全文获取类型
收费全文 | 434篇 |
免费 | 16篇 |
专业分类
电工技术 | 8篇 |
化学工业 | 104篇 |
金属工艺 | 11篇 |
机械仪表 | 2篇 |
建筑科学 | 40篇 |
能源动力 | 10篇 |
轻工业 | 33篇 |
水利工程 | 3篇 |
石油天然气 | 2篇 |
无线电 | 49篇 |
一般工业技术 | 79篇 |
冶金工业 | 74篇 |
原子能技术 | 1篇 |
自动化技术 | 34篇 |
出版年
2023年 | 5篇 |
2022年 | 9篇 |
2021年 | 6篇 |
2020年 | 3篇 |
2019年 | 9篇 |
2018年 | 4篇 |
2017年 | 12篇 |
2016年 | 14篇 |
2015年 | 2篇 |
2014年 | 8篇 |
2013年 | 15篇 |
2012年 | 18篇 |
2011年 | 17篇 |
2010年 | 14篇 |
2009年 | 12篇 |
2008年 | 20篇 |
2007年 | 15篇 |
2006年 | 21篇 |
2005年 | 16篇 |
2004年 | 14篇 |
2003年 | 13篇 |
2002年 | 12篇 |
2001年 | 7篇 |
2000年 | 9篇 |
1999年 | 6篇 |
1998年 | 23篇 |
1997年 | 18篇 |
1996年 | 13篇 |
1995年 | 10篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 7篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1982年 | 8篇 |
1981年 | 12篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 8篇 |
1976年 | 7篇 |
1973年 | 4篇 |
1930年 | 1篇 |
排序方式: 共有450条查询结果,搜索用时 62 毫秒
91.
Thin metal films used as Schottky contacts to semiconductors are sometimes connected in one spot only. The change of the forward IV-characteristics then caused by the finite sheet conductivity of the metal film is considered, using a model which is solved by computer techniques. The results are plotted as the deviations from the usual ln Ifvvs Vfv linear plots, for different ratios of the radii R and r0 of the C circular metal contact and the connecting wire, and with the sheet resistivity of the metal film as a parameter. The calculations are performed for the barrier height φBn = 0.79 eV. The effective series resistance of the contact wire-sheet-platelet system varies with current, but is of the order of the sheet resistivity of the film, for R/r0 ratios region of ~20–100. 相似文献
92.
Numerical calculations of charge distributions and injection ratios for high-barrier Schottky diodes are performed to extend the understanding of this type of phenomena under various conditions. The calculations are performed for two doping concentrations, 1014 and 1013 cm?3, in n-type silicon and for several barrier heights in the range 0.92-0.79 eV. Two sets of carrier lifetimes are used to give nominal diffusion lengths that are much larger than, or comparable with, the dimension of the structure. The boundary conditions at the barrier were those of the combined diffusion-emission model. The back contact was modeled as a perfect ohmic contact, or as a low-high junction. The results are compared with experiments involving the use of injecting Schottky rectifiers, capable of giving low forward-voltage drop and sustaining moderately-high reverse voltages. 相似文献
93.
LT Van der Ven PJ Roholl T Gloudemans SC Van Buul-Offers MJ Welters BA Bladergroen JA Faber JS Sussenbach W Den Otter 《Canadian Metallurgical Quarterly》1997,75(11):1631-1640
To assess the role of insulin-like growth factors (IGFs) in growth and transformation of normal (myometrium) and tumorous smooth muscle cell (SMC) tissues, in situ hybridization (ISH) analysis for insulin-like growth factor I and II (IGF-I and IGF-II) mRNAs was combined with detection of IGF peptides, their receptors and IGF binding protein-3 (IGFBP-3). mRNAs for both IGFs were detected in smooth muscle cells in normal, benign and malignant SMC tissues, together with the IGF peptides, both IGF receptors and IGFBP-3. This suggests an autocrine role for both IGFs. Leiomyomas had higher IGF-I peptide levels and higher levels of type I IGF receptors than myometrium, supporting the idea that IGFs play a role in the growth and transformation of these tumours. Low-grade leiomyosarcomas contained more IGF-II mRNAs than myometrium and leiomyoma, fewer type II IGF/mannose 6-phosphate receptors and less IGFBP-3 than myometrium and, in addition, fewer IGF-I mRNAs and type I IGF receptors than leiomyoma. Intermediate- and high-grade leiomyosarcomas had intermediate levels of IGF-II mRNAs and peptide, ranging between those in myometrium and low-grade leiomyosarcomas. Thus, growth and transformation of leiomyosarcomas may be regulated by IGF-II, although more markedly in low-grade than in high-grade leiomyosarcomas. In conclusion, the various categories of SMC tissues are associated with a distinct expression pattern of the IGF system. This suggests that each category of SMC tumours arises as a distinct entity and that there is no progression of transformation in these tissues. 相似文献
94.
