全文获取类型
收费全文 | 22081篇 |
免费 | 1400篇 |
国内免费 | 19篇 |
专业分类
电工技术 | 366篇 |
综合类 | 54篇 |
化学工业 | 4805篇 |
金属工艺 | 639篇 |
机械仪表 | 533篇 |
建筑科学 | 970篇 |
矿业工程 | 131篇 |
能源动力 | 477篇 |
轻工业 | 2870篇 |
水利工程 | 163篇 |
石油天然气 | 53篇 |
无线电 | 1322篇 |
一般工业技术 | 5530篇 |
冶金工业 | 1899篇 |
原子能技术 | 202篇 |
自动化技术 | 3486篇 |
出版年
2023年 | 282篇 |
2022年 | 240篇 |
2021年 | 492篇 |
2020年 | 418篇 |
2019年 | 391篇 |
2018年 | 739篇 |
2017年 | 760篇 |
2016年 | 814篇 |
2015年 | 656篇 |
2014年 | 926篇 |
2013年 | 1685篇 |
2012年 | 1045篇 |
2011年 | 1240篇 |
2010年 | 1066篇 |
2009年 | 978篇 |
2008年 | 1079篇 |
2007年 | 1049篇 |
2006年 | 767篇 |
2005年 | 613篇 |
2004年 | 525篇 |
2003年 | 516篇 |
2002年 | 508篇 |
2001年 | 417篇 |
2000年 | 375篇 |
1999年 | 297篇 |
1998年 | 660篇 |
1997年 | 450篇 |
1996年 | 375篇 |
1995年 | 291篇 |
1994年 | 220篇 |
1993年 | 218篇 |
1992年 | 162篇 |
1991年 | 130篇 |
1990年 | 118篇 |
1989年 | 101篇 |
1988年 | 110篇 |
1987年 | 90篇 |
1986年 | 75篇 |
1985年 | 182篇 |
1984年 | 184篇 |
1983年 | 118篇 |
1982年 | 127篇 |
1981年 | 155篇 |
1980年 | 121篇 |
1979年 | 100篇 |
1978年 | 100篇 |
1977年 | 109篇 |
1976年 | 163篇 |
1975年 | 90篇 |
1974年 | 78篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Effect of enzymatic high temperature prehydrolysis on the subsequent cellulose hydrolysis of steam‐pretreated spruce in high solids concentration
下载免费PDF全文
![点击此处可从《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
993.
Leopold Weber Wolfgang Lenhardt Franz Möstl Gregor Götzl Julia Weilbold Heinz Reitner 《BHM Berg- und Hüttenm?nnische Monatshefte》2016,161(4):148-155
Touristic mines are by far not only of public interest. During guided tours the importance of mining and mineral resources for society can be explained in a proper way. Mineral deposits, for long time not accessible and only known from old literature can now be studied in detail by scientists. Old underground mines can be used for different purposes. With respect to Arzberg the different possibilities of utilization of old underground workings are described in detail: A touristic mine serves not only as an attraction, but also as a training centre for underground geological mapping, geochemistry and geophysics research laboratory of universities. For many years the ZAMG (Central Institute for Meteorology and Geodynamics) has been operating a seismic station, and parts of the old mine workings have been used for cheese refinery since 2006. Furthermore, the mine water is utilized for extracting geothermal energy and serves the cooling chambers. The combined use of the old mine workings by different parties permits sharing the substantial maintenance costs. 相似文献
994.
Herbert Wiggenhauser Christian Köpp Juri Timofeev Hoda Azari 《Journal of Nondestructive Evaluation》2018,37(3):67
The non-destructive assessment of cracks in concrete is a common task for which non-destructive evaluation solutions have been published. Primarily, these tests have been carried out on artificial cracks that have been created by using notches instead of natural cracks. This study evaluates a procedure designed to create reproducible and controlled cracks in concrete. The procedure is based on using expanding mortar in a series of blind holes. This is done in combination with carefully aligned reinforcement to guide the direction of the crack development. The depth of the crack is also controlled by reinforcement. Crack depth varies statistically in the range of the maximum aggregate size (16 mm) used for concrete. 相似文献
995.
Time‐dependent effects on the apparent roughness and surface free energy of different polymeric surfaces and stainless steel were studied during the biofouling process for Escherichia coli K12. The surface roughness increases during primary adhesion of E. coli on the surfaces and is later reduced as the surface between scattered bacteria is completely covered, forming a uniform biofilm. During the fouling process, the polar fraction of the surface free energy significantly increased, whereas the dispersive fraction decreased for all substrates. The attachment of E. coli and subsequent bacterial production of extracellular polymeric substances increased the polarity of the initially nonpolar polymeric surfaces to increase wettability. 相似文献
996.
