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41.
Copolymerizations of ethylene with 1-decene were carried out with a series of
stereospecific metallocene compounds, rac–(EBI)Zr(NMe2)2 [ 1, EBI = ethylene–1,2–bis( 1–indenyl)], rac–(EBI)Hf(NMe2 (2), rac–Me2Si( 1–C5H2–2–Me–4–
t
Bu)2Zr(NMe2)2
(3), ethylidene(cyclopentadienyl)(9-fluorenyl)ZrMe2 [4, Et(Flu)(Cp)ZrMe2] and isopropylidene(cyclopentadienyl)(9–fluorenyl)ZrMe2 [5, iPr(Flu)(Cp)ZrMe2], combined
with Al(i–Bu)3/[CPh3] [B(C6F5)4] cocatalyst. All catalyst systems showed very high
copolymerization rates and the 1–decene reactivity decreased in the order of 2 > 5 > 1 4 > 3. The reactivity product of ethylene and 1–decene (r
E x r
D) was below 1 except
3 catalyst, corresponding to random copolymer structures with an alternating
character. The melting point (Tm), crystallinity (XC), intrinsic viscosity ([] and
density of the 1–decene/ethylene copolymers decreased markedly with an increase in
the 1–decene content, regardless of the type of catalytic system. 相似文献
42.
The key to the success of flip‐chip technology lies in the availability of sucessful underfill materials. However, the reliability of flip‐chip technology using current underfill materials is generally found to be lower than that of conventional wire‐bond connection packaging materials such as epoxy molding compound (EMC) because of the high coefficients of thermal expansion (CTE) and moisture absorption of cured underfill material. In this study desbimide (DBMI), which has a low melting point (about 80°C), was used in the underfill materials as a cohardener. As a result, DBMI‐added underfill can show excellent thermal reliability, which is due to the superior properties of the CTE, the elastic modulus, and water resistance. When the properties of a 2 wt % DBMI‐added underfill were compared with those of a typical underfill (epoxy/anhydride), the CTE value was reduced to less than one‐half at the solder reflow temperature (about 200°C), the elastic modulus was reduced to less than one‐half in the temperature region below the glass‐transition temperature, and the water resistance was improved twofold. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2617–2624, 2002 相似文献
43.
J. H. Kim J. H. Park J. H. Kim T. V. Cao T. Y. Lee H. J. Ban K. Yang H. G. Kim P. B. Ha Y. H. Kim 《中南工业大学学报(英文版)》2009,16(4):621-628
A power management unit (PMU) chip supplying dual panel supply voltage, which has a low electro-magnetic interference (EMI)
characteristic and is favorable for miniaturization, is designed. A two-phase charge pump circuit using external pumping capacitor
increases its pumping current and works out the charge-loss problem by using bulk-potential biasing circuit. A low-power start-up
circuit is also proposed to reduce the power consumption of the band-gap reference voltage generator. And the ring oscillator
used in the ELVSS power circuit is designed with logic devices by supplying the logic power supply to reduce the layout area.
The PMU chip is designed with MagnaChip’s 0.25 μm high-voltage process. The driving currents of ELVDD and ELVSS are more than
50 mA when a SPICE simulation is done. 相似文献
44.
The peel and tack properties of mixtures of polystyrene-block-polybutadiene-block-polystyrene (SBS) and a tackifier were investigated after these were crosslinked by ultraviolet (UV) irradiation at various amounts of benzophenone (BP) as a photoinitiator and trimethylolpropane mercaptopropionate (TRIS) as a crosslinking agent.The degree of crosslinking of polybutadiene (PB) block in the SBS mixture was qualitatively estimated from the amount of gel fraction as well as the change in the glass transition temperature of the PB block. The crosslinking of the PB block was done within 3 min after UV irradiation and the peel strength of crosslinked specimens was as low as 45[percnt] of specimens without crosslinking. Nano-tack and bulk tack properties as well as the surface tension of mixtures were measured depending upon amounts of BP and TRIS. 相似文献
45.
根据沧州市92个雨量监测站2006~2016年间的春季大到暴雨资料,研究了11年来沧州市春季大到暴雨的特征指标、时间变化规律以及空间变化趋势.研究发现:沧州市11年间春季大到暴雨强度(站点数)的时间变化呈抛物线趋势,与沧州市年降水量变化趋势非常接近;沧州市春季大到暴雨的空间分布情况为各县市均有发生,但分布不均匀,子牙新河沿岸出现高值区,以子牙新河为界,向两侧递减. 相似文献
46.
