全文获取类型
收费全文 | 4803篇 |
免费 | 154篇 |
国内免费 | 12篇 |
专业分类
化学 | 2889篇 |
晶体学 | 88篇 |
力学 | 152篇 |
数学 | 362篇 |
物理学 | 1478篇 |
出版年
2023年 | 45篇 |
2022年 | 94篇 |
2021年 | 87篇 |
2020年 | 105篇 |
2019年 | 99篇 |
2018年 | 119篇 |
2017年 | 88篇 |
2016年 | 143篇 |
2015年 | 117篇 |
2014年 | 170篇 |
2013年 | 273篇 |
2012年 | 357篇 |
2011年 | 351篇 |
2010年 | 206篇 |
2009年 | 178篇 |
2008年 | 204篇 |
2007年 | 199篇 |
2006年 | 190篇 |
2005年 | 154篇 |
2004年 | 119篇 |
2003年 | 124篇 |
2002年 | 90篇 |
2001年 | 75篇 |
2000年 | 62篇 |
1999年 | 56篇 |
1998年 | 35篇 |
1997年 | 54篇 |
1996年 | 64篇 |
1995年 | 46篇 |
1994年 | 77篇 |
1993年 | 82篇 |
1992年 | 82篇 |
1991年 | 53篇 |
1990年 | 51篇 |
1989年 | 54篇 |
1988年 | 35篇 |
1987年 | 39篇 |
1986年 | 37篇 |
1985年 | 37篇 |
1984年 | 33篇 |
1983年 | 37篇 |
1982年 | 39篇 |
1981年 | 50篇 |
1980年 | 40篇 |
1979年 | 31篇 |
1978年 | 26篇 |
1977年 | 34篇 |
1975年 | 24篇 |
1974年 | 27篇 |
1973年 | 33篇 |
排序方式: 共有4969条查询结果,搜索用时 0 毫秒
101.
Meccanica - A particular hydro-elastic model is considered to examine a radiation problem involving an immersed sphere in an infinitely extended ice-covered sea, where the lower surface is... 相似文献
102.
Basak Anirban Sadhu Arindam Das Kunal Sharma Kapil K. 《International Journal of Theoretical Physics》2019,58(9):3158-3179
In this paper, an attempt is made to present a method of quantum cost minimization or optimization technique for quantum reversible circuits using proposed merger rules in Exclusive Sum of Product (ESOP) method. These modified ESOP methods are used to minimize the quantum circuits. We found that the quantum cost is drastically decreased than the previous ESOP method. It will be easy to find the quantum cost and quantum gate optimized quantum circuits implementation. It will also reduce quantum error while the quantum circuit is executed in real quantum processor.
相似文献103.
Tania Chowdhury Kaushik Bera Debabrata Samanta Sandip Dolui Suvendu Maity Nakul C. Maiti Prasanta Kumar Ghosh Debasis Das 《应用有机金属化学》2020,34(4):e5556
Four new zinc (II) complexes [Zn (HL1H)Br2] (1), [Zn (HL1H)Cl2] (2), [Zn2(HL2)Br3] (3), and [Zn (HL2)Cl] (4) have been synthesized by adopting template synthetic strategy and utilizing two homologous Schiff base ligands (H2L1 = 4-bromo-2-{[2-(2-hydroxyethylamino)-ethylimino]-methyl}-6-methoxyphenol, H2L2 = 4-bromo-2-{[3-(2-hydroxyethylamino)propylimino]methyl}-6-methoxyphenol), differing in one -CH2- unit in the ligating backbone, by adopting template synthetic strategy. All the complexes have been characterized by single crystal X-ray diffraction analysis as well as by other routine physicochemical techniques. Ligand mediated structural variations have been observed and rationalized by density functional theoretical (DFT) calculations. Interaction of the complexes 1–4 with Bovine Serum Albumin protein (BSA) has been studied by different spectroscopic techniques. A complete thermodynamic profile (ΔHo, ΔSo and ΔGo) was evaluated initially from the change in absorption and fluorescence spectra upon addition of BSA to the complexes. Appreciable binding constant values in the range ~ 0.94–4.51 × 104 M−1 indicate efficient binding tendency of the complexes to BSA with the sequence 1 ≅ 2 > 3 ≅ 4. Circular dichroism (CD), isothermal calorimetric titration experiments, molecular docking and molecular dynamics have been performed to gain deep insight into the binding regions of complex 1 to BSA. Experimental evidences suggest an interaction of zinc complexes at the surface of BSA protein and this particular binding has been exploited to determine unknown concentration of BSA protein. For this purpose complex 1 was explored as a BSA protein quantification tool. 相似文献
104.
