全文获取类型
收费全文 | 2369篇 |
免费 | 106篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 17篇 |
综合类 | 4篇 |
化学工业 | 534篇 |
金属工艺 | 40篇 |
机械仪表 | 53篇 |
建筑科学 | 215篇 |
矿业工程 | 1篇 |
能源动力 | 114篇 |
轻工业 | 263篇 |
水利工程 | 40篇 |
石油天然气 | 5篇 |
无线电 | 149篇 |
一般工业技术 | 437篇 |
冶金工业 | 121篇 |
原子能技术 | 18篇 |
自动化技术 | 465篇 |
出版年
2023年 | 26篇 |
2022年 | 50篇 |
2021年 | 55篇 |
2020年 | 43篇 |
2019年 | 52篇 |
2018年 | 63篇 |
2017年 | 54篇 |
2016年 | 67篇 |
2015年 | 61篇 |
2014年 | 89篇 |
2013年 | 169篇 |
2012年 | 142篇 |
2011年 | 158篇 |
2010年 | 137篇 |
2009年 | 117篇 |
2008年 | 145篇 |
2007年 | 123篇 |
2006年 | 114篇 |
2005年 | 104篇 |
2004年 | 94篇 |
2003年 | 73篇 |
2002年 | 79篇 |
2001年 | 34篇 |
2000年 | 31篇 |
1999年 | 34篇 |
1998年 | 38篇 |
1997年 | 25篇 |
1996年 | 25篇 |
1995年 | 18篇 |
1994年 | 23篇 |
1993年 | 23篇 |
1992年 | 15篇 |
1991年 | 8篇 |
1990年 | 8篇 |
1989年 | 11篇 |
1988年 | 9篇 |
1987年 | 8篇 |
1984年 | 9篇 |
1983年 | 6篇 |
1982年 | 7篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1978年 | 7篇 |
1943年 | 16篇 |
1942年 | 12篇 |
1941年 | 8篇 |
1940年 | 8篇 |
1939年 | 7篇 |
1938年 | 5篇 |
1937年 | 5篇 |
排序方式: 共有2476条查询结果,搜索用时 0 毫秒
101.
Klas Engvall Henrik Kusar Krister Sjöström Lars J. Pettersson 《Topics in Catalysis》2011,54(13-15):949-959
The depletion of fossil fuel-based resources and concerns for increasing emissions of CO2 call for new ways of producing environmentally-friendly substitutes for motor fuels and chemicals. Thermo-chemical conversion of biomass and waste using gasification is a strong candidate to meet these challenges. For efficient and cost-effective application of this technique, novel solutions for hot gas cleaning are needed. This review highlights some important areas for improvement of upgrading technologies for pressurised fluidised bed gasification systems using biomass as a fuel. 相似文献
102.
Stefanie Dietmair Lars K. Nielsen Nicholas E. Timmins 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2011,86(7):905-914
Mammalian cells are the preferred host for the manufacture of a wide range of biopharmaceuticals, but production costs are high owing to low productivity. A range of rational engineering strategies have been pursued in order to increase volumetric product titres from mammalian cells, such as delaying apoptosis, manipulation of the cell cycle, and improving metabolism and protein processing. Unfortunately, outcomes from these strategies have been mixed, with few instances where significant improvements in product yield have been achieved. This article reviews and contrasts many of the engineering strategies attempted to date, highlighting the variability and context specificity in outcome. The paper argues that this is a reflection of the complexity of mammalian cells, and that a deeper understanding of the biology underpinning protein production for biotechnological purposes is required. Copyright © 2011 Society of Chemical Industry 相似文献
103.
Studies using both in vitro and in vivo techniques have repeatedly shown that endothelium-dependent vasodilation (EDV) is impaired in different forms of experimental
as well as human hypercholesterolemia. Clearly this impaired EDV can be reversed by lowering cholesterol levels by diet or
medical therapy. Competitive blocking of l-arginine, changes in nitric oxide synthase acitivity, increased release of endothelin-1, and inactivation of nitric oxide
due to superoxide ions all contribute to the impairment in EDV during dyslipidemia. The oxidation of low density lipoprotein,
with its compound lysophosphatidylcholine, plays a critical role in these events. However, data on the role of triglycerides
and fat-rich meals regarding EDV are not so consistent as data for cholesterol, although a view that the compositions of individual
fatty acids and antioxidants are of major importance is emerging. Thus, this review shows that while impaired FDV is a general
feature of hypercholesterolemia, the mechanisms involved and the therapeutic opportunities available still have to be investigated.
Furthermore, discrepancies regarding the role of triglycerides and fat content in food may be explained by divergent effects
of different fatty acids on the endothelium. 相似文献
104.
Lars Pleth Nielsen Morten Schønning Steffen V. Christensen Søren V. Hoffmann Zheshen Li Philip Hofmann Flemming Besenbacher Bjerne S. Clausen 《Catalysis Letters》2001,73(2-4):85-90
The sulfiding of Mo/Al2O3 in H2S/Ar versus in H2S/H2 has been studied by temperature-programmed sulfiding (TPS), X-ray photon electron spectroscopy (XPS), extended X-ray absorption fine structure (EXAFS), and temperature-programmed desorption of NO (NO-TPD). All the applied techniques agree on the sulfur content in the sulfided catalysts and the findings are in accord with a model for the H2S production reaction. The nucleation and growth of well-ordered MoS2 clusters are probed by XPS during sulfiding with and without the presence of hydrogen. The resulting dispersion of the MoS2 phase is evaluated on the basis of XPS, EXAFS, and NO-TPD, and is found to be highest when the sulfiding occurs in the presence of hydrogen. 相似文献
105.
