全文获取类型
收费全文 | 1177篇 |
免费 | 77篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 12篇 |
综合类 | 1篇 |
化学工业 | 617篇 |
金属工艺 | 8篇 |
机械仪表 | 14篇 |
建筑科学 | 33篇 |
矿业工程 | 5篇 |
能源动力 | 33篇 |
轻工业 | 80篇 |
水利工程 | 7篇 |
石油天然气 | 1篇 |
无线电 | 72篇 |
一般工业技术 | 113篇 |
冶金工业 | 177篇 |
自动化技术 | 82篇 |
出版年
2023年 | 7篇 |
2022年 | 26篇 |
2021年 | 52篇 |
2020年 | 34篇 |
2019年 | 101篇 |
2018年 | 115篇 |
2017年 | 45篇 |
2016年 | 40篇 |
2015年 | 12篇 |
2014年 | 98篇 |
2013年 | 43篇 |
2012年 | 39篇 |
2011年 | 64篇 |
2010年 | 42篇 |
2009年 | 29篇 |
2008年 | 41篇 |
2007年 | 38篇 |
2006年 | 48篇 |
2005年 | 31篇 |
2004年 | 27篇 |
2003年 | 16篇 |
2002年 | 18篇 |
2001年 | 12篇 |
2000年 | 20篇 |
1999年 | 12篇 |
1998年 | 22篇 |
1997年 | 16篇 |
1996年 | 20篇 |
1995年 | 14篇 |
1994年 | 12篇 |
1993年 | 12篇 |
1992年 | 8篇 |
1991年 | 9篇 |
1990年 | 6篇 |
1989年 | 10篇 |
1987年 | 9篇 |
1986年 | 10篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 8篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1975年 | 7篇 |
1974年 | 4篇 |
1973年 | 4篇 |
1971年 | 5篇 |
1970年 | 5篇 |
排序方式: 共有1255条查询结果,搜索用时 15 毫秒
101.
Patrick N Okoh Roman P Kubiczek Placid C Njoku Grace T Iyeghe 《Journal of the science of food and agriculture》1989,49(3):271-279
Grains of two sorghum (Sorghum vulgare L) varieties were germinated at room temperature for 2, 4 and 6 days. Germination resulted in an increase in protein content due to dry matter loss; this rose with increasing time of germination. The absolute amount of tannin was unchanged until the fourth day of germination but decreased markedly by the sixth day. Fractionation of the grain protein of one variety showed that there was a large increase in the albumin-globulin fraction (rich in lysine) and a decrease in the kafirin and cross-linked kafirin fraction (low in lysine) as a result of germination. Although these changes resulted in a more than 30% increase in lysine content on the fourth and sixth days of germination, a substantial loss in dry matter occurred when germination was continued up to 6 days. When 14-day-old Hubbard chicks were fed a diet containing about 59% malted sorghum supplemented with lysine, they showed better (P < 0.05) weight gain and efficiency of feed conversion than those on malted sorghum without lysine supplementation. However, malting reduced the amount of lysine needed to supplement the diet from 0.25% for unmalted sorghum to 0.18% for malted sorghum. 相似文献
102.
103.
Ricardo Acosta Ortiz María Lydia Berlanga Duarte Amy Grace Savage Gómez Marco Sangermano Aída E García Valdez 《Polymer International》2010,59(5):680-685
Shrinkage that takes place during polymerizations induces internal stress in polymeric materials generating a series of problems like poor adhesion to substrates and delamination in coatings or microcracks and microvoids in composites. Some additives like spiro orthocarbonates can reduce or eliminate this shrinkage. This paper deals with the synthesis of novel diol spiro orthocarbonates (DIOL SOCs) and their effect as anti‐shrinkage additives in the photopolymerization of the monomer 3,4‐epoxycyclohexyl‐3′, 4′‐epoxycyclohexanecarboxylate. It was found that increasing the concentration of the DIOL SOCs resulted in higher conversion of the monomer due to the presence of hydroxyl groups. The viscoelastic properties of the polymer products were also measured. It was observed that at 5 mol% of the mixture of DIOL SOCs there was an increase in the storage modulus due to the crosslinking produced by the bifunctional SOCs. However, at higher concentrations, a decrease in the storage modulus was observed. The level of shrinkage using the DIOL SOCs at 20 mol% was reduced by 45% when compared to the case without any additive. DIOL SOCs can be easily prepared by reacting glycerol with tetraethylorthocarbonate. These additives reduced significantly the level of shrinkage of the polyether derived from the diepoxycyclohexane monomer. Copyright © 2010 Society of Chemical Industry 相似文献
104.
This paper presents a prototype analog-to-digital converter (ADC) that uses a calibration algorithm to adaptively overcome constant closed-loop gain errors, closed-loop gain variation, and slew-rate limiting. The prototype consists of an input sample-and-hold amplifier (SHA) that can serve as a calibration queue, a 12-bit 80-MSample/s pipelined ADC, a digital-to-analog converter (DAC) for calibration, and an embedded custom microprocessor, which carries out the calibration algorithm. The calibration is bootstrapped in the sense that the DAC is used to calibrate the ADC, and the ADC is used to calibrate the DAC. With foreground calibration, test results show that the peak differential nonlinearity (DNL) is -0.09 least significant bits (LSB), and the peak integral nonlinearity (INL) is -0.24LSB. Also, the maximum signal-to-noise-and-distortion ratio (SNDR) and spurious-free dynamic range (SFDR) are 71.0 and 79.6dB with a 40-MHz sinusoidal input, respectively. The prototype occupies 22.6 mm/sup 2/ in a 0.25-/spl mu/m CMOS technology and dissipates 755 mW from a 2.5-V supply. 相似文献
105.
