全文获取类型
收费全文 | 13875篇 |
免费 | 1296篇 |
国内免费 | 2159篇 |
专业分类
化学 | 5841篇 |
晶体学 | 39篇 |
力学 | 790篇 |
综合类 | 178篇 |
数学 | 8614篇 |
物理学 | 1868篇 |
出版年
2024年 | 39篇 |
2023年 | 220篇 |
2022年 | 346篇 |
2021年 | 451篇 |
2020年 | 691篇 |
2019年 | 509篇 |
2018年 | 446篇 |
2017年 | 464篇 |
2016年 | 545篇 |
2015年 | 455篇 |
2014年 | 755篇 |
2013年 | 1175篇 |
2012年 | 639篇 |
2011年 | 764篇 |
2010年 | 650篇 |
2009年 | 791篇 |
2008年 | 897篇 |
2007年 | 899篇 |
2006年 | 794篇 |
2005年 | 749篇 |
2004年 | 605篇 |
2003年 | 681篇 |
2002年 | 590篇 |
2001年 | 447篇 |
2000年 | 374篇 |
1999年 | 342篇 |
1998年 | 320篇 |
1997年 | 282篇 |
1996年 | 230篇 |
1995年 | 154篇 |
1994年 | 136篇 |
1993年 | 105篇 |
1992年 | 110篇 |
1991年 | 78篇 |
1990年 | 54篇 |
1989年 | 48篇 |
1988年 | 56篇 |
1987年 | 35篇 |
1986年 | 47篇 |
1985年 | 70篇 |
1984年 | 46篇 |
1983年 | 26篇 |
1982年 | 41篇 |
1981年 | 38篇 |
1980年 | 23篇 |
1979年 | 31篇 |
1978年 | 24篇 |
1977年 | 18篇 |
1976年 | 16篇 |
1973年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
1.
Qianqian Fan Zirui Liu Feng Qiu Prof. Yong Mao Prof. Qingju Liu Prof. Longzhou Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(63):e202202700
The artificially accurate design of nonmetal electrocatalysts’ active site has been a huge challenge because no pure active species with the specific structure could be strictly controlled by traditional synthetic methods. Species with a multiconfiguration in the catalyst hinder identification of the active site and the subsequent comprehension of the reaction mechanism. We have developed a novel electro-assisted molecular assembly strategy to obtain a pure pentagon ring on perfect graphene avoiding other reconstructed structures. More importantly, the active atom was confirmed by the subtle passivation process as the topmost carbon atom. Recognition of the carbon-defect electrocatalysis reaction mechanism was first downsized to the single-atom scale from the experimental perspective. It is expected that this innovative electro-assisted molecular assembly strategy could be extensively applied in the active structure-controlled synthesis of nonmetal electrocatalysts and verification of the exact active atom. 相似文献
2.
3.
《Indagationes Mathematicae》2021,32(1):55-85
We show that the differential structure of the orbit space of a proper action of a Lie group on a smooth manifold is weakly reflexive. This implies that the orbit space is a differentiable space in the sense of Smith, which ensures that the orbit space has an exterior algebra of differential forms, that satisfies Smith’s version of de Rham’s theorem. Because the orbit space is a locally closed subcartesian space, it has vector fields and their flows. 相似文献
4.
A finite support product of clones of Jensen's minimal singleton forcing is used to define a model in which any non-empty analytically definable set of reals contains an analytically definable real (the full basis theorem), but there is no analytically definable wellordering of the reals. 相似文献
5.
Prediction of drag reduction effect caused by pulsating pipe flows is examined using machine learning. First, a large set of flow field data is obtained experimentally by measuring turbulent pipe flows with various pulsation patterns. Consequently, more than 7000 waveforms are applied, obtaining a maximum drag reduction rate and maximum energy saving rate of 38.6% and 31.4%, respectively. The results indicate that the pulsating flow effect can be characterized by the pulsation period and pressure gradient during acceleration and deceleration. Subsequently, two machine learning models are tested to predict the drag reduction rate. The results confirm that the machine learning model developed for predicting the time variation of the flow velocity and differential pressure with respect to the pump voltage can accurately predict the nonlinearity of pressure gradients. Therefore, using this model, the drag reduction effect can be estimated with high accuracy. 相似文献
6.
7.
Liang Zhao 《Journal of Differential Equations》2019,266(9):5615-5624
In this paper, let be n-dimensional noncompact metric measure space which satisfies Poincaré inequality with some Ricci curvature condition. We obtain a Liouville theorem for positive weak solutions to weighted p-Lichnerowicz equation where are real constants. 相似文献
8.
9.
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
10.
Dekun Wu Dr. Qing Xu Dr. Jing Qian Prof. Xiaopeng Li Prof. Yuhan Sun 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(12):3105-3111
Covalent organic frameworks (COFs) are a new class of crystalline porous polymers comprised mainly of carbon atoms, and are versatile for the integration of heteroatoms such as B, O, and N into the skeletons. The designable structure and abundant composition render COFs useful as precursors for heteroatom-doped porous carbons for energy storage and conversion. Herein, we describe a multifunctional electrochemical catalyst obtained through pyrolysis of a bimetallic COF. The catalyst possesses hierarchical pores and abundant iron and cobalt nanoparticles embedded with standing carbon layers. By integrating these features, the catalyst exhibits excellent electrochemical catalytic activity in the oxygen reduction reaction (ORR), with a 50 mV positive half-wave potential, a higher limited diffusion current density, and a much smaller Tafel slope than a Pt-C catalyst. Moreover, the catalyst displays superior electrochemical performance toward the hydrogen evolution reaction (HER), with overpotentials of −0.26 V and −0.33 V in acidic and alkaline aqueous solution, respectively, at a current density of 10 mA cm−2. The overpotential in the catalysis of the oxygen evolution reaction (OER) was 1.59 V at the same current density. 相似文献