全文获取类型
收费全文 | 2852篇 |
免费 | 89篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 179篇 |
综合类 | 4篇 |
化学工业 | 771篇 |
金属工艺 | 82篇 |
机械仪表 | 70篇 |
建筑科学 | 67篇 |
能源动力 | 122篇 |
轻工业 | 285篇 |
水利工程 | 4篇 |
石油天然气 | 6篇 |
武器工业 | 2篇 |
无线电 | 172篇 |
一般工业技术 | 493篇 |
冶金工业 | 324篇 |
原子能技术 | 80篇 |
自动化技术 | 288篇 |
出版年
2023年 | 11篇 |
2022年 | 35篇 |
2021年 | 70篇 |
2020年 | 25篇 |
2019年 | 34篇 |
2018年 | 47篇 |
2017年 | 43篇 |
2016年 | 63篇 |
2015年 | 38篇 |
2014年 | 87篇 |
2013年 | 168篇 |
2012年 | 140篇 |
2011年 | 159篇 |
2010年 | 130篇 |
2009年 | 163篇 |
2008年 | 149篇 |
2007年 | 123篇 |
2006年 | 109篇 |
2005年 | 97篇 |
2004年 | 77篇 |
2003年 | 63篇 |
2002年 | 76篇 |
2001年 | 53篇 |
2000年 | 65篇 |
1999年 | 56篇 |
1998年 | 150篇 |
1997年 | 88篇 |
1996年 | 85篇 |
1995年 | 68篇 |
1994年 | 53篇 |
1993年 | 51篇 |
1992年 | 38篇 |
1991年 | 26篇 |
1990年 | 21篇 |
1989年 | 29篇 |
1988年 | 19篇 |
1987年 | 22篇 |
1986年 | 27篇 |
1985年 | 22篇 |
1984年 | 20篇 |
1983年 | 17篇 |
1982年 | 10篇 |
1981年 | 13篇 |
1980年 | 21篇 |
1979年 | 10篇 |
1977年 | 19篇 |
1976年 | 15篇 |
1975年 | 7篇 |
1972年 | 6篇 |
1967年 | 7篇 |
排序方式: 共有2949条查询结果,搜索用时 0 毫秒
1.
The performance of surface ionic conduction single chamber fuel cell (SIC‐SCFC) prepared by the sol gel method was studied on electric characteristics due to the differences of the operating temperature and humidity, the electrode distance and electrolyte film depth, and multiple cells with the series and parallel connections. The SIC–SCFC was arranged the both anode of Pt and cathode of Au on the boehmite electrolyte. The open circuit voltage (OCV) of single cell achieved a maximum of 530mV in the dry gas mixtures of O2/H2=50% in room temperature operation, and but it became decrease as over 60%. The OCV was maintained the constant value between operating temperatures of 30°C to 80°C, and but it was decreased sharply at over 90°C because a humidity on the cell became lower as increasing operating temperature. Then, the cell property was improved to 120°C by adding to the humidity of 70% using a humidifier. The electrode distance and the electrolyte film depth of SIC‐SCFC found to be contributed to the reductions of the cell resistance and the surface roughness on the electrode, respectively. Moreover, the power property of SIC‐SCFC was significantly improved by cell stacks comprised of the series or parallel connection of a cell. 相似文献
2.
We present simulation results of the vortex dynamics in a trapped Bose-Einstein condensate in the presence of a rotating optical
lattice. Changing the potential amplitude and the relative rotation frequency between the condensate and the optical lattice,
we find a rich variety of dynamical phases of vortices. In particular, when the optical lattice rotates faster than the condensate,
the competition between the pinning force and the interactions by nucleated interstitial vortices leads to the melting of
vortex lattice, yielding a vortex liquid phase. 相似文献
3.
New technologies such as power electronics have made it possible to change continuously the impedance of a power system not only to control power flow but also to enhance stability. A power system incorporating a variable impedance apparatus such as a variable series capacitor (VSrC) and high-speed phase shifter (HSPS) is called VIPS (Variable Impedance Power System) by the authors. This paper proposes a novel control method of VIPS apparatus such as VSrC and HSPS installed at an interconnecting point for stabilizing inter-area unstable and/or oscillatory modes. The proposed design method of the control system is a kind of hierarchical decentralized control method of a large-scale power system based on a Lyapunov function. Under the proposed control scheme, each subsystem can be stabilized independently by local controllers such as AVR, speed governor and PSS, and then the whole interconnected system can be stabilized by VIPS apparatus taking into account interactions between subsystems. The effectiveness and robustness of the VIPS apparatus control are shown by numerical examples with model systems including a large-scale power system. 相似文献
4.
Norihito Kijima Kenichi Morie Shoichi Nagata Isao Shimono 《Journal of Low Temperature Physics》1996,105(5-6):1511-1516
A strontium tantalum sulfide, SrTa2S5, has a hexagonal structure with lattice constants of a =3.32 and c=24.1 Å. With decreasing temperature the electrical resistivity decreases monotonically and exhibits an abrupt superconducting transition at 3.16 K (midpoint). The diamagnetic susceptibility is observed below Tc. The magnetic susceptibility is nearly independent of temperature above Tc and shows Pauli paramagnetism. 相似文献
5.
