全文获取类型
收费全文 | 1998篇 |
免费 | 69篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 37篇 |
综合类 | 3篇 |
化学工业 | 379篇 |
金属工艺 | 46篇 |
机械仪表 | 51篇 |
建筑科学 | 35篇 |
矿业工程 | 3篇 |
能源动力 | 94篇 |
轻工业 | 91篇 |
水利工程 | 5篇 |
石油天然气 | 16篇 |
无线电 | 336篇 |
一般工业技术 | 451篇 |
冶金工业 | 288篇 |
原子能技术 | 20篇 |
自动化技术 | 221篇 |
出版年
2023年 | 16篇 |
2022年 | 34篇 |
2021年 | 56篇 |
2020年 | 43篇 |
2019年 | 42篇 |
2018年 | 66篇 |
2017年 | 58篇 |
2016年 | 53篇 |
2015年 | 32篇 |
2014年 | 70篇 |
2013年 | 140篇 |
2012年 | 94篇 |
2011年 | 90篇 |
2010年 | 64篇 |
2009年 | 75篇 |
2008年 | 71篇 |
2007年 | 83篇 |
2006年 | 61篇 |
2005年 | 41篇 |
2004年 | 46篇 |
2003年 | 44篇 |
2002年 | 51篇 |
2001年 | 32篇 |
2000年 | 30篇 |
1999年 | 39篇 |
1998年 | 96篇 |
1997年 | 60篇 |
1996年 | 53篇 |
1995年 | 50篇 |
1994年 | 39篇 |
1993年 | 30篇 |
1992年 | 32篇 |
1991年 | 27篇 |
1990年 | 28篇 |
1989年 | 17篇 |
1988年 | 25篇 |
1987年 | 10篇 |
1986年 | 13篇 |
1985年 | 13篇 |
1984年 | 14篇 |
1983年 | 15篇 |
1982年 | 11篇 |
1981年 | 12篇 |
1980年 | 5篇 |
1979年 | 16篇 |
1978年 | 14篇 |
1977年 | 8篇 |
1976年 | 20篇 |
1975年 | 6篇 |
1973年 | 11篇 |
排序方式: 共有2076条查询结果,搜索用时 750 毫秒
151.
Banerjee Amit Mishra P. R. Mohanty Ashok Chakravarty K. Das Biswas R. Sahu R. Chakravarty S. 《国际煤炭科学技术学报(英文)》2016,3(2):97-103
International Journal of Coal Science & Technology - Mineral phase characterization and thorough understanding of its transformation behavior during combustion are imperative to know the... 相似文献
152.
From 2002 to 2010 inclusive we monitored concentrations of arsenic (As) and major ions (Ca, Mg, Sr, Na, K, Fe, Mn, Cl, and SO4) in groundwater from 14 domestic wells and three piezometer nests in a shallow aquifer (<60 m depth), and 3 wells in a deep aquifer (>70 m depth), in southern West Bengal, India. In the deep aquifer, concentrations of As did not change over time despite increases in the concentration of Fe in two wells. The shallow aquifer occurs in two sedimentological settings: palaeo-channel and palaeo-interfluve. At the top of the shallow aquifer of the palaeo-channel, decreases in all constituent concentrations with time, and an 3H/3He age of 1.4 years, proves that the aquifer is beginning to be flushed of pollutants. In As-polluted groundwater (>50 μg/L As) tapped from deeper grey sands of the shallow, palaeo-channel, aquifer, concentrations of As were mostly stable over time, but both increases and decreases occurred with time in response to downward migration of the chemically-stratified water column. In groundwater tapped from Pleistocene brown sands, the concentration of As remained either low and stable (<2 μg/L As), or increased at rates up to 34 μg/L per year. The increases were caused by the flow of As-rich groundwater either downward into brown sand at the base of palaeo-channels, or laterally into a confined, unpolluted, palaeo-interfluvial, aquifer of brown sand that lies regionally beneath a palaeosol.Under the present pumping regime, the prognosis for As-pollution in the shallow aquifer is complex. Wells in brown sand may become polluted over timescales of as little as 2 years, whilst some wells tapping As-polluted groundwater from grey sand will become fit for potable use (<50 μg/L) within a few decades. The evidence of flushing, and of declining As in some of the groundwater from palaeo-channels, which are conduits for recharge of the confined, As-free, palaeo-interfluve aquifer, and probably also the deeper aquifer, offers hopes that the spread of As-pollution will be limited. 相似文献
153.
Sanjib Banerjee 《Polymer》2010,51(6):1258-5572
Living cationic polymerization of styrene was achieved with a series of initiating systems consisting of a HX-styrenic monomer adduct (X = Br, Cl) and ferric chloride (FeCl3) in conjunction with added salts such as tetrabutylammonium halides (nBu4N+Y−; Y− = Br−, Cl−, I−) or tetraalkylphosphonium bromides [nR′4PBr; R′ = CH3CH2-, CH3(CH2)2CH2-, CH3(CH2)6CH2-] or tetraphenylphosphonium bromide [(C6H5)4PBr] in dichloromethane (CH2Cl2) and in toluene. Comparison of the molecular weight distributions (MWDs) of the polystyrenes prepared at different temperatures (e.g., −25 °C, 0 °C and 25 °C) showed that the polymerization is better controlled at ambient temperature (25 °C). The polymerization was almost instantaneous (completed within 1 min) and quantitative (yield ∼100%) in CH2Cl2. In CH2Cl2, polystyrenes with moderately narrow (Mw/Mn ∼ 1.33-1.40) and broad (Mw/Mn ∼ 1.5-2.4) MWDs were obtained respectively with and without nBu4N+Y−. However, in toluene, the MWDs of the polystyrenes obtained respectively with and without nBu4N+Y−/nR′4P+Br− were moderately narrow (Mw/Mn = 1.33-1.5) and extremely narrow (Mw/Mn = 1.05-1.17). Livingness of this polymerization in CH2Cl2 was confirmed via monomer-addition experiment as well as from the study of molecular weights of obtained polystyrenes prepared simply by varying monomer to initiator ratio. A possible mechanistic pathway for this polymerization was suggested based on the results of the 1H NMR spectroscopic analysis of the model reactions as well as the end group analysis of the obtained polymer. 相似文献
154.
