全文获取类型
收费全文 | 1253篇 |
免费 | 24篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 14篇 |
综合类 | 1篇 |
化学工业 | 151篇 |
金属工艺 | 8篇 |
机械仪表 | 15篇 |
建筑科学 | 49篇 |
矿业工程 | 2篇 |
能源动力 | 12篇 |
轻工业 | 112篇 |
水利工程 | 33篇 |
石油天然气 | 2篇 |
无线电 | 73篇 |
一般工业技术 | 154篇 |
冶金工业 | 483篇 |
原子能技术 | 5篇 |
自动化技术 | 164篇 |
出版年
2023年 | 4篇 |
2022年 | 6篇 |
2021年 | 7篇 |
2019年 | 17篇 |
2018年 | 22篇 |
2017年 | 16篇 |
2016年 | 12篇 |
2015年 | 16篇 |
2014年 | 19篇 |
2013年 | 47篇 |
2012年 | 33篇 |
2011年 | 54篇 |
2010年 | 45篇 |
2009年 | 44篇 |
2008年 | 44篇 |
2007年 | 66篇 |
2006年 | 57篇 |
2005年 | 42篇 |
2004年 | 34篇 |
2003年 | 33篇 |
2002年 | 26篇 |
2001年 | 25篇 |
2000年 | 24篇 |
1999年 | 30篇 |
1998年 | 84篇 |
1997年 | 68篇 |
1996年 | 43篇 |
1995年 | 36篇 |
1994年 | 28篇 |
1993年 | 35篇 |
1992年 | 31篇 |
1991年 | 14篇 |
1990年 | 17篇 |
1989年 | 15篇 |
1988年 | 11篇 |
1987年 | 9篇 |
1986年 | 13篇 |
1985年 | 12篇 |
1984年 | 11篇 |
1983年 | 13篇 |
1982年 | 9篇 |
1981年 | 8篇 |
1980年 | 9篇 |
1979年 | 8篇 |
1978年 | 12篇 |
1977年 | 13篇 |
1976年 | 11篇 |
1975年 | 8篇 |
1973年 | 5篇 |
1971年 | 5篇 |
排序方式: 共有1278条查询结果,搜索用时 223 毫秒
21.
To select a source of lymphocytes for the generation of an anti-sperm-biased combinatorial phage display library, venous blood was obtained from 34 vasovasostomy (vasectomy reversal) patients approximately 3 mo after surgery. Using a variety of immunoassays, serum was analyzed for antibodies against human spermatozoa, and a patient was selected on the basis of high titer of antibodies that recognized the equatorial region of the sperm head and inhibited sperm fertilizing capacity in vitro. Total RNA isolated from the stored lymphocytes of this individual was reversed transcribed, and gamma1 (Fd) region and kappa chains were amplified by polymerase chain reaction for the successful construction of an antibody phage display library. The library was panned against human spermatozoa to isolate sperm-specific phage that recognized the equatorial region of the sperm head. Three preparations of Fab were tested via the hamster egg penetration test. Each preparation significantly (p < 0. 005) inhibited sperm-egg binding and fusion, with one preparation (designated Fab-G) causing complete inhibition. Sequence analysis of the kappa light gene encoding Fab-G revealed a 93% homology with the light chain of human anti-human immunodeficiency virus gp120 p35 variable region. This technology may have a practical application in characterization of the immune response to spermatozoa and for the design of sperm-based contraceptive vaccines. 相似文献
22.
Tracy L. Westeyn Gregory D. Abowd Thad E. Starner Jeremy M. Johnson Peter W. Presti Kimberly A. Weaver 《Personal and Ubiquitous Computing》2012,16(2):169-191
Previous research has established the connection between the way in which children interact with objects and the potential
early identification of children with autism. Those findings motivate our own work to develop "smart toys," objects embedded with wireless sensors that are safe and enjoyable for very small children, that allow detailed interaction
data to be easily recorded. These sensor-enabled toys provide opportunities for autism research by reducing the effort required
to collect and analyze a child’s interactions with objects. In the future, such toys may be a useful part of clinical and
in-home assessment tools. In this paper, we discuss the design of a collection of smart toys that can be used to automatically
characterize the way in which a child is playing. We use statistical models to provide objective, quantitative measures of
object play interactions. We also developed a tool to view rich forms of annotated play data for later analysis. We report
the results of recognition experiments on more than fifty play sessions conducted with adults and children as well as discuss
the opportunities for using this approach to support video annotation and other applications. 相似文献
23.
