全文获取类型
收费全文 | 75145篇 |
免费 | 803篇 |
国内免费 | 695篇 |
专业分类
电工技术 | 1467篇 |
综合类 | 47篇 |
化学工业 | 11225篇 |
金属工艺 | 3479篇 |
机械仪表 | 2639篇 |
建筑科学 | 1645篇 |
矿业工程 | 503篇 |
能源动力 | 1865篇 |
轻工业 | 6404篇 |
水利工程 | 846篇 |
石油天然气 | 2306篇 |
武器工业 | 41篇 |
无线电 | 7233篇 |
一般工业技术 | 16522篇 |
冶金工业 | 12544篇 |
原子能技术 | 2643篇 |
自动化技术 | 5234篇 |
出版年
2022年 | 582篇 |
2021年 | 914篇 |
2020年 | 696篇 |
2019年 | 783篇 |
2018年 | 1561篇 |
2017年 | 1570篇 |
2016年 | 1769篇 |
2015年 | 948篇 |
2014年 | 1570篇 |
2013年 | 3575篇 |
2012年 | 2368篇 |
2011年 | 2835篇 |
2010年 | 2384篇 |
2009年 | 2655篇 |
2008年 | 2628篇 |
2007年 | 2563篇 |
2006年 | 2197篇 |
2005年 | 1928篇 |
2004年 | 1843篇 |
2003年 | 1799篇 |
2002年 | 1715篇 |
2001年 | 1679篇 |
2000年 | 1676篇 |
1999年 | 1575篇 |
1998年 | 3721篇 |
1997年 | 2625篇 |
1996年 | 1955篇 |
1995年 | 1544篇 |
1994年 | 1339篇 |
1993年 | 1364篇 |
1992年 | 1002篇 |
1991年 | 1055篇 |
1990年 | 1077篇 |
1989年 | 1055篇 |
1988年 | 944篇 |
1987年 | 879篇 |
1986年 | 882篇 |
1985年 | 939篇 |
1984年 | 780篇 |
1983年 | 770篇 |
1982年 | 680篇 |
1981年 | 693篇 |
1980年 | 665篇 |
1979年 | 646篇 |
1978年 | 620篇 |
1977年 | 776篇 |
1976年 | 938篇 |
1975年 | 582篇 |
1974年 | 551篇 |
1973年 | 544篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Stakheev A. Yu. Gabrielsson P. Gekas I. Teleguina N. S. Bragina G. O. Tolkachev N. N. Baeva G. N. 《Topics in Catalysis》2007,42(1-4):143-147
Pt/Al2O3 and Pt/BaO/Al2O3 catalysts (1 wt% Pt, 10 wt%BaO) were sulfated under conditions simulating a real NSR catalyst operation. Comparative TPR
and XPS studies of sulfur removal from Pt/Al2O3 and Pt/BaO/Al2O3 catalysts indicate that the sulfur removal from Al2O3 surface precedes reductive decomposition of BaSO4 (250–400 °C). Barium sulfate decomposition started with further increase in desulfation temperature at the point of surface
atomic ratio Ba:S = 1 (~450o). Simultaneously, an intensive formation of sulfide species on the catalyst surface was observed. Thermodynamic analysis
of the desulfation process allows us to hypothesize that barium sulfide formation may hinder sulfur removal under reducing
conditions. 相似文献
992.
993.
994.
Thermal behaviour of starch-graft-polyacrylamide (S-g-PAM) copolymers was evaluated. Grafting of polyacrylamide onto starch lowers the initial decomposition temperature. However, the over-all stability as assessed by the shape of thermogravimetric curve and integral procedural decomposition temperature increased with an increase in % graft-on. 相似文献
995.
Effect of sodium monofluorophosphate treatment on microstructure and frost salt scaling durability of slag cement paste 总被引:1,自引:0,他引:1
Sodium-monofluorophosphate (Na-MFP) is currently in use as a surface applied corrosion inhibitor in the concrete industry. Its basic mechanism is to protect the passive layer of the reinforcement steel against disruption due to carbonation. Carbonation is known as the most detrimental environmental effect on blast furnace slag cement (BFSC) concrete with respect to frost salt scaling. In this paper the effect of Na-MFP on the microstructure and frost salt scaling resistance of carbonated BFSC paste is presented. The results of electron microscopy, mercury intrusion porosimetry (MIP) and X-ray diffraction (XRD) are discussed. It is found that the treatment modifies the microstructure and improves the resistance of carbonated BFSC paste against frost salt attack. 相似文献
996.
