全文获取类型
收费全文 | 47722篇 |
免费 | 4559篇 |
国内免费 | 2575篇 |
专业分类
电工技术 | 1145篇 |
综合类 | 2262篇 |
化学工业 | 10101篇 |
金属工艺 | 2586篇 |
机械仪表 | 3364篇 |
建筑科学 | 1251篇 |
矿业工程 | 1054篇 |
能源动力 | 2460篇 |
轻工业 | 8286篇 |
水利工程 | 131篇 |
石油天然气 | 1470篇 |
武器工业 | 146篇 |
无线电 | 2674篇 |
一般工业技术 | 5112篇 |
冶金工业 | 10715篇 |
原子能技术 | 848篇 |
自动化技术 | 1251篇 |
出版年
2024年 | 200篇 |
2023年 | 839篇 |
2022年 | 1505篇 |
2021年 | 1919篇 |
2020年 | 1727篇 |
2019年 | 1648篇 |
2018年 | 1546篇 |
2017年 | 1744篇 |
2016年 | 1879篇 |
2015年 | 1832篇 |
2014年 | 2955篇 |
2013年 | 3051篇 |
2012年 | 3322篇 |
2011年 | 3415篇 |
2010年 | 2349篇 |
2009年 | 2454篇 |
2008年 | 1841篇 |
2007年 | 2747篇 |
2006年 | 2543篇 |
2005年 | 2186篇 |
2004年 | 1830篇 |
2003年 | 1791篇 |
2002年 | 1507篇 |
2001年 | 1292篇 |
2000年 | 1116篇 |
1999年 | 1049篇 |
1998年 | 759篇 |
1997年 | 710篇 |
1996年 | 570篇 |
1995年 | 534篇 |
1994年 | 424篇 |
1993年 | 311篇 |
1992年 | 266篇 |
1991年 | 216篇 |
1990年 | 147篇 |
1989年 | 109篇 |
1988年 | 90篇 |
1987年 | 62篇 |
1986年 | 60篇 |
1985年 | 47篇 |
1984年 | 36篇 |
1983年 | 29篇 |
1982年 | 55篇 |
1981年 | 71篇 |
1980年 | 26篇 |
1979年 | 10篇 |
1978年 | 5篇 |
1976年 | 5篇 |
1975年 | 6篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Al2O3对唐钢高炉炉渣性能的影响 总被引:14,自引:1,他引:13
针对唐钢近2年提高进口矿配比后,Al2O3含量升高对炉渣流动性带来的不利影响,对唐钢高炉的炉渣性能进行了试验研究。并结合国内同行业的生产实践经验,从理论上分析了炉渣中Al2O3及MgO的适宜含量范围,着重论述了唐钢所处冀东矿区条件下降低Al2O3的主要途径及适应高Al2O3炉渣的具体措施。 相似文献
22.
本文介绍了用αβ谱仪系统同时测量αβ谱、实现Rn/Th子体补偿、确定超铀α核素气溶胶体积活度及人工放射性气溶胶总β体积活度的技术途径。利用RaA、RaC′a峰的二段时间计数可确定空气中RaA、RaB、RaC的气溶胶体积活度,相应的,也能给出RaB、RaC对总β计数的贡献。根据一般环境条件下的平衡比,用ThC′的。计数修正Th子体对αβ测量的影响。 ̄[239]pu或/和 ̄[241]Am人工核素的α计数,可通过两段时间分别扣除RaA、RaC′拖尾的方法确定;β计数分别扣除Rn/Th子体β贡献即可确定。在本文规定的测量条件下,对室内天然Rn子体水平在15Bq/m ̄3以下,超铀α核素气溶胶体积活度的测量下限可达到0.1Bq/m ̄3;即使在75Bq/m ̄3环境下,人工核素总β的测量下限也可达lBq/m ̄3以下。 相似文献
23.
The effect of FEF carbon black as filler on the thermal capacity c, diffusivity a, and thermal conductivity λ, of styrene butadiene rubber (SBR) composites in the temperature range 300–420 K was studied. The filler strongly increases the thermal diffusivity, whilst strongly decreasing the thermal capacity and the thermal conductivity (except at high FEF content ≥80 phr). The influence of the filler on the thermoelastic behaviour of the same composites was also investigated. It was found that the thermoelastic temperature change (ΔT) increased with carbon black concentration as well as the entropy change per unit extension. 相似文献
24.