155.
A generalized analytical model based on multistage scattering phenomena has been developed in this paper for estimating the impact ionization rate of charge carriers in semiconductors. The probabilities of impact ionization initiated by electrons and holes have been calculated separately by taking into account all possible combinations of optical phonon scattering and carrier-carrier collisions prior to the impact ionization. Finally the analytical expressions of impact ionization rate of electrons and holes have been developed by using the aforementioned impact ionization probabilities. The impact ionization rates of electrons and holes in 4H-SiC have been calculated within the field range of \(2.5\times 10^{8}\) – \(6.5\times 10^{8}\hbox { V m}^{-1}\) by using the analytical expressions of those developed in the present paper. Those are also calculated by using the analytical expressions developed by some other researchers earlier without considering the multistage scattering phenomena. Finally the theoretical results obtained from the analytical model proposed in this paper and the analytical model developed by earlier researchers within the field range under consideration have been compared with the ionization rate values calculated by using the empirical relations fitted from the experimentally measured data. Closer agreement with the experimental data has been achieved when the impact ionization rate of charge carriers in 4H-SiC are calculated from the proposed model as compared to the earlier one. 相似文献
156.
Optical control of large-signal properties of millimeter-wave and sub-millimeter-wave DDR Si IMPATTs
Aritra Acharyya Suranjana Banerjee J. P. Banerjee 《Journal of Computational Electronics》2014,13(2):408-424
The authors have proposed a complete large-signal (L-S) model to investigate the optical modulation of high frequency properties of double-drift region (DDR) impact avalanche transit time (IMPATT) devices operating at different millimeter-wave and sub-millimeter-wave frequencies. Simulation is carried out based on the proposed model to study the effect of photo-irradiation of different values of incident optical power of different wavelengths from 600–1000 nm on the DC and L-S characteristics of DDR IMPATTs based on Si designed to operate at 94, 140, 220, 300 and 500 GHz. Two different optical illumination configurations such as top mount and flip chip are taken into account for the present study. Results show that the maximum optical tuning of L-S parameters of the device can be achieved for optical illumination of wavelength 700 nm, i.e. near the wavelength corresponding to the responsivity peak of Si in both top mount and flip chip configurations. Further, better photo-sensitivity of top mount structure is observed as compared to its flip chip counterpart. The simulation results are found to be in good agreement with the experimental results reported earlier. Suitable tunable light source information is also suggested to carry out the optical control experiment within the wavelength range under consideration. 相似文献
157.
Bakul Banerjee 《Annals of Software Engineering》2000,10(1-4):373-387
As software technologies advance, the software community uses the newest and most powerful technology and associated notations.
However, mapping software with a set of notations that would survive the test of time is becoming increasingly difficult.
A survey of current methodologies indicates that half‐lives of various software notations are short. The dependence of software
notations on programming languages and environment specific methodologies often makes these notations obsolete. In this paper,
development of a standard set of software notations that is independent of programming paradigms, yet extensible enough to
accommodate programming needs, is proposed.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
158.
We present a Path-Sum Monte Carlo method, a tight-biding approach to Path Integral Monte Carlo, as an alternative to mean-field theory for analyzing exchange-correlation effects in many-electrons systems. To test the algorithm we apply it to a small trial system of either four or six electrons confined to two parallel six single-orbital-atom rings (12 atoms and orbitals total) for which exact results are available for comparison. We observe the phase diagram for exciton formation as a function of interlayer separation and temperature, showing good agreement between the Monte Carlo and exact calculations. Moreover, although the Monte Carlo algorithm employs a fixed node approximation to avoid the Fermion sign problem and, therefore, is inexact, we consider two different limits to the fixed node approximation which provide upper and lower bounds on the total energy. While a simple system is considered here to allow the comparison with exact results, the algorithm should extend the reach of computational analysis to larger many-electrons systems such as, e.g., paired graphene layers for which room-temperature superfluidity has been predicted elsewhere. 相似文献
159.
Banerjee S. Chung-En Zah Bhat R. Caneau C. 《IEEE transactions on instrumentation and measurement》1999,48(1):45-49
Spatially resolved photoluminescence is used as a nondestructive tool to characterize semiconductor epitaxial wafers with a resolution better than the device dimensions. In this paper, we describe a novel photoluminescence measurement setup using fiber optic techniques for luminescence excitation and detection in a very simple confocal arrangement. A final spatial resolution as small as 5 μm±0.5 μm together with the compact design makes it very attractive 相似文献
160.
B. Bhatia H. L. Sarkar D. K. Banerjee Inamul Haq 《The International journal of environmental studies》2013,70(1-2):111-123
Four‐hourly data were collected for 24 hour periods in the months of December (1977), April (1978), July (1978) and December (1978) in respect of some physicochemical characteristics and plankton population in a protected part of the Loktak Lake (Manipur) India. Highly significant correlations, positive as well as negative, were observed between the diurnal and seasonal variations of physicochemical characteristics with those of total phyto or zooplankton of certain species. 相似文献