Forming Single-Phase Laminates via the Gelcasting Technique 总被引:1,自引:0,他引:1
Donald M. Baskin Michael H. Zimmerman K. T. Faber Edwin R. Fuller 《Journal of the American Ceramic Society》1997,80(11):2929-2932
Single–phase laminates of iron titanate were formed by gelcasting in both the presence and absence of a magnetic field to produce alternating layers of textured and nontextured microstructure, respectively. X–ray analysis was performed on each lamina verifying that alignment was maintained throughout processing. Tunnel cracks were found in trilayer laminates (nontextured/textured/nontextured) when the alignment direction was parallel to the interface between layers. The cracks are consistent with a stress profile of residual tension parallel to the interface in the textured layer. 相似文献
95.
Hongda Cai K. T. Faber Edwin R. Fuller Jr. 《Journal of the American Ceramic Society》1992,75(11):3111-3117
Crack bridging by inclined fibers has been studied in a brittle fiber–brittle matrix model ceramic composite. Results of the fiber bridging force vs the crack opening displacement have been obtained for different fiber inclination angles using a fracture mechanics approach. Localized matrix cracking has been observed for inclined fibers and related to fiber inclination angle. The experimental results showing the influence of fiber inclination angle are discussed and compared with theoretical analyses to provide insight into crack bridging by inclined fibers/whiskers. Implications for toughening by whisker bridging are also discussed. 相似文献
96.
A model-based four-dimensional left ventricular surface detector 总被引:1,自引:0,他引:1
The authors have developed a general model-based surface detector for finding the four-dimensional (three spatial dimensions plus time) endocardial and epicardial left ventricular boundaries. The model encoded left ventricular (LV) shape, smoothness, and connectivity into the compatibility coefficients of a relaxation labeling algorithm. This surface detection method was applied to gated single photon emission computed tomography (SPECT) perfusion images, tomographic radionuclide ventriculograms, and cardiac rotation magnetic resonance images. Its accuracy was investigated using actual patient data. Global left ventricular volumes correlated well, with a maximum correlation coefficient of 0.98 for magnetic resonance imaging (MRI) endocardial surfaces and a minimum of 0.88 for SPECT epicardial surfaces. The average absolute errors of edge detection were 6.4, 5.6. and 4.6 mm for tomographic radionuclide ventriculograms, gated perfusion SPECT, and magnetic resonance images, respectively. 相似文献
97.
Copper(I) Thiocyanate (CuSCN) Hole‐Transport Layers Processed from Aqueous Precursor Solutions and Their Application in Thin‐Film Transistors and Highly Efficient Organic and Organometal Halide Perovskite Solar Cells 下载免费PDF全文
Nilushi Wijeyasinghe Anna Regoutz Flurin Eisner Tian Du Leonidas Tsetseris Yen‐Hung Lin Hendrik Faber Pichaya Pattanasattayavong Jinhua Li Feng Yan Martyn A. McLachlan David J. Payne Martin Heeney Thomas D. Anthopoulos 《Advanced functional materials》2017,27(35)
This study reports the development of copper(I) thiocyanate (CuSCN) hole‐transport layers (HTLs) processed from aqueous ammonia as a novel alternative to conventional n‐alkyl sulfide solvents. Wide bandgap (3.4–3.9 eV) and ultrathin (3–5 nm) layers of CuSCN are formed when the aqueous CuSCN–ammine complex solution is spin‐cast in air and annealed at 100 °C. X‐ray photoelectron spectroscopy confirms the high compositional purity of the formed CuSCN layers, while the high‐resolution valence band spectra agree with first‐principles calculations. Study of the hole‐transport properties using field‐effect transistor measurements reveals that the aqueous‐processed CuSCN layers exhibit a fivefold higher hole mobility than films processed from diethyl sulfide solutions with the maximum values approaching 0.1 cm2 V?1 s?1. A further interesting characteristic is the low surface roughness of the resulting CuSCN layers, which in the case of solar cells helps to planarize the indium tin oxide anode. Organic bulk heterojunction and planar organometal halide perovskite solar cells based on aqueous‐processed CuSCN HTLs yield power conversion efficiency of 10.7% and 17.5%, respectively. Importantly, aqueous‐processed CuSCN‐based cells consistently outperform devices based on poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate HTLs. This is the first report on CuSCN films and devices processed via an aqueous‐based synthetic route that is compatible with high‐throughput manufacturing and paves the way for further developments. 相似文献
98.
