全文获取类型
收费全文 | 4539篇 |
免费 | 240篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 42篇 |
综合类 | 5篇 |
化学工业 | 755篇 |
金属工艺 | 67篇 |
机械仪表 | 87篇 |
建筑科学 | 142篇 |
矿业工程 | 7篇 |
能源动力 | 102篇 |
轻工业 | 326篇 |
水利工程 | 33篇 |
石油天然气 | 9篇 |
无线电 | 458篇 |
一般工业技术 | 816篇 |
冶金工业 | 1347篇 |
原子能技术 | 32篇 |
自动化技术 | 557篇 |
出版年
2023年 | 33篇 |
2022年 | 46篇 |
2021年 | 103篇 |
2020年 | 71篇 |
2019年 | 104篇 |
2018年 | 117篇 |
2017年 | 103篇 |
2016年 | 111篇 |
2015年 | 107篇 |
2014年 | 154篇 |
2013年 | 214篇 |
2012年 | 195篇 |
2011年 | 258篇 |
2010年 | 178篇 |
2009年 | 175篇 |
2008年 | 217篇 |
2007年 | 193篇 |
2006年 | 145篇 |
2005年 | 137篇 |
2004年 | 111篇 |
2003年 | 101篇 |
2002年 | 90篇 |
2001年 | 51篇 |
2000年 | 64篇 |
1999年 | 86篇 |
1998年 | 284篇 |
1997年 | 182篇 |
1996年 | 129篇 |
1995年 | 99篇 |
1994年 | 102篇 |
1993年 | 97篇 |
1992年 | 52篇 |
1991年 | 32篇 |
1990年 | 40篇 |
1989年 | 47篇 |
1988年 | 39篇 |
1987年 | 31篇 |
1986年 | 31篇 |
1985年 | 32篇 |
1984年 | 35篇 |
1983年 | 27篇 |
1982年 | 28篇 |
1981年 | 23篇 |
1980年 | 17篇 |
1979年 | 18篇 |
1978年 | 19篇 |
1977年 | 51篇 |
1976年 | 69篇 |
1973年 | 18篇 |
1971年 | 16篇 |
排序方式: 共有4785条查询结果,搜索用时 15 毫秒
1.
2.
Benjarat Tepsongkroh Kamolwan Jangchud Anuvat Jangchud Pitchayapat Chonpracha Ryan Ardoin Witoon Prinyawiwatkul 《International Journal of Food Science & Technology》2020,55(1):46-54
Effects of mushroom type, seasoning and health benefit information (HBI) on consumers’ saltiness expectation, sensory liking, elicited emotions and purchase intent (PI) of extruded snacks were investigated. Five snacks were evaluated: straw mushroom (Volvariella volvacea) extrudates without (SME) or with seasoning (SMES), phoenix mushroom (Pleurotus pulmonarius) extrudates without (PME) or with seasoning (PMES), and the control without mushroom and seasoning. Hedonic scores and positive emotions were generally higher for seasoned mushroom-containing snacks (SMES and PMES) with 65% and 75.83% of consumers reporting willingness to purchase, respectively, after receiving HBI. Bored, interested and satisfied were identified as significant emotional predictors for PI odds. Flavour, saltiness, overall liking, bored, good and interested were critical attributes, differentiating snacks. This study demonstrated that sensory liking and PI of extruded brown rice-based snacks containing mushroom could be improved through savoury seasoning addition, which also allowed saltiness expectations to be met. 相似文献
3.
In this paper, we first re-examine the previous protocol of controlled quantum secure direct communication of Zhang et al.’s scheme, which was found insecure under two kinds of attacks, fake entangled particles attack and disentanglement attack. Then, by changing the party of the preparation of cluster states and using unitary operations, we present an improved protocol which can avoid these two kinds of attacks. Moreover, the protocol is proposed using the three-qubit partially entangled set of states. It is more efficient by only using three particles rather than four or even more to transmit one bit secret information. Given our using state is much easier to prepare for multiqubit states and our protocol needs less measurement resource, it makes this protocol more convenient from an applied point of view. 相似文献
4.
Silverberg Koerner Susan; Wallace Sara; Jacobs Lehman Stephanie; Lee Sun-A; Escalante Kristine A. 《Canadian Metallurgical Quarterly》2004,18(1):46
This study addressed two main questions: (a) Are adolescent sons and daughters exposed to sensitive maternal disclosures after divorce with similar frequency and in similar detail? and (b) Does gender act as a moderator in the association between maternal disclosures and adolescent adjustment difficulties? Forced-choice and open-ended data were collected from 194 adolescents within 2 years after their parents' divorce. Quantitative analyses revealed that although the majority of adolescents experience some level of maternal disclosure, neither frequency nor detail of maternal disclosure differed as a function of adolescent gender. Frequent and detailed maternal disclosures were associated with adolescent adjustment difficulties, primarily psychological distress. Gender did not moderate that significant association. Qualitative analysis shed light on the link between maternal disclosures and adolescent distress, suggested the importance of how disclosures are made, and revealed several gender differences in reactions to maternal disclosures. Implications of the findings are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
5.
