全文获取类型
收费全文 | 323778篇 |
免费 | 3512篇 |
国内免费 | 942篇 |
专业分类
化学 | 177676篇 |
晶体学 | 4969篇 |
力学 | 13776篇 |
综合类 | 11篇 |
数学 | 32626篇 |
物理学 | 99174篇 |
出版年
2018年 | 2600篇 |
2016年 | 4440篇 |
2015年 | 3046篇 |
2014年 | 4524篇 |
2013年 | 13316篇 |
2012年 | 9450篇 |
2011年 | 11903篇 |
2010年 | 8073篇 |
2009年 | 8056篇 |
2008年 | 10881篇 |
2007年 | 11083篇 |
2006年 | 10515篇 |
2005年 | 9607篇 |
2004年 | 8740篇 |
2003年 | 7766篇 |
2002年 | 7684篇 |
2001年 | 9351篇 |
2000年 | 7168篇 |
1999年 | 5650篇 |
1998年 | 4625篇 |
1997年 | 4622篇 |
1996年 | 4418篇 |
1995年 | 4112篇 |
1994年 | 4014篇 |
1993年 | 3768篇 |
1992年 | 4457篇 |
1991年 | 4410篇 |
1990年 | 4235篇 |
1989年 | 4249篇 |
1988年 | 4133篇 |
1987年 | 4068篇 |
1986年 | 3806篇 |
1985年 | 5150篇 |
1984年 | 5258篇 |
1983年 | 4333篇 |
1982年 | 4673篇 |
1981年 | 4491篇 |
1980年 | 4363篇 |
1979年 | 4621篇 |
1978年 | 4988篇 |
1977年 | 4738篇 |
1976年 | 4710篇 |
1975年 | 4493篇 |
1974年 | 4506篇 |
1973年 | 4522篇 |
1972年 | 2971篇 |
1971年 | 2564篇 |
1968年 | 2883篇 |
1967年 | 3097篇 |
1966年 | 2627篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
E. S. Moskalenko M. Larsson K. F. Karlsson P. O. Holtz B. Monemar W. V. Schoenfeld P. M. Petroff 《Physics of the Solid State》2007,49(10):1995-1998
We report on low-temperature microphotoluminescence (μ-PL) measurements of InAs/GaAs quantum dots (QDs) exposed to a lateral
external electric field. It is demonstrated that the QDs’ PL signal could be increased severalfold by altering the external
and/or the internal electric field, which could be changed by an additional infrared laser. A model which accounts for a substantially
faster lateral transport of the photoexcited carriers achieved in an external electric field is employed to explain the observed
effects. The results obtained suggest that the lateral electric fields play a major role for the dot luminescence intensity
measured in our experiment—a finding which could be used to tailor the properties of QD-based optoelectronic applications.
The text was submitted by the authors in English. 相似文献
993.
The notion of a fuzzy retract was introduced by Rodabaugh (1981). The notion of a fuzzy pairwise retract was introduced in 2001. Some weak forms and some strong forms of α-continuous mappings were introduced in 1988 and 1997. The authors extend some of these forms to the L-fuzzy bitopological setting and construct various α-fuzzy pairwise retracts. The concept of weakly induced spaces in the case L = [0,1] was introduced by Martin (1980). Liu and Luo (1987) generalized this notion to the case that L is an arbitrary F-lattice and introduced the notion of induced L-fts. Several results are obtained, especially, for L-valued pairwise stratification spaces. 相似文献
994.
The electronic states of the Cr overlayers on TiO2(0 0 1) surfaces have been investigated using angle-resolved and resonant photoemission spectroscopy with synchrotron radiation. At lower coverages, Cr deposition on TiO2(0 0 1) creates two well separated in-gap emissions due to the formation of surface Ti3+ (3d1) ions and Cr3+ (3d3) ions. At higher coverages, the in-gap emission is developed into the 2-peak-structure emission of Cr 3d character. The corresponding state is considered to be of metallic nature from the viewpoint of the high ability of oxygen adsorption, but has no Fermi edge, indicating a possibility of forming small Cr clusters on TiO2(0 0 1) at this stage. 相似文献
995.
Kentsch U. Zschornack G. Grossmann F. Ovsyannikov V. P. Ullmann F. 《Hyperfine Interactions》2003,148(1-4):237-242
Hyperfine Interactions - It is well known that many reinforced concrete structures are at risk of deterioration due to chloride ion contamination of the concrete or atmospheric carbon dioxide... 相似文献
996.
997.
The chemical composition of 200 renal stones, collected from Taxila, Rawalpindi and Islamabad regions in Pakistan, was determined by thermogravimetric (TG) and differential thermal analysis (DTA) techniques. The thermal curves show weight losses at various temperatures indicating dehydration and decomposition phenomena of renal stones. Results were compared with qualitative data obtained by IR analysis which confirmed the chemical composition of various stones in the solid state. The thermal curves helped in the differentiation of various kinds of water held by stones and their chemical composition was obtained by weight loss during pyrolysis. It was found that 26.5% of the stones were pure whewellite, 3% weddellite, 13% uric acid anhydrous, 7.5% struvite, 2.5% ammonium acid urate, 0.5% cystine and 47% stones had mixed composition. In the mixed state the most frequent combinations were those of calcium oxalate with uric acid (14.5%) and with phosphates (27.5%).
Zusammenfassung Mittels TG und DTA wurde die chemische Zusammensetzung von 200 Nierensteinen untersucht, die in den Gebieten Taxila, Rawalpindi und Islamabad in Indien gesammelt wurden. Die Thermogramme zeigen Masseverluste bei verschiedenen Temperaturen, die auf Dehydratation und Zersetzung der Nierensteine hinweisen. Die Ergebnisse wurden mit den qualitativen Resultaten aus der IR-Analyse verglichen, welche die chemische Zusammensetzung der verschiedenen Steine im festen Zustand bekräftigte. Die Thermogramme halfen bei der Unterscheidung von verschieden gebundenem Wasser, ihre chemische Zusammensetzung wurde durch Gewichtsverlust bei der Pyrolyse bestimmt. Man fand, daß 26.5 % der Steine aus reinem Whewellit bestanden, 3 % aus Weddellit, 13 % aus anhydrierter Harnsäure, 7.5 % aus Struvit, 2.5 % aus Ammmoniumhydrogenurat, 0.5 % aus Cystin und 47 % der Steine hatten eine gemischte Zusammensetzung. Die häufigsten Kombinationen der Mischzusammensetzungen waren Calciumoxalat mit Harnsäure (14.5 %) und mit Phosphaten (27.5 %).相似文献
998.
999.
N. E. Tovmasyan H. A. Babayan 《Journal of Contemporary Mathematical Analysis (Armenian Academy of Sciences)》2007,42(4):198-204
The paper establishes some solvability conditions of the Cauchy problem for linear differential equation in the class of monotone increasing functions. The results are applied for clarifying the possibility of flight along a given trajectory under existence of braking forces. 相似文献
1000.