全文获取类型
收费全文 | 148篇 |
免费 | 3篇 |
专业分类
化学 | 84篇 |
力学 | 9篇 |
数学 | 12篇 |
物理学 | 46篇 |
出版年
2023年 | 2篇 |
2022年 | 6篇 |
2021年 | 5篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2015年 | 4篇 |
2014年 | 3篇 |
2013年 | 12篇 |
2012年 | 8篇 |
2011年 | 9篇 |
2010年 | 13篇 |
2009年 | 5篇 |
2008年 | 4篇 |
2007年 | 9篇 |
2006年 | 12篇 |
2005年 | 3篇 |
2004年 | 3篇 |
2002年 | 1篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 5篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1982年 | 2篇 |
1980年 | 3篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有151条查询结果,搜索用时 20 毫秒
1.
Gravimetric measurements of thermodesorption of n-hexane and n-heptane were performed under quasi-equilibrium conditions. Differential thermodesorption profiles for ZSM-5 and ZSM-11 showed two peaks, but for Y zeolites, only one thermodesorption peak was observed. A model function, derived from the Langmiur adsorption model, was fitted to the experimental data, and the model parameters (the adsorption entropy and enthalpy) were estimated. The two-step desorption profiles observed for ZSM-5 and ZSM-11 were attributed to the commensurate freezing effect, i.e. a transition in the adsorbed phase resulting in ordering of the adsorbed molecules in the zeolite channels. The results observed for ZSM-11 indicate that the zigzag channels typical for ZSM-5 micropore system are not necessary for this transition to occur. 相似文献
2.
We consider a discrete-time stochastic model of an ECN/RED gateway where competing TCP sources share the link capacity. As
the number of competing flows becomes large, the asymptotic queue behavior (normalized by the number of flows) at the gateway
can be described by a simple recursion and the throughput behavior of individual TCP flows becomes asymptotically independent.
A Central Limit Theorem complement is also presented, yielding a more accurate characterization of the asymptotic queue size.
These results suggest a scalable yet accurate model of this complex large-scale stochastic feedback system, and crisply reveal
the sources of queue fluctuations.
This work was prepared through collaborative participation in the Communications and Networks Consortium sponsored by the
U.S. Army Research Laboratory under the Collaborative Technology Alliance Program, Cooperative Agreement DAAD19-01-2-0011.
This work was also supported by the Space and Naval Warfare Systems Center—San Diego under Contract No: N66001-00-C-8063.
The views and conclusions contained in this document are those of the authors and should not be interpreted as representing
the official policies, either expressed or implied, of the Army Research Laboratory or the U.S. Government. 相似文献
3.
4.
5.
Washing conditions of phosphate slurry from which Ni–P–O–Te catalyst had been obtained had practically no effect on the initial H
surf.
+
concentration but affected substantially the degree of acidification of the catalyst surface during the first stage of ethylbenzene oxidehydrogenation, and thereby the catalyst activity.
, Ni–P–O–Te, H . + , .相似文献
6.
Paulina Mech-Warda Artur Giedo Anna Kawiak Natalia Maciejewska Mateusz Olszewski Mariusz Makowski Agnieszka Chylewska 《Molecules (Basel, Switzerland)》2022,27(12)
Pyrazine and its derivatives are a large group of compounds that exhibit broad biological activity, the changes of which can be easily detected by a substituent effect or a change in the functional group. The present studies combined theoretical research with the density functional theory (DFT) approach (B3LYP/6-311+G**) and experimental (potentiometric and spectrophotometric) analysis for a thorough understanding of the structure of chlorohydrazinopyrazine, its physicochemical and cytotoxic properties, and the site and nature of interaction with DNA. The obtained results indicated that 2-chloro-3-hydrazinopyrazine (2Cl3HP) displayed the highest affinity to DNA. Cytotoxicity studies revealed that the compound did not exhibit toxicity toward human dermal keratinocytes, which supported the potential application of 2Cl3HP in clinical use. The study also attempted to establish the possible equilibria occurring in the aqueous solution and, using both theoretical and experimental methods, clearly showed the hydrophilic nature of the compound. The experimental and theoretical results of the study confirmed the quality of the compound, as well as the appropriateness of the selected set of methods for similar research. 相似文献
7.
