全文获取类型
收费全文 | 42747篇 |
免费 | 5418篇 |
国内免费 | 3691篇 |
专业分类
化学 | 14520篇 |
晶体学 | 144篇 |
力学 | 4366篇 |
综合类 | 404篇 |
数学 | 19429篇 |
物理学 | 12993篇 |
出版年
2024年 | 82篇 |
2023年 | 417篇 |
2022年 | 590篇 |
2021年 | 874篇 |
2020年 | 1384篇 |
2019年 | 1276篇 |
2018年 | 1128篇 |
2017年 | 1128篇 |
2016年 | 1370篇 |
2015年 | 1319篇 |
2014年 | 2025篇 |
2013年 | 3630篇 |
2012年 | 2254篇 |
2011年 | 2828篇 |
2010年 | 2548篇 |
2009年 | 2761篇 |
2008年 | 2940篇 |
2007年 | 2862篇 |
2006年 | 2572篇 |
2005年 | 2411篇 |
2004年 | 2068篇 |
2003年 | 1848篇 |
2002年 | 1713篇 |
2001年 | 1239篇 |
2000年 | 1161篇 |
1999年 | 1080篇 |
1998年 | 976篇 |
1997年 | 839篇 |
1996年 | 681篇 |
1995年 | 594篇 |
1994年 | 491篇 |
1993年 | 359篇 |
1992年 | 333篇 |
1991年 | 321篇 |
1990年 | 272篇 |
1989年 | 167篇 |
1988年 | 172篇 |
1987年 | 140篇 |
1986年 | 138篇 |
1985年 | 128篇 |
1984年 | 124篇 |
1983年 | 56篇 |
1982年 | 119篇 |
1981年 | 89篇 |
1980年 | 72篇 |
1979年 | 69篇 |
1978年 | 45篇 |
1977年 | 38篇 |
1976年 | 36篇 |
1973年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Dr. Jordan Donat Mr. Patrick Dubourdeaux Dr. Martin Clémancey Dr. Julia Rendon Clara Gervasoni Mr. Morgan Barbier Jessica Barilone Dr. Jacques Pécaut Prof. Dr. Serge Gambarelli Prof. Dr. Pascale Maldivi Prof. Dr. Jean-Marc Latour 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(70):e202201875
Nitrene transfer reactions have emerged as one of the most powerful and versatile ways to insert an amine function to various kinds of hydrocarbon substrates. However, the mechanisms of nitrene generation have not been studied in depth albeit their formation is taken for granted in most cases without definitive evidence of their occurrence. In the present work, we compare the generation of tosylimido iron species and NTs transfer from FeII and FeIII precursors where the metal is embedded in a tetracarbene macrocycle. Catalytic nitrene transfer to reference substrates (thioanisole, styrene, ethylbenzene and cyclohexane) revealed that the same active species was at play, irrespective of the ferrous versus ferric nature of the precursor. Through combination of spectroscopic (UV-visible, Mössbauer), ESI-MS and DFT studies, an FeIV tosylimido species was identified as the catalytically active species and was characterized spectroscopically and computationally. Whereas its formation from the FeII precursor was expected by a two-electron oxidative addition, its formation from an FeIII precursor was unprecedented. Thanks to a combination of spectroscopic (UV-visible, EPR, Hyscore and Mössbauer), ESI-MS and DFT studies, we found that, when starting from the FeIII precursor, an FeIII tosyliodinane adduct was formed and decomposed into an FeV tosylimido species which generated the catalytically active FeIV tosylimide through a comproportionation process with the FeIII precursor. 相似文献
2.
This paper is concerned with the Cauchy problem on the Boltzmann equation without angular cutoff assumption for hard potential in the whole space. When the initial data is a small perturbation of a global Maxwellian, the global existence of solution to this problem is proved in unweighted Sobolev spaces with . But if we want to obtain the optimal temporal decay estimates, we need to add the velocity weight function, in this case the global existence and the optimal temporal decay estimate of the Boltzmann equation are all established. Meanwhile, we further gain a more accurate energy estimate, which can guarantee the validity of the assumption in Chen et al. (0000). 相似文献
3.
4.
Tomoyuki Nakatsuka 《Mathematische Nachrichten》2021,294(1):98-117
We study the existence of a time‐periodic solution with pointwise decay properties to the Navier–Stokes equation in the whole space. We show that if the time‐periodic external force is sufficiently small in an appropriate sense, then there exists a time‐periodic solution of the Navier–Stokes equation such that and uniformly in as . Our solution decays faster than the time‐periodic Stokes fundamental solution and the faster decay of its spatial derivatives of higher order is also described. 相似文献
5.
Donglei Wei Huili Li Chuanqing Yang Jianmin Fu Hou Chen Liangjiu Bai Wenxiang Wang Huawei Yang Lixia Yang Ying Liang 《Journal of polymer science. Part A, Polymer chemistry》2022,60(10):1588-1594
Acridone as a new kind of visible light photocatalyst has been developed to catalyze metal free atom transfer radical polymerization (ATRP). The photocatalyst possess low excited state potential as can undergo an oxidative quenching pathway to initiate ATRP of vinyl monomers. Kinetic study and light on/off reaction demonstrate the “living”/controlled nature of the polymerization by light. Block copolymers can be achieved by using PMMA as macroinitiator to reinitiate polymerization of other vinyl monomers, which shows highly preserved Br chain-end functionality in the synthesized polymers. Moreover, the polymerization can be conducted under air atmosphere as most photocatalysts need anaerobic condition, which may give inspiration of further application of this kind of photocatalyst. 相似文献
6.
7.
8.
9.
10.
Florence Drui Emmanuel Franck Philippe Helluy Laurent Navoret 《Comptes Rendus Mecanique》2019,347(3):259-269
The over-relaxation approach is an alternative to the Jin–Xin relaxation method in order to apply the equilibrium source term in a more precise way. This is also a key ingredient of the lattice Boltzmann method for achieving second-order accuracy. In this work, we provide an analysis of the over-relaxation kinetic scheme. We compute its equivalent equation, which is particularly useful for devising stable boundary conditions for the hidden kinetic variables. 相似文献