On The Measurement of Temperature in Material Removal Processes 总被引:5,自引:0,他引:5
Because it is key to understanding the performance of material removal processes and resultant workpiece quality, the measurement of temperature during material removal is done extensively. We review several widely used temperature measurement methods and show how they can be applied to temperature monitoring during material removal. Since there is little documentation on measurement uncertainties as relates to material removal, this paper outlines the physics of each method, detailing the sources and evaluation of uncertainty. Finally, using criteria critical in measuring material removal, methods are compared, and the results presented in guide-format for participants in this field of work. 相似文献
24.
Anthony Walker Matthew Driller Christos Argus Julie Cooke Ben Rattray 《Ergonomics》2014,57(4):612-621
Currently, there is no enforcement of physical standards within Australian fire services post-recruitment, possibly leading to inappropriate fitness and body composition. This study evaluated the impacts of ageing on physical standards of Australian firefighters. Seventy-three firefighters from three different 10-year age groups [25–34 years (n = 27), 35–44 years (n = 27), 45–54 years (n = 19)] volunteered for physical testing using dual-energy X-ray analysis and existing fitness tests used for recruitment by an Australian fire service. Older (45–54 years) participants demonstrated significantly poorer physical standards compared with younger participants including cardiovascular fitness (p < 0.05), strength (p = 0.001) and simulated operational power testing tasks (p < 0.001). Age-related body composition changes were also observed independent of body mass index. Minimum recruitment standards and fitness programs need to account for age-related declines in physical capabilities to ensure that the minimum standard is maintained regardless of age.
Practitioner Summary: Using dual-energy X-ray analysis and established fitness testing protocols, this study aimed to gain an appreciation of the current standards of body composition and fitness of Australian firefighters and the effects of ageing on their physical abilities post-recruitment. The study demonstrated a significant decline in physical standards due to age. 相似文献
25.
Tracy Q. Gardner Ana I. Flores Richard D. Noble John L. Falconer 《American Institute of Chemical Engineers》2002,48(6):1155-1167
A transient permeation method presented here not only determines the adsorption and diffusion properties of the pores that are the transport pathways through zeolite membranes, but nondestructively estimates the effective thickness of the membrane. Transient responses of the permeate concentration to step changes in the feed were measured on two H-ZSM-5 tubular membranes and modeled assuming Maxwell-Stefan diffusion and Langmuir adsorption. The adsorption isotherms determined from these transient measurements at 298 K of N2 and CO2 were nearly identical to those measured by calorimetry on H-ZSM-5 powders. The CH4 isotherm at 298 K was similar to isotherms measured by calorimetry and gravimetric techniques on Na-ZSM-5 and silicalite powders. The similarity of the isotherms indicates that transport of these light gases occurs mainly through zeolite pores. The Maxwell-Stefan diffusion coefficients DMS depended on concentration and were higher for higher feed partial pressures. Average DMS values for the two membranes were 7.5, 5 and 1.5×10−10 m2/s for N2, CH4, and CO2, respectively; these are in the same range and order as diffusion coefficients measured in zeolite crystals. 相似文献
26.
William M. Tracy 《Computational Economics》2014,43(1):83-103
The classical game theoretic resolutions to Selten’s Chain Store game are unsatisfactory; they either alter the game to avoid the paradox or struggle to organize the existing experimental data. This paper applies co-evolutionary algorithms to the Chain Store game and demonstrates that the resulting system’s dynamics are neither intuitively paradoxical nor contradicted by the existing experimental data. Specifically, some parameterizations of evolutionary algorithms promote genetic drift. Such drift can lead the system to transition among the game’s various Nash Equilibria. This has implications for policy makers as well as for computational modelers. 相似文献
27.
