全文获取类型
收费全文 | 120篇 |
免费 | 1篇 |
专业分类
化学 | 84篇 |
晶体学 | 9篇 |
数学 | 16篇 |
物理学 | 12篇 |
出版年
2021年 | 1篇 |
2020年 | 3篇 |
2019年 | 1篇 |
2018年 | 7篇 |
2017年 | 9篇 |
2016年 | 5篇 |
2015年 | 2篇 |
2014年 | 5篇 |
2013年 | 5篇 |
2012年 | 10篇 |
2011年 | 11篇 |
2010年 | 12篇 |
2009年 | 8篇 |
2008年 | 5篇 |
2007年 | 10篇 |
2006年 | 3篇 |
2005年 | 3篇 |
2004年 | 2篇 |
2003年 | 3篇 |
2002年 | 2篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
排序方式: 共有121条查询结果,搜索用时 15 毫秒
81.
Evald Übi 《Central European Journal of Mathematics》2005,3(2):228-241
A linear programming problem is transformed to the finding an element of polyhedron with the minimal norm. According to A.
Cline [6], the problem is equivalent to the least squares problem on positive ortant. An orthogonal method for solving the
problem is used. This method was presented earlier by the author and it is based on the highly developed least squares technique.
First of all, the method is meant for solving unstable and degenerate problems. A new version of the artifical basis method
(M-method) is presented. Also, the solving of linear inequality systems is considered. 相似文献
82.
P. Ünak F. Yurt Lambrecht F. Z. Biber S. Darcan 《Journal of Radioanalytical and Nuclear Chemistry》2007,273(3):649-651
This study was designed to evaluate iodine concentrations in drinking water samples using isotope dilution analysis (IDA)
in the Aegean region of Turkey A total of 76 drinking water samples from rural and urban areas in regional cities were analyzed.
The mean iodine concentration was 78±27 μg/l and iodine concentration ranges were within 69±26 μg/l and 103±6 μg/l. 相似文献
83.
We introduce the concept of a base conformal warped product of two pseudo-Riemannian manifolds. We also define a subclass
of this structure called as a special base conformal warped product. After, we explicitly mention many of the relevant fields
where metrics of these forms and also considerations about their curvature related properties play important rolls. Among
others, we cite general relativity, extra-dimension, string and super-gravity theories as physical subjects and also the study
of the spectrum of Laplace-Beltrami operators on p-forms in global analysis. Then, we give expressions for the Ricci tensor and scalar curvature of a base conformal warped
product in terms of Ricci tensors and scalar curvatures of its base and fiber, respectively. Furthermore, we introduce specific
identities verified by particular families of, either scalar or tensorial, nonlinear differential operators on pseudo-Riemannian
manifolds. The latter allow us to obtain new interesting expressions for the Ricci tensor and scalar curvature of a special
base conformal warped product and it turns out that not only the expressions but also the analytical approach used are interesting
from the physical, geometrical and analytical point of view. Finally, we analyze, investigate and characterize possible solutions
for the conformal and warping factors of a special base conformal warped product, which guarantee that the corresponding product
is Einstein. Besides all, we apply these results to a generalization of the Schwarzschild metric.
相似文献
84.
Dirk Haller Perihan Ekici Albrecht Friess Harun Parlar 《Applied biochemistry and biotechnology》2010,162(6):1547-1557
Tweezing adsorptive bubble separation (TABS) was used as a method for the enrichment of matrix metalloproteinases (92-kDa type IV, gelatinase B (MMP-9)) and carboxypeptidase A (CPA) from dilute aqueous solutions. The method is based on the chelation of metalloenzymes applying 2-(carbamoylmethyl-(carboxymethyl)amino)acetic acid (ADA) coupled with an octyl part to form a surface active unit. MMP-9 could be enriched with an enrichment ratio of 12.0 and a recovery of 87.3%, and CPA could be enriched 18.8-fold and with 95.3% recovery. Both enzymes were enriched without significant losses of enzymatic activity. To verify that the enzymes were tweezed by ADA-C8 without abstraction of the zinc ions from the active center, TABS trials were additionally conducted with zinc ions in complex with ADA-C8, which revealed only negligible enrichment ratios of the enzymes (2.2 for MMP-9 and 0.2 for CPA). The results obtained impressively demonstrate that zinc-containing proteases can be enriched selectively and efficiently by TABS. 相似文献
85.
