全文获取类型
收费全文 | 4723篇 |
免费 | 128篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 58篇 |
综合类 | 11篇 |
化学工业 | 1091篇 |
金属工艺 | 143篇 |
机械仪表 | 96篇 |
建筑科学 | 261篇 |
矿业工程 | 19篇 |
能源动力 | 118篇 |
轻工业 | 634篇 |
水利工程 | 20篇 |
石油天然气 | 5篇 |
无线电 | 419篇 |
一般工业技术 | 828篇 |
冶金工业 | 715篇 |
原子能技术 | 64篇 |
自动化技术 | 374篇 |
出版年
2021年 | 45篇 |
2020年 | 44篇 |
2019年 | 56篇 |
2018年 | 54篇 |
2017年 | 59篇 |
2016年 | 99篇 |
2015年 | 85篇 |
2014年 | 101篇 |
2013年 | 167篇 |
2012年 | 200篇 |
2011年 | 196篇 |
2010年 | 144篇 |
2009年 | 163篇 |
2008年 | 170篇 |
2007年 | 161篇 |
2006年 | 164篇 |
2005年 | 131篇 |
2004年 | 130篇 |
2003年 | 100篇 |
2002年 | 109篇 |
2001年 | 85篇 |
2000年 | 75篇 |
1999年 | 92篇 |
1998年 | 213篇 |
1997年 | 146篇 |
1996年 | 96篇 |
1995年 | 106篇 |
1994年 | 94篇 |
1993年 | 71篇 |
1992年 | 71篇 |
1991年 | 58篇 |
1990年 | 58篇 |
1989年 | 60篇 |
1988年 | 60篇 |
1987年 | 75篇 |
1986年 | 63篇 |
1985年 | 61篇 |
1984年 | 63篇 |
1983年 | 58篇 |
1982年 | 52篇 |
1981年 | 58篇 |
1980年 | 49篇 |
1979年 | 55篇 |
1978年 | 51篇 |
1977年 | 53篇 |
1976年 | 70篇 |
1975年 | 32篇 |
1974年 | 32篇 |
1973年 | 40篇 |
1971年 | 38篇 |
排序方式: 共有4856条查询结果,搜索用时 15 毫秒
121.
122.
Dr. Sven Eck Werner Ecker Thomas Wlanis Hans-Peter Gänser Reinhold Ebner 《BHM Berg- und Hüttenm?nnische Monatshefte》2014,159(9):371-374
Through process modelling of surface densified gears produced by powder metallurgy (PM) was established by coupling the modelling of the manufacturing processes surface densification, carburization, and heat treatment. The complete model allows the prediction of the local microstructure and hardness in the gear as well as the appearance and direction of residual stresses in the final part. The structural integrity of the part is governed, on the one hand, by the local material properties and residual stresses and, on the other hand, by the load stresses calculated for typical operating conditions. A simplified hardness dependent Haigh diagram was used to calculate the maximum allowable cyclic stresses for the gear tooth and to derive a local utilization ratio as target entity for optimization of the individual steps of the production chain. 相似文献
123.
124.
125.
Dr. Sebastian Meier Dr. Natalia Solodovnikova Dr. Pernille R. Jensen Prof. Jürgen Wendland 《Chembiochem : a European journal of chemical biology》2012,13(15):2265-2269
Detecting the molecular targets of xenobiotic substances in vivo poses a considerable analytical challenge. Here, we describe the use of an NMR‐based tracer methodology for the instantaneous in vivo observation of sulfur(IV) action on cellular metabolism. Specifically, we find that glycolytic flux is directed towards sulfite adducts of dihydroxyacetone phosphate and pyruvate as off‐pathway intermediates that obstruct glycolytic flux. In particular, the pyruvate–sulfite association hinders the formation of downstream metabolites. The apparent in vivo association constant of pyruvate and sulfite agrees with the apparent inhibition constant of CO2 formation, thus supporting the importance of pyruvate interception in disturbing central metabolism and inhibiting NAD regeneration. 相似文献
126.
127.
与以往相比,马克斯·杜德勒的建筑似乎更直接地从源头接近目标。任何可能妨碍材料与建筑内在联系的部分都被排除在外—这一点在柏林的洪堡大学新图书馆格林兄弟中心可以明显见到。竖向支撑以一种非常紧密的节奏顺次排列,其间隔密度远高于正常要求。没有为附加装饰或者表面肌理的翻新留下任何余地。结构忠实于自身,形成了自己的"装饰",既不能增也不能减。它深深地扎根于它所建造的场地,并与背景相一致,这种背景是与"准确(分布)"联系在一起的,莱昂·巴蒂斯塔·阿尔伯蒂将其解释为一种先天判断能力的结果。从这个意义来讲,杜德勒的建筑是直接而准确的。他避 相似文献
128.
