全文获取类型
收费全文 | 4246篇 |
免费 | 225篇 |
国内免费 | 70篇 |
专业分类
电工技术 | 170篇 |
综合类 | 54篇 |
化学工业 | 836篇 |
金属工艺 | 110篇 |
机械仪表 | 152篇 |
建筑科学 | 94篇 |
矿业工程 | 19篇 |
能源动力 | 141篇 |
轻工业 | 209篇 |
水利工程 | 31篇 |
石油天然气 | 32篇 |
武器工业 | 8篇 |
无线电 | 814篇 |
一般工业技术 | 673篇 |
冶金工业 | 611篇 |
原子能技术 | 29篇 |
自动化技术 | 558篇 |
出版年
2024年 | 11篇 |
2023年 | 36篇 |
2022年 | 103篇 |
2021年 | 128篇 |
2020年 | 78篇 |
2019年 | 66篇 |
2018年 | 87篇 |
2017年 | 93篇 |
2016年 | 95篇 |
2015年 | 114篇 |
2014年 | 177篇 |
2013年 | 323篇 |
2012年 | 262篇 |
2011年 | 265篇 |
2010年 | 219篇 |
2009年 | 211篇 |
2008年 | 210篇 |
2007年 | 195篇 |
2006年 | 185篇 |
2005年 | 107篇 |
2004年 | 106篇 |
2003年 | 105篇 |
2002年 | 81篇 |
2001年 | 62篇 |
2000年 | 66篇 |
1999年 | 76篇 |
1998年 | 243篇 |
1997年 | 157篇 |
1996年 | 115篇 |
1995年 | 65篇 |
1994年 | 76篇 |
1993年 | 71篇 |
1992年 | 49篇 |
1991年 | 36篇 |
1990年 | 39篇 |
1989年 | 39篇 |
1988年 | 24篇 |
1987年 | 20篇 |
1986年 | 16篇 |
1985年 | 18篇 |
1984年 | 17篇 |
1983年 | 7篇 |
1982年 | 8篇 |
1981年 | 10篇 |
1980年 | 6篇 |
1978年 | 8篇 |
1977年 | 8篇 |
1976年 | 15篇 |
1975年 | 7篇 |
1973年 | 5篇 |
排序方式: 共有4541条查询结果,搜索用时 15 毫秒
21.
Chin-Ming Kuo Daniel P. Miranker James C. Browne 《Journal of Parallel and Distributed Computing》1991,13(4)
This paper presents the performance results of a comprehensive approach to the parallel execution of rule systems. It describes the semantics of a Concurrent Rule Execution Language, CREL, and the architecture of the system that compiles and executes CREL programs. The system has been designed to avoid run-time overhead by performing extensive compile-time analysis and by parallelizing compilation. Static dependency analysis, based on serializability, coupled with a set of optimizing transforms, partitions the program into subsets, called clusters. Clusters execute independently of each other and communicate though asynchronous message passing. At run time two additional sources of parallelism are exploited—run-time consistency checking allowing multiple rules to fire, and match-level parallelism. The CREL system is implemented on a Sequent Symmetry shared-memory computer. This paper presents the results of a factorial experiment that isolates and evaluates each source of parallelism in the CREL system and each possible combination of those methods. The results suggest that multiple-rule firing is the single most important source of parallelism in CREL programs and that the use of static dependency analysis based on serializability is instrumental to effectively exploit parallelism. 相似文献
22.
Way Kuo 《IIE Transactions》1985,17(2):132-140
Classical statistical estimation techniques have limited usage in predicting system availability when a system, e.g., a computer or telecommunications system, is highly reliable. A Bayesian solution is suggested in this paper. Gamma priors, which are rich in shapes, are assigned to the scale parameters of a gamma distributed component on-time and off-time. Estimation of the gamma priors follows engineer's past experiences for reliability modeling. Both steady-state and instantaneous availabilities are derived using Bayes Theorem. An illustration highlights the assessment and evaluation of the proposed availability measure. 相似文献
23.
PLZT ceramics with the composition of 9/62/38 (La/Zr/Ti) were fabricated from spraydried aqueous solution. Complete crystallization
of the spray-dried powder is achieved after 1 hr calcination at 650‡ C as compared to 800‡ C, 1 hr for conventional mixedoxide
method. Sintering environment plays an important role in the densification of PLZT ceramics. Densities of the atmosphere sintered
samples are much higher than those of normal sintered ones. PLZT ceramics derived from spray-dried powders have properties
comparable to those derived from sol-gel ones. The spray-dried method presents a less expensive and more effective approach
in the synthesis of PLZT ceramics. 相似文献
24.
