and 90°. Our method makes it possible to accurately reproduce reflection characteristics of paint finishes containing special flake pigments, such as pearl mica. Also it was proved that our method can apply not only to solid and metallic coatings but to all painted surfaces. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 275–282, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20125 相似文献
38.
In accord with the increasing concern about the global environmental issues, the absorption refrigeration heat-pump systems are currently being considered very promising and attractive. For the purpose of supporting the advanced R&D technology in this area, we have developed a novel correlation to represent the bubble-point pressures of LiBr H2O solutions. The developed correlation covers the most extensive range of validity ever proposed: 273–483 K for temperatures, 0.05 kPa to 1.0 MPa for pressures. and 29 76 wt% LiBr for concentrations.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994. Boulder, Colorado, U.S.A. 相似文献
39.
Bubble-point pressures and saturated-liquid densities of the binary R-135 (pentafuoroethane) + R- 143a ( 1, 1, 1-trifluoroethane) system have been measured for several compositions at temperatures from 280 to 330 K by means of a magnetic densimeter coupled with a variable-volume cell mounted with a metallic bellows. The experimental uncertainties of the temperature, pressure. and density measurements and the composition determination were estimated to be within ±15 mK, ±13 k Pa, ±0.2%, and ±0.1 wt%, respectively. The purities of the samples used throughout the measurements are 99.98 wt% for R-125 and 99.0 mol % for R- 143a. Based on the present data, the thermodynamic behavior of the vapor-liquid equilibria of this binary refrigerant mixture has been evaluated by using the Peng-Robinson equation for the bubble-point pressures, and the modified Hankinson-Brobst-Thomson equation for the saturated-liquid densities. This was done to identify the optimized binary interaction parameters.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A. 相似文献
40.
Hara H. Sakurai T. Nagamatsu T. Seta K. Momose H. Niitsu Y. Miyakawa H. Matsuda K. Watanabe Y. Sano F. Chiba A. 《Solid-State Circuits, IEEE Journal of》1992,27(11):1579-1584
BiCMOS standard cell macros, including a 0.5-W 3-ns register file, a 0.6-W 5-ns 32-kbyte cache, a 0.2-W 3-ns table look-aside buffer (TLB), and a 0.1-W 3-ns adder, are designed with a 0.5-μm BiCMOS technology. A supply voltage of 3.3 V is used to achieve low power consumption. Several BiCMOS/CMOS circuits, such as a self-aligned threshold inverter (SATI) sense amplifier and an ECL HIT logic are used to realize high-speed operation at the low supply voltage. The performance of the BiCMOS macros is verified using a fabricated test chip 相似文献