全文获取类型
收费全文 | 579篇 |
免费 | 20篇 |
国内免费 | 1篇 |
专业分类
化学 | 362篇 |
晶体学 | 65篇 |
力学 | 5篇 |
数学 | 65篇 |
物理学 | 103篇 |
出版年
2022年 | 8篇 |
2021年 | 11篇 |
2019年 | 11篇 |
2018年 | 10篇 |
2017年 | 10篇 |
2016年 | 14篇 |
2015年 | 12篇 |
2014年 | 13篇 |
2013年 | 42篇 |
2012年 | 21篇 |
2011年 | 19篇 |
2010年 | 16篇 |
2009年 | 12篇 |
2008年 | 24篇 |
2007年 | 16篇 |
2006年 | 21篇 |
2005年 | 16篇 |
2004年 | 22篇 |
2003年 | 7篇 |
2002年 | 7篇 |
2001年 | 6篇 |
2000年 | 5篇 |
1999年 | 9篇 |
1996年 | 6篇 |
1995年 | 8篇 |
1994年 | 10篇 |
1993年 | 17篇 |
1992年 | 11篇 |
1991年 | 7篇 |
1990年 | 13篇 |
1989年 | 8篇 |
1988年 | 10篇 |
1987年 | 11篇 |
1986年 | 8篇 |
1985年 | 8篇 |
1984年 | 9篇 |
1983年 | 10篇 |
1981年 | 12篇 |
1980年 | 9篇 |
1979年 | 13篇 |
1978年 | 4篇 |
1977年 | 7篇 |
1976年 | 5篇 |
1972年 | 4篇 |
1968年 | 4篇 |
1947年 | 5篇 |
1946年 | 6篇 |
1941年 | 7篇 |
1940年 | 6篇 |
1937年 | 7篇 |
排序方式: 共有600条查询结果,搜索用时 0 毫秒
91.
Supriya S. Khot Prashant V. Anbhule Uday V. Desai Prakash P. Wadgaonkar 《Comptes Rendus Chimie》2018,21(9):814-821
Tris-hydroxymethylaminomethane has been demonstrated to be an efficient organocatalyst in diversity-oriented synthesis of medicinally prevalent spirochromenes by one-pot, three-component reactions between isatins, malononitrile, and enolizable CH acids like dimedone, 4-hydroxycoumarin, 4-hydroxy-N-methylquinolin-2-one, or in situ generated 2-methylpyrazolon-2-one. Biodegradability and extremely low cost of the catalyst are the noteworthy features of this chromatography-free protocol. 相似文献
92.
93.
Desai TG 《The Journal of chemical physics》2007,127(15):154707
Molecular dynamics simulations of NaCl fluid are used to understand the behavior of ionic fluid to screen the field generated by charges on the ionic crystal surfaces in absence of any external electric field. The NaCl fluid in the strongly coupled regime (corresponding to the melt) in contact with the charged octopolar (111) NaCl surface shows that the spatial correlations decay in an oscillatory manner, with a screening length lambdaQ given by the envelope of the damped oscillations. By contrast to the Debye-Huckel theory, in the strongly coupled regime, lambdaQ increases with increasing coupling strength (also seen in bulk ionic simulations). The NaCl fluid confined between neutral (100) NaCl surfaces also shows weak oscillatory charge decay near the surface. Similar oscillatory exponential decay was seen when the NaCl fluid was confined between two analytically smooth neutral walls. The origin of these oscillations was due to the difference in ion sizes. NaCl fluid confined between neutral octopolar (110) and dipolar (110) surface show stronger density oscillations than (100) surface but comparatively very weak charge oscillations. This paper shows that the strength of the charges on the crystal surfaces is enough to induce a characteristic spatial distribution of charges in the contacting fluid and the extent of distribution depends on the type of surface. 相似文献
94.
