全文获取类型
收费全文 | 111809篇 |
免费 | 11024篇 |
国内免费 | 6803篇 |
专业分类
电工技术 | 8030篇 |
技术理论 | 3篇 |
综合类 | 8305篇 |
化学工业 | 16937篇 |
金属工艺 | 6888篇 |
机械仪表 | 7644篇 |
建筑科学 | 8418篇 |
矿业工程 | 3279篇 |
能源动力 | 3703篇 |
轻工业 | 8049篇 |
水利工程 | 2601篇 |
石油天然气 | 4752篇 |
武器工业 | 1286篇 |
无线电 | 14193篇 |
一般工业技术 | 12903篇 |
冶金工业 | 4565篇 |
原子能技术 | 1624篇 |
自动化技术 | 16456篇 |
出版年
2024年 | 449篇 |
2023年 | 1441篇 |
2022年 | 2879篇 |
2021年 | 4238篇 |
2020年 | 3163篇 |
2019年 | 2724篇 |
2018年 | 2988篇 |
2017年 | 3450篇 |
2016年 | 3317篇 |
2015年 | 4623篇 |
2014年 | 5998篇 |
2013年 | 7038篇 |
2012年 | 8318篇 |
2011年 | 9171篇 |
2010年 | 8460篇 |
2009年 | 8138篇 |
2008年 | 8173篇 |
2007年 | 7749篇 |
2006年 | 7207篇 |
2005年 | 5781篇 |
2004年 | 4337篇 |
2003年 | 3592篇 |
2002年 | 3468篇 |
2001年 | 2910篇 |
2000年 | 2333篇 |
1999年 | 1727篇 |
1998年 | 1224篇 |
1997年 | 966篇 |
1996年 | 804篇 |
1995年 | 635篇 |
1994年 | 488篇 |
1993年 | 390篇 |
1992年 | 278篇 |
1991年 | 209篇 |
1990年 | 168篇 |
1989年 | 160篇 |
1988年 | 100篇 |
1987年 | 97篇 |
1986年 | 75篇 |
1985年 | 45篇 |
1984年 | 44篇 |
1983年 | 51篇 |
1982年 | 27篇 |
1981年 | 31篇 |
1980年 | 29篇 |
1979年 | 13篇 |
1978年 | 18篇 |
1977年 | 25篇 |
1976年 | 24篇 |
1959年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 13 毫秒
31.
Studies on the deactivations and initiations of gas phase polymerizations of 1,3‐butadiene have been achieved by Monte Carlo simulation. Initiation and deactivation control the reaction before and after the peak of the polymerization rate, respectively. The influence of polymerization temperature has been studied. Monte Carlo modeling of polymerization kinetics and mechanism was confirmed by the agreement of experimental data and simulation results of polymerizations run with a temporary evacuation of monomer. The balance of catalysts and active chains is established by both initiation and chain transfer reactions with cocatalyst, which causes a ‘pseudo‐stability’ stage. © 2003 Society of Chemical Industry 相似文献
32.
Shi-Jin Ding Hang Hu Lim H.F. Kim S.J. Yu X.F. Chunxiang Zhu Li M.F. Byung Jin Cho Chan D.S.H. Rustagi S.C. Yu M.B. Chin A. Dim-Lee Kwong 《Electron Device Letters, IEEE》2003,24(12):730-732
For the first time, we successfully fabricated and demonstrated high performance metal-insulator-metal (MIM) capacitors with HfO/sub 2/-Al/sub 2/O/sub 3/ laminate dielectric using atomic layer deposition (ALD) technique. Our data indicates that the laminate MIM capacitor can provide high capacitance density of 12.8 fF//spl mu/m/sup 2/ from 10 kHz up to 20 GHz, very low leakage current of 3.2 /spl times/ 10/sup -8/ A/cm/sup 2/ at 3.3 V, small linear voltage coefficient of capacitance of 240 ppm/V together with quadratic one of 1830 ppm/V/sup 2/, temperature coefficient of capacitance of 182 ppm//spl deg/C, and high breakdown field of /spl sim/6 MV/cm as well as promising reliability. As a result, the HfO/sub 2/-Al/sub 2/O/sub 3/ laminate is a very promising candidate for next generation MIM capacitor for radio frequency and mixed signal integrated circuit applications. 相似文献
33.
