全文获取类型
收费全文 | 1582篇 |
免费 | 42篇 |
国内免费 | 14篇 |
专业分类
电工技术 | 43篇 |
综合类 | 19篇 |
化学工业 | 191篇 |
金属工艺 | 66篇 |
机械仪表 | 40篇 |
建筑科学 | 44篇 |
矿业工程 | 2篇 |
能源动力 | 36篇 |
轻工业 | 56篇 |
水利工程 | 9篇 |
石油天然气 | 6篇 |
武器工业 | 1篇 |
无线电 | 325篇 |
一般工业技术 | 306篇 |
冶金工业 | 229篇 |
原子能技术 | 5篇 |
自动化技术 | 260篇 |
出版年
2023年 | 6篇 |
2022年 | 21篇 |
2021年 | 27篇 |
2020年 | 13篇 |
2019年 | 18篇 |
2018年 | 23篇 |
2017年 | 29篇 |
2016年 | 39篇 |
2015年 | 33篇 |
2014年 | 44篇 |
2013年 | 89篇 |
2012年 | 74篇 |
2011年 | 95篇 |
2010年 | 78篇 |
2009年 | 84篇 |
2008年 | 86篇 |
2007年 | 68篇 |
2006年 | 84篇 |
2005年 | 47篇 |
2004年 | 39篇 |
2003年 | 54篇 |
2002年 | 36篇 |
2001年 | 39篇 |
2000年 | 27篇 |
1999年 | 28篇 |
1998年 | 80篇 |
1997年 | 62篇 |
1996年 | 44篇 |
1995年 | 28篇 |
1994年 | 26篇 |
1993年 | 36篇 |
1992年 | 14篇 |
1991年 | 17篇 |
1990年 | 16篇 |
1989年 | 12篇 |
1988年 | 16篇 |
1987年 | 9篇 |
1986年 | 7篇 |
1984年 | 9篇 |
1983年 | 5篇 |
1982年 | 10篇 |
1981年 | 7篇 |
1980年 | 8篇 |
1979年 | 4篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1974年 | 3篇 |
1973年 | 8篇 |
1971年 | 3篇 |
1970年 | 4篇 |
排序方式: 共有1638条查询结果,搜索用时 15 毫秒
91.
C. L. Burford R. M. Bethea J. C. Kao 《Journal of the American Oil Chemists' Society》1982,59(6):457A-461A
An economic analysis of the total cost for various dust control systems for a 500 ton/day model cottonseed oil mill has been
performed. All cost data have been adjusted to reflect May 1981 prices. Cost data are presented for the dust collection system,
cyclone(s), baghouse(s) and prime air mover(s) for each major processing area at 3 different air-to-cloth ratios. Data were
obtained for equipment and installation costs from mills using the various devices and/or complete systems wherever possible.
In cases where these data were not available, estimates were obtained from several firms that manufacture and install similar
equipment. At the recommended air-to-cloth ratio of 20:1, the initial capital cost was estimated as $707,900, the annual operating
expenses as $226,490 and the life cycle cost as $607,510. 相似文献
92.
The electric conductivities of float-zone silicon doped with arsenic for ntype and with boron for ptype have been measured before and after gamma irradiation using a four-point probe. Some new phenomena after prolonged irradiation are reported, and a brief discussion is given. 相似文献
93.
94.
95.
