全文获取类型
收费全文 | 168211篇 |
免费 | 1321篇 |
国内免费 | 191篇 |
专业分类
电工技术 | 2552篇 |
综合类 | 119篇 |
化学工业 | 26463篇 |
金属工艺 | 9471篇 |
机械仪表 | 5715篇 |
建筑科学 | 3008篇 |
矿业工程 | 1887篇 |
能源动力 | 2703篇 |
轻工业 | 8815篇 |
水利工程 | 2729篇 |
石油天然气 | 8692篇 |
武器工业 | 12篇 |
无线电 | 14487篇 |
一般工业技术 | 38249篇 |
冶金工业 | 27793篇 |
原子能技术 | 6933篇 |
自动化技术 | 10095篇 |
出版年
2018年 | 2977篇 |
2017年 | 3091篇 |
2016年 | 3344篇 |
2015年 | 1672篇 |
2014年 | 2954篇 |
2013年 | 6338篇 |
2012年 | 4311篇 |
2011年 | 5397篇 |
2010年 | 4420篇 |
2009年 | 4894篇 |
2008年 | 4940篇 |
2007年 | 4868篇 |
2006年 | 4140篇 |
2005年 | 3819篇 |
2004年 | 3634篇 |
2003年 | 3520篇 |
2002年 | 3450篇 |
2001年 | 3463篇 |
2000年 | 3361篇 |
1999年 | 3212篇 |
1998年 | 7018篇 |
1997年 | 5148篇 |
1996年 | 3821篇 |
1995年 | 2916篇 |
1994年 | 2593篇 |
1993年 | 2720篇 |
1992年 | 2254篇 |
1991年 | 2304篇 |
1990年 | 2409篇 |
1989年 | 2315篇 |
1988年 | 2313篇 |
1987年 | 2190篇 |
1986年 | 2246篇 |
1985年 | 2292篇 |
1984年 | 2206篇 |
1983年 | 2135篇 |
1982年 | 1980篇 |
1981年 | 2193篇 |
1980年 | 2053篇 |
1979年 | 2269篇 |
1978年 | 2431篇 |
1977年 | 2430篇 |
1976年 | 3095篇 |
1975年 | 2244篇 |
1974年 | 2307篇 |
1973年 | 2342篇 |
1972年 | 2155篇 |
1971年 | 1911篇 |
1970年 | 1701篇 |
1969年 | 1632篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
921.
Y. Miyamoto Y. Kubo N. Ono M. Hashimoto T. Takahashi I. Ito F. Arezzo P. Gimondo 《Thin solid films》1995,270(1-2):253-259
A new coil-coating pilot plant, capable of utilizing ion plating, sputtering and plasma-assisted chemical vapor deposition (PACVD) processes, independently or in series, was developed and optimum conditions for TiN, TiC, AlxOy, SiOx and Cr coating were established. This paper is mostly concerned with the results of characterization (conducted in parallel by the authors′ two institutions) of TiN films deposited by ion plating or sputtering onto type-304 stainless steel strips. In particular, the dependence of the basic properties such as chemical composition, structure, adhesion, and color on the coating process are discussed with respect to anti-corrosion, anti-wear, and decorative applications. TiN coatings with a very attractive gold coloration were obtained; they performed well in wear testing, but did not show satisfactory corrosion resistance. However, it was found that the latter can be improved significantly by depositing a SiOx, top layer by PACVD above the TiN coating. Thus the in-line dry coating processes are capable of producing highly functional steel surfaces with decorative color and high corrosion resistance. 相似文献
922.
L. P. Podenok L. I. Sharakhovskii V. D. Shimanovich O. I. Yas’ko 《Journal of Engineering Physics and Thermophysics》1997,70(1):95-99
The influence of heat transfer processes in arc discharges on the development of thermal instability is considered. A substantial
dependence of the process of destabilization on the plasma properties is shown by the example of argon and helium arcs.
Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 70, No. 1, pp. 93–98, January–February, 1997. 相似文献
923.
M. Grana A. D'Anjou F.X. Albizuri M. Hernandez F.J. Torrealdea A. de la Hera A.I. Gonzalez 《Applied Intelligence》1997,7(4):287-303
This work reports the results obtained with the application of High Order Boltzmann Machines without hidden units to construct classifiers for some problems that represent different learning paradigms. The Boltzmann Machine weight updating algorithm remains the same even when some of the units can take values in a discrete set or in a continuous interval. The absence of hidden units and the restriction to classification problems allows for the estimation of the connection statistics, without the computational cost involved in the application of simulated annealing. In this setting, the learning process can be sped up several orders of magnitude with no appreciable loss of quality of the results obtained. 相似文献
924.
