全文获取类型
收费全文 | 96803篇 |
免费 | 598篇 |
国内免费 | 141篇 |
专业分类
化学 | 48892篇 |
晶体学 | 1575篇 |
力学 | 4058篇 |
综合类 | 12篇 |
数学 | 10753篇 |
物理学 | 32252篇 |
出版年
2022年 | 719篇 |
2021年 | 1166篇 |
2020年 | 1256篇 |
2019年 | 1533篇 |
2018年 | 2367篇 |
2017年 | 2537篇 |
2016年 | 3180篇 |
2015年 | 1443篇 |
2014年 | 2570篇 |
2013年 | 4563篇 |
2012年 | 4076篇 |
2011年 | 4517篇 |
2010年 | 4053篇 |
2009年 | 3996篇 |
2008年 | 4355篇 |
2007年 | 4173篇 |
2006年 | 3946篇 |
2005年 | 3132篇 |
2004年 | 2744篇 |
2003年 | 2337篇 |
2002年 | 2407篇 |
2001年 | 2501篇 |
2000年 | 2152篇 |
1999年 | 1547篇 |
1998年 | 1503篇 |
1997年 | 1412篇 |
1996年 | 985篇 |
1995年 | 854篇 |
1994年 | 835篇 |
1993年 | 815篇 |
1992年 | 873篇 |
1991年 | 940篇 |
1990年 | 891篇 |
1989年 | 910篇 |
1988年 | 823篇 |
1987年 | 774篇 |
1986年 | 747篇 |
1985年 | 870篇 |
1984年 | 963篇 |
1983年 | 825篇 |
1982年 | 839篇 |
1981年 | 749篇 |
1980年 | 705篇 |
1979年 | 769篇 |
1978年 | 894篇 |
1977年 | 917篇 |
1976年 | 811篇 |
1975年 | 777篇 |
1974年 | 793篇 |
1973年 | 763篇 |
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
111.
Jun-tao Chang Joerg Evers Marian O. Scully M. Suhail Zubairy 《量子光学学报》2006,12(B08):77-77
We propose a scheme to obtain the distance of two identical atoms placed inside the standing wave field by monitoring the collective resonance fluorescence spectrum emitted by the two particles. We find three different parameter ranges, depending on the distance of the atoms as compared to the transition wavelength. For large interparticle distances, dipole-dipole coupling is negligible, and the main system evolution arises from the interaction with the standing wave field. In the small-distance limit, the dynamics is dominated by the dipole-dipole interaction. Finally, in the intermediate region, a rich interplay of the various couplings arises, which however is lifted for strong driving laser fields. The present measurement procedure allows us to distinguish the three cases. In each of the cases, we show how to determine the distance of the two particles and their respective positions relative to the nodes of the standing wave field with fractional-wavelength precision. 相似文献
112.
S. N. Solov’ev K. A. Minasyan A. A. Korunov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2006,80(4):663-664
The enthalpies of reactions of La2CoO4(cr) and CoCl2(cr) with hydrochloric acid were measured with an isothermal-jacket calorimeter. The results obtained and the available literature data were used to calculate the standard enthalpy of formation of La2CoO4(cr) at 298.15 K, Δf H o = ?2179 ± 7 kJ/mol. 相似文献
113.
A noiselike fine structure of ferromagnetic resonance spectra in magnetic powders was investigated after ultrasonic treatment. Magnetic interactions between particles are proved to have an influence upon the fine structure formation. After decreasing dipole-dipole magnetic interactions in dilute suspension a special order appears in fine-structure spectra, which is generally the same for different systems. 相似文献
114.
The critical fields of the valence transition induced by a magnetic field in the EuNi2(Si1?x Gex)2 (x=0.5–0.75) compound in an intermediate valence state are measured. The magnetic-field-induced valence transition is observed in the low-concentration range down to x=0.5. It is demonstrated that the critical field increases linearly with a decrease in the germanium concentration. 相似文献
115.