Remediation of PCE-contaminated aquifer by an in situ two-layer biobarrier: laboratory batch and column studies 总被引:11,自引:0,他引:11
The industrial solvent tetrachloroethylene (PCE) is among the most ubiquitous chlorinated compounds found in groundwater contamination. The objective of this study was to develop an in situ two-layer biobarrier system consisting of an organic-releasing material layer followed by an oxygen-releasing material layer. The organic-releasing material, which contained sludge cakes from a domestic wastewater treatment plant, is able to release biodegradable organics continuously. The oxygen-releasing material, which contained calcium peroxide, is able to release oxygen continuously upon contact with water. The first organic-releasing material layer was to supply organics (primary substrates) to reductively dechlorinate PCE in situ. The second oxygen-releasing material layer was to release oxygen to aerobic biodegrade or cometabolize PCE degradation byproducts from the first anaerobic layer. Batch experiments were conducted to design and identify the components of the organic and oxygen-releasing materials, and evaluate the organic substrate (presented as chemical oxygen demand (COD) equivalent) and oxygen release rates from the organic-releasing material and oxygen-releasing materials, respectively. The observed oxygen and COD release rates were approximately 0.0368 and 0.0416 mg/d/g of material, respectively. A laboratory-scale column experiment was then conducted to evaluate the feasibility of this proposed system for the bioremediation of PCE-contaminated groundwater. This system was performed using a series of continuous-flow glass columns including a soil column, an organic-releasing material column, two consecutive soil columns, and an oxygen-releasing material column, followed by two other consecutive soil columns. Anaerobic acclimated sludges were inoculated in the first four columns, and aerobic acclimated sludges were inoculated in the last three columns to provide microbial consortia for contaminant biodegradation. Simulated PCE-contaminated groundwater with a flow rate of 0.25 L/d was pumped into this system. Effluent samples from each column were analyzed for PCE and its degradation byproducts. Results show that up to 99% of PCE removal efficiency was obtained in this passive system. Thus, the biobarrier treatment scheme has the potential to be developed into an environmentally and economically acceptable remediation technology for the in situ treatment of PCE-contaminated aquifer. 相似文献
96.
We consider robustness analysis of heterogeneous and homogeneous networked systems based on integral quadratic constraints (IQCs). First, we show how the analysis decomposes into lower dimensional problems if the interconnection structure is exploited. This generally leads to a significant reduction of the computational complexity. Secondly, by considering a set of IQCs that characterizes the eigenvalues of the interconnection matrices of symmetrically networked systems, we derive a Popov-like criterion for such systems. In particular, when the nodes of the networked system are single-input–single-output linear time-invariant operators, the criterion can be illustrated using a generalized Popov plot. In such cases, the Popov criterion is also a necessary condition in the sense that if the criterion is violated then a destabilizing network with the specified eigenvalue distribution can be constructed. 相似文献
97.
Viscoelastic contact is a type of contact which includes, in addition to linear or nonlinear elastic response, time-dependent response due to relaxation or creep phenomena that govern the contact behavior. The characteristics of the time-dependent relaxation of such a viscoelastic contact are typically exponentially decaying functions, and exponentially growing functions for creep, respectively. Such contacts can be found in anthropomorphic robotic fingers, soft materials, viscoelastic skin with rigid core, and human fingers and feet. In this paper, the nature of viscoelastic contacts is investigated, and the evolution of their friction limit surfaces and of the pressure distributions at the contact interface are studied. Two cases commonly found in robotic grasping and manipulation are discussed. Based on the modeling formulation, it is found that the two important parameters of analysis and modeling for such contacts, i.e., the radius of contact area and the profile of pressure distribution, can be chosen using proposed coupling equations as the viscoelastic contact interface evolves with time. The new contribution of this paper includes a proposal of coupling equations between the two important parameters to describe the viscoelastic contact interface, and a study of the evolution of limit surfaces for viscoelastic contact interface due to temporal dependency, and the implication on grasp stability. It is found from the evolution of limit surfaces that when normal force is applied with typical viscoelastic contacts, grasp becomes more stable as time elapses. The modeling can be applied to the design of fingertips and the analysis of robotic grasping and manipulation involving viscoelastic fingers 相似文献
98.