T. Ünak 《Journal of Radioanalytical and Nuclear Chemistry》2009,280(2):223-226
It is well known that several reports on the common educational problems of nuclear chemistry have been prepared by certain
groups of experts from time to time. According to very important statements in these reports, nuclear chemistry and related
courses generally do not take sufficient importance in undergraduate chemistry curricula and it was generally proposed that
nuclear chemistry and related courses should be introduced into undergraduate chemistry curricula at universities worldwide.
Starting from these statements, an ideal program in an undergraduate chemistry curriculum was proposed to be introduced into
the undergraduate chemistry program at the Department of Chemistry, Ege University, in Izmir, Turkey during the regular updating
of the chemistry curriculum. Thus, it has been believed that this Department of Chemistry has recently gained an ideal teaching
program in the field of nuclear chemistry and its applications in scientific, industrial, and medical sectors. In this contribution,
the details of this program will be discussed. 相似文献
86.
H. Enginar P. ünak F. Y. Lambrecht F. Z. Biber Müftüler E. I. Medine S. Yolcular A. Yurt B. Seyito?lu I. Bulduk 《Journal of Radioanalytical and Nuclear Chemistry》2009,280(2):363-370
Codeine which was extracted from dry capsules of the opium poppy (Papaver somniferum) was purified by HPLC (High Performance Liquid Chromatography) and characterized by NMR (Nuclear Magnetic Resonance) and
IR (Infrared) spectroscopy techniques. The purified compound was labeled with 131I and biodistribution studies were performed in rats. Radioiodinated codeine distributed uniformly in the cerebellum, m.pons,
striatum and hypothalamus while the other branch of brain and Stomach, urinary bladder, and small intestine uptakes were significantly
higher than other tissues. 相似文献
87.
We define the Balanced Disjoint Rings (BDR) problem as developing a method to partition of the nodes in a network to form
a given number of disjoint rings of minimum total link length in such a way that there is almost the same number of nodes
in each ring. The BDR problem has potential applications in the design of survivable network structures in telecommunications
as well as in the identification of local distribution/collection routes in logistics. The BDR problem can also be considered
a generalization of the traveling salesman problem since we are interested in multiple tours instead of a single tour. We
develop an efficient heuristic solution methodology that involves various GRASP-based randomized solution construction routines
that allow a multi-start framework and a n effective combination of cyclic-exchange and single-move neighborhoods in a local
search improvement procedure. The algorithms perform very well in our numerical studies, providing encouraging optimality
and lower bound gaps with very reasonable runtimes. 相似文献
88.
Fatma Aydın Hüseyin Ünver Doğan Aykaç Nazan Ocak İskeleli 《Journal of chemical crystallography》2010,40(12):1082-1086
Abstract
4-(3-Benzoylthioureido)benzoic acid has been synthesized from the reaction of 4-aminobenzoic acid with benzoyl isothiocyanate. The title compound has been characterized by elemental analysis, MS, FT-IR, 1H-NMR, 13C-NMR and UV–Visible techniques. The structure of the compound has also been examined crystallographically. The title compound crystallizes in the triclinic space group P-1 with a = 3.969(1), b = 13.039(1), c = 13.504(1) ?, α = 96.50(1)°, β = 92.25(1)°, γ = 94.94(1), V = 691.0(1) ?3 and D x = 1.444 g cm−3, respectively. The crystal structure has been solved by direct methods and refined by full-matrix least squares and found R 1 = 0.031 and wR 2 = 0.081 for 2909 observed reflections [I > 2σ(I)]. 相似文献89.
For the first time, the solanidine alkaloids alpha-solanine and alpha-chaconine could be quantitatively enriched from potato juice by Adsorptive Bubble Separation (ABS) with a pH gradient. The enrichment into the foam was influenced by the pH value, bubble size, and gas flow rate. The efficiency was highest on using diluted samples with a concentration between 2 and 6 mg L(-1) of the alkaloids at pH 6.0. The experiments with a standard solution of each alkaloid confirmed that these substances can be quantitatively enriched into the 'spumat' without surface active potato proteins. The transfer into the foam fraction under these conditions was similar to that from the aqueous potato extract. 相似文献
90.
In this study, the stability constants of uranium(VI) and thorium(IV) complexes formed with 8-hydroxyquinoline (8-HOQ) and its 5-sulfonic acid (8-HOQ-5-SO3H) derivative have been determined using the Irving-Rossotti method, computing the Calvin-Bjerrum pH-titration data. As a result, it is determined that the thorium(IV) complexes are considerably more stable than the corresponding uranium(VI) complexes. On the other hand, the complexes formed between 8-HOQ-5-SO3H and uranium(VI) or thorium(IV) are less stable than the corresponding 8-HOQ complexes. 相似文献