全文获取类型
收费全文 | 574篇 |
免费 | 16篇 |
国内免费 | 4篇 |
专业分类
化学 | 434篇 |
晶体学 | 4篇 |
力学 | 4篇 |
数学 | 41篇 |
物理学 | 111篇 |
出版年
2023年 | 2篇 |
2022年 | 5篇 |
2021年 | 3篇 |
2019年 | 9篇 |
2018年 | 5篇 |
2016年 | 12篇 |
2015年 | 8篇 |
2014年 | 13篇 |
2013年 | 30篇 |
2012年 | 16篇 |
2011年 | 25篇 |
2010年 | 14篇 |
2009年 | 15篇 |
2008年 | 37篇 |
2007年 | 39篇 |
2006年 | 32篇 |
2005年 | 30篇 |
2004年 | 31篇 |
2003年 | 29篇 |
2002年 | 20篇 |
2001年 | 12篇 |
2000年 | 17篇 |
1999年 | 4篇 |
1998年 | 8篇 |
1997年 | 6篇 |
1996年 | 8篇 |
1995年 | 4篇 |
1994年 | 7篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1989年 | 9篇 |
1988年 | 7篇 |
1987年 | 9篇 |
1985年 | 13篇 |
1984年 | 9篇 |
1983年 | 2篇 |
1982年 | 7篇 |
1981年 | 20篇 |
1980年 | 7篇 |
1979年 | 11篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 6篇 |
1973年 | 6篇 |
1972年 | 2篇 |
1966年 | 1篇 |
1960年 | 1篇 |
排序方式: 共有594条查询结果,搜索用时 0 毫秒
541.
We report our recent work on a hadronic molecule state of the KKN system with I =1/2 and jR = 1/2+. We assume that the A(1405) resonance and the scalar mesons, f0(980), ao(980), are reproduced as quasi-bound states of KN and KK, respectively. Performing non-relativistic three-body calculations with a variational method for this system, we find a quasibound state of the KIlN system around 1910 MeV below the three-body breakup threshold. This state corresponds to a new baryon resonance of N* with JP : 1/2+. We find also that this resonance has the cluster structure of the two-body bound states keeping their properties as in the isolated two-particle systems. We also briefly discuss another hadronic molecular state composed by two K and one N, which corresponds to a resonance. 相似文献
542.
Nishino MN Fujimoto M Phan TD Mukai T Saito Y Kuznetsova MM Rastätter L 《Physical review letters》2008,101(6):065003
Earth's magnetosphere is an obstacle to the supersonic solar wind and the bow shock is formed in the front side of it. In ordinary hydrodynamics, the flow decelerated at the shock is diverted around the obstacle symmetrically about the Earth-Sun line, which is indeed observed in the magnetosheath most of the time. Here we show a case under a very low-density solar wind in which duskward flow was observed in the dawnside magnetosheath. A Rankine-Hugoniot test shows that the magnetic effect is crucial for this "wrong flow" to appear. A full three-dimensional magnetohydrodynamics (MHD) simulation of the situation confirming this interpretation and earlier simulations is also performed. It is illustrated that in addition to the "wrong flow" feature, various peculiar characteristics appear in the global picture of the MHD flow interaction with the obstacle. 相似文献
543.
Noriyuki Suzuki Taiga Takabe Yoshiko Yamauchi Shun Koyama Rina Koike Masahiro Rikukawa Wei-Ting Liao Wen-Sheng Peng Fu-Yu Tsai 《Tetrahedron》2019,75(10):1351-1358
Palladium-catalyzed Mizoroki-Heck reactions were carried out in water using thermoresponsive polymer micelles. The micelles were generated from thermoresponsive block copolymers consisting of a poly(N-isopropylacrylamide) (PNIPAAm) segment and a hydrophilic segment such as nonionic poly(ethylene glycol) (PEG) (2) and anionic poly(sodium p-styrenesulfonate) (PSSNa) (9). These copolymers exhibited lower critical solution temperature (LCST) behavior at ca. 40–50?°C and showed thermal stimuli-induced formation and dissociation of micelles. The copolymers formed micelles in aqueous solution at higher temperature, where catalytic reactions proceeded. At lower temperature, the micelles dissociated to form a clear solution, enabling efficient extraction of the products from aqueous reaction mixture. In the presence of these copolymers, palladium complexes catalyzed the coupling reactions between aryl iodides and alkene compounds inside the hydrophobic micelle cores in water under relatively milder conditions. Extraction of the products from the aqueous solution of 2 or 9 was found to be efficient enough in comparison with conventional surfactants. 相似文献
544.
o-Nitrobenzyl photochemistry as induced by UV-A irradiation was applied to a photoactivated drug releasing system based on a molecular beacon strategy. A stem-and-loop structured oligodeoxynucleotide (ODN) possessing a photoreactive o-nitrobenzyl chromophore at the 3'-end and 1-aminonaphthalene quencher at the 5'-end underwent conformational change into a conventional double strand structure by hybridization with a specified target DNA. The intrinsic stem-and-loop structure suppressed photoactivated release of benzoic acid as a phantom drug from the o-nitrobenzyl chromophore because of intramolecular quenching by the 1-aminonaphthalene unit in close proximity to the chromophore. Formation of the double strand structure in the presence of perfectly matched target DNA minimized occurrence of intramolecular quenching and thereby enhanced the photoactivated drug release. 相似文献
545.