Maxim A. Poorfard R. K. Johnson R. A. Crawley P. J. Kao J. T. Dong Z. Chennam M. Nutt T. Trager D. 《Solid-State Circuits, IEEE Journal of》2007,42(5):967-982
A low-IF fully integrated tuner for DBS satellite TV applications has been realized in 0.13-mum CMOS. A wideband ring oscillator-based frequency synthesizer having a large frequency step was used to downconvert a cluster of channels to a sliding low-IF frequency, while the second downconversion to baseband was performed in the digital domain. Eliminating the inductors and using a small-area oscillator has reduced both the parasitic magnetic and substrate coupling, allowing single-chip integration of the sensitive tuner and the noisy digital demodulator. A significant reduction in die area was achieved by using a single oscillator to cover the entire satellite TV spectrum, while a noise attenuator was cascaded with the PLL passive loop filter to reduce the equivalent VCO tuning gain. This improves PLL noise and spur performance and allows the on-chip integration of the loop filter. The digital low-IF tuner allows the use of a discrete step AGC loop that results in lower noise figure and higher linearity. Automatic signal path gain and bandwidth digital calibration was realized using replica ring oscillators. Tuner specifications include: 90 dB gain range, 10 dB noise figure at max gain, +25dBm IIP3 at min gain, 1.3deg rms integrated phase noise, <-50dBc spurs, 0.5-W power consumption from dual 1.8/3.3-V supplies, and 1.8times1.2 mm2 die area 相似文献
99.
Management by exceptions (MBE) is an effective management strategy in many domains. It suggests that managers focus on important jobs (e.g., planning and decision-making) without being involved in the tedious monitoring of exceptions (e.g., a critical item whose current status violates some regulations). Once an exception is detected, the managers are notified to respond to the exception promptly. Therefore, exception monitoring is the key to realize the idea of MBE. An exception monitoring system should detect exceptions in a timely manner for the managers. It should also control the extra loading it incurs to related information servers (e.g., database management systems) and the Intranet, which are fundamental backbones for information processing in businesses. In this paper, a multiagent paradigm Adaptive Agents for Management by Exceptions (AAMBE) is proposed for exception monitoring. The agents adapt to the environment by learning to work together to achieve timely detection of exceptions. An experiment to investigate the performance of AAMBE is conducted by simulating real-world operations of financial management in merchandising trades. Empirical and theoretical analyses show that AAMBE may detect more exceptions in a timelier manner by incurring less extra loading to the related information servers and the Intranet. 相似文献
100.
As information technologies advance and user-friendly interfaces develop, the interaction between humans and computers, information devices, and new consumer electronics is increasingly gaining attention. One example that most people can relate to is Apple’s innovation in human–computer interaction which has been used on many products such as iPod and iPhone. Siri, the intelligent personal assistant, is a typical application of machine-learning human–computer interaction.Algorithms in machine learning have been employed in many disciplines, including gesture recognition, speaker recognition, and product recommendation systems. While the existing learning algorithms compute and learn from a large quantity of data, this study proposes an improved learning to rank algorithm named MultiStageBoost. In addition to ranking data through multiple stages, the MultiStageBoost algorithm significantly improves the existing algorithms in two ways. Firstly, it classifies and filters data to small quantities and applies the Boosting algorithm to achieve faster ranking performance. Secondly, it enhances the original binary classification by using the reciprocal of fuzzily weighted membership as the ranking distance.The importance of data is revealed in their ranked positions. Usually data ranked in the front are given more attention than those ranked in the middle. For example, after ranking 10,000 pieces of data, the top 10, or at most 100, are the most important and relevant. Whether the data after the top ones are ranked precisely does not really matter. Due to this reason, this study has made improvement on the conventional methods of the pair-wise ranking approach. Not only are data classified and ranked binarily, they are also given different weights depending on whether they are concordant or discordant. Incorporating the concept of weighting into the ranking distance allows us to increase the precision of ranking. Results from experiments demonstrate that our proposed algorithm outperforms the conventional methods in three evaluation measures: P@n, MAP, and NDCG. MultiStageBoost was then applied to speech recognition. However, we do not aim to improve the technology of speech recognition, but simply hope to provide evidences that MultiStageBoost can be used in the classification and ranking in speech recognition. Experiments show that the recognition optimization procedures established by this study are able to increase the recognition rate to over 95% in the personal computing device and industrial personal computer. It is expected that in the future this voice management system will accurately and effectively identify speakers answering the voice response questionnaire and will successfully carry out the functions in the choice of answers, paying the way for the formation of a virtual customer service person. 相似文献