全文获取类型
收费全文 | 2833篇 |
免费 | 190篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 43篇 |
综合类 | 2篇 |
化学工业 | 737篇 |
金属工艺 | 60篇 |
机械仪表 | 38篇 |
建筑科学 | 96篇 |
矿业工程 | 8篇 |
能源动力 | 103篇 |
轻工业 | 449篇 |
水利工程 | 18篇 |
石油天然气 | 3篇 |
无线电 | 148篇 |
一般工业技术 | 448篇 |
冶金工业 | 414篇 |
原子能技术 | 14篇 |
自动化技术 | 443篇 |
出版年
2024年 | 11篇 |
2023年 | 33篇 |
2022年 | 61篇 |
2021年 | 98篇 |
2020年 | 67篇 |
2019年 | 90篇 |
2018年 | 110篇 |
2017年 | 104篇 |
2016年 | 117篇 |
2015年 | 85篇 |
2014年 | 126篇 |
2013年 | 193篇 |
2012年 | 171篇 |
2011年 | 163篇 |
2010年 | 151篇 |
2009年 | 151篇 |
2008年 | 156篇 |
2007年 | 130篇 |
2006年 | 105篇 |
2005年 | 75篇 |
2004年 | 71篇 |
2003年 | 61篇 |
2002年 | 70篇 |
2001年 | 51篇 |
2000年 | 51篇 |
1999年 | 32篇 |
1998年 | 99篇 |
1997年 | 74篇 |
1996年 | 55篇 |
1995年 | 44篇 |
1994年 | 27篇 |
1993年 | 36篇 |
1992年 | 20篇 |
1991年 | 17篇 |
1990年 | 8篇 |
1989年 | 14篇 |
1988年 | 9篇 |
1987年 | 9篇 |
1986年 | 11篇 |
1985年 | 12篇 |
1984年 | 4篇 |
1983年 | 7篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1977年 | 3篇 |
1976年 | 15篇 |
1975年 | 3篇 |
1974年 | 3篇 |
排序方式: 共有3024条查询结果,搜索用时 23 毫秒
101.
M Santana A?e B Villaverde A?e A Morales Landrove J Pérez Avila 《Canadian Metallurgical Quarterly》1997,49(2):142-144
Tear lactoferrin concentration was measured by ELISA technique and followed in 30 patients undergoing cataract surgery. On the first day following surgery, there was a significant decrease in tear lactoferrin concentration followed by a gradual return to the initial values during the postoperative observation period of 7 days. There was an inverse linear relationship between tear lactoferrin concentration and the tear secretion rate measured by a modified Schirmer I test (1 min) suggesting a constant lactoferrin secretion by the tear glands. Since lactoferrin has known antibacterial and anti-inflammatory effects, the results may contribute to further understanding of the microbial vulnerability or resistance of the eye following surgical procedures. 相似文献
102.
103.
Enrique Snchez Rafael Borja Lissette Travieso Manuel F Colmenarejo Arturo Chica Antonio Martín 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2004,79(8):851-862
A study of the effect of organic volumetric loading rate (BV) on the performance of a down‐flow anaerobic fixed bed reactor (DFAFBR) treating settled piggery waste was carried out at a range of between 1.1 and 6.8 g COD dm?3 d?1. The reactor operated at good removal efficiencies and stability under the operational conditions studied. Logarithmic empirical equations described adequately the removal efficiency for different parameters studied (COD, SCOD, BOD, TS, VS, TSS, VSS and phosphorous). Although process stability was affected by the increase of BV, process failure was not observed. A logarithmic relationship was found to describe the influence of BV on the TVFA/alkalinity ratio (p). A linear correlation was found between the effluent substrate concentration and the values of p and between p and the CO2/CH4 ratio in the biogas. The effect of the hydraulic volumetric loading rate (HV) on the flow pattern of the reactor was evaluated. Dispersion number (Dn) was in the range of 0.17–0.37 for the maximum and minimum values of HV studied, respectively. The ratio between the real and theoretical HRT increased as the HV decreased. These results demonstrate that axial dispersion increased as the HV and the Reynolds number decreased. Due to the hydraulic behaviour of the reactor, the kinetic model developed by Lawrence and McCarty was used for describing the experimental results obtained. Maximum specific substrate removal rate (K), specific organic loading rate constant (KL), microbial decay coefficient (Kd), microbial yield coefficient (Y), maximum microbial growth rate (UM) and saturation constant (KS) were found to be: 3.1 (g COD g VSS?1 d?1), 3.0 (g COD g VSS?1 d?1), 0.062 (d?1), 0.15 (g VSS g COD removed?1), 0.39 (d?1) and 2.6 (g SCOD dm?3), respectively. Copyright © 2004 Society of Chemical Industry 相似文献
104.
