全文获取类型
收费全文 | 31868篇 |
免费 | 2623篇 |
国内免费 | 1903篇 |
专业分类
电工技术 | 1649篇 |
综合类 | 1599篇 |
化学工业 | 10808篇 |
金属工艺 | 2907篇 |
机械仪表 | 1150篇 |
建筑科学 | 1225篇 |
矿业工程 | 357篇 |
能源动力 | 685篇 |
轻工业 | 1786篇 |
水利工程 | 121篇 |
石油天然气 | 1692篇 |
武器工业 | 249篇 |
无线电 | 3200篇 |
一般工业技术 | 3259篇 |
冶金工业 | 1299篇 |
原子能技术 | 671篇 |
自动化技术 | 3737篇 |
出版年
2024年 | 132篇 |
2023年 | 554篇 |
2022年 | 1226篇 |
2021年 | 1537篇 |
2020年 | 1128篇 |
2019年 | 855篇 |
2018年 | 680篇 |
2017年 | 863篇 |
2016年 | 1047篇 |
2015年 | 1061篇 |
2014年 | 1469篇 |
2013年 | 1825篇 |
2012年 | 1873篇 |
2011年 | 2458篇 |
2010年 | 1796篇 |
2009年 | 1986篇 |
2008年 | 1788篇 |
2007年 | 1998篇 |
2006年 | 1908篇 |
2005年 | 1525篇 |
2004年 | 1219篇 |
2003年 | 1104篇 |
2002年 | 983篇 |
2001年 | 851篇 |
2000年 | 734篇 |
1999年 | 621篇 |
1998年 | 471篇 |
1997年 | 387篇 |
1996年 | 330篇 |
1995年 | 264篇 |
1994年 | 219篇 |
1993年 | 217篇 |
1992年 | 183篇 |
1991年 | 145篇 |
1990年 | 128篇 |
1989年 | 87篇 |
1988年 | 64篇 |
1987年 | 67篇 |
1986年 | 64篇 |
1985年 | 72篇 |
1984年 | 63篇 |
1983年 | 44篇 |
1982年 | 38篇 |
1981年 | 39篇 |
1980年 | 40篇 |
1978年 | 37篇 |
1977年 | 41篇 |
1976年 | 43篇 |
1975年 | 49篇 |
1974年 | 43篇 |
排序方式: 共有10000条查询结果,搜索用时 890 毫秒
101.
102.
Jan‐Chan Huang 《应用聚合物科学杂志》2003,90(3):671-680
A modified method is discussed that is based on Farooque and Deshpande's method to obtain polymer–polymer interaction parameters using inverse gas chromatography (IGC) data. In the Farooque and Deshpande method, the ratio of the difference of probe–polymer interaction parameters between two polymers and the probe volume [(χ12 ? χ13)/V1] is used as the abscissa. In the modified method, the ratio [(?2χ12 + ?3χ13)/V1] is used as the abscissa. Experimental data previously reported for a poly(?‐caprolactone)‐polyepichlorohydrin (PCL/PECH) blend and a poly(ethyl acrylate)‐poly(vinyl propionate) (PEA/PVPr) blend are analyzed. It is found that the slopes obtained by the new method had smaller deviations from the theoretical values than the Farooque and Deshpande method. The standard deviations of both slopes and intercepts obtained from the new method are also smaller. Using the new method, the polymer–polymer interaction parameters obtained from the intercept are negative numbers for the PCL/PECH system and very small positive numbers for PEA/PVPr. Explanations are given for the probe and concentration dependency of the polymer–polymer interaction parameters that are generally observed in IGC studies. A new method for selecting the best probe for calculating the interaction parameter is discussed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 671–680, 2003 相似文献
103.
LiNi0.5Mn1.5O4 powder was synthesized via sol-gel method and coated with ZnO in order to test the electrochemical cyclability of the material as a cathode for the secondary Li battery in the 5 V range at 55 °C. The ZnO-coated LiNi0.5Mn1.5O4 powder nearly maintained its initial capacity of 137 mA h g−1 after 50 cycles whereas the uncoated powder was able to retain no more than 10% of the initial capacity after 30 cycles. TEM analysis of the cycled cathodes suggests that the formation of the graphitic surface phase, hindering the Li migration, may be responsible for the rapid capacity loss of the uncoated material while no such phase was observed on the surface of the ZnO coated LiNi0.5Mn1.5O4 powder. 相似文献
104.
