全文获取类型
收费全文 | 3134篇 |
免费 | 84篇 |
国内免费 | 14篇 |
专业分类
电工技术 | 21篇 |
综合类 | 2篇 |
化学工业 | 132篇 |
金属工艺 | 12篇 |
机械仪表 | 7篇 |
建筑科学 | 58篇 |
能源动力 | 18篇 |
轻工业 | 57篇 |
水利工程 | 1篇 |
石油天然气 | 3篇 |
武器工业 | 1篇 |
无线电 | 245篇 |
一般工业技术 | 191篇 |
冶金工业 | 2294篇 |
原子能技术 | 4篇 |
自动化技术 | 186篇 |
出版年
2023年 | 5篇 |
2022年 | 5篇 |
2021年 | 21篇 |
2020年 | 14篇 |
2019年 | 25篇 |
2018年 | 36篇 |
2017年 | 28篇 |
2016年 | 20篇 |
2015年 | 27篇 |
2014年 | 31篇 |
2013年 | 50篇 |
2012年 | 34篇 |
2011年 | 44篇 |
2010年 | 40篇 |
2009年 | 39篇 |
2008年 | 56篇 |
2007年 | 47篇 |
2006年 | 37篇 |
2005年 | 35篇 |
2004年 | 41篇 |
2003年 | 58篇 |
2002年 | 24篇 |
2001年 | 18篇 |
2000年 | 24篇 |
1999年 | 103篇 |
1998年 | 781篇 |
1997年 | 456篇 |
1996年 | 294篇 |
1995年 | 176篇 |
1994年 | 124篇 |
1993年 | 126篇 |
1992年 | 21篇 |
1991年 | 36篇 |
1990年 | 28篇 |
1989年 | 35篇 |
1988年 | 22篇 |
1987年 | 33篇 |
1986年 | 26篇 |
1985年 | 29篇 |
1984年 | 5篇 |
1982年 | 11篇 |
1981年 | 15篇 |
1980年 | 14篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1977年 | 34篇 |
1976年 | 67篇 |
1975年 | 4篇 |
1959年 | 3篇 |
1890年 | 3篇 |
排序方式: 共有3232条查询结果,搜索用时 15 毫秒
91.
SC Shim DH Yoo JK Lee HK Koh SR Lee SH Oh SY Kim 《Canadian Metallurgical Quarterly》1998,25(12):2464-2468
Ankylosing spondylitis (AS) results in disease-specific inflammation at the site of ligamentous insertion into the bone. Atlantoaxial joint subluxation and vertical subluxation of the axis may occur as a consequence of instability resulting from the inflammatory process. Spontaneous anterior atlantoaxial subluxation is a well recognized complication in about 2% of patients with AS, and presents with or without signs of spinal cord compression. Vertical subluxation may follow anterior or posterior subluxation. It was noted in 3-8% of patients with rheumatoid arthritis, but is an exceedingly rare complication of AS. Moreover, it has never been reported that multiple cerebellar infarction and bulbar symptoms developed spontaneously due to atlanto-occipital subluxation and vertical subluxation in a patient with a long [corrected] history of AS. We describe a man with AS who developed multiple cerebellar infarction due to vertebral artery obstruction and bulbar symptoms associated with atlanto-occipital subluxation and vertical subluxation. 相似文献
92.
