全文获取类型
收费全文 | 853篇 |
免费 | 44篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 9篇 |
综合类 | 1篇 |
化学工业 | 240篇 |
金属工艺 | 9篇 |
机械仪表 | 17篇 |
建筑科学 | 14篇 |
能源动力 | 11篇 |
轻工业 | 50篇 |
水利工程 | 4篇 |
石油天然气 | 13篇 |
无线电 | 106篇 |
一般工业技术 | 143篇 |
冶金工业 | 106篇 |
自动化技术 | 177篇 |
出版年
2023年 | 7篇 |
2022年 | 9篇 |
2021年 | 16篇 |
2020年 | 12篇 |
2019年 | 18篇 |
2018年 | 13篇 |
2017年 | 18篇 |
2016年 | 27篇 |
2015年 | 28篇 |
2014年 | 29篇 |
2013年 | 31篇 |
2012年 | 35篇 |
2011年 | 48篇 |
2010年 | 33篇 |
2009年 | 35篇 |
2008年 | 57篇 |
2007年 | 51篇 |
2006年 | 46篇 |
2005年 | 34篇 |
2004年 | 26篇 |
2003年 | 28篇 |
2002年 | 24篇 |
2001年 | 13篇 |
2000年 | 8篇 |
1999年 | 20篇 |
1998年 | 18篇 |
1997年 | 32篇 |
1996年 | 15篇 |
1995年 | 10篇 |
1994年 | 12篇 |
1993年 | 18篇 |
1992年 | 11篇 |
1991年 | 12篇 |
1990年 | 4篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 5篇 |
1983年 | 8篇 |
1982年 | 7篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1971年 | 3篇 |
1957年 | 2篇 |
1924年 | 2篇 |
排序方式: 共有900条查询结果,搜索用时 15 毫秒
1.
This paper describes a new formalism for inheritance systems, based on the formal semantics of set expressions. Using the formalism, it is possible to define new semantic classes by arbitrary set expressions operating on previously defined classes. Thus generalizing bothIS-A links andIS-NOT-A links and adding the set intersection operation. We present an efficient algorithm which follows these definitions to deduce the properties implied by the inheritance network, i.e., the properties of the classes containing a given element. The application which motivated the development of the formalism, namely semantic disambiguation of natural language, is also described. 相似文献
2.
This paper presents a technique for characterizing the statistical properties and spectrum of power supply noise using only two on-chip low-throughput samplers. The samplers utilize a voltage-controlled oscillator to perform high-resolution analog-to-digital conversion with minimal hardware. The measurement system is implemented in a 0.13-/spl mu/m process along with a high-speed link transceiver. Measured results from this chip validate the accuracy of the measurement system and elucidate several aspects of power supply noise, including its cyclostationary nature. 相似文献
3.
Ezequiel R. Soulé Guillermo E. Eliçabe Roberto J. J. Williams 《Polymer Bulletin》2008,60(2-3):417-423
An unexpected experimental finding is reported where the primary morphology developed during polymerization-induced
phase separation in a rubber-modified thermoplastic practically disappears at high conversions. This process
was evidenced by light scattering (LS) and scanning electron microscopy (SEM) for a particular composition
of solutions of polyisobutylene oligomers (PIB) in isobornylmethacrylate (IBoMA), during the free-radical
polymerization of the monomer. The primary phase separation produced a dispersion of domains rich in PIB
containing significant amounts of the monomer (IBoMA). Polymerization of the monomer in these domains occurred
at high overall conversions producing the filling of dispersed domains with a PIBoMA-PIB blend that could
not be distinguished from the matrix. Under these conditions the final material had the appearance of a
homogeneous blend. 相似文献
4.
Robert R. Gillies Jayne Brim Box Jürgen Symanzik Eli J. Rodemaker 《Remote sensing of environment》2003,86(3):411-422
Impervious surface area (ISA) was derived for a period from 1979 to 1997 from Landsat MSS and TM data for the Line Creek watershed that lies to the south of the city of Atlanta, GA. The change in ISA is presented as an ecological indicator to examine the cumulative water resource impacts on mussel population in three sub-watersheds of Line Creek—namely, Line, Flat, and Whitewater creeks. The satellite analysis shows that ISA expansion occurred substantially from 1987 to 1997 and is predominantly in industrial, commercial, and shopping center (ICS) complexes but also in smaller lot-size residential development. Evidence of mussel habitat degradation is indicated and loss of species (in the region of 50 to 70%) is present in areas where ISA expansion is observed—specifically in ICS complex development in and around Peachtree City that drains directly into the Line and Flat creeks. This is in marked contrast to Whitewater Creek where overall development of ISA is less and no major loss of mussel species is observed. 相似文献
5.