N Schr?der A de Mattos-Dutra M Sampaio de Freitas CS Foga?a Lisboa AC Zilles R Pessoa-Pureur I Izquierdo 《Canadian Metallurgical Quarterly》1997,749(2):275-282
In the homodimeric hemoglobin from Scapharca, HbI, functional communication between the two heme groups is based on their direct structural linkage across the subunit interface through the heme propionates. The heme-protein interactions have been altered in deutero- and meso-HbI by substituting the vinyl groups at positions 2 and 4 of protoheme with hydrogen and ethyl groups, respectively. In meso-HbI the introduction of the ethyl groups in the heme pocket induces significant alterations in the conformation of the heme peripheral substituents, including the propionates, and in the structure of bound CO, as revealed by the resonance Raman spectra. The functional counterpart of these structural changes is the loss of cooperativity in carbon monoxide binding and in the rate of oxygen dissociation. Oxygen pulse and flash photolysis experiments indicate that meso-HbI is locked in the liganded conformation. It is postulated that the ethyl groups, which occupy a larger volume than vinyl ones, impair the ligand-linked movement of the heme relative to its pocket and in turn the expression of cooperativity. In deutero-HbI structural alterations have not been monitored. Functionally, cooperativity in the CO binding kinetics is increased as if hydrogen atoms at positions 2 and 4 permitted more marked movements of the heme than in the native protein. 相似文献
925.
E Kumazawa K Hirotani SC Burford K Kawagoe T Miwa I Mitsui A Ejima 《Canadian Metallurgical Quarterly》1997,45(9):1470-1474
Novel benzophenone derivatives were synthesized and screened for cytotoxic and antitumor activity. Friedel-Crafts condensation was employed to construct the benzophenone skeleton. Among the compounds synthesized, morpholino and thiomorpholino benzophenones 3a-d exhibited potent cytotoxic activity against P388 murine leukemia and PC-6 human lung carcinoma cells in vitro, and compounds 3a, 3c, and 3j, when administered intraperitoneally, showed significant antitumor activity against the malignant ascites caused by intraperitoneal inoculation of P388 cells in mice. 相似文献
926.
A Lubics D Regl?di S Slezák M Szelier I Lengvári 《Canadian Metallurgical Quarterly》1997,99(4):459-467
In addition to receptor-type pinealocytes, the mammalian pineal organ contains small and large neurons and ependymal/glial cells as well. Axons of pinealocytes form synaptic ribbon-containing axo-dendritic synapses on large secondary pineal neurons and/or terminate as neurohormonal endings on the basal lamina of the vascular surface of the organ. The small pineal neurons were found to be gamma-aminobutyric acid (GABA)-immunoreactive, while large secondary neurons and pinealocytes contained immunoreactive amino acids (glutamate and aspartate). Glutamate accumulated presynaptically in pinealocytic axon terminals on large secondary neurons and in the axons of these neurons. Glutamate immunoreactive axons of pineal neurons were traced via the pineal tract to the habenular nucleus. Axons containing granular vesicles and coming from extrapineal perikarya are glutamate immunoreactive as well. Aspartate and GABA are also present in some of the myelinated axons, supposedly pinealopetal in the pineal tract. 相似文献
927.
S Delorme A Dietz V Rudat I Zuna ML Bahner G van Kaick 《Canadian Metallurgical Quarterly》1997,23(9):1311-1317
This summary of the practice parameters describes the assessment, differential diagnosis, and treatment of children, adolescents, and adults who present with symptoms of attention-deficit/hyperactivity disorder. The rationales for specific recommendations are based on a review of the scientific literature and clinical consensus which is contained in the complete document. Assessment includes clinical interviews with the child and parents and standardized rating scales from parent and teachers. Testing of intelligence and academic achievement is usually required. Comorbidity is common. The cornerstones of treatment are support and education of parents, appropriate school placement, and psychopharmacology. The primary medications are psychostimulants, but antidepressants and alpha-adrenergic agonists are used in special circumstances. Other treatments such as behavior modification, school consultation, family therapy, and group therapy address remaining symptoms. 相似文献
928.
929.
The spatial distribution measurements of laser radiation, scattered in the laser spark, were accomplished for various laser radiation wavelengths (1060, 530, 353, and 265 nm) and various pressures of the gas (air at 10-760 mm Hg). The interference structure of the laser light scattering cone behind the laser spark was observed for the first time. It is proposed to consider the observed structure as a result of interference of the laser radiation, scattered by two or more self-focusing centers in laser spark air plasma. The experimental dependence of the maximal angle of the light scattering on the gas pressure and on the laser radiation wavelength was obtained 相似文献
930.
A. I. Ponomarev V. I. Tsidilkovski K. R. Krylov T. B. Charikova A. A. Lakhtin L. I. Leonyuk 《Journal of Superconductivity and Novel Magnetism》1996,9(1):27-32
The anisotropy of the resistivity and thermoelectric power (TEP)S of Nd1.85Ce0.15CuO4?δ single crystal (T c =17 K) has been investigated. In the temperature rangeT c <T<300 K the ratioρ c/ρab≈104 and the dependencesρ ab (T) andρ c (T) change from quadratic to linear atT~200 K. The dependencesS ab (T) andS c (T) reach a maximum atT>T c and then decrease almost linearly with increasing temperature, changing sign from positive to negative nearT~ 150 K. The features of the resistivity and TEP temperature dependences (the lawρ∝T 2 changing toρ∝T, the change in the sign of S with temperature, and the low TEP anisotropy at largeρ anisotropy) have been interpreted in the framework of the narrow-band model. 相似文献