全文获取类型
收费全文 | 31008篇 |
免费 | 1728篇 |
国内免费 | 1050篇 |
专业分类
化学 | 11130篇 |
晶体学 | 370篇 |
力学 | 950篇 |
综合类 | 121篇 |
数学 | 10162篇 |
物理学 | 11053篇 |
出版年
2023年 | 183篇 |
2022年 | 355篇 |
2021年 | 335篇 |
2020年 | 399篇 |
2019年 | 698篇 |
2018年 | 488篇 |
2017年 | 499篇 |
2016年 | 437篇 |
2015年 | 441篇 |
2014年 | 492篇 |
2013年 | 1661篇 |
2012年 | 827篇 |
2011年 | 1346篇 |
2010年 | 843篇 |
2009年 | 1265篇 |
2008年 | 1382篇 |
2007年 | 1455篇 |
2006年 | 1353篇 |
2005年 | 960篇 |
2004年 | 1328篇 |
2003年 | 1454篇 |
2002年 | 2347篇 |
2001年 | 2023篇 |
2000年 | 1840篇 |
1999年 | 1983篇 |
1998年 | 1727篇 |
1997年 | 1063篇 |
1996年 | 585篇 |
1995年 | 345篇 |
1994年 | 297篇 |
1993年 | 192篇 |
1992年 | 178篇 |
1991年 | 143篇 |
1990年 | 220篇 |
1989年 | 216篇 |
1988年 | 144篇 |
1987年 | 115篇 |
1986年 | 179篇 |
1985年 | 231篇 |
1984年 | 209篇 |
1983年 | 89篇 |
1982年 | 156篇 |
1981年 | 262篇 |
1980年 | 249篇 |
1979年 | 126篇 |
1978年 | 178篇 |
1977年 | 120篇 |
1976年 | 77篇 |
1975年 | 81篇 |
1974年 | 77篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
Hyperfine Interactions - Rotational J=1→J=0 transitions in muonic molecule, (3Heμd) J ++, in [(3Heμd)++,2e]–D and [(3Heμd)++,e]+–D collisions are considered. The... 相似文献
152.
J.T. Devaraju B.H. Sharmila S. Asokan K.V. Acharya 《Applied Physics A: Materials Science & Processing》2002,75(4):515-518
The electrical switching behaviour of As45Te55-xInx (5≤x≤15) and As50Te50-xInx (2.5≤x≤11.5) has been studied over a wide range of compositions. These glasses are found to exhibit threshold switching.
The composition dependence of switching voltage (Vt) has been found to exhibit a change in slope and a local minimum at compositions x=10 and 12.5 for As45Te55-xInx and x=7.5 and 10.8 for As50Te50-xInx, respectively. The slope change in Vt verses x and the local minimum have been identified using two network topological effects, namely the rigidity percolation
threshold and the chemical threshold.
Received: 23 August 2001 / Accepted: 27 August 2001 / Published online: 11 February 2002 相似文献
153.
Laser driven shocks can lead to a dynamic failure, called film spallation. Here, we use a modified laser spallation set-up
to measure the dynamic adhesion of thin films and we propose a novel diagnostic technology. Based on correlation theory, new
spallation criteria for characterizing the progressive damage at the interface between the film and the substrate are established,
such as interface delamination, film spallation and film expulsion. With the help of the theory, the degree of damage and
the dimension of damage (i.e. fracture), such as the minimum width of delamination radius, the thickness of the film etc.,
are estimated. Experiments are carried out on epoxy/stainless steel and epoxy/Al, and the experimental results show that their
dynamic bonding strengths are about 25 MPa and 20 MPa, respectively. The detailed results, analyses and discussions are presented
in this paper.
Received: 6 February 2001 / Accepted: 3 December 2001 / Published online: 11 February 2002 相似文献
154.
