全文获取类型
收费全文 | 514334篇 |
免费 | 9560篇 |
国内免费 | 4636篇 |
专业分类
化学 | 266796篇 |
晶体学 | 7548篇 |
力学 | 23965篇 |
综合类 | 314篇 |
数学 | 71353篇 |
物理学 | 158554篇 |
出版年
2021年 | 2785篇 |
2020年 | 3351篇 |
2019年 | 3278篇 |
2018年 | 11992篇 |
2017年 | 12795篇 |
2016年 | 9688篇 |
2015年 | 5934篇 |
2014年 | 6797篇 |
2013年 | 19005篇 |
2012年 | 19017篇 |
2011年 | 30094篇 |
2010年 | 18601篇 |
2009年 | 18399篇 |
2008年 | 26532篇 |
2007年 | 29809篇 |
2006年 | 16271篇 |
2005年 | 21773篇 |
2004年 | 16648篇 |
2003年 | 14795篇 |
2002年 | 12657篇 |
2001年 | 12881篇 |
2000年 | 10062篇 |
1999年 | 7936篇 |
1998年 | 6508篇 |
1997年 | 6310篇 |
1996年 | 6386篇 |
1995年 | 5862篇 |
1994年 | 5453篇 |
1993年 | 5199篇 |
1992年 | 5751篇 |
1991年 | 5623篇 |
1990年 | 5246篇 |
1989年 | 5068篇 |
1988年 | 5334篇 |
1987年 | 5051篇 |
1986年 | 4823篇 |
1985年 | 6905篇 |
1984年 | 7031篇 |
1983年 | 5763篇 |
1982年 | 6389篇 |
1981年 | 6282篇 |
1980年 | 6061篇 |
1979年 | 6138篇 |
1978年 | 6286篇 |
1977年 | 6142篇 |
1976年 | 6138篇 |
1975年 | 5960篇 |
1974年 | 5688篇 |
1973年 | 5993篇 |
1972年 | 3520篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
11.
Laguel Yassine Pillutla Krishna Malick Jérôme Harchaoui Zaid 《Set-Valued and Variational Analysis》2021,29(4):967-996
Set-Valued and Variational Analysis - R. Tyrell Rockafellar and his collaborators introduced, in a series of works, new regression modeling methods based on the notion of superquantile (or... 相似文献
12.
13.
Li Y. Shi W. H. Dong L. M. Xu S. X. Huang H. J. Yin J. R. 《Journal of Applied Spectroscopy》2022,89(3):534-541
Journal of Applied Spectroscopy - Sr3B2O6:Dy3+, Eu3+ single-matrix white-light-emitting materials are prepared using the high-temperature solid-state method. The microstructure, emission spectrum,... 相似文献
14.
15.
Ajit Kumar Singh Seulgi Ji Baghendra Singh Chittaranjan Das Heechae Choi Prashanth W. Menezes Arindam Indra 《Materials Today Chemistry》2022
Herein, we report a Mott-Schottky catalyst by entrapping cobalt nanoparticles inside the N-doped graphene shell (Co@NC). The Co@NC delivered excellent oxygen evolution activity with an overpotential of merely 248 mV at a current density of 10 mA cm–2 with promising long-term stability. The importance of Co encapsulated in NC has further been demonstrated by synthesizing Co nanoparticles without NC shell. The synergy between the hexagonal close-packed (hcp) and face-centered cubic (fcc) Co plays a major role to improve the OER activity, whereas the NC shell optimizes the electronic structure, improves the electron conductivity, and offers a large number of active sites in Co@NC. The density functional theory calculations have revealed that the hcp Co has a dominant role in the surface reaction of electrocatalytic oxygen evolution, whereas the fcc phase induces the built-in electric field at the interfaces with N-doped graphene to accelerate the H+ ion transport. 相似文献
16.