Dr. Tessa Lühmann Valerie Spieler Dr. Vera Werner Dr. Marie‐Gabrielle Ludwig Dr. Juliane Fiebig Prof. Dr. Thomas D. Mueller Prof. Dr. Dr. Lorenz Meinel 《Chembiochem : a European journal of chemical biology》2016,17(22):2123-2128
Driving macrophage (M?) polarization into the M2 phenotype provides potential against inflammatory diseases. Interleukin‐4 (IL‐4) promotes polarization into the M2‐M? phenotype, but its systemic use is constrained by dose‐limiting toxicity. Consequently, we developed IL‐4‐decorated surfaces aiming at sustained and localized activity. IL‐4 muteins were generated by genetic code expansion; Lys42 was replaced by unnatural amino acids (uAAs). Both muteins showed cell‐stimulation ability and binding affinity to IL4Rα similar to those of wt‐IL‐4. Copper‐catalyzed (CuAAC) and copper‐free strain‐promoted (SPAAC) 1,3‐dipolar azide–alkyne cycloadditions were used to site‐selectively anchor IL‐4 to agarose surfaces. These surfaces had sustained IL‐4 activity, as demonstrated by TF‐1 cell proliferation and M2, but not M1, polarization of M‐CSF‐generated human M?. The approach provides a blueprint for the engineering of cytokine‐activated surfaces profiled for sustained and spatially controlled activity. 相似文献
129.
Wolfram Witte Daniel Abou‐Ras Karsten Albe Gottfried H. Bauer Frank Bertram Christian Boit Rudolf Brüggemann Jürgen Christen Jens Dietrich Axel Eicke Dimitrios Hariskos Matthias Maiberg Roland Mainz Max Meessen Mathias Müller Oliver Neumann Thomas Orgis Stefan Paetel Johan Pohl Humberto Rodriguez‐Alvarez Roland Scheer Hans‐Werner Schock Thomas Unold Alfons Weber Michael Powalla 《Progress in Photovoltaics: Research and Applications》2015,23(6):717-733
The gallium gradient in Cu(In,Ga)Se2 (CIGS) layers, which forms during the two industrially relevant deposition routes, the sequential and co‐evaporation processes, plays a key role in the device performance of CIGS thin‐film modules. In this contribution, we present a comprehensive study on the formation, nature, and consequences of gallium gradients in CIGS solar cells. The formation of gallium gradients is analyzed in real time during a rapid selenization process by in situ X‐ray measurements. In addition, the gallium grading of a CIGS layer grown with an in‐line co‐evaporation process is analyzed by means of depth profiling with mass spectrometry. This gallium gradient of a real solar cell served as input data for device simulations. Depth‐dependent occurrence of lateral inhomogeneities on the µm scale in CIGS deposited by the co‐evaporation process was investigated by highly spatially resolved luminescence measurements on etched CIGS samples, which revealed a dependence of the optical bandgap, the quasi‐Fermi level splitting, transition levels, and the vertical gallium gradient. Transmission electron microscopy analyses of CIGS cross‐sections point to a difference in gallium content in the near surface region of neighboring grains. Migration barriers for a copper‐vacancy‐mediated indium and gallium diffusion in CuInSe2 and CuGaSe2 were calculated using density functional theory. The migration barrier for the InCu antisite in CuGaSe2 is significantly lower compared with the GaCu antisite in CuInSe2, which is in accordance with the experimentally observed Ga gradients in CIGS layers grown by co‐evaporation and selenization processes. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
130.
Roland Mainz Alfons Weber Humberto Rodriguez‐Alvarez Sergiu Levcenko Manuela Klaus Paul Pistor Reiner Klenk Hans‐Werner Schock 《Progress in Photovoltaics: Research and Applications》2015,23(9):1131-1143
Ga segregation at the backside of Cu(In,Ga)Se2 solar cell absorbers is a commonly observed phenomenon for a large variety of sequential fabrication processes. Here, we investigate the correlation between Se incorporation, phase formation and Ga segregation during fast selenisation of Cu–In–Ga precursor films in elemental selenium vapour. Se incorporation and phase formation are analysed by real‐time synchrotron‐based X‐ray diffraction and fluorescence analysis. Correlations between phase formation and depth distributions are gained by interrupting the process at several points and by subsequent ex situ cross‐sectional electron microscopy and Raman spectroscopy. The presented results reveal that the main share of Se incorporation takes place within a few seconds during formation of In–Se at the top part of the film, accompanied by outdiffusion of In out of a ternary Cu–In–Ga phase. Surprisingly, CuInSe2 starts to form at the surface on top of the In–Se layer, leading to an intermediate double graded Cu depth distribution. The remaining Ga‐rich metal phase at the back is finally selenised by indiffusion of Se. On the basis of a proposed growth model, we discuss possible strategies and limitations for the avoidance of Ga segregation during fast selenisation of metallic precursors. Solar cells made from samples selenised with a total annealing time of 6.5 min reached conversion efficiencies of up to 14.2 % (total area, without anti‐reflective coating). The evolution of the Cu(In,Ga)Se2 diffraction signals reveals that the minimum process time for high‐quality Cu(In,Ga)Se2 absorbers is limited by cation ordering rather than Se incorporation. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献