全文获取类型
收费全文 | 2696篇 |
免费 | 57篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 170篇 |
综合类 | 5篇 |
化学工业 | 506篇 |
金属工艺 | 95篇 |
机械仪表 | 82篇 |
建筑科学 | 38篇 |
能源动力 | 148篇 |
轻工业 | 187篇 |
水利工程 | 8篇 |
石油天然气 | 1篇 |
无线电 | 303篇 |
一般工业技术 | 493篇 |
冶金工业 | 456篇 |
原子能技术 | 97篇 |
自动化技术 | 174篇 |
出版年
2023年 | 11篇 |
2022年 | 33篇 |
2021年 | 36篇 |
2020年 | 27篇 |
2019年 | 23篇 |
2018年 | 40篇 |
2017年 | 38篇 |
2016年 | 42篇 |
2015年 | 35篇 |
2014年 | 63篇 |
2013年 | 128篇 |
2012年 | 71篇 |
2011年 | 120篇 |
2010年 | 97篇 |
2009年 | 103篇 |
2008年 | 120篇 |
2007年 | 114篇 |
2006年 | 96篇 |
2005年 | 112篇 |
2004年 | 93篇 |
2003年 | 86篇 |
2002年 | 75篇 |
2001年 | 54篇 |
2000年 | 60篇 |
1999年 | 76篇 |
1998年 | 179篇 |
1997年 | 145篇 |
1996年 | 107篇 |
1995年 | 67篇 |
1994年 | 63篇 |
1993年 | 41篇 |
1992年 | 29篇 |
1991年 | 31篇 |
1990年 | 23篇 |
1989年 | 19篇 |
1988年 | 34篇 |
1987年 | 30篇 |
1986年 | 25篇 |
1985年 | 31篇 |
1984年 | 23篇 |
1983年 | 20篇 |
1982年 | 14篇 |
1981年 | 20篇 |
1980年 | 17篇 |
1979年 | 15篇 |
1978年 | 16篇 |
1977年 | 15篇 |
1976年 | 15篇 |
1973年 | 6篇 |
1972年 | 5篇 |
排序方式: 共有2763条查询结果,搜索用时 15 毫秒
1.
Deformation behavior of stoichiometric blends made from poly(styrene-co-styrenesulfonic acid) (SPS) and poly(styrene-co-4-vinylpyridine) (SVP) was investigated by TEM observation of strained thin films. An FTIR investigation revealed that ionic cross-links were formed between the component polymers upon blending due to intermolecular ion-ion interactions, which arose from proton transfer from sulfonic acid groups to pyridine groups. TEM observations indicate that the deformation mode of the blends changed from crazing only to crazing plus shear deformation, with the shear contribution becoming larger, as the ion content in the blends increased. Such changes in deformation mode can be understood as arising from an increase in the ‘effective’ strand density due to the formation of ionic cross-links upon blending. It was also found that the ionic cross-links via pyridinium cation/sulfonate anion ion pairs were more effective in inducing the transition of deformation mode than ionic cross-links via -SO3−/Na+ or -SO3−/Ca2+ ion pairs. 相似文献
2.
3.
4.
K. Fujii J. Fujimoto H. Hayashii R. Kajikawa Y. Masatani H. Ozaki A. Sugiyama R. Suzaki S. Suzuki T.Y. Tsukamoto T.F. Tsukamoto S. Uno S. Iwata 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1985,236(1):55-63
We constructed and tested a prototype gas sampling electromagnetic calorimeter of the Pb-proportional tube sandwich type. The calorimeter uses conductive plastic tubes and cathode pad readout with a tower structure which resulted in reasonable energy and spatial resolutions for electrons in the momentum range 0.5–4.0 GeV/c; /c). This paper describes the test and the performance studied under various conditions. 相似文献
5.
H Kuniyasu W Yasui F Shimamoto K Fujii M Nakahara T Asahara K Dohi E Tahara 《Canadian Metallurgical Quarterly》1996,46(12):1005-1010
A rare case of hepatoblastoma in a 61-year-old Japanese housewife is described. This liver tumor mainly consisted of two tissue components: embryonal hepatocytes and primitive mesenchymal tissue. Fetal hepatocytes with alpha-fetoprotein production, gland formation, cartilage and osteoid were also found in a small portion. Molecular analysis by slot blot method revealed increased copy numbers of c-met and K-sam proto-oncogenes and cyclin D1 genes. These findings suggest that alterations of these oncogenes might play a role in the development of adult hepatoblastoma. 相似文献
6.