997.
1,2‐Dimethyl‐3‐(5‐methylisoxazol‐3‐yldiazenyl)‐1H‐indole was obtained by coupling 3‐amino‐5‐methylisoxazole with diazotised 1,2‐dimethylindole. It was characterised by proton and carbon nuclear magentic resonance, ultraviolet–visible, infrared and Raman spectra, and the X‐ray single crystal diffraction method. On the theoretical side, the molecular geometry, chemical shifts and the fundamental vibrational frequencies were evaluated using density functional theory. Time‐dependent density functional theory was used to evaluate the electronic excitation spectra. In addition, the scaled quantum mechanical approach was used to study the total energy distributions of the vibrational modes of the molecule. The results showed that the general agreement between experimental and calculated geometric parameters, chemical shifts and λmax values are good. Excellent agreement was found between the calculated and experimental vibrational frequencies. 相似文献
998.
Tero Luukkonen Emma-Tuulia Tolonen Hanna Runtti Kimmo Kemppainen Paavo Perämäki Jaakko Rämö Ulla Lassi 《Journal of Materials Science》2017,52(16):9363-9376
Geopolymers are functional materials that can be used in various environmental applications such as adsorbents in pollutant removal from wastewaters. Metakaolin geopolymer (MK-GP) has been proven to be especially suitable for ammonium (NH4 +) removal. In this research, the optimal reagent and raw material ratios in the preparation of MK-GP in terms of NH4 + adsorption capacity were investigated. The response surface methodology based on the face-centered central composite design was used to optimize the levels of three factors: the amounts of hydroxide, silicate, and metakaolin. In addition, the effect of Na or K as the charge-balancing cation was studied. Empirical models were fitted to the experimental data using multiple linear regression. The significance of the models was confirmed by means of analysis of variance. Optimal NH4 + removal efficiency was achieved when the amounts of hydroxide and silicate were maximized, the amount of metakaolin was minimized, and Na-based reagents were used. These trends are most likely a result of optimized conversion of metakaolin into MK-GP. 相似文献
999.
At the macroscopic scale, concrete appears as a composite made of a cement paste matrix with embedded aggregates. The latter are covered by interfacial transition zones (ITZs) of reduced stiffness and strength. Cracking in the ITZs is probably the key to the nonlinear stress–strain behavior in the prepeak regime. For a deeper understanding of this effect triggered by tensile microstress peaks, we here employ and extend the framework of continuum micromechanics, as to develop analytical solutions relating the macroscopic stresses acting on a piece of concrete, to microtractions at the aggregates' surfaces and to three‐dimensional stress states within the ITZs. In the latter context, a new aggregate‐to‐ITZ stress concentration tensor is derived based on the separation‐of‐scale principle, which implies that ITZs may be modeled as two‐dimensional interfaces at the concrete scale, but as three‐dimensional bulk phases at the scale of a few micrometers. Microtensile peaks occur both under uniaxial macroscopic tension and compression. To describe the respective microtraction and microstress fields, it is suitable to define aggregate's “poles” and “equator” by an “axis” through the aggregate center, directed in the uniaxial macroscopic loading direction. Accordingly, tensile microtraction peaks, induced by macro‐tension and macro‐compression, respectively, occur at the “poles” and at the “equator”, respectively. The largest tensile ITZ‐microstresses occur at an offset of about π/8 from the “poles” and the “equator”, respectively. These fields of microtractions and ITZ microstresses are prerequisites for upscaling ITZ‐related strength to the macroscopic concrete level, as presented in the companion paper (Part II). 相似文献
1000.
Zinc oxide has recently been suggested to be a potential material for hot metal desulfurization. The present work was carried out to examine whether ZnO could help the remaining blast furnace (BF) slag to capture sulfur. For this purpose, slags prepared with relatively high ZnO content was equilibrated with either liquid silver or liquid copper under controlled oxygen potential at 1773 K. It was found that most of the ZnO escaped during the experiment, indicating thereby that ZnO could not increase the desulfurization potential of the BF slag in the case of hot metal. The experimental data were used to evaluate the sulfide capacities of the studied slags. In some of the slags equilibrated with silver, the MgO activities were evaluated. 相似文献