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131.
132.
用一级轻气炮对铁和镍两种材料动态加载。用透射电镜观察两种材料的位错结构。结果发现:受动加载作用后铁和镍的位错结构分别是类似于网状的和网状的结构。冲击波压力与位错密度有直接关系,而在本试验的条件下脉冲持续时间对位错密度没有影响。 相似文献
133.
Spatial analysis of annual air pollution exposure and mortality 总被引:1,自引:0,他引:1
Scoggins A Kjellstrom T Fisher G Connor J Gimson N 《The Science of the total environment》2004,321(1-3):71-85
The aim of this study was to relate ambient air pollution levels to mortality in Auckland, New Zealand. We used urban airshed modelling and GIS-based techniques to quantify long-term exposure to ambient air pollution levels and associated mortality. After adjusting for age, sex, ethnicity, socio-economic status, and urban/rural domicile there was a 1.3% (95%CI: 1-1.5%) increase in non-external cause mortality, and 1.8% (95%CI: 1.5-2.1%) increase in circulatory and respiratory causes per 1 microg/m(3) increase in annual average NO(2). Based on these exposure-response relationships and applying an annual average threshold of 13 microg/m(3), the average annual (for 1996-1999) number of people estimated to die from non-external causes and circulatory and respiratory causes attributable to air pollution in Auckland is 268 (95% range: 227-310) (3.9% of total all cause deaths) and 203 (95% range: 169-237) (5.9% of total circulatory and respiratory deaths) per year, respectively. The number of attributable deaths found in this study are consistent with a previous New Zealand risk assessment using a different methodology, and is approximately twice the number of people dying from motor vehicle accidents in the region, which is on average (1996-1999) 103 per year. The GIS-based exposure maps identify high exposure areas for policy developers and planners in a simple and realistic manner. Taken together with overseas studies the study provides additional evidence that long-term exposure to poor air quality, even at levels below current standards, is a hazard to the public health. 相似文献
134.
The purpose of this study was to determine the effect of load position in an internal frame backpack on physiological and perceptual variables. Ten female participants walked on a level treadmill for 10 min carrying 25% of their body weight in a high, central, or low position. The variables measured included oxygen consumption (VO2), heart rate (HR), respiratory exchange ratio (R), respiratory rate (RR), minute ventilation (VE), and rating of perceived exertion (RPE). VO2, VE, and RPE were significantly lower in the high position (18.6 +/- 2.3 ml/kg/min, 31.7 +/- 5.0 l/min, 2.8 +/- 0.8, respectively) compared to the low position (22.2 +/- 3.0 ml/kg/min, 38.6 +/- 7.5 l/min, 3.7 +/- 1.0, respectively). HR, R, and RR did not change significantly as the load was moved from the high (129.8 +/- 16.8, 0.89 +/- 0.06, 30.3 +/- 4.2, respectively) to the low position (136.0 +/- 25.3, 0.92 +/- 0.04, 33.8 +/- 5.2, respectively). The results of this study suggest that load placement is an important factor in the physiological and perceptual responses to load carriage, and that packing heavy items high in the backpack may be the most energy efficient method of carrying a load on the back. 相似文献
135.
Reddish brown flocs form along the edge of the Coeur d'Alene River when porewater drains into river water during the annual lowering of water level in the basin. The precipitates are efficient scavengers of dissolved elements and have characteristics that may make metals associated with them bioavailable. This work characterizes the geochemistry of the porewater and models the formation and composition of the flocs. Porewater is slightly acidic, has suboxic to anoxic characteristics, tends to have higher alkalinity, and contains elevated concentrations of many constituents relative to river water. Laboratory mixing experiments involving porewater and river water were done to produce the precipitates. Thermodynamic predictions using PHREEQC indicate that predicted amounts of ferrihydrite and gibbsite agree with removal of Fe and Al. Predictions of element removal by adsorption onto ferrihydrite are consistent with observed removal using a combination of surface complexation constants for the generalized two-layer model (As and Se), alternative surface constants derived from experiments at high sorbate-to-sorbent ratios (Cd, Co, Cu, Ni, Pb, and Zn), and adjusted surface constants to fit experimental data (Cr, Mo, and Sb). This new set of surface complexation constants needs further testing in other contaminated systems. 相似文献
136.
