全文获取类型
收费全文 | 28641篇 |
免费 | 2160篇 |
国内免费 | 921篇 |
专业分类
电工技术 | 516篇 |
综合类 | 1593篇 |
化学工业 | 8576篇 |
金属工艺 | 4916篇 |
机械仪表 | 1368篇 |
建筑科学 | 1224篇 |
矿业工程 | 842篇 |
能源动力 | 263篇 |
轻工业 | 3751篇 |
水利工程 | 144篇 |
石油天然气 | 295篇 |
武器工业 | 348篇 |
无线电 | 565篇 |
一般工业技术 | 3756篇 |
冶金工业 | 3244篇 |
原子能技术 | 84篇 |
自动化技术 | 237篇 |
出版年
2024年 | 121篇 |
2023年 | 431篇 |
2022年 | 675篇 |
2021年 | 909篇 |
2020年 | 885篇 |
2019年 | 649篇 |
2018年 | 691篇 |
2017年 | 890篇 |
2016年 | 892篇 |
2015年 | 912篇 |
2014年 | 1312篇 |
2013年 | 1488篇 |
2012年 | 1765篇 |
2011年 | 1855篇 |
2010年 | 1529篇 |
2009年 | 1454篇 |
2008年 | 1273篇 |
2007年 | 1842篇 |
2006年 | 1897篇 |
2005年 | 1620篇 |
2004年 | 1411篇 |
2003年 | 1279篇 |
2002年 | 1120篇 |
2001年 | 947篇 |
2000年 | 811篇 |
1999年 | 667篇 |
1998年 | 533篇 |
1997年 | 435篇 |
1996年 | 332篇 |
1995年 | 277篇 |
1994年 | 261篇 |
1993年 | 162篇 |
1992年 | 139篇 |
1991年 | 70篇 |
1990年 | 56篇 |
1989年 | 47篇 |
1988年 | 25篇 |
1987年 | 15篇 |
1986年 | 7篇 |
1985年 | 7篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 7篇 |
1981年 | 9篇 |
1980年 | 6篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Long processing cycle makes vacuum assisted resin infusion molding (VARIM) only suitable for low and medium volumes of production, and shortening of curing time is critical to improving the processing efficiency of automotive composite parts. In this paper, unidirectional carbon fiber reinforced composite laminates were fabricated by VARIM. Three different processes (namely quick, quick-post and preheating) were employed, in which a kind of rapid curing epoxy resin is used. The preheating of mold and fiber was conducted to shorten the filling time compared with that of quick process. Quick-post process with a post cure stage was investigated to verify the composite properties fabricated by quick process. The cycle time was 16 min for preheating process, about 30% shorter than that of quick process, simultaneously, flexural strength and interlaminar shear strength (ILSS) were respectively improved by 29% and 7% compared with those of quick process. The non-uniformity of mechanical properties at different positions along resin flow direction under preheating process was found, but the processing quality of composite was good. The preheating process is confirmed to be suitable for the improvement of processing efficiency of VARIM with good mechanical properties. In addition, the composite fabricated by quick-post process has better mechanical properties, which is attributed to the alleviation of residual stress during post curing process. 相似文献
993.
首先建立了微构件的热注射近净成型的数学模型,讨论了参数变量的控制。通过数据分析找到了参数的最佳控制范围,达到微构件的热注射近净成型过程中效率高、损失小的实验目标。 相似文献
994.
995.
Shi-yun Wu Xiao-yu Wu Bin Xu Rong Cheng Feng Luo Shuang-chen Ruan 《Journal of Materials Processing Technology》2014,214(11):2668-2675
The Sn–Bi eutectic alloy powder in the micro-cavity was melted by ultrasonic vibration and rapidly cooled to form micro parts; no subsequent sintering process was required. Three kinds of Sn–Bi alloy micro gears were successfully fabricated, which verified the feasibility of the micro-ultrasonic powder moulding method. The effect of ultrasonic exposure time on the microstructure and mechanical properties of the micro parts was investigated respectively by metallographic analysis, XRD and tensile testing. Reasonable process parameters for this method were determined, which were sonotrode pressure of 63.5 MPa, ultrasonic output power of 2475 W and ultrasonic exposure time of 1.5 s. 相似文献
996.
