全文获取类型
收费全文 | 4353篇 |
免费 | 106篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 44篇 |
综合类 | 1篇 |
化学工业 | 848篇 |
金属工艺 | 79篇 |
机械仪表 | 75篇 |
建筑科学 | 186篇 |
矿业工程 | 23篇 |
能源动力 | 85篇 |
轻工业 | 392篇 |
水利工程 | 26篇 |
石油天然气 | 18篇 |
无线电 | 260篇 |
一般工业技术 | 650篇 |
冶金工业 | 1090篇 |
原子能技术 | 53篇 |
自动化技术 | 634篇 |
出版年
2022年 | 33篇 |
2021年 | 41篇 |
2019年 | 37篇 |
2018年 | 37篇 |
2017年 | 40篇 |
2016年 | 56篇 |
2015年 | 51篇 |
2014年 | 76篇 |
2013年 | 245篇 |
2012年 | 141篇 |
2011年 | 170篇 |
2010年 | 149篇 |
2009年 | 168篇 |
2008年 | 197篇 |
2007年 | 194篇 |
2006年 | 178篇 |
2005年 | 133篇 |
2004年 | 124篇 |
2003年 | 109篇 |
2002年 | 123篇 |
2001年 | 92篇 |
2000年 | 85篇 |
1999年 | 77篇 |
1998年 | 64篇 |
1997年 | 74篇 |
1996年 | 74篇 |
1995年 | 81篇 |
1994年 | 75篇 |
1993年 | 76篇 |
1992年 | 90篇 |
1991年 | 33篇 |
1990年 | 70篇 |
1989年 | 56篇 |
1988年 | 59篇 |
1987年 | 67篇 |
1986年 | 66篇 |
1985年 | 89篇 |
1984年 | 86篇 |
1983年 | 81篇 |
1982年 | 83篇 |
1981年 | 74篇 |
1980年 | 45篇 |
1979年 | 61篇 |
1978年 | 60篇 |
1977年 | 55篇 |
1976年 | 52篇 |
1975年 | 64篇 |
1974年 | 38篇 |
1973年 | 39篇 |
1972年 | 32篇 |
排序方式: 共有4464条查询结果,搜索用时 15 毫秒
71.
Edmund F. Jordan Steven Smith Ronald E. Koos Winfred E. Parker Bohdan Artymyshyn A. N. Wrigley 《应用聚合物科学杂志》1978,22(6):1509-1528
Compositionally and structurally varied copolymers all containing n-octadecyl acrylate were prepared and evaluated as viscosity index improvers in a common base oil under conditions of low shear. Systems evaluated over a range of copolymer and blend composition were: copolymers of n-octadecyl acrylate with, respectively, methyl methacrylate, 2-ethylhexyl acrylate, and n-dodecyl acrylate; and homopolymers of poly(n-octadecyl acrylate), prepared with a wide range of molecular weights. Properties were compared with those of blends of commercial methacrylate copolymers (acryloids) which had been freed of their entraining liquid. Mixtures of base oil with copolymers of n-octadecyl acrylate and methyl methacrylate, compared at fixed SAE viscosities, were the most efficient of all blends studied. They had the smallest rate of change of viscosity with temperature (as measured by their ASTM slopes), particularly in the composition region of incipient polymer precipitation at room temperature. Efficiency of certain of these composition was somewhat greater than that of the acryloids. A parameter that related concentration and weight-average molecular weight was used to correlate all of the data for ASTM slope and viscosity. Empirical relations developed by using this parameter enabled rheological data to be estimated that agree within 6% of experimental values for the case of thermodynamically good base oil solvents. These data demonstrated the relatively small contributions of copolymer structure to viscosity index improvement. 相似文献
72.
