全文获取类型
收费全文 | 46175篇 |
免费 | 4387篇 |
国内免费 | 2091篇 |
专业分类
电工技术 | 2573篇 |
技术理论 | 2篇 |
综合类 | 2944篇 |
化学工业 | 7811篇 |
金属工艺 | 2622篇 |
机械仪表 | 2828篇 |
建筑科学 | 3659篇 |
矿业工程 | 1350篇 |
能源动力 | 1180篇 |
轻工业 | 4057篇 |
水利工程 | 914篇 |
石油天然气 | 2523篇 |
武器工业 | 351篇 |
无线电 | 5256篇 |
一般工业技术 | 5490篇 |
冶金工业 | 2203篇 |
原子能技术 | 525篇 |
自动化技术 | 6365篇 |
出版年
2024年 | 261篇 |
2023年 | 942篇 |
2022年 | 1656篇 |
2021年 | 2324篇 |
2020年 | 1869篇 |
2019年 | 1403篇 |
2018年 | 1566篇 |
2017年 | 1721篇 |
2016年 | 1611篇 |
2015年 | 2112篇 |
2014年 | 2572篇 |
2013年 | 3108篇 |
2012年 | 3174篇 |
2011年 | 3303篇 |
2010年 | 2883篇 |
2009年 | 2620篇 |
2008年 | 2516篇 |
2007年 | 2376篇 |
2006年 | 2389篇 |
2005年 | 1892篇 |
2004年 | 1207篇 |
2003年 | 1119篇 |
2002年 | 1022篇 |
2001年 | 884篇 |
2000年 | 832篇 |
1999年 | 923篇 |
1998年 | 759篇 |
1997年 | 694篇 |
1996年 | 608篇 |
1995年 | 512篇 |
1994年 | 399篇 |
1993年 | 303篇 |
1992年 | 218篇 |
1991年 | 183篇 |
1990年 | 141篇 |
1989年 | 131篇 |
1988年 | 97篇 |
1987年 | 71篇 |
1986年 | 62篇 |
1985年 | 32篇 |
1984年 | 26篇 |
1983年 | 24篇 |
1982年 | 22篇 |
1981年 | 19篇 |
1980年 | 18篇 |
1979年 | 11篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1968年 | 4篇 |
1959年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Sosnowchik B.D. Azevedo R.G. Cao A. Lin L. Pisano A.P. 《Advanced Packaging, IEEE Transactions on》2005,28(4):626-634
This paper presents the rapid, low-temperature bonding between silicon and steel using the rapid thermal annealing process. Three different thin-film adhesion layer systems including silver, gold, and nickel were utilized as the intermediate bonding material to assist the eutectic Pb/Sn bonding between silicon and steel. The bonding temperature was set at 220/spl deg/C for 20 s, with a 20-s ramp-up time. Five experiments were conducted to determine the strength of the bond, including static tensile and compressive four-point bend tests, axial extension tests, tensile bending fatigue tests, and corrosion resistance tests. The test results have shown that the gold adhesion layer is the most robust, demonstrating minimal creep during fatigue tests, no delamination during the tensile or compressive four-point bend tests, and acceptable strength during the axial extension tests. Additionally, all adhesion layers have withstood four months of submersion in various high-temperature solutions and lubricants without failure. Simulations of the axial stresses and strains that developed during the four-point bend and axial extension tests were performed and showed that the presence of the silicon die provides a local reinforcement of the bond as observed in the experimental tests. 相似文献
32.
棉织物手感值的模糊综合评判研究 总被引:4,自引:0,他引:4
利用模糊综合评判数学模型对棉织物的手感值进行了计算与分析,这种方法简单、可靠,与主观评估结果有很好的一致性,为纺织生产的质量判断提供了便利。 相似文献
33.
文章通过对五口井的现场应用介绍,阐述了快速色谱分析技术在油气层识别和解释方面的准确性,探讨了该技术在薄油气层的发现和评价、快速钻进条件下油气层的发现、对油气层全烃组份变化的统一、水平井的地质导向以及排除钻井液添加荆对油气显示的影响五个方面的优势,从而论证了快速色谱分析技术在油气勘探中的应用价值。 相似文献
34.