34.
Yong-Chae Jeong Si-Gyun Jeong Jong-Sik Lim Sangwook Nam 《Microwave and Wireless Components Letters, IEEE》2003,13(12):538-540
A new /spl lambda//4 bias line combined by a dumb-bell shaped defected ground structure (DGS) is proposed to suppress harmonics in power amplifiers. The proposed DGS bias line maintains the required high impedance even after DGS is inserted, while the width and length of the /spl lambda//4 bias line are broader and shorter than those of conventional bias lines. When the DGS bias line is used in power amplifiers, the third harmonic components as well as the second harmonic are reduced, because of the increased slow-wave effect over wide harmonic band. It is shown that the reduction of the third harmonic component, the improvement of 1 dB compression point, and power added efficiency are 26.5 dB, 0.45 dB, and 9.1%, respectively. 相似文献
35.
36.
37.
W. Lim C. K. Wang 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1996,370(2-3):568-572
The one-dimensional (1D) position-sensitive superheated-liquid-droplet dosimeter (SLDD) has been fabricated and tested in the laboratory. The 1D SLDD is fabricated from a 9.525-mm OD, 6.35-mm ID, 20-cm long, Plexiglas-walled tube filled with a mixture of superheated-liquid Freon droplets and host medium glycerol. Washer-shaped piezoelectric acoustic transducers are positioned at both ends of the tube; they determine the number and positions of the acoustic events when the superheated-liquid droplets evaporate upon neutron irradiation. The SLDD is irradiated with the 137Cs and 60Co γ-sources, as well as 252Cf neutron source to test for its radiation response and spatial resolution. The SLDD based on the Freon-134a superheated-liquid droplets operating at 20°C and 1 atm is found to be ideal for measuring absorbed neutron dose. This study also proves that the positions of the radiation-induced nucleation acoustic events can be linearly determined from the differences in the transmission times received by the acoustic transducers on the 1D SLDD. The spatial resolution of the neutron depth-dose is 1 mm due the finite response time (1 μs) of the piezoelectric acoustic transducers. 相似文献
38.
The effect of high oxide field stress is studied using capacitance-time (C-t) measurements of MOS capacitors. The stress results in parallel shifts of the C-t curve along the time axis. The flatband voltage shift ΔVFB obtained from the initial deep depletion capacitance C(t=0+) follows the same trend as that from the high-frequency C-V characteristics. However, the discrepancy between the two flatband voltages becomes larger as the stress increases due to the effect of interface charges on C-t characteristics. The flatband voltage difference is converted to interface trap density, showing a steady increase of interface trap density with stress, similar to that from low-frequency C-V measurements 相似文献
39.
本文在分析了双眼立体视觉面临的本质困难之后,提出了用金字塔图法匹配特征基元的三眼立体视觉方法,这种方法由于建筑在透视投影几何原理的稳固基础上,无须任何先验限制,也不以图象相似性为基础,故可较好地解决精度与匹配难度的矛盾,且运用金字塔图法进行匹配传播使在保证精度的基础上,匹配速度大大提高,对计算机人工图象的匹配结果表明,误匹配率几乎为零,且有较高的匹配速度和精度。 相似文献
40.
Summary This paper presents the free vibration of thin doubly-curved shallow shells of rectangular planform. The study covers wide combinations of free, simply supported and clamped boundary conditions. Both positive and negative Gaussian curvatures (spherical and hyperbolic paraboloidal shells resepectively) are considered. Thepb-2 Ritz energy based approach, along with the in-plane and transverse deflections assumed in the form of a product of mathematically complete two-dimensional orthogonal polynomials and a basic function, is employed to model the vibratory characteristic of these shells. Numerical results have been established through convergence study and comparison with published data from the open literature. Extensive sets of new results for various ranges of aspect ratio, curvature ratio andx- andy-shallowness ratios have been presented for future reference. 相似文献