全文获取类型
收费全文 | 2520篇 |
免费 | 79篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 31篇 |
综合类 | 4篇 |
化学工业 | 612篇 |
金属工艺 | 80篇 |
机械仪表 | 62篇 |
建筑科学 | 45篇 |
能源动力 | 103篇 |
轻工业 | 76篇 |
水利工程 | 16篇 |
石油天然气 | 2篇 |
无线电 | 501篇 |
一般工业技术 | 408篇 |
冶金工业 | 262篇 |
原子能技术 | 21篇 |
自动化技术 | 381篇 |
出版年
2023年 | 5篇 |
2022年 | 27篇 |
2021年 | 47篇 |
2020年 | 19篇 |
2019年 | 27篇 |
2018年 | 41篇 |
2017年 | 34篇 |
2016年 | 45篇 |
2015年 | 41篇 |
2014年 | 83篇 |
2013年 | 206篇 |
2012年 | 134篇 |
2011年 | 149篇 |
2010年 | 136篇 |
2009年 | 153篇 |
2008年 | 148篇 |
2007年 | 112篇 |
2006年 | 107篇 |
2005年 | 91篇 |
2004年 | 82篇 |
2003年 | 70篇 |
2002年 | 68篇 |
2001年 | 50篇 |
2000年 | 48篇 |
1999年 | 51篇 |
1998年 | 105篇 |
1997年 | 67篇 |
1996年 | 56篇 |
1995年 | 38篇 |
1994年 | 38篇 |
1993年 | 29篇 |
1992年 | 32篇 |
1991年 | 21篇 |
1990年 | 20篇 |
1989年 | 26篇 |
1988年 | 18篇 |
1987年 | 17篇 |
1985年 | 18篇 |
1984年 | 17篇 |
1983年 | 11篇 |
1982年 | 9篇 |
1981年 | 9篇 |
1980年 | 9篇 |
1979年 | 11篇 |
1978年 | 5篇 |
1977年 | 15篇 |
1976年 | 12篇 |
1975年 | 13篇 |
1973年 | 8篇 |
1967年 | 5篇 |
排序方式: 共有2604条查询结果,搜索用时 31 毫秒
11.
MT Yeh TN Mather RT Coughlin C Gingrich-Baker JW Sumner RF Massung 《Canadian Metallurgical Quarterly》1997,35(4):944-947
A new indirect fluorescent-antibody (IFA) assay with antigen produced in vitro in the human promyelocytic leukemia cell line HL60 was used to identify the first recognized case of human granulocytic ehrlichiosis in Rhode Island. This IFA assay was used to detect granulocytic ehrlichiae in white-footed mice and in a dog inhabiting the area surrounding the patient's residence. Host-seeking Ixodes scapularis ticks found in the same habitat also were infected. I. scapularis ticks collected from other locations were fed on dogs and New Zealand White rabbits to assess the competency of these species as hosts of granulocytotropic Ehrlichia. Tick-induced infections of dogs were confirmed by serologic testing, tissue culture isolation, and PCR amplification, whereas several rabbits seroconverted but were PCR and culture negative. PCR amplification of the 16S rRNA gene and DNA sequencing of the PCR products or culture isolation was used to confirm granulocytic Ehrlichia infections in humans, dogs, white-footed mice, and ticks. 相似文献
12.
The dc and ac electrical conduction properties have been investigated in four composites containing hydroxyl-terminated polybutadiene (HTPB) as binder and different proportions of aluminum particles as filler in a temperature range of -60 to +70°C and a frequency range of 40 Hz to 100 kHz. A change in conduction mechanism at a temperature of 4±3°C was displayed explicitly in de measurements. The transition was shown to be due to crystallization of the HTPB upon cooling. dc conduction is explained in terms of ionic hopping in HTPB. Distinct polarization mechanisms, below and above the transition temperature, have been identified as interfacial polarisation and electrode blocking effect, respectively. The change of conduction behaviors at the crystallization temperature, 4±3°C, was not revealed explicitly in ac measurements. However, using the free volume concept to analyze the frequency shift factor aT, a discontinuity in the fractional free volume curve was displayed. The temperature of the break point, 6.7°C, corresponds to the crystallization temperature of HTPB. The study showed that the crystallization of a polymer is accompanied by an abrupt reduction in free volume, and this structural change affects dc as well as ac conduction behaviors 相似文献
13.
