全文获取类型
收费全文 | 564篇 |
免费 | 29篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 11篇 |
综合类 | 1篇 |
化学工业 | 132篇 |
金属工艺 | 13篇 |
机械仪表 | 11篇 |
建筑科学 | 34篇 |
能源动力 | 14篇 |
轻工业 | 39篇 |
石油天然气 | 1篇 |
武器工业 | 1篇 |
无线电 | 44篇 |
一般工业技术 | 162篇 |
冶金工业 | 58篇 |
原子能技术 | 3篇 |
自动化技术 | 70篇 |
出版年
2023年 | 8篇 |
2022年 | 7篇 |
2021年 | 20篇 |
2020年 | 16篇 |
2019年 | 14篇 |
2018年 | 10篇 |
2017年 | 16篇 |
2016年 | 16篇 |
2015年 | 18篇 |
2014年 | 20篇 |
2013年 | 50篇 |
2012年 | 29篇 |
2011年 | 34篇 |
2010年 | 24篇 |
2009年 | 21篇 |
2008年 | 23篇 |
2007年 | 23篇 |
2006年 | 18篇 |
2005年 | 23篇 |
2004年 | 20篇 |
2003年 | 17篇 |
2002年 | 17篇 |
2001年 | 8篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1995年 | 10篇 |
1993年 | 4篇 |
1991年 | 5篇 |
1990年 | 7篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 8篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1976年 | 3篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1968年 | 3篇 |
1966年 | 3篇 |
1938年 | 3篇 |
1937年 | 3篇 |
1928年 | 2篇 |
1913年 | 3篇 |
1912年 | 2篇 |
排序方式: 共有594条查询结果,搜索用时 15 毫秒
81.
The submitted work discussed the possibility of using two of the most problematic wastes to formulate an added‐value hard wood‐composite (HWC). The lignocellulosic rice straws (RS) fibers (as reinforced filler) and recycled expanded polystyrene foam (PS) wastes (as dispersed polymer matrix), were used to formulated the hard wood product applying the hot press technique. The air dried RS was added to the molten PS at increasing ratios (30–70% mass:mass), and the reached HWC sheet was subjected to tensile strength, water absorption and acoustic resistance characterizations. Based on the experimental data, it was found that increasing the RS contents accompanied with a diminish in the tensile strength value by about 50% at 70% RS compare to that at 30% RS. To improve the adhesion between the hydrophilic filler RS and the hydrophobic PS matrix, maleated PS graft (PS‐g‐MA) was prepared and added at the expanse of the PS content, to formulate an additional wood‐composite (HWCg) aiming to have better mechanical and dimensional stability features. Results obtained indicated that increasing the coupling agent content, keeping the RS added constant, enhance the tensile strength feature in addition, reduced the water absorption for the final products by more than 45%. The data obtained suggested that, it can create added‐value hard wood composites entirely from the two nominated problematic wastes. In addition to the value gained by the environment, the reached hard wood products record acceptable mechanical characterization, dimensional stability and sound resistance properties that qualified it to replace the natural wood in many daily applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44770. 相似文献
82.
Daniel F. Schafer II Peter T. Wolczanski Emil B. Lobkovsky Samantha N. MacMillan 《Israel journal of chemistry》2017,57(10-11):982-989
Treatment of (tBu3SiNH)(tBu3SiN=)2WH ( 1 -H) with small alkyl anions (RM) afforded tungsten alkyl hydride anions [(tBu3SiNH)(tBu3SiN=)2HWR)]M ( 3 -(R)M: R=CH3, M=Li; R=nBu, M=Li; R=neoPe, M=Li; R=CH2Ph (Bn), M=K (two isomers); R=CCH, M=Na; R=CH=CH2 (Vy), M=Li). The saturated alkyl anions 3 -(R)M ( 3 -(R)M: R=CH3, M=Li; R=nBu, M=Li; R=neoPe, M=Li; R=CH2Ph (Bn), M=K) degraded via apparent 1,2-RH-elimination to produce the known [(tBu3SiN=)3WH]M ( 2 -HM), but the acetylide ( 3 -(C2H)Na) and vinyl ( 3 -(Vy)Li) anions converted to their hydrogenated isomers, [(tBu3SiN=)3WVy]Na ( 2 -VyNa) and [(tBu3SiN=)3WEt]Li ( 2 -EtLi), respectively. The structure of 3 -(nBu)Li is reported, and a discussion of tungsten-hydride coupling constants in tBu3SiX-ligated (X=O, NH, N) systems is given. 相似文献
83.
We study the issue of whether the wind load factors specified in the ASCE 7–95 Standard for hurricane- prone regions on the one hand and extratropical storm regions on the other are mutually consistent with respect to risk. We consider structures or elements whose design is governed by wind loads and for which wind directionality effects are not significant. We present estimates according to which ASCE 7–95 Standard provisions for wind loads inducing the design strength result in (1) safety levels that are considerably lower for hurricane-prone than for extratropical storm regions, and (2) estimates of mean recurrence intervals of hurricane wind loads inducing the design strength of about 500 y if epistemic uncertainties are neglected, and significantly lower than 500 years otherwise. 相似文献
84.
