全文获取类型
收费全文 | 700篇 |
免费 | 20篇 |
国内免费 | 1篇 |
专业分类
化学 | 467篇 |
晶体学 | 5篇 |
力学 | 11篇 |
数学 | 31篇 |
物理学 | 207篇 |
出版年
2024年 | 7篇 |
2023年 | 7篇 |
2022年 | 21篇 |
2021年 | 15篇 |
2020年 | 16篇 |
2019年 | 22篇 |
2018年 | 16篇 |
2017年 | 23篇 |
2016年 | 28篇 |
2015年 | 12篇 |
2014年 | 17篇 |
2013年 | 57篇 |
2012年 | 27篇 |
2011年 | 31篇 |
2010年 | 26篇 |
2009年 | 27篇 |
2008年 | 26篇 |
2007年 | 29篇 |
2006年 | 34篇 |
2005年 | 27篇 |
2004年 | 20篇 |
2003年 | 12篇 |
2002年 | 16篇 |
2001年 | 11篇 |
2000年 | 7篇 |
1999年 | 12篇 |
1998年 | 5篇 |
1997年 | 5篇 |
1996年 | 6篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1991年 | 5篇 |
1989年 | 10篇 |
1988年 | 4篇 |
1987年 | 8篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 15篇 |
1981年 | 13篇 |
1980年 | 9篇 |
1979年 | 10篇 |
1978年 | 10篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1975年 | 4篇 |
1973年 | 9篇 |
1963年 | 3篇 |
排序方式: 共有721条查询结果,搜索用时 31 毫秒
81.
A modular approach to 5-acylated naphtho[2,1-b]benzofurans was developed where Sonogashira cross-coupling and intramolecular alkyne carbonyl metathesis were sequentially employed to build the aromatic benzene C ring of naphtho[2,1-b]benzofuran with an acyl group at the C5 position. 相似文献
82.
S. N. V. M. S. Gupta A. K. Nayak U. B. Misra Balaji Rao Yarasi C. Phani Babu G. Kalyanakrishnan 《Journal of Radioanalytical and Nuclear Chemistry》2017,313(3):571-579
The present paper describes a new analytical method developed for direct determination of boron in steels using radio frequency glow discharge optical emission spectrometer. “Single parameter alternative method” technique has been used to optimize the various experimental conditions of glow discharge plasma such as forward power, gas pressure inside plasma chamber, pre-integration time, and integration time. Different emission lines for boron were studied and inter element interference effect is also discussed in the paper. A complete statistical analysis has been done to validate the developed method. A RSD of less than ±5% is achieved for boron in the range of 0.0010–0.020% in Steels using this method. 相似文献
83.
Yughandhar Sreedhar Neelam Rekha Dasari P. Reddy Prasad M. Sankar Nayak 《Journal of Saudi Chemical Society》2010,14(2):149-155
A novel analytical reagent 4-(2-hydroxy phenyl ethaminodiol), benzene-1,3-diol(4-2-HPEDB-1,3,D) was synthesized for the determination of molybdenum(VI). The present paper reveals the detailed study of electroanalytical behaviour for [Mo-(4-2-HPEDB-1,3,D)] complex under optimized conditions. The peak obtained for [Mo-(4-2-HPEDB-1,3,D)] prevent the interference of foreign ions which shows the sensitivity of the proposed method. The linearity was maintained at the concentration range of 0.5–200 μg/mL at pH 4.5 with correlation factor 0.9997. The present method was successfully applied for the analysis of molybdenum(VI) in biological fluids and plant material. The results obtained from the proposed method show good agreement with reference method. 相似文献
84.
