全文获取类型
收费全文 | 2964篇 |
免费 | 104篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 159篇 |
综合类 | 3篇 |
化学工业 | 823篇 |
金属工艺 | 60篇 |
机械仪表 | 83篇 |
建筑科学 | 79篇 |
能源动力 | 114篇 |
轻工业 | 366篇 |
水利工程 | 14篇 |
石油天然气 | 1篇 |
无线电 | 173篇 |
一般工业技术 | 519篇 |
冶金工业 | 269篇 |
原子能技术 | 119篇 |
自动化技术 | 296篇 |
出版年
2023年 | 23篇 |
2022年 | 34篇 |
2021年 | 80篇 |
2020年 | 28篇 |
2019年 | 38篇 |
2018年 | 83篇 |
2017年 | 55篇 |
2016年 | 106篇 |
2015年 | 52篇 |
2014年 | 92篇 |
2013年 | 184篇 |
2012年 | 164篇 |
2011年 | 187篇 |
2010年 | 140篇 |
2009年 | 168篇 |
2008年 | 188篇 |
2007年 | 136篇 |
2006年 | 119篇 |
2005年 | 121篇 |
2004年 | 100篇 |
2003年 | 94篇 |
2002年 | 91篇 |
2001年 | 64篇 |
2000年 | 46篇 |
1999年 | 53篇 |
1998年 | 124篇 |
1997年 | 79篇 |
1996年 | 62篇 |
1995年 | 39篇 |
1994年 | 47篇 |
1993年 | 46篇 |
1992年 | 18篇 |
1991年 | 19篇 |
1990年 | 11篇 |
1989年 | 19篇 |
1988年 | 18篇 |
1987年 | 17篇 |
1986年 | 16篇 |
1985年 | 19篇 |
1984年 | 13篇 |
1983年 | 15篇 |
1982年 | 9篇 |
1981年 | 4篇 |
1980年 | 8篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 12篇 |
1976年 | 10篇 |
1975年 | 5篇 |
1974年 | 5篇 |
排序方式: 共有3078条查询结果,搜索用时 31 毫秒
221.
Motohiko Umeyama Duc Hoang Nguyen Cat Vu Minh Xuan Roanh Le Satoshi Motani 《Water Resources Management》2014,28(12):3937-3955
Despite many previous investigations, there is no theoretically justifiable equation to determine the freshwater discharge, tidal velocity, and salinity in a complex estuary that contains several branches. In this study, the longitudinal distributions of freshwater and salinity concentration in multi-branched estuaries are investigated using a mathematical model, considering the energy balance by frictional head loss and the salt balance by diffusion and advection in a one-dimensional steady-state condition. We attempt to obtain the time-mean freshwater discharge rate quantitatively at a junction where the main flow separates into two branches. The salinity distribution along each branch is calculated by following the dispersion coefficient equation previously proposed for a single estuary. The salinity field is divided into the near-coast region and the upstream region, because in each segment the inland velocity varies according to the tidal flux. For computing the tidal velocity, we propose the Burgers equation and the Hoph-Cole transformation. The theoretical results obtained by these equations were found to be in good agreement with a set of observed data in the Red River estuary system. 相似文献
222.
Mui-How Phua Satoshi Tsuyuki Jung Soo Lee Mohammad A. A. Ghani 《International journal of remote sensing》2013,34(14):4312-4333
Fires associated with recurrent El Niño events have caused severe damage to tropical peat swamp forests. Accurate quantitative information about the frequency and distribution of the burned areas is imperative to fire management but is lacking in the tropics. This article examines a novel method based on principal component analysis (PCA) of the normalized difference water index (NDWI) from multisensor data for simultaneously detecting areas burned due to multiple El Niño–related fires. The principal components of multitemporal NDWI (NDWI-PCs) were able to capture the areas burned in the 1998 and 2003 El Niño fires in NDWI-PC3 and 2, respectively. The proposed method facilitates the reduction of dimensionality in detecting the burned areas. From 22 image bands, the proposed method was able to accurately detect the burned areas of multiple fires with only three NDWI-PCs. The proposed method also shows superior performance to unsupervised classifications of the principal components of combined image bands, multitemporal NDWI, NDWI differencing and post-classification comparison methods. The results show that the 1998 El Niño fire was devastating especially to intact peat swamp forest. For degraded peat swamp forest, there was an increase in the burned area from 1998 to 2003. The proposed method offers the retrieval of accurate and reliable quantitative information on the frequency and spatial distribution of burned areas of multiple fires in the tropics. This method is also applicable to the detection of changes in general as well as the detection of vegetation changes. 相似文献
223.
Hideki Kokame Kentaro Hirata Keiji Konishi Takehiro Mori 《International journal of control》2013,86(6):537-546
Supposing a non-linear system is subjected to parametric uncertainties, the present paper aims at stabilizing its unstable steady states. A distinctive feature of the problem is that exact information about the steady state is unavailable. To cope with the difficulty, we have examined the applicability of the state difference feedback which uses the difference between the present state x(t) and the past state x(t-T). A rigorous stability analysis has been executed for the case where state deviations are controllable by a single input variable. The stability analysis has led to a favourable conclusion that if the number of unstable modes is just two, and if they are not associated with the origin in the complex plane, we are always able to find a controller which stabilizes the deviations from the unknown steady state. Design process is illustrated by using two kinds of pendulum systems. 相似文献
224.
