全文获取类型
收费全文 | 344131篇 |
免费 | 2067篇 |
国内免费 | 727篇 |
专业分类
化学 | 170679篇 |
晶体学 | 5266篇 |
力学 | 18364篇 |
综合类 | 32篇 |
数学 | 42867篇 |
物理学 | 109717篇 |
出版年
2020年 | 3449篇 |
2019年 | 4292篇 |
2018年 | 6321篇 |
2017年 | 6415篇 |
2016年 | 8243篇 |
2015年 | 4015篇 |
2014年 | 7263篇 |
2013年 | 14586篇 |
2012年 | 11506篇 |
2011年 | 13526篇 |
2010年 | 11190篇 |
2009年 | 11418篇 |
2008年 | 12960篇 |
2007年 | 12779篇 |
2006年 | 11330篇 |
2005年 | 9938篇 |
2004年 | 9409篇 |
2003年 | 8472篇 |
2002年 | 8590篇 |
2001年 | 9526篇 |
2000年 | 7201篇 |
1999年 | 5488篇 |
1998年 | 4899篇 |
1997年 | 4835篇 |
1996年 | 4327篇 |
1995年 | 3805篇 |
1994年 | 3872篇 |
1993年 | 3810篇 |
1992年 | 4083篇 |
1991年 | 4427篇 |
1990年 | 4307篇 |
1989年 | 4367篇 |
1988年 | 4176篇 |
1987年 | 4176篇 |
1986年 | 3919篇 |
1985年 | 5004篇 |
1984年 | 5049篇 |
1983年 | 4295篇 |
1982年 | 4366篇 |
1981年 | 4216篇 |
1980年 | 3894篇 |
1979年 | 4468篇 |
1978年 | 4583篇 |
1977年 | 4771篇 |
1976年 | 4839篇 |
1975年 | 4517篇 |
1974年 | 4397篇 |
1973年 | 4637篇 |
1972年 | 3652篇 |
1971年 | 3388篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
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
62.
The present paper analyzes the properties of structural phase transitions under the extremal conditions of high pressures. In the context of the theory of density functional (TDF), the pressures of the B1–B2 transitions are calculated for small alkali-halide crystals as functions of the crystal size. The size effect of the B1–B2 transition – an increase in the transition pressure with the decreasing crystal grain radius – has been established for all investigated halides except lithium fluoride for which the dependence is reverse. 相似文献
63.
64.
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
65.
66.
It is proved that biorthogonal polynomials obey two different kinds of Christoffel-Darboux-type formulae, one linking polynomials with a different parameter and one combining polynomials with different degrees. This is used to produce a mixed recurrence relation, which is valid for all biorthogonal polynomials. This recurrence relation establishes several results on interlacing property of zeros of successive biorthogonal polynomials and leads to a new result on the interlace of zeros of orthogonal polynomials (of equal degrees) with respect to two distributionsdψ(x) andx p dψ(x), 0<p≤1, with support in either [0, 1] or [1, ∞). 相似文献
67.
68.
Results of an experiment on investigating the fluctuations of a sound signal with a frequency of 295 Hz on a stationary 32-km-long acoustic path in a shallow sea are presented. Hydrological conditions on the path were characterized by the presence of a weak thermocline and a frequent occurrence of intense internal wave trains. The space-time characteristics of these internal waves were measured in detail. Experimental evidence of the repetition of the forms of internal solitons in the variations of the amplitude and phase of an acoustic signal was obtained. 相似文献
69.
Possibilities for the control of the parameters of free-polarization decay (FPD), optical nutation, and photon echo (PE) using the dressing field are studied. Coherent transients are generated with the Stark switching technique and are detected in the radiation of the probe field polarized orthogonally to the dressing field. The evolution-operator technique is employed in the calculations. The experiments are performed at the R(4, 3) transition of the 0 ? 1 v3 13CH3F vibrational band with the radiation of a cw CO2 laser. It is theoretically and experimentally demonstrated that FPD and PE are suppressed upon an increase in the intensity of the dressing field. The observed shapes of the transient FPD and PE signals and their variations with the dressing field intensity are in qualitative agreement with the results of the calculations. 相似文献
70.