The ketogenic diet, a treatment for intractable epilepsy, is rarely initiated because it requires strict compliance with a diet that is perceived to be unpalatable. In a case study of a 15-year-old girl with uncontrolled epilepsy, we used a stimulus-choice procedure to assess relative preferences of 33 foods from the diet and to develop two treatments based on Premack's principle. The results of a multielement analysis showed that both treatments increased dietary compliance. Compliance was maintained with generalization of treatment across settings, and was associated with a 40% reduction in seizures. 相似文献
106.
Round-robin scheduling is commonly employed in time-division multiple-access based medium access control protocols, to provide users with equitable access to a shared channel. The letter presents an analytical model to evaluate the mean end-to-end delay of packets traversing a geostationary satellite link with a round-robin free assignment scheduling strategy and Poisson source traffic. It is shown that the model can accurately predict the end-to-end delay performance of a round-robin scheduling satellite system. 相似文献
107.
On the design and management of heterogeneous networks: a predictability-based perspective 总被引:1,自引:0,他引:1
While great strides have been made in the design and deployment of commercial networks over the past two decades, relatively little progress has been made toward the realization of large-scale tactical military networks. The primary reasons for this disparity include the fact that commercial telecommunication networks are predominantly wired, relatively stable infrastructures, whereas tactical networks consist largely of wireless mobile nodes with unique operating characteristics in hostile environments. Wireless networks must cope with dynamic link conditions not present in wired infrastructures, which place a heavy burden on quality of service management solutions. Managing QoS in the face of constantly changing operating conditions demands dynamic management approaches that span multiple layers in the protocol stack. Such cross-layer design approaches have recently received attention in the context of cellular and mobile ad hoc networks. However, there are still a wide range of opinions and definitions about what exactly CLD entails, and there is no fundamental guidance concerning how to apply CLD techniques in various environments. In this article we introduce the notion of network predictability and describe its relationship to achievable QoS. This relationship is used to propose a framework for CLD that can be used to guide development efforts and direct investment decisions for future military networks. The framework also contains the notion of a crosslayer coherence length, which determines the protocol layers across which the highest degree of coupling, or correlation, should be present in order to realize the greatest possible gains in achievable QoS. 相似文献
108.
Entitativity perception refers to the perception of a collection of individuals as a group. The authors propose 2 perceptual-inferential bases of entitativity perception. First, perceivers would expect a collection of individuals with similar physical traits to possess common psychological traits. Second, perceivers watching a group of individuals engage in concerted behavior would infer that these individuals have common goals. Thus, both similarity in physical traits (e.g., same skin color) and concerted collective behavior (e.g., same movement) would evoke perception of group entitativity. Results from 5 experiments show that same group movement invariably leads to common goal inferences, increased perceived cohesiveness, and increased perceived entitativity. Moreover, same skin color evokes inferences of group traits and increases perceived homogeneity and perceived entitativity but only when skin color is diagnostic of group membership. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
109.
PS Jensen KW Grace R Attariwala JE Colgate MR Glucksberg 《Canadian Metallurgical Quarterly》1997,235(11):696-701
BACKGROUND: Experimental protocol in our laboratory routinely requires the precise placement of instruments at, or near, the retina. Although manipulators for placing an instrument within the eye presently exist, none of the designs were satisfactory due to limitations on size, accuracy and operability. To overcome these limitations, we have developed a novel six degree of freedom manipulator designed specifically for retinal microsurgery. METHODS: The manipulator is parallel in structure and provides submicrometer positioning of an instrument within the constrained environment of the eye. The position of an instrument attached to the manipulator is commanded by the operator using a hand-held trackball. A computer controller interprets the trackball input and moves the manipulator in an intuitive manner according to mathematically constrained modes of operation. RESULTS: Over 50 retinal vessels in the live, anesthetized cat have been successfully cannulated for pressure measurement and drug injection using the described manipulator and micropuncture techniques. The targeted vessels ranged in internal diameter from 20 to 130 microns. CONCLUSION: This device has applications in microsurgery where tremor and fatigue limit the performance of an unaided hand and where mechanically constrained manipulators are inappropriate due to size and operative constraints. 相似文献
110.
INTEGRATED SHOP FLOOR CONTROL USING AUTONOMOUS AGENTS 总被引:26,自引:0,他引:26
In this paper, we present a generic framework for controlling the work flow in computer controlled manufacturing systems. Based on a market-like model and a combination of objective and price mechanism, the framework allows heterogeneous job objectives, admits job priorities, recognizes multiple resources types, and allows multiple step negotiation between parts and resources. The framework is designed to accommodate frequent changes in the environment such as machine failures, tool shortages, and process requirement variations. An object-oriented simulation system is built to demonstrate the flexibility and effectiveness of die proposed framework. The results show that the proposed framework provides a foundation for highly adaptive, real time shop floor control. 相似文献