Generalized quantum measurements with two outcomes are fully characterized by two real parameters, dubbed as sharpness parameter and biasedness parameter and they can be linked with different aspects of the experimental setup. It is known that sharpness parameter characterizes precision of the measurements and decreasing sharpness parameter of the measurements reduces the possibility of probing quantum features like quantum mechanical (QM) violation of local-realism (LR) or macro-realism (MR). Here we investigate the effect of biasedness together with that of sharpness of measurements and find a trade-off between those two parameters in the context of probing QM violations of LR and MR. Interestingly, we also find that the above mentioned trade-off is more robust in the latter case. 相似文献
105.
A. Das 《International Journal of Theoretical Physics》1980,19(10):745-757
Within the context of a manifestly covariant massive Abelian gauge field model, it is demonstrated that a mass is genuinely compatible with the existence of a bonafide Goldstone boson. Some arguments have been placed to claim that this Goldstone boson may occupy a physical sector of the Hilbert space and as a consequence, at the zero momentum limit, is shown to connect the spectral measure to the bare coupling constant through the Higgs meson mass. It is conjectured that this Goldstone boson can be recognized to invoke a class of Brans-Dicke scalars of the scalar-tensor theory of gravitation. 相似文献
106.
Amal K. Das 《Zeitschrift für Physik B Condensed Matter》1981,40(4):353-357
The Brownian motion of an ensemble of charged particles in a quantizing magnetic field is considered in a simple quasi-classical model. The model describes random jumps between the Landau levels—corresponding to the quantized motion perpendicular to the magnetic field, and markovian fluctuations in momentum space—corresponding to the classical motion parallel to the field. A random walk dynamics is adopted for the former while an Ornstein-Uhlenbeck process is considered for the latter. The resulting Fokker-Planck equations constitute a semi-quantum stochastic process. The equations are solved and several physical aspects of the underlying system are discussed. 相似文献
107.
Understanding of the basic nature of arc root fluctuation is still one of the unsolved problems in thermal arc plasma physics.
It has direct impact on myriads of thermal plasma applications being implemented at present. Recently, chaotic nature of arc
root behavior has been reported through the analysis of voltages, acoustic and optical signals which are generated from a
hollow copper electrode arc plasma torch. In this paper we present details of computations involved in the estimation process
of various dynamic properties and show how they reflect chaotic behavior of arc root in the system. 相似文献
108.
The electric field gradients at27Al and63Cu nuclei which are nearest neighbors to the muon in the face-centered cubic metals aluminum and copper, with muon at an octahedral
interstitial site, are studied. The electron density fluctuations needed for the evaluation of the electronic, or valence,
contributions to field gradients are taken from earlier investigations involving the spherical solid approximation. The enhancement
factors a that have to be applied to the electric field-gradients obtained from these approximations, due to the departures
of the electronic wave-functions from plane-wave character, and the incorporation of antishielding effects, have been obtained
for both APW and OPW approaches to the conduction electron wave-functions and good agreement is found between the results
by the two approaches. Size effects due to the lattice distortion associated with the presence of the muon are included through
actual point ion summations using available calculated displacements of the ions surrounding the muon. The valence contributions
are the dominant ones but the size effect contributions are also significant. The net field-gradient obtained for the27Al site is significantly smaller than experiment while that for63Cu is substantially larger than experiment. Possible sources that could lead to better agreement with experiment are discussed
and it is concluded that major improvement is needed in the valence effect contributions in both metals. 相似文献
109.
We extend the method of path integrals to obtain the solution of the chiral Schwinger model in curved space-time and compare it with the flat space-time solution. 相似文献
110.
The k‐th power of a graph G, denoted by , is a graph with the same set of vertices as G such that two vertices are adjacent in if and only if their distance in G is at most k. In this paper, we give the bounds on the spectral radius of and . The Nordhaus–Gaddum‐type inequality for the spectral radius of the graph is also presented. Moreover, we obtain an upper bound on the energy of the second power of graphs. 相似文献