全文获取类型
收费全文 | 475篇 |
免费 | 35篇 |
专业分类
电工技术 | 3篇 |
化学工业 | 116篇 |
金属工艺 | 10篇 |
机械仪表 | 18篇 |
建筑科学 | 30篇 |
能源动力 | 34篇 |
轻工业 | 54篇 |
水利工程 | 7篇 |
石油天然气 | 4篇 |
无线电 | 36篇 |
一般工业技术 | 87篇 |
冶金工业 | 43篇 |
原子能技术 | 1篇 |
自动化技术 | 67篇 |
出版年
2023年 | 23篇 |
2022年 | 28篇 |
2021年 | 49篇 |
2020年 | 26篇 |
2019年 | 27篇 |
2018年 | 24篇 |
2017年 | 27篇 |
2016年 | 23篇 |
2015年 | 17篇 |
2014年 | 21篇 |
2013年 | 36篇 |
2012年 | 12篇 |
2011年 | 24篇 |
2010年 | 13篇 |
2009年 | 14篇 |
2008年 | 16篇 |
2007年 | 7篇 |
2006年 | 10篇 |
2005年 | 4篇 |
2004年 | 6篇 |
2003年 | 2篇 |
2002年 | 8篇 |
2001年 | 2篇 |
2000年 | 10篇 |
1999年 | 5篇 |
1998年 | 10篇 |
1997年 | 5篇 |
1996年 | 11篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1991年 | 7篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1984年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1972年 | 1篇 |
排序方式: 共有510条查询结果,搜索用时 15 毫秒
51.
It is shown that the form of a laid-down thread can be expressed mathematically by the equation of a modified cycloid when the speed ratio between the feed and the belt is within a certain range. The experimental form is found to be reasonably close to the theoretical form. The theoretical form can be predicted if the radius of the circular coil with the belt stationary, the feed speed, and the belt speed are known, The condition for laying down the thread in a form of overlapping loops is deduced. A strobo-photographic method is used to clarify the existence of different mechanisms under different conditions. 相似文献
52.
An objective screening technique for fabric handle is presented. This method is based on the use of a simple device fitted to a tensile testing machine, and measures the force generated while passing a fabric specimen through a ring. The method proved capable of detecting differences in fabric handle between comparable fabrics, as illustrated by studies on shirting fabrics, and on fabrics with functional finishes. The results were validated by comparison with measurements of fabric mechanical properties obtained from the KESF (Kawabata Evaluation System for Fabrics). The handle force measurement gives a summed single value result for fabric handle. 相似文献
53.
A kinetic method for the determination of vitamin C, citrate and oxalate in their mixture is described. The method involves the use of cerium(IV) as an oxidant and measurement of reaction rates spectrophotometrically by following the decrease in absorbance of cerium(IV) at 410 nm. The adaptive Kalman filter was used for data manipulation and analysis. It is shown that the use of the Kalman filter is superior to the classical differential kinetic methods owing to its suitability for the determination of analytes that react with a single reagent and exhibit a reaction rate constant ratio of less than 1.5. The results obtained were found to be highly precise and accurate even in the presence of some expected interferents. 相似文献
54.
An investigation on the operation of packed tower for the regeneration of liquid desiccant is presented. A theoretical model demonstrating the effect of the system parameters is described. The experimental results are plotted to illustrate the effect of air and liquid parameters on the output variables. The regeneration process is shown to be highly dependent on the air inlet conditions, namely, temperature, humidity and flow rate. Also, the effects of the liquid temperature, concentration and flow rate is discussed. Data obtained were correlated to estimate the rate of water evaporation (regeneration rate) from values of variables that influence the rate of mass transfer in the column. 相似文献
55.
A rigorous analysis of the features of the modes of an annular sector printed microstrip antenna is presented. General expressions for its radiation field are derived by using the cavity model. The expressions are used to study the radiation patterns, radiation peak in the broadside direction, and beamwidth of different structures for various sector angles, widths, and modes of excitation. This includes the special cases of quarter-, half-, three-quarters-, and ideal-gap open-ring structures. Compared to a closed ring, the results indicate that the TM12 mode is superior to the TM11 mode with regard to the radiation properties in the annular sector as its angle approaches 2π 相似文献
56.