Mittal Vijay A.; Tessner Kevin D.; Trottman Hanan D.; Esterberg Michelle; Dhruv Shivali H.; Simeonova Diana I.; McMillan Amanda L.; Murphy Erin; Saczawa Mary E.; Walker Elaine F. 《Canadian Metallurgical Quarterly》2007,116(2):260
The link between movement abnormalities and psychotic disorders is presumed to reflect common neural mechanisms that influence both motor functions and vulnerability to psychosis. The prodromal period leading to psychotic disorders represents both a viable point for intervention and a developmental period that, if studied, could shed light on etiology; however, no published studies have examined the temporal progression of this link. A group with high levels of prodromal symptomatology (i.e., adolescents with schizotypal personality disorder [SPD]; n = 42) and both psychiatric controls (with other personality disorders or conduct disorder [OD]; n = 30) and nonpsychiatric controls ([NC]; n = 49) were recruited. Videotapes of structured psychiatric interviews were coded for movement abnormalities by raters blind to participants' diagnostic status, and follow-up assessments were conducted 1 year later. Controlling for psychotropic medications, the authors found that adolescents with SPD exhibited significantly more motor abnormalities in the face and upper body than did OD and NC controls. At baseline, movement abnormalities were positively correlated with the severity of positive, negative, and total prodromal symptoms. Within the SPD group, baseline movement abnormalities predicted symptom severity 1 year later. Movement abnormalities represent an early risk indicator that may be predictive of later symptom severity and potentially of psychosis onset. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
137.
Amanda M. Kimbrough Rosanna E. Guadagno Nicole L. Muscanell Janeann Dill 《Computers in human behavior》2013
Past research in gender differences in the overall Internet use has been contradictory. Some asserted men used it more than women, while others asserted there were no gender difference. Both camps concluded that men and women differed in their motivation and utilization of time spent online. The purpose of the present research was to take a contemporary look at these gender differences. Using an online survey, we asked participants about their experiences with multiple forms of mediated communication: social networking sites, e-mail, video calls, instant messaging, texting, and phone calls. Our results indicated that women, compared to men, are generally more frequent mediated communication users. Compared to men, women prefer and more frequently use text messaging, social media, and online video calls. These results suggest that the nature of mediated social interaction is changing. 相似文献
138.
Particulate matter (PM) air‐quality information is usually derived from ground‐based instruments. These measurements, while valuable, are not well suited to provide air‐quality information over large spatial scales. In this study, using 4 years of satellite aerosol optical thickness (AOT) at 0.55 µm derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) on board NASA's Terra and Aqua satellites, we present a multi‐year air analysis of PM air quality over Sydney, Australia. We then compare the satellite data with PM2.5 mass concentration measurements from six ground‐based stations in the area. Our results indicate significant diurnal variations and an overall increase in PM2.5 during Southern Hemisphere spring and summer seasons due to bush fires. The air quality in Sydney, Australia is good throughout the year except during major bushfires when PM2.5 mass loading can increase from normal (<20 µg m?3) to unhealthy conditions (>70 µg m?3). The satellite data also show corresponding AOT changes from less than 0.1 to greater than 1.0 during bushfire events. We conclude that satellite data are an excellent tool for studying PM air quality over large areas, especially when ground measurements are not available. While this is the first multi‐year combined satellite and ground‐based air quality analysis over Sydney, ancillary information from lidars, sun photometers, and size‐resolved chemistry measurements will further enhance our capability to monitor and forecast air quality in and around Sydney. 相似文献
139.
Rodrigo Bonacin Amanda M. Melo Carlos A. C. Simoni M. Cecília C. Baranauskas 《Universal Access in the Information Society》2010,9(1):17-33
The multidisciplinary nature of e-government demands a research agenda that includes issues related to social inclusion, universal
accessibility, interoperability, privacy, security, and citizen participation, to name a few. Understanding the underlying
cultural context, the involvement of citizens in the proposal and evaluation of services, and the promotion of quality in
use are aspects that need special consideration in the development of systems to support government. This paper provides an
outline for a process model for promoting the identification and specification of accessible e-government services with the
participation of the interested parties. A socially shared perspective is adopted toward the comprehension of the involved
problems and the elaboration of potential solutions. The proposed model is a result of practice in the domain, using organizational
semiotics artifacts to stimulate participation and discussion. 相似文献
140.
Trends in marine composites 总被引:1,自引:0,他引:1