全文获取类型
收费全文 | 30145篇 |
免费 | 182篇 |
国内免费 | 312篇 |
专业分类
化学 | 11506篇 |
晶体学 | 268篇 |
力学 | 1455篇 |
综合类 | 12篇 |
数学 | 9091篇 |
物理学 | 8307篇 |
出版年
2022年 | 32篇 |
2021年 | 82篇 |
2020年 | 116篇 |
2019年 | 100篇 |
2018年 | 1296篇 |
2017年 | 1530篇 |
2016年 | 835篇 |
2015年 | 632篇 |
2014年 | 590篇 |
2013年 | 851篇 |
2012年 | 3230篇 |
2011年 | 2404篇 |
2010年 | 1899篇 |
2009年 | 1622篇 |
2008年 | 628篇 |
2007年 | 637篇 |
2006年 | 604篇 |
2005年 | 4429篇 |
2004年 | 3908篇 |
2003年 | 2300篇 |
2002年 | 482篇 |
2001年 | 286篇 |
2000年 | 91篇 |
1999年 | 170篇 |
1998年 | 107篇 |
1997年 | 69篇 |
1996年 | 42篇 |
1995年 | 42篇 |
1994年 | 43篇 |
1992年 | 169篇 |
1991年 | 152篇 |
1990年 | 135篇 |
1989年 | 107篇 |
1988年 | 98篇 |
1987年 | 57篇 |
1986年 | 41篇 |
1985年 | 38篇 |
1984年 | 29篇 |
1983年 | 27篇 |
1979年 | 31篇 |
1976年 | 79篇 |
1975年 | 37篇 |
1974年 | 40篇 |
1973年 | 48篇 |
1972年 | 39篇 |
1970年 | 34篇 |
1969年 | 37篇 |
1968年 | 35篇 |
1967年 | 30篇 |
1966年 | 37篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
1.
Clemens G. Raab Georg Regensburger Jamal Hossein Poor 《Journal of Pure and Applied Algebra》2021,225(5):106564
A formal computation proving a new operator identity from known ones is, in principle, restricted by domains and codomains of linear operators involved, since not any two operators can be added or composed. Algebraically, identities can be modelled by noncommutative polynomials and such a formal computation proves that the polynomial corresponding to the new identity lies in the ideal generated by the polynomials corresponding to the known identities. In order to prove an operator identity, however, just proving membership of the polynomial in the ideal is not enough, since the ring of noncommutative polynomials ignores domains and codomains. We show that it suffices to additionally verify compatibility of this polynomial and of the generators of the ideal with the labelled quiver that encodes which polynomials can be realized as linear operators. Then, for every consistent representation of such a quiver in a linear category, there exists a computation in the category that proves the corresponding instance of the identity. Moreover, by assigning the same label to several edges of the quiver, the algebraic framework developed allows to model different versions of an operator by the same indeterminate in the noncommutative polynomials. 相似文献
2.
3.
4.
5.
Behnam Reza Roghani-Mamaqani Hossein Salami-Kalajahi Mehdi 《Journal of Thermal Analysis and Calorimetry》2019,135(6):3311-3319
Journal of Thermal Analysis and Calorimetry - Effect of different chain extenders, silica nanoparticle loading, and using sol–gel method on the thermal properties of polyurethane (PU) hybrid... 相似文献
6.
Zheng Yuanzhou Yang Haoran Mazaheri Hossein Aghaei Alireza Mokhtari Namjoo Afrand Masoud 《Journal of Thermal Analysis and Calorimetry》2021,143(2):1425-1438
Journal of Thermal Analysis and Calorimetry - The purpose of this study is to numerically investigate flow field and turbulent heat transfer of hybrid nanofluid, water–DWCNT–TiO2 in a... 相似文献
7.
8.
Julia K Pruns Jens-Peter Vietzke Manfred Strassner Claudius Rapp Ulrich Hintze Wilfried A K?nig 《Rapid communications in mass spectrometry : RCM》2002,16(3):208-211
A new solvent-free sample preparation method using silver trifluoroacetate (AgTFA) was developed for the analysis of low molecular weight paraffins and microcrystalline waxes by laser desorption/ionization time-of-flight mass spectrometry (LDI-TOFMS). Experiments show that spectral quality can be enhanced by dispersing AgTFA directly in liquid paraffins without the use of additional solvents. This preparation mixture is applied directly to the MALDI probe. Solid waxes could be examined by melting prior to analysis. The method also provides sufficiently reproducible spectra that peak area ratios between mono- and bicyclic alkane peaks indicated variations in the cycloalkane content of paraffin samples. Dehydrogenation of hydrocarbons observed during the desorption/ionization process was studied by analysis of alkane standards. 相似文献
9.
The versatile behavior of a trihydrazidophosphoradamantane allowing the synthesis of a variety of neutral, mono- or di-cationic water-soluble molecules of potential interest for biphasic catalysis is reported. 相似文献
10.
In this paper we construct an example of a word metric on an infinite cyclic subgroup. This example shows that subexponential
distortion does not obstruct non-trivial growth of connected radii. This answers a question of Gromov [6]. The constructed
metric has other pathological properies. Specifically, its asymptotic cone depends on the choice of ultrafilter and scaling
sequence.
The work has been partially supported by the Swiss National Science Foundation. 相似文献