全文获取类型
收费全文 | 504996篇 |
免费 | 5547篇 |
国内免费 | 1532篇 |
专业分类
电工技术 | 9233篇 |
综合类 | 341篇 |
化学工业 | 75941篇 |
金属工艺 | 19831篇 |
机械仪表 | 15027篇 |
建筑科学 | 12206篇 |
矿业工程 | 2532篇 |
能源动力 | 13115篇 |
轻工业 | 43453篇 |
水利工程 | 5063篇 |
石油天然气 | 9483篇 |
武器工业 | 28篇 |
无线电 | 61198篇 |
一般工业技术 | 99162篇 |
冶金工业 | 94727篇 |
原子能技术 | 11448篇 |
自动化技术 | 39287篇 |
出版年
2021年 | 4005篇 |
2019年 | 3622篇 |
2018年 | 6429篇 |
2017年 | 6394篇 |
2016年 | 6775篇 |
2015年 | 4397篇 |
2014年 | 7616篇 |
2013年 | 22051篇 |
2012年 | 12122篇 |
2011年 | 16596篇 |
2010年 | 13523篇 |
2009年 | 15433篇 |
2008年 | 16085篇 |
2007年 | 15942篇 |
2006年 | 14146篇 |
2005年 | 12829篇 |
2004年 | 12132篇 |
2003年 | 12148篇 |
2002年 | 11734篇 |
2001年 | 12109篇 |
2000年 | 11282篇 |
1999年 | 11772篇 |
1998年 | 29536篇 |
1997年 | 21183篇 |
1996年 | 16331篇 |
1995年 | 12340篇 |
1994年 | 11120篇 |
1993年 | 10906篇 |
1992年 | 8036篇 |
1991年 | 7839篇 |
1990年 | 7592篇 |
1989年 | 7421篇 |
1988年 | 7242篇 |
1987年 | 6177篇 |
1986年 | 6148篇 |
1985年 | 6903篇 |
1984年 | 6441篇 |
1983年 | 6033篇 |
1982年 | 5686篇 |
1981年 | 5717篇 |
1980年 | 5504篇 |
1979年 | 5284篇 |
1978年 | 5183篇 |
1977年 | 6128篇 |
1976年 | 8124篇 |
1975年 | 4610篇 |
1974年 | 4416篇 |
1973年 | 4403篇 |
1972年 | 3811篇 |
1971年 | 3423篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
71.
In studying a series of fibre samples spun in steady-state conditions, the following was found: as a function of the conditions of processing Armos fibre, two structural modifications of the polymer can form; intensive crystallization of the modification corresponding to the 28.7° reflection begins in heat treatment above 220°C; above 320°C, intensive crystallization of the modification corresponding to the 14.25° reflection is observed; at 360°C, symbatic enhancement of the intensities of both reflections with a weak change in the other structural parameters of the fibre is observed. 相似文献
72.
Polycrystalline Cu(In,Ga)Se2 (CIGS) films with various ratios of Cu, In, and Ga were grown by codeposition of all elements in vacuum. The X-ray diffraction
study showed that the films are single-phase and possess a chalcopyrite structure with predominant [112] orientation. The
films exhibited a mirror smooth surface and had a close-packed structure composed of crystallites with clear faceting and
a transverse size of 0.1–0.3 μm. Related surface barrier structures of the (In,Ag)/Cu(In,Ga)Se2 type were obtained and their spectra of the quantum efficiency of photoconversion were studied. The obtained structures can
be used for optimization of the CIGS film technology. 相似文献
73.
Previously unknown compounds AI
I(BUO5)2·nH2O (AI
I = Mg, Ca, Sr, Ba; n = 0-7) were synthesized. Their structure and thermal decomposition were studied by X-ray diffraction, IR spectroscopy, and thermal analysis. 相似文献
74.
In this letter, bandpass filters with one or two tunable transmission zeros are proposed. The reconfigurable transmission zeros are implemented through varactors in combination with tapped quarter-wavelength stubs. Based on mixed mode simulations including EM simulation and circuit simulation, the proposed filters were designed and fabricated on low-cost FR4 board. The measurement results verified the design concepts. 相似文献
75.