106.
Janine Will Lars Schneider Dr. Jonathan Becker Jun.-Prof. Dr. Sabine Becker Andreas Miska Christopher Gawlig Prof. Dr. Siegfried Schindler 《Israel journal of chemistry》2020,60(10-11):999-1003
A new tripodal imine ligand tris(2-(propan-2-ylideneamino)ethyl)amine (imine3tren) was prepared in order to stabilize high valent iron-oxido complexes. Iron complexes were synthesized in template reactions from iron(II) salts, tris(2-aminoethyl)amine (tren) and acetone. Due to the reversibility of the imine formation, complexes with different ligands were obtained depending on the reaction conditions. Three complexes, [Fe(imine3tren)(OAc)2] ( 1 ), [Fe(imine3tren)(OAc)]OTf ( 2 ) and [(imine3tren)2Fe2(F)2](SbF6)2 ( 3 ), could be synthesized and structurally characterized. However, reactions with hydrogen peroxide, iodosobenzene or ozone did not lead to any kind of “oxygen adduct” complex that could be spectroscopically observed. 相似文献
107.
Pengfei Liu Kacper Januchta Lars R. Jensen Mathieu Bauchy Morten M. Smedskjaer 《Journal of the American Ceramic Society》2020,103(2):944-954
Lithium aluminoborate glasses have recently been found to feature high resistance to crack initiation during indentation, but suffer from relatively low hardness and chemical durability. To further understand the mechanical properties of this glass family and their correlation with the network structure, we here study the effect of adding SiO2 to a 25Li2O–20Al2O3–55B2O3 glass on the structure and mechanical properties. Addition of silica increases the average network rigidity, but meanwhile its open tetrahedral structure decreases the atomic packing density. Consequently, we only observe a minor increase in hardness and glass transition temperature, and a decrease in Poisson's ratio. The addition of SiO2, and thus removal of Al2O3 and/or B2O3, also makes the network less structurally adaptive to applied stress, since Al and B easily increase their coordination number under pressure, while this is not the case for Si under modest pressures. As such, although the silica-containing networks have more free volume, they cannot densify more during indentation, which in turn leads to an overall decrease in crack resistance upon SiO2 addition. Our work shows that, although pure silica glass has very high glass transition temperature and relatively high hardness, its addition in oxide glasses does not necessarily lead to significant increase in these properties due to the complex structural interactions in mixed network former glasses and the competitive effects of free volume and network rigidity. 相似文献
108.
109.
Aggregation‐Prone Amyloid‐β⋅CuII Species Formed on the Millisecond Timescale under Mildly Acidic Conditions 下载免费PDF全文
Prof. Dr. Jeppe T. Pedersen Christian B. Borg Thomas C. T. Michaels Dr. Tuomas P. J. Knowles Prof. Dr. Peter Faller Prof. Dr. Kaare Teilum Prof. Dr. Lars Hemmingsen 《Chembiochem : a European journal of chemical biology》2015,16(9):1293-1297
Metal ions and their interaction with the amyloid beta (Aβ) peptide might be key elements in the development of Alzheimer's disease. In this work the effect of CuII on the aggregation of Aβ is explored on a timescale from milliseconds to days, both at physiological pH and under mildly acidic conditions, by using stopped‐flow kinetic measurements (fluorescence and light‐scattering), 1H NMR relaxation and ThT fluorescence. A minimal reaction model that relates the initial CuII binding and Aβ folding with downstream aggregation is presented. We demonstrate that a highly aggregation prone Aβ ? CuII species is formed on the sub‐second timescale at mildly acidic pH. This observation might be central to the molecular origin of the known detrimental effect of acidosis in Alzheimer's disease. 相似文献
110.
One Question,Multiple Answers: Biochemical and Biophysical Screening Methods Retrieve Deviating Fragment Hit Lists 下载免费PDF全文
Dr. Johannes Schiebel Nedyalka Radeva Dr. Helene Köster Dr. Alexander Metz Timo Krotzky Dr. Maren Kuhnert Prof. Wibke E. Diederich Prof. Andreas Heine Dr. Lars Neumann Dr. Cedric Atmanene Dominique Roecklin Dr. Valérie Vivat‐Hannah Dr. Jean‐Paul Renaud Dr. Robert Meinecke Dr. Nina Schlinck Dr. Astrid Sitte Franziska Popp Dr. Markus Zeeb Prof. Gerhard Klebe 《ChemMedChem》2015,10(9):1511-1521
Fragment‐based lead discovery is gaining momentum in drug development. Typically, a hierarchical cascade of several screening techniques is consulted to identify fragment hits which are then analyzed by crystallography. Because crystal structures with bound fragments are essential for the subsequent hit‐to‐lead‐to‐drug optimization, the screening process should distinguish reliably between binders and non‐binders. We therefore investigated whether different screening methods would reveal similar collections of putative binders. First we used a biochemical assay to identify fragments that bind to endothiapepsin, a surrogate for disease‐relevant aspartic proteases. In a comprehensive screening approach, we then evaluated our 361‐entry library by using a reporter‐displacement assay, saturation‐transfer difference NMR, native mass spectrometry, thermophoresis, and a thermal shift assay. While the combined results of these screening methods retrieve 10 of the 11 crystal structures originally predicted by the biochemical assay, the mutual overlap of individual hit lists is surprisingly low, highlighting that each technique operates on different biophysical principles and conditions. 相似文献