全文获取类型
收费全文 | 95905篇 |
免费 | 2190篇 |
国内免费 | 425篇 |
专业分类
化学 | 46819篇 |
晶体学 | 1032篇 |
力学 | 4180篇 |
综合类 | 13篇 |
数学 | 11104篇 |
物理学 | 35372篇 |
出版年
2022年 | 615篇 |
2021年 | 760篇 |
2020年 | 910篇 |
2019年 | 776篇 |
2018年 | 1065篇 |
2017年 | 981篇 |
2016年 | 1921篇 |
2015年 | 1410篇 |
2014年 | 1863篇 |
2013年 | 4337篇 |
2012年 | 4028篇 |
2011年 | 4867篇 |
2010年 | 3331篇 |
2009年 | 3205篇 |
2008年 | 4463篇 |
2007年 | 4212篇 |
2006年 | 4012篇 |
2005年 | 3569篇 |
2004年 | 3188篇 |
2003年 | 2702篇 |
2002年 | 2405篇 |
2001年 | 3752篇 |
2000年 | 2736篇 |
1999年 | 1938篇 |
1998年 | 1427篇 |
1997年 | 1393篇 |
1996年 | 1294篇 |
1995年 | 1215篇 |
1994年 | 1165篇 |
1993年 | 1095篇 |
1992年 | 1479篇 |
1991年 | 1297篇 |
1990年 | 1223篇 |
1989年 | 1078篇 |
1988年 | 1043篇 |
1987年 | 1124篇 |
1986年 | 956篇 |
1985年 | 1361篇 |
1984年 | 1290篇 |
1983年 | 948篇 |
1982年 | 975篇 |
1981年 | 948篇 |
1980年 | 907篇 |
1979年 | 1014篇 |
1978年 | 1032篇 |
1977年 | 1047篇 |
1976年 | 937篇 |
1975年 | 835篇 |
1974年 | 862篇 |
1973年 | 735篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
Central European Journal of Operations Research - 相似文献
83.
84.
Zsifkovits Martin Günther Markus 《Central European Journal of Operations Research》2015,23(2):501-522
Central European Journal of Operations Research - Innovation resistances play a major role in innovation diffusion, as they do not only hinder the adoption, but might also change a decision... 相似文献
85.
Altıntas Yemliha Öztürk Esra Aksöz Sezen Keşlioğlu Kâzım Maraşlı Necmettin 《Journal of Thermal Analysis and Calorimetry》2015,122(1):65-72
Journal of Thermal Analysis and Calorimetry - The equilibrated grain boundary groove shapes for solid Bi (Bi–2.87 at.%Ag) in equilibrium with Bi–Ag eutectic liquid have been... 相似文献
86.
Thomas Wittmann Dr. Renée Siegel Nele Reimer Dr. Wolfgang Milius Prof. Dr. Norbert Stock Prof. Dr. Jürgen Senker 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(1):314-323
The resistance of metal–organic frameworks towards water is a very critical issue concerning their practical use. Recently, it was shown for microporous MOFs that the water stability could be increased by introducing hydrophobic pendant groups. Here, we demonstrate a remarkable stabilisation of the mesoporous MOF Al‐MIL‐101‐NH2 by postsynthetic modification with phenyl isocyanate. In this process 86 % of the amino groups were converted into phenylurea units. As a consequence, the long‐term stability of Al‐MIL‐101‐URPh in liquid water could be extended beyond a week. In water saturated atmospheres Al‐MIL‐101‐URPh decomposed at least 12‐times slower than the unfunctionalised analogue. To study the underlying processes both materials were characterised by Ar, N2 and H2O sorption measurements, powder X‐ray diffraction, thermogravimetric and chemical analysis as well as solid‐state NMR and IR spectroscopy. Postsynthetic modification decreased the BET equivalent surface area from 3363 to 1555 m2 g?1 for Al‐MIL‐101‐URPh and reduced the mean diameters of the mesopores by 0.6 nm without degrading the structure significantly and reducing thermal stability. In spite of similar water uptake capacities, the relative humidity‐dependent uptake of Al‐MIL‐101‐URPh is slowed and occurs at higher relative humidity values. In combination with 1H‐27Al D ‐HMQC NMR spectroscopy experiments this favours a shielding mechanism of the Al clusters by the pendant phenyl groups and rules out pore blocking. 相似文献
87.
88.
89.
Hanfi Mohamed Y. Yarmoshenko Ilia V. Seleznev Andrian A. Zhukovsky Michael V. 《Journal of Radioanalytical and Nuclear Chemistry》2019,320(3):831-839
Journal of Radioanalytical and Nuclear Chemistry - A castable polyurethane (PUR) with soft segment made by polytetrahydrofuran polyol (or polytretramethylene ether glycol?=?PTMEG)... 相似文献
90.
We consider the question whether, given a countable family of lattices in a locally compact abelian group G, there exist functions such that the resulting generalized shift-invariant system is a tight frame of . This paper develops a new approach to the study of generalized shift-invariant system via almost periodic functions, based on a novel unconditional convergence property. From this theory, we derive characterizing relations for tight and dual frame generators, we introduce the system bandwidth as a measure of the total bandwidth a generalized shift-invariant system can carry, and we show that the so-called Calderón sum is uniformly bounded from below for generalized shift-invariant frames. Without the unconditional convergence property, we show, counter intuitively, that even orthonormal bases can have arbitrary small system bandwidth. Our results show that the question of existence of frame generators for a general lattice system is rather subtle and depends on analytical and algebraic properties of the lattice system. 相似文献