The crosslinking reactions of a new type of polyethylene, an ethylene vinyltrimethoxy silane (EVS) copolymer, when reacted with water has been studied. Samples of EVS were treated in water at 90°C. The kinetics of the crosslinking was followed by measuring the gel content and by determination of the content of different structures (? Si? OCH3,? Si? OH, and ? Si? O? Si? ) using FT-IR. The observations show that a maximum gel content of 70-75% is obtained after 25 h treatment in water at 90°C. On the other hand, the absorption index for the crosslinks, ? Si? O? Si? , continues to increase until about 100 h, i.e., more crosslinks seem to be formed without a simultaneous increase in gel content. Mechanical measurements showed decreased elongation at break even after very long treatments. Thermo-oxidative degradation is, however, also responsible for the change in mechanical properties. For properly stabilized samples, the decrease in elongation leveled off after about 100 h of treatment. This indicates that the crosslinks formed after 25 h mainly should be within the already existing gel. The observed synergistic effect of crosslinking and thermo-oxidative degradation emphasizes the importance of a proper stabilizing system. 相似文献
57.
Syed Adnan Ali Shah Huey Ling Tan Sadia Sultan Muhammad Afifi Bin Mohd Faridz Mohamad Azlan Bin Mohd Shah Sharifah Nurfazilah Munawar Hussain 《International journal of molecular sciences》2014,15(7):12027-12060
Microbial-catalyzed biotransformations have considerable potential for the generation of an enormous variety of structurally diversified organic compounds, especially natural products with complex structures like triterpenoids. They offer efficient and economical ways to produce semi-synthetic analogues and novel lead molecules. Microorganisms such as bacteria and fungi could catalyze chemo-, regio- and stereospecific hydroxylations of diverse triterpenoid substrates that are extremely difficult to produce by chemical routes. During recent years, considerable research has been performed on the microbial transformation of bioactive triterpenoids, in order to obtain biologically active molecules with diverse structures features. This article reviews the microbial modifications of tetranortriterpenoids, tetracyclic triterpenoids and pentacyclic triterpenoids. 相似文献
58.
Suhana M Sultan Nonofo J Ditshego Robert Gunn Peter Ashburn Harold MH Chong 《Nanoscale research letters》2014,9(1):517
This paper studies the effect of atomic layer deposition (ALD) temperature on the performance of top-down ZnO nanowire transistors. Electrical characteristics are presented for 10-μm ZnO nanowire field-effect transistors (FETs) and for deposition temperatures in the range 120°C to 210°C. Well-behaved transistor output characteristics are obtained for all deposition temperatures. It is shown that the maximum field-effect mobility occurs for an ALD temperature of 190°C. This maximum field-effect mobility corresponds with a maximum Hall effect bulk mobility and with a ZnO film that is stoichiometric. The optimized transistors have a field-effect mobility of 10 cm2/V.s, which is approximately ten times higher than can typically be achieved in thin-film amorphous silicon transistors. Furthermore, simulations indicate that the drain current and field-effect mobility extraction are limited by the contact resistance. When the effects of contact resistance are de-embedded, a field-effect mobility of 129 cm2/V.s is obtained. This excellent result demonstrates the promise of top-down ZnO nanowire technology for a wide variety of applications such as high-performance thin-film electronics, flexible electronics, and biosensing. 相似文献
59.
Neslihan Temizel Giray Girisken A. Cuneyt Tas 《Materials science & engineering. C, Materials for biological applications》2011,31(5):1136-1143
This study investigated the hydrothermal transformation of brushite (dicalcium phosphate dihydrate, DCPD, CaHPO4·2H2O) into octacalcium phosphate (OCP, Ca8(HPO4)2(PO4)4·5H2O) in seven different newly developed biomineralization media, all inspired from the commercial DMEM solutions, over the temperature range of 36.5 °C to 90 °C with aging times varying between 1 h and 6 days. DCPD powders used in this study were synthesized in our laboratory by using a wet-chemical technique. DCPD was found to transform into OCP in the Ca2+, Mg2+, Na+, K+, HCO3?, Cl? and H2PO4? containing aqueous biomineralization media in less than 72 h at 36.5 °C, without stirring. The same medium was able to convert DCPD into OCP in about 2 h at 75–80 °C, again without a need for stirring. Samples were characterized by using powder X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). 相似文献
60.
Sultan F. Bohra A. Smaldone S. Pan Y. Gallard P. Neamtiu I. Iftode L. 《Internet Computing, IEEE》2005,9(2):17-27
Current Internet service architectures lack support for salvaging stateful client sessions when the underlying operating system fails due to hangs, crashes, deadlocks, or panics. The backdoors (BD) system is designed to detect such failures and recover service sessions in clusters of Internet servers by extracting lightweight state associated with client service sessions from server memory. The BD architecture combines hardware and software mechanisms to enable accurate monitoring and remote healing actions, even in the presence of failures that render a system unavailable. 相似文献