Y Ohishi T Mukai M Nagahara M Yajima N Kajikawa 《Chemical & pharmaceutical bulletin》1992,40(4):907-911
5-Alkyl-3-carboxymethylrhodanines (2) were prepared from 5-alkylmethylidene-3-carboxymethylrhodanines (1). The exo double bond of 1 was successfully reduced with NaBH4. The 1,4-addition reaction path was confirmed on the basis of proton nuclear magnetic resonance spectrum of the product (4b) obtained from the reduction of 3 using NaBD4. Optical resolution of the tert-butyl compound (2i) was achieved upon epimerization-crystallization method using L-3-amino-epsilon-caprolactam. The alkyl compounds (2) and the optical active compounds ((+)-2i, (-)-2i) were evaluated for aldose reductase inhibitory potency. 相似文献
546.
B. Cederwall A. Johnson B. Fant S. Juutinen P. Ahonen S. Mitarai J. Mukai J. Nyberg 《Zeitschrift für Physik A Hadrons and Nuclei》1991,338(4):463-464
In a γ-spectroscopic study, excited states in the very neutron deficient nucleus121La have been established for the first time. Rotational bands built on the 9/2+[404] and l/2?[550] Nilsson orbitals are observed up to a maximum spin of tentatively 51/2?. The experimental results are compared with Total Routhian Surface calculations. 相似文献
547.
J. Mukai N. Hashimoto T. Saitoh M. Matsuda T. Hayakawa J. Lu T. Komatsubara K. Furuno 《Zeitschrift für Physik A Hadrons and Nuclei》1996,356(1):367-368
The excited states of78Rb have been investigated by means of in-beam andβ-γ spectroscopy. The production of78Rb and theβ radioactivity of78Sr have been made through the54Fe(28Si,3pn) and54Fe(28Si,2p2n) reactions, respectively. Four rotational bands have been observed in the high-spin band structure. The signature splitting is large in the two bands, while the other two bands have small splitting. A detailed low-lying level scheme of78Rb has been constructed for the first time via theβ decay of78Sr in order to search for a linking transition between the high-spin band head and low lying states. 相似文献
548.
We consider a new problem, the Kth best valued assignment problem. Given a bipartite graph G and a cost vector w on its edge set, this is the problem of finding a perfect matching Mk in G such that there exist perfect matchings M1,…,MK−1 satisfying w(M1) < < w(MK−1) < w(MK), and w(MK) < w(M) for all perfect matchings M with w(M) ≠ w(M1),…,w(MK). Here w(M) denotes the sum of costs of edges in M. In this paper, we propose two algorithms for solving this problem and verify the efficiency of our algorithms by our preliminary computational experiments. 相似文献
549.
A new algorithm for solving nonconvex, equality-constrained optimization problems with separable structures is proposed in the present paper. A new augmented Lagrangian function is derived, and an iterative method is presented. The new proposed Lagrangian function preserves separability when the original problem is separable, and the property of linear convergence of the new algorithm is also presented. Unlike earlier algorithms for nonconvex decomposition, the convergence ratio for this method can be made arbitrarily small. Furthermore, it is feasible to extend this method to algorithms suited for inequality-constrained optimization problems. An example is included to illustrate the method.This research was supported in part by the National Science Foundation under NSF Grant No. ECS-85-06249. 相似文献
550.
Z.?YuanEmail author W.L.?Huang K.?Mukai 《Applied Physics A: Materials Science & Processing》2004,78(4):617-622
Contact angles of molten silicon on various substrates have been determined using the sessile drop method and reactivity has been investigated by examining cross sections between silicon and substrates with an electron-probe microanalyzer (EPMA). The contact angles between molten silicon and oxide substrates, such as SiO2(s), Al2O3(s) and MgO(s), are in the range 85° to 88°. The reaction zone is composed of forsterite (2MgO·SiO2) and clinoenstatite (2MgO·2SiO2) on the MgO(s)-side of the interface between the Si and MgO. The contact angle between molten silicon and Si3N4 is about 90°. Molten silicon spreads over the SiC plate and the contact angle is estimated to be 8°. Large contact-angle values (around 145°) have been observed on BN substrates. At the interface between Si(l) and the BN substrate, a discontinuous Si3N4 layer is believed to form and might retard the dissolution of BN into molten silicon. The BN substrate is regarded as being the most suitable substrate for supporting a molten silicon drop during surface tension measurements, due to the large contact angle and low contamination. PACS 68.08.Bc; 06.30.Bp; 73.40.Ns; 61.72.Tt 相似文献