全文获取类型
收费全文 | 317901篇 |
免费 | 3841篇 |
国内免费 | 1006篇 |
专业分类
化学 | 167211篇 |
晶体学 | 5061篇 |
力学 | 13763篇 |
综合类 | 10篇 |
数学 | 35156篇 |
物理学 | 101547篇 |
出版年
2020年 | 2515篇 |
2019年 | 2638篇 |
2018年 | 3367篇 |
2017年 | 3221篇 |
2016年 | 5177篇 |
2015年 | 3453篇 |
2014年 | 5024篇 |
2013年 | 13690篇 |
2012年 | 10534篇 |
2011年 | 12954篇 |
2010年 | 8538篇 |
2009年 | 8239篇 |
2008年 | 11674篇 |
2007年 | 11785篇 |
2006年 | 11458篇 |
2005年 | 10446篇 |
2004年 | 9500篇 |
2003年 | 8487篇 |
2002年 | 8265篇 |
2001年 | 9298篇 |
2000年 | 7203篇 |
1999年 | 5682篇 |
1998年 | 4666篇 |
1997年 | 4663篇 |
1996年 | 4419篇 |
1995年 | 4215篇 |
1994年 | 3855篇 |
1993年 | 3786篇 |
1992年 | 4264篇 |
1991年 | 4150篇 |
1990年 | 4060篇 |
1989年 | 3852篇 |
1988年 | 3906篇 |
1987年 | 3912篇 |
1986年 | 3665篇 |
1985年 | 4869篇 |
1984年 | 5188篇 |
1983年 | 4330篇 |
1982年 | 4714篇 |
1981年 | 4538篇 |
1980年 | 4437篇 |
1979年 | 4534篇 |
1978年 | 4725篇 |
1977年 | 4656篇 |
1976年 | 4737篇 |
1975年 | 4443篇 |
1974年 | 4304篇 |
1973年 | 4586篇 |
1972年 | 2886篇 |
1967年 | 2240篇 |
排序方式: 共有10000条查询结果,搜索用时 484 毫秒
71.
Mathematical Notes - We study the multiplicity of weak solutions to the boundary-value problem $$\begin{alignedat}{2} - M\biggl(\iint_{\mathbb R^{2N}}|u(x)-u(y)|^2 K(x-y)\,d x\,d y\biggr)\mathscr... 相似文献
72.
Gary W. Breton Lauren A. Hahn Kenneth L. Martin 《Acta Crystallographica. Section C, Structural Chemistry》2019,75(9):1208-1212
Tetrahydrotetrazoles are five‐membered‐ring heterocycles containing four contiguous saturated nitrogen atoms. Very few examples of such compounds have been reported in the literature. Our previous attempt at the synthesis of a member of this class of compound suggested that the N—N bonds may be more labile than expected. This finding raised the question as to whether the structures of any of the previously reported tetrahydrotetrazoles had been properly assigned. We have reproduced the synthesis of a reported tetrahydrotetrazole, namely 1,2‐di‐tert‐butyl 3‐phenyl‐1H,2H,3H,10bH‐[1,2,3,4]tetrazolo[5,1‐a]isoquinoline‐1,2‐dicarboxylate, C25H30N4O4, and have now confidently confirmed its structure via X‐ray crystallography. However, while sufficiently stable in the crystal phase, we discovered that it remains very labile in solution (having a half‐life of only 15 min at 20 °C in CDCl3). A tentative reaction pathway for its dissociation based on 1H NMR spectral evidence is provided. 相似文献
73.
Optics and Spectroscopy - A cell with a submicron thickness was used to measure the broadening and shift of the D1 and D2 lines of Rb atoms by neon. The resolution of hypefine components... 相似文献
74.
75.
Periodica Mathematica Hungarica - We present a tight parametrical Hermite–Hadamard type inequality with probability measure, which yields a considerably closer upper bound for the mean value... 相似文献
76.
Mathematical Notes - It is proved that the lattice of all Fitting classes of finite groups is not distributive, and conditions under which Fitting classes satisfy the distributive and modular laws... 相似文献
77.
Kuzmenkova P. S. Gromushkin D. M. Shulzhenko I. A. Tretyakova T. D. 《Physics of Atomic Nuclei》2021,84(9):1588-1592
Physics of Atomic Nuclei - The paper presents a comparison of three neutrons identifying methods in scintillators based on ZnS with 6Li and 10B: charge integration method, pulse gradient analysis,... 相似文献
78.
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
79.
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
80.
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