6.
Valenzuela R.A. Landron O. Jacobs D.L. 《Vehicular Technology, IEEE Transactions on》1997,46(1):203-212
We explore techniques for the measurement of local mean signal strength at 900 MHz and 2 GHz. In particular, we characterize the impact of transmitter and receiver antenna rotation on the estimated local mean. Then, we explore the collection of high resolution data while moving along a linear trajectory and using linear averaging techniques to estimate the local mean. With this information, the best measurement techniques can be chosen depending on the required speed versus accuracy tradeoff. Finally, we use a ray tracing propagation model to evaluate different methods of calculating the local mean signal strength for indoor environments 相似文献
7.
Kuh S.S. Strozier T.A. Ryan C.R. 《Selected Areas in Communications, IEEE Journal on》1989,7(9):1462-1469
A continuous phase quadrature phase shift keyed (CPQPSK) modulation technique is presented. This method utilizes a conventional QPSK modulator and a phase trajectory converter to approximate M =4, h =1/4 continuous phase signal and allows low cost, low complexity, and high rate (>1 Gbit/s) CPM modem implementation for bandwidth efficient transmission through nonlinear satellite channels. Using a communications analysis computer program it has been found that CPQPSK has 99 percent out-of-band power of 0.8R (MSK has 99 percent out-of-band power of 1.2 R where R is defined as bit rate), continuous phase trajectories, and nearly constant envelope amplitude. Simulation of realistic hardware designs indicate that the CPQPSK will require an Eb /No of 14 dB to achieve a bit error rate (BER) of 10-6. Forward error correcting techniques using block codes with an overhead of 10 percent indicate that the Eb /No requirements can be reduced to 11.2 dB for 10-6 BER 相似文献
8.
In an experiment on the effects of different feedback conditions on motivationally relevant variables, R. Butler (see record 1988-21628-001) tested the hypothesis that the effects of feedback on intrinsic motivation would depend on whether that feedback promotes a task-involving or ego-involving orientation. She interpreted the findings as they relate to J. G. Nicholls's (see record 1984-28719-001) theory of task/ego involvement and our cognitive evaluation theory (E. L. Deci and R. M. Ryan, 1985). Although the data were very interesting, Butler failed to review a series of highly relevant studies, she misportrayed cognitive evaluation theory, and she drew conclusions that were not necessarily warranted given her experimental manipulations and data. This article provides a commentary on that research and presents a discussion of the relation between the two theories that Butler claimed to have tested. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
9.
T.Z. Kosc K.L. Marshall Anka Trajkovska-Petkoska Erin Kimball S.D. Jacobs 《Displays》2004,25(5):171-176
Polymer cholesteric liquid crystal (PCLC) flake technology is being developed as an alternative display technology for flexible, reflective particle displays. The motion of PCLC flakes suspended in a host fluid can be controlled with an electric field, creating a way to electrically control the flakes' ability to brightly reflect light that is circularly polarized. The PCLC flake/host fluid dispersion has been successfully microencapsulated both in a polymer matrix and in gelatin micro-capsules. Microencapsulation will not only expand the applications scope of the technology, but also may aid in addressing some potential problem areas that are inherent to many forms of particle display technology. A second important development in PCLC flake technology involves the manufacture of shaped flakes based on soft lithography techniques. The size and shape of a flake impact its reorientation, and uniformly shaped flakes respond in a similar manner. The unique reflective properties of PCLC flakes also provide possible applications in areas such as optics and photonics, switchable ‘smart windows’ or conformal coatings, and information displays such as ‘electronic paper.’ 相似文献
10.
Why are human observers particularly sensitive to human movement? Seven experiments examined the roles of visual experience and motor processes in human movement perception by comparing visual sensitivities to point-light displays of familiar, unusual, and impossible gaits across gait-speed and identity discrimination tasks. In both tasks, visual sensitivity to physically possible gaits was superior to visual sensitivity to physically impossible gaits, supporting perception-action coupling theories of human movement perception. Visual experience influenced walker-identity perception but not gait-speed discrimination. Thus, both motor experience and visual experience define visual sensitivity to human movement. An ecological perspective can be used to define the conditions necessary for experience-dependent sensitivity to human movement. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献