全文获取类型
收费全文 | 1027篇 |
免费 | 31篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 8篇 |
化学工业 | 123篇 |
金属工艺 | 34篇 |
机械仪表 | 43篇 |
建筑科学 | 11篇 |
矿业工程 | 17篇 |
能源动力 | 31篇 |
轻工业 | 57篇 |
水利工程 | 11篇 |
石油天然气 | 2篇 |
无线电 | 58篇 |
一般工业技术 | 178篇 |
冶金工业 | 368篇 |
原子能技术 | 2篇 |
自动化技术 | 116篇 |
出版年
2021年 | 16篇 |
2020年 | 15篇 |
2019年 | 13篇 |
2018年 | 16篇 |
2017年 | 13篇 |
2016年 | 17篇 |
2015年 | 12篇 |
2014年 | 9篇 |
2013年 | 45篇 |
2012年 | 20篇 |
2011年 | 34篇 |
2010年 | 19篇 |
2009年 | 18篇 |
2008年 | 31篇 |
2007年 | 38篇 |
2006年 | 32篇 |
2005年 | 22篇 |
2004年 | 19篇 |
2003年 | 24篇 |
2002年 | 13篇 |
2001年 | 20篇 |
2000年 | 21篇 |
1999年 | 26篇 |
1998年 | 78篇 |
1997年 | 58篇 |
1996年 | 43篇 |
1995年 | 28篇 |
1994年 | 20篇 |
1993年 | 46篇 |
1992年 | 16篇 |
1991年 | 9篇 |
1990年 | 14篇 |
1989年 | 13篇 |
1988年 | 14篇 |
1986年 | 11篇 |
1985年 | 14篇 |
1984年 | 10篇 |
1983年 | 9篇 |
1982年 | 11篇 |
1981年 | 12篇 |
1980年 | 11篇 |
1979年 | 12篇 |
1978年 | 10篇 |
1977年 | 18篇 |
1976年 | 26篇 |
1974年 | 6篇 |
1973年 | 10篇 |
1971年 | 6篇 |
1970年 | 7篇 |
1969年 | 8篇 |
排序方式: 共有1059条查询结果,搜索用时 31 毫秒
101.
Particle Swarm Optimization (PSO), in its present form, has been in existence for roughly a decade, with formative research
in related domains (such as social modelling, computer graphics, simulation and animation of natural swarms or flocks) for
some years before that; a relatively short time compared with some of the other natural computing paradigms such as artificial
neural networks and evolutionary computation. However, in that short period, PSO has gained widespread appeal amongst researchers
and has been shown to offer good performance in a variety of application domains, with potential for hybridisation and specialisation,
and demonstration of some interesting emergent behaviour. This paper aims to offer a compendious and timely review of the
field and the challenges and opportunities offered by this welcome addition to the optimization toolbox. Part I discusses
the location of PSO within the broader domain of natural computing, considers the development of the algorithm, and refinements
introduced to prevent swarm stagnation and tackle dynamic environments. Part II considers current research in hybridisation,
combinatorial problems, multicriteria and constrained optimization, and a range of indicative application areas. 相似文献
102.
Fredrik Gustavsson Matthieu Bugnet Tomas Polcar Albano Cavaleiro Staffan Jacobson 《摩擦学汇刊》2013,56(1):113-118
It has been shown many times that cosputtering low-friction coatings of molybdenum disulfide (MoS2) and tungsten disulfide (WS2) with other elements can improve the structural, mechanical, and tribological properties. To achieve the lowest friction, MoS2 or WS2 should be doped with element(s) improving the hardness and density of the coatings. On the other hand, such elements, or their compounds, should not be present in the outermost molecular layers at the sliding interface. This article suggests that there are important differences between how MoS2 and WS2 coatings respond to or react with doping elements, despite the almost identical structure and behavior of the undoped materials. Two systems have been investigated by high-resolution transmission electron microscopy (HRTEM) and scanning TEM (STEM) electron energy loss spectroscopy (EELS), W-S-C-Cr and W-S-C-Ti, and showed significant amounts of oxides, which typically formed a layer just underneath the crystalline WS2 top layer. Further, carbon was almost completely absent in the tribofilms, despite the fact that the as-deposited coatings contained as much as 40–50 at% C. An interesting observation here is that WS2 basal planes surround or embed Fe wear particles, suggesting a relatively strong adhesion or a Fe-S chemical bonding between iron/steel and WS2. The result of this is that the wear particles become pacified and remain in the contact as low-friction material. 相似文献
103.
104.
105.
106.
