全文获取类型
收费全文 | 298024篇 |
免费 | 1560篇 |
国内免费 | 326篇 |
专业分类
化学 | 136940篇 |
晶体学 | 4653篇 |
力学 | 16876篇 |
综合类 | 3篇 |
数学 | 42018篇 |
物理学 | 99420篇 |
出版年
2021年 | 3095篇 |
2020年 | 3416篇 |
2019年 | 4190篇 |
2018年 | 6228篇 |
2017年 | 6440篇 |
2016年 | 7944篇 |
2015年 | 3521篇 |
2014年 | 6874篇 |
2013年 | 12108篇 |
2012年 | 10116篇 |
2011年 | 11784篇 |
2010年 | 9970篇 |
2009年 | 10132篇 |
2008年 | 11401篇 |
2007年 | 11196篇 |
2006年 | 9968篇 |
2005年 | 8606篇 |
2004年 | 8355篇 |
2003年 | 7763篇 |
2002年 | 8057篇 |
2001年 | 7665篇 |
2000年 | 6058篇 |
1999年 | 4489篇 |
1998年 | 4264篇 |
1997年 | 4126篇 |
1996年 | 3739篇 |
1995年 | 3301篇 |
1994年 | 3364篇 |
1993年 | 3381篇 |
1992年 | 3388篇 |
1991年 | 3788篇 |
1990年 | 3792篇 |
1989年 | 3794篇 |
1988年 | 3548篇 |
1987年 | 3629篇 |
1986年 | 3321篇 |
1985年 | 3852篇 |
1984年 | 4086篇 |
1983年 | 3490篇 |
1982年 | 3687篇 |
1981年 | 3375篇 |
1980年 | 3136篇 |
1979年 | 3621篇 |
1978年 | 3688篇 |
1977年 | 3855篇 |
1976年 | 3928篇 |
1975年 | 3672篇 |
1974年 | 3527篇 |
1973年 | 3691篇 |
1972年 | 3179篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
981.
Within the framework of free interaction theory numerical methods are used to investigate the occurrence of supersonic zones with shocks in the outer inviscid region for flow past roughness in the lower viscous sublayer, with and without the formation of local separation zones. 相似文献
982.
S. D. Gunapala S. V. Bandara J. K. Liu S. B. Rafol J. M. Mumolo C. A. Shott R. Jones J. Woolaway II J. M. Fastenau A. K. Liu M. Jhabvala K. K. Choi 《Infrared Physics & Technology》2003,44(5-6):411-425
A 9 μm cutoff 640 × 512 pixel hand-held quantum well infrared photodetector (QWIP) camera has been demonstrated with excellent imagery. A noise equivalent differential temperature (NEDT) of 10.6 mK is expected at a 65 K operating temperature with f/2 optics at a 300 K background. This focal plane array has shown background limited performance at a 72 K operating temperature with the same optics and background conditions. In this paper, we discuss the development of this very sensitive long-wavelength infrared camera based on a GaAs/AlGaAs QWIP focal plane array and its performance in quantum efficiency, NEDT, uniformity, and operability. In the second section of this paper, we discuss the first demonstration of a monolithic spatially separated four-band 640 × 512 pixel QWIP focal plane array and its performance. The four spectral bands cover 4–5.5, 8.5–10, 10–12, and 13.5–15 μm spectral regions with 640 × 128 pixels in each band. In the last section, we discuss the array performance of a 640 × 512 pixel broad-band (10–16 μm full-width at half-maximum) QWIP focal plane. 相似文献
983.
E. V. Karnaukh 《Ukrainian Mathematical Journal》2007,59(4):620-632
We consider almost upper-semicontinuous processes defined on a finite Markov chain. The distributions of functionals associated
with the exit of these processes from a finite interval are studied. We also consider some modifications of these processes.
__________
Translated from Ukrains’kyi Matematychnyi Zhurnal, Vol. 59, No. 4, pp. 555–565, April, 2007. 相似文献
984.
G. I. Petrashen V. V. Reshetnikov Yu. A. Surkov 《Journal of Mathematical Sciences》2007,142(6):2645-2654
A nonstationary problem concerning the propagation of low-frequency waves for a model that consists of a packet of elastic
layers lying on an elastic half-space is considered, and exact mathematical solutions in the form of repeated integrals are
constructed in three basic forms. It is proved that these solutions satisfy initial conditions. The representation of solutions
as a superposition of multiple waves is treated. Bibliography: 6 titles.
__________
Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 332, 2006, pp. 220–239. 相似文献
985.
A theorem on the existence of a G-representation and a differential-geometric criterion of the kinematic integrability for nonlinear differential equations
from the Λ2-G-classes is proved. Examples of zero-curvature representations and metrics for some equations of mathematical physics are
presented.
__________
Translated from Fundamental’naya i Prikladnaya Matematika (Fundamental and Applied Mathematics), Vol. 11, No. 1, Geometry,
2005. 相似文献
986.
The photogyrotropic properties of several mordant yellow azo dyes in gelatin and polymer matrices that are in the normal state or exposed to circularly polarized light are investigated. A model explanation for the experimental data is given. 相似文献
987.
S. A. Shiryaev M. V. Atamanov M. I. Guseva Yu. V. Martynenko A. V. Mitin V. S. Mitin P. G. Moskovkin 《Technical Physics》2002,47(2):238-243
It is suggested to produce metal-carbon composite coatings by magnetron sputtering of mosaic cathodes, which are Group IV,
V, and VI metals. The mosaic structure of the cathode elements are computer-optimized for each of the metals. Reflection electron
diffraction studies show that the coatings have the amorphous or nanocrystalline structures, which are thermally stable. The
coatings offer specific physical properties, in particular, low friction factor and high hardness. 相似文献
988.
989.
I. P. Raevskii L. A. Reznichenko M. P. Ivliev V. G. Smotrakov V. V. Eremkin M. A. Malitskaya L. A. Shilkina S. I. Shevtsova A. V. Borodin 《Crystallography Reports》2003,48(3):486-490
(Na, K)NbO3 crystals with a perovskite structure and a KNbO3 content up to 40 mol % were grown from flux with the use of the solvent NaBO2. The dielectric measurements of the crystals grown revealed phase transitions that had never been observed before in ceramic samples. 相似文献
990.
N. S. Zefirov N. V. Zyk E. K. Beloglazkina V. S. Tyurin 《Russian Chemical Bulletin》1995,44(2):315-317
Two systems for arene sulfenylation were investigated: arenesulfenamides in the presence of SO3 and sulfenylacetate complexes with AlBr3. A preference for the second reagent was demonstrated for sulfenylation of substrates bearing donor substituitents.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 324–326, February, 1995. 相似文献