全文获取类型
收费全文 | 318篇 |
免费 | 9篇 |
国内免费 | 1篇 |
专业分类
化学 | 208篇 |
晶体学 | 1篇 |
力学 | 26篇 |
数学 | 30篇 |
物理学 | 63篇 |
出版年
2023年 | 2篇 |
2022年 | 6篇 |
2021年 | 7篇 |
2020年 | 9篇 |
2019年 | 4篇 |
2018年 | 8篇 |
2017年 | 7篇 |
2016年 | 7篇 |
2015年 | 3篇 |
2014年 | 13篇 |
2013年 | 20篇 |
2012年 | 28篇 |
2011年 | 34篇 |
2010年 | 8篇 |
2009年 | 15篇 |
2008年 | 17篇 |
2007年 | 13篇 |
2006年 | 13篇 |
2005年 | 22篇 |
2004年 | 14篇 |
2003年 | 13篇 |
2002年 | 9篇 |
2001年 | 3篇 |
2000年 | 5篇 |
1999年 | 6篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1971年 | 1篇 |
排序方式: 共有328条查询结果,搜索用时 421 毫秒
41.
42.
A model for predicting the effective thermal conductivity of nanofluids is proposed. It has been documented that the interfacial layer at the solid (particle)/liquid interface and particle size is one of the major mechanisms for enhancing the thermal conductivity of nanofluids. Comparing with other classical models, the proposed model takes into account some additional effects including volume fraction, thickness, thermal conductivity of the interfacial layer and particle size. The proposed model is found to be better than the existing models since the predicted effective thermal conductivity of different types of nanofluids are closer to the experimental results. 相似文献
43.
Partial purification of acid pyrophosphatase activity from dried red kidney beans was achieved. The crude enzyme was found
to adhere to plastic and was very unstable. These problems were solved by extraction with low pH and high-ionic-strength buffers.
This extraction procedure separated acid pyrophosphatase activity into three parts. One of these activities appears to correspond
to the purple phosphatase isolated by other workers (1—3). The other two fractions showed both general phosphomonoesterase
and pyrophosphatase activity, but were most active with pyrophosphate and were used for further characterization. The pH optimum
for the enzyme was approx 5.5-6.0 with pyrophosphatase, and it exhibited substrate inhibition with pyrophosphate and ATP at
low pH. The partially purified acid pyrophosphatase was estimated to be a dimer of approx 98 kDa (mol wt estimated by gel
filtration on Sephacryl S-200) with no detectable carbohydrate or iron content. Of the cations tested for their effect on
pyrophosphatase activity, iron was the most inhibitory, followed by magnesium and zinc. 相似文献
44.
Boon Leong Lan 《International Journal of Theoretical Physics》2008,47(10):2686-2689
Contrary to conventional view, it is shown that, for an ensemble of either single-particle systems or multi-particle systems,
the realistic interpretation of a mathematical superposition of states that mathematically describes the ensemble does not
imply that the ensemble is a mixture. Therefore it cannot be argued, as is conventionally done, that the realistic interpretation
is wrong on the basis that some predictions derived from the mixture are different from the corresponding predictions derived
from the mathematical superposition of states. 相似文献
45.
LetLbe a Moufang loop of odd orderpαqα11···qnαnwherepandqiare primes with 3 ≤ p < q1 < ··· < qnand αi ≤ 2. In this paper, we prove thatLis a group ifpandqiare primes with 3 ≤ p < q1 < ··· < qn: (i) α ≤ 3, or (ii) α ≤ 4,p ≥ 5. 相似文献
46.
47.
Terminal phosphino groups of [Re2(CO)9(η1-P-P)] (P-P = diphosphines) are activated towards oxidation by Me3NO. The respective reactions of Me3NO with [Re2(CO)9{η1-P(o-anisyl)2(CH2)3PPh2}], [Re2(CO)9{η1-PPh2(CH2)3P(o-anisyl)2}] and [Re2(CO)9(η1-trans-PPh2CHCHPPh2)] were studied to investigate the mechanism of this oxidation. The results are consistent with an intramolecular pathway involving a cyclic intermediate, without exchange of the coordinated and terminal phosphino groups. A mechanism which involves an interaction of the terminal phosphino group with a carbonyl ligand is proposed. In sharp contrast to eq-[Re2(CO)9(η1-P-P)] (P-P = Ph2P(CH2)nPPh2, n = 1-6), eq-[Re2(CO)9(η1-trans-PPh2CHCHPPh2)] appears to be indefinitely stable towards equatorial → axial isomerization at room temperature, thus, allowing its crystal structure to be determined. 相似文献
48.
Leong M. Gan Chwee H. Chew Stig E. Friberg 《Journal of polymer science. Part A, Polymer chemistry》1983,21(2):513-523
The solubility of styrene, its oligomers, and different molecular weight polymers was determined in W/O microemulsions stabilized by sodium dodecyl sulfate and pentanol. The results showed a complex pattern due to the interactions with pentanol, surfactant, and associated structures. 相似文献
49.
This work considers an electrically conducting fluid filled between two concentric cylindrical walls relatively close to each other. A theoretical solution for the steady Taylor–Couette flow between these two electrically insulated rotating cylinders under the influence of a radial magnetic field is provided in this work. By solving the appropriate set of governing equations simultaneously, the profiles of fluid tangential velocity component and induced magnetic field were obtained as complicated functions involving the modified Bessel functions of the first and second kinds of the first-order in terms of radial coordinates and Hartmann number. A computational study was also performed to validate the present theoretical solution. The analytical and computational results are identical when Ha = 1 while these results only slightly deviate from each other as Ha increases. Current results show that, the presence of the external magnetic field causes the flow close to the slower cylinder to accelerate while that close to the faster cylinder to decelerate. This has clearly implied the fact that an external magnetic field tends to make the velocity distribution across the inner and outer cylinders more uniform. 相似文献
50.
Let 𝔽 be a field of characteristic two. Let S n (𝔽) denote the vector space of all n?×?n symmetric matrices over 𝔽. We characterize i. subspaces of S n (𝔽) all whose elements have rank at most two where n???3, ii. linear maps from S m (𝔽) to S n (𝔽) that sends matrices of rank at most two into matrices of rank at most two where m, n???3 and |𝔽|?≠?2. 相似文献