全文获取类型
收费全文 | 260篇 |
免费 | 10篇 |
国内免费 | 4篇 |
专业分类
化学 | 143篇 |
晶体学 | 3篇 |
力学 | 23篇 |
数学 | 48篇 |
物理学 | 57篇 |
出版年
2023年 | 3篇 |
2022年 | 4篇 |
2021年 | 1篇 |
2020年 | 7篇 |
2019年 | 7篇 |
2018年 | 5篇 |
2017年 | 3篇 |
2016年 | 11篇 |
2015年 | 10篇 |
2014年 | 11篇 |
2013年 | 19篇 |
2012年 | 24篇 |
2011年 | 17篇 |
2010年 | 22篇 |
2009年 | 22篇 |
2008年 | 18篇 |
2007年 | 13篇 |
2006年 | 16篇 |
2005年 | 8篇 |
2004年 | 10篇 |
2003年 | 3篇 |
2002年 | 4篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1994年 | 2篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有274条查询结果,搜索用时 15 毫秒
31.
32.
Russian Journal of Organic Chemistry - Chiral norephedrine-based β-amino alcohol bearing a substituted thiophene ring were applied as catalysts for the enantioselective aldol reaction of... 相似文献
33.
34.
In this paper we consider the equation y
+q(t)y
+ p(t)h(y)=0, where p, q are real valued continuous functions on [0, ) such that q(t) 0, p(t) 0 and h(y) is continuous in (–, ) such that h(y)y > 0 for y 0. We obtain sufficient conditions for solutions of the considered equation to be nonoscillatory. Furthermore, the asymptotic behaviour of these nonoscillatory solutions is studied. 相似文献
35.
Aydin Aytuna Vyacheslav Zakharyuta 《Proceedings of the American Mathematical Society》2008,136(5):1733-1742
The main theorem of this note is the following refinement of the well-known Lelong-Bremermann Lemma: converges to uniformly on each compact subset of .
Let be a continuous plurisubharmonic function on a Stein manifold of dimension Then there exists an integer , natural numbers , and analytic mappings such that the sequence of functions
In the case when is a domain in the complex plane, it is shown that one can take in the theorem above (Section 3); on the other hand, for -circular plurisubharmonic functions in the statement of this theorem is true with (Section 4). The last section contains some remarks and open questions.
36.
Haydar Kilic Omer Aydin Sinan Bayindir Nurullah Saracoglu 《Journal of heterocyclic chemistry》2016,53(6):2096-2101
Bismuth nitrate catalyzed condensation reactions of indoline with 1,2‐ and 1,3‐diketones were investigated and were reported to proceed via different reaction pathways with the involvement of one or two of the carbonyl groups. While the reaction of indoline with cyclohexane‐1,3‐dione ( 4 ) gave solely condensation product, the reaction between the acetylacetone ( 5 ) and indoline provided N‐acetyl indoline as single products on retro‐aldol process. In contrast to 1,3‐diketones, the reaction with benzil ( 17 ) was performed under difficult conditions and proceeded to give secondary products. 相似文献
37.
In this study, the excitation functions for the reactions 203Tl(p, n)203Pb, 205Tl(p, 3n)203Pb, 203Tl(p, 2n)202Pb, 205Tl(p, 4n)202Pb, 203Tl(p, 3n)201Pb, 205Tl(p, 5n)201Pb, 203Tl(p, 4n)200Pb and 205Tl(p, 6n)200Pb have been calculated using pre-equilibrium and equilibrium reaction mechanisms. Calculated results based on hybrid model,
geometry-dependent hybrid model and cascade-exciton model have been compared with the experimental data.
相似文献
38.
Ultrasound-assisted emulsification-microextraction (USAEME) procedure was developed for the determination of selected polychlorinated biphenyls (PCBs) in 10 mL of water samples by gas chromatography-mass-selective detection. After determination of the most suitable solvent and extraction time, several other parameters including solvent volume, centrifugation time and ionic strength of the sample were optimized using a 23 factorial experimental design. The optimized USAEME procedure used 200 μL of chloroform as extraction solvent, 10 min of extraction with no ionic strength adjustment at 25 °C and 5 min of centrifugation at 4000 rpm. The limits of detection ranged from 14 ng L−1 (for PCB153) to 30 ng L−1 (for PCB101). Recoveries of PCBs from fortified distilled water are over 80% for three different fortification levels between 0.1 and 5 μg L−1 and relative standard deviations of the recoveries are below 10%. The performance of the proposed method was compared with those involving traditional liquid-liquid extraction (LLE) and solid phase extraction (SPE) on the real water samples (i.e., tap and well water as well as domestic and industrial wastewaters, etc.) and comparable efficiencies were obtained. The proposed USAEME procedure has been demonstrated to be viable, simple, rapid and easy to use for residue analysis of PCBs in water samples. 相似文献
39.
Arif A. Suleymanov Askar A. Abbasov Aydin J. Ismaylov 《Chaos, solitons, and fractals》2009,41(5):2474-2483
The peculiarities of fractal characteristics’ calculations for time series are described in this article. An algorithm for calculation of fractal dimension is suggested. It has been proved that the suggested method possesses high accuracy and the rapidity of convergence on the limited number of measurements compared to the methods of covering.The criteria of early diagnosis for changes in the condition of hydrodynamic processes, which do not vary by fractal dimension, have been recommended.The presented method is applicable for practical engineering calculations with self-affine, chaotic data, usually with relatively limited number of measurements. It is quite a simple method for calculation of fractal dimension, algorithm can be easily realized and it should be useful for engineers.The applicability of the proposed algorithm for fractal dimension calculation and early diagnosis criteria of qualitative changes in the behaviour of various dynamic systems has been tested both on simulated as well as practical examples of oil and gas production. 相似文献
40.
研究二阶非线性脉冲微分方程边界值问题(BVPI).构造了BVPI的Green函数,并将非线性的BVPI转化为不动点问题,利用Banach不动点定理和Lipschitz条件,证明了该非线性BVPI解的唯一性,最后证明了BVPI解的存在性定理. 相似文献