全文获取类型
收费全文 | 10175篇 |
免费 | 923篇 |
国内免费 | 30篇 |
专业分类
电工技术 | 119篇 |
综合类 | 13篇 |
化学工业 | 2844篇 |
金属工艺 | 350篇 |
机械仪表 | 523篇 |
建筑科学 | 233篇 |
矿业工程 | 9篇 |
能源动力 | 451篇 |
轻工业 | 970篇 |
水利工程 | 40篇 |
石油天然气 | 18篇 |
武器工业 | 1篇 |
无线电 | 1539篇 |
一般工业技术 | 2190篇 |
冶金工业 | 477篇 |
原子能技术 | 70篇 |
自动化技术 | 1281篇 |
出版年
2024年 | 16篇 |
2023年 | 127篇 |
2022年 | 214篇 |
2021年 | 354篇 |
2020年 | 274篇 |
2019年 | 320篇 |
2018年 | 424篇 |
2017年 | 416篇 |
2016年 | 484篇 |
2015年 | 375篇 |
2014年 | 531篇 |
2013年 | 701篇 |
2012年 | 763篇 |
2011年 | 837篇 |
2010年 | 645篇 |
2009年 | 640篇 |
2008年 | 577篇 |
2007年 | 430篇 |
2006年 | 372篇 |
2005年 | 316篇 |
2004年 | 269篇 |
2003年 | 295篇 |
2002年 | 245篇 |
2001年 | 176篇 |
2000年 | 169篇 |
1999年 | 165篇 |
1998年 | 187篇 |
1997年 | 122篇 |
1996年 | 109篇 |
1995年 | 72篇 |
1994年 | 68篇 |
1993年 | 41篇 |
1992年 | 59篇 |
1991年 | 42篇 |
1990年 | 40篇 |
1989年 | 37篇 |
1988年 | 21篇 |
1987年 | 26篇 |
1986年 | 19篇 |
1985年 | 20篇 |
1984年 | 23篇 |
1983年 | 18篇 |
1982年 | 5篇 |
1981年 | 11篇 |
1980年 | 9篇 |
1979年 | 6篇 |
1978年 | 5篇 |
1977年 | 15篇 |
1976年 | 17篇 |
1975年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
Verifiably encrypted signature schemes can convince a verifier that a given ciphertext is an encryption of an ordinary signature on a given message and the ordinary signature can be recovered by the third party, called adjudicator. In 2010, Rückert et al. proposed a general construction for the verifiably encrypted signatures, and then, they also showed that there exist the lattice-based verifiably encrypted signature schemes. Their constructions are very insightful, but their schemes need an extra adjudication setup phase and Merkle trees, so they have large parameters and keys, that is, they are inefficient. Also, their schemes provide only the limited signature capacity because the signing keys should be reissued after generating \(k\) th verifiably encrypted signatures. To overcome the weaknesses of Rückert et al.’s scheme, we construct a verifiably encrypted signature scheme based on the hard lattice problems. Our scheme provides the full functionality, i.e., the signatures can be generated without any limitations and does not need any extra adjudication setup phases. Moreover, the size of the secret keys in our scheme is constant. Our scheme provides unforgeability, opacity, extractability, and abuse-freeness in the random oracle model. 相似文献
53.
Thomas F. Derosa Benjamin J. Kaufman Rodney L.-D. Sung Joseph M. Russo 《应用聚合物科学杂志》1994,51(7):1339-1346
Perfluorobutyl-1,1,2-tri-H-1-hexene and perfluoroalkyl methacrylate have been solubilized in lubricating oil by single-step free radically grafting onto poly(ethylene-co-propylene). Perfluoroalkyl-1,1,2,2-tetra-H-ethanol and perfluoropolyether carboxylic acid were solubilized by condensing with poly[(ethylene-co-propylene)-g-glycidyl methacrylate], generating the corresponding perfluoroalkyl ether or ester, respectively. Solubilization of 1,1,2,2-tetra-H-ethanol was also achieved by condensing with poly[(ethylene-co-propylene)-g-2-isocyanoethyl methacrylate] to the corresponding perfluoroalkyl urethane. Scar diameter reductions ranged from 9.4 to 58% using perfluoro-modified graft copolymers as determined using the Four Ball Wear Test, although optimum reductions were obtained using perfluoroalkyl urethane-modified graft copolymers. Moreover, a semiquantitative correlation of scar reductions and thermal instability was determined. Sequence VI engine testing of perfluoroalkyl urethane graft copolymers containing pendant perfluoroalkyl chain lengths of 8.2 and 7.2 had an Equivalent Fuel Economy Index of 4.33 and 4.27, respectively. © 1994 John Wiley & Sons, Inc. 相似文献
54.
Male and female weanling rats that were born to dams fed a diet low in linolenic acid received diets of 15% lipids by weight
containing 45% elaidic acid (as trielaidin) and 8.5% or 0.1% linolenic acid for 10 weeks. Four other groups, in which palmitic
or oleic acid replaced elaidic acid in the diet, served as controls. The fatty acid profiles of several lipid classes were
determined in adipose tissue, adrenals, testes, heart and brain. Elaidic acid was incorporated into tissue lipids in varying
degrees, depending on the organ and on the lipid class. Feeding elaidic acid induced no changes in the polyunsaturated fatty
acid (PUFA) profiles of testes lipids but resulted in definite modifications of the PUFA patterns of heart phosphatidylcholine
(PC) and phosphatidylethanolamine (PE). In linolenic acid-deprived rats, arachidonic acid was decreased in PC and linoleic
acid was increased in both PC and PE; 22∶5n−6 was strongly depressed in both PC and PE. In linolenic acid-fed rats, 22∶6n−3
was decreased in PC and PE. These changes, on the whole, were more evident in females, and some also were observed in adrenal
cholesteryl esters but only slightly in brain phospholipids. the apparent inhibition of the biosynthesis of PUFA induced by
dietary elaidic acid appeared to be complex and of greater intensity in the n−6 fatty acid series than in their n−3 homologues. 相似文献
55.
