全文获取类型
收费全文 | 47014篇 |
免费 | 4455篇 |
国内免费 | 3240篇 |
专业分类
电工技术 | 2002篇 |
技术理论 | 2篇 |
综合类 | 4712篇 |
化学工业 | 6385篇 |
金属工艺 | 3691篇 |
机械仪表 | 2361篇 |
建筑科学 | 6610篇 |
矿业工程 | 1344篇 |
能源动力 | 2125篇 |
轻工业 | 1621篇 |
水利工程 | 1828篇 |
石油天然气 | 2486篇 |
武器工业 | 540篇 |
无线电 | 3368篇 |
一般工业技术 | 8092篇 |
冶金工业 | 2246篇 |
原子能技术 | 797篇 |
自动化技术 | 4499篇 |
出版年
2024年 | 188篇 |
2023年 | 738篇 |
2022年 | 1134篇 |
2021年 | 1334篇 |
2020年 | 1558篇 |
2019年 | 1376篇 |
2018年 | 1282篇 |
2017年 | 1584篇 |
2016年 | 1727篇 |
2015年 | 1753篇 |
2014年 | 2499篇 |
2013年 | 2741篇 |
2012年 | 2945篇 |
2011年 | 3317篇 |
2010年 | 2672篇 |
2009年 | 2857篇 |
2008年 | 2817篇 |
2007年 | 3266篇 |
2006年 | 2943篇 |
2005年 | 2559篇 |
2004年 | 2043篇 |
2003年 | 1830篇 |
2002年 | 1502篇 |
2001年 | 1306篇 |
2000年 | 1077篇 |
1999年 | 942篇 |
1998年 | 759篇 |
1997年 | 710篇 |
1996年 | 544篇 |
1995年 | 468篇 |
1994年 | 423篇 |
1993年 | 312篇 |
1992年 | 279篇 |
1991年 | 241篇 |
1990年 | 222篇 |
1989年 | 203篇 |
1988年 | 127篇 |
1987年 | 68篇 |
1986年 | 59篇 |
1985年 | 59篇 |
1984年 | 62篇 |
1983年 | 46篇 |
1982年 | 36篇 |
1981年 | 16篇 |
1980年 | 15篇 |
1979年 | 20篇 |
1978年 | 7篇 |
1976年 | 6篇 |
1975年 | 7篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
氟挥发对氟化物乳白玻璃瓶罐生产的影响陆德明,周俊梅,付希英(山东轻工业学院250100)(山东德州玻璃厂253019)TheInfluenceofFluorineVolatilizationonProductionofFluorideopalGlas... 相似文献
93.
J. G. Blencoe S. E. Drummond J. C. Seitz B. E. Nesbitt 《International Journal of Thermophysics》1996,17(1):179-190
A vibrating U-tube apparatus has been developed for determining the densities of pure fluids and fluid mixtures at 10-200 MPa and 323-773 K. Measured parameters areP,T, andr (period of vibration). Fluids are injected into the U-tube at constantP andT. Three or more reference fluids are used to calibrate the response of the instrument. Fluid mixtures are produced by pumping pure fluids into T-junctions on the upstream side of the U-tube using high accuracy syringe pumps. An automated syringe pump is used to maintainP at setpoint ±0.01 MPa.T is controlled to ±0.01 K using a closed-loop, electronic signal amplification/feedback system. For mixtures, a statistically significant number of measurements of r are obtained to account for the effects of small heterogeneities in fluid composition (generally <0.005X;). Typically, density data for 15 fluids can be obtained in a 6- to 8-h period. Considering all of the potential sources of error in the experimentation, conservative estimates of uncertainty are as follows:P, ±0.02 MPa;T, ±0.05 K;p (pure fluids), ±0.0005g.cm–3; andp (fluid mixtures), ±0.0005-0.0010g-cm–3.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A. 相似文献
94.
