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91.
The aim of the present study was to investigate the effect of social networking sites (SNSs) engagement on cognitive and social skills. We investigated the use of Facebook, Twitter, and YouTube in a group of young adults and tested their working memory, attentional skills, and reported levels of social connectedness. Results showed that certain activities in Facebook (such as checking friends’ status updates) and YouTube (telling a friend to watch a video) predicted working memory test performance. The findings also indicated that Active and Passive SNS users had qualitatively different profiles of attentional control. The Active SNS users were more accurate and had fewer misses of the target stimuli in the first block of trials. They also did not discriminate their attentional resources exclusively to the target stimuli and were less likely to ignore distractor stimuli. Their engagement with SNS appeared to be exploratory and they assigned similar weight to incoming streams of information. With respect to social connectedness, participants’ self-reports were significantly related to Facebook use, but not Twitter or YouTube use, possibly as the result of greater opportunity to share personal content in the former SNS. 相似文献
92.
We have examined the 3'-terminal sequence of the "small" structural ribosomal RNA ("13S") of hamster cell mitochondria, using a procedure involving [3H]isoniazide labeling of samples subjected to sequential periodate oxidation and beta-elimination. The terminus was found to be PyUAUUAOH, which is similar, but not identical, to the corresponding terminus of eukaryotic cytoplasmic 18S rRNA. 相似文献
93.
An ontology of scientific experiments 总被引:1,自引:0,他引:1
94.
Hydrogen storage: The major technological barrier to the development of hydrogen fuel cell cars 总被引:2,自引:0,他引:2
In this paper, we review the current technology for the storage of hydrogen on board a fuel cell-propelled vehicle. Having outlined the technical specifications necessary to match the performance of hydrocarbon. fue1, we first outline the inherent difficulties with gas pressure and liquid hydrogen storage. We then outline the history of transition metal hydride storage, leading to the development of metal hydride batteries. A viable system, however, must involve lighter elements and be vacuum-tight. The first new system to get serious consideration is titanium-activated sodium alanate, followed by the lithium amide and borohydride systems that potentially overcome several of the disadvantages of alanates. Borohydrides can alternatively produce hydrogen by reaction with water in the presence of a catalyst but the product would have to be recycled via a chemical plant. Finally various possible ways of making magnesium hydride decompose and reform more readily are discussed. The alternative to lighter hydrides is the development of physisorption of molecular hydrogen on high surface area materials such as carbons, metal oxide frameworks, zeolites. Here the problem is that the surface binding energy is too low to work at anything above liquid nitrogen temperature. Recent investigations of the interaction mechanism are discussed which show that systems with stronger interactions will inevitably require a surface interaction that increases the molecular hydrogen-hydrogen distance. 相似文献
95.
J.Y. Cheng C.A. Ross H.I. Smith E.L. Thomas 《Advanced materials (Deerfield Beach, Fla.)》2006,18(19):2505-2521
One of the key challenges in nanotechnology is to control a self‐assembling system to create a specific structure. Self‐organizing block copolymers offer a rich variety of periodic nanoscale patterns, and researchers have succeeded in finding conditions that lead to very long range order of the domains. However, the array of microdomains typically still contains some uncontrolled defects and lacks global registration and orientation. Recent efforts in templated self‐assembly of block copolymers have demonstrated a promising route to control bottom‐up self‐organization processes through top‐down lithographic templates. The orientation and placement of block‐copolymer domains can be directed by topographically or chemically patterned templates. This templated self‐assembly method provides a path towards the rational design of hierarchical device structures with periodic features that cover several length scales. 相似文献
96.