A new mathematical model for study of an interface crack between two dissimilar elastic half planes is proposed. A process zone is formed along the interface between the physical crack and the continuous part. Both the crack opening (and sliding) displacement with a smooth shape and the finite magnitude of stress concentration appear in this zone. The analytical model is expressed by closed elastic solutions using complex variables, but with no oscillations at the crack tip. 相似文献
7.
A solid oxide fuel cell using a thin ceria-based electrolyte film with a Ru-catalyzed anode was directly operated on hydrocarbons, including methane, ethane, and propane, at 600 °C. The role of the Ru catalyst in the anode reaction was to promote the reforming reaction of the unreacted hydrocarbons by the produced steam and CO2, which avoided interference from steam and CO2 in the gas-phase diffusion of the fuels. The resulting peak power density reached 750 mW cm−2 with dry methane, which was comparable to the peak power density of 769 mW cm−2 with wet (2.9 vol.% H2O) hydrogen. More important was the fact that the cell performance was maintained at a high level regardless of the change in the methane utilization from 12 to 46% but was significantly reduced by increasing the hydrogen utilization from 13 to 42%. While the anodic reaction of hydrogen was controlled by the slow gas diffusion, the anodic reaction of methane was not subject to the onset of such a gas-diffusion process. 相似文献
8.
Hydrothermal Synthesis and Low-Temperature Sintering of Zinc Gallate Spinel Fine Particles 总被引:1,自引:0,他引:1
Nanosized powders of single-phase zinc gallate (ZnGa2 O4 ) spinel were hydrothermally synthesized from solutions in the presence of NaOH over the pH range of 1.9 to 7.0 and from solutions above pH 7.0, i.e., the very basic medium (pH of 13.85), by removing the residual ZnO phase by washing with aqueous H2 SO4 from the precipitate mixtures of zinc gallate spinel particles and ZnO. A very wide compositional range (Zn/2Ga = 0.705–1.157) of zinc gallate spinel solid solutions could be hydrothermally synthesized in the form of nanosized particles from acid and very basic mediums (pH of 2.4–13.85) in the presence of NaOH. These hydrothermally synthesized spinel powders showed good sinterability and almost full densification at 1100°C for 1 h. Dense sintered bodies consisting of single-phase zinc gallate spinel were fabricated at 1100°C using zinc gallate spinel powders having almost stoichiometric composition formed from the solution at pH 9.95 in the presence of aqueous ammonia. 相似文献
9.
Narita K. Horiguchi Y. Fujii T. Nakamura K. 《Electron Devices, IEEE Transactions on》1997,44(7):1124-1130
A novel on-chip electrostatic discharge (ESD) protection for high-speed CMOS LSI's that operate at higher than 500 MHz has been developed. Introduction of a newly developed common discharge line (CDL) can completely eliminate the protection device influence on the inner circuit operation. This enables minimization of the I/O capacitance by shrinking the dimension of the output transistor, which also serves as a protection device in conventional devices. This new protection (CDL protection) was applied to a high-speed DRAM of which I/O pin capacitance specification is 2 pF. As a result, the ESD tolerance of 4 kV for the charged device model test, 4 kV for the human body model test, and 700 V for the machine model test were obtained. In addition, the DRAM data rate higher than 660 MHz at room temperature was achieved. The results show significant improvement for both ESD and the I/O capacitance, compared with the conventional structure 相似文献
10.
This paper focuses on the microscopic damage and progressive failure of a composite reinforced by plain-weave glass cloth under tensile fatigue loading. The fatigue process was divided into three stages like that of multi-directional laminates. It was found that the internal damage at each stage (matrix cracks, debonds in the weft, successive debonds in the warp and ‘metadelaminations’ between warps and wefts) occurred near the cross-over point of the fabric. The modulus decay mechanism was explained by considering the progression of this internal damage. From the end of the first stage to the beginning of the middle stage, a characteristic damage state (CDS) (called a ‘meta-CDS’) was observed. It was found that woven composites have a unit area of damage accumulation (called a ‘unit cell’) and the damage of each unit cell and its distribution control the total fatigue damage of the material. 相似文献