全文获取类型
收费全文 | 5705篇 |
免费 | 357篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 74篇 |
综合类 | 13篇 |
化学工业 | 1419篇 |
金属工艺 | 138篇 |
机械仪表 | 115篇 |
建筑科学 | 402篇 |
矿业工程 | 29篇 |
能源动力 | 146篇 |
轻工业 | 450篇 |
水利工程 | 49篇 |
石油天然气 | 7篇 |
无线电 | 450篇 |
一般工业技术 | 1231篇 |
冶金工业 | 248篇 |
原子能技术 | 37篇 |
自动化技术 | 1259篇 |
出版年
2024年 | 7篇 |
2023年 | 96篇 |
2022年 | 72篇 |
2021年 | 227篇 |
2020年 | 149篇 |
2019年 | 128篇 |
2018年 | 189篇 |
2017年 | 165篇 |
2016年 | 248篇 |
2015年 | 242篇 |
2014年 | 301篇 |
2013年 | 400篇 |
2012年 | 380篇 |
2011年 | 463篇 |
2010年 | 356篇 |
2009年 | 340篇 |
2008年 | 342篇 |
2007年 | 317篇 |
2006年 | 240篇 |
2005年 | 212篇 |
2004年 | 160篇 |
2003年 | 149篇 |
2002年 | 126篇 |
2001年 | 81篇 |
2000年 | 78篇 |
1999年 | 66篇 |
1998年 | 75篇 |
1997年 | 45篇 |
1996年 | 50篇 |
1995年 | 57篇 |
1994年 | 35篇 |
1993年 | 33篇 |
1992年 | 29篇 |
1991年 | 20篇 |
1990年 | 18篇 |
1989年 | 18篇 |
1988年 | 15篇 |
1987年 | 13篇 |
1986年 | 8篇 |
1985年 | 5篇 |
1984年 | 23篇 |
1983年 | 9篇 |
1982年 | 9篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1976年 | 9篇 |
1975年 | 6篇 |
1974年 | 5篇 |
排序方式: 共有6067条查询结果,搜索用时 15 毫秒
991.
992.
We present a detailed analysis of the patient and resource scheduling problem in rehabilitation hospitals. In practice, the
predominantly therapeutical treatments and activities which are prescribed for the patients are typically scheduled manually.
This leads to rigid and inefficient schedules which can have negative effects on the quality of care and the patients’ satisfaction.
We outline the conceptual framework of a decision support system for the scheduling process that is based on formal optimization
models. To this end, we first develop a large-scale monolithic optimization model. Then we derive a numerically tractable
hierarchical model system in order to deal with problem instances of realistic sizes. We report numerical results with respect
to solution times, model sizes and solution quality. 相似文献
993.
Aromatic polyimide films are processed from polyamic acid solutions. This process involved the simultaneous loss of solvent and chemical conversion of polyamic acid to polyimide, and implied structural reorganization which led to changed physical properties. Polymer films generated from benzophenonetetracarboxylic dianhydride and 4,4′-diamino-3,3′-dimethyl diphenylmethane have been investigated at different stages of thermal treatment. The surface polarity, which was determined by the presence of polar COOH and CONH groups, changed during polyamic acid thermal treatment. These polar groups were removed step by step by imidization process leading to the modification of the physical properties of the polymer film. 相似文献
994.
Vignolini S Yufa NA Cunha PS Guldin S Rushkin I Stefik M Hur K Wiesner U Baumberg JJ Steiner U 《Advanced materials (Deerfield Beach, Fla.)》2012,24(10):OP23-OP27
Optical metamaterials have unusual optical characteristics that arise from their periodic nanostructure. Their manufacture requires the assembly of 3D architectures with structure control on the 10-nm length scale. Such a 3D optical metamaterial, based on the replication of a self-assembled block copolymer into gold, is demonstrated. The resulting gold replica has a feature size that is two orders of magnitude smaller than the wavelength of visible light. Its optical signature reveals an archetypal Pendry wire metamaterial with linear and circular dichroism. 相似文献
995.
We present measurements of the change in ionic conductance due to double-stranded (ds) DNA translocation through small (6 nm diameter) nanopores at low salt (100 mM KCl). At both low (<200 mV) and high (>600 mV) voltages we observe a current enhancement during DNA translocation, similar to earlier reports. Intriguingly, however, in the intermediate voltage range, we observe a new type of composite events, where within each single event the current first decreases and then increases. From the voltage dependence of the magnitude and timing of these current changes, we conclude that the current decrease is caused by the docking of the DNA random coil onto the nanopore. Unexpectedly, we find that the docking time is exponentially dependent on voltage (t ∝ e(-V/V(0))). We discuss a physical picture where the docking time is set by the time that a DNA end needs to move from a random location within the DNA coil to the nanopore. Upon entrance of the pore, the current subsequently increases due to enhanced flow of counterions along the DNA. Interestingly, these composite events thus allow to independently measure the actual translocation time as well as the docking time before translocation. 相似文献
996.