Measurements of saturated liquid viscosities and densities were performed on environmentally acceptable hydrochlorofluorocarbons (HCFCs), CH3CCl2F (HCFC-141b), CH3CClF2 (HCFC-142b; only for viscosity), CF3CF2CHCl2 (HCFC-225ca), and CClF2CF2CHClF (HCFC-225cb), using a capillary viscometer and a glass pycnometer in the temperature range from 273 to 353 K. The uncertainty in the measurement of viscosity is estimated to be 5% based on the comparison of the present data with those in the literature for HCFC-141b. An equation is given to represent our saturated liquid viscosity data as a function of temperature. 相似文献
95.
The Bi-system tapes and coils were prepared by the powder-in-tube method. The effect of processing and heat treatment on the properties of the tapes and coils was studied. It is found that the shearing stress produced by the rolling process may destroy the 2223 phase, and the destroyed 2223 phase cannot be recovered by heat treatment, whereas the pressing stress produced by the uniaxial pressing process only makes the 2223 phase grains break, and the broken 2223 phase can be closed by the heat treatment. TheJ
c values of the rolling samples, pressing sample, and the coil with a diameter of 35 mm are over 1.3×104, 2.5×104, and 4×103 A/cm2 (77 K, 0 T), respectively. 相似文献
96.
An elastic half plane with an oblique edge crack is considered in this paper. A pair of concentrated forces or point dislocations is assumed to act at an arbitrary point in the half plane. The half plane with an edge crack is first mapped into a unit circle by a rational mapping function so that the following analysis can be carried out on the mapped plane analytically. Then the complex stress functions are derived by separating the whole problem into two parts; one is the principal part corresponding to the infinite plane acted on by concentrated forces or dislocations, the other is the holomorphic part, which can be determined by making use of the property of regularity of complex stress functions. The stress intensity factors of the crack can be calculated with different inclined angles of the crack, and the displacement and stress components at an arbitrary position in the half plane can be expressed explicitly. 相似文献
97.
在工业生产条件下,对影响HPb59-1水平连铸律材热轧开裂的熔铸工艺进行了试验研究.取三个熔铸工艺因素:铸造速度、冷却水压力、冷却水温度.试验结果表明;铸造速度对热轧开裂影响极为显著,使其控制在410mm/min左右可获得较为理想的效果. 相似文献
98.
A two-dimensional cross-section finite difference model is presented to simulate density dependent leachate migration in leaky aquifers. Unlike existing models, a new approach is adopted to couple the groundwater-flow equation and the hydrodynamic dispersion equation with the elimination of the intermediate step of calculating velocities. The concept of the reference density is employed, permitting increased accuracy (over pressure-based models) in the representation of the transport process. The model is then used to study the effect of several hydraulic and transport parameters on the flow pattern and plume migration which are found to be very sensitive to most of these parameters. Equiconcentration and equipotential lines are overlapped to provide a better understanding of the coupling effect. 相似文献
99.
氧化锌压敏陶瓷烧结致密化过程的研究 总被引:6,自引:0,他引:6
本文研究了氧化锌压敏陶瓷的致密化过程,结果发现只有当烧结温度升高到一定值时,试样中的ZnO粉粒产生聚集,致密化过程才开始.致密化是瓷体获得稳定电性能的基础.低熔点添加剂B2O3可以降低致密化的起始温度,而致密化过程中的等温烧结对ZnO压敏陶瓷的最大密度几乎没有影响. 相似文献
100.
An investigation of pore cracking in titanium welds 总被引:1,自引:0,他引:1
T. Khaled 《Journal of Materials Engineering and Performance》1994,3(1):21-36
Two welded Ti-6A1-4V pressure vessels leaked prematurely in service. The leaks were caused by cracks emanating from weld porosity.
The cracks originated during fabrication, with subsequent growth in service leading to the formation of the leak paths. Pore
cracking is thought to be caused by a mechanism that involves both sustained-load and cyclic contributions, with the former
being the more prominent. It is shown that the tendency for cracking is influenced by pore position and that pore size is
not a deciding factor in that regard. The factors that govern pore cracking are discussed, and the possible role of interstitial
embrittlement is assessed. 相似文献