全文获取类型
收费全文 | 4363篇 |
免费 | 97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 | 187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 | 41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4465条查询结果,搜索用时 15 毫秒
991.
Chandra S. Sharma Palghat A. Ramachandran Ronald Hughes 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1976,26(5):231-238
The kinetics of the oxidation of carbon monoxide over five commercially available oxide catalysts have been determined at CO concentrations of 4–15 mol% and initial temperatures up to 170°C. The reaction showed a fractional dependence on the concentration of CO and was inhibited by CO2. From an analysis of the data a Langmuir-Hinshelwood reaction scheme is proposed. 相似文献
992.
Gayland F. Spencer Ronald D. Plattner Thomas Miwa 《Journal of the American Oil Chemists' Society》1977,54(5):187-189
Two analytical procedures for determining com-positions of jojoba liquid wax esters are described and compared. One, the more
tedious, involves separation of wax ester homologs by high pressure liquid chro-matography followed by determination of the
acid and alcohol moieties from each homolog. The second allows rapid determination of wax ester composition by gas Chromatographic
separation of hydrogenated jojoba wax esters according to chain length, followed immediately by ancillary mass spectrometric
identifi-cation of the acid and alcohol moieties. Double bonds in the alkyl chains in jojoba liquid waxes were almost exclusively
(98%) ω-9, when examined by gas chro-matography/mass spectrometry (GC/MS) and ozonolysis/GC/MS.
Presented in part at the 2nd International Conference on Jojoba and Its Uses, Ensenada, Mexico, February, 1976. 相似文献
993.
Ronald R. Yager 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2013,17(3):391-399
We introduce the concept of a membership modification function and describe its role in transforming one fuzzy set into another. We discuss the related idea of a membership modification program consisting of a collection of related membership modification functions and show how the concept of level sets is an example of a membership modification program. Using this idea of membership modification allows us to consider other transformations of fuzzy sets that soften the idea of level sets. Using these ideas we provide an extension of the Jaccard similarity index. 相似文献
994.
Manginell RP Moorman MW Rejent JA Vianco PT Grazier MJ Wroblewski BD Mowry CD Achyuthan KE 《The Review of scientific instruments》2012,83(3):031301
The deleterious consequences of climate change are well documented. Future climate treaties might mandate greenhouse gas (GHG) emissions measurement from signatories in order to verify compliance. The acquisition of atmospheric chemistry would benefit from low cost, small size/weight/power of microsystems. In this paper, we investigated several key materials science aspects of a phase-change microvalve (PCμV) technology with low power/size/weight/cost for ubiquitous GHG sampling. The novel design, based on phase-change material low-melting-point eutectic metal alloys (indium-bismuth, InBi and tin-lead, SnPb), could be actuated at temperatures as low as 72 °C. Valve manufacturing was based on standard thick and thin-film processes and solder technologies that are commonly used in industry, enabling low-cost, high-volume fabrication. Aging studies showed that it was feasible to batch fabricate the PCμVs and store them for future use, especially in the case of SnPb alloys. Hermetic sealing of the valve prototypes was demonstrated through helium leak testing, and Mil spec leak rates less than 1 × 10(-9) atm cm(3)/s were achieved. This confirms that the sample capture and analysis interval can be greatly expanded, easing the logistical burdens of ubiquitous GHG monitoring. Highly conservative and hypothetical CO(2) bias due to valve actuation at altitude in 1 cm(3) microsamplers would be significantly below 1.0 and 2.2 ppmv for heat-treated InBi and SnPb solders, respectively. The CO(2) bias from the PCμV scales well, as a doubling of sampler volume halved the bias. We estimated the shelf life of the SnPb PCμVs to be at least 2.8 years. These efforts will enable the development of low cost, low dead volume, small size/weight microsystems for monitoring GHGs and volatile organic compounds. 相似文献
995.
Dual-beam focused ion beam microscopy (FIB/SEM) preparation of rock varnish for high-resolution transmission electron microscopy (HR-TEM) has enabled us to characterize unreported nanostructures. Fossils, unreported textures, and compositional variability were observed at the nanoscale. These techniques could provide a method for studying ancient terrestrial and extra-terrestrial environments to better understand geological processes at the nanoscale. 相似文献
996.
