全文获取类型
收费全文 | 61358篇 |
免费 | 7308篇 |
国内免费 | 4259篇 |
专业分类
电工技术 | 8121篇 |
技术理论 | 1篇 |
综合类 | 5958篇 |
化学工业 | 6287篇 |
金属工艺 | 5086篇 |
机械仪表 | 4758篇 |
建筑科学 | 3130篇 |
矿业工程 | 3484篇 |
能源动力 | 2225篇 |
轻工业 | 2075篇 |
水利工程 | 1422篇 |
石油天然气 | 6096篇 |
武器工业 | 838篇 |
无线电 | 6692篇 |
一般工业技术 | 8176篇 |
冶金工业 | 2832篇 |
原子能技术 | 994篇 |
自动化技术 | 4750篇 |
出版年
2024年 | 304篇 |
2023年 | 1044篇 |
2022年 | 1783篇 |
2021年 | 2058篇 |
2020年 | 2063篇 |
2019年 | 1805篇 |
2018年 | 1709篇 |
2017年 | 2318篇 |
2016年 | 2477篇 |
2015年 | 2578篇 |
2014年 | 3476篇 |
2013年 | 3532篇 |
2012年 | 4379篇 |
2011年 | 4707篇 |
2010年 | 3409篇 |
2009年 | 3535篇 |
2008年 | 3165篇 |
2007年 | 4026篇 |
2006年 | 3763篇 |
2005年 | 3215篇 |
2004年 | 2675篇 |
2003年 | 2508篇 |
2002年 | 1971篇 |
2001年 | 1604篇 |
2000年 | 1558篇 |
1999年 | 1305篇 |
1998年 | 1050篇 |
1997年 | 953篇 |
1996年 | 826篇 |
1995年 | 646篇 |
1994年 | 567篇 |
1993年 | 409篇 |
1992年 | 305篇 |
1991年 | 234篇 |
1990年 | 215篇 |
1989年 | 222篇 |
1988年 | 127篇 |
1987年 | 74篇 |
1986年 | 53篇 |
1985年 | 44篇 |
1984年 | 58篇 |
1983年 | 33篇 |
1982年 | 46篇 |
1981年 | 17篇 |
1980年 | 14篇 |
1979年 | 11篇 |
1978年 | 4篇 |
1975年 | 5篇 |
1959年 | 9篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
乙炔在磁稳定床中的选择性加氢研究 总被引:1,自引:0,他引:1
制备了一种磁性Pd/Al2O3催化剂,采用磁稳定床考察了活性组分负载量、反应条件及CO浓度对乙炔加氢反应性能的影响。结果表明,当反应温度80℃、反应压力1.5MPa、空速9000h-1、磁场强度(H)25kA/m时,乙炔转化率为100%,乙烯选择性可达81%,具有优良的乙炔加氢活性和乙烯选择性,优于相同反应条件下的进口催化剂;250h稳定性实验结果表明,磁性Pd/Al2O3催化剂具有良好的初活性和乙烯选择性,催化剂性能稳定。 相似文献
92.
从理论计算分离器处理能力和现场开展试验两方面入手,对靖边气田目前在用的不同规格分离器的分离效果进行了对比分析,通过对现场数据统计和整理,得到了靖边气田不同规格分离器合理的处理气量,给气田开发建设中分离器的选型和维护改造中分离器的调整提供了依据。 相似文献
93.
94.
The present work is devoted to measure the absolute magnetic field produced by different coils in the EGYPTOR tokamak using a calibrated pickup coil. Scaling these measurements in different equations connected with the discharge currents from each supply system are performed. The pickup coil used in the present study is well calibrated with Helmholz coils at the IPP in Prague, Czech Republic. A 0.2% deviation has been found between an evaluation done in the present study and the calibration using Helmholz coils. Experimental measurements of the toroidal magnetic field are in good agreement with calculations to within 2%. Very low values of stray magnetic field components arising from TF and OH coils are recorded which proves that the compensation coils for these components are sufficient. 相似文献
95.
