全文获取类型
收费全文 | 103098篇 |
免费 | 8696篇 |
国内免费 | 4400篇 |
专业分类
电工技术 | 6129篇 |
技术理论 | 7篇 |
综合类 | 6911篇 |
化学工业 | 17684篇 |
金属工艺 | 6183篇 |
机械仪表 | 6344篇 |
建筑科学 | 8927篇 |
矿业工程 | 3004篇 |
能源动力 | 2737篇 |
轻工业 | 6934篇 |
水利工程 | 1853篇 |
石油天然气 | 5850篇 |
武器工业 | 846篇 |
无线电 | 11026篇 |
一般工业技术 | 12177篇 |
冶金工业 | 4946篇 |
原子能技术 | 1217篇 |
自动化技术 | 13419篇 |
出版年
2024年 | 466篇 |
2023年 | 1839篇 |
2022年 | 3117篇 |
2021年 | 4233篇 |
2020年 | 3270篇 |
2019年 | 2693篇 |
2018年 | 3074篇 |
2017年 | 3465篇 |
2016年 | 3024篇 |
2015年 | 4008篇 |
2014年 | 4978篇 |
2013年 | 6089篇 |
2012年 | 6805篇 |
2011年 | 7043篇 |
2010年 | 6085篇 |
2009年 | 5854篇 |
2008年 | 5638篇 |
2007年 | 5441篇 |
2006年 | 5548篇 |
2005年 | 4850篇 |
2004年 | 3265篇 |
2003年 | 2749篇 |
2002年 | 2520篇 |
2001年 | 2244篇 |
2000年 | 2472篇 |
1999年 | 2807篇 |
1998年 | 2270篇 |
1997年 | 1848篇 |
1996年 | 1884篇 |
1995年 | 1523篇 |
1994年 | 1250篇 |
1993年 | 886篇 |
1992年 | 721篇 |
1991年 | 563篇 |
1990年 | 412篇 |
1989年 | 342篇 |
1988年 | 275篇 |
1987年 | 194篇 |
1986年 | 130篇 |
1985年 | 92篇 |
1984年 | 59篇 |
1983年 | 38篇 |
1982年 | 46篇 |
1981年 | 36篇 |
1980年 | 26篇 |
1979年 | 6篇 |
1978年 | 2篇 |
1965年 | 2篇 |
1959年 | 4篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
Yawei Li Shaobai Sang Shengli Jin Chunyan Yang Nan Li 《Journal of Materials Science》2006,41(18):5815-5819
Synthesis of Mg-α-Sialon has been investigated by the mixture of silicon, aluminum and magnesia powders in a flowing nitrogen atmosphere in the range of 1300–1600 °C, when Mg-α-Sialon is designed with a chemical formulation of Mg
x
Si12−3x
Al3x
O
x
N16−x
in present work. The results showed that Mg-α-sialon initially occurred at 1400 °C and basically increased with elevated temperatures. For the samples of x = 0.6, 0.8 and 1.0 the products mainly consisted of Mg-α-Sialon with small amounts of Si, AlN and 21R AlN-polytypoid phases at 1600° C. However, in final products of x = 1.2, 1.4 and 1.6 only a little of Mg-α-Sialon formed and a great amount of Si remained in these samples at all the fired temperatures. Fortunately, the content of Mg-α-Sialon in these samples were obviously increased by adding a small amount of α-Si3N4 as seeds before nitridation. 相似文献
92.
川西平原属沉积平原,不到2m厚的表土下面全是沙卵石,沙卯石厚度达二、三十米。地面覆盖农田,沟垄纵横,限制了车载钻机的进入。以往地震勘探多采取浅井组合方式激发,所获得的地震资料能量差、面波强,对农田破坏面积大。若使用SH30—2A型轻便工程钻机,配上自制的冲击管,采取冲击钻进,从管中下药柱的方式,可实现沙卵石地区的深井激发,提高资料采集质量,且效率高、成本低。 相似文献
93.
Shu‐Li Sun Jing Ma Nan Lv 《International Journal of Adaptive Control and Signal Processing》2008,22(10):932-948
Based on the optimal fusion estimation algorithm weighted by scalars in the linear minimum variance sense, a distributed optimal fusion Kalman filter weighted by scalars is presented for discrete‐time stochastic singular systems with multiple sensors and correlated noises. A cross‐covariance matrix of filtering errors between any two sensors is derived. When the noise statistical information is unknown, a distributed identification approach is presented based on correlation functions and the weighted average method. Further, a distributed self‐tuning fusion filter is given, which includes two stage fusions where the first‐stage fusion is used to identify the noise covariance and the second‐stage fusion is used to obtain the fusion state filter. A simulation verifies the effectiveness of the proposed algorithm. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
94.
Y. L. Hao R. Yang M. Niinomi D. Kuroda Y. L. Zhou K. Fukunaga A. Suzuki 《Metallurgical and Materials Transactions A》2003,34(4):1007-1012
Alloys for implant devices require improved strength but a reduced Young’s modulus, in order to become mechanically more compatible
with adjacent bone tissues. In this study, a new metastable β-type titanium alloy, Ti-29Nb-13Ta-4.6Zr (wt pct), was subjected to aging treatment to produce different microstructures,
and the resulting mechanical properties, including the Young’s modulus, were measured. The Young’s modulus of this alloy is
found to be sensitive to microstructures generated by various heat treatments. For microstructures varying from (α + β) to (α + β + ω) and (β + ω), the Young’s modulus increases with an accompanying increase in tensile strength and hardness, but decreases in ductility.
The (β + ω) microstructure has a low strength, high modulus, and poor ductility and cannot be used for biomedical applications. For
an (α + β) microstructure, the volume fraction of the phases is shown to be the main factor that determines the mechanical properties. 相似文献
95.
96.
The Clopper-Pearson confidence interval has ever been documented as an exact approach in some statistics literature. More recently, such approach of interval estimation has been introduced to probabilistic control theory and has been referred as non-conservative in control community. In this note, we clarify the fact that the so-called exact approach is actually conservative. In particular, we derive analytic results demonstrating the extent of conservatism in the context of probabilistic robustness analysis. This investigation encourages seeking better methods of confidence interval construction for robust control purpose. 相似文献
97.
LaNiO3 was synthesized by sol-gel method in which lanthanum nitrate and nickel nitrate were used as start materials and citric acid was used as complex for gel formation.The precursor was dried and subsequently heated at elevated temperature to form the desired product.XRD analysis shows that pure LaNiO3 was synthesized.Electrical conductivity and electrochemical performance of the material were tested.The electrical conductivity decreases from 34.5that there are current peaks in the curve, which is the evidence of the electrochemical activity of LaNiO3. 相似文献
98.
99.
100.