Milliken Garrett W.; Ferra Gina; Kraiter Kyle S.; Ross Courtney L. 《Canadian Metallurgical Quarterly》2005,119(4):430
Sixteen sifakas (11 Propithecus verreauxi coquereli, 2 Propithecus verreauxi verreauxi form majori, and 3 Propithecus tattersalli) were videotaped as they fed on leaves in an arboreal context. The hand used to feed and the hand used to maintain postural stability was coded. For each subject, the lateral bias of the hand used to feed was opposite the hand used in postural support. Seven sifakas displayed no bias for feeding or posture-related hand use, 7 sifakas displayed significant feeding-related reach preferences for pulling branches to the mouth (5 left- and 2 right-hand preferences), and 9 sifakas exhibited significant hand preferences for postural support (2 left-, 7 right-hand preferent). Although these data do not strongly support the postural origins theory of behavioral lateralization, the modal preference pattern for sifakas that displayed significant hand preferences for posture and feeding involve a left bias for feeding and a right bias for postural support. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
97.
Love John M.; Kisker Ellen Eliason; Ross Christine; Raikes Helen; Constantine Jill; Boller Kimberly; Brooks-Gunn Jeanne; Chazan-Cohen Rachel; Tarullo Louisa Banks; Brady-Smith Christy; Fuligni Allison Sidle; Schochet Peter Z.; Paulsell Diane; Vogel Cheri 《Canadian Metallurgical Quarterly》2005,41(6):885
Early Head Start, a federal program begun in 1995 for low-income pregnant women and families with infants and toddlers, was evaluated through a randomized trial of 3,001 families in 17 programs. Interviews with primary caregivers, child assessments, and observations of parent-child interactions were completed when children were 3 years old. Caregivers were diverse in race-ethnicity, language, and other characteristics. Regression-adjusted impact analyses showed that 3-year-old program children performed better than did control children in cognitive and language development, displayed higher emotional engagement of the parent and sustained attention with play objects, and were lower in aggressive behavior. Compared with controls, Early Head Start parents were more emotionally supportive, provided more language and learning stimulation, read to their children more, and spanked less. The strongest and most numerous impacts were for programs that offered a mix of home-visiting and center-based services and that fully implemented the performance standards early. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
98.
M. Yedji G.G. Ross 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2005,230(1-4):386-390
Charge accumulation at the surface of insulators during low energy ion implantation is related to two processes: ion impinging on the sample and secondary electron emission. Samples composed of a piece of Si (having the size of the ion beam) fixed on the centre of polyethylene (PE) coupons have been implanted with 2.2 keV H2 ions to a fluence of 2 × 1016 H/cm2. ERD (Elastic Recoil Detection) depth profiles of the implanted ions are shallower with an increase of the PE coupon size. The relative critical Si/PE size to repel all the incident ions is around 1.1 × 1.1 cm2/2.5 × 2.5 cm2. The potential of the secondary electron suppressor has been varied from −500 V to +500 V. It changes the secondary electron distribution around the implanted area and, consequently, affects the accumulation of charges at the sample surface. When the potential is 0 V, a uniform ion implantation with little effect of charge accumulation for all sizes of PE coupons is obtained. A two-dimension model has been performed and gives a good explanation for the mechanism of the electric charge neutralisation. 相似文献
99.
High-level language abstraction for reconfigurable computing 总被引:1,自引:0,他引:1
Najjar W.A. Bohm W. Draper B.A. Hammes J. Rinker R. Beveridge J.R. Chawathe M. Ross C. 《Computer》2003,36(8):63-69
100.
Attila Bérces Ross M. Dickson Liangyou Fan Heiko Jacobsen David Swerhone Tom Ziegler 《Computer Physics Communications》1997,100(3):247-262
The Coupled Perturbed Kohn-Sham equations have been implemented in the Amsterdam Density Functional program package. Our implementation differs from previous ones in many ways. This program uses density fitting to calculate the Coulomb and exchange integrals. Further, all matrix elements of the Fock type matrix and its derivatives are calculated by numerical integration. The frozen core approximation is also implemented. Our implementation is approximately 10 times faster than a finite difference algorithm, and the absolute CPU times also compare favorably with other reported implementations. 相似文献