全文获取类型
收费全文 | 73353篇 |
免费 | 5701篇 |
国内免费 | 2776篇 |
专业分类
电工技术 | 3874篇 |
技术理论 | 6篇 |
综合类 | 4428篇 |
化学工业 | 12711篇 |
金属工艺 | 3948篇 |
机械仪表 | 4811篇 |
建筑科学 | 5195篇 |
矿业工程 | 2404篇 |
能源动力 | 2236篇 |
轻工业 | 4777篇 |
水利工程 | 1007篇 |
石油天然气 | 5300篇 |
武器工业 | 460篇 |
无线电 | 7706篇 |
一般工业技术 | 9437篇 |
冶金工业 | 3938篇 |
原子能技术 | 750篇 |
自动化技术 | 8842篇 |
出版年
2024年 | 303篇 |
2023年 | 1273篇 |
2022年 | 2108篇 |
2021年 | 2892篇 |
2020年 | 2202篇 |
2019年 | 1969篇 |
2018年 | 2309篇 |
2017年 | 2505篇 |
2016年 | 2077篇 |
2015年 | 2699篇 |
2014年 | 3439篇 |
2013年 | 4226篇 |
2012年 | 4345篇 |
2011年 | 4860篇 |
2010年 | 4176篇 |
2009年 | 3958篇 |
2008年 | 3852篇 |
2007年 | 3712篇 |
2006年 | 3811篇 |
2005年 | 3440篇 |
2004年 | 2290篇 |
2003年 | 2091篇 |
2002年 | 1875篇 |
2001年 | 1642篇 |
2000年 | 1812篇 |
1999年 | 2068篇 |
1998年 | 1776篇 |
1997年 | 1431篇 |
1996年 | 1413篇 |
1995年 | 1187篇 |
1994年 | 959篇 |
1993年 | 718篇 |
1992年 | 546篇 |
1991年 | 428篇 |
1990年 | 327篇 |
1989年 | 255篇 |
1988年 | 226篇 |
1987年 | 142篇 |
1986年 | 120篇 |
1985年 | 96篇 |
1984年 | 67篇 |
1983年 | 40篇 |
1982年 | 42篇 |
1981年 | 30篇 |
1980年 | 25篇 |
1979年 | 13篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1975年 | 5篇 |
1945年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
Wei Feng Jianping Wen Xiaoqiang Jia Qing Yuan Yan Sun Cuiyun Liu 《American Institute of Chemical Engineers》2006,52(8):2864-2875
A coupled three-dimensional (3-D) model, combining hydrodynamics with biochemical reactions, was developed to simulate the local transient flow patterns and the dynamic behaviors of cell growth and phenol biodegradation by yeast Candida tropicalis in the bubble-column bioreactor, using the computational fluid dynamic (CFD) method. In order to validate this proposed model effectively, the validation of the local hydrodynamic characteristics of the gas-mineral salt solution (gas-liquid) two-phase system, with the phenol concentration of 1200 mg/L, and with the absence of cells, was performed in a square-sectioned bubble column bioreactor using the LDA system and conductivity probe. Furthermore, the validation of phenol biodegradation behaviors by yeast Candida tropicalis at different initial concentrations of phenol and cell was also carried out in the above bubble-column bioreactor. The results indicated that the model simulations had a satisfying agreement with the experimental data. Finally, the local instantaneous flow and phenol biodegradation features including gas holdup, gas velocity, liquid velocity, cell concentration and phenol concentration inside the bioreactor were successfully predicted in different-scale bubble columns by the proposed model. © 2006 American Institute of Chemical Engineers AIChE J, 2006 相似文献
152.
L. A. Kosyachenko I. M. Rarenko E. F. Sklyarchuk I. I. German Sun Weiguo 《Semiconductors》2006,40(5):554-557
Photodiodes designed to be sensitive in the region 0.5–1.7 μm and obtained by vacuum magnetron sputtering of the ITO (SnO2 + In2O3) layer on the surface of the Hg3In2Te6 single crystal are studied. The electrical characteristics, measured at 265–333 K, indicate that the mechanism of charge
transport in the diodes under study is thermionic. The current-voltage characteristic and its temperature variations are described
quantitatively based on the energy diagram and the found parameters of the heterojunction.
Original Russian Text ? L.A. Kosyachenko, I.M. Rarenko, E.F. Sklyarchuk, I.I. German, Sun Weiguo, 2006, published in Fizika
i Tekhnika Poluprovodnikov, 2006, Vol. 40, No. 5, pp. 568–571. 相似文献
153.
Hydrate formation rate plays an important role in making hydrates for the storage and transport of natural gas. Micellar surfactant solutions were found to increase gas hydrate formation rate and storage capacity. With the presence of surfactant, hydrate could form quickly in a quiescent system and the energy costs of hydrate formation reduced. Surfactants (an anionic surfactant, a non‐ionic surfactant and their mixtures) and liquid hydrocarbons (cyclopentane and methylcyclohexane) were used to improve hydrate formation. The experiments of hydrate formation were carried out in the pressure range 3.69–6.82 MPa and the temperature range 274.05–277.55 K. The experimental pressures were kept constant during hydrate formation in each experimental run. The effect of anionic surfactant (sodium dodecyl sulphate (SDS)) on natural gas storage in hydrates is more pronounced compared to a non‐ionic surfactant (dodecyl polysaccharide glycoside (DPG)). The induction time of hydrate formation was reduced with the presence of cyclopentane (CP). Cyclopentane and methylcyclohexane (MCH) could increase hydrate formation rate, but reduced hydrate storage capacity The higher methylcyclohexane concentration, the lower the hydrate storage capacity. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
154.
扇形段是连铸机组中的主要设备,扇形段制造水平的高低将直接影响到板坯厚度的均匀性,对最终的钢板轧制质量起着十分重要的作用。阐述扇形段主要部件的质量控制。 相似文献
155.
The effect of pressure on combustion and heat transfer is analyzed. The research is based on the basic combustion and heat
transfer theorem. A correction for the heat calculation method for pressurized furnace is made on the basis of the normal
pressure case. The correction takes the effect of pressurizing into account. The results show that the correction is reasonable
and the method is applicable to combustion and heat transfer of the marine supercharged boiler. 相似文献
156.
157.
158.
Average consensus in networks of dynamic agents with switching topologies and multiple time-varying delays 总被引:5,自引:0,他引:5
In this paper, we discuss average consensus problem in undirected networks of dynamic agents with fixed and switching topologies as well as multiple time-varying communication delays. By employing a linear matrix inequality method, we prove that all the nodes in the network achieve average consensus asymptotically for appropriate communication delays if the network topology is connected. Particularly, several feasible linear matrix inequalities are established to determine the maximal allowable upper bound of time-varying communication delays. Numerical examples are given to demonstrate the effectiveness and the sharpness of the theoretical results. 相似文献
159.
Xin Sun Qiang Lu Moroz V. Takeuchi H. Gebara G. Wetzel J. Shuji Ikeda Changhwan Shin Tsu-Jae King Liu 《Electron Device Letters, IEEE》2008,29(5):491-493
A tri-gate bulk MOSFET design utilizing a low-aspect-ratio channel is proposed to provide an evolutionary pathway for CMOS scaling to the end of the roadmap. 3-D device simulations indicate that this design offers the advantages of a multi-gate FET (reduced variability in performance and improved scalability) together with the advantages of a conventional planar MOSFET (low substrate cost and capability for dynamic threshold-voltage control). 相似文献
160.
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