T Ayabe H Takenaka O Takenaka A Takenaka H Nagahama H Maruyama A Yamamoto M Nagata Y Koga M Sumida M Hamada 《Canadian Metallurgical Quarterly》1996,38(2):373-381
The pMEX8-hAK1 vector was devised from the pAK plasmid (Kim J. H. et al., 1989, Protein Engineering 5, 379-386), which could directly express human adenylate kinase proteins without recombination and its single strand DNA could be withdrawn with helper phage for random site-directed mutagenesis. The conserved key residues at Lys21, Lys27, and Thr39 were engineered to obtain mutants for kinetic analysis. Three mutants were obtained as K21P, K27R, and T39S, their specific activities were strikingly reduced compared to those of wild type adenylate kinase. This pMEX8-hAK1 will be a powerful tool for site-directed mutagenesis to detect the substrate-enzyme interaction for human adenylate kinase including various other enzymes. 相似文献
6.
7.
K. Y. Cheah T. S. Tang Fujio Mizukami Shu-ichi Niwa Makoto Toba Y. M. Choo 《Journal of the American Oil Chemists' Society》1992,69(5):410-416
A new catalyst, ruthenium-tin-alumina is found to selectively hydrogenate oleic acid to 9-octadecen-1-ol (oleyl + elaidyl
alcohol) at low pressure with high yield. Catalyst preparation methods, catalyst raw materials and activation conditions have
a significant effect on the activity of the catalyst. The optimum atomic ratio of ruthenium to tin is about 1:2. Catalyst
prepared by an improved sol-gel method shows higher activity and selectivity than catalysts prepared by impregnation and coprecipitation
methods. Chloride is found to have a negative effect on catalytic activity. The best catalyst is prepared from chloride-free
ruthenium and tin raw materials. Under the optimum reaction conditions of 250°C and 5.6 MPa, the selectivities for 9-octadecen-1-ol
and total alcohol (9-octadecen-1-ol + stearyl alcohol) formation are 80.9% and 97%, respectively, at a conversion of 81.3%. 相似文献
8.
The three-dimensional dynamics of two interacting quantized vortex filaments is studied. The equations of motion and the method of numerical calculation follow Schwarz. Whether two approaching filaments reconnect or not depends on their arrangement before approach. When a ring moves toward a line from a distance, only within a critical initial distance they can reconnect. The critical distance is minimized when their circulations are parallel at the closest place, while it increases as their circulations begin to deviate from being parallel. Hence the reconnection probability can be less than unity. 相似文献
9.
Michael T. Nagata John G. Speer David K. Matlock 《Metallurgical and Materials Transactions A》2002,33(10):3099-3110
To assess the potential for obtaining and utilizing titanium nitride (TiN) refinement via the increased postsolidification cooling rates associated with thin-slab casting, TiN particle size distributions were evaluated
by transmission electron microscope (TEM) examination of carbon extraction replicas. Eight commercially produced thin-slab
cast TiN steels, nominally 0.05 pct C, 1.2 pct Mn, and one conventionally cast steel were received. Thin slab samples were
taken from three locations in the production process: quenched after casting before the tunnel furnace, quenched after tunnel
furnace soaking, and the as-rolled and air-cooled final product. Effects of cooling rate were evident in the results and agree
with previously documented behavior, where precipitate size decreases with increased cooling rate. Statistical differences
in particle size between specimens from steels with different chemistries were shown. These variations result from differences
in the driving force for precipitation, rates of coarsening, and differences in volume fraction due to changes in steel composition.
The interaction of composition and processing, such as soaking in the tunnel furnace and rolling, was found to be important.
For example, the hyperstoichiometric steel (excess Ti) exhibited fine TiN after casting and soaking, but dramatic coarsening
after hot rolling. This behavior was attributed to deformation enhanced particle coarsening, or incomplete precipitation after
soaking, followed by continued growth during subsequent processing. 相似文献
10.
Makoto Hino Minoru Hiramatsu Koichi Akiyama Hitoshi Kawasaki Masato Tsujikawa Makoto Kawamoto 《Materials and Manufacturing Processes》1997,12(1):37-46
A high powered YAG laser with kaleidoscope for surface modification was applied to the surface hardening of carbon steels containing 0. 18-0.54 wt% C without the absorbents, and the relationships between laser processing and surface hardening were investigated by hardness and microstructure. The structure of the hardened zone underwent complete martensitic transformation in all of the carbon steels tested, and its hardness increased with greater carbon content. Under identical irradiated conditions, the hardened zone expanded with increasing carbon content. A hardened zone extending from the surface to a depth of 1.0 mm was obtained at a laser power of 1.0 kW and a scanning speed of 1 mm/sec. It was found that in the surface hardening of carbon steels, a high powered YAG laser can be used to control the hardened zone by selecting the appropriate irradiation conditions, however, the hardened zone was affected by the assistant gas and the flow rate. 相似文献