全文获取类型
收费全文 | 5306篇 |
免费 | 200篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 28篇 |
化学工业 | 561篇 |
金属工艺 | 40篇 |
机械仪表 | 66篇 |
建筑科学 | 90篇 |
矿业工程 | 8篇 |
能源动力 | 89篇 |
轻工业 | 264篇 |
水利工程 | 29篇 |
石油天然气 | 7篇 |
无线电 | 295篇 |
一般工业技术 | 609篇 |
冶金工业 | 3012篇 |
原子能技术 | 17篇 |
自动化技术 | 398篇 |
出版年
2023年 | 33篇 |
2022年 | 53篇 |
2021年 | 86篇 |
2020年 | 62篇 |
2019年 | 92篇 |
2018年 | 101篇 |
2017年 | 77篇 |
2016年 | 91篇 |
2015年 | 71篇 |
2014年 | 109篇 |
2013年 | 162篇 |
2012年 | 152篇 |
2011年 | 210篇 |
2010年 | 140篇 |
2009年 | 133篇 |
2008年 | 169篇 |
2007年 | 150篇 |
2006年 | 116篇 |
2005年 | 94篇 |
2004年 | 73篇 |
2003年 | 68篇 |
2002年 | 60篇 |
2001年 | 26篇 |
2000年 | 36篇 |
1999年 | 116篇 |
1998年 | 888篇 |
1997年 | 470篇 |
1996年 | 324篇 |
1995年 | 183篇 |
1994年 | 165篇 |
1993年 | 174篇 |
1992年 | 45篇 |
1991年 | 44篇 |
1990年 | 44篇 |
1989年 | 50篇 |
1988年 | 42篇 |
1987年 | 38篇 |
1986年 | 30篇 |
1985年 | 29篇 |
1984年 | 25篇 |
1983年 | 20篇 |
1982年 | 27篇 |
1981年 | 21篇 |
1980年 | 27篇 |
1979年 | 17篇 |
1978年 | 16篇 |
1977年 | 85篇 |
1976年 | 191篇 |
1975年 | 11篇 |
1971年 | 13篇 |
排序方式: 共有5513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.
5.
Phospholamban (PLN) was expressed in Escherichia coli as a protein fusion with glutathione S-transferase (GST). GST-PLN was mostly present in the insoluble protein fraction and accounted for approximately 50% of total insoluble protein. Attempts to suppress inclusion body formation or to use GST as an affinity-purification tag failed. A successful purification method is based on preparative SDS/PAGE and electrodialysis. From 1 g cells we typically purified 13.5 mg fusion protein with a PLN content of 2.8 mg. We genetically inserted an enterokinase (EK) protease site just in front of the PLN sequence and demonstrated the proteolytical liberation of PLN from the carrier protein. The approach described represents a substantial advancement in PLN expression and purification. 相似文献
6.
BACKGROUND: The effect of topical corticosteroids after excimer laser photorefractive keratectomy (PRK) remains a matter of some controversy. Refractive effects may be different according to the amount of myopia and timing of instillation. METHODS: Two groups of patients were studied: Study A consisted of 215 eyes (128 patients) with PRK (mean baseline myopia, -6.53 +/- 2.22 D) that received no corticosteroids (No Corticosteroid Group) unless significant regression or corneal haze appeared (Delayed Corticosteroid Group), and in Study B, we randomly assigned eyes to the Initial Corticosteroid Group (mean baseline myopia, -6.39 +/- 1.84 D) or the No/delayed Corticosteroid Group (mean baseline myopia -5.78 +/- 2.02 D). Clinical results after PRK for low-to-moderate and high myopia were compared. RESULTS: In the first group, 70.9% (73 eyes) of moderately myopic eyes (mean, -4.56 +/- 1.10 D) belonged to the No Corticosteroid Group that had a mean refraction of -5.39 +/- 1.77 D. Delayed Corticosteroid Group eyes were more myopic (mean, -7.52 +/- 2.10 D), and showed more severe haze than those in the No Corticosteroid Group. In study B, only in high myopes with more than -6.00 D (mean, -7.76 +/- 1.15 D) did refraction and corneal haze outcomes show significant difference between the Initial Corticosteroid Group and the No/delayed Corticosteroid Group. CONCLUSIONS: The effects of topical corticosteroids after PRK were less in moderate myopes compared to high myopes. Delayed instillation of corticosteroids did not reverse the regression or haze whereas initial instillation showed a beneficial effect on high myopes but not on moderate myopes. 相似文献
7.
9.
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
10.
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