Discharges with liquid nonmetallic electrodes of much interest for applications are investigated. It is found that a dc discharge between two streams of tap water in air at atmospheric pressure is stable at a currentof 40≤I≤100 mA. The discharge exists in the diffuse (volume) form with a relatively low current density (∼0.2 A/cm2) and a high (above one kilovolt) voltage drop across the air gap (∼1 cm) between the water electrodes. The current density and voltage depend only slightly on the discharge current. Probe measurements show that three regions can be distinguished in the discharge: two electrode regions (1–2 mm in length) and a discharge column with a constant electric field of ≈0.8 kV/cm (i.e., E/N≈20 Td, because the gas in the discharge is heated up to 1500–2000 K). The average electric field strength near the electrodes is E≈2–3×103 V/cm (E/N≈60–80 Td). The charged particle density in the column is n ∼ 1012 cm−3. The probe measurements of n agree with the previous microwave absorption measurements. The water vapor concentration in the column is also estimated from probe measurements. 相似文献
116.
The influence of interatomic distances on magnetic ordering in RMnSi compounds (R=La, Y, Sm, and Gd)
S. A. Nikitin T. I. Ivanova Yu. A. Ovchenkova M. V. Maslennikova G. S. Burkhanov O. D. Chistyakov 《Physics of the Solid State》2002,44(2):308-311
Magnetic ordering in the RMnSi (R=La, Y, Sm, and Gd) compounds is investigated. It is found that the type of magnetic ordering depends on the d Mn-Mn distance between manganese atoms inside the magnetic layers located in the planes perpendicular to the c axis. This inference is based on the results of studies performed with SmMnSi and GdMnSi compounds in which the distances between manganese atoms are close to the critical value d Mn-Mn that corresponds to the crossover between ferromagnetic and antiferromagnetic ordering in RMnSi compounds. The introduction of lanthanum and yttrium atoms into the rare-earth sublattice leads to an increase and a decrease in the unit cell size, respectively, and brings about magnetic phase transitions in the compounds under investigation. 相似文献
117.
E. V. Kuz’min 《Physics of the Solid State》2002,44(6):1122-1129
The spin system of the Heisenberg model (s=1/2) on a square lattice with antiferromagnetic (AFM) exchange between nearest neighbors (in which there is no long-range magnetic order at any T≠0) is treated as a spatially homogeneous isotropic spin liquid. The double-time temperature Green’s function method is used in the framework of a second-step decoupling scheme. It is shown that, as T → 0, the spin liquid goes over (without any change in symmetry) to a singlet state with energy (per bond) ?0=?0.352 and the correlation length diverges as ξ ∝ T ?1 exp(T 0/T). The spatial spin correlators oscillate in sign with distance, as in the AFM state. The theory allows one to calculate the main characteristics of the system in all temperature ranges. 相似文献
118.
N. L. Dmitruk O. Yu. Borkovskaya R. V. Konakova I. B. Mamontova S. V. Mamykin D. I. Voitsikhovskiy 《Technical Physics》2002,47(6):698-702
The effect of 60Co gamma irradiation at doses of 103-2×105 Gy on the photoconversion and dark I-V characteristics of Au/GaAs surface-barrier solar cells (SCs) is studied. The morphology of the interface microrelief is varied
to reach the highest photoconversion efficiency. Of the two types of microrelief morphology (dendritic and quasi-grating)
obtained by the chemical anisotropic etching of n-(100)GaAs, the latter is more promising, particularly for SCs designed for space application, since the associated SCs offer
higher efficiency and radiation resistance. 相似文献
119.
Sanzharov N. A. Yarovoi A. T. Bekhtereva E. S. Ulenikov O. N. 《Russian Physics Journal》2002,45(10):1024-1031
Analytical formulas are derived that describe the dependences of the transition probabilities in vibrational-rotational spectra of XY3-type molecules with C
3v
symmetry on the rotational quantum numbers. 相似文献
120.
We analyze diffusion from a periodic array of hemispherical droplets through a membrane. We find that the multiple sources do not interact strongly, even when the droplets are closely spaced, so that the flux through the membrane appears nearly additive. 相似文献