David Lloyd Suzie Morrell Helle N. Carlsen Hans Degn Phillip E. James Christopher C. Rowlands 《Yeast (Chichester, England)》1993,9(8):825-833
Saccharomyces cerevisiae HSc was grown with ethanol at concentrations up to 10% (v/v). The immediate effects of additions of externally added ethanol on CO2 production and O2 consumption of washed organisms were studied by stopped-flow membrane inlet quadrupole mass spectrometry. Fermentative activities of organisms grown with ethanol (0–5% v/v) showed similar sensitivities to inhibition by ethanol, whereas those grown with 10% (v/v) ethanol had become protected and were markedly less sensitive. The fluidity of subcellular membrane fractions was measured by determination of the temperature dependence of the rotational order parameter of the spin label 5-doxyl stearic acid (free radical) by electron spin resonance. Mitochondria prepared from yeasts grown with 0, 7 and 9% (v/v) ethanol showed similar overall fluidity, although differences in temperature-dependent behaviour indicate altered lipid composition or lateral phase separations. On the other hand the microsomal fraction from organisms grown with 9% ethanol showed a remarkable increase in fluidity. These data suggest that the protective effects of growth with ethanol near the limit of tolerance on fermentative activities may arise from altered plasma membrane fluidity properties. 相似文献
25.
A general model, based on double film theory, is developed to study absorption with chemical reactions. In the liquid film region, the model is a set of differential equations that describe the mass transfer accompanying several chemical reactions; the resolution of the system is achieved by the finite difference method using an implicit scheme combined with Newton's method. Continuity equations and equilibrium coefficients are exploited in the treatment of the bulk region, which is based on the Newton‐Raphson method; the results are used directly as boundary conditions in the liquid film equations. Maxwell‐Stefan equations have been used as a rigorous approach in this model. 相似文献
26.
通过对组成打结料成分特性的研究,提出以优质原料生产的MgO-CaO-Fe2O3系合成砂为骨料,用MgO〉97%,粒度〈0.088mm烧结镁砂做细粉,适当添加超微粉等工艺措施,制成适当高碳铬铁电炉炉底用的高基质打结料,通过调控基质成分,实现材料相和固相的复合烧结。 相似文献
27.
Abdulla A. Shaikh S. M. Javaid Zaidi 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1993,56(2):139-145
The absorption and reaction of oxygen in aqueous alkaline solutions of sodium dithionite has been experimentally investigated in a novel gas-liquid contactor. The novel gas-lift bubble column contactor was used to study the kinetics over wide ranges of reactant concentrations, temperature, and pH. The oxygen-sodium dithionite reaction was found to be first-order with respect to dithionite in the range of dithionite concentration < 0.1 M, and second-order in the range of dithionite concentration > 0.1 M. The reaction with respect to oxygen was found to be zero-order for all dithionite concentrations. These results and experimental investigations of the effect of solution alkalinity and temperature on the reaction rate are consistent with previous findings obtained in different gas-liquid contactors. The results thus confirm the feasibility of using the gas-lift bubble column for the kinetics of gas-liquid reactions. 相似文献
28.
T. R. Guilinger M. J. Kelly J. R. Scully T. M. Christensen D. Ingersoll J. A. Knapp R. I. Ewing W. H. Casey S. S. Tsao 《Journal of Fusion Energy》1990,9(3):299-304
We describe several electrochemical methods used to investigate the possibility of cold fusion phenomena in palladium and titanium tritide cathodes. We performed long-term (up to 77 days) electrolysis experiments with electrochemical cells of the University of Utah type at current densities as high as 1 A/cm2, while monitoring neutron and tritium levels. With some cells, we pulsed the current to determine if neutron bursts would result. In another cell, we used titanium tritide as the cathode to determine if D-T reactions yielding neutrons would occur. In no instance were levels of neutrons or tritium significantly above background except in the titanium tritide cell where isotopic exchange, occcurring between the electrode and the electrolyte, resulted in significant tritium levels. We also combined x-ray photoelectron spectroscopy (XPS) and electrochemical hydrogen permeation experiments to determine the effectiveness of various Pd surface treatment procedures on the resultant electrochemical hydrogen absorption efficiency. Electroanalytical and thermal desorption/gas analysis techniques indicated the maximum loading of H in Pd was to a ratio of HPd=0.8. 相似文献
29.
30.