OBJECTIVE: To investigate the efficacy of the rectus abdominis muscle flap (RAMF) technique for the closure and augmentation of small, non-compliant bladder exstrophies. PATIENTS AND METHODS: The RAMF technique was used in two girls and two boys (mean age at operation, 31.7 months, range 3-72) with bladder exstrophy. The clinical outcome and urodynamics were assessed during a follow-up of 29 months to 6 years (mean 49.2 months) and included imaging, cystoscopy, biochemical and microbiological studies. RESULTS: There were no urinary tract infections, metabolic problems or electrolyte disturbances and kidney function remained normal in all patients. Radiography confirmed intact function and anatomy of the urinary tract and cystoscopy showed complete coverage of the inner peritoneal layer of RAMF with uroepithelium. No stone formation or mucus production were detected. Currently, three patients void using clean intermittent catheterization through the native urethra and the fourth through an appendiceal Mitrofanoff valve. However, the bladder volume was insufficient at the late follow-up and three patients required bladder augmentation. CONCLUSIONS: The RAMF technique is a good alternative for closing bladder exstrophies and achieves an increase in bladder capacity; however, although there is a mild improvement in bladder capacity and compliance. RAMF should not be used as a bladder augmentation procedure. The technique is indicated in the closure of large bladder defects, bladder exstrophies with small, inelastic, non-compliant bladder remnants and failed primary closures. 相似文献
6.
Fractionation of partly hydrolysed polyvinyl acetate (PVA) was performed by warming of its aqueous solutions. The following properties of the obtained fractions were determined: viscosity, molecular weight and molecular weight distribution, surface tension, and absorbance in the IR range. The blockiness of the polymer molecules, characterized by their behaviour towards iodine-containing systems such as I2,-H3BO3 and I2,-KI, was estimated. Fractionation of the aqueous solutions of PVA by warming is based mainly on the different internal molecular structure of the separated products, i.e. on the length of the vinyl acetate blocks in the PVA molecules and, to a lesser extent, on the degree of hydrolysis and the degree of polymerization. The more blocklike are the PVA molecules, the less compatible are the polymers in the PVA-hydroxypropyl methylcellulose (HPMC)-water system. At phase separation in this sytem the PVA molecules which are not compatible with HPMC are, in the first place, those of the highest blockiness. 相似文献
7.
Minor Thomas R.; Dess Nancy K.; Ben-David Eli; Chang Wei-Chao 《Canadian Metallurgical Quarterly》1994,20(4):402
The present study determined whether individual differences in neophobia during an open-field pretest predict vulnerability to inescapable electric shock, as measured by 2 tests of learned helplessness in rats. Shuttle-escape latencies and saccharin finickiness increased across groups that had received increasing numbers of inescapable shocks 24 hr earlier. Dispersion in the test measure as well as the percentage of variance explained by pretest neophobia were greater when no or few shocks were delivered in the interpolated stress phase. Pretest neophobia was positively related to stress vulnerability in both tests under these conditions. Further increments in stressor severity overwhelmed even the most stress-resistant rats, thereby decreasing dispersion in the test measure and eliminating the predictive value of pretest neophobia. This pattern of outcomes was more robust for the shuttle-escape measure of helplessness. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
8.
A series of poly(vinyl chloride) (PVC)/polyaniline (PANI) blends plasticized and protonated simulataneously by bis(2-ethylhexyl) hydrogen phosphate, bis(4-nitrophenyl) phosphate, diphenyl phosphate, or dibenzyl phosphate was prepared by a mass homogenization technique. Thermal analysis studies by means of thermo-gravimetric analysis (TGA) and differential scanning calorimetry (DSC) revealed that PVC/PANI blends with bis(2-ethylhexyl) hydrogen phosphate were characterized by the highest thermal stability values. Kinetic analysis of the decomposition process by the isoconversional Friedman method showed that the activation energy did not change substantially over the broad conversion range; further advanced kinetic analysis by a nonlinear regression method revealed that the kinetic function that was the best approximation for the experimental data was based on a reaction of nth order. 相似文献
9.
Analysis of advertisements in Israeli newspapers over the past decade has shown that American symbols have been widely used to market an array of consumer goods. Products made in America, Israel, or other countries are marketed with some sort of American angle by invoking America's values, symbols, landscapes, or lifestyle. Using both qualitative and quantitative methods, we analyzed how central components of the nation-state/national sphere—language, flag, political leaders, borders, landscapes, and sights—are reflected in advertising. We attempt to show how social values metamorphose, shedding their "Israeliness" and taking on an American veneer. Using Israel as an example may provide a test case for the Americanization process in other societies at the turn of the millennium. 相似文献
10.
Rattok Jack; Ross Barbara; Ben-Yishay Yehuda; Ezrachi Ora; Silver Saralyn; Lakin Phyllis; Vakil Eli; Piasetsky Eugene; Zide Ellen; Diller Leonard 《Canadian Metallurgical Quarterly》1992,6(4):395
Within a clinical demonstration program, 59 traumatically brain-injured patients were treated with 1 of 3 mixes of treatment. Mix 1 included cognitive remediation (CGR), small-group interpersonal (SGI) communication training, therapeutic community activities, and personal counseling. Mix 2 was similar to Mix 1 but stressed SGI exercises and eliminated CGR. Mix 3 emphasized CGR and eliminated SGI exercises. The efficacy of the treatment mixes was evaluated with performance on neuropsychological tests, improved independence in functional activities, measures of intra- and interpersonal functioning, and vocational outcome. Ss' participation in the program, irrespective of treatment mix, yielded improvements in (1) self-image, (2) quality of interpersonal relatedness and interaction, (3) involvement with others in naturalistic settings, and (4) vocational outcome. Overall, data point to the superiority of the balanced mix (Mix 1) over Mixes 2 and 3. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献