全文获取类型
收费全文 | 1017篇 |
免费 | 32篇 |
专业分类
电工技术 | 27篇 |
综合类 | 1篇 |
化学工业 | 262篇 |
金属工艺 | 14篇 |
机械仪表 | 23篇 |
建筑科学 | 60篇 |
矿业工程 | 1篇 |
能源动力 | 23篇 |
轻工业 | 153篇 |
水利工程 | 1篇 |
石油天然气 | 3篇 |
无线电 | 65篇 |
一般工业技术 | 168篇 |
冶金工业 | 94篇 |
原子能技术 | 6篇 |
自动化技术 | 148篇 |
出版年
2023年 | 4篇 |
2022年 | 16篇 |
2021年 | 22篇 |
2020年 | 9篇 |
2019年 | 11篇 |
2018年 | 20篇 |
2017年 | 28篇 |
2016年 | 19篇 |
2015年 | 16篇 |
2014年 | 16篇 |
2013年 | 24篇 |
2012年 | 37篇 |
2011年 | 64篇 |
2010年 | 51篇 |
2009年 | 46篇 |
2008年 | 55篇 |
2007年 | 64篇 |
2006年 | 33篇 |
2005年 | 45篇 |
2004年 | 28篇 |
2003年 | 30篇 |
2002年 | 24篇 |
2001年 | 20篇 |
2000年 | 30篇 |
1999年 | 18篇 |
1998年 | 41篇 |
1997年 | 24篇 |
1996年 | 18篇 |
1995年 | 28篇 |
1994年 | 22篇 |
1993年 | 14篇 |
1992年 | 15篇 |
1991年 | 6篇 |
1990年 | 12篇 |
1989年 | 14篇 |
1988年 | 10篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 8篇 |
1983年 | 10篇 |
1982年 | 8篇 |
1981年 | 4篇 |
1980年 | 10篇 |
1978年 | 5篇 |
1976年 | 8篇 |
1974年 | 4篇 |
1973年 | 4篇 |
1925年 | 4篇 |
1904年 | 3篇 |
排序方式: 共有1049条查询结果,搜索用时 15 毫秒
61.
Tapas Debnath Subrata Chandra Roy Claus H. Rüscher Altaf Hussain 《Journal of Materials Science》2009,44(1):179-185
Needle-shaped crystals of sizes up to 5 μm × 5 μm × 40 μm of nominal composition K
x
Nb
y
W1−y
O3 were synthesized by solid state method at 800 °C using appropriate amount of WO3, WO2, Nb2O5, and K2WO4. The samples were characterized with XRD, SEM, microprobe analysis, optical spectroscopy, and Raman spectroscopy. The XRD
patterns of the samples show single phase of tetragonal tungsten bronze (TTB) type (P4/mbm, No. 127) up to y = 0.07. Structure refinements reveal an increase in cell parameter with increasing nominal niobium content within the TTB
phase. The elemental compositions of the crystals determined by electron microprobe analysis also show an increase in Nb content
with increasing y. With increasing Nb content the reflectivity minimum in the near infrared spectral range shifts towards lower wavenumber
indicating the effect of decreasing carrier concentration. Pyrochlore type phase (KNbWO6) is obtained as a second phase when nominal composition y > 0.07. 相似文献
62.
Hertkorn N Claus H Schmitt-Kopplin P Perdue EM Filip Z 《Environmental science & technology》2002,36(20):4334-4345
Aquatic humic substances (HS) from a bog lake water, a riverwater, and a groundwater were isolated after enrichment on XAD 8 columns and added to a Czapek-Dox nutrient broth which was used either in full strength or without glucose and/or NaNO3. The individual flasks were inoculated with natural microbial populations of corresponding water samples or with a Pseudomonas fluorescens strain isolated from groundwater. The presence of HS resulted in an increase of bacterial numbers in nearly all cultures incubated for 3 weeks at 25 degrees C on a shaker. HS reisolated from cultures without glucose or NaNO3 showed no or only minor quantitative differences as compared to those from sterile controls. In full strength nutrient broth up to 27% of HS were utilized. Data obtained by spectroscopic methods (UV/vis/FTIR) and elemental analysis indicated a decrease in particle size and a loss in aromaticity and aliphatic carbon in HS reisolated from the microbial cultures. Simultaneously an increase in the N content of HS was observed, which probably originated from some constituents of microbial biomass such as proteins and amino sugars. The NMR data also documented that significant transformations of HS occurred in the individual microbial cultures. After incubation, increased amounts of aromatic acids were detected in some liquid media and residual HS by GC/MS or capillary electrophoresis. 1H NMR spectroscopy was less effective in indicating structural differences in the HS than 13C NMR but revealed considerable detail of the microbial degradation of riverine HS, when limited sample was available. The newly developed NMR increment analysis provided substantial detail of aromatic structures in a microbially altered HS. The microbial degradation of HS strongly depended on the composition of the HS, the species selection of the microorganisms, and to a lesser extent on the culture conditions. For any series of identical inoculum and HS, full broth media initiated the most extensive alteration of HS. 相似文献
63.
