全文获取类型
收费全文 | 53474篇 |
免费 | 3692篇 |
国内免费 | 3727篇 |
专业分类
化学 | 21003篇 |
晶体学 | 404篇 |
力学 | 4785篇 |
综合类 | 618篇 |
数学 | 13504篇 |
物理学 | 20579篇 |
出版年
2024年 | 44篇 |
2023年 | 451篇 |
2022年 | 769篇 |
2021年 | 1081篇 |
2020年 | 1176篇 |
2019年 | 1205篇 |
2018年 | 1095篇 |
2017年 | 1269篇 |
2016年 | 1410篇 |
2015年 | 1121篇 |
2014年 | 1784篇 |
2013年 | 3318篇 |
2012年 | 2108篇 |
2011年 | 2329篇 |
2010年 | 1950篇 |
2009年 | 3071篇 |
2008年 | 3387篇 |
2007年 | 3765篇 |
2006年 | 3192篇 |
2005年 | 2561篇 |
2004年 | 2122篇 |
2003年 | 2419篇 |
2002年 | 2898篇 |
2001年 | 2144篇 |
2000年 | 2018篇 |
1999年 | 1726篇 |
1998年 | 1704篇 |
1997年 | 982篇 |
1996年 | 897篇 |
1995年 | 848篇 |
1994年 | 847篇 |
1993年 | 647篇 |
1992年 | 707篇 |
1991年 | 493篇 |
1990年 | 448篇 |
1989年 | 333篇 |
1988年 | 294篇 |
1987年 | 297篇 |
1986年 | 261篇 |
1985年 | 240篇 |
1984年 | 238篇 |
1983年 | 149篇 |
1982年 | 209篇 |
1981年 | 202篇 |
1980年 | 124篇 |
1979年 | 156篇 |
1978年 | 115篇 |
1977年 | 92篇 |
1976年 | 48篇 |
1973年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
M. Georgelin A. Pocheau 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(2):169-174
The polycrystalline perovskitelike manganese oxides La1-xAxMnO (A = Na, and K, ) have been fabricated by sol-gel technique. For all the compositions explored in this work, the average manganese oxidation
state is practically constant, at for A = Na, and for A = K, respectively. A close relationship is confirmed to hold between the Curie temperature (Tc) and the bond distance of Mn-O. Results of magnetic measurements show that these materials can be utilized as suitable candidates
for magnetic refrigerants with wide applied temperature span, for their significant entropy change and the easily tuned Curie
temperature.
Received: 12 September 1997 / Revised: 18 December 1997 / Accepted: 21 January 1998 相似文献
42.
I. L. Eremenko M. A. Golubnichaya S. E. Nefedov A. A. Sidorov D. A. Nesterenko N. P. Konovalova L. M. Volkova L. T. Eremenko 《Russian Chemical Bulletin》1997,46(9):1595-1598
Thetrans-[Pt(NC5H4C(O)NHC2H4ONO2)2Cl2] complex (2) was prepared by the reaction of nicorandyl (N-nitroethoxynicotinamide), which is widely used in cardiology, with K2PtCl4 in water. The structure of2 was established by X-ray structural analysis. It was found that complex2 exhibits high antitumor activity, in particular, antimetastatic activity, unlike the analogous CuII complex with bromine atoms.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1672–1675, September, 1997. 相似文献
43.
XU Jun YAN Ai-Zhen XU Qin-Hua Department of Chemistry Nanjing University Nanjing Jiangsu China 《中国化学》1995,(2)
The strength of basic sites has been measured by pyrrole-IR on alkali metal cation exchanged β and X zeolites, as well as NaOH loaded Naβ. The influence of cation type and the structure of zeolites on their basicity has been studied. The acidic and basic properties of the samples were investigated by NH3-TPD and isopropanol reaction. It was shown that the strength of basic sites on samples could be characterized by the shift of vNH band in the pyrrole-IR spectra. The framework oxygen charges were calculated from the Sanderson electronegativity. The changes in basic properties with various alkali metal cation are consistent with the changes of local oxygen charges of the zeolite framework. 相似文献
44.
45.
46.
通过建立具有平面近横向各向异性场的非晶态合金薄带及膜的磁畴结构模型,利用线性化Maxwell方程组及Landau-Lifshitz方程,推出了在高频交变磁场及外加面内轴向直流磁场Hex作用下的铁磁材料的与取向相关的磁导率表达式,得到了对方位角平均的相对磁导率及阻抗的计算式,导出了磁导率与张量磁化率分量间的关系,对材料磁导率的实部及虚部随Hex的变化进行了计算,并给出了对应的磁谱图.建立的磁导率与外磁场的理论关系可将Panina及Kraus给出的理论结果统一起来.
关键词:
非晶态合金薄带及膜
取向相关磁导率
GMI效应理论与计算
近横向各向异性场 相似文献
47.
High index of refraction via quantum interference in a three-level system of Er^3+-doped yttrium aluminium garnet crystal 下载免费PDF全文
A simple three-level system is proposed to produce high index of refraction with zero absorption in an Er^3+-doped yttrium aluminium garnet (YAG) crystal, which is achieved for a probe field between the excited state 4I13/2 and ground state 4I15/2 by adjusting a strong coherent driving field between the upper excited state 4I11/2 and 4I15/2. It is found that the changes of the frequency of the coherent driving field and the concentration of Er^3+ ions in the YAG crystal can maximize the index of refraction accompanied by vanishing absorption. This result could be useful for the dispersion compensation in fibre communication, laser particle acceleration, high precision magnetometry and so on. 相似文献
48.
49.
S. Sabchevski T. Idehara I. Ogawa M. Glyavin K. Ohashi 《International Journal of Infrared and Millimeter Waves》2002,23(5):675-692
A computer code for simulation of beam-field interaction in a resonant cavity of a gyrotron has been developed. It is based on a self-consistent, time-independent, single-mode physical model. The code has been applied to the analysis of the electrodynamical system of a novel high-harmonic gyrotron with axis-encircling beam and a permanent magnet. In this paper both the physical model and numerical techniques used are outlined. Some results of the numerical experiments are presented and discussed. 相似文献
50.
使用SAC/SAC-CI方法,利用D95(d),6-311g**以及cc-PVTZ等基组,对B2分子的基态(X3Σg-)和第一激发态(A3Σu-)的平衡结构和谐振频率进行了优化计算.通过对3个基组的计算结果的比较,得出了D95(d)基组为3个基组中的最优基组的结论;使用D95(d)基组,利用SAC的GSUM(Group Sum of Operators)方法对基态(X3Σg-),SAC-CI的GSUM方法对激发态(A3Σu-)进行单点能扫描计算,用正规方程组拟合Murrell-Sorbie函数,得到了相应电子态的完整势能函数;从得到的势能函数计算了与基态(X3Σg-)和第一激发态(A3Σu-)相对应的光谱常数(Be,αe,ωe和ωeχe),结果与实验数据吻合. 相似文献