全文获取类型
收费全文 | 147篇 |
免费 | 0篇 |
国内免费 | 1篇 |
专业分类
化学 | 116篇 |
力学 | 7篇 |
数学 | 12篇 |
物理学 | 13篇 |
出版年
2022年 | 19篇 |
2021年 | 9篇 |
2020年 | 2篇 |
2019年 | 1篇 |
2017年 | 7篇 |
2016年 | 2篇 |
2015年 | 8篇 |
2014年 | 6篇 |
2013年 | 11篇 |
2012年 | 7篇 |
2011年 | 15篇 |
2010年 | 3篇 |
2009年 | 5篇 |
2008年 | 2篇 |
2007年 | 2篇 |
2006年 | 4篇 |
2005年 | 4篇 |
2004年 | 2篇 |
2003年 | 3篇 |
2002年 | 4篇 |
2001年 | 3篇 |
2000年 | 5篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1993年 | 5篇 |
1992年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有148条查询结果,搜索用时 0 毫秒
51.
52.
Monasnicotinates A-D, four new pyridine alkaloids from the fungal strain Monascus pilosus BCRC 38093
Wu MD Cheng MJ Yech YJ Chen YL Chen KP Chen IS Yang PH Yuan GF 《Molecules (Basel, Switzerland)》2011,16(6):4719-4727
Four new pyridine derivatives, monasnicotinates A-D (1-4) were isolated from the red yeast rice of Monascus pilosus BCRC 38093. Their structures were elucidated on the basis of physicochemical evidence, in-depth NMR spectroscopic analysis, and high-resolution mass spectrometry. Their inhibitory effects on NO production was also evaluated. 相似文献
53.
This study conducts an experimental study concerning the improvement of nozzle/diffuser micropump design using some novel no-moving-part valves. A total of three micropumps, including two enhancement structures having two-fin or obstacle structure and one conventional micro nozzle/diffuser design, are made and tested in this study. It is found that dramatic increase of the pressure drops across the designed micro nozzles/diffusers are seen when the obstacle or fin structure is added. The resultant maximum flow rates are 47.07 mm3/s and 53.39 mm3/s, respectively, for the conventional micro nozzle/diffuser and the added two-fin structure in micro nozzle/diffuser operated at a frequency of 400 Hz. Yet the mass flow rate for two-fin design surpasses that of conventional one when the frequency is below 425 Hz but the trend is reversed with a further increase of frequency. This is because the maximum efficiency ratio improvement for added two-fin is appreciably higher than the other design at a lower operating frequency. In the meantime, despite the efficiency ratio of the obstacle structure also reveals a similar trend as that of two-fin design, its significant pressure drop (flow resistance) had offset its superiority at low operating frequency, thereby leading to a lesser flow rate throughout the test range. 相似文献
54.
T.Y. Pai G.S. Shyu L. Chen H.M. Lo D.H. Chang W.J. Lai P.Y. Yang C.Y. Chen Y.C. Liao S.C. Tseng 《Applied Mathematical Modelling》2013
A mathematical model was established to describe the transportation and transformation of nitrogen compounds in the sewer pipe. In order to verify the consistency between the experimental data and model simulation data, four runs of experiments were carried out in a 21 m long, 0.15 m diameter model sewer. The results showed a good consistency between the experimental and simulation values (all correlation coefficients >0.81). According to the good consistency, it was proved that the attached heterotrophic biofilm on the sewer bottom played a dominant role on degradation of compounds in the system. Readily biodegradable substrate (SS) decreased with the test time due to aerobic and anoxic growth of heterotrophs. Ammonia and ammonium nitrogen (SNH) increased with the test time. But nitrate and nitrite nitrogen (SNO) and soluble organic nitrogen (SND) decreased. Dissolved oxygen (SO) declined due to the microbial consumption and subsequently increased due to reaeration, forming a sag curve. Furthermore, the transformation pathways of different compounds were identified in this study. 相似文献
55.