Shunsuke Ohashi 《Electrical Engineering in Japan》2005,150(1):71-77
Magnetic bearing using pinning force of a permanent magnet and a high‐temperature superconductor has been developed. Additional permanent magnet is introduced to increase the levitation force of the magnetic bearing. In this hybrid magnetic bearing system, levitation force is mainly given by the repulsive force of the permanent magnets, and stability for the lateral direction is given by pinning force of the superconductor. The experimental device is developed. A ring‐type superconductor and a bulk one are examined. Levitation characteristics of the hybrid magnetic bearing are measured. The bulk superconductor shows better characteristics of both levitation and lateral stability than the ring one. Levitation force of the hybrid system becomes about twice as large as that of the nonhybrid one. Although, the repulsive force of the permanent magnet decreases the lateral stability of the system, its influence becomes small by choosing an adequate position of the permanent magnets and the superconductor. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(1): 71–77, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10350 相似文献
96.
Kotaro Matsuuchi Tadashi Fukami Nobuyuki Naoe Ryoichi Hanaoka Shinzo Takata Toshio Miyamoto 《Electrical Engineering in Japan》2005,150(2):43-49
This paper presents a method of predicting the steady‐state performance of a new hybrid‐excitation synchronous machine (HESM) theoretically. The field pole of this HESM is axially divided into two parts; one is an excitation part and the other a permanent‐magnet (PM) part. A nonlinear equivalent circuit, which can include the saliency of the rotor and the magnetic saturation due to the iron core, is derived. Based on this equivalent circuit, the steady‐state performance of the HESM is calculated, and the results are confirmed through experiments. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(2): 43–49, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20033 相似文献
97.
雅克拉凝析气田高压脱水工艺的成功应用 总被引:6,自引:2,他引:4
雅克拉凝析气田位于新疆阿克苏境内,2005年11月29日建成投运的260×104m3/d雅克拉集气处理站是目前中石化最大的高压凝析气处理装置。该站的高压分子筛脱水工艺为两塔流程,采用差压再生(吸附压力5.9 MPa、再生压力2.8 MPa)、再生气自动回收工艺技术,并采用时序控制程序自动切换,具有工艺简单可靠、自动化程度高、热能利用率高、脱水露点深度高、操作维护简单、投资较少、运行成本低等优点,自建成投产以来运行稳定,效果十分显著。该工艺装置的成功应用,对类似脱水装置设计、操作具有一定参考价值。 相似文献
98.
NUMERICAL ANALYSIS AND EXPERI- MENT OF UNSTEADY THERMAL FIELD OF ROTOR PLATE FOR EDDY CURRENT RETARDER 总被引:3,自引:0,他引:3
LIU Chengye HE Ren 《机械工程学报(英文版)》2008,21(4):71-75
The physical model based on heat transfer theory and virtual boundary method for analyzing unsteady thermal field of rotor plate for eddy current retarder used in automobile is established and boundary conditions are also defined. The finite element governing equation is derived by Galerkin method. The time differential item is discrete based on Galerkin format that is stable at any condition. And a new style of varying time step method is used in iteration process. The thermal field on the rotor plate at the radial and axle directions is analyzed and varying temperature at appointed points on two side-surfaces is measured. The testing and analytical data are uniform approximately. Finite element method can be used for estimating thermal field of the rotor plate at initial design stage of eddy current retarder. 相似文献
99.
100.
This study examined how 1 symbol is selected to control the allocation of attention when several symbols appear in the visual field. In Experiments 1-3, the critical target feature was color, and it was found that uninformative central arrows that matched the color of the target were selected and produced unintentional shifts of attention (i.e., involuntary, initiated slowly, producing long-lasting facilitatory effects). Experiment 4 tested whether such selection is the result of an attentional filter or of a competition bias due to a match of incoming information against integrated object representations stored in working memory. Here, the critical feature was shape and color was irrelevant, but matching color arrows were still selected. Thus, features of objects in working memory will bias the selection of symbols in the visual field, and such selected symbols are capable of producing unintentional shifts of attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献