全文获取类型
收费全文 | 70309篇 |
免费 | 8730篇 |
国内免费 | 4269篇 |
专业分类
电工技术 | 11556篇 |
综合类 | 6147篇 |
化学工业 | 12267篇 |
金属工艺 | 4414篇 |
机械仪表 | 4048篇 |
建筑科学 | 9952篇 |
矿业工程 | 1570篇 |
能源动力 | 5400篇 |
轻工业 | 2363篇 |
水利工程 | 1672篇 |
石油天然气 | 2252篇 |
武器工业 | 972篇 |
无线电 | 4704篇 |
一般工业技术 | 8661篇 |
冶金工业 | 2419篇 |
原子能技术 | 851篇 |
自动化技术 | 4060篇 |
出版年
2024年 | 430篇 |
2023年 | 1278篇 |
2022年 | 2063篇 |
2021年 | 2495篇 |
2020年 | 2776篇 |
2019年 | 2382篇 |
2018年 | 2274篇 |
2017年 | 2791篇 |
2016年 | 2817篇 |
2015年 | 2999篇 |
2014年 | 4433篇 |
2013年 | 4467篇 |
2012年 | 5070篇 |
2011年 | 5321篇 |
2010年 | 3967篇 |
2009年 | 4156篇 |
2008年 | 3749篇 |
2007年 | 4614篇 |
2006年 | 4304篇 |
2005年 | 3414篇 |
2004年 | 2875篇 |
2003年 | 2373篇 |
2002年 | 2066篇 |
2001年 | 1776篇 |
2000年 | 1508篇 |
1999年 | 1240篇 |
1998年 | 934篇 |
1997年 | 883篇 |
1996年 | 736篇 |
1995年 | 560篇 |
1994年 | 451篇 |
1993年 | 348篇 |
1992年 | 314篇 |
1991年 | 274篇 |
1990年 | 244篇 |
1989年 | 212篇 |
1988年 | 177篇 |
1987年 | 93篇 |
1986年 | 78篇 |
1985年 | 77篇 |
1984年 | 72篇 |
1983年 | 57篇 |
1982年 | 59篇 |
1981年 | 30篇 |
1980年 | 23篇 |
1979年 | 9篇 |
1977年 | 3篇 |
1975年 | 4篇 |
1959年 | 7篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
根据高性混凝土的水化特性、物理力学特性及自收缩特性,分析了高性能混凝土早期开裂机理和影响早期开裂的主要因素.并结合工程实例,借助混凝土温度和应力有限元仿真计算方法分析研究了表面适度保温和水管冷却技术在高性能混凝土温控防裂中的应用效果.研究结果表明,表面适度保温与水管冷却相结合能有效降低混凝土的内外温差,减小混凝土早期表面拉应力与后期内部拉应力,防裂效果明显,对类似的工程具有借鉴作用. 相似文献
92.
Mirna Suárez-Quiroz Béatrice De Louise Oscar Gonzalez-Rios Michel Barel Bernard Guyot Sabine Schorr-Galindo & Joseph-Pierre Guiraud 《International Journal of Food Science & Technology》2005,40(6):605-611
Roasting coffee led to a drop in the ochratoxin A (OTA) concentration, as measured by the reference method, especially for dark type roasts. The way the beverage was prepared also affected the OTA content, which could paradoxically be higher than that of the initial roasted coffee. Assays on the thermal stability of pure OTA showed that it ought to be found in larger quantities in roasted coffee. This suggested that OTA was masked by reactions with the substrate during roasting. The absence of OTA in green coffee is therefore the best guarantee of safety. 相似文献
93.
The present study presents the synthesis of unsaturated polyester resins using only one glycol i.e., ethylene glycol. Polyesters of inorganic solubility in styrene were prepared. Properties of the resins in the noncrosslinked state in the process of crosslinking and after curing were studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3143–3150, 2006 相似文献
94.
3-D MCM封装技术及其应用 总被引:1,自引:0,他引:1
介绍了超大规模集成电路(VLSI)用的3-D MCM封装技术的最新发展,重点介绍了3-D MCM封装垂直互连工艺,分析了3-D MCM封装技术的硅效率、复杂程度、热处理、互连密度、系统功率与速度等问题,并对3-D MCM封装的应用作了简要说明。 相似文献
95.
《International Journal of Food Science & Technology》2003,38(3):297-304
Summary The heat resistance of a four‐strain mixture of Escherichia coli O157:H7 was tested. The temperature range was 55–62.5 °C and the substrate was beef at pH 4.5 or 5.5, adjusted with either acetic or lactic acid. Inoculated meat, packaged in bags, was completely immersed in a circulating water bath and cooked to an internal temperature of 55, 58, 60, or 62.5 °C in 1 h, and then held for pre‐determined lengths of time. The surviving cell population was enumerated by spiral plating meat samples on tryptic soy agar overlaid with Sorbitol MacConkey agar. Regardless of the acidulant used to modify the pH, the D ‐values at all temperatures were significantly lower (P < 0.05) in ground beef at pH 4.5 as compared with the beef at pH 5.5. At the same pH levels, acetic acid rendered E. coli O157:H7 more sensitive to the lethal effect of heat. The analysis of covariance showed evidence of a significant acidulant and pH interaction on the slopes of the survivor curves at 55 °C. Based on the thermal‐death–time values, contaminated ground beef (pH 5.5/lactic acid) should be heated to an internal temperature of 55 °C for at least 116.3 min and beef (pH 4.5/acetic acid) for 64.8 min to achieve a 4‐log reduction of the pathogen. The heating time at 62.5 °C, to achieve the same level of reduction, was 4.4 and 2.6 min, respectively. Thermal‐death–time values from this study will assist the retail food processors in designing acceptance limits on critical control points that ensure safety of beef originally contaminated with E. coli O157:H7. 相似文献
96.
利用寿命周期评价的思想,计算了炼铁生产过程中的环境负荷,并分析了各因素对环境负荷的影响,运用神经网络对炼铁生产过程环境负荷进行了预测。 相似文献
97.
ZnS, ZnSe, and CdTe polycrystals are experimentally investigated. Mechanisms are treated which restrict the thermal conductivity in samples prepared by recrystallization pressing and by deposition from the vapor phase and subjected to additional strain. Anomalies are observed on the temperature dependences of the thermal resistance of investigated samples, which are due to the special features of their phonon spectra and to the variation of the contribution made by longitudinal and transverse phonon branches to the heat transfer in the Debye temperature region and higher. 相似文献
98.
We study the stressed state of an inhomogeneous welded joint containing an interlayer of a more high-strength material under the action of tensile loads. It is assumed that the contact boundary has a cracklike defect. We deduce analytic dependences of the fracture load on the mechanical inhomogeneity of the joint, thickness of the interlayer, and depth of the defect. The maximum depth of the defect to which the joint is insensitive is established. The proposed theoretical results are innovative and agree with the experimental data obtained for specimens cut out from a pipe of 14KhGS steel. 相似文献
99.
金属基复合材料的热残余应力力学模型研究进展 总被引:3,自引:0,他引:3
金属基复合材料在高温制备的冷却过程中或热处理过程中由于组分间热膨胀系数(CTEs)的差异会产生较大的热残余应力,热残余应力对复合材料的宏观性能有着重要的影响。本文综述了分析金属基复合材料热残余应力的有限元模型和解析模型等理论模型,并指出有待深入研究的问题。 相似文献
100.
就我公司动力厂给水车间155kW水泵电机无功就地补偿的可行性及经济效益进行了分析和研究,对工厂用电如何节能降耗有一定的参考价值。 相似文献