全文获取类型
收费全文 | 19349篇 |
免费 | 963篇 |
国内免费 | 140篇 |
专业分类
电工技术 | 328篇 |
综合类 | 32篇 |
化学工业 | 4322篇 |
金属工艺 | 597篇 |
机械仪表 | 635篇 |
建筑科学 | 373篇 |
矿业工程 | 47篇 |
能源动力 | 1400篇 |
轻工业 | 1178篇 |
水利工程 | 157篇 |
石油天然气 | 84篇 |
武器工业 | 1篇 |
无线电 | 2402篇 |
一般工业技术 | 4413篇 |
冶金工业 | 1450篇 |
原子能技术 | 178篇 |
自动化技术 | 2855篇 |
出版年
2024年 | 105篇 |
2023年 | 422篇 |
2022年 | 1001篇 |
2021年 | 1182篇 |
2020年 | 926篇 |
2019年 | 958篇 |
2018年 | 1236篇 |
2017年 | 979篇 |
2016年 | 937篇 |
2015年 | 615篇 |
2014年 | 861篇 |
2013年 | 1546篇 |
2012年 | 927篇 |
2011年 | 1091篇 |
2010年 | 882篇 |
2009年 | 830篇 |
2008年 | 732篇 |
2007年 | 598篇 |
2006年 | 484篇 |
2005年 | 370篇 |
2004年 | 283篇 |
2003年 | 247篇 |
2002年 | 191篇 |
2001年 | 181篇 |
2000年 | 173篇 |
1999年 | 171篇 |
1998年 | 292篇 |
1997年 | 238篇 |
1996年 | 221篇 |
1995年 | 169篇 |
1994年 | 160篇 |
1993年 | 152篇 |
1992年 | 103篇 |
1991年 | 131篇 |
1990年 | 100篇 |
1989年 | 99篇 |
1988年 | 84篇 |
1987年 | 88篇 |
1986年 | 75篇 |
1985年 | 86篇 |
1984年 | 74篇 |
1983年 | 71篇 |
1982年 | 61篇 |
1981年 | 70篇 |
1980年 | 48篇 |
1979年 | 31篇 |
1978年 | 27篇 |
1977年 | 26篇 |
1976年 | 35篇 |
1975年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Shared-memory based packet switches are known to provide the best possible throughput performance for bursty data traffic in high-speed packet networks and internets compared with other buffering strategies under conditions of identical memory resources deployed in the switch. However, scaling of shared-memory packet switches to a larger size has been restricted mainly due to the physical limitations imposed by the memory-access speed and the centralized control for switching functions in shared-memory switches. A new scalable architecture for a shared-memory packet switch, called the sliding-window (SW) switch, is proposed to overcome these limitations. The SW switch introduces a new class of switching architecture, where physically separate multiple memory modules are logically shared among all the ports of the switch, and the control is decentralized. The SW switch alleviates the bottleneck caused by the centralized control of switching functions in large shared-memory switches. Decentralized switching functions enable the SW switch to operate in a pipeline fashion to enhance scalability and switching capacity compared with that of previously known classes of shared-memory switch architecture. 相似文献
102.
Novel star-like wholly aromatic copolyesters having four arms based on a tetraamine star core, p- and m- hydroxybenzoic acids and 6-hydroxy-2-naphthoic acid have been successfully synthesized and spun into fibers for the investigation of the effect of the star-like structure on improving compressive properties of the fiber. The reactivity of the star core was demonstrated using a model compound with FTIR, 1H and 13C NMR spectroscopy. The 13C NMR spectrum of the star-like terpolymer having a molar ratio of 10:1 of the monomers to star core showed a characteristic peak at around δ62 ppm which corresponds to a tetra-substituted carbon and thereby demonstrates that the star core was really incorporated into the polymer. The star-like copolyester exhibited a clear stir opalescence and liquid crystalline morphology in the temperature range of 150-280 °C. However, no transition was observed in the DSC thermogram except a clear Tg at 110 °C. The star-like terpolymer fiber, prepared from a polymer with a molar ratio of 500:1 for the monomers to imide core, was spun in the liquid crystalline state at 180 °C. Fiber structure and properties have been studied. 相似文献
103.
