全文获取类型
收费全文 | 2835篇 |
免费 | 22篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 15篇 |
化学工业 | 132篇 |
金属工艺 | 34篇 |
机械仪表 | 23篇 |
建筑科学 | 23篇 |
矿业工程 | 2篇 |
能源动力 | 20篇 |
轻工业 | 132篇 |
水利工程 | 5篇 |
石油天然气 | 2篇 |
无线电 | 92篇 |
一般工业技术 | 164篇 |
冶金工业 | 2074篇 |
原子能技术 | 37篇 |
自动化技术 | 103篇 |
出版年
2021年 | 7篇 |
2019年 | 10篇 |
2018年 | 11篇 |
2017年 | 11篇 |
2016年 | 6篇 |
2015年 | 9篇 |
2014年 | 11篇 |
2013年 | 46篇 |
2012年 | 27篇 |
2011年 | 40篇 |
2010年 | 36篇 |
2009年 | 30篇 |
2008年 | 35篇 |
2007年 | 23篇 |
2006年 | 22篇 |
2005年 | 27篇 |
2004年 | 31篇 |
2003年 | 26篇 |
2002年 | 29篇 |
2001年 | 32篇 |
2000年 | 29篇 |
1999年 | 60篇 |
1998年 | 530篇 |
1997年 | 333篇 |
1996年 | 221篇 |
1995年 | 131篇 |
1994年 | 120篇 |
1993年 | 134篇 |
1992年 | 27篇 |
1991年 | 32篇 |
1990年 | 32篇 |
1989年 | 34篇 |
1988年 | 31篇 |
1987年 | 23篇 |
1986年 | 25篇 |
1985年 | 38篇 |
1984年 | 8篇 |
1983年 | 22篇 |
1982年 | 27篇 |
1981年 | 36篇 |
1980年 | 42篇 |
1979年 | 21篇 |
1978年 | 20篇 |
1977年 | 111篇 |
1976年 | 211篇 |
1975年 | 17篇 |
1974年 | 6篇 |
1973年 | 6篇 |
1972年 | 7篇 |
1971年 | 8篇 |
排序方式: 共有2858条查询结果,搜索用时 8 毫秒
961.
962.
TP Preobrazhenskaia LP Terekhova AV La?ko TI Selezneva VA Zenkova 《Canadian Metallurgical Quarterly》1976,21(9):779-784
Eight strains of actinomycetes isolated from soil samples were described as representatives of Actinomadura coeruleoviolacea sp.nov. The species was characterized by straight and sometimes branching short chains of spores, smooth spores, blue aerial mycellium and violet soluble pigment. All the strains showed antibacterial activity when cultivated in liquid media. The pigment differed from all known pigments. It is probably a new natural compound. 相似文献
963.
Morphological changes in the midpiece of wooly opossum spermatozoa during epididymal transit 总被引:1,自引:0,他引:1
Several ultrastructural changes were found to occur in the midpiece region of wooly opossum spermatozoa during epididymal maturation. The changes include alterations in mitochondrial morphology, development of structural specializations of the plasma membrane, and acquisition of a prominent extracellular coating. The lamellar membrane network which is wound about the periphery of the mitochondria becomes more densely packed during sperm development and the reticular network of membranes noted in the center of the mitochondria of immature sperm disappears leaving a homogeneous electron dense central zone. During epididymal transit the plasma membrane over the sperm midpiece region shows extensive structural modification. In cross sections of paired spermatozoa the plasma membrane of the midpiece regions shows a very regular, repetitive scalloping. In longitudinal sections the scalloping is observed as continuous parallel ridges which extend slightly obliquely to the flagellar long axis. Each ridge appears to be greater in density than the interridge areas. In the epididymis a prominent extracellular coating of dense material is deposited over the midpiece surface; this material is similar in appearance to dense material seen in restricted areas of the epididymal lumen. At the proximal and distal ends of the midpiece the plasma membrane comes into intimate contact with underlying structural specializations and it is suggested that these zones of fusion may serve to preserve regional differences in membrane composition. 相似文献
964.