Sophia J. Makowski Evelyn Calta Michael Hörmannsdorfer Prof. Dr. Wolfgang Schnick 《无机化学与普通化学杂志》2012,638(2):345-351
The stability against hydrolysis of triazine tricarboxylate (TTC) in the presence of divalent transition metal and alkaline earth ions was investigated by means of X‐ray diffraction and FTIR spectroscopy. Depending on the size of the cation either formation of the respective triazine tricarboxylate salts or hydrolysis of TTC yielding oxalate was observed. The hydrolysis of TTC induced by transition metal ions could be explained in analogy to the hydrolysis of triazine tris(2‐pyrimidyl) as a result of ring tension caused by the coordination of these ions. By the reaction of potassium triazine tricarboxylate with alkaline earth salts in aqueous solution the alkaline earth triazine tricarboxylates M3[C3N3(CO2)3]2 · 12H2O (M = Sr, Ba) were obtained and analyzed by single‐crystal X‐ray diffraction. The isotypic salts represent the first examples of alkaline earth triazine tricarboxylates and the first TTC salts comprising solely divalent cations. 相似文献
8.
Dorota Majda Wac?aw Makowski Maria Mańko 《Journal of Thermal Analysis and Calorimetry》2012,109(2):663-669
Thermoporosimetry, i.e., DSC measurements of melting point depression of water and heptane confined in mesopores, has been used for determination the pore size distribution of several mesoporous silicas synthesized with the use of micelle templates. Porosity of these materials was additionally characterized by low-temperature nitrogen adsorption and quasi-equilibrated thermodesorption of nonane. The pore size distributions obtained using the water thermoporosimetry were similar to those determined using the other methods, but the pore size values found for the narrow pore materials were underestimated by ca 1?nm. Too large pore sizes obtained for the wide pore silica from heptane thermoporosimetry were attributed to nonlinear dependence of the melting point depression on the reciprocal of the pore size. 相似文献
9.
Maciej Makowski Krzysztof Pawełczak Paweł Kafarski Jolanta M. Dzik Barbara Gołos Małgorzata Balinska 《Phosphorus, sulfur, and silicon and the related elements》2013,188(8):1639-1651
The synthesis of six analogues of the potent thymidylate synthase (TS) inhibitor N -[4-[ N -[(3,4-dihydro-2-methyl-4-oxo-6-quinazolinoyl)-methyl]- N -prop-2-ynylamino]benzoyl]- L -glutamic acid 2 is described in which the glutamic acid residue has been replaced by DL -aminophosphonic acids. New antifolates were tested as inhibitors of TS isolated from mouse L1210 leukemic cells as well as inhibitors of growth mouse leukemic L5178Y cells. In general these modifications result in compounds that are considerably less potent than 2 as TS inhibitors with K i 's 0.17-1.10 w M. Very poor solubility in water limited their proper assay of growth cells inhibition. 相似文献
10.
RITVA LINDBERG GORAN SUNDHOLM JOHAN SJö BLOM PETRI AHONEN ESKO I. KAUPPINEN 《Journal of Dispersion Science and Technology》2013,34(1-2):715-722
The zeta-potentials of silica, copper, platinum and gold particles have been measured as a function of pH. The isoelectric points were found to be at pH 3.0, 5.8, 3.0 and 3.5, respectively. In the pH range 3.0 to 5.8 copper and silica particles are oppositely charged and accordingly the coating of silica with copper particles could be demonstrated. In the case of gold and platinum the sign of the charge is such that direct adhesion to silica particles cannot be expected and this was also demonstrated in the case of platinum. 相似文献