CW van Haselen PV Diederen J Toonstra SC van der Putte LH Rademakers JA Faber WA van Vloten 《Canadian Metallurgical Quarterly》1998,290(11):583-590
Small-cell variants of Sézary syndrome and mycosis fungoides (MF) have been described. However, in these studies the nuclear area of the small-cell variant of MF (SC-MF) as compared to histological classical MF (CL-MF) was not characterized objectively by quantitative electron microscopy. In a 14-year follow-up period, of a total of 76 patch/plaque stage MF patients seen in the Department of Dermatology of the University Hospital Utrecht, 14 (18%) had an infiltrate composed of atypical lymphocytes characterized by a distinctly smaller cell diameter and smaller, hyperchromatic, deeply indented nuclei as compared to the usual cell type of MF. The aim of the investigation was to confirm this observation objectively using quantitative electron microscopy (morphometry) and to define SC-MF as compared to CL-MF. The study was performed on the 14 patients with SC-MF, and 10 patients with clinical and histological CL-MF and 4 patients with chronic eczema. Electron micrographs of sections obtained from each biopsy were analysed by computer to produce the following data: a nuclear contour index (NCI), the mean nuclear area (MNA), the mean nuclear area of the cells above the 75th percentile (P75NA) and the percentage of cells larger than 30 microm2. The values of MNA differed significantly between patients with SC-MF and those with CL-MF (17.6 vs 23.2 microm2; P = 0.02), as did the values of P75NA (20.7 vs 27.9 microm2; P = 0.01). The NCI of the SC-MF and CL-MF patients were similar. These results are consistent with our observations that SC-MF does indeed exist. 相似文献
93.
In this investigation we consider the formation of Cooper pairs near the oxygen-deficient sites in Y-Ba-Cu-O ceramic superconductors which would give rise to an energy-dependent potential as seen by conduction charge carriers. It is shown that Cooper pairs could be formed under such conditions, resulting in a supercurrent. We use the Bogoliubov transformation technique to calculate the energy gap, the energy difference, and the transition temperature of the model superconductor using certain data obtained from previous experiments. Numerical analysis shows that the superconducting current can be explained by the presence of such oscillating Cooper pairs. 相似文献
94.
Sarala Arunagiri Yipkei Kwok Patricia J. Teller Ricardo A. Portillo Seetharami R. Seelam 《International journal of parallel programming》2014,42(1):165-197
Providing differentiated service in a consolidated storage environment is a challenging task. To address this problem, we introduce FAIRIO, a cycle-based I/O scheduling algorithm that provides differentiated service to workloads concurrently accessing a consolidated RAID storage system. FAIRIO enforces proportional sharing of I/O service through fair scheduling of disk time. During each cycle of the algorithm, I/O requests are scheduled according to workload weights and disk-time utilization history. Experiments, which were driven by the I/O request streams of real and synthetic I/O benchmarks and run on a modified version of DiskSim, provide evidence of FAIRIO’s effectiveness and demonstrate that fair scheduling of disk time is key to achieving differentiated service in a RAID storage system. In particular, the experimental results show that, for a broad range of workload request types, sizes, and access characteristics, the algorithm provides differentiated storage throughput that is within 10% of being perfectly proportional to workload weights; and, it achieves this with little or no degradation of aggregate throughput. The core design concepts of FAIRIO, including service-time allocation and history-driven compensation, potentially can be used to design I/O scheduling algorithms that provide workloads with differentiated service in storage systems comprised of RAIDs, multiple RAIDs, SANs, and hypervisors for Clouds. 相似文献
95.
Alan Y. Kwok 《Polymer》2004,45(12):4017-4027
Poly(2-hydroxyethyl methacrylate) networks were synthesized in aqueous solutions of propylene glycol, ethylene glycol, ethylene glycol monomethyl ether, or ethylene glycol dimethyl ether and the influences of solvent on phase separation during the polymerization process studied. Results from conversion-phase diagrams, turbidity measurements, swelling studies, and viscosity measurements show that the phase separation process is dependent upon the solubility parameter of the organic solvent, the instantaneous monomer concentration at each stage of the gel formation process, and the crosslinker content of the reaction mixture. 相似文献
96.
Zirconia and yttria films were sputter deposited onto unheated fused silica substrates using a metal target and rare gas-oxygen discharges. Double-beam spectrophotometry was used to measure the transmission and reflection as a function of incident photon energy, E , from which the absorption coefficient, α( E ), was calculated. An indirect interband transition at E i = 4.70 eV and two direct interband transitions at E g1 = 5.17 eV and E g2 = 5.93 eV occur in monoclinic zirconia. Two direct interband transitions at E g1 = 5.07 eV and E g2 = 5.73 eV occur in cubic yttria. The absorption edge structure is modified when unusual phases, such as tetragonal zirconia, and zirconia and yttria with no longrange crystallographic order, are present. 相似文献
97.
