全文获取类型
收费全文 | 322篇 |
免费 | 4篇 |
专业分类
化学 | 181篇 |
晶体学 | 11篇 |
力学 | 16篇 |
数学 | 37篇 |
物理学 | 81篇 |
出版年
2022年 | 3篇 |
2021年 | 6篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 5篇 |
2016年 | 10篇 |
2015年 | 3篇 |
2014年 | 7篇 |
2013年 | 38篇 |
2012年 | 14篇 |
2011年 | 17篇 |
2010年 | 11篇 |
2009年 | 16篇 |
2008年 | 18篇 |
2007年 | 13篇 |
2006年 | 20篇 |
2005年 | 10篇 |
2004年 | 12篇 |
2003年 | 5篇 |
2002年 | 12篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1999年 | 2篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 6篇 |
1995年 | 5篇 |
1994年 | 11篇 |
1993年 | 4篇 |
1992年 | 8篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1986年 | 5篇 |
1980年 | 2篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1972年 | 3篇 |
1971年 | 3篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1967年 | 2篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1963年 | 1篇 |
1939年 | 2篇 |
1936年 | 2篇 |
1925年 | 1篇 |
1900年 | 1篇 |
排序方式: 共有326条查询结果,搜索用时 15 毫秒
71.
72.
The performance of a network subject to either state dependent or state independent flow control is investigated. In the state dependent case, the flow control policy is a function of the total number of packets for which the controller has not yet received an acknowledgment. In this case it is shown that the optimal flow control is a sliding window mechanism. The effect of the delayed feedback on the network performance as well as the size of the window are studied. The state independent optimal rate is also derived. The performance of the state dependent and state independent flow control policies are compared. Conditions for employing one of the two types of flow control policies for superior end-to-end network performance are discussed. All the results obtained are demonstrated using simple examples. 相似文献
73.
M. V. Kirov 《Journal of Structural Chemistry》1994,34(4):557-561
Energy and entropy characteristics of the F-structures of polyhedral water clusters containing tetragonal, pentagonal, and hexagonal faces with the intermolecular potential ST2 are studied.Institute of Thermal Physics, Ural Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 34, No. 4, pp. 77–82, July–August, 1993.Translated by L. Smolina 相似文献
74.
Rodica
Olar Mihaela Badea Veronica Lazar Carmen Balotescu Elena Cristurean Dana Marinescu 《Journal of Thermal Analysis and Calorimetry》2007,88(2):323-327
N,N-Dimethylbiguanide derivatives (HDMBG)X, where X=CH3COO
(1), Cl (2)
and NO3 (3) respectively,
exhibit in vitro antimicrobial activity
on representative bacterial and fungal strains. The presence of N,N-dimethylbiguanidium
ion for all derivatives was evidenced by IR and 1H
NMR spectra. Thermal analysis gave information on their decomposition steps
and also on the accompanying thermodynamic effects. According to TG and DTG
curves processes as melting, oxidative degradation as well as oxidative condensation
of –C=N– units occur. The different nature of the anions results
different melting points. Paracyanide formation at various condensation degrees
was observed. 相似文献
75.
76.
The synthesis of various 2H-1,5-benzodioxepin and 2,5-dihydro-1,6-benzodioxocin derivatives is described. The key step involves the construction of seven- and eight-membered rings via ring-closing metathesis reaction. 相似文献
77.
78.
Markus Lazar 《Physics letters. A》2010,374(30):3092-3098
We investigate the nonuniform motion of a straight screw dislocation in infinite media in the framework of the translational gauge theory of dislocations. The equations of motion are derived for an arbitrarily moving screw dislocation. The fields of the elastic velocity, elastic distortion, dislocation density and dislocation current surrounding the arbitrarily moving screw dislocation are derived explicitly in the form of integral representations. We calculate the radiation fields and the fields depending on the dislocation velocities. 相似文献
79.
Mihaela Badea Rodica Olar Dana Marinescu Veronica Lazar Carmen Chifiriuc Gina Vasile 《Journal of Thermal Analysis and Calorimetry》2009,97(2):781-785
This paper reports the investigation on the thermal stability of new complexes with mixed ligands of the type [Cd(NN)(C3H3O2)2(H2O)m]·nH2O [(1) NN: 1,10-phenantroline, m = 1, n = 0; (2) NN: 2,2′-bipyridine, m = 0, n = 1.5 and (C3H3O2): acrylate anion]. The IR data indicate a bidentate coordination mode for both heterocyclic amine and acrylate. The in vitro
qualitative and quantitative antimicrobial activity assays showed that the complexes exhibited variable antimicrobial activity
against planktonic as well as biofilm embedded Gram-negative (Escherichia coli, Klebsiella sp., Proteus sp., Salmonella sp., Shigella sp., Acinetobacter boumani, Pseudomonas aeruginosa), Gram-positive (Bacillus subtilis, Staphylococcus aureus) and fungal (Candida albicans) strains, reference and isolated ones from the hospital environment. The thermal behaviour steps were investigated
in synthetic air flow. The thermal transformations are complex processes according to TG and DTA curves including dehydration,
amine as well as acrylate thermolysis. The final products of decomposition are the most stable metal oxides. 相似文献
80.
The biochemistry of the para-sulfonato-calix[n]arenes has shown rapid development during the past ten years, the highly diverse biomedical applications of these molecules now include anti-viral, anti-thrombotic activities, enzyme blocking and protein complexation. The future is even more promising as para-sulfonato-calix[n]arenes have, now, been shown to have potential in the diagnosis of prion-based diseases. Their innocuous nature, as far as is known at present, may open up their future use in medications. 相似文献