Wei‐Lin Su Hsiu‐Ping Huang Wei‐Ting Chen Wen‐Yi Hsu Hsi‐Yen Chang Szu‐Yu Ho Shao‐Pin Wang Shin‐Guang Shyu 《中国化学会会志》2011,58(2):163-173
Carbonyls' 2π orbital populations, [2π], in W(CO)5L {L = PPh3, PPh2Me, PPhMe2} have been determined by NMR spin‐lattice relaxation techniques. Experimental values of axial [2π], compared with those reported for PMe3 and P(OMe)3, reveal that PMe3 is a slightly better π‐acid than PPh3. Through space interactions between carbonyl and phenyl groups are insignificant since values of [2π] do not vary significantly in the series of phosphines, going from PMep3 to PPh3. Natural bond orbital (NBO) studies indicate that π‐accepting capabilities for these phosphines are primarily governed by the nature of P‐C anti‐bonding, σ*P‐C. Compared with PPh3, the better π‐accepting σ*P‐C, as well as the better s‐donating lone‐pair LP(P), in PMe3 can both be explained by the higher extents of rehybridization of the coordinated phosphorus atom. Based on this rehybridization argument, the NBO predicted order of increasing π‐acidic strengths PPh3 < PPh2Me < PPhMe2 < PMe3, which cannot be clearly distinguished by NMR experiments, is ascribed to the same NBO trend of σ‐donating capabilities in a synergistic manner. Effects of coordination on P‐Y (Y = C, O, F) bonding strengths in phosphines (or phosphites) are depending on two conflicting effects: rehybridization of LP(P) and the hyperconjugative‐like dπ → σ*P‐Y back‐donation. 相似文献
56.
Guor-Shiarn Shyu Nishawn S. M. Hanif Kenneth R. Hall Philip T. Eubank 《Fluid Phase Equilibria》1997,130(1-2):73-85
A model based upon the Peng-Robinson equation of state with the Wong-Sandler mixture combining rule (W-S MCR) can correlate phase equilibria in CO2 + H2O. The W-S MCR requires two energy parameters for liquid behavior and one interaction parameter for gas behavior, kij. In this paper, we present expressions for the energy parameters which cover a wide temperature range, and we use a new procedure to obtain kij by relating it to experimental cross second virial coefficients, Bij. The three-phase pressures calculated for this system using our proposed model agree with the experimental data within a fraction of 1 bar. The correlated phase behavior of CO2 + H2O appears to be accurate over the ranges 1 – 1000 bar and 298.15–623.15 K. The proposed model also confirms the advantage of using the W-S MCR for phase equilibrium calculations. 相似文献
57.
Shyu Jiann-Shing 《中国化学会会志》1992,39(1):27-34
The most recent ab initio potentials for H2(1∑g+), which include relativistic, adiabatic and radiative corrections, were used to calculate the spectrum of quasibound states. The levels, widths and tunneling permeability of resonant states were also studied by the quantum phase-shift method. A new set of relevant resonance states for the calculations of atomic recombination of hydrogen is indicated by the present work. In comparison with the previous studies, significant improvements have been found for the resonances. 相似文献
58.
A biodegradable GTP composite composed of OPCs crosslinked gelatin with tricalcium phosphate was prepared as a novel bone substitute. The effects of the degree of crosslinking on the swelling ratio, in vitro degradation rate, and morphology of the GTP composite are discussed. Adding OPCs to GP and GTP composites markedly reduced the degradation rate, indicating that OPCs are good crosslinking reagents for gelatin. Cytotoxic tests demonstrated that OPCs, gelatin and tricalcium phosphate released from GTP composite promoted the proliferation of MG-63 cells. Results of this study suggest that the nontoxic GTP composite is suitable for use as a large defect bone substitute. 相似文献
59.
60.
Secondary resonances of a slender, elastic, cantilevered beam subjected to a transverse harmonic load are investigated. The effects of nonlinear curvature, nonlinear inertia, viscous damping and static load are included. Cubic terms in the governing equations lead to subharmonic and superharmonic resonances of order three. The static displacement produced by the weight of the beam introduces quadratic terms in the governing equations, which cause subharmonic and superharmonic resonances of order two. Out-of-plane motion is possible in all of these secondary resonances when the principal moments of inertia of the beam cross section are approximately equal. 相似文献