全文获取类型
收费全文 | 843篇 |
免费 | 55篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 3篇 |
化学工业 | 243篇 |
金属工艺 | 16篇 |
机械仪表 | 21篇 |
建筑科学 | 23篇 |
矿业工程 | 2篇 |
能源动力 | 45篇 |
轻工业 | 133篇 |
水利工程 | 2篇 |
无线电 | 56篇 |
一般工业技术 | 164篇 |
冶金工业 | 60篇 |
原子能技术 | 2篇 |
自动化技术 | 129篇 |
出版年
2024年 | 7篇 |
2023年 | 16篇 |
2022年 | 22篇 |
2021年 | 30篇 |
2020年 | 32篇 |
2019年 | 33篇 |
2018年 | 28篇 |
2017年 | 36篇 |
2016年 | 46篇 |
2015年 | 26篇 |
2014年 | 56篇 |
2013年 | 92篇 |
2012年 | 59篇 |
2011年 | 60篇 |
2010年 | 54篇 |
2009年 | 40篇 |
2008年 | 28篇 |
2007年 | 36篇 |
2006年 | 28篇 |
2005年 | 15篇 |
2004年 | 15篇 |
2003年 | 24篇 |
2002年 | 14篇 |
2001年 | 5篇 |
2000年 | 11篇 |
1999年 | 13篇 |
1998年 | 10篇 |
1997年 | 7篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 8篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1970年 | 1篇 |
排序方式: 共有899条查询结果,搜索用时 24 毫秒
1.
2.
ABSTRACT: Physical aging of amorphous anhydrous fructose at temperature 5 °C and at 22 °C was studied using differential scanning calorimetry (DSC). The dynamic glass transition temperature, Tg0 for unaged samples was 16 °C and 13.3 °C for heating rate of 10 °C/min and 1 °C/min, respectively. The fictive temperature, Tf0 for unaged samples calculated by Richardson and Savill method was 12 °C, which is close to the dynamic value obtained from the lower DSC heating rate. The fictive temperature Tf of the aged fructose glasses at temperatures both below and above the transition region was fitted well by a non-exponential decay function (Williams-Watts form). Aging above the transition region (22 °C) for 18 d increased both the dynamic glass transition temperature Tg and the fictive temperature Tf . However, aging below the transition region (5 °C) for 1 d increased the dynamic glass transition temperature Tg but decreased the fictive temperature Tf . 相似文献
3.
4.
5.
Helmy Ahmed Garg Saurabh Nahata Nitin Pamu Priyatham 《Mobile Networks and Applications》2005,10(1-2):99-113
Traditional protocols for routing in ad hoc networks attempt to obtain optimal or shortest paths, and in doing so may incur significant route discovery overhead. Such approaches may be appropriate for routing long-lived transfers where the initial cost of route discovery may be amortized over the life of the connection. For short-lived connections, however, such as resource discovery and small transfers, traditional shortest path approaches may be quite inefficient. In this paper we propose a novel architecture, CARD, for resource discovery in large-scale wireless ad hoc networks. Our mechanism is suitable for resource discovery as well as routing very small data transfers or transactions in which the cost of data transfer is much smaller than the cost of route discovery. Our architecture avoids expensive mechanisms such as global flooding and complex hierarchy formation and does not require any location information. In CARD resources within the vicinity of a node, up to a limited number of hops, are discovered using a proactive scheme. For resources beyond the vicinity, each node maintains a few distant nodes called contacts. Contacts help in creating a small world in the network and provide an efficient way to query for distant resources. Using contacts, the network view (or reachability) of the nodes increases, reducing the discovery overhead and increasing the success rate. On the other hand, increasing the number of contacts also increases control overhead. We study such trade-off in depth and present mechanisms for contact selection and maintenance that attempt to increase reachability with reduced overhead. Our schemes adapt gracefully to network dynamics and mobility using soft-state periodic mechanisms to validate and recover paths to contacts. Our simulation results show that CARD is scalable and can be configured to provide desirable performance for various network sizes. Comparisons with other schemes show overhead savings reaching over 93% (vs. flooding) and 80% (vs. bordercasting or zone routing) for high query rates in large-scale networks. 相似文献
6.