H Aouani M Navarro-Cia M Rahmani TP Sidiropoulos M Hong RF Oulton SA Maier 《Nano letters》2012,12(9):4997-5002
We report the experimental realization of efficient tunable nanosources of second harmonic light with individual multiresonant log-periodic optical antennas. By designing the nanoantenna with a bandwidth of several octaves, simultaneous enhancement of fundamental and harmonic fields is observed over a broad range of frequencies, leading to a high second harmonic conversion efficiency, together with an effective second order susceptibility within the range of values provided by widespread inorganic crystals. Moreover, the geometrical configuration of the nanoantenna makes the generated second harmonic signal independent from the polarization of the fundamental excitation. These results open new possibilities for the development of efficient integrated nonlinear nanodevices with high frequency tunability. 相似文献
997.
First lab-on-chip devices based on active transport by biomolecular motors have been demonstrated for basic detection and sorting applications. However, to fully employ the advantages of such hybrid nanotechnology, versatile spatial and temporal control mechanisms are required. Using a thermo-responsive polymer, we demonstrate the selective starting and stopping of modified microtubules gliding on a kinesin-1-coated surface. This approach allows the self-organized separation of multiple microtubule populations and their respective cargoes. 相似文献
998.
Victor Wessels Gwénaël Le Mené Stefan F. Fischerauer Tanja Kraus Annelie‐Martina Weinberg Peter J. Uggowitzer Jörg F. Löffler 《Advanced Engineering Materials》2012,14(6):B357-B364
A study of Mg‐based bulk metallic glasses (BMGs) as biodegradable bone implants is presented. The implantation site can affect performance, so the BMGs were evaluated in vivo in rat femurs using µ‐CT scans at various times for more than 90 days. Estimates of H2 evolution correlate well with previous in vitro studies and bone–implant contact is similar to that for Ti pins. One potential drawback of Mg‐based BMGs in this application is embrittlement due to structural relaxation. Here, relaxation at 20 and 37 °C is examined, and an increase in the characteristic relaxation time, from 10 to 30 days at 20 °C, is observed as Zn increases from 29 to 32 at.%, correlating with dramatically reduced hydrogen evolution. 相似文献
999.
Schlapak R Danzberger J Armitage D Morgan D Ebner A Hinterdorfer P Pollheimer P Gruber HJ Schäffler F Howorka S 《Small (Weinheim an der Bergstrasse, Germany)》2012,8(1):89-97
The bottom-up approach of DNA nano-biotechnology can create biomaterials with defined properties relevant for a wide range of applications. This report describes nanoscale DNA tetrahedra that are beneficial to the field of biosensing and the targeted immobilization of biochemical receptors on substrate surfaces. The DNA nanostructures act as immobilization agents that are able to present individual molecules at a defined nanoscale distance to the solvent thereby improving biomolecular recognition of analytes. The tetrahedral display devices are self-assembled from four oligonucleotides. Three of the four tetrahedron vertices are equipped with disulfide groups to enable oriented binding to gold surfaces. The fourth vertex at the top of the bound tetrahedron presents the biomolecular receptor to the solvent. In assays testing the molecular accessibility via DNA hybridization and protein capturing, tetrahedron-tethered receptors outperformed conventional immobilization approaches with regard to specificity and amount of captured polypeptide by a factor of up to seven. The bottom-up strategy of creating DNA tetrahedrons is also compatible with the top-down route of nanopatterning of inorganic substrates, as demonstrated by the specific coating of micro- to nanoscale gold squares amid surrounding blank or poly(ethylene glycol)-passivated glass surfaces. DNA tetrahedra can create biofunctionalized surfaces of rationally designed properties that are of relevance in analytical chemistry, cell biology, and single-molecule biophysics. 相似文献
1000.
For decades ferroelectric thin films (FETFs) have been the focus of research and development for next-generation memory and semiconductor devices. FETFs are attractive because their polarization states are highly localized, stable, and switchable. These unique properties are also attractive for (bio)molecular sensing and separation applications. Polarization of both polymer and ceramic FETF results in the expression of a sustained high, non-Faradaic, surface charge density. If these surface charges are maintained in aqueous environments, then the resulting electrostatic forces should induce the formation of electrolyte gradients and aid in the localization of charged species to the surface. Recently, there has been a growing interest in the interfacial properties of FETFs, specifically how they interact with liquid or gaseous phases. Recent work has shown that the FETF polarization state affects adsorption from the gaseous phase, surface catalysis, and cell growth. Encouraged by these findings, the use of FETFs in aqueous environments is explored. After an introduction to FETFs, the growing body of literature on the FETF interface is reviewed, along with the limited number of studies demonstrating FETF function in gas and liquid environments. Finally, the exciting possibilities that FETFs could bring to interfacial engineering and lab-on-chip (LOC) device design is reviewed. 相似文献