We study the propagation of the light mesons σ,ω,ρ, and a0(980) in dense hadronic matter in an extended derivative scalar coupling model. Within the scheme proposed it is possible
to unambiguously define effective density-dependent couplings at the Lagrangian level. We first apply the model to study asymmetric
nuclear matter with fixed isospin asymmetry, and then we pay particular attention to hypermatter in β-equilibrium. The equation
of state and the potential contribution to the symmetry coefficient arising from the mean-field approximation are investigated.
Received: 16 October 2001 / Accepted: 10 January 2002 相似文献
155.
S. Zschocke G. Plunien G. Soff 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(2):147-156
The renormalization method of Bogoljubov-Parasiuk-Hepp-Zimmermann (BPHZ) is used in order to derive the renormalized energy
shift due to the gauge invariant K?llén-Sabry diagram of the two-photon vacuum polarization (VPVP) as well as the self energy
vacuum polarization S(VP)E beyond the Uehling approximation. It is outlined, that no outer renormalization is required for
the two-photon vacuum polarization and that only the inner renormalization has to be accomplished. It is shown that the so-called
nongauge invariant spurious term is absent for a wide class of vacuum polarization (VP) diagrams if one applies the widely
used spherical expansion of bound and free-electron propagator. This simplifies significantly calculations in bound state
quantum electrodynamics. As one result of our paper the use of the BPHZ-approach in bound state QED is established.
Received 28 September 2001 相似文献
156.
Sadaharu Jo 《Applied Surface Science》2006,252(10):3514-3519
The morphologies and lattice structures of anthracene single crystals grown from the vapor phase were investigated using optical microscopy, phase contrast microscopy, atomic force microscopy (AFM), and X-ray diffraction analysis. Common morphologies with hexagonal large planes were observed irrespective of crystal size. The observation of certain surface morphologies with a phase contrast microscopy revealed that the spiral steps originated from screw dislocations present on the (0 0 1) planes. Moreover, the center and edge of the (0 0 1) planes had large curvatures, similar to hills. Resultantly, quarter-monolayer (ML) steps were observed on the large and flat planes between both hills. 相似文献
157.
The possibility that pairs of quarks will form diquark clusters in the regime above deconfinement transition for hadron matter
at finite density is revisited. Here we present the results on the diquark-diquark (dq-dq) interaction in the framework of
constituent quark model taking account of spin, isospin and color degrees of freedom in the spirit of generalized Pauli principle.
By constructing the appropriate spin and color states of the dq-dq clusters we compute the expectation values of the interaction
Hamiltonian involving pairwise quark—quark interaction. We find that the effective interaction between two diquark clusters
is quite sensitive to different configurations characterized by color and spin states, obtained after the coupling of two
diquark states. The value of the coupling parameter for a particular color—spin state, i.e., -3, 1 is compared to the one
obtained earlier by Donoghue and Sateesh,Phys. Rev.
D38, 360 (1988) based on the effective Φ4-theory. This new value of λ derived for different color-spin dq-dq states, may lead to several important implications in
the studies of diquark star and diquark gas. 相似文献
158.
We have investigated the free energy of formation for AgxIn1-x and AgxSn1-x liquid binary alloys at temperatures 1173 and 1250 K, respectively. A microscopic theory based on the first order perturbation has been applied. The interionic interaction and a reference liquid are the fundamental components of the theory. The interionic interaction is described by a local pseudopotential. A liquid of hard spheres (HS) of two different effective diametres and charges is used to describe the reference system. The results of the calculations for energy of formation agree very well with the available experimental data. Our calculations also reveal that a simple perturbative approach along with appropriate effective pair potentials can produce nearly quantitative results for the concerned alloys. 相似文献
159.
On the third largest Laplacian eigenvalue of a graph 总被引:1,自引:0,他引:1
Ji-Ming Guo 《Linear and Multilinear Algebra》2007,55(1):93-102
In this article, a sharp lower bound for the third largest Laplacian eigenvalue of a graph is given in terms of the third largest degree of the graph. 相似文献
160.