One aim of pervasive computing is to allow users to share their resources so that they seem to be part of a single pervasive computer. This is just an illusion, the result of the synergy between different systems and resources. SHAD, introduced in PerCom 2007, is the first architecture that offers actual Single Sign-On to avoid authentication obtrusiveness and maintain the illusion of a single, pervasive computer. This paper describes how SHAD allows users to securely share their resources in a easy, natural, and intuitive way. It also describes its role-based Human-to-Human architecture, the threat model, and the protocols involved. Last but not the least, it presents results of further evaluation for our working implementation. 相似文献
105.
Bing Q. Han Enrique J. Lavernia Farghalli A. Mohamed 《Metallurgical and Materials Transactions A》2004,35(4):1343-1350
The evolution of dislocation structure in pure Fe during equal-channel-angular pressing (ECAP) is investigated. Also, the
effect of the formation of this dislocation structure on deformation and fracture behavior is examined. The results show that
intensive dislocation cell blocks are present after one pass and even more after subsequent pressings. The low-energy dislocation
structures (LEDS) may have changed into the high-energy dislocation structures (HEDS) in the final several pressings. The
high-density array of dislocations plays a significant role in strengthening. The HEDS may cause the materials to lose work-hardening
ability and show a cleavage morphology of the fracture surface. A proper subsequent annealing treatment will lead to the evolution
of HEDS to LEDS while maintaining little grain growth. This change in the nature of dislocation structures allows ultrafine-grained
materials to achieve an excellent combination of high strength and high ductility. 相似文献
106.
Yolanda Moreno M. Carmen Collado M. Antonia Ferrús José M. Cobo Enrique Hernández & Manuel Hernández 《International Journal of Food Science & Technology》2006,41(3):275-280
The viability of lactic acid bacteria (LAB) from commercial fermented milks was studied during storage at 4 °C. The enumeration of total viable bacteria was assessed using fluorescence microscopy. Plate counting on selective media was used to enumerate LAB. Using LIVE/DEAD® BacLightTM viability staining, it was observed that bacterial counts decreased gradually after expiry dates, the number of viable bacteria remaining above 106 bacteria g?1 for all of the products. Viable cell counts estimated by plating onto selective media were lower than those obtained by direct microscopic counting. The viability of LAB contained in acid products decreased during their storage period at 4 °C. All products contain viable LAB ranging from 108 to 109 bacteria g?1 and could be considered as probiotic, given that the recommended minimum number of probiotic bacteria in such food products is approximately 107 bacteria mL?1 product. The number of bifidobacteria in commercial fermented milks declared to contain bifidobacteria varied from 104 to 107 bacteria mL?1. This study confirms the usefulness of fluorescent techniques for a rapid and accurate evaluation of bacterial viability in probiotic products. 相似文献
107.
