全文获取类型
收费全文 | 73266篇 |
免费 | 8027篇 |
国内免费 | 5155篇 |
专业分类
电工技术 | 4860篇 |
技术理论 | 2篇 |
综合类 | 7725篇 |
化学工业 | 8822篇 |
金属工艺 | 6219篇 |
机械仪表 | 5290篇 |
建筑科学 | 9859篇 |
矿业工程 | 4302篇 |
能源动力 | 2591篇 |
轻工业 | 4775篇 |
水利工程 | 3336篇 |
石油天然气 | 4945篇 |
武器工业 | 648篇 |
无线电 | 4382篇 |
一般工业技术 | 9317篇 |
冶金工业 | 4411篇 |
原子能技术 | 1109篇 |
自动化技术 | 3855篇 |
出版年
2024年 | 613篇 |
2023年 | 1126篇 |
2022年 | 2846篇 |
2021年 | 3062篇 |
2020年 | 2464篇 |
2019年 | 2086篇 |
2018年 | 2019篇 |
2017年 | 2441篇 |
2016年 | 2780篇 |
2015年 | 2870篇 |
2014年 | 4221篇 |
2013年 | 4645篇 |
2012年 | 4962篇 |
2011年 | 5556篇 |
2010年 | 4215篇 |
2009年 | 4348篇 |
2008年 | 4013篇 |
2007年 | 4813篇 |
2006年 | 4254篇 |
2005年 | 3655篇 |
2004年 | 3027篇 |
2003年 | 2604篇 |
2002年 | 2293篇 |
2001年 | 1914篇 |
2000年 | 1632篇 |
1999年 | 1370篇 |
1998年 | 1136篇 |
1997年 | 964篇 |
1996年 | 853篇 |
1995年 | 685篇 |
1994年 | 585篇 |
1993年 | 441篇 |
1992年 | 392篇 |
1991年 | 278篇 |
1990年 | 251篇 |
1989年 | 227篇 |
1988年 | 176篇 |
1987年 | 120篇 |
1986年 | 70篇 |
1985年 | 54篇 |
1984年 | 69篇 |
1983年 | 27篇 |
1982年 | 42篇 |
1981年 | 24篇 |
1980年 | 27篇 |
1979年 | 25篇 |
1964年 | 21篇 |
1960年 | 14篇 |
1959年 | 22篇 |
1955年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
11.
This two-part paper presents a closed-form procedure for evaluation of estimates of local thermomechanical stress fields in two-phase fibrous composites and laminates. The first part is concerned with a unidirectional elastic laminate subjected to uniform mechanical loads and to uniform changes in temperature. Both phases are assumed to be elastic, with temperature-dependent moduli and expansion coefficients; the solution reflects the influence of thermomechanical interactions. Exact solutions are not possible for any real system, because the local geometry is not known in detail. Instead, estimates of the fields are found from a modified Mori-Tanaka approximation. Examples are presented for two SiC/Ti---Al---Nb composites. Local stresses of interest are found after cooling from fabrication to room temperature. The presence of local yielding, and the influence of coupling terms on the local stress magnitudes are examined. Extension of the results to laminated plates is presented in Part II (Dvorak, G.J., Chen, T. & Teply, J., Composites Science and Technology, 43 (1992) 359–368, this issue). 相似文献
12.
氯蜡-70是—应用广泛、性能优良的精细化工产品,其色泽是—重要的技术指标,直接影响着产品的质量和应用。本文考察了合成反应过程导致生色的因素,指出原料中含有的少量环烷烃、芳烃、杂环有机物及少量无机杂质能影响产品的色泽,实验表明温度过高,光源波长选择不当也是致色的重要原因。研究了致色的过程,提出其生色历程是按照β-消除反应机理进行的,并做了具体描述。 相似文献
13.
Taijiro Nonaka Rodney J. Clifton Taichiro Okazaki 《International Journal of Impact Engineering》1996,18(7-8):889-898
An analysis is presented of longitudinal waves in a thin elastic column. Velocity is specified at one end, and the boundary condition at the other end is expressed in terms of a range of effective impedances of an attached structure. Propagation, reflection and interference of the waves are followed by the method of characteristics. Integration of differential equations along characteristics yields the wave-induced stress, which is then applied to problems of earthquake excitation. Numerical examples are given for recorded updown ground motion of the Kobe Earthquake. 相似文献
14.