Anastasio MA Zou Y Sidky EY Pan X 《Journal of the Optical Society of America. A, Optics, image science, and vision》2007,24(6):1569-1579
We develop reconstruction algorithms for local cone-beam tomography for use with generalized scanning trajectories. The algorithms are grounded theoretically in a recently developed chord-based theory for exact image reconstruction and principles of lambda tomography. Being chord based, they are distinct mathematically and conceptually from conventional local tomography reconstruction algorithms. The salient feature of our algorithms is that they permit reconstruction of discontinuities in the profiles of the object function along chords. By consideration of all possible chords, a 3D image that describes the locations of object discontinuities can be reconstructed. Results from microlocal analysis are applied for understanding the object features that can be reconstructed stably by use of the algorithms. A computer-simulation study is conducted to demonstrate the algorithms and compare their performance with an existing algorithm. 相似文献
85.
Leschkies KS Divakar R Basu J Enache-Pommer E Boercker JE Carter CB Kortshagen UR Norris DJ Aydil ES 《Nano letters》2007,7(6):1793-1798
We combine CdSe semiconductor nanocrystals (or quantum dots) and single-crystal ZnO nanowires to demonstrate a new type of quantum-dot-sensitized solar cell. An array of ZnO nanowires was grown vertically from a fluorine-doped tin oxide conducting substrate. CdSe quantum dots, capped with mercaptopropionic acid, were attached to the surface of the nanowires. When illuminated with visible light, the excited CdSe quantum dots injected electrons across the quantum dot-nanowire interface. The morphology of the nanowires then provided the photoinjected electrons with a direct electrical pathway to the photoanode. With a liquid electrolyte as the hole transport medium, quantum-dot-sensitized nanowire solar cells exhibited short-circuit currents ranging from 1 to 2 mA/cm2 and open-circuit voltages of 0.5-0.6 V when illuminated with 100 mW/cm2 simulated AM1.5 spectrum. Internal quantum efficiencies as high as 50-60% were also obtained. 相似文献
86.
Tindale R. Scott; Heath Linda; Edwards John; Posavac Emil J.; Bryant Fred B.; Suarez-Balcazar Yolanda; Henderson-King Eaaron; Myers Judith 《Canadian Metallurgical Quarterly》1999,3(4):313
Review of book: R. Scott Tindale et. al (Eds.) Theory and Research on Small Groups. New York: Plenum Press. 1998, 277 pp. Reviewed by Mark F. Stasson, Michael J. Markus, and Jason W. Hart. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
87.
Rodolfa Emil R.; Vieille Richard; Russell Peter; Nijjer Sukhvender; Nguyen Dao Q.; Mendoza Mary; Perrin Lori 《Canadian Metallurgical Quarterly》1999,30(4):415
As an internship applicant, do you know what internship agencies look for to select or exclude you from further consideration? In a survey, the authors examined exclusion and inclusion criteria used at 402 internship sites accredited by the American Psychological Association (APA). The 249 respondents (62%) rated fit between applicant goals and site opportunities as the most important inclusion criteria. Four exclusion criteria (lack of completion of orals, lack of APA status of doctoral program, poor fit between applicant goals and site opportunities, and incomplete doctoral course work) were most commonly used to eliminate applicants from consideration. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
88.
Novel polyurethane cationomers bearing p-nitroazoaromatic groups covalently incorporated in the polymer chain were synthesized. Their photobehavior in polymer films and solutions was investigated by electronic absorption spectroscopy and was also evaluated comparatively with an ionic azodiol model. Under UV irradiation, in the first stage of the photoprocess the trans-cis isomerization occurs, followed then by a photobleaching reaction in the second stage of the process. 相似文献
89.
Andrea Bírov Emil vajdlenka Jn Cvengros Viera Dostlíkov 《European Journal of Lipid Science and Technology》2002,104(5):271-277
This paper presents the results of two methods employed to determine the methyl ester (ME) fraction in mixed fuels prepared from MEs of higher fatty acids and fossil Diesel fuel. The first method is based on determining the ester number of the mixed fuel. The second one utilises the measurement of the carbonyl band intensity in the mixed fuel by infrared (IR) spectroscopy. The ME fraction in the tested mixed fuels was always set to 30 wt‐%. Applying the first method the ester numbers of mixed fuels were determined and the ME fraction was defined using an averaged molar mass of ME. The differences between the values of the measured and real fraction of ME varied between −0.2 and +0.8 wt‐%. If the value of the average molar mass of ME was not known, the molar mass of methyl oleate was used as a reference. Thereby the differences in determining the ME fraction in mixed fuels ranged between −0.1 and +0.9 wt‐%. Employing the IR spectroscopy method the differences between the measured and the real fraction of ME varied between −1.0 and +0.5 wt‐%. Both methods are suitable to determine the ME fraction in mixed fuels. 相似文献
90.
Roychowdhury H Agrawal GP Wolf E 《Journal of the Optical Society of America. A, Optics, image science, and vision》2006,23(4):940-948
Expressions are derived for the cross-spectral density matrix of an electromagnetic Gaussian Schell-model beam propagating through a paraxial ABCD system. Using the recently developed unified theory of coherence and polarization of electromagnetic beams and the ABCD matrix for gradient-index fibers, we study the changes of the spectral density, of the spectral degree of polarization, and of the spectral degree of coherence of such a beam as it travels through the fiber. Effects of material dispersion are also considered. 相似文献