全文获取类型
收费全文 | 65171篇 |
免费 | 7399篇 |
国内免费 | 7386篇 |
专业分类
化学 | 29173篇 |
晶体学 | 578篇 |
力学 | 2072篇 |
综合类 | 559篇 |
数学 | 4521篇 |
物理学 | 14294篇 |
综合类 | 28759篇 |
出版年
2024年 | 185篇 |
2023年 | 743篇 |
2022年 | 1462篇 |
2021年 | 1571篇 |
2020年 | 1672篇 |
2019年 | 1586篇 |
2018年 | 1436篇 |
2017年 | 1449篇 |
2016年 | 2041篇 |
2015年 | 2514篇 |
2014年 | 3268篇 |
2013年 | 4032篇 |
2012年 | 4648篇 |
2011年 | 4895篇 |
2010年 | 3988篇 |
2009年 | 4089篇 |
2008年 | 4627篇 |
2007年 | 4389篇 |
2006年 | 4023篇 |
2005年 | 3510篇 |
2004年 | 3021篇 |
2003年 | 2588篇 |
2002年 | 3134篇 |
2001年 | 2687篇 |
2000年 | 2056篇 |
1999年 | 1805篇 |
1998年 | 1130篇 |
1997年 | 1131篇 |
1996年 | 1013篇 |
1995年 | 897篇 |
1994年 | 825篇 |
1993年 | 656篇 |
1992年 | 550篇 |
1991年 | 495篇 |
1990年 | 422篇 |
1989年 | 388篇 |
1988年 | 278篇 |
1987年 | 221篇 |
1986年 | 138篇 |
1985年 | 86篇 |
1984年 | 61篇 |
1983年 | 48篇 |
1982年 | 40篇 |
1981年 | 32篇 |
1980年 | 27篇 |
1978年 | 12篇 |
1977年 | 10篇 |
1976年 | 14篇 |
1975年 | 13篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 531 毫秒
21.
22.
23.
搪瓷制品鳞爆缺陷已经成为国内外研究重点。为提高搪瓷用钢的抗鳞爆性能,非常有必要了解搪瓷层的鳞爆机理。综述了国内外研究鳞爆机理以及氢扩散影响因素的现状。 相似文献
24.
In the view of substrate availability, atomic efficiency and cost, directly using arenols as coupling partners in cross‐coupling, would be one of the most attractive goals. Up to date, many efforts have been made to activate the C—O bond of phenols with different strategies, for example, through in‐situ formed intermediates, through a catalytic reductive dearomatization‐condensation‐rearomatization sequence or catalytic deoxygenation. In this review, we summarized recent advances in cross‐couplings of arenols as the electrophiles via C—O activation. 相似文献
25.
Polypyrrole Shell@3D‐Ni Metal Core Structured Electrodes for High‐Performance Supercapacitors 下载免费PDF全文
Gao‐Feng Chen Yu‐Zhi Su Pan‐Yong Kuang Zhao‐Qing Liu Dao‐Yi Chen Xu Wu Nan Li Prof. Shi‐Zhang Qiao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(12):4614-4621
Three‐dimensional (3D) nanometal films serving as current collectors have attracted much interest recently owing to their promising application in high‐performance supercapacitors. In the process of the electrochemical reaction, the 3D structure can provide a short diffusion path for fast ion transport, and the highly conductive nanometal may serve as a backbone for facile electron transfer. In this work, a novel polypyrrole (PPy) shell@3D‐Ni‐core composite is developed to enhance the electrochemical performance of conventional PPy. With the introduction of a Ni metal core, the as‐prepared material exhibits a high specific capacitance (726 F g?1 at a charge/discharge rate of 1 A g?1), good rate capability (a decay of 33 % in Csp with charge/discharge rates increasing from 1 to 20 A g?1), and high cycle stability (only a small decrease of 4.2 % in Csp after 1000 cycles at a scan rate of 100 mV s?1). Furthermore, an aqueous symmetric supercapacitor device is fabricated by using the as‐prepared composite as electrodes; the device demonstrates a high energy density (≈21.2 Wh kg?1) and superior long‐term cycle ability (only 4.4 % and 18.6 % loss in Csp after 2000 and 5000 cycles, respectively). 相似文献
26.
以应用ProCAST和MAGMAsoft 2款软件为例,针对铸造工艺仿真设计前处理和过程处理每个环节的主要内容与使用方法进行了较为详细地归纳、分析和总结。提出了处理过程的技术路线,并系统地介绍了每项应用内容的操作平台与使用步骤,从而为高效地应用铸造工艺仿真设计提供理论和技术支持。 相似文献
27.
Recently,the nested Mach–Zehnder interferometer[Phys.Rev.Lett.111,240402(2013)]was modified by adding Dove prisms in a paper[Quantum Stud.:Math.Found.2,255(2015)],and an interesting result is that,after the Dove prisms were inserted,a signal at the first mirror of the nested interferometer was obtained.But,according to the former original paper,the photons have never been present near that mirror.In this work,we interpret this result naturally by resorting to the three-path interference method.Moreover,we find that even though the photons have been somewhere,they can hide the trace of being there. 相似文献
28.
Youchao Wang Na Tian Weize Sun Boerhan Rena Xusheng Guo Yang Feng Chao Li Xuesong Wang Qianxiong Zhou 《Particle & Particle Systems Characterization》2020,37(5):2000045
Photoactivated chemotherapy (PACT) has appealing merits over traditional chemotherapy as well as photodynamic therapy (PDT) by virtue of its spatial and temporal control on drug activity and oxygen-independent mechanisms of action. However, the short photoactivation wavelengths, e.g., visible light–activated Ru(II)-based PACT agents, limit the clinical application severely. In this work, a facile construction of supramolecular nanoparticles from a poly(ethylene glycol) (PEG)-modified [Ru(dip)2(py-SO3)]+ (abbreviated as Ru-PEG, dip = 4,7-diphenyl-1,10-phenanthroline, py-SO3 = pyridine-2-sulfonate) and 1,3-phenylenebis(pyren-1-ylmethanone) (BP) is shown. While Ru-PEG may undergo photoinduced ligand dissociation and release anticancer species of [Ru(dip)2(H2O)2]2+, BP has extremely large two-photon absorption cross sections (δ2) in the NIR region and intense fluorescence over the wavelengths where Ru-PEG has strong absorption. Thus, two-photon excitation of BP followed by an efficient Förster resonance energy transfer (FRET) from BP to Ru-PEG may lead to a potent inactivation against cisplatin-resistant cancer cells and 3D multicellular tumor spheroids (MCTSs). The residue fluorescence of BP also allows the cellular uptake of the particles to be visualized. This work provides a universal and convenient strategy to realize theranostic PACT in the ideal phototherapeutic window of 650–900 nm. 相似文献
29.
30.
讨论了3×3阶正交矩阵的特征值和迹的关系,证明了迹为整数的3×3阶正交矩阵的谱可由迹确定,为应用广泛的3×3阶正交矩阵的谱的计算提供了简单实用的方法. 相似文献