104.
In the modeling of the gas metal-arc (GMA) welding process, heat inputs to the workpiece by the arc and the metal transfers
have been considered separately. The heat energy delivered due to the metal transfer has been approximated in the form of
a cylindrical volumetric heat source, whose dimensions of the radius and the height are dependent on the molten metal droplet
characteristics. The pinch instability theory (PIT) and the static force balance theory (SFBT) of drop detachment have independently
been used to obtain the expressions for various characteristics of the drop,i.e., the drop radius, the drop velocity, and the drop frequency at various welding parameters. The occurrence or the nonoccurrence
of finger penetration, routinely found in the GMA welding at high welding currents, has been satisfactorily explained by the
cylindrical heat source model. The effect of various welding parameters,e.g., the welding current, the wire radiusetc., on the weld bead penetration characteristics has been investigated. In this modeling effort, the heat conduction equation
has been solved in three dimensions. 相似文献
105.
In the present work Taguchi's approach has been applied to the V-process castings of Al-11 per cent Si alloy to acertain the most influential control factors which will provide better and consistent surface finish to the castings regardless of the noise factors present. The control factors of the V-process that may affect the quality of the castings are the molding sand, vibration frequency, vibrating time, degree of vacuum imposed, and pouring temperature. In order to understand how these factors affect the surface roughness of the V-process castings, response surface methodology has been applied, and to obtain the optimal setting of the control factors Taguchi's method has been used. It is found that the pouring temperature has a significant effect on the surface roughness of Al-11 per cent Si alloy castings made by a V-process. Thus the pouring temperature must be kept at the lower level. All other factors are insignificant. Therefore, any setting of the insignificant factors/variables that give the minimum cost can be used. 相似文献
106.
PV Kumar 《Canadian Metallurgical Quarterly》1994,38(5):702-706
From 1980 to 1992, five cases of Askin tumor were diagnosed by fine needle aspiration cytology at the Shiraz University Hospitals, Namazi, Faghihi and Beheshti, Iran. All patients were female, their ages ranging between 15 and 22 years. Three of them had a mass on the right side and two on the left side of the chest. Chest roentgenography revealed no bone involvement. Two tumors involved the lungs and pleura. Urinary catecholamine levels were within normal limits. The fine needle aspiration smears revealed many small, round malignant cells with indistinct cytoplasm, a high nuclear/cytoplasmic ratio and prominent, multiple nucleoli. Homer-Wright rosettes were seen frequently. The cells were often arranged in rows simulating rouleaux formation. They were positively stained by periodic acid-Schiff stain. The histologic sections confirmed the cytologic diagnosis of Askin tumor. Four of the patients died within 7-11 months after treatment began. 相似文献
107.
108.
Vijay Kumar 《Bulletin of Materials Science》1996,19(6):1047-1058
With the discovery of solid C60, efforts are being made to develop new clusters and molecules which could be assembled to form new materials. Here we present
some recent developments in this direction and discuss bonding in such materials. 相似文献
109.
110.
S Kasiviswanathan P S Asoka Kumar B K Mathur K L Chopra 《Bulletin of Materials Science》1996,19(2):411-416
Surface structure of thin silver films (200 Å) on two technologically important films, indium tin oxide (ITO) and aluminium oxide, has been studied using scanning tunneling microscope. ITO films were prepared by reactive electron beam evaporation. Aluminium oxide films were prepared by oxidizing 2000 Å thick aluminium films evaporated on to H2 terminated single crystal silicon substrates. The surface structure of silver on ITO and aluminium oxide appeared to be same and was characteristic of Stranski-Krastanov type. The observed asymmetry in the island shape was attributed to the anisotropic nature of the strain fields surrounding the nucleation centres. 相似文献