The superplastic deformation behavior of quasi-single phase Zn-0.3 wt. %Al was investigated. A series of load relaxation and
tensile tests was conducted at various temperatures ranging from RT (20 °C) to 200 °C. The recently proposed internal variable
theory of structural superplasticity was applied. The flow curves obtained from load relaxation tests were shown to consist
of contributions from interface sliding (IS) and accommodating plastic deformation. In the case of quasi-single phase Zn-0.3
wt.% Al alloy with an average agrain size of 1 μm, the IS behavior could be described as a viscous flow process characterized
by a power index of Mg=0.5. A large elongation of about 1400% was obtained at room temperature and the strain rate sensitivity parameter was about
0.4. Although relatively large-grained (10 μm) single phase alloy showed a high value of strain rate sensitivity comparable
to that of fine-grained alloy at very low strain rate range, IS was not expected from the analysis based on the internal variable
theory of structural superplasticity at room temperature. As the temperature increased above 100 °C, however, the contribution
from IS was observed at a very low strain rate range. A high elongation of ∼400% was obtained in a specimen of 10-μm-grain-size
at 200 °C under a strain rate of 2×10−4/sec.
Jointly appointed at Center for Advanced Aerospace Materials (CAAM) 相似文献
47.
Dongwoon Jeon Doo-Hyun Kim Young-Guk Ha Vladimir Tyan 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2016,20(5):1713-1720
In this paper, we present an algorithm for providing visually-guided unmanned aerial vehicle (UAV) control using visual information that is processed on a mobile graphic processing unit (GPU). Most real-time machine vision applications for UAVs exploit low-resolution images because the shortage of computational resources comes from size, weight and power issue. This leads to the limitation that the data are insufficient to provide the UAV with intelligent behavior. However, GPUs have emerged as inexpensive parallel processors that are capable of providing high computational power in mobile environments. We present an approach for detecting and tracking lines that use a mobile GPU. Hough transform and clustering techniques were used for robust and fast tracking. We achieved accurate line detection and faster tracking performance using the mobile GPU as compared with an x86 i5 CPU. Moreover, the average results showed that the GPU provided approximately five times speedup as compared to an ARM quad-core Cortex-A15. We conducted a detailed analysis of the performance of proposed tracking and detection algorithm and obtained meaningful results that could be utilized in real flight. 相似文献
48.
Miloš Hašan Edgar Velázquez‐Armendáriz Fabio Pellacini Kavita Bala 《Computer Graphics Forum》2008,27(4):1105-1114
Rendering animations of scenes with deformable objects, camera motion, and complex illumination, including indirect lighting and arbitrary shading, is a long‐standing challenge. Prior work has shown that complex lighting can be accurately approximated by a large collection of point lights. In this formulation, rendering of animation sequences becomes the problem of efficiently shading many surface samples from many lights across several frames. This paper presents a tensor formulation of the animated many‐light problem, where each element of the tensor expresses the contribution of one light to one pixel in one frame. We sparsely sample rows and columns of the tensor, and introduce a clustering algorithm to select a small number of representative lights to efficiently approximate the animation. Our algorithm achieves efficiency by reusing representatives across frames, while minimizing temporal flicker. We demonstrate our algorithm in a variety of scenes that include deformable objects, complex illumination and arbitrary shading and show that a surprisingly small number of representative lights is sufficient for high quality rendering. We believe out algorithm will find practical use in applications that require fast previews of complex animation. 相似文献
49.
Motion synthesis with decoupled parameterization 总被引:2,自引:0,他引:2
In real-time animation systems, motion interpolation techniques are widely used for their controllability and efficiency. The techniques sample the parameter space using example motions, and interpolate them to compute the blend weights corresponding to the given parameters. A main problem of the techniques is that, as the dimension n of the parameter space increases, the number of required example motions increases exponentially, i.e. O(c n ). To resolve the problem, this paper proposes to use two decoupled parameter spaces for controlling the upper body and the lower body separately. At each frame time, a parameterized motion space produces a source frame, and the target frame is synthesized by splicing the upper body of one source frame with the lower body of the other. In order to have the two source frames correlated with each other, a time-warping scheme has been developed. Furthermore, in order to handle the dynamic properties of the parameter samples of the upper body, we have developed an approximation technique for quickly determining the sample positions in its parameter space. This decoupled parameterization method alleviates the complexity problem, e.g. from O(c 6) to O(c 3), while providing the users with the capability of convenient control over the character. 相似文献
50.
Wonpil Yu Jae-Yeong Lee Young-Guk Ha Minsu Jang Joo-Chan Sohn Yong-Moo Kwon Hyo-Sung Ahn 《Automation Science and Engineering, IEEE Transactions on》2009,6(4):633-640
This paper describes a concerted effort to design and implement a robotic service framework. The proposed framework is comprised of three conceptual spaces: physical, semantic, and virtual spaces, collectively referred to as a ubiquitous robotic space. We implemented a prototype robotic security application in an office environment, which confirmed that the proposed framework is an efficient tool for developing a robotic service employing IT infrastructure, particularly for integrating heterogeneous technologies and robotic platforms. 相似文献