Compact miniaturized hairpin resonators are used to design cross-coupled filters with a dual-passband response of elliptic function type. The hairpin resonators are treated as a stepped impedance resonator (SIR) in analysis. In a filter, two different hairpin resonators are used to establish proper couplings required for the two design frequencies. Two filters are fabricated and measured. The results show a good agreement with the simulation. 相似文献
25.
Solid solutions of the GdFeO3–GdInO3 system were prepared at 1550 °C by ceramic powder processing. The formulated composition was Gd(Fe1−xInx)O3 (GFI) with the indium contents at x = 0, 0.25, 0.5, 0.75, and 1.0. A stable phase of Gd(Fe1/3In2/3)O3 in our system was identified by X-ray diffraction and phase composition analysis. Multi-phase morphologies were observed for GFI bulks with x = 0.5 and 0.75. Dielectric and electrical properties of the GFI bulks were investigated. The addition of 25% In3+ in GdFeO3 had an obvious enhancement in polarization and led to an elevated resonance frequency. Dielectric properties of GFI bulks except GdInO3 were strongly dependent upon the test frequency, which corresponded to the response of polarization mechanism. GdInO3 displayed as a stable dielectric, which was frequency- and temperature-insensitive. GdInO3 was thermally activated and became leaky until above 600 °C. 相似文献
26.
Kuo‐Hsiung Wang Tzong‐Ming Wu Yeng‐Fong Shih Chien‐Ming Huang 《Polymer Engineering and Science》2008,48(9):1833-1839
The water bamboo husk is one of major agricultural wastes in Taiwan. In this study, the powder obtained from the water bamboo husk was added to poly(lactic acid) (PLA) to form novel reinforced biodegradable composites. Morphologies, mechanical properties, and heat resistance of these water bamboo powder reinforced composites were investigated. The results indicate that the char yields were increased as plant powder was incorporated to PLA. In addition, the mechanical properties were also enhanced due to the addition of powders. The increments of storage moduli of PLA were about 50–200%. Moreover, the increments of loss moduli of PLA were about 70–200%. On the other hand, the Tg of PLA was slightly decreased by the addition of powder, and this may improve the brittle characteristics of PLA. Furthermore, this type of reinforced PLA would be more environmental friendly than the artificial additive‐reinforced one. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers 相似文献
27.
28.
A closed-form physical model is reported for VLSI bipolar devices considering energy transport. Based on the model, for a base width of 810 Å, the bipolar device, biased at Vcb=2 V, has a peak electron temperature of over 700 K, which results in a 5% reduction in the collector current 相似文献
29.
C-reactive protein (CRP) is a prototypic acute phase protein in human and rabbit. Although it is structurally and functionally conserved from invertebrate to human, there are species-specific differences in patterns of expression and putative function. To further investigate the biological significance, regulation, and evolution of CRP, we isolated Xenopus CRP and subsequently derived and sequenced corresponding cDNA and the genomic clones. The structure and expression of Xenopus CRP were also compared to those of the other CRPs. Analyses of the amino acid sequence and the nucleotide sequence reveal that the mature Xenopus CRP is a 222-amino acid protein preceded by a 16-residue signal peptide. During development, Xenopus CRP is expressed, only when the liver appears, and therefore is not likely to play a role in early embryonic development. Compared to other species, Xenopus CRP is present at an intermediate low level of < 1 microgram/ml in the normal serum. Unlike human and rabbit CRP, Xenopus CRP is not induced by turpentine or heatshock treatment. The heatshock consensus sequence (Woo, P., Korenberg, J. R., and Whitehead, A. S. (1985) J. Biol. Chem. 265, 4136-4142) are not present in the Xenopus CRP gene. It is suggested that Xenopus CRP represents a transitional period in CRP evolution when host defenses switched from primitive innate immunity to a much more complex immune system. The constitutive functions of CRP gradually became less essential as the result of the development of a complex immune system. 相似文献
30.
H.C. Kuo Y.H. Chang H.H. Yao Y.A. Chang F.-I. Lai M.Y. Tsai S.C. Wang 《Photonics Technology Letters, IEEE》2005,17(3):528-530
1.27-/spl mu/m InGaAs: Sb-GaAs-GaAsP vertical-cavity surface-emitting lasers (VCSELs) were grown by metal-organic chemical vapor deposition and exhibited excellent performance and temperature stability. The threshold current changes from 1.8 to 1.1 mA and the slope efficiency falls less than /spl sim/35% as the temperature raised from room temperature to 70/spl deg/C. With a bias current of only 5 mA, the 3-dB modulation frequency response was measured to be 8.36 GHz, which is appropriate for 10-Gb/s operation. The maximal bandwidth is measured to be 10.7 GHz with modulation current efficiency factor (MCEF) of /spl sim/5.25 GHz/(mA)/sup 1/2/. These VCSELs also demonstrate high-speed modulation up to 10 Gb/s from 25/spl deg/C to 70/spl deg/C. 相似文献