全文获取类型
收费全文 | 546510篇 |
免费 | 11964篇 |
国内免费 | 5534篇 |
专业分类
化学 | 282591篇 |
晶体学 | 8037篇 |
力学 | 26551篇 |
综合类 | 298篇 |
数学 | 74650篇 |
物理学 | 171881篇 |
出版年
2022年 | 4031篇 |
2021年 | 4975篇 |
2020年 | 5622篇 |
2019年 | 5882篇 |
2018年 | 13590篇 |
2017年 | 14029篇 |
2016年 | 13584篇 |
2015年 | 7855篇 |
2014年 | 10682篇 |
2013年 | 22841篇 |
2012年 | 22018篇 |
2011年 | 31879篇 |
2010年 | 21302篇 |
2009年 | 21169篇 |
2008年 | 28229篇 |
2007年 | 30484篇 |
2006年 | 18446篇 |
2005年 | 21369篇 |
2004年 | 17439篇 |
2003年 | 15654篇 |
2002年 | 13848篇 |
2001年 | 14329篇 |
2000年 | 11149篇 |
1999年 | 8729篇 |
1998年 | 7317篇 |
1997年 | 6994篇 |
1996年 | 6890篇 |
1995年 | 6161篇 |
1994年 | 5995篇 |
1993年 | 5694篇 |
1992年 | 6296篇 |
1991年 | 6316篇 |
1990年 | 6021篇 |
1989年 | 5777篇 |
1988年 | 5774篇 |
1987年 | 5621篇 |
1986年 | 5309篇 |
1985年 | 6788篇 |
1984年 | 6889篇 |
1983年 | 5453篇 |
1982年 | 5525篇 |
1981年 | 5480篇 |
1980年 | 5054篇 |
1979年 | 5454篇 |
1978年 | 5587篇 |
1977年 | 5415篇 |
1976年 | 5388篇 |
1975年 | 4960篇 |
1974年 | 4932篇 |
1973年 | 4964篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
911.
L. C. Lew Yan Voon C. Galeriu M. Willatzen 《Physica E: Low-dimensional Systems and Nanostructures》2003,18(4):547-549
We argue that the two-dimensional elliptic quantum dot problem with finite barrier cannot be exactly solved, contrary to a recent assertion (van den Broek and Peeters, Physica E 11 (2001) 345. We also prove it explicitly by numerically calculating the correct energy spectrum. 相似文献
912.
报道了硅基有机微腔的电致发光(EL).该微腔由上半透明金属膜、中心有源多层膜和多孔硅分布Bragg反射镜(PS DBR)组成.半透明金属膜由Ag(20nm)构成,充当发光器件的负电极和微腔的上反射镜.有源多层膜由Al (1 nm) / LiF(05 nm) /Alq3/Alq3:DCJTB/NPB/CuPc/ITO/SiO2组成,其中的Al/LiF为电子注入层,ITO为正电极,SiO2为使正、负电极电隔离的介质层.该PS DBR是采用设备简单、成本低廉且非常省时的电化学腐蚀法用单晶Si来制备的;该PS
关键词:
电化学腐蚀
电致发光
窄峰发射
硅基有机微腔 相似文献
913.
The effect of bacterial and fungal activities on organic matter degradation in Brazilian soils was studied by a microcalorimetric method. Bacteria and fungi isolated from tropical soils and added to: Rhodic eutrudox (R), Typic eutrudox (V) and Quartzipsamment (Q) soils amended separately with moisture (control) (A) and 25% of cattle manure (E), municipal refuse compost (L), earthworm casts (H) or 23 μg of trifluralin (T) were investigated. The number of colony forming units in soil suspension was quantified by microscopy and inoculated in respective soil. All processes were measured at intervals of 7 days over a period of 35 days. The exothermic thermal effect (μJ) per cm3 of bacteria or fungi per gram of dry soil, respectively, for each substrate was: [(9±1), (4±1)] RA; [(478±24), (105±5)] RE; [(121±6), (71±4)] RL; [(121±6), (71±4)] RH; [(8±1); (3±1)] RT; [(10±1), (9±1] VA; [(347±17), (261±13)] VE; [(71±4), (28±1)] VL; [(22±1), (33±2)] VH; [(7±1), (10±1)] VT; [(19±1), (12±1)] QA; [(1301±65), (46±2)] QE; [(89±4), (9±1)] QL; [(130±7), (11±1)] QH; [(32±2), (8±1)] QT. The calorimetric values are higher for bacteria than for fungi. In general, the results showed higher activities in the soil amended with cattle manure than with other additives. 相似文献
914.
H. H. Salah M. Darwish A.-S. F. Obada 《International Journal of Theoretical Physics》2003,42(3):549-567
The odd excited negative binomial states are introduced using the photon creation operator by repeated application on negative binomialstates. These states interpolate between the odd displaced Fock states and the odd excited pure thermal states. In this paper both squeezing phenomena (normal squeezing and amplitude squared squeezing) are discussed. Besides discussion of the Glauber second-order correlation function, investigations are carried out for the quasi-probability distribution functions (Wigner function and Q-function). Finally the Pegg-Barnett phase probability distribution is computed for these states. 相似文献
915.
916.
本文对一般微分代数方程给出了几类可解集的概念,并讨论了多项式微分代数方程的可解集,得到子多项式系统具有唯一解。特别是有多于一个的解的条件,并得到了低次多项式在一定意义下的充分必要条件。 相似文献
917.
The fine-structure parameters of a series of configurations of the first ion of indium and the gyromagnetic ratios in intermediate coupling are calculated by a semiempirical method in the single-configuration approximation. 相似文献
918.
The OPAL Collaboration G. Abbiendi et al. 《The European Physical Journal C - Particles and Fields》2003,27(3):311-329
This paper describes topological searches for neutral scalar bosons S0 produced in association with a Z0 boson via the Bjorken process at centre-of-mass energies of 91 GeV and 183-209 GeV. These searches are based on studies of the recoil mass spectrum of
and events and on a search for with and S or photons. They cover the decays of the S0 into an arbitrary combination of hadrons, leptons, photons and invisible particles as well as the possibility that it might
be stable.
No indication for a signal is found in the data and upper limits on the cross section of the Bjorken process are calculated.
Cross-section limits are given in terms of a scale factor k with respect to the Standart Model cross section for the Higgs-strahlung process .
These results can be interpreted in general scenarios independently of the decay modes of the S0. The examples considered here are the production of a single new scalar particle with a decay width smaller than the detector
mass resolution, and for the first time, two scenarios with continuous mass distributions, due to a single very broad state
or several states close in mass.
Received: 13 March 2002 / Published online: 19 February 2003 相似文献
919.
V. N. Popov 《Technical Physics》2003,48(5):541-545
The slip velocity of a rarefied gas nonuniform in temperature and mass velocity is calculated for gas slip over the surface
of a right circular cylinder. The calculation uses the two-moment boundary condition in an approximation linear in Knudsen
number. Corrections to the slip velocity that are due to the interface curvature, volume temperature stresses, and nonuniform
temperature distribution in the Knudsen layer are studied as func-tions of the accommodation coefficients in the first two
moments of the distribution function. The Bhatnagar-Gross-Krook model of the Boltzmann kinetic equation is employed as the
basic equation for the gas state. 相似文献
920.