The new concept, anion substitution, is explored for possible improvement of hydrogen storage properties in the system LiBH4-LiI. The structural chemistry and the substitution mechanism are analyzed using Rietveld refinement of in situ synchrotron radiation powder X-ray diffraction (SR-PXD) data, attenuated total reflectance infrared spectroscopy (ATR-IR), differential scanning calorimetry (DSC) and Sieverts measurements. Anion substitution is observed as formation of two solid solutions of Li(BH4)1−xIx, which merge into one upon heating. The solid solutions have hexagonal structures (space group P63mc) similar to the structures of h-LiBH4 and β-LiI. The solid solutions have iodide contents in the range ∼0-62 mol% and are stable from below room temperature to the melting point at 330 °C. Thus the stability of the solid solutions is higher as compared to that of the orthorhombic and hexagonal polymorphs of LiBH4 and α- and β-LiI. Furthermore, the rehydrogenation properties of the iodide substituted solid solution Li(BH4)1−xIx, measured by the Sieverts method, are improved as compared to those of LiBH4. After four cycles of hydrogen release and uptake the Li(BH4)1−xIx solid solution maintains 68% of the calculated hydrogen storage capacity in contrast to LiBH4, which maintains only 25% of the storage capacity after two cycles under identical conditions. 相似文献
997.
Elena Pastor‐Cavada Silvina R. Drago Rolando J. González Rocío Juan Julio E. Pastor Manuel Alaiz Javier Vioque 《International Journal of Food Science & Technology》2013,48(9):1949-1955
Flour blends based on whole corn and rice with two added wild legumes at 15% level of cereal replacement were extruded to produce whole grain snacks. Extrusion temperature was 175 °C, and the moisture content was adjusted to 14%. The extruded products were evaluated for their physical, chemical and nutritional properties. Results showed that the addition of legumes produces a decrease in expansion in rice‐containing samples and an increase in solubility in corn‐containing samples. With only 15% of legume added to cereal, a significant increase in protein content and quality was obtained. An increase in fibre, polyphenol, iron and zinc content was also obtained. Protein digestibility was in the range of 81.8–85.3%. Mineral availability ranged from 6.4 to 16.3% for iron and 10–16.3% for zinc. The performance of each mixture during extrusion and the physical properties of the extruded products were considered to be similar to those expected for snack‐type products and described in the literature. 相似文献
998.
Pure Fe,Cr,Al,Ti elemental powders and prealloyed Y2O3 powder were processed by high energy mechanical milling.The compositions of the mixed powders are designed as Fe-18Cr-0.2Ti-0.35Y2O3 and Fe-18Cr-5... 相似文献
999.
In this article the effects of moisture on a novel epoxy molding compound, including the mechanical properties, temperature transition, and thermal degradation behavior, are studied. The experimental results reveal that the absorbed water acts predominantly as a crazing agent, continuously decreasing the mechanical strength with the time in water. The glass-transition temperature decreases at the early stage and is finally equilibrated. The thermal degradation behavior of the materials is not greatly influenced by the hydrothermal age. The decomposition of samples in oxygen is composed of two independent steps: the thermal degradation and oxidation at high temperature. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2253–2259, 2001 相似文献
1000.
采用孔隙率大于90%的泡沫铜装填ZrCo合金粉末,测试分析了泡沫铜填充ZrCo合金粉末的吸放氢性能和充放氢抗破坏性能。结果表明:通过泡沫铜填充法制备贮氢块的传热性能比自然堆积状态的粉末有很大提高,因此采用泡沫铜装填的贮氢反应容器吸、放氢速率比自然堆积粉末有明显改善,并显著提高了充放氢抗破坏能力,利用该方法改进贮氢粉末的装填方式是可行的。 相似文献