14.
The behavior of a spatially smoothing adaptive array is examined. An expression for the weight vector is first derived. Using the array gain on the desired signal and the coherent interference is obtained. Then the expression for output signal-to-noise (SNR) is derived. It shows that the performance of the spatially smoothing array depends on the number of the subarrays, the angle separation, relative power and initial phase difference between the desired signal and the coherent interference. For good interference suppression it is found that the magnitude of the phase difference of the incident and interference signals must be greater than the beamwidths of both the subarray and the equivalent array. There is also a tradeoff between increasing the groups of subarrays and decreasing the number of elements in the subarrays. Computer simulation results are given that validate the analysis 相似文献
15.
Herchang Ay JiinYuh JangJer-Nan Yeh 《International Journal of Heat and Mass Transfer》2002,45(20):4069-4078
An experimental study is performed using an infrared thermovision to monitor temperature distribution over a plate-fin surface inside the plate finned-tube heat exchangers. The differentiation of the temperature function is derived to determine the local convective heat transfer coefficients on the tested fin, using a local element lumped conduction equation included the convective effect on the boundaries with experimental data. It is disclosed that the infrared thermography is capable of rapidly detecting location and extent of transition and separation regions of the boundary layer over the whole surface of the tested models. Through the comparison of the test results on the strategy region of the in-line and staggered arrangements, it is more easy to understand or interpret the detailed dynamic phenomena of flow existed in the heat exchangers. In addition, the experimental results demonstrate that the averaged heat transfer coefficient of staggered configuration is 14-32% higher than that of in-lined configuration 相似文献
16.
17.
High conductivity n-type ZnSe with = 0.01 ωcm and n = 2.4 × 1018 cm−3 is obtained on (100) GaAs substrates by low pressure organometallic chemical vapor deposition. The 14 meV full width at half maximum of the 77 K photoluminescence near-band-edge emission shows a high quality of as-grown Al-doped ZnSe epilayers. With a suitable Al doping level, a strong photoluminescence intensity of near-band-edge emission is obtained. The behavior of near-band-edge emission and of self-activated emission related to the incorporation of aluminum are discussed in this paper. 相似文献
18.
Ray P. S. Han Kai-Yuan Yeh Guoli Liu Diankui Liu 《International Journal of Engineering Science》1992,30(12):1773-1787
The scattering and diffraction of plane SH-waves, by an arbitrary-shaped cylindrical canyon in anisotropic media is formulated here. Analytical solutions are obtained via the complex function theory, using the orthogonal property of the Hermite functions to solve the resulting set of infinite algebraic equations. Expressions for scattered displacements and scattered stresses are given. Three cross-sectional profile types are used in the numerical simulation of the two-dimensional canyon topography: (a) a semi-circular profile, (b) a semi-elliptical profile and (c) a triangular profile. The results obtained in (a) and (b) are consistent with known solutions computed by Trifunac and his co-workers [1,3] using a different method. As the exact solution for (c) is not known to exist, the result given here is believed to be new and would therefore serve as a useful check for numerical analysts working in this area. 相似文献
19.
Indexed in current contents 相似文献
20.
The solubilities of ethyl palmitate, ethyl oleate, ethyl eicosapentaenoate (EPA) and ethyl docosahexaenoate (DHA) in supercritical
carbon dioxide were determined by a continuous flow method. The solubilities of fatty acid ethyl esters increased with pressure
and decreased as the temperature was increased. An empirical equation, similar to Chrastil's equation, was used to describe
the relationship between solute solubility and the density of carbon dioxide. The empirical equation was further used to qualitatively
estimate the separation efficiency of isolating EPA and DHA ethyl esters from fatty acid esters. The operating conditions
yielding high solubility gave fast extraction rate but resulted in low separation efficiency. Experiments were conducted to
separate ethyl EPA and ethyl DHA from a model mixture containing four fatty acid ethyl esters and from esterified squid visceral
oil. The experimental data compared closely with the calculated values. 相似文献