Mark A. Kaemingk Tracy L. Galarowicz John A. Clevenger David F. Clapp 《Journal of Great Lakes research》2011,37(4):625-631
Fish movement may vary across a wide array of aquatic ecosystems and may be related to the overall size of the system inhabited. We investigated movement of smallmouth bass in Lake Michigan because this information is lacking for larger systems. A total of 16 smallmouth bass were surgically implanted with ultrasonic transmitters within the Beaver Archipelago, northern Lake Michigan. During 2007-2008, a maximum of one location per individual was recorded daily during three specific tracking periods - pre-spawn, spawning, and post-spawn - to determine diurnal movement patterns. Movement was evaluated as site fidelity, minimum displacement rate, maximum excursion rate, and distance from shore. Smallmouth bass exhibited greater maximum excursion rates during the spawn period compared to pre-spawn. Movement rates did not differ between tracking periods; however, movement rates were greater during the spawn period in 2007 than 2008. Both sexes moved further offshore to deeper water during post-spawn, but females were located further offshore than males during this period. Annual site fidelity was more evident during post-spawn than during spawning for both sexes. Two smallmouth bass emigrated outside of the Archipelago, suggesting this population may be more “open” in terms of individuals moving throughout northern Lake Michigan than previously thought. These results indicate smallmouth bass may move greater distances in larger aquatic systems and therefore larger management units (in terms of total area) should be established in Lake Michigan to account for these greater excursion distances. 相似文献
28.
Calorimetry offers a direct measurement of thermodynamic properties of materials, including information on the energetics of phase transitions. Many materials can only be prepared in thin film or small crystal (submilligram) form, negating the use of traditional bulk techniques. The use of micromachined, membrane-based calorimeters for submilligram bulk samples is detailed here. Numerical simulations of the heat flow for this use have been performed. These simulations describe the limits to which this calorimetric technique can be applied to the realm of small crystals (1-1000 microg). Experimental results confirm the feasibility of this application over a temperature range from 2 to 300 K. Limits on sample thermal conductivity as it relates to the application of the lumped and distributed tau 2 models are explored. For a typical sample size, the simulations yield 2.5% absolute accuracy for the heat capacity of a sample with thermal conductivity as low as 2 x 10(-5) W/cm K at 20 K, assuming a strong thermal link to the device. Silver paint is used to attach (both thermally and physically) the small samples; its heat capacity and reproducibility are discussed. Measurements taken of a submilligram single crystal of cobalt oxide (CoO) compare favorably to the results of a bulk calorimetric technique on a larger sample. 相似文献
29.
The main problem of interval computations is as follows:given sets of possible valuesX i for variablesx i, and an algorithmf:R n → R, to.estimate the rangef(X 1, ..,X n ) of the possible values off(x 1, ...,x n ). In many real-life, situations setsX i are not intervals. To handle such problems, it is desirable to add set data type and operations with sets to a programming language. it is well known that the entire mathematics can be formulated in terms of sets. So, if we already have a set as a data type, why have anything else. The main reason, is that expression in terms of sets is often clumsy. To avoid this clumsiness, it has been suggested to use not only sets, but alsobags (multisets), in which an element can have multiple occurrences. Bags are used in many areas of Computer Science, and recently, several languages have appeared that use the bag as a basic data type. In this paper, we explain the main ideas behind bag languages, and we also show: · that bag languages are naturally parallelizable, thus leading to a parallelization of the coresponding generalized interval computations; · and that bag languages can be also helpfully applied to traditional interval computations (where setsX i are intervals). 相似文献
30.
EP Gerstenfeld Y Balarajan R Cooke RS Mittleman 《Canadian Metallurgical Quarterly》1998,114(2):637-639
A 36-year-old man with a history of hypertrophic obstructive cardiomyopathy presented to the emergency room with "stabbing" chest pain. He had undergone dual-chamber pacemaker implantation in 1993 using an atrial lead (Accufix; Telectronics; Englewood, Colo) and a myomectomy in 1996 during which the distal portion of the atrial lead was removed. Digital fluoroscopy revealed that the retention wire had migrated out of the remaining atrial lead and perforated the right atrium. The retention wire was successfully removed percutaneously. The need for complete removal of the retention wire in the Accufix lead at the time of open-heart surgery is emphasized. 相似文献