Mukesh G. Nayak L.K. Saini 《Physica E: Low-dimensional Systems and Nanostructures》2011,44(1):196-201
We study the effect of finite width on the ground-state of a spin-polarized electron–electron quantum bilayers (EEBL) system at temperature T=0. Correlations among carriers are treated beyond the static mean-field theories by using the quantum or dynamical version of Singwi, Tosi, Land and Sjölander (qSTLS) theory. Numerical results are presented for the pair-correlation function, the ground-state energy, the static density susceptibility, and the static local-field correction factor as a function of density parameter rsl and interlayer spacing d. Interestingly, we find that the inclusion of finite width lowered the critical density, for the onset of Wigner crystal (WC) ground-state, as compared to the similar recent study of spin-polarized EEBL system without finite width effect. Further, spin-polarization effect is seen to introduce a marked change in the ground-state energy of the EEBL system as compared to the results of unpolarized EEBL system with finite width. Results of ground-state energies are also compared with the recent diffusion Monte Carlo (DMC) and variational Monte Carlo (VMC) simulation studies of spin-polarized EEBL system with zero width. 相似文献
85.
86.
Flow through a channel whose walls are lined with non-erodible porous material is investigated using Beavers and Joseph slip
boundary condition. It is shown that the effect of porous lining is to increase the mass flow rate and to decrease the friction
factor. 相似文献
87.
Vikas Jain A.K. Nayak P.K. Vijayan D. Saha R.K. Sinha 《Experimental Thermal and Fluid Science》2010,34(6):776-787
Natural circulation as a mode of heat removal is being considered as a prominent passive feature in the innovative nuclear reactor designs, particularly in boiling-water-reactors, due to its simplicity and economy. However, boiling natural circulation system poses many challenges to designer due to occurrence of various kinds of instabilities such as excursive instability, density wave oscillations, flow pattern transition instability, geysering and metastable states in parallel channels. This problem assumes greater significance particularly at low-pressures i.e. during startup, where there is great difference in the properties of two phases. In light of this, a parallel channel loop has been designed and installed that has a geometrical resemblance to the pressure-tube-type boiling-water-reactor, to investigate into the behavior of boiling natural circulation. The loop comprises of four identical parallel channels connected between two common plenums i.e. steam drum and header. The recirculation path is provided by a single downcomer connected between steam drum and header. Experiments have been conducted over a wide range of power and pressures (1–10 bar). Two distinct unstable zones are observed with respect to power i.e. corresponding to low power (Type-I) and high power (Type-II) with a stable zone at intermediate powers. The nature of oscillations in terms of their amplitude and frequency and their evolution for Type-I and Type-II instabilities are studied with respect to the effect of heater power and pressure. This paper discusses the evolution of unstable and stable behavior along with the nature of flow oscillation in the channels and the effect of pressure on it. 相似文献
88.
Finite clusters of atoms or molecules, typically composed of about 50 particles (and often as few as 13 or even less) have
proved to be useful prototypes of systems undergoing phase transitions. Analogues of the solid-liquid melting transition,
surface melting, structural phase transitions and the glass transition have been observed in cluster systems. The methods
of nonlinear dynamics can be applied to systems of this size, and these have helped elucidate the nature of the microscopic
dynamics, which, as a function of internal energy (or ‘temperature’) can be in a solidlike, liquidlike, or even gaseous state.
The Lyapunov exponents show a characteristic behaviour as a function of energy, and provide a reliable signature of the solid-liquid
melting phase transition. The behaviour of such indices at other phase transitions has only partially been explored. These
and related applications are reviewed in the present article. 相似文献
89.
Chetan Nayak 《General Relativity and Gravitation》1991,23(9):981-989
Einstein-Maxwell theory in 2+1 dimensions is considered as a toy model for the 3+1 theory and as a means for understanding field theories without a background space-time geometry. Two possible approaches to the quantization of this theory are presented, one based on a Schwinger-Tomonaga time evolution equation and the other on a loop space construction, and the problems arising in both of these are discussed. 相似文献
90.
We propose to use the recently predicted two-dimensional "weak-pairing" px + ipy superfluid state of fermionic cold atoms as a platform for topological quantum computation. In the core of a vortex, this state supports a zero-energy Majorana mode, which moves to finite energy in the corresponding topologically trivial "strong-pairing" state. By braiding vortices in the "weak-pairing" state, unitary quantum gates can be applied to the Hilbert space of Majorana zero modes. For readout of the topological qubits, we propose realistic schemes suitable for atomic superfluids. 相似文献