全文获取类型
收费全文 | 22487篇 |
免费 | 1861篇 |
国内免费 | 1225篇 |
专业分类
电工技术 | 1690篇 |
综合类 | 1709篇 |
化学工业 | 3234篇 |
金属工艺 | 2167篇 |
机械仪表 | 1869篇 |
建筑科学 | 1315篇 |
矿业工程 | 1364篇 |
能源动力 | 1146篇 |
轻工业 | 1194篇 |
水利工程 | 617篇 |
石油天然气 | 783篇 |
武器工业 | 219篇 |
无线电 | 1655篇 |
一般工业技术 | 3698篇 |
冶金工业 | 663篇 |
原子能技术 | 240篇 |
自动化技术 | 2010篇 |
出版年
2024年 | 69篇 |
2023年 | 316篇 |
2022年 | 599篇 |
2021年 | 665篇 |
2020年 | 717篇 |
2019年 | 621篇 |
2018年 | 649篇 |
2017年 | 831篇 |
2016年 | 928篇 |
2015年 | 968篇 |
2014年 | 1391篇 |
2013年 | 1514篇 |
2012年 | 1567篇 |
2011年 | 1918篇 |
2010年 | 1413篇 |
2009年 | 1395篇 |
2008年 | 1210篇 |
2007年 | 1425篇 |
2006年 | 1185篇 |
2005年 | 1006篇 |
2004年 | 854篇 |
2003年 | 752篇 |
2002年 | 616篇 |
2001年 | 464篇 |
2000年 | 436篇 |
1999年 | 390篇 |
1998年 | 267篇 |
1997年 | 289篇 |
1996年 | 217篇 |
1995年 | 174篇 |
1994年 | 159篇 |
1993年 | 100篇 |
1992年 | 86篇 |
1991年 | 73篇 |
1990年 | 64篇 |
1989年 | 48篇 |
1988年 | 36篇 |
1987年 | 16篇 |
1986年 | 23篇 |
1985年 | 18篇 |
1984年 | 14篇 |
1983年 | 24篇 |
1982年 | 26篇 |
1981年 | 5篇 |
1980年 | 11篇 |
1979年 | 3篇 |
1978年 | 7篇 |
1977年 | 4篇 |
1975年 | 4篇 |
1960年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Sun-Jung Kim Pyeong-Seok Cho Jong-Heun Lee Chong-Yun Kang Jin-Sang Kim Seok-Jin Yoon 《Ceramics International》2008,34(4):827-831
Various compositions of gas sensing films were prepared by the combinatorial deposition of SnO2, ZnO, and WO3 sol solutions and their gas sensing behaviors were investigated. The film composition could be manipulated conveniently via the alternate dropping of different oxide sol solutions. From the correlation between film compositions and gas sensitivities, the selective detection of C2H5OH and CH3COCH3 in the presence of CO, C3H8, H2, and NO2 could be attained. In addition, the discrimination between C2H5OH and CH3COCH3, which is a challenging issue due to their similar chemical nature, becomes possible. This research demonstrates the precise design of the sensor-material composition for the selective gas detection via the combinatorial approach. 相似文献
62.
The space-time distribution of the basic kinetic parameters of a plasma is experimentally determined under conditions of expansion of plasma clusters and jets into vacuum. It is demonstrated that the dynamics and structure of plasmoids injected by pulsed erosion plasma accelerators of the electrothermal type are characterized by two successive stages or two modes of acceleration, namely, the Joule heating of electrons in the initial region of the path and the collisionless expansion of rarefied plasma. 相似文献
63.
We study low-frequency vibrations of a vibroprotective system of solid bodies formed by a roller damper and a moving load-carrying body under the action of external harmonic excitations. The dynamic equations of combined motion of the working body of the damper over the hinged roller without sliding and the load-carrying body are deduced and numerically analyzed. A new procedure is proposed for the evaluation of the optimal parameters of adjustment of roller dampers in nonlinear systems. 相似文献
64.