O.L. Schönborn R.C. Desai 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,9(4):719-724
We show how the interface curvature autocorrelation function (ICAF) and associated structure factor (ICSF), of relevance in
non-equilibrium pattern-formation problems where sharp interfaces are present, provide new and interesting information on
domain structure, as yet not visible via the order-parameter structure factor (OPSF). This is done by discussing numerical simulations of model A (non-conserved relaxational
phase-ordering kinetics) in two-dimensional systems. The ICAF is Gaussian over short distances and exhibits dynamical scaling
and t
1/2
power-law growth. We use it to show what the typical length-scale in the model A dynamics corresponds to physically and how
it can be obtained uniquely, rather than simply within a multiplicative constant. Experimental methods to measure the ICAF
and/or ICSF are still needed at this point.
Received 22 April 1998 相似文献
95.
Hindered‐amine light stabilizers were surface anchored to polyethylene and polypropylene thin films by: i) direct photo‐grafting of 1,2,2,6,6‐pentamethyl piperidinyl‐4‐acrylate onto the surface and ii) by reacting of 1,2,2,6,6‐pentamethyl‐4‐piperidinol with succinic anhydride functionalized polyolefin surface. The samples were exposed to UV irradiation in air and the oxidative‐degradation of the polymers was studied with FT‐IR spectroscopy. The photo‐stability of surface anchored Hindered‐amine stabilizers (HAS) was compared with films stabilized with commercial HAS by melt blending. The results of the study evince superiority of surface anchored HAS over that of melt blended polyolefins. 相似文献
96.
InBi0.8Sb0.2 single crystals have been grown by zone melting method. The freezing interface temperature gradient of 3 °C/cm has been found to yield the best quality crystals obtainable at growth velocity 1.0 cm/hr. Traingular features have been obtained on the free surface of the as grown crystal. A new dislocation etchant based on nitric acid has been found to give reproducible etch-pitting on the cleavage surface. Standard tests for a dislocation etchant have been carried out and results are reported. 相似文献
97.
98.
S. Petrovi? B. Gakovi? D. Peru?ko T. Desai D. Batani M. ?ekada B. Radak M. Trtica 《Laser Physics》2009,19(8):1844-1849
Interaction of an Nd:YAG laser, operating at 532 nm wavelength and pulse duration of 40 ps, with tungsten-titanium (WTi) thin film (thickness, 190 nm) deposited on single silicon (100) substrate was studied. Laser fluences of 10.5 and 13.4 J/cm2 were found to be sufficient for modification of the WTi/silicon target system. The energy absorbed from the Nd:YAG laser beam is partially converted to thermal energy, which generates a series of effects, such as melting, vaporization of the molten material, shock waves, etc. The following WTi/silicon surface morphological changes were observed: (i) ablation of the thin film during the first laser pulse. The boundary of damage area was relatively sharp after action of one pulse whereas it was quite diffuse after irradiation with more than 10 pulses; (ii) appearance of some nano-structures (e.g., nano-ripples) in the irradiated region; (iii) appearance of the micro-cracking. The process of the laser interaction with WTi/silicon target was accompanied by formation of plasma. 相似文献
99.
Hanif D. Sherali Evrim Dalkiran Jitamitra Desai 《Computational Optimization and Applications》2012,52(2):483-506
In this paper, we propose to enhance Reformulation-Linearization Technique (RLT)-based linear programming (LP) relaxations for polynomial programming problems by developing cutting plane strategies using concepts derived from semidefinite programming. Given an RLT relaxation, we impose positive semidefiniteness on suitable dyadic variable-product matrices, and correspondingly derive implied semidefinite cuts. In the case of polynomial programs, there are several possible variants for selecting such particular variable-product matrices on which positive semidefiniteness restrictions can be imposed in order to derive implied valid inequalities. This leads to a new class of cutting planes that we call v-semidefinite cuts. We explore various strategies for generating such cuts, and exhibit their relative effectiveness towards tightening the RLT relaxations and solving the underlying polynomial programming problems in conjunction with an RLT-based branch-and-cut scheme, using a test-bed of problems from the literature as well as randomly generated instances. Our results demonstrate that these cutting planes achieve a significant tightening of the lower bound in contrast with using RLT as a stand-alone approach, thereby enabling a more robust algorithm with an appreciable reduction in the overall computational effort, even in comparison with the commercial software BARON and the polynomial programming problem solver GloptiPoly. 相似文献
100.