全文获取类型
收费全文 | 332433篇 |
免费 | 3373篇 |
国内免费 | 933篇 |
专业分类
化学 | 173086篇 |
晶体学 | 5013篇 |
力学 | 15141篇 |
综合类 | 10篇 |
数学 | 36698篇 |
物理学 | 106791篇 |
出版年
2021年 | 2477篇 |
2020年 | 2750篇 |
2019年 | 2999篇 |
2018年 | 3924篇 |
2017年 | 3821篇 |
2016年 | 5818篇 |
2015年 | 3621篇 |
2014年 | 5675篇 |
2013年 | 14582篇 |
2012年 | 11326篇 |
2011年 | 13884篇 |
2010年 | 9561篇 |
2009年 | 9470篇 |
2008年 | 12599篇 |
2007年 | 12795篇 |
2006年 | 12161篇 |
2005年 | 11006篇 |
2004年 | 10005篇 |
2003年 | 8844篇 |
2002年 | 8722篇 |
2001年 | 9922篇 |
2000年 | 7642篇 |
1999年 | 5887篇 |
1998年 | 4934篇 |
1997年 | 4895篇 |
1996年 | 4485篇 |
1995年 | 4235篇 |
1994年 | 4054篇 |
1993年 | 3807篇 |
1992年 | 4351篇 |
1991年 | 4444篇 |
1990年 | 4206篇 |
1989年 | 4021篇 |
1988年 | 4005篇 |
1987年 | 3940篇 |
1986年 | 3698篇 |
1985年 | 4873篇 |
1984年 | 5181篇 |
1983年 | 4268篇 |
1982年 | 4583篇 |
1981年 | 4413篇 |
1980年 | 4244篇 |
1979年 | 4469篇 |
1978年 | 4721篇 |
1977年 | 4565篇 |
1976年 | 4664篇 |
1975年 | 4376篇 |
1974年 | 4405篇 |
1973年 | 4524篇 |
1972年 | 2959篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
A plasma reactor that has a transient traveling arc has been used to study hydrogen in relation to in-flight reduction of metal oxide particles. Experiments were done to determine the nature of the arc and its interaction with the reactor gas. The lifetime of the excited atomic hydrogen was measured and it was found to be more than 4 ms after the arc had ceased. Powders and tablets of oxides were exposed to the pulsed-arc treated hydrogen and found to react much more rapidly and intensely than when exposed to hot molecular hydrogen. The results suggest that atomic hydrogen will exist throughout the volume of such a reactor for a period that is sufficient to reduce particles of FeO, Cr2O3, and TiO2. 相似文献
992.
A generalization of the Bloembergen-Shen model to Raman active molecules with an arbitrary number of normal modes was suggested. The generalized model was used to study Raman echo signal characteristics when a system of molecules was excited by pulses of widths up to one period of optical oscillations. It was shown that a large number of echo responses on Stokes and anti-Stokes components could arise even under a two-pulse action in a continuous monochromatic pumping field. The number of echo responses depended on the number of molecular normal modes and the geometry of measurements. At small exciting pulse “areas,” the echo responses whose Stokes and anti-Stokes components corresponded to normal vibrational modes of a molecule had the highest intensity, whereas the components formed by normal mode combinations were strongly suppressed. 相似文献
993.
994.
Data on the proteinase complex from Carica papaya latex were reviewed. The properties and applications of the domestic preparation cucumazyme and known medicinal preparations based on papaya proteinases (caripazyme, lecozyme, lecopain) were compared. 相似文献
995.
M. De Falco F. De Giovanni C. Musella R. Schmidt 《Rendiconti del Circolo Matematico di Palermo》2003,52(1):70-76
A subgroupH of a groupG is said to bepermutable ifHX=XH for every subgroupX ofG. In this paper the structure of groups in which every subgroup either is abelian or permutable is investigated.
This work was done while the last author was visiting the University of Napoli Federico II. He thanks the “Dipartimento di
Matematica e Applicazioni” for its financial support. 相似文献
996.
Pre—Separation Axioms in Fuzzifying Topology 总被引:1,自引:0,他引:1
K.M.AbdEl-Hakeim F.M.Zeyada 《模糊系统与数学》2003,17(1):28-36
1 IntroductionYing[5,6 ] introduced and elementally developed so called fuzzifying topology with the semanticmethod of continuous valued L ogic.Shen[7] introduced and studied T0 -,T1-,T2 (Hausdorff) -,T3(regularity) -,T4 (normality) -separation axioms in fuzzifying topology.In [3 ]the concepts of thefamily of fuzzifying pre-open sets,fuzzifying pre-neighbourhood structure of a point and fuzzifyingpre-closure are introduced and studied.It is worth to mention that pre-separation axioms are … 相似文献
997.
998.
V. P. Belousov I. M. Belousova A. S. Grenishin O. B. Danilov V. M. Kiselev A. V. Kris’ko A. A. Mak T. D. Murav’eva V. N. Sosnov 《Optics and Spectroscopy》2003,95(6):830-832
The possibility of lasing in the fullerene-oxygen-iodine system with optical excitation of fullerene is studied. Laser radiation with an energy of 25 mJ and a pulse duration of 5–10 ms is obtained. 相似文献
999.
The effect of dynamical exchange interactions on the dielectric function of a two-dimensional electron gas is studied using a variational approach. Exchange effects are introduced via the local-field correction. The variationally obtained local-field factor is compared to the earlier perturbative result to first order in the electron-electron interaction. 相似文献
1000.
L. G. Lumbreras R. Gebhard W. Häusler F. Kauffmann-Doig J. Riederer G. Sieben U. Wagner 《Hyperfine Interactions》2003,150(1-4):51-72
Ceramic finds from the Galería de las Ofrendas at Chavín de Huántar and surface finds from the settlement of Chavín were characterised by combining the results of archaeological typology with archaeometric studies using neutron activation analysis, Mössbauer spectroscopy, X-ray diffraction and thin-section microscopy. Sherds from the pyramid Tello are included in the study as representative of local material. The analyses show that the vessels were made from different raw materials and that different firing procedures were used in their production. Sherds of certain styles largely exhibit similar types of Mössbauer patterns and in many instances also have similar element compositions. This supports the archaeological notion that the vessels were brought to Chavín from the provinces, perhaps on the occasion of a festivity. 相似文献