Finite element piezothermoelasticity analysis and the active control of FGM plates with integrated piezoelectric sensors and actuators 总被引:3,自引:0,他引:3
An efficient finite element model is presented for the static and dynamic piezothermoelastic analysis and control of FGM
plates under temperature gradient environments using integrated piezoelectric sensor/actuator layers. The properties of an FGM plate are functionally graded in the thickness
direction according to a volume fraction power law distribution. A constant displacement-cum-velocity feedback control algorithm that couples the direct and inverse piezoelectric effects is applied to provide active feedback
control of the integrated FGM plate in a closed loop system. Numerical results for the static and dynamic control are presented
for the FGM plate, which consists of zirconia and aluminum. The effects of the constituent volume fractions and the influence
of feedback control gain on the static and dynamic responses of the FGM plates are examined.
Received: 13 March 2002 / Accepted: 5 March 2003
The work described in this paper was supported by a grant awarded by the Research Grants Council of the Hong Kong Special
Administrative Region, China (Project No. CityU 1024/01E). 相似文献
76.
In this work it is presented a study on the residence time distribution (RTD) of particles in a co-current pilot-plant spray dryer operated with a rotary atomization system. A nuclear technique is applied to investigate the RTD responses of spray dryers. The methodology is based on the injection of a radioisotope tracer in the feed stream followed by the monitoring of its concentration at the outlet stream. The experiments were performed during the drying of aqueous suspensions of gadolinium oxide. The RTD responses obtained experimentally presented good reproducibility, indicating that the technique applied is well suited to investigating fluid-dynamics of spray dryers. In addition to the experimental investigation, a mathematical model was used to describe the RTD experimental curves. 相似文献
77.
Scale Up from Small Oven-Drying Tests of Mineral Concentrate to Pilot-Scale Drying with a Heated Pad
While Fickian diffusion models are commonly used in other applications, there are few reports of them being applied to the batch drying of a mineral concentrate. Diffusion coefficients estimated from small-scale oven-drying tests were used to predict the drying behavior of a concentrate sample 1 m × 1 m in area and 50 cm deep, with a heated bottom pad. These pilot-scale tests included both daily turning of the sample and turning every three days. The excellent quantitative agreement between the predicted and observed pilot-scale behavior gives a high level of confidence in the model predictions and suggests that a Fickian diffusion model is adequate to predict the behavior of mineral concentrates at the low moisture contents used here. 相似文献
78.
79.
G. Murali Dhar B. N. Srinivas M. S. Rana Manoj Kumar S. K. Maity 《Catalysis Today》2003,86(1-4):45-60
Support effects form important aspect of hydrodesulfurization (HDS) studies and mixed oxide supports received maximum attention in the last two decades. This review will focus attention on studies on mixed oxide supported Mo and W catalysts. For convenience of discussion, these are divided into Al2O3 containing mixed oxide supports, TiO2 containing mixed oxide supports, ZrO2 containing mixed oxide supports and other mixed oxide supports containing all the rest. TiO2 containing mixed oxides received maximum attention, especially TiO2–Al2O3 supported catalysts. A brief discussion about their prospects for application to ultradeep desulfurization is also included. An overview of the available literature with emphasis on research carried out in our laboratory form the contents of this publication. 相似文献
80.
Thirty patients who had undergone either a right or left unilateral temporal lobectomy (14 RTL; 16 LTL) and 16 control participants were tested on a computerized human analogue of the Morris Water Maze. The procedure was designed to compare allocentric and egocentric spatial memory. In the allocentric condition, participants searched for a target location on the screen, guided by object cues. Between trials, participants had to walk around the screen, which disrupted egocentric memory representation. In the egocentric condition, participants remained in the same position, but the object cues were shifted between searches to prevent them from using allocentric memory. Only the RTL group was impaired on the allocentric condition, and neither the LTL nor RTL group was impaired on additional tests of spatial working memory or spatial manipulation. The results support the notion that the right anterior temporal lobe stores long-term allocentric spatial memories. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献