The ability of selected phosphorus-containing compounds and nitrogen-containing compounds to act as flame retardants for cotton cellulose was investigated using flame tests, thermal gravimetric analysis (TGA), and differential thermal analysis (DTA). The effectiveness of the organophosphorus compounds was found to correlate with the changes which they induced in the pyrolytic degradation of the cellulose as indicated by DTA. Many of the samples containing nitrogen were found to exhibit DTA curves having pronounced exotherms. The presence of nitrogen-containing compounds in conjunction with the organophosphorus systems enhanced their ability to retard flame propagation but did not produce significant changes in the pyrolytic endotherm as observed by DTA. More conclusive evidence for a chemically based phosphorus-nitrogen synergism was obtained by the use of TGA. These data can be interpreted in terms of the phosphorus-nitrogen synergistic effects and flame retardance mechanisms which have been proposed in the literature. 相似文献
965.
966.
967.
968.
Characterization of silane-modified immobilized gold colloids as a substrate for surface-enhanced Raman spectroscopy 总被引:1,自引:0,他引:1
Immobilized gold colloid particles coated with a C-18 alkylsilane layer have been characterized as a substrate for surface-enhanced Raman scattering (SERS) studies of adsorption onto hydrophobic surfaces. Atomic force microscopy images, optical extinction spectra, and SERS measurements are reported as a function of accumulation of gold colloid on glass. As the metal particles become increasingly aggregated on the surface, the SERS enhancement increases until the plasmon resonance shifts to wavelengths longer than the excitation laser. The gold colloid substrates are stable and exhibit reproducible SERS enhancement. When octadecyltrimethoxysilane is self-assembled over the gold, the metal surface is protected from exposure to solution-phase species, as evidenced by the inhibition of chemisorption of a disulfide reagent to the overcoated gold surface. The results show that interactions with gold can be blocked by a silane layer so as not to significantly influence physisorption of molecules at the C-18/solution interface. The SERS enhancement from these C-18-overcoated gold substrates is reproducible for different films prepared from the same colloidal suspension; the substrates are also stable with time and upon exposure to laser irradiation. 相似文献
969.
Comments on the article "Psychology and Phenomenology: A Clarification" by H. H. Kendler (see record 2005-05480-003). In this article, Kendler sought to resolve the methodological issue that divides much of contemporary psychology--namely, the difference between natural science and human science in their respective views of psychological life. Whereas Kendler provided an evocative historical account of conflicts over how psychology has interpreted consciousness, the force of his analysis depends on the extent to which the proverbial "is/ought" distinction, invoked any time the question of "science" is at stake, can have any meaningful purchase in the face of a radical phenomenology like that of Martin Heidegger. Regrettably, Kendler's position in the end eclipses any intention to clarify our understanding of the relationship between "natural" and "human" science. The consequence of his article will not likely resolve the controversy he put before us, but if it does nothing more than provoke further discussion, Kendler will have provided our profession with an opportunity to understand more fully this business we call psychology. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
970.
Christopher K. Y. Leung Xinyang Wang Noah Olson 《Canadian Metallurgical Quarterly》2000,126(3):300-307
Fiber optic sensors have recently be considered for strain monitoring in concrete structures. The calibration factor of the sensor depends on the strain distribution along the fiber. When an embedded fiber is under strain, debonding may occur, causing the strain distribution and hence the calibration to change. Since interfacial properties that govern debonding are sensitive to environmental conditions, the calibration factor can also change when exposed to various environments. In this paper, a theoretical framework is developed to quantify the effect of environmental conditions on calibration shift. To illustrate the application of the theoretical approach, pullout test results on specimens subjected to various environmental conditions are first analyzed to obtain interfacial parameters. With these parameters, the effects of applied strain, environmental conditions, and fiber length on the calibration factor of two kinds of fiber optic sensors are quantified with the use of a strain transfer model. Based on the results, design guidelines to minimize calibration shift can be identified. 相似文献