全文获取类型
收费全文 | 636篇 |
免费 | 20篇 |
国内免费 | 6篇 |
专业分类
化学 | 376篇 |
晶体学 | 11篇 |
力学 | 19篇 |
综合类 | 1篇 |
数学 | 83篇 |
物理学 | 172篇 |
出版年
2023年 | 10篇 |
2022年 | 29篇 |
2021年 | 18篇 |
2020年 | 13篇 |
2019年 | 13篇 |
2018年 | 16篇 |
2017年 | 21篇 |
2016年 | 26篇 |
2015年 | 22篇 |
2014年 | 17篇 |
2013年 | 59篇 |
2012年 | 31篇 |
2011年 | 35篇 |
2010年 | 27篇 |
2009年 | 20篇 |
2008年 | 28篇 |
2007年 | 28篇 |
2006年 | 25篇 |
2005年 | 20篇 |
2004年 | 14篇 |
2003年 | 9篇 |
2002年 | 10篇 |
2000年 | 6篇 |
1999年 | 4篇 |
1998年 | 7篇 |
1997年 | 10篇 |
1996年 | 7篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1993年 | 6篇 |
1990年 | 4篇 |
1989年 | 9篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 7篇 |
1984年 | 8篇 |
1983年 | 3篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 11篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1977年 | 8篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 5篇 |
1971年 | 3篇 |
1959年 | 5篇 |
排序方式: 共有662条查询结果,搜索用时 15 毫秒
1.
Aequationes mathematicae - In this paper, we establish a new class of dynamic inequalities of Hardy’s type which generalize and improve some recent results given in the literature. More... 相似文献
2.
H.S RagabA Shehap M.S Abo EllilW.H Osman F.H Abd El-Kader 《Journal of Physics and Chemistry of Solids》2002,63(10):1839-1847
Ternary-phase ceramic system of Li2O Al2O3 4SiO2 doped with CuO, FeO and TiO2 has been prepared and subjected to dc electrical conductivity and thermally stimulated depolarization current (TSDC) measurements as a function of temperature (30-250 °C) and field strength. The electrical conductivity results are explained by assuming both ionic and electronic conduction mechanisms coexist with different contributions over the whole temperature range of experiments. TSDC spectra have been found to be characterized by a broad intense relaxation peak, which can be attributed to an ionic charge polarization. The broad relaxation transitions are apparently a result of the nonuniform nature of this process. Activation energies are calculated for both dc electrical conductivity and TSDC according to Arrhenius equation and initial rise method, respectively. 相似文献
3.
Iradj Ouveysi Andrew Wirth Annie Yeh Osman Oğuz 《Annals of Operations Research》2003,124(1-4):285-293
We consider the problem of providing a minimum cost multi-service network subject to one link failure scenarios. We assume our network is fully meshed and demand is satisfied by using direct or two hop-paths. We provide a large scale linear programming formulation and propose and test two effective heuristics. 相似文献
4.
Mat Rasol Awang Hassan Hamdani Mutaat Mohd. Shukri Mahmud Wan Badrin Wan Husain Tajuddin Osman Khomsaton Abu Bakar Asmahwati Kassim Zal U''yun Wan Mahmud Ishak ManafTamikazu Kume Shoji Hashimoto 《Radiation Physics and Chemistry》1993,42(4-6):611-616
In solid state fermentation, Pleurotus sajor-caju has been found to be able to degrade at least 30% oil palm empty Fruit Bunch (EFB) fibre leaving 70 % useful materials. Conditions under which fermentation carried out were investigated. It was found that, in the temperature range between 25– 28 °C, relative ph between 6–8, moisture between 60–70 % and medium composition of CaCO3: rice bran 2 %: 5 % were the optimum conditions. The results showed in fermented products that, there were substantial reduction in cellulosic component such as Crude Fiber (CF, 18 %); Acid Detergent Fibre (ADF, 45 %), Neutral Detergent Fibre (NDF, 61 %) and Acid Detergent Lignin (ADL, 14 %). However, Crude Protein (CP, 10%) increased resulted from single cell protein enrichment of mycelial microbial mass. The mass reductions of substrate in fermentation process corresponds to the CO2 released during fermentation. Hence, attributable to the decreased in content of CF, ADF, NDF, and ADL. The digestibility study has also been carried out to determine the useful level of this product to ruminant. Aflatoxin content was detected low in both the initial substrates and products. Based on nutritional value and low content of aflatoxin, the product is useful as a source of roughage to ruminant. 相似文献
5.
We prove that the set of homotopy classes of the paths in a topological ring is a ring object (called ring groupoid). Using this concept we show that the ring structure of a topological ring lifts to a simply connected covering space. 相似文献
6.
7.
Proteins obtained from agricultural sources represent a unique feedstock from which to prepare thermally processable polymers. In this study, thermally processed feather keratin films were composted with three-month-old compost inoculum in self-heating laboratory composters for 30 days and temperature and carbon dioxide development monitored. About 24% of the available carbon in the feather keratin polymer (FKP) was metabolized in this time and this may not be high enough for some applications. Degradation of the feather keratin polymers was observed within 10 days with concurrent molecular weight reduction measured using FT-IR. Visual inspection of the polymers also showed destruction of the films. A change in crystallinity was observed in DSC analysis and some degradation processes could be inferred from this as well. 相似文献
8.
9.
M. M. Hafiz N. Afify M. A. Osman M. Dongol 《Journal of Thermal Analysis and Calorimetry》1990,36(7-8):2417-2426
The crystallization kinetics of the chalcogenide glass Se0.8Te0.2 was studied by means of differential scanning calorimetry. The variation in partial area (X) with temperature (T) revealed that the transition from the amorphous to the crystalline phase occurs in two dimensions.Activation energies were determined for both the glass transition (E
t) and the crystallization (E
c).E
t was calculated from the variation inT
g with the heating rate (a).E
c was determined by three different methods: (i) variation inX withT, (ii) variation inT
p
witha, and (iii) variation inT
c witha.E
t andE
c have values of 161.01±2.75 and 84.75 ±8.21 kJ/mol, respectively.
This work was partly supported by a Grant-in-Aid for Scientific Research from the GTZ GmbH and DAAD, W. Germany. 相似文献
Zusammenfassung Mittels DSC wurde die Kristallisierungskinetik des Chalkogenidglases Se0.8Te0.2 untersucht. Eine Änderung partieller Gebiete (X) mit der Temperatur (T) zeigte, daß der Übergang von der amorphen zur kristallinen Phase zweidimensional verläuft.Es wurde die Aktivierungsenergie sowohl für den Glasübergang (E t) als auch für die Kristallisierung (E c) bestimmt.E t wurde mittels der Abhängigkeit vonT g von der Aufheizgeschwindigkeit (a) ermittelt.E c wurde auf drei verschiedene Wege bestimmt: (i) Änderung vonX in Abhängigkeit vonT, (ii) Änderung vonT p in Abhängigkeit vona und (iii) Änderung vonT c in Abhängigkeit vona. Die Werte vonE t undE c betragen 161.01±2.75 bzw. 84.75±8.21 kJ/mol.
This work was partly supported by a Grant-in-Aid for Scientific Research from the GTZ GmbH and DAAD, W. Germany. 相似文献
10.