Calculations and detailed first principle and thermodynamic analyses have been performed to understand the formation mechanism of K2Ti6O13 nanowires (NWs) by a hydrothermal reaction between bulk Na2Ti3O7 crystals and a KOH solution. It is found that direct ion exchange between K+ and Na+ plus H+ interactions with [TiO6] octahedra in Na2Ti3O7 promote the formation of an intermediate H2K2Ti6O14 phase. The large lattice mismatch between this intermediate phase and the bulk Na2Ti3O7 structure, and the large energy reduction associated with the formation of this intermediate phase, drive the splitting of the bulk crystal into H2K2Ti6O14 NWs. However, these NWs are not stable because of large [TiO6] octahedra distortion and are subject to a dehydration process, which results in uniform K2Ti6O13 NWs with narrowly distributed diameters of around 10 nm. 相似文献
35.
3-D MCM封装技术及其应用 总被引:1,自引:0,他引:1
介绍了超大规模集成电路(VLSI)用的3-D MCM封装技术的最新发展,重点介绍了3-D MCM封装垂直互连工艺,分析了3-D MCM封装技术的硅效率、复杂程度、热处理、互连密度、系统功率与速度等问题,并对3-D MCM封装的应用作了简要说明。 相似文献
36.
Jiayong Cao Yu Zhu Jinsong Wang Wensheng Yin Guanghong Duan 《IEEE transactions on magnetics》2004,40(6):3490-3494
This paper investigates three kinds of permanent-magnet arrays used in planar motors with polarity centers distributed in the lattices of a matrix. The magnetic field of every kind of magnet array is analyzed by analytical methods. First, we give a Laplace equation of magnetic scalar potential and a series of boundary conditions. Then, we derive the analytical expressions of magnet field strength and magnet flux density in the air gap of each kind of magnet array by the method of separation of variables. Finally, we compare the three types of magnet arrays on the basis of the analytical solutions. 相似文献
37.
Yung Ting Liang-Chiang Chen Chun-Chung Li Jeng-Lin Huang 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2007,54(4):847-853
A new type of piezoelectric linear motor incorporating a traveling wave has been developed. The linear motor is comprised of a stator and a carriage. The stator design, which consists of a meander-line structure and gear teeth mounted on the meander-line structure, is the focus of this article. The meander-line structure is constructed with bimorph actuators arranged in a line. These actuators are driven by two phased sets of alternating current (ac) in order to generate a traveling wave. The traveling wave is transferred to the gear teeth, by which the carriage is driven. Modeling of the stator is derived by use of a strain energy method. The performance of various materials is evaluated by analytical and experimental methods. The analytical and the experimental results are quite approximate. Modal analysis is investigated using ANSYS. Appropriate modes associated with ultrasonic levels of resonant frequency are selected to obtain desired motion and to enhance the output performance. Surface speed for various applied input voltage are studied and indicate a nearly linear relationship. The stator in combination with the carriage makes up the linear motor. 相似文献
38.
Domain-Driven, Actionable Knowledge Discovery 总被引:1,自引:0,他引:1
Data mining increasingly faces complex challenges in the real-life world of business problems and needs. The gap between business expectations and R&D results in this area involves key aspects of the field, such as methodologies, targeted problems, pattern interestingness, and infrastructure support. Both researchers and practitioners are realizing the importance of domain knowledge to close this gap and develop actionable knowledge for real user needs. 相似文献
39.
Xi-Ren Cao Han-Fu Chen 《Automatic Control, IEEE Transactions on》1997,42(10):1382-1393
Two fundamental concepts and quantities, realization factors and performance potentials, are introduced for Markov processes. The relations among these two quantities and the group inverse of the infinitesimal generator are studied. It is shown that the sensitivity of the steady-state performance with respect to the change of the infinitesimal generator can be easily calculated by using either of these three quantities and that these quantities can be estimated by analyzing a single sample path of a Markov process. Based on these results, algorithms for estimating performance sensitivities on a single sample path of a Markov process can be proposed. The potentials in this paper are defined through realization factors and are shown to be the same as those defined by Poisson equations. The results provide a uniform framework of perturbation realization for infinitesimal perturbation analysis (IPA) and non-IPA approaches to the sensitivity analysis of steady-state performance; they also provide a theoretical background for the PA algorithms developed in recent years 相似文献
40.
空调器用盘式电机的计算机模拟 总被引:1,自引:0,他引:1
介绍线绕盘式永磁直流电流电动机的结构特点,设计原则和有关的主要设计公式,并进行电机的计算机模拟。模拟运行结果与样机实测数据基本相符。 相似文献