S. Multsch A. S. Alquwaizany O. A. Alharbi M. Pahlow H.-G. Frede L. Breuer 《国际水资源开发杂志》2017,33(2):292-309
Agriculture policy changes in Saudi Arabia are investigated by water footprint (WF) assessment. WF is calculated with the model SPARE:WATER for 3758 irrigated sites. The WF of agriculture areas (WFarea, km3 yr?1) has decreased (–17%) since the year 2000 to 13.84 km3 yr?1 (2011), which is mainly caused by the reduction of cropland by –33%. Nevertheless, water consumption per field has increased about 16%, which can be attributed to the cultivation of fodder crops (+12%). A scenario analysis revealed that a shifting cropping pattern towards less fodder crops reduces WFarea by –15%, and implementing improved irrigation technology leads to a combined reduction of up to 32% 相似文献
997.
K. A. Malyshevskaya O. P. Laletina N. V. Polpur L. N. Natural'nova 《Fibre Chemistry》1987,19(2):95-97
Conclusions The effect of salts of alkaline earth metals and iron on the physico-chemical indices of viscose — viscosity, ripeness, and filterability — has been investigated.In amounts which exceed the content allowed by the All-Union State Standard in viscose by a factor of 3–4, calcium and magnesium ions do not cause a significant impairment in the physico-chemical indices of the viscose.Even at a content of 28 mg/liter, the presence of trivalent iron salts in a viscose causes a sharp impairment in its filterability, especially on prolonged ripening.Strict control of the trivalent iron content of viscose during the process of preparing it for spinning is necessary.Siberian Technological Institute. Translated from Kimicheskie Volokna, No. 2, pp. 17–18, March–April, 1987. 相似文献
998.
O.K. Buros Ph.D. 《Desalination》1979,30(1):595-603
Care must be exercised, in predicting operating costs for membrane desalination systems for electricity, labor, chemicals, etc. The assumptions made in establishing unit costs can greatly affect the predicted operating cost and hence the ultimate investment decision. The use of data estimating the quantities of chemicals, power, etc., expected to be used per unit of production can assist in predicting costs, as then site-specific cost data can be used. The fact that 0.2 pounds of acid per kgal of permeate is required in a Florida RO plant is more useful for predicting operating costs of an RO plant on the Island of Anegata than is the fact that acid costs at the Florida plant are $0.03/kgal of water produced. Data based on units rather than costs are presented for seven RO facilities and one ED facility in this paper for use in this type of analysis. 相似文献
999.
O.I. Konkov E.I. Terukov I.N. Trapeznikova V.E. Chelnokov 《Diamond and Related Materials》1994,3(11-12)
The temperature dependence of the electron drift mobility in glow-discharged undoped hydrogenated amorphous silicon, carbon and silicon carbide films with stoichiometric compositional (a-Si0.5C0.5:H) has been measured by the time-of-flight method. All films displayed the same behaviour of the transient current and dispersion parameters, which can be explained by assuming a gaussian distribution of tail states near the conduction band. The results obtained results corroborated the common nature and degree of disorder of the conduction band tail in all four-coordinated amorphous semiconductors. 相似文献
1000.
Conclusions Heat treatment of the resin-bonded refractories in an atmosphere consisting of the products of sublimation and decomposition of the binder leads to a significant improvement in the properties of the specimens (in particular, in the coked condition). The increase in the content of the residual carbon, the mechanical strength of the specimens, and their hydration resistance are determined by the heat treatment temperature. The highest levels of the physical and the technological properties are obtained after heat treating the specimens in the 400–600°C range. In this case, the most significant effect is observed in the lime-periclase refractories and the minimum effect is obtained in the resin-periclase refractories.The increased hydration resistance of the resin-bonded refractories containing free calcium oxide (the lime-periclase and the periclase-lime refractories) owes mainly to fixing up of CaO during the heat treatment process and to the formation of the protective calcium carbonate films at the surface of the fired dolomite grains.Translated from Ogneupory, No. 2, pp. 10–13, February, 1992. 相似文献