全文获取类型
收费全文 | 389876篇 |
免费 | 8046篇 |
国内免费 | 5947篇 |
专业分类
化学 | 197257篇 |
晶体学 | 5402篇 |
力学 | 20460篇 |
综合类 | 380篇 |
数学 | 57795篇 |
物理学 | 122575篇 |
出版年
2021年 | 3452篇 |
2020年 | 3912篇 |
2019年 | 4189篇 |
2018年 | 12520篇 |
2017年 | 13051篇 |
2016年 | 10206篇 |
2015年 | 5324篇 |
2014年 | 6806篇 |
2013年 | 13454篇 |
2012年 | 15911篇 |
2011年 | 24776篇 |
2010年 | 16391篇 |
2009年 | 16320篇 |
2008年 | 21788篇 |
2007年 | 24616篇 |
2006年 | 11878篇 |
2005年 | 15960篇 |
2004年 | 12244篇 |
2003年 | 11359篇 |
2002年 | 9699篇 |
2001年 | 9064篇 |
2000年 | 7117篇 |
1999年 | 5146篇 |
1998年 | 4468篇 |
1997年 | 4203篇 |
1996年 | 4324篇 |
1995年 | 3678篇 |
1994年 | 3847篇 |
1993年 | 3622篇 |
1992年 | 3814篇 |
1991年 | 3931篇 |
1990年 | 3736篇 |
1989年 | 3575篇 |
1988年 | 3427篇 |
1987年 | 3331篇 |
1986年 | 3318篇 |
1985年 | 4163篇 |
1984年 | 4196篇 |
1983年 | 3551篇 |
1982年 | 3769篇 |
1981年 | 3497篇 |
1980年 | 3234篇 |
1979年 | 3537篇 |
1978年 | 3766篇 |
1977年 | 3703篇 |
1976年 | 3867篇 |
1975年 | 3521篇 |
1974年 | 3630篇 |
1973年 | 3718篇 |
1972年 | 2958篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
An overview of theoretical and experimental studies of the coherent type-B e
+
e-pair production by photons in aligned crystals performed at Nuclear Physics Institute at Tomsk Polytechnic University is given. 相似文献
82.
M. A. Augustyniak-Jabłokow K. Łukaszewicz A. Pietraszko V. E. Petrashen Yu. V. Yablokov 《Physics of the Solid State》2002,44(8):1480-1483
The EPR spectra evolution of Cs2Zn1?x Cux(ZrF6)2 · 6H2O (x=0.01, 0.6, 0.8, and 1.0) in the temperature range 4.2–330 K and the x-ray structure analysis of the compound with x=1.0 in the range 150–327 K show that the Jahn-Teller (JT) complex Cu(H2O)6 coordination sphere undergoes a plastic deformation. The observed effect is due to the combined influence of small lattice strains existing in the paraphase and a new one appearing as a result of a ferroelastic phase transition and increasing with decreasing temperature below T c . It is proved that both cooperative interactions between JT complexes and ferroelastic strain stabilize a certain JT configuration. The problem of instability of a JT configuration compressed at T ~ 265 K is discussed. 相似文献
83.
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
84.
B. Dubrulle F. Hersant 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(3):379-386
We generalize an analogy between rotating and stratified shear flows. This analogy is summarized in Table 1. We use this analogy
in the unstable case (centrifugally unstable flow vs. convection) to compute the torque in Taylor-Couette configuration, as a function of the Reynolds number. At low Reynolds
numbers, when most of the dissipation comes from the mean flow, we predict that the non-dimensional torque G = T/ν2
L, where L is the cylinder length, scales with Reynolds number R and gap width η, G = 1.46η3/2(1 - η)-7/4
R
3/2. At larger Reynolds number, velocity fluctuations become non-negligible in the dissipation. In these regimes, there is no
exact power law dependence the torque versus Reynolds. Instead, we obtain logarithmic corrections to the classical ultra-hard (exponent 2) regimes: G = 0.50
. These predictions are found to be in excellent agreement with avail-able experimental data. Predictions for scaling of velocity
fluctuations are also provided.
Received 7 June 2001 and Received in final form 7 December 2001 相似文献
85.
86.
87.
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
88.
89.
90.