Dongyu Zhao Fan Fan Vladimir G. Chigrinov Hoi Sing Kwok Ben Zhong Tang 《Journal of the Society for Information Display》2015,23(5):218-222
Nowadays, liquid crystal displays (LCDs) with light‐emission are considered as energy‐efficient devices and are promising alternatives to conventional LCDs. To realize such possibility, strong fluorescent materials with a dichroic properties are required. Aggregate‐induced emission (AIE) is an unusual photophysical phenomenon shown by some luminogenic materials that will be highly emissive in their aggregate state. In this work, we studied the AIE effect of a luminescent liquid crystalline molecule TPE‐PPE in our LC system as a luminophore dopant. The result showed the excellent AIE effect that higher concentration of luminogen in the nematic LC host induced stronger luminescent intensity. Through exposure of a photoisomeriable alignment material sulfonic‐dye‐1, the photopatterning of a light‐emitting LC device was achieved with the use of the TPE‐PPE/nematic LC mixture. 相似文献
98.
Abhishek K. Srivastava Vladimir G. Chigrinov Hoi Sing Kwok 《Journal of the Society for Information Display》2015,23(6):253-272
The ferroelectric liquid crystals, because of their fast electro‐optical response, are one of the most important classes of liquid crystals. Here, in this review, we have summarized the different electro‐optical modes for ferroelectric liquid crystals. Clark–Lagerwall effect (surface stabilized ferroelectric liquid crystal), deformed helix ferroelectric (DHF) effect, electrically suppressed helix (ESH) mode, DHF orientational Kerr effect, and ESH diffraction modes have been discussed. All of the crucial features, that is, optics, electro‐optics, dynamics, and their dependence on material parameters, operational regime, and applications, have been reviewed. 相似文献
99.
Ultra wideband (UWB) systems are considered as the key wireless infrastructure platforms for efficient short-range communications.
In particular, the UWB based mobile computing systems are envisioned to be attractive solutions to various ad hoc networking
applications. However, due to UWB’s unique physical characteristics, the traditional resource management schemes for ad hoc
networks cannot be applied to UWB based systems directly. In this paper, we consider the bandwidth scheduling problem in a
UWB based hierarchical wireless ad hoc network, which is typically used in an enterprise-scale mobile computing environment.
Based on the mathematical analysis and the computer simulations, it is demonstrated that our proposed scheduling scheme exhibits
close-to-optimal performance governed by the proportional fairness (PF) constraint. Moreover, a novel self-organized clustering
method is designed to improve the system throughput while meeting the PF constraint. Simulation results suggest that the proposed
clustering method is effective under various system configurations.
相似文献
Yu-Kwong KwokEmail: |
100.
Building Sparse Multiple-Kernel SVM Classifiers 总被引:1,自引:0,他引:1
The support vector machines (SVMs) have been very successful in many machine learning problems. However, they can be slow during testing because of the possibly large number of support vectors obtained. Recently, Wu (2005) proposed a sparse formulation that restricts the SVM to use a small number of expansion vectors. In this paper, we further extend this idea by integrating with techniques from multiple-kernel learning (MKL). The kernel function in this sparse SVM formulation no longer needs to be fixed but can be automatically learned as a linear combination of kernels. Two formulations of such sparse multiple-kernel classifiers are proposed. The first one is based on a convex combination of the given base kernels, while the second one uses a convex combination of the so-called ldquoequivalentrdquo kernels. Empirically, the second formulation is particularly competitive. Experiments on a large number of toy and real-world data sets show that the resultant classifier is compact and accurate, and can also be easily trained by simply alternating linear program and standard SVM solver. 相似文献