全文获取类型
收费全文 | 14199篇 |
免费 | 1407篇 |
国内免费 | 1282篇 |
专业分类
化学 | 3030篇 |
晶体学 | 94篇 |
力学 | 1130篇 |
综合类 | 427篇 |
数学 | 7349篇 |
物理学 | 4858篇 |
出版年
2024年 | 29篇 |
2023年 | 116篇 |
2022年 | 227篇 |
2021年 | 298篇 |
2020年 | 329篇 |
2019年 | 317篇 |
2018年 | 299篇 |
2017年 | 340篇 |
2016年 | 392篇 |
2015年 | 295篇 |
2014年 | 548篇 |
2013年 | 873篇 |
2012年 | 644篇 |
2011年 | 843篇 |
2010年 | 863篇 |
2009年 | 1014篇 |
2008年 | 978篇 |
2007年 | 1006篇 |
2006年 | 955篇 |
2005年 | 729篇 |
2004年 | 642篇 |
2003年 | 642篇 |
2002年 | 568篇 |
2001年 | 521篇 |
2000年 | 446篇 |
1999年 | 409篇 |
1998年 | 351篇 |
1997年 | 309篇 |
1996年 | 254篇 |
1995年 | 212篇 |
1994年 | 188篇 |
1993年 | 143篇 |
1992年 | 153篇 |
1991年 | 101篇 |
1990年 | 95篇 |
1989年 | 88篇 |
1988年 | 79篇 |
1987年 | 70篇 |
1986年 | 34篇 |
1985年 | 64篇 |
1984年 | 53篇 |
1983年 | 32篇 |
1982年 | 65篇 |
1981年 | 43篇 |
1980年 | 34篇 |
1979年 | 58篇 |
1978年 | 36篇 |
1977年 | 29篇 |
1974年 | 21篇 |
1973年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
121.
In this paper we shall introduce two q-analogues of the squeezed states in terms of the technique of integration within an ordered product of operators and the
properties of the inverses of q-deformed annihilation and creation operators, and some nonclassical properties of the states are examined. Furthermore, we
obtain some new completeness relations composed of the bra and ket which are not mutually Hermitian conjugate.
PACS numbers: 03.65.-w; 45.50.Ct.
Work supported by the National Natural Science Foundation of China under Grant 10574060 and the Natural Science Foundation
of Shandong Province of China under Grant Y2004A09. 相似文献
122.
123.
Z.Q. Li D.X. Zhang X.H. Zhang Y.Q. Gao X.J. Liu E.Y. Jiang 《Physics letters. A》2007,370(5-6):512-516
The charge ordering characteristics in Y0.5Ca0.5MnO3 manganite, prepared by sol–gel process, have been investigated experimentally. It is found that the superlattice diffractions appear in the electron diffraction patterns recorded at low temperatures, while only basic Brag diffraction spots can be observed when temperature is higher than 300 K. This provides direct evidence for the existence of charge ordering in Y0.5Ca0.5MnO3. The magnetization and specific heat measurements indicate the charge ordering temperature of Y0.5Ca0.5MnO3 is 290 K, around which both the magnetization and specific heat reveal anomalous behaviors. We also observed that the MnO bond length changed remarkably and the effective number of carriers reduced prominently with decreasing temperature around charge ordering temperature through transform infrared spectra measurements. 相似文献
124.
The study uses the Fourier transform infrared spectroscopy method to evaluate the influence of phosphogypsum from the soil on the growth and accumulation of nutrients in Spinacia oleracea. Attenuated total reflectance spectra of Spinacia oleracea roots and stems originated from plants cultivated on 28% to 52% phosphogypsum enriched soil have been studied in the 4000–600 cm?1 area. The structure of the infrared absorption bands for spinach roots and stems and for the soil where plants were grown was analyzed. Thus, it was observed that phosphorus–oxygen bonds contribution can be identified both in roots and stems absorption spectra. The significance of the research is the possibility to use the infrared investigation as rapid technique, particularly useful for agriculture, to study the extraction and assimilation process of the compounds containing phosphorus and nitrogen from the soil in which the spinach seedlings grew. In the case of this study, it was observed that the absorption of phosphorus in the spinach roots and stems has not the same effect. The analysis of obtained data indicated that the assimilation of phosphorus from phosphogypsum enriched soil induces changes in spinach roots structure that are most likely due to an increase synthesis of proteins, rather than to a decrease in carbohydrates quantity. 相似文献
125.
126.
127.
讨论了两列光波发生干涉现象的理想化条件和在实验中能否观察到干涉现象发生的操作性条件,推导了各种情况下的理论公式。从工程应用的角度出发,研究了检测仪器的响应时间T和光强分辨能力对观察光的干涉现象的影响,提出了观察光的干涉现象的第四个必要条件,对在各种情况下应用光的干涉现象有一定的指导作用。 相似文献
128.
目前,针对空间电磁场作用有耗介质层上传输线的电磁耦合,仍缺乏有效的数值分析方法.因此,本文提出一种高效的时域混合算法,很好地解决了有耗介质层上传输线电磁耦合建模难的问题.首先,对经典传输线方程进行改进,推导了适用于有耗介质层上多导体传输线电磁耦合分析的修正传输线方程.然后,结合时域有限差分方法和相应插值技术,求解修正传输线方程,获得多导线及其端接负载上的电压和电流响应,并实现空间电磁场辐射与多导线瞬态响应的同步计算.最后,通过相应计算实例的数值模拟,与CST软件的仿真结果进行对比,验证了时域混合算法的正确性和高效性. 相似文献
129.
A.H.Tang 《中国物理C(英文版)》2020,44(5):054101-054101-13
In this paper a pair of observables are proposed as alternative ways,by examining the fluctuation of net momentum-ordering of charged pairs,to study the charge separation induced by the Chiral Magnetic Effect(CME)in relativistic heavy ion collisions.They are,the out-of-plane to in-plane ratio of fluctuation of the difference between signed balance functions measured in pair’s rest frame,and the ratio of it to similar measurement made in the laboratory frame.Both observables have been studied with simulations including flow-related backgrounds,and for the first time,backgrounds that are related to resonance's global spin alignment.The two observables have similar positive responses to signal,and opposite,limited responses to identifiable backgrounds arising from resonance flow and spin alignment.Both observables have also been tested with two realistic models,namely,a multi-phase transport(AMPT)model and the anomalous-viscous fluid dynamics(AVFD)model.These two observables,when cross examined,will provide useful insights in the study of CME-induced charge separation. 相似文献
130.
G. A. Miller 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):578-584
The discovery more than twenty years ago, by the EMC Collaboration, that the deep-inelastic-scattering DIS structure functions
are influenced by the nuclear environment stunned the nuclear physics community and brought quarks and gluons into the field
with great impact. A great length of time has passed, but despite a semi-infinite number of papers on the subject, there is
no explanation that is universally accepted. Many models (related in one way or another to QCD) have been successful in reproducing
data for deep inelastic scattering on nuclear targets, but fewer have described both the DIS and nuclear Drell-Yan experiments.
Although there are some positive indications, no model has been used to predict correctly and unambiguously new independent
phenomena. We review the history and discuss the best experimental prospects for future discovery. 相似文献