Immobilised DNA-oligo layers are scientifically and technologically appealing for a wide range of sensor applications such as DNA chips. Using microcantilever-based sensors with integrated readout, we demonstrate in situ quantitative studies of surface-stress formation during self-assembly of a 25-mer thiol-modified DNA-oligo layer. The self-assembly induces a surface-stress change, which closely follows Langmuir adsorption model. The adsorption results in compressive surface-stress formation, which might be due to intermolecular repulsive forces in the oligo layer. The rate constant of the adsorption depends on the concentration of the oligo solution. Based on the calculated rate constants a surface free energy of the thiol-modified DNA-oligo adsorption on gold is found to be -32.4 kJ mol(-1). The adsorption experiments also indicate that first a single layer of DNA-oligos is assembled on the gold surface after which a significant unspecific adsorption takes place on top of the first DNA-oligo layer. The cantilever-based sensor principle has a wide range of applications in real-time local monitoring of chemical and biological interactions as well as in the detection of specific DNA sequences, proteins and particles. 相似文献
64.
Prof. Dr. Hans Ulrich Buhl Dr. Bernd Heinrich Prof. Dr. Peter Loos Prof. Dr. Ulrich Frank Visiting Prof. Daniel L. Moody PhD Prof. Jeffrey Parsons PhD Prof. Dr. Michael Rosemann Prof. Dr. Elmar J. Sinz Prof. Ron Weber PhD Achim Kindler Dr. Prof. Dr. Claus Rautenstrauch Dipl.-Wirt.-Inf. Peter Fettke 《WIRTSCHAFTSINFORMATIK》2005,47(2):152-161
65.
Huiqing Li Simon Thompson Claus Reinke 《Electronic Notes in Theoretical Computer Science》2005,141(4):29
We demonstrate the Haskell Refactorer, HaRe, both as an example of a fully-functional tool for a complete (functional) programming language, and to show the API which HaRe provides for building source-level program transformations for Haskell. We comment on the challenges presented by the construction of this and similar tools for language frameworks and processors. 相似文献
66.
This study investigated the representations that readers construct for narratives describing a sequence of events. Participants read narratives describing 4 successive events in chronological order (Event 1, Event 2, Event 3, Event 4 [E1, E2, E3, E4] Experiment 1) or in nonchronological order with E1 being mentioned in a flashback (E2, E3, E1, E4; Experiments 2-4). The information about the duration of E2 was manipulated, and the mental accessibility of E1 was tested at the end of a passage. All 4 experiments showed that E1 was less accessible if the text implied that it occurred a relatively long time ago in the described world compared with when it occurred a shorter time ago. This result suggests that readers construct a temporally organized representation even if the text structure does not suggest such an organization. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
67.
Active centers, catalytic behavior, symbiosis and redox properties of MoV(Nb,Ta)TeO ammoxidation catalysts 总被引:1,自引:0,他引:1
Robert K. Grasselli Douglas J. Buttrey James D. Burrington Arne Andersson Johan Holmberg Wataru Ueda Jun Kubo Claus G. Lugmair Anthony F. Volpe Jr 《Topics in Catalysis》2006,38(1-3):7-16
Selective as well as waste forming active centers were defined for MoVNbTeO and MoVTaTeO catalysts in the ammoxidation of
propane to acrylonitrile and all catalytic functionalities were assigned to specific elements at the respective active centers.
Symbiosis between M1 and M2 phases of these catalysts was observed, with phase cooperation being more extensive in the Nb than Ta containing compositions.
The difference in catalytic effectiveness arises most likely because contact and surface area exposure of the two respective,
cooperating phase pairs are not equal. The M1 phase of the catalysts is reducible by propane and ammonia in the absence of dioxygen and is regenerable to its original,
fully oxidized state by dioxygen (air). No structural collapse is observed even after 120 C3H8 + NH3 reduction pulses. The so induced reduction of the catalyst extends up to 70 layers deep. The product distribution over the
first few pulses is very similar to that under catalytic conditions, supporting the concept that lattice oxygen is involved
in the catalytic ammoxidation process. Therefore, the ammoxidation of paraffins is a redox process, as is of course the well-known
olefin ammoxidation process. 相似文献
68.
69.
70.