O Rambeau R Morales de Lafond P Baldoni J P Gosselin J C Baccou 《Water science and technology》2004,50(2):139-147
Oil and gas production gives rise to water production depending on the state of maturation of the Field. This means large volumes of water available. Today, this water is partly re-injected into the reservoir. Totalfinaelf's sustainable contribution to preserve water resources is to propose an alternative utilization: the reuse of produced waters from petroleum activities, outside the food chain. The aim of the first part of this study is to demonstrate the feasibility of utilizing low-salt water (<20 g/l) cleaned of hydrocarbons, for agricultural or forest irrigation. Rudimentary technologies such as artificial wetlands were tested to remove hydrocarbon substances and preliminary tests were performed with cotton (Gossypium hirsutum) and hemp (Cannabis sativa). Among the species tested in real conditions (greenhouse), hemp was affected by saline water whereas the results obtained for cotton were representative of the average worldwide production. These results validate the reuse of low-salt produced water in climatic conditions with expected temperatures of up to 37 degrees C in summer and 25 degrees C in winter. Following these results, field pilots are planned. Further research is planned to focus, taking into account local needs and environmental and production constraints. 相似文献
108.
Ricardo Díaz‐Calleja Abel García‐Bernab Enrique Snchez‐Martínez Andrea Hormazbal Ligia Gargallo Deodato Radi 《Polymer International》2002,51(12):1448-1458
Dielectric behaviour of two poly(methacrylate)s with cyclobutyl groups in the side‐chains has been studied. This investigation was performed by determining the dielectric permittivity and loss in terms of frequency and temperature for poly(cyclobutyl methacrylate) (PCBuM) and poly(cyclobutylmethyl methacrylate) (PCBuMM). Dynamic dielectric measurements show sub‐glass relaxations, probably due to motions in the lateral chain, including the cyclobutyl ring. The effect of the insertion of a flexible spacer group into the side‐chain is also analyzed. The α relaxations were analyzed in terms of the Havriliak–Negami equation and the free volume theory tested according to the Vogel–Fulcher–Tamman–Hesse equation. The conductive and interfacial phenomena were studied by hopping and MacDonald–Coelho models. © 2002 Society of Chemical Industry 相似文献
109.
Monica Bocco Gustavo Ovando Silvina Sayago Enrique Willington Susana Heredia 《International journal of remote sensing》2013,34(6):1717-1728
The ground cover is a necessary parameter for agronomic and environmental applications. In Argentina, soybean (Glycine max (L.) Merill) is the most important crop; therefore it is necessary to determine its amount and configuration. In this work, neural-network (NN) models were developed to calculate soybean percentage ground cover (fractional vegetation cover, fCover) and to compare the accuracy of the estimate from Moderate-Resolution Imaging Spectroradiometer (MODIS) and Landsat satellites data. The NN design included spectral values of the red and near-infrared (NIR) bands as input variables and one neuron output, which expressed the estimated coverage. Data of fCover were acquired throughout the growing season in the central plains of Córdoba (Argentina); they were used for training and validating the networks. The results show that the NNs are an appropriate methodology for estimating the temporal evolution of soybean coverage fraction from MODIS and Landsat images, with coefficients of determination (R 2) equal to 0.90 and 0.91, respectively. 相似文献
110.
Aggregation of system-wide information in large-scale distributed systems, such as p2p systems and Grids, can be unfairly influenced by nodes that are selfish, colluding with each other, or are offline most of the time. We present AVCOL, which uses probabilistic and gossip-style techniques to provide availability-aware aggregation. Concretely, AVCOL is the first aggregation system that: (1) implements any (arbitrary) global predicate that explicitly specifies any node’s probability of inclusion in the global aggregate, as a mathematical function of that node’s availability (i.e., percentage time online); (2) probabilistically tolerates large numbers of selfish nodes and large groups of colluders; and (3) scales well with hundreds to thousands of nodes. AVCOL uses several unique design decisions: per-aggregation tree construction where nodes are allowed a limited but flexible probabilistic choice of parents or children, probabilistic aggregation along trees, and auditing of nodes both during aggregation as well as in gossip-style (i.e., periodically). We have implemented AVCOL, and we experimentally evaluated it using real-life churn traces. Our evaluation and our mathematical analysis show that AVCOL satisfies arbitrary predicates, scales well, and withstands a variety of selfish and colluding attacks. 相似文献