Kenji Imura 《Color research and application》2007,32(3):195-200
In this article, a new method for measuring a total spectral radiance factor of a FWA‐treated sample illuminated by a specific standard illuminant is introduced. The method replaces an unstable real fluorescent standard by a bi‐spectral luminescent radiance factor data, which works as a virtual fluorescent standard (VFS) by knowing spectral intensity distributions of illuminations applied to the sample. The method utilizes two illuminations I1 and I2 whose relative spectral intensity distributions are different from each other and synthesizes a virtual illumination presenting the identical fluorescent spectral radiance factor to that presented by the standard illuminant with the VFS of the specific bi‐spectral luminescent radiance factor by linearly combining I1 and I2 with the suitable weighting factors. The applicability of the method is examined in principle by comparing ISO brightness and CIE whiteness index of fluorescent standard paper as a test sample obtained by this new method to the assigned values. © 2007 Wiley Periodicals, Inc. Col Res Appl, 32, 195–200, 2007 相似文献
15.
16.
Johan M. Thevelein 《Yeast (Chichester, England)》1994,10(13):1753-1790
17.
M. Nishida T. Hanabusa Y. Ikeuchi N. Minakawa 《Materialwissenschaft und Werkstofftechnik》2003,34(1):49-55
Stress measurement methods using neutron and X‐ray diffraction were examined by comparing the surface stresses with internal stresses in the continuous tungsten‐fiber reinforced copper‐matrix composite. Surface stresses were measured by X‐ray stress measurement with the sin2ψ method. Furthermore, the sin2ψ method and the most common triaxal measurement method using Hooke's equation were employed for internal stress measurement by neutron diffraction. On the other hand, microstress distributions developed by the difference in the thermal expansion coefficients between these two phases were calculated by FEM. The weighted average strains and stresses were compared with the experimental results. The FEM results agreed with the experimental results qualitatively and confirmed the importance of the triaxial stress analysis in the neutron stress measurement. 相似文献
18.
The fracture stress of chemical vapour deposited diamond 总被引:2,自引:0,他引:2
C. S. J. Pickles 《Diamond and Related Materials》2002,11(12):492-1922
The factors which control the fracture stress of chemical vapour deposited diamond have been studied using the 3-point bend geometry. Fracture stress values of 300–800 MPa for the growth side and 600–1200 MPa for the nucleation side were recorded for samples of thickness 0.4–2.4 mm. A Weibull modulus of 23 was calculated for the growth surface data, showing that the fracture stress variability was low for a brittle material. A theory based on these results demonstrates that the material behaviour is remarkably simple, depending only on the grain size and the sample thickness, regardless of wide variations in other parameters such as optical transmission and stress state. The paper also contains a possible explanation for this well-defined behaviour based on microstress variations resulting from differences in defect density in different growth sectors within a grain. 相似文献
19.
This paper deals with a new boundary element method for analysis of the quasistatic problems in coupled thermoelasticity. Through some mathematical manipulation of the Navier equation in elasticity, the heat conduction equation is transformed into a simpler form, similar to the uncoupled-type equation with the modified thermal conductivity which shows the coupling effects. This procedure enables us to treat the coupled thermoelastic problems as an uncoupled one, A few examples are computed by the proposed BEM, and the results obtained are compared with the analytical ones available in the literature, whereby the accuracy and versatility of the proposed method are demonstrated. 相似文献
20.
S. H. Ahmad 《Polymer International》1992,28(4):291-294
Measurement of the flow stress of high density polyethylene (HDPE) and nylon 66 at strain rates of 103 s?1 using a split Hopkinson pressure bar technique is discussed. The flow stress at a strain of 10% has been determined for both polymers at 20°C. The intrinsic errors involved in this technique are briefly reviewed. The results indicate that the flow stress of HDPE and nylon 66 were 50MPa and 150MPa, respectively, at strain rates of about 103s?1. 相似文献