The attractiveness of different synthetic host odors and a synthetic aggregation pheromone (grandisoic acid [GA]) to overwintered adult plum curculios (PCs), Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae), was examined using two types of traps (sticky panels and black pyramids) placed in border areas surrounding an unsprayed section of an apple orchard in Massachusetts. In 2001, we evaluated the response of PCs to three synthetic fruit volatiles (benzaldehyde [BEN], ethyl isovalerate [EIV], and limonene [LIM]) assessed alone and in combination with GA, as well as the response to GA alone and a no-odor (control) treatment. BEN was the only host volatile that synergized the response of PCs to GA for both trap types. For both trap types, GA was as attractive to PCs as a single component as when in combination with either EIV or LIM. In 2002, four release rates of BEN (0, 2.5, 10, and 40 mg/day) and two release rates of GA (1 and 2 mg/day) were evaluated for attractiveness to PCs using panel and pyramid traps. For panel traps, an increase in amount of GA released (from 1 to 2 mg/day) was associated with a 35% increase in captures. However, PC captures by pyramid traps were similar regardless of the amount of GA released. For panel traps, 10 and 40 mg/day of BEN were the most attractive release rates regardless of the amount of GA released. For pyramid traps baited with GA. PC captures were enhanced by the presence of BEN, regardless of release rate. In 2003, GA at 1 mg/day + BEN at 80 mg/day of release did not enhance PC captures by panel traps relative to lower release rates of BEN. Pyramid traps releasing GA at 1 mg/day performed best when baited with BEN at 10 mg/day of release; a release rate of 80 mg/day of BEN decreased the attractiveness of the binary combination of BEN + GA. Combined results suggest that BEN at 10 mg/day + GA at 1 mg/day of release constitutes an attractive lure that may improve the effectiveness of monitoring traps for PCs. 相似文献
73.
Christoph Windmeier Felix Flegiel Alexander Döß Ronald Franz Eckhard Schleicher Michael Wiezorek Markus Schubert Uwe Hampel 《化学,工程师,技术》2021,93(7):1119-1125
An optimized equipment design for natural gas processing and liquefaction plants becomes increasingly difficult with changing process conditions: Particularly low values of surface tension create rising challenges on the design of phase separators and column internals. The TERESA test rig at HZDR was designed to allow the investigation of multiphase thermohydraulics and phase separator performance under critical fluid properties in industrial dimensions. A versatile pipe test section is available in DN200 and equipment internals may be tested in a sectional DN300/DN500 test separator. The applied test fluid shows a high vapor-liquid density difference between 1470 and 940 kg m−3, viscosity as low as 0.12 mm2s−1, and surface tension down to 1.3 mN m−1. Volumetric liquid and vapor flow rates may be varied up to 9 and 530 m3h−1 in the test rig, respectively. 相似文献
74.
C. -X. Ji Peter F. Ladwig Ronald D. Ott Y. Yang Joshua J. Yang Y. Austin Chang Eric S. Linville Jenny Gao Bharat B. Pant 《JOM Journal of the Minerals, Metals and Materials Society》2006,58(6):50-54
Sputter-deposited, equiatomic PtMn thin films have application in giant magnetoresistive spin valves, tunneling magnetoresistive
spin valves, and magnetic random access memory. However, the as-deposited films are found to be a disordered A1 phase in a
paramagnetic state rather than an antiferromagnetic phase with L10 structure, which is needed for device operation. Therefore, a postannealing step is required to induce the phase transformation
from the asdeposited A1 face-centered-cubic phase to the antiferromagnetic L10 phase. The A1 to L10 metastable transformation was studied by x-ray diffraction and differential-scanning calorimetry. An exothermic transformation
enthalpy of −12.1 kJ/mol of atoms was determined. The transformation kinetics were simulated using the Johnson-Mehl-Avrami
analysis. 相似文献
75.
Alexander N. Chen James P. Downey Ronald E. McGaughey Kan Jin 《International journal of human-computer interaction》2016,32(2):132-142
Technology, particularly information technology (IT), is changing rapidly and offers many advantages for users. IT has the potential to improve one’s quality of life, but only if used. Research has shown that, in most developed and developing nations, senior use of IT lags behind that of other segments of society. This “gray divide” is a concern for government, business, and others. Concern about senior adoption and use of IT has been the motivation for numerous studies and is the motivation for this study of Chinese seniors. This exploratory study examines urban Chinese seniors’ IT use, computers and mobile phones in particular, but also their attitudes and behaviors as they relate to the use of those devices. More specifically it examines several potential factors that motivate or hinder senior’s use of information technology, including self-efficacy, satisfaction, comfort with technology, and both positive and negative attitudes. This study provides some insight into the quantity and diversity of Chinese senior technology use in urban China. Particularly noteworthy, the study found that technology ownership was quite high, and in general the Chinese seniors studied had positive attitudes and beliefs concerning information technology. This is generally good news for the Chinese government, which must efficiently provide services for the growing population of Chinese seniors, as well as for businesses that wish to capitalize on one of the largest senior populations in the world. 相似文献
76.