Vassilis P. Panoskaltsis Katerina D. Papoulia Saurabh Bahuguna Igor Korovajchuk 《Mechanics of Time-Dependent Materials》2007,11(3-4):217-230
We propose a generalization of the Kuhn model of linear viscoelasticity. This generalization, which has four material parameters, is able to provide a near frequency independent response over a wide range of frequencies. It is useful for highly dissipative materials such as asphalt concrete. It is derived by generalizing Lubliner and Panoskaltsis’s modified Kuhn model, but we also show that it is closely related to fractional derivative models. We show that the model admits a rheological approximation, that is, an approximation by classical springs and dashpots. The model and rheological representation are compared to experimental data. 相似文献
7.
S. Sarkar P. K. Singha S. Dey M. Mohanty B. Adhikari 《Materials and Manufacturing Processes》2006,21(3):291-296
A polyester urethane was synthesized for use in a biodegradable scaffold. The polyurethane was synthesized in a two-step process: first, ester diol was synthesized from lactic acid and polyethylene glycol 400 (PEG 400), then it was polymerized with toluene diisocyanate using dibutyl tin dilaurate (DBTDL) as a catalyst to form a polyester urethane. Polyester urethane has tensile strength of 51-59 MPa and elongation at fracture of 369-439%. FTIR and XRD were used to confirm the formation and structure of the polymer. Hydrolytic degradation was studied in different alkali solutions and in saline water. In order to assess the cellular response of this material, cytotoxicity analysis was carried out against the cell line. 相似文献
8.
Inventory aggregation, also called Risk Pooling, is one of the most efficient ways to reduce the level of safety stocks thereby reducing inventory across the supply chain. Determining the best level of aggregation is a difficult problem and needs extensive study of all the possible scenarios that can affect this decision. Minimizing costs in a supply chain is no longer the sole priority of businesses. Maintaining a high level of responsiveness is also considered equally important. The conflicting nature of these two criteria makes the solution of the problem difficult. In this paper, we develop a bi-criteria nonlinear stochastic integer programming model to determine the best supply chain distribution network to meet customer demands, where minimizing costs while maintaining high levels of responsiveness is important. We develop a two-stage optimization algorithm to solve this problem. 相似文献
9.
Kundu Abhijit Adhikari Saikat Das Arnima Kanjilal Maitreyi Ray Mukherjee Moumita 《Microsystem Technologies》2021,27(2):569-584
Microsystem Technologies - Photo-sensors are integral part of different bio-medical diagnostic equipment. Each type of bio-molecules possess unique spectral fingerprint in visible wavelength region... 相似文献
10.
Rizwana Begum Syed Nabi Rupesh Tayade Adil Hussain Arjun Adhikari In-Jung Lee Gary J. Loake Byung-Wook Yun 《International journal of molecular sciences》2021,22(10)
In the last two decades, global environmental change has increased abiotic stress on plants and severely affected crops. For example, drought stress is a serious abiotic stress that rapidly and substantially alters the morphological, physiological, and molecular responses of plants. In Arabidopsis, several drought-responsive genes have been identified; however, the underlying molecular mechanism of drought tolerance in plants remains largely unclear. Here, we report that the “domain of unknown function” novel gene DUF569 (AT1G69890) positively regulates drought stress in Arabidopsis. The Arabidopsis loss-of-function mutant atduf569 showed significant sensitivity to drought stress, i.e., severe wilting at the rosette-leaf stage after water was withheld for 3 days. Importantly, the mutant plant did not recover after rewatering, unlike wild-type (WT) plants. In addition, atduf569 plants showed significantly lower abscisic acid accumulation under optimal and drought-stress conditions, as well as significantly higher electrolyte leakage when compared with WT Col-0 plants. Spectrophotometric analyses also indicated a significantly lower accumulation of polyphenols, flavonoids, carotenoids, and chlorophylls in atduf569 mutant plants. Overall, our results suggest that novel DUF569 is a positive regulator of the response to drought in Arabidopsis. 相似文献