全文获取类型
收费全文 | 358467篇 |
免费 | 31767篇 |
国内免费 | 17647篇 |
学科分类
工业技术 | 407881篇 |
出版年
2024年 | 1159篇 |
2023年 | 5287篇 |
2022年 | 9755篇 |
2021年 | 14384篇 |
2020年 | 10668篇 |
2019年 | 8634篇 |
2018年 | 9640篇 |
2017年 | 11163篇 |
2016年 | 10059篇 |
2015年 | 14131篇 |
2014年 | 18239篇 |
2013年 | 22653篇 |
2012年 | 24626篇 |
2011年 | 26715篇 |
2010年 | 23696篇 |
2009年 | 22848篇 |
2008年 | 22143篇 |
2007年 | 21134篇 |
2006年 | 20483篇 |
2005年 | 17112篇 |
2004年 | 11829篇 |
2003年 | 10234篇 |
2002年 | 9553篇 |
2001年 | 8545篇 |
2000年 | 7856篇 |
1999年 | 7929篇 |
1998年 | 6730篇 |
1997年 | 5503篇 |
1996年 | 5029篇 |
1995年 | 4239篇 |
1994年 | 3530篇 |
1993年 | 2657篇 |
1992年 | 2073篇 |
1991年 | 1540篇 |
1990年 | 1227篇 |
1989年 | 1061篇 |
1988年 | 802篇 |
1987年 | 572篇 |
1986年 | 450篇 |
1985年 | 352篇 |
1984年 | 228篇 |
1983年 | 202篇 |
1982年 | 183篇 |
1981年 | 175篇 |
1980年 | 168篇 |
1979年 | 120篇 |
1978年 | 72篇 |
1977年 | 72篇 |
1976年 | 86篇 |
1975年 | 46篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
Ku T.K. Chen S.H. Yang C.D. She N.J. Wang C.C. Chen C.F. Hsieh I.J. Cheng H.C. 《Electron Device Letters, IEEE》1996,17(5):208-210
Undoped and phosphorus (P)-doped diamond-clad Si field emitter arrays have been successfully fabricated using microwave plasma chemical vapor deposition (MPCVD) technology. The electron emission from the blunt diamond-clad microtips are much higher than those for the pure Si tips with sharp curvature due to a lower work function. Furthermore, the characteristics of emission current against applied voltage for the P-doped diamond-clad tips show superior emission at lower field to the undoped ones. After the examination of Auger electron spectroscopy (AES) and electrical characteristics of as-grown diamond, such a significant enhancement of the electron emission from the P-doped diamond-clad tips is attributed to a higher electron conductivity and defect densities 相似文献
952.
953.
提出了映射半解析边界元法解百轴对称瞬态弹性动力问题时存在解析方向不能正确反映波的传播现象的问题,产生该问题的原因和如何解决该问题的建议。 相似文献
954.
通过合成的一系列具有不同分子量的聚丙烯酰胺的阳离子化制得具有不同分子参数的阳离子聚丙烯酰胺(CPAM)。经评价实验就分子参数对页岩抑制性的影响进行研究 相似文献
955.
A simple and elegant proof is given for a recurrence relation that computes the coefficients of the characteristic polynomial of a linear system used in the Souriau-Frame-Faddeev algorithm 相似文献
956.
A BiCMOS dynamic carry lookahead circuit that is free from race problems is presented. A 16 b full-adder test circuit, which has been designed based on a 2 μm BiCMOS technology, shows a more than five times improvement in speed as compared to the CMOS Manchester carry lookahead (MCLA) circuit. The speed advantage of the BiCMOS dynamic carry lookahead circuit is even greater in a 32- or 64-b adder 相似文献
957.
Cheng-Hsiung Lid Shou-Chiung Chen Yung-Chi Lee Theodore D. Sokoloski Ming-Thau Sheu 《Drug development and industrial pharmacy》1994,20(11):1911-1922
Polyvinylpyrrolidone (PVP) in aqueous solution was used as a binding agent in a fluidized-bed system to agglomerate acetaminophen powder into directly compressible granules. It was found that a minimal amount of 5% w/w PVP in a concentration of 7.5% w/v or less was needed to produce granules with an acceptable flow and the corresponding tablets having enough hardness without capping. There was a strong correlation between the time for 80% dissolved (T80) and the logarithm of granule volume-surface mean diameter. A directly compressible acetaminophen composition to manufacture tablets having a T80 value less than 30 min can be prepared simply by adding an appropriate amount of disintegrant (crospovidone, sodium starch glycolate, or pregelatinized starch) to the agglomerated granules. 相似文献
958.
959.
Wen-Chau Liu Lih-Wen Laih Shiou-Ying Cheng Wen-Lung Chang Wei-Chou Wang Jing-Yuh Chen Po-Hung Lin 《Electron Devices, IEEE Transactions on》1998,45(2):373-379
In this paper, a new multiple negative-differential-resistance (MNDR) device based on a metal-insulator-semiconductor-insulator-metal (MISIM)-like structure with step-compositional InxGa1-x As quantum wells has been fabricated and demonstrated. The interesting MNDR phenomena are found in the current-voltage (I-V) characteristics of this device. At room temperature, the triple switching behaviours and quadruple stable operation states are obtained. In addition, the sixfold switching behaviors and a staircase-shaped I-V characteristic are observed at -105°C. A sequential carrier accumulation at InGaAs subwells and the potential lowering process are used to qualitatively explain the interesting MNDR phenomena. From the experimental results, it is shown that the studied device has good potential in multiple-valued logic applications 相似文献
960.
从冷却曲线上相变段倾角最小原则出发,研究了新型激冷剂的配比与热分析法检测铸铁成分精度的关系,实验结果表明,能使相变段倾角最小的成分配比,也能提高对铸铁成分的热分析和检测精度。 相似文献