Beam-shape correction in deployable phased arrays 总被引:1,自引:0,他引:1
Yonezawa R. Konishi Y. Chiba I. Katagi T. 《Antennas and Propagation, IEEE Transactions on》1999,47(3):482-486
Deployable phased-array antennas-antennas that are receiving great attention-have a major problem in that they possess the possibility of an incomplete deployment and antenna shape distortion. These effects cause a displacement of the element antenna positions that results in deviation of the phase distribution on the antenna aperture, eventually causing antenna beam deflection. We have investigated how to correct this beam deflection by observing the phased-array antenna from certain directions. There are cases when more than one observation point is necessary to carry out the proposed method depending on the extent of the antenna shape distortion and the number of the points is consulted. This correction method makes it possible to correct the deflection of the main beam and also to determine the displacement of relative element positions 相似文献
225.
Satoshi Fukuta Keita Ogawa Masaki Nomura Mariko Yamasaki Yasutoshi Sasaki 《Holz als Roh- und Werkstoff》2017,75(3):429-437
In this study, the potential of wood-only (metal-free) load-bearing walls was proposed and tested based on the idea of using the same type of material throughout wherever possible while improving basic properties such as strength, sound insulation, and heat insulation. Specifically, a technique was tested of combining pressure sensitive adhesive tape and wood dowels in place of nails for load-bearing structures with panel reinforcement represented by wood-frame construction. For this paper, its strength was evaluated by conducting in-plane shear tests, which revealed that the initial rigidity and maximum load of the proposed test specimens were greater than that of specimens using nails for jointing. However, the shear load factor, which is calculated based on some strength parameters and which forms the foundation of housing strength design, was slightly lower than that of the nail-jointed specimen. This was because there was a large decline in post-collapse resistance and a lower calculated absorbed energy caused by brittleness. The early detachment of panels was also revealed as a problem in the tests. 相似文献
226.
Qingjun Zhu Junko N. Kondo Satoshi Inagaki Takashi Tatsumi 《Topics in Catalysis》2009,52(9):1272-1280
Aluminosilicate H/CHA and H/MTF zeolites show remarkably different catalytic activities in the methanol and ethanol transformations
although they have similar pore size of 8-membered ring structures. Moreover, the produced ethylene is further converted on
H/CHA, but H/MTF is not active for the ethylene transformation. The correlations between the distinct catalytic differences
and their intrinsic structural properties, including topology and acidity, are discussed. 相似文献
227.
Lithium-doped sulfated-zirconia catalysts for oxidative coupling of methane to give ethylene and ethane 总被引:1,自引:0,他引:1
Li-doped sulfated-zirconia catalysts were found to be effective for oxidative coupling of methane (OCM). The catalyst performances depend on the sulfate content and calcination temperature. A maximum C2 yield is attained over the catalysts, which contain 6 wt.% sulfate and calcined at 923–973 K, being closely related to the preparation conditions of sulfated-ZrO2 as solid super-acids. When the performances of the Li-doped sulfated-ZrO2 (Li/SZ) catalysts were tested at 1023 K as a function of reaction time, both the C2 and COx selectivities remained constant over the range of 8 h, but the CH4 conversion decreased from 17.5% to 11.9%. The nature of Li/SZ catalysts for the OCM was investigated by X-ray diffraction, XPS, and NH3 and CO2 TPD measurements. It could be postulated that the sulfated-ZrO2 surface could play an important role in the formation of a catalytically active structure by Li-doping. 相似文献
228.
Yuzo Nishida Satoshi Nishino Li Li Guo Mami Kunita Hideaki Matsushima Tadashi Tokii 《Inorganic chemistry communications》1999,2(12):160
We have observed that binuclear cobalt(II) compounds with H(HPTP), Co2(HPTP)(CH3COO)(ClO4)2 and Co2(HPTP)Cl(ClO4)2, react with oxygen molecules when DNA is present in the solution, cleaving the DNA (H(HPTP) denotes N,N,N′,N′-tetrakis(2-pyridylmethyl)-1,3-diaminopropane-2- ol). 相似文献
229.
Helical carbon and graphite films were prepared from iodine-doped helical polyacetylene (H-PA) film using currently developing morphology-retaining carbonization. It was found from scanning electron microscopy (SEM) observations that the hierarchical helical morphology of the H-PA film remains unchanged even after the carbonization at 800 °C. Besides, the weight loss of the film due to the carbonization was very small, which was only a few percent to the weight of the film before doping. Furthermore, the graphite film prepared by the subsequent heating at 2600 °C still retained the same morphology as those in the original H-PA film and in the helical carbon film prepared at 800 °C. X-ray diffraction (XRD) and Raman scattering measurements were then pursued. The results showed that graphitic crystallization proceeds in the carbon film through the heat treatment at 2600 °C. Transmission electron microscopy (TEM) image of a single helical graphitic fibril was also observed by ultrasonicating the graphite film in ethanol. Carbonization of the H-PA films by way of iodine doping was found to afford helical carbon and graphite films, where spiral morphologies and even helical fibril structures were completely preserved. 相似文献
230.
Satoshi Miyaguchi Shinichi Ishizuka Takeo Wakimoto Jun Funaki Yoshinori Fukuda Hirofumi Kubota Kenji Yoshida Teruichi Watanabe Hideo Ochi Tsuyoshi Sakamoto Masami Tsuchida Isamu Ohshita Teruo Tohma 《Journal of the Society for Information Display》1999,7(3):221-226
Abstract— A full-color 5.2-inch 1/4-VGA passive-matrix organic LED display has been developed, adopting selective deposition for the different emitting materials. The display features 320 (×3) × 240 pixels with an equivalent pixel size of 0.33 × 0.33 mm, white peak luminance of over 150 cd/m2, and power consumption of 6 W. 相似文献