全文获取类型
收费全文 | 207417篇 |
免费 | 2387篇 |
国内免费 | 898篇 |
专业分类
化学 | 104652篇 |
晶体学 | 3366篇 |
力学 | 9477篇 |
综合类 | 25篇 |
数学 | 22947篇 |
物理学 | 70235篇 |
出版年
2021年 | 1744篇 |
2020年 | 1924篇 |
2019年 | 2094篇 |
2018年 | 2798篇 |
2017年 | 2692篇 |
2016年 | 3890篇 |
2015年 | 2436篇 |
2014年 | 3772篇 |
2013年 | 9310篇 |
2012年 | 7547篇 |
2011年 | 9010篇 |
2010年 | 6245篇 |
2009年 | 6091篇 |
2008年 | 8155篇 |
2007年 | 8283篇 |
2006年 | 7900篇 |
2005年 | 7044篇 |
2004年 | 6549篇 |
2003年 | 5755篇 |
2002年 | 5586篇 |
2001年 | 6499篇 |
2000年 | 5022篇 |
1999年 | 3858篇 |
1998年 | 3101篇 |
1997年 | 3097篇 |
1996年 | 2862篇 |
1995年 | 2668篇 |
1994年 | 2520篇 |
1993年 | 2389篇 |
1992年 | 2742篇 |
1991年 | 2704篇 |
1990年 | 2626篇 |
1989年 | 2436篇 |
1988年 | 2484篇 |
1987年 | 2477篇 |
1986年 | 2319篇 |
1985年 | 2988篇 |
1984年 | 3244篇 |
1983年 | 2655篇 |
1982年 | 2816篇 |
1981年 | 2785篇 |
1980年 | 2656篇 |
1979年 | 2737篇 |
1978年 | 2832篇 |
1977年 | 2830篇 |
1976年 | 2901篇 |
1975年 | 2686篇 |
1974年 | 2647篇 |
1973年 | 2784篇 |
1972年 | 1767篇 |
排序方式: 共有10000条查询结果,搜索用时 271 毫秒
61.
Ding Q. Yao M. Wu Sh. Zeng M. Xue N. Wu D. Xu J. 《Journal of Applied Spectroscopy》2022,89(4):712-718
Journal of Applied Spectroscopy - Based on partial least squares (PLS) analysis, the effects of different smoothing points and different preprocessing methods on the accuracy and precision of the... 相似文献
62.
Crystallography Reports - Nd1 – yEuyF3 – y crystals (y is the molar fraction of EuF2; 0 ≤ y ≤ 0.15) with a tysonite (LaF3) structure have... 相似文献
63.
Stolpovskaya N. V. Kruzhilin A. A. Zorina A. V. Shikhaliev Kh. S. Ledeneva I. V. Kosheleva E. A. Vandyshev D. Yu. 《Russian Journal of Organic Chemistry》2019,55(9):1322-1328
Russian Journal of Organic Chemistry - A procedure has been proposed for the synthesis of a series of substituted N-(1,3-thiazol-2-yl)-pyrimidin-2-amines and N-(pyrimidin-2-yl)thioureas by... 相似文献
64.
65.
66.
Francesco Segatta David M. Rogers Naomi T. Dyer Ellen E. Guest Zhuo Li Hainam Do Artur Nenov Marco Garavelli Jonathan D. Hirst 《Molecules (Basel, Switzerland)》2021,26(2)
A fully quantitative theory of the relationship between protein conformation and optical spectroscopy would facilitate deeper insights into biophysical and simulation studies of protein dynamics and folding. In contrast to intense bands in the far-ultraviolet, near-UV bands are much weaker and have been challenging to compute theoretically. We report some advances in the accuracy of calculations in the near-UV, which were realised through the consideration of the vibrational structure of the electronic transitions of aromatic side chains. 相似文献
67.
Corina Andronescu Justus Masa Richard D. Tilley John J. Gooding Wolfgang Schuhmann 《Current Opinion in Electrochemistry》2021
The complex interplay of restricted mass transport leading to local accumulation or depletion of educts, intermediates, products, counterions and co-ions influences the reactions at the active sites of electrocatalysts when electrodes are rough, three-dimensionally mesoporous or nanoporous. This influence is important with regard to activity, and even more to selectivity, of electrocatalytic reactions. The underlying principles are discussed based on the growing awareness of these considerations over recent years. 相似文献
68.
Two new divalent copper (C1) and zinc (C2) chelates having the formulae [M(PIMC)2] (where M = Cu(II), Zn(II) and PIMC = Ligand [(E)-3-(((3-hydroxypyridin-2-yl)imino)methyl)-4H-chromen-4-one] were obtained and characterized by several techniques. Structures and geometries of the synthesized complexes were judged based on the results of alternative analytical and spectral tools supporting the proposed formulae. IR spectral data confirmed the coordination of the ligands to the copper and zinc centers as monobasic tridentate in the enol form. Thermal analysis, UV-Vis spectra and magnetic moment confirmed the geometry around the copper center to be tetrahedral, square pyramidal and octahedral. Study of the binding ability of the synthesized compounds with Circulating tumor DNA (CT-DNA) bas been evaluated applying UV-Vis spectral titration and viscosity measurements. The copper and zinc oxides were achieved from the copper and zinc nano-particles structures Schiff base complexes as the raw material after calcination for 5 hr at 600°C. On the other hand, synthesized of C1 and C2 NPs were used as suitable precursors to the preparation of CuO and ZnO NPs. Finally, the synthesized of the two complexes exhibited enhanced activity against the tested bacterial (Staphylococcus aureus and Escherichia Coli) and fungal strains (Candida albicans and Aspergillus fumigatus) as compared to HPIMC. Among all these synthesized compounds, C1 exhibits good cleaving ability compared to other newly synthesized C2. 相似文献
69.
Chao Liu Liying Wang Lin Yang Famei Wang Chunhong Xu Jingwei Lv Guanglai Fu Xianli Li Qiang Liu Haiwei Mu Tao Sun Paul K. Chu 《Physics letters. A》2019,383(25):3200-3206
A single-polarization filter comprising a gold-coated photonic crystal fiber based on surface plasmon resonance is designed and investigated. The pattern matching and coupled polarization characteristics analyzed by the full-vector finite element method (FEM) and losses at 1,540 nm are achieved to 1,016.01739 dB/cm (x-pol core mode) and 33.81917 dB/cm (y-pol core mode). The crosstalk (CT) value of the 1,540 nm band is ?853.12653 dB for fiber length and the bandwidth is 850 nm. The working wavelength of the filter ranges from 1,280 nm to 1,540 nm by varying the diameter of outer air holes (), the diameter of inner air holes (), the metal film thickness (t), as well as the liquid refractive index (n). 相似文献
70.
Martín D. Safe 《Journal of Graph Theory》2020,93(2):268-298
A graph is concave-round if its vertices can be circularly enumerated so that the closed neighborhood of each vertex is an interval in the enumeration. In this study, we give a minimal forbidden induced subgraph characterization for the class of concave-round graphs, solving a problem posed by Bang-Jensen, Huang, and Yeo [SIAM J. Discrete Math., 13 (2000), pp. 179–193]. In addition, we show that it is possible to find one such forbidden induced subgraph in linear time in any given graph that is not concave-round. As part of the analysis, we obtain characterizations by minimal forbidden submatrices for the circular-ones property for rows and for the circular-ones property for rows and columns and show that, also for both variants of the property, one of the corresponding forbidden submatrices can be found (if present) in any given matrix in linear time. We make some final remarks regarding connections to some classes of circular-arc graphs. 相似文献