Restricted testing conditions were considered recently. For the maximal operator, Hytönen, Li and Sawyer [8] first obtained parental testing condition. Later, they [9] showed that it suffices to restrict testing to doubling cubes. Chen and Lacey [3] gave a similar restricted testing condition. In our paper, we discuss a version of the latter in the multilinear setting.
相似文献17.
S. Venkatesan S. Suresh P. Ramu M. Kandasamy J. Arumugam S. Thambidurai K.M. Prabu N. Pugazhenthiran 《印度化学会志》2022,99(5):100436
A facile biosynthesis route was followed to prepare zinc oxide nanoparticles (ZnO NPs) using Euphorbia milii (E. milii) leaf constituents. The SEM images exhibited presence of spherical ZnO NPs and the corresponding TEM images disclosed monodisperse nature of the ZnO NPs with diameter ranges between 12 and 20 nm. The Brunauer–Emmett–Teller (BET) analysis revealed that the ZnO NPs have specific surface area of 20.46 m2/g with pore diameter of 2 nm–10 nm and pore volume of 0.908 cm3/g. The EDAX spectrum exemplified the existence of Zn and O elements and non-appearance of impurities that confirmed pristine nature of the ZnO NPs. The XRD pattern indicated crystalline peaks corresponding to hexagonal wurtzite structured ZnO with an average crystallite size of 16.11 nm. The FTIR spectrum displayed strong absorption bands at 512 and 534 cm?1 related to ZnO. The photocatalytic action of ZnO NPs exhibited noteworthy degradation of methylene blue dye under natural sunlight illumination. The maximum degradation efficiency achieved was 98.17% at an illumination period of 50 min. The reusability study proved considerable photostability of the ZnO NPs during photocatalytic experiments. These findings suggest that the E. milii leaf constituents can be utilized as suitable biological source to synthesis ZnO NPs for photocatalytic applications. 相似文献
18.
Bingjie Chen Dr. Lianhai Zu Dr. Yao Liu Dr. Ruijing Meng Yutong Feng Prof. Chengxin Peng Feng Zhu Tianzi Hao Jiajia Ru Prof. Yonggang Wang Prof. Jinhu Yang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(8):3161-3166
Incorporating nanoscale Si into a carbon matrix with high dispersity is desirable for the preparation of lithium-ion batteries (LIBs) but remains challenging. A space-confined catalytic strategy is proposed for direct superassembly of Si nanodots within a carbon (Si NDs⊂C) framework by copyrolysis of triphenyltin hydride (TPT) and diphenylsilane (DPS), where Sn atomic clusters created from TPT pyrolysis serve as the catalyst for DPS pyrolysis and Si catalytic growth. The use of Sn atomic cluster catalysts alters the reaction pathway to avoid SiC generation and enable formation of Si NDs with reduced dimensions. A typical Si NDs⊂C framework demonstrates a remarkable comprehensive performance comparable to other Si-based high-performance half LIBs, and higher energy densities compared to commercial full LIBs, as a consequence of the high dispersity of Si NDs with low lithiation stress. Supported by mechanic simulations, this study paves the way for construction of Si/C composites suitable for applications in future energy technologies. 相似文献
19.
20.
Haixing Guan Qianwen Zhang Prof. Dr. Patrick J. Walsh Prof. Dr. Jianyou Mao 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(13):5210-5215
A unique nickel/organic photoredox co-catalyzed asymmetric reductive cross-coupling between α-chloro esters and aryl iodides is developed. This cross-electrophile coupling reaction employs an organic reductant (Hantzsch ester), whereas most reductive cross-coupling reactions use stoichiometric metals. A diverse array of valuable α-aryl esters is formed under these conditions with high enantioselectivities (up to 94 %) and good yields (up to 88 %). α-Aryl esters represent an important family of nonsteroidal anti-inflammatory drugs. This novel synergistic strategy expands the scope of Ni-catalyzed reductive asymmetric cross-coupling reactions. 相似文献