全文获取类型
收费全文 | 65760篇 |
免费 | 13659篇 |
国内免费 | 4676篇 |
专业分类
化学 | 61461篇 |
晶体学 | 659篇 |
力学 | 2523篇 |
综合类 | 319篇 |
数学 | 5672篇 |
物理学 | 13461篇 |
出版年
2024年 | 84篇 |
2023年 | 621篇 |
2022年 | 778篇 |
2021年 | 1146篇 |
2020年 | 2324篇 |
2019年 | 3606篇 |
2018年 | 1938篇 |
2017年 | 1504篇 |
2016年 | 4595篇 |
2015年 | 4685篇 |
2014年 | 4900篇 |
2013年 | 6094篇 |
2012年 | 5618篇 |
2011年 | 4934篇 |
2010年 | 4577篇 |
2009年 | 4504篇 |
2008年 | 4175篇 |
2007年 | 3464篇 |
2006年 | 2990篇 |
2005年 | 2916篇 |
2004年 | 2409篇 |
2003年 | 2186篇 |
2002年 | 2865篇 |
2001年 | 2036篇 |
2000年 | 1882篇 |
1999年 | 1093篇 |
1998年 | 680篇 |
1997年 | 651篇 |
1996年 | 721篇 |
1995年 | 567篇 |
1994年 | 514篇 |
1993年 | 425篇 |
1992年 | 425篇 |
1991年 | 365篇 |
1990年 | 287篇 |
1989年 | 231篇 |
1988年 | 190篇 |
1987年 | 152篇 |
1986年 | 143篇 |
1985年 | 136篇 |
1984年 | 102篇 |
1983年 | 67篇 |
1982年 | 49篇 |
1981年 | 40篇 |
1980年 | 44篇 |
1978年 | 42篇 |
1977年 | 71篇 |
1976年 | 38篇 |
1975年 | 46篇 |
1974年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 44 毫秒
111.
112.
Yun-Zhi Tang Shao-Song Qian Xi-Sen Wang Hong Zhao Xue-Feng Huang Yong-Hua Li Xing-Cai Jiao Ren-Gen Xiong Prof. Dr. 《无机化学与普通化学杂志》2004,630(11):1623-1626
The in situ hydrolysis of phthalyl-γ-glutaminyl-histidine with Cd(ClO4)2·6H2O in the presence of water and methanol affords a novel two-dimensional cadmium coordination polymer, a new phase, anhydrous cadmium(II) phthalate, ( 1 ). The structure was determined by single crystal X-ray diffraction. Crystal data: P21/c, a = 13.8168(14), b = 7.0351(7), c = 8.2054(8) Å, β = 105.540(2)°, V = 768.43(13) Å3, Z = 4, R1 = 0.0380, wR2 = 0.1111. 相似文献
113.
114.
115.
A graph G is N2‐locally connected if for every vertex ν in G, the edges not incident with ν but having at least one end adjacent to ν in G induce a connected graph. In 1990, Ryjá?ek conjectured that every 3‐connected N2‐locally connected claw‐free graph is Hamiltonian. This conjecture is proved in this note. © 2004 Wiley Periodicals, Inc. J Graph Theory 48: 142–146, 2005 相似文献
116.
In the present paper, some new almost fixed point theorems and fixed point theorems for lower semicontinuous type multivalued mappings are obtained in metrizable H-spaces. 相似文献
117.
Ching‐Yuan Cheng Kuan‐Jiuh Lin 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(8):m363-m365
In the title compound, catena‐poly[lithium‐μ3‐ethylenediphosphonato], [Li(C2H7O6P2)]n, the supramolecular monoclinic (C2/c) structure consists of one‐dimensional lithium chains [Li⋯Li = 2.7036 (8) Å] that are embedded within ethylenediphosphonate anions linked by strong symmetric hydrogen bonds [O⋯O = 2.473 (3) Å]. The Li atoms and the H atom in the symmetric hydrogen bond reside on twofold rotation axes and there is an inversion center at the mid‐point of the C—C bond of the ethylenediphosphonate ligand. 相似文献
118.
The inhomogeneous Dirichlet problems concerning divergence form elliptic equations are studied. Optimal regularity requirements on the coefficients and domains for the W1,p theory, 1 < p < ∞, are obtained. The principal coefficients are supposed to be in the John‐Nirenberg space with small BMO seminorms. The domain is a Reifenberg domain. These conditions for the W1,p theory not only weaken the requirements on the coefficients but also lead to a more general geometric condition on the domains. In fact, these domains might have fractal dimensions. © 2004 Wiley Periodicals, Inc. 相似文献
119.
勿庸置疑,课堂只是学生腾飞的基地,社会才是学生飞翔的天空.如何架设课堂与社会之间的桥梁,使学生从理论走向实践,从空想走向实际,是每位教师必须思考的问题.就物理教学而言,实验是架设课堂和社会的桥梁之一.那就是通过物理实验来实现. 相似文献
120.
Marcelino Maneiro Manuel R. Bermejo M. Isabel Fernndez Ana M. Gonzlez‐Noya Alexei M. Tyryshkin Robin G. Pritchard 《无机化学与普通化学杂志》2003,629(2):285-290
A new MnIII‐Schiff base complex, [MnL(OH2)](ClO4) ( 1 ) (H2L = N, N′‐bis‐(3‐Br‐5‐Cl‐salicylidene)‐1, 2‐diimino‐2‐methylethane), an inorganic model of the catalytic center (OEC, Oxygen Evolving Complex) in photosystem II (PSII), has been synthesized and characterized by elemental analysis, IR and EPR spectroscopy, mass spectrometry, magnetic susceptibility measurement and the study of its redox properties by cyclic and normal pulse voltammetry. This complex mimics reactivity (showing a relevant photolytic activity), and also some structural characteristics (parallel‐mode MnIII EPR signal from partially assembled OEC cluster) of the natural OEC. The complex 1 was found to rearrange in solution into a crystallographically solved square‐pyramidal complex, [MnLL′] ( 2 ) (HL′ = 6‐bromo‐4‐chloro‐2‐cyanophenol), through a process, which probably liberates radical species (detected by EPR), and provokes a C—N bond cleavage in the ligand. A photo‐radical mechanism is discussed to explain this rearrangement. 相似文献