A new DNA diagnostic and sequencing system has been developed that uses time-of-flight resonance ionization mass spectrometry (TOF-RIMS) to provide a rapid method of analyzing stable isotope-labeled oligonucleotides in form 1 sequencing by hybridization (SBH). With form 1, the DNA is immobilized on a nylon membrane and enriched isotope-labeled individual oligonucleotide probes are free to seek out complementary DNAs during hybridization. The major advantage of this new approach is that multiple oligonucleotides can be labeled with different enriched isotopes and can all be simultaneously hybridized to the genosensor matrix. The probes can then be simultaneously detected with TOF-RIMS with high selectivity, sensitivity, and efficiency. By using isotopically enriched tin labels, up to 10 labeled oligonucleotides could be examined in a single hybridization to the DNA matrix. Greater numbers of labels are available if rare earth isotopes are employed. In the present study, matrices containing three different DNAs were prepared and simultaneously hybridized with two different probes under a variety of conditions. The results show that DNAs, immobilized on nylon surfaces, can be specifically hybridized to probes labeled with different enriched in isotopes. Discrimination between complementary and noncomplementary sites of better than 100 was obtained in multiplexed samples. This new SBH method, which employs stable isotopic labels to locate target DNAs and TOF-RIMS to detect the labels, will be a very versatile and extensive multiplexing method. 相似文献
107.
Osprey Metals Ltd. has developed a new family of lightweight, low expansion aluminium‐silicon alloys to suit electronic applications, containing between 30 and 70 wt.% aluminium. They are produced using the Osprey spray deposition process, which achieves homogeneous and isotropic properties. Their advantageous physical characteristics, combining low thermal expansion, high thermal conductivity and low density are particularly suited for packaging electronic circuitry. These CE (controlled expansion) alloys are easy to machine to tight tolerances using standard machine tools and they can be electroplated with gold, silver or nickel finishes without difficulty. This paper focuses on the measurement of mechanical (flexural strength) and thermo‐mechanical properties (CTE, thermal diffusivity and specific heat) of these alloys, carried out in collaboration with AMTT. The property measurements were consistent with those measured previously elsewhere, apart from the CTE values, which deviated significantly and were at variance with values predicted from a rule of mixtures. This discrepancy was resolved in a short follow‐up series of measurements carried out under conditions corresponding more closely to temperature equilibrium. 相似文献
108.
109.
Jacobson Joseph L.; Jacobson Sandra W.; Padgett Robert J.; Brumitt Gail A.; Billings Robin L. 《Canadian Metallurgical Quarterly》1992,28(2):297
Assesses 4-yr-old children exposed prenatally to polychlorinated biphenyls (PCBs; an environmental toxin) on 3 tasks: 2 designed to evaluate cognitive processing efficiency and 1 to evaluate sustained attention. When compared with standardized IQ tests, these tasks provided greater specificity in identifying cognitive deficits. Adapted for 4-yr-old children in the present study, these paradigms demonstrated moderate levels of test–retest reliability. Prenatal exposure to PCBs was associated with less efficient visual discrimination processing and more errors in short-term memory scanning but not with sustained attention. Although much larger quantities of these contaminants are transferred postnatally via breastfeeding than prenatally across the placenta, postnatal exposure was unrelated to cognitive performance. The data link intrauterine PCB exposure to 2 dimensions of cognitive functioning fundamental to learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
110.
M Buraczynska W Wu R Fujita K Buraczynska E Phelps S Andréasson J Bennett DG Birch GA Fishman DR Hoffman G Inana SG Jacobson MA Musarella PA Sieving A Swaroop 《Canadian Metallurgical Quarterly》1997,61(6):1287-1292
The RPGR (retinitis pigmentosa GTPase regulator) gene for RP3, the most frequent genetic subtype of X-linked retinitis pigmentosa (XLRP), has been shown to be mutated in 10%-15% of European XLRP patients. We have examined the RPGR gene for mutations in a cohort of 80 affected males from apparently unrelated XLRP families, by direct sequencing of the PCR-amplified products from the genomic DNA. Fifteen different putative disease-causing mutations were identified in 17 of the 80 families; these include four nonsense mutations, one missense mutation, six microdeletions, and four intronic-sequence substitutions resulting in splice defects. Most of the mutations were detected in the conserved N-terminal region of the RPGR protein, containing tandem repeats homologous to those present in the RCC-1 protein (a guanine nucleotide-exchange factor for Ran-GTPase). Our results indicate that mutations either in as yet uncharacterized sequences of the RPGR gene or in another gene located in its vicinity may be a more frequent cause of XLRP. The reported studies will be beneficial in establishing genotype-phenotype correlations and should lead to further investigations seeking to understand the mechanism of disease pathogenesis. 相似文献