Kenji Nomura Hiromichi OhtaKazushige Ueda Toshio Kamiya Masahiro HiranoHideo Hosono 《Thin solid films》2003,445(2):322-326
We have investigated the characteristics of transparent metal-insulator-semiconductor field-effect transistors (MISFETs) fabricated using InGaO3(ZnO)m (m=integer) single-crystalline thin films as n-channel layers and amorphous alumina as gate insulator films. The MISFETs exhibit good characteristics such as insensitivity to visible light illumination, off-current as low as ∼1 nA with a positive threshold voltage of ∼3 V and on/off current ratio of 105. The field-effect mobility increased from ∼1 to ∼10 cm2 (V s)−1 as the m-value increased. Room temperature Hall mobility also increased. However, unexpectedly these values were lower than the field-effect mobility. It is explained by existence of shallow localized state in the homologous compounds. 相似文献
105.
SF6气体绝缘电容式电压互感器研制 总被引:6,自引:0,他引:6
本文介绍西容公司新研制的一种完全无油化的SF6气体绝缘电容式电压互感器,提出了关键技术问题解决方案和产品绝缘结构的设计思路.并介绍了研制成功的110kV和220kV系列产品的结构、技术参数、性能指标、试验考核情况和产品特点. 相似文献
106.
首先以 HERMLE C1200 U 为例分析了五轴铣削加工中心的基本结构,然后据此给出了涉及多轴铣削加工中心后置处理角度分配和坐标变换的数学模型,最后介绍了以此数学模型为核心,为UG 软件开发的后置处理软件 UG-HERP1.0的解决方案。 相似文献
107.
J. Gegner Priv.‐Doz. Dr. W. Nierlich M. Brückner 《Materialwissenschaft und Werkstofftechnik》2007,38(8):613-623
Due to clearly distinguishable damage symptoms, it is differentiated between the surface and sub‐surface failure mode of rolling bearings. Material states red out by X‐ray diffraction (XRD) residual stress measurements point to a variety of loading conditions especially at raceway surfaces that are associated with several competing failure mechanisms. The corresponding lifetime reduction can range from the lower fatigue strength region to material ratcheting in extreme cases. Relevant position of the microstructural changes and nature of the failure mechanisms are characterized. The time alteration of the XRD material parameters measured at or near the surface and at the depth of the maximum equivalent stress correlates, in a different manner, with the statistical parameter of the 10 % bearing life. Both failure modes are illustrated by concrete examples. Contaminated lubricant and boundary lubrication, which represent practically important surface‐induced failures, are discussed in more detail. Gray staining, i.e. shallow pitting, often occurs without distinct indication of global material aging by means of XRD characteristics. Here, scanning electron microscopy observations and electron microprobe analyses point to corrosion fatigue as acting surface failure mechanism. The interaction between material and lubricant under complex loading regimes particularly of mixed friction and corrosion opens further failure research areas in the field of tribology. 相似文献
108.
尼龙6/马来酸酐-苯乙烯多单体接枝聚丙烯反应共混物 总被引:8,自引:0,他引:8
用双螺杆挤出机制备了聚丙烯(PP)与尼龙6(PA6)的共混物.先用多组分熔融接枝的方法将马来酸杆(MAH)和苯乙烯(St)共同接枝于聚丙烯(PP)上,制得多单体接枝聚丙烯PP-g-(MAH-St),该接枝物具有较高的MAH接枝率。利用MFR、SEM、TEM和力学性能测试等分析方法,研究了多组分熔融接枝聚丙烯PP-g-(MAH-St)对PA6/PP共混物的形态结构和力学性能等的影响。结果表明,PP-g-(MAH-St)中的酸酐基团与PA6末端的氨基发生化学反应,原位形成的PP-PA6共聚物能有效地改善PA6与PP的相容性,可以使PP均匀地分散在PA6基体中,相区尺寸明显减小,可至0.1μm,并使共混物的力学性能得到均衡的提高,冲击韧性的提高尤其显著,达到了橡胶改性所难以达到的效果。 相似文献
109.
TORGILS FOSSEN ØYVIND M. ANDERSEN DAG OLAV ØVSTEDAL ATLE T. PEDERSEN ÅSE RAKNES 《Journal of food science》1996,61(4):703-706
Three red onion (Allium cepa) cultivars, top onion (A. cepa var. vivi-parum), A. altaicum and chive (A. schoenoprasum) contained several or all of the following anthocyanins: 3-(6′-malonyl-3′-glucosylglucoside), 3-(3′,6′-dimalonylglucoside), 3-(6′-malonylglucoside), 3-(3′-malonyl-glucoside), 3-(3′-glucosylglucoside) and 3-glucoside of cyanidin. Trace amounts of two pelargonidin derivatives and the 3,5-diglucosides of cyanidin and peonidin were for the first time reported in red onion. Carbon NMR data showed that the sugars of the 3-(6′-malonyl-3′-glu-cosylglucoside), 3-(6′-malonylglucoside) and 3-glucoside of cyanidin were pyranoses. Substitution either by sugar or acid in the sugar 3-position of an anthocyanin has never been reported outside the genus Allium. 相似文献
110.