The temperature dependence of permeability through highly syndiotactic poly(2-hydroxyethyl methacrylate) [P(HEMA)] membrane is reported for highly polar organic solutes such as ureas, methyl substituted ureas and amides, and for NaCl and Na2SO4. The membranes used were equilibrated in distilled water at each temperature before measurements. From the linear correlationship between the excess heat capacities, ?Cpo(excess) in aqueous solution at infinite dilution and the permeability parameter PM1/3, it is found that the water structure perturbing capability of the polar organic solutes is a controlling factor in the permeation mechanism at relatively low temperature, where P(HEMA) membrane has higher water content and more structured water. In addition, it is found that the poor separation for urea of cellulose acetate membrane in the reverse osmosis practice is due to the higher water structure-breaking capability of urea. 相似文献
56.
Yoon -Suk Choi Sung -Joon Kim Ik -Min Park Kwang -Woo Kwon In -Suk Yoo 《Metals and Materials International》1997,3(2):118-124
Boron distribution in a low-alloy steel (15B26:0.25C-0.29Cr-0.03Ti-0.028Al-0.0016B) has been characterized employing Fission
Track Etching (FTE) method. The characteristics of boron distribution with variation of cooling rate after austenitization
and through case-hardened depth after carburization were analyzed. Hardenability of 15B26 steel was also evaluated through
Jominy-end-quench test and the results are as follows: It was observed that, in austenitized 15B26 steel, boron was distributed
uniformly over the whole area of specimen with a little segregation along the austenite grain boundaries at higher cooling
rates and boron precipitates were formed in the intergranular as well as transgranular regions at lower cooling rates. Jominy
equivalents (HRC 35) of 15B26 steel were fairly increased between the Jominy temperatures of 820°C and 850°C, which might
result from the increase of the amount of soluble boron in austenite due to the dissolution of borocarbides between 820°C
and 850°C. In carburized 15B26 steel, the different through thickness features of boron distribution from the carburized surface
were found; coarse nodular boron precipitates up to the depth of 150 μm; uniform distribution of dissolved boron between 150~650
μm; and segregation of boron atoms along grain boundaries in the regions deeper than 650 μm. 相似文献
57.
Shi Hyoung Ryu Hae Sung Lee Chong Nam Chu 《International Journal of Machine Tools and Manufacture》2003,43(14):2177
In this research, an effective method for the form error prediction in side wall machining with a flat end mill is suggested. The form error is predicted directly from the tool deflection without surface generation by cutting edge locus with time simulation. The developed model can predict the surface form error accurately about 300 times faster than the previous method. Cutting forces and tool deflection are calculated considering tool geometry, tool setting error and machine tool stiffness. The characteristics and the difference of generated surface shape in up milling and down milling are discussed. The usefulness of the presented method is verified from a set of experiments under various cutting conditions generally used in die and mold manufacturing. This study contributes to real time surface shape estimation and cutting process planning for the improvement of form accuracy. 相似文献
58.
59.
Dae Kyung Kim Ji Yeon Hyun Sung Chul Kim Han Sung Kim Sei Young Lee 《Microfluidics and nanofluidics》2016,20(5):75
Micro-/nanoparticle-based systems are regarded as one of the possible candidates due to the engineerability and multifunctionality to maximize the accumulation of the nano-/microparticle-based drug delivery system on the target. Recent advances in nanotechnology enable the fabrication of diverse particle shapes from simple spherical particles to more complex shapes. The particle dynamics in blood flow and endocytosis characteristics of non-spherical particles change as the non-sphericity effect increases. We used a numerical approach to investigate the particle dynamics in linear shear flow near a wall. We examined the dynamics of slender cylindrical particles with aspect ratio γ = 5.0 in terms of particle trajectory, velocity, and force variation for different Stokes numbers over time. We identified the rotating inertia of particle near a wall as the source of inertial migration toward the wall. The drift velocity of slender cylindrical particles is comparable to that of discoidal particles. We discuss the possibilities and limitations of using slender cylindrical particles as a drug delivery system. 相似文献
60.
João Tavares Jorge Barbosa Ismael Cardoso Cristiano Costa Adenauer Yamin Rodrigo Real 《Universal Access in the Information Society》2016,15(4):589-607
This article proposes Hefestos, an intelligent system applied to ubiquitous accessibility. This model uses ubiquitous computing concepts to manage accessibility resources for people with disabilities. Among the concepts employed, context awareness, user profiles and trails management can be highlighted. The paper proposes an ontology for accessibility and delineates scenarios of its application in everyday life of people with disabilities. Moreover, the implementation of a smart wheelchair prototype and its application in a practical experiment is described. Ten users with a range of disability degrees tried the system and filled out a survey based on the technology acceptance model. This experiment demonstrated the main functionalities and the acceptance of the system. The results showed 96 % of acceptance regarding perceived easy of use and 98 % in perceived usefulness. These results were encouraging and show the potential for implementing Hefestos in real life situations. 相似文献