Toshiharu Makino Hiromitsu Kato Sung-Gi Ri Yigang Chen Hideyo Okushi 《Diamond and Related Materials》2005,14(11-12):1995
Electrical properties of homoepitaxial diamond p–n+ junction of boron (B)-doped p-type layer and phosphorus-doped n-type layer on Ib (111) diamond single crystal have been characterized. Current–voltage characteristics show a clear rectifying property with rectification ratio of over 105 at ± 10 V. From capacitance–voltage characteristics, it is found that a spatial distribution of space-charge density Ni of the p–n+ junction is not uniform and Ni at a middle region of the space-charge layer formed at zero bias voltage is higher than that of other region of the space-charge layer. This peculiar characteristic can be explained by superposition of two effects; one is the deep dopant effect due to B atoms in the p-type layer, which makes to reduce Ni at around the edge of the space-charge layer formed at zero bias voltage. The other is the compensation of B acceptors by impurity atoms diffusing during the p–n+ interface and incorporating during the growth of p-type layer, which makes to reduce Ni at the vicinity of the p–n+ interface. 相似文献
65.
Diane M. Hopkins Alan D. Jackson Kenneth Oates 《Microscopy research and technique》1991,18(2):176-182
The standardisation of frozen hydrated bulk biological specimens using gelatin standards is described. The relationship between corrected elemental X-ray counts and ionic concentration was found to be linear, and minimum detectable limits for each element are stated. Variations in uncorrected standard curves were found to be due to changes in aluminium coating thickness. There was an inverse relationship between coating thickness and elemental X-ray counts. The factors causing this are discussed. To avoid errors arising from inconsistent aluminium thickness, experimental material should only be compared with standards of similar aluminium net counts. This can be achieved most easily by mounting and analysing specimen and standard together. 相似文献
66.
预测油气田产量的β模型 总被引:4,自引:0,他引:4
通过对油气田产量变化规律进行系统研究,推导建立了预测油气田产量的β模型。该模型不但可以预测油气田产量、累积产量随生产时间的变化,而且可以预测可采储量、最高年产量及其发生的时间。实例检验该模型是可信的。 相似文献
67.
Masahiko Ogura Norikazu Mizuochi Satoshi Yamasaki Hideyo Okushi 《Diamond and Related Materials》2005,14(11-12):2023
The deuterium (hydrogen) passivation effect on acceptors in boron-doped CVD homoepitaxial diamond was studied by electrical (Hall-effect) and secondary ion mass spectroscopy (SIMS) measurements. Deuterium was incorporated into the samples using microwave (MW) deuterium plasma at 673 K for 2–24 h. We observed the progress of acceptor passivation with p-type conduction, which finally resulted in a highly resistive state. 相似文献
68.
In this paper, a sensor system, called a fuzzy pulse discriminator, is developed to classify various discharge pulses in electrical discharge machining (EDM). The fuzzy rules of the pulse discriminator are obtained based on the features of the gap voltage and gap current between the tool workpiece. The membership functions of the fuzzy pulse discriminator are automatically synthesized by using genetic algorithms. The effectiveness of this approach is verified under different cutting parameters. 相似文献
69.
Mgidi Donald Dlamini 《Solar Energy Materials & Solar Cells》1996,43(4):353
In this paper results on surface photovoltage (SPV) and electron beam induced conductivity (EBIC) studies of edge-defined film-fed growth (EFG) and floating zone (FZ) silicon solar cell materials (both p-type) are presented. A systematic comparison based on minority carrier diffusion length and carrier recombination is made between: (i) samples contaminated with Ti and/or Fe, (ii) samples gettered by phosphorous diffusion, and (iii) as-received samples. Deep level transient spectroscopy (DLTS) measurements, together with the iron-boron (FeB) pairing kinetics [1] have successfully been used to detect the presence of Fe in the samples. Even though this process is effective in revealing Fe impurities in p-type FZ silicon it is evidently not suitable for Fe identification in p-type EFG silicon. Ti, like Fe, is found to be a prominent lifetime-limiting metallic impurity in both EFG and FZ silicon. Phosphorous diffusion is proven to be an effective external gettering technique for fast-diffusing impurities such as Fe, but not for Ti. 相似文献
70.
一类动态大系统的协调控制模型 总被引:12,自引:0,他引:12
讨论了一类离散动态大系统的协调控制问题,提出了相应的模型辨识方法及自适应协调控制算法。通过仿真实例,说明效果是良好的。 相似文献