Lance C. Hibbeler Brian G. Thomas Ronald C. Schimmel Gert Abbel 《Metallurgical and Materials Transactions B》2012,43(5):1156-1172
This article investigates the thermal distortion of a funnel mold for continuous casting of thin slabs and explores the implications on taper and solidification of the steel shell. The three-dimensional mold temperatures are calculated using shell-mold heat flux and cooling water profiles that were calibrated with plant measurements. The thermal stresses and distorted shape of the mold are calculated with a detailed finite-element model of a symmetric fourth of the entire mold and waterbox assembly, and they are validated with plant thermocouple data and measurements of the wear of the narrow-face copper mold plates. The narrow-face mold distorts into the typical parabolic arc, and the wide face distorts into a ??W?? shape owing to the large variation in bolt stiffnesses. The thermal expansion of the wide face works against the applied narrow-face taper and funnel effects, so the effect of thermal distortion must be considered to accurately predict the ideal mold taper. 相似文献
997.
Pattama Saisaha Lea Buettner Margarethe vanderMeer Ronald Hage Ben L. Feringa Wesley R. Browne Johannes W. deBoer 《Advanced Synthesis \u0026amp; Catalysis》2013,355(13):2591-2603
The manganese‐containing catalytic system [MnIV,IV2O3(tmtacn)2]2+ ( 1 )/carboxylic acid (where tmtacn=N,N′,N′′‐trimethyl‐1,4,7‐triazacyclononane), initially identified for the cis‐dihydroxylation and epoxidation of alkenes, is applied for a wide range of oxidative transformations, including oxidation of alkanes, alcohols and aldehydes employing H2O2 as oxidant. The substrate classes examined include primary and secondary aliphatic and aromatic alcohols, aldehydes, and alkenes. The emphasis is not primarily on identifying optimum conditions for each individual substrate, but understanding the various factors that affect the reactivity of the Mn‐tmtacn catalytic system and to explore which functional groups are oxidised preferentially. This catalytic system, of which the reactivity can be tuned by variation of the carboxylato ligands of the in situ formed [MnIII,III2(O)(RCO2)2(tmtacn)2]2+ dimers, employs H2O2 in a highly atom efficient manner. In addition, several substrates containing more than one oxidation sensitive group could be oxidised selectively, in certain cases even in the absence of protecting groups.
998.
Mentzoni Michael H. Row Ronald V. Montgomery Charles E. 《IEEE transactions on nuclear science》1964,11(1):3-11
Experimental observations of reflection and transmission of a cw wave propagating in the quasi TE11 mode in a cylindrical wave guide filled with a time decaying plasma are presented. The discharge column occupies, with the exception of a thin layer of quartz, the entire cross-section of the wave guide. The transmitted wave displays a series of optima whose relative amplitudes increase with decreasing electron density. With regard to phase separation, frequency and pressure variation the extrema seem to fit a simple theoretical model, which, however, fails to explain the absorption mechanism, the latter being also associated with a reversed cross-modulation not explainable by the Ramsauer effect. 相似文献
999.
Carole M. McNamee Ronald A. Olsson 《International journal of parallel programming》1991,20(3):181-202
Earlier work has shown the effectiveness of hand-applied program transformations optimizing high-level interprocess communication mechanisms. This paper describes the static analysis techniques necessary to ensure correct compiler application of the optimizing transformations. These techniques include both dataflow analysis and interprocess analysis. This paper focuses on the analysis of communication mechanisms within program modules; however, the analysis techniques can be generalized to handle inter-module optimization analysis as well. The major contributions of this paper include the application of dataflow analysis and the extension of interprocedural analysis—interprocess analysis—to real concurrent programming languages and, more specifically, to the optimization of interprocess communication and synchronization mechanisms that use both static and dynamic channels. In addition, the use of attribute grammars to perform interprocess analysis is significant. This paper also describes an implementation of both intra-process dataflow and interprocess analysis techniques using attribute grammars.This work was supported by NSF under Grant Number CCR88-10617. 相似文献
1000.
Damping characteristics of composite materials and structures 总被引:1,自引:0,他引:1
This paper presents an overview of experimental and analytical approaches that have been used to characterize damping properties
of composite materials and structures, with emphasis on polymer composites. A discussion of damping mechanisms operating in
composites is followed by a review of several experimental methods for measuring damping. A summary of analytical models for
predicting damping at both the micromechanical and macromechanical levels is presented and comments on ways of improving and
optimizing damping in composites are offered. 相似文献