Ronald Poppe Khiet P. Truong Dirk Heylen 《Autonomous Agents and Multi-Agent Systems》2013,27(2):235-253
Artificial listeners are virtual agents that can listen attentively to a human speaker in a dialog. In this paper, we present two experiments where we investigate the perception of rule-based backchannel strategies for artificial listeners. In both, we collect subjective judgements of humans who observe a video of a speaker together with a corresponding animation of an artificial listener. In the first experiment, we evaluate six rule-based strategies that differ in the types of features (e.g. prosody, gaze) they consider. The ratings are given at the level of a speech turn and can be considered a measure for how human-like the generated listening behavior is perceived. In the second experiment, we systematically investigate the effect of the quantity, type and timing of backchannels within the discourse of the speaker. Additionally, we asked human observers to press a button whenever they thought a generated backchannel occurrence was inappropriate. Both experiments together give insights in the factors, both from an observation and generation point-of-view, that influence the perception of backchannel strategies for artificial listeners. 相似文献
77.
Park ND Thring RW Garton RP Rutherford MP Helle SS 《Water science and technology》2011,64(9):1851-1856
Anaerobic digestion is a well established technology for the reduction of organic matter and stabilization of wastewater. Biogas, a mixture of methane and carbon dioxide, is produced as a useful by-product of the process. Current solid waste management at the city of Prince George is focused on disposal of waste and not on energy recovery. Co-digestion of fresh fruit and vegetable waste with sewer sludge can improve biogas yield by increasing the load of biodegradable material. A six week full-scale project co-digesting almost 15,000 kg of supermarket waste was completed. Average daily biogas production was found to be significantly higher than in previous years. Digester operation remained stable over the course of the study as indicated by the consistently low volatile acids-to-alkalinity ratio. Undigested organic material was visible in centrifuged sludge suggesting that the waste should have been added to the primary digester to prevent short circuiting and to increase the hydraulic retention time of the freshly added waste. 相似文献
78.
Félix Gómez Mármol Christoph Sorge Ronald Petrlic Osman Ugus Dirk Westhoff Gregorio Martínez Pérez 《International Journal of Information Security》2013,12(2):67-82
The recent deployment of smart grids promises to bring numerous advantages in terms of energy consumption reduction in both homes and businesses. A more transparent and instantaneous measurement of electricity consumption through smart meters utilization leads to an enhancement in the ability of monitoring, controlling and predicting energy usage. Nevertheless, it also has associated drawbacks related to the privacy of customers, since such management might reveal their personal habits, which electrical appliances they are using at each moment, whether they are at home or not, etc. In this work, we present a privacy-enhanced architecture for smart metering aimed at tackling this threat by means of encrypting individual measurements while allowing the electricity supplier to access the aggregation of the corresponding decrypted values. 相似文献
79.
Image mosaic construction is about stitching together a number of images about the same scene to construct a single image with a larger field of view. The majority of the previous work was rooted at the use of a single image-to-image mapping termed planar homography for representing the imaged scene. However, the mapping is applicable only to cases where the imaged scene is either a single planar surface, or very distant from the cameras, or imaged under a pure rotation of the camera, and that greatly limits the range of applications of the mosaicking methods. This paper presents a novel mosaicking solution for scenes that are polyhedral (thus consisting of multiple surfaces) and that are pictured possibly in closed range of the camera. The solution has two major advantages. First, it requires only a few correspondences over the entire scene, not correspondences over every surface patch in it to work. Second, it conquers a seemingly impossible task—warping image data of surfaces that are visible in only one of the input images, which we refer to as the singly visible surfaces, to another viewpoint to constitute the mosaic there. We also provide a detail analysis of what determines whether a singly visible surface could be mosaicked or not. Experimental results on real image data are presented to illustrate the performance of the method. 相似文献
80.
It has been a common consensus that general techniques for stabilization of nonlinear systems are available only for some
special classes of nonlinear systems. Control design for nonlinear systems with uncertain components is usually carried out
on a per system basis, especially when physical control constraints, and certain control performance measures such as optimum
time control are imposed. Elegant adaptive control techniques are difficult to apply to this type of problems. A new neural
network based control design is proposed and presented in this paper to deal with a special class of uncertain nonlinear systems
with multiple inputs. The desired system dynamics are analyzed and utilized in the process of the proposed intelligent control
design. The theoretical results are provided to justify the design procedures. The simulation study is conducted on a second-order
bilinear system with two inputs and uncertainties on its parameters. The simulation results indicate that the proposed design
approach is effective. 相似文献