Antisera to the C-peptide of human proinsulin were obtained by immunizing guinea pigs with synthetic benzyloxycarbonyl-C-peptide conjugated to human albumin with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide. In three series of 10, the animals were injected with C-peptide conjugated to albumin in the molar ratio of 23 : 1, 15 : 1, and 4 : 1, respectively. Antibodies to human C-peptide were present in all the surviving 25 animals. Fifteen of the antisera were suitable for measuring C-peptide concentrations lower than 0.10 pmol/ml. The antisera demonstrated an increasing immunogenicity with increasing molar ratio of C-peptide to albumin in the conjugate. In the fourth series, ten guinea pigs immunized with benzyloxycarbonyl-C-peptide ionically bound to QAE-Sephadex A-25 did not produce detectable antibodies to C-peptide. A qualitative evaluation of the radioimmunoassay by use of the antiserum with the highest titer and sensitivity, "M 1230", revealed a mean intra-assay and inter-assay coefficient of variance of 3.2 and 9.6%, respectively. 相似文献
99.
As part of a complex network of genome control, long regulatory RNAs exert significant influences on chromatin dynamics. Understanding how this occurs could illuminate new avenues for disease treatment and lead to new hypotheses that would advance gene regulatory research. Recent studies using the model fission yeast Schizosaccharomyces pombe (S. pombe) and powerful parallel sequencing technologies have provided many insights in this area. This review will give an overview of key findings in S. pombe that relate long RNAs to multiple levels of chromatin regulation: histone modifications, gene neighborhood regulation in cis and higher-order chromosomal ordering. Moreover, we discuss parallels recently found in mammals to help bridge the knowledge gap between the study systems. 相似文献
100.
Emilie Dauzon Yuanbao Lin Hendrik Faber Emre Yengel Xavier Sallenave Cedric Plesse Fabrice Goubard Aram Amassian Thomas D. Anthopoulos 《Advanced functional materials》2020,30(28)
The development of transparent, conducting, and stretchable poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)‐based electrodes using a combination of a polyethylene oxide (PEO) polymer network and the surfactant Zonyl is reported. The latter improves the ductility of PEDOT:PSS and enables its deposition on hydrophobic surfaces such as polydimethylsiloxane (PDMS) elastomers, while the presence of a 3D matrix offers high electrical conductivity, elasticity, and mechanical recoverability. The resulting electrode exhibits attractive properties such as high electrical conductivity of up to 1230 S cm?1 while maintaining high transparency of 95% at 550 nm. The potential of the electrode technology is demonstrated in indium‐tin‐oxide (ITO)‐free solar cells using the PBDB‐T‐2F:IT‐4F blend with a power conversion efficiency of 12.5%. The impact of repeated stretch‐and‐release cycles on the electrical resistance is also examined in the effort to evaluate the properties of the electrodes. The interpenetrated morphology of the PEDOT:PSS and polyethylene oxide network is found to exhibit beneficial synergetic effects resulting in excellent mechanical stretchability and high electrical conductivity. By carefully tuning the amount of additives, the ability to detect small changes in electrical resistance as a function of mechanical deformation is demonstrated, which enables the demonstration of stretchable and resilient on‐skin strain sensors capable of detecting small motions of the finger. 相似文献