全文获取类型
收费全文 | 1285639篇 |
免费 | 33436篇 |
国内免费 | 10466篇 |
专业分类
化学 | 636062篇 |
晶体学 | 20098篇 |
力学 | 74992篇 |
综合类 | 319篇 |
数学 | 239722篇 |
物理学 | 358348篇 |
出版年
2021年 | 14323篇 |
2020年 | 16681篇 |
2019年 | 16867篇 |
2016年 | 27946篇 |
2015年 | 21490篇 |
2014年 | 31495篇 |
2013年 | 75748篇 |
2012年 | 36025篇 |
2011年 | 29843篇 |
2010年 | 36009篇 |
2009年 | 39014篇 |
2008年 | 29700篇 |
2007年 | 24251篇 |
2006年 | 32602篇 |
2005年 | 23700篇 |
2004年 | 26070篇 |
2003年 | 25325篇 |
2002年 | 26854篇 |
2001年 | 24507篇 |
2000年 | 22550篇 |
1999年 | 21827篇 |
1998年 | 20999篇 |
1997年 | 21058篇 |
1996年 | 21310篇 |
1995年 | 19431篇 |
1994年 | 18763篇 |
1993年 | 18244篇 |
1992年 | 17701篇 |
1991年 | 18022篇 |
1990年 | 17254篇 |
1989年 | 17313篇 |
1988年 | 16812篇 |
1987年 | 16850篇 |
1986年 | 15700篇 |
1985年 | 22179篇 |
1984年 | 23530篇 |
1983年 | 19795篇 |
1982年 | 21542篇 |
1981年 | 20771篇 |
1980年 | 20090篇 |
1979年 | 20088篇 |
1978年 | 21506篇 |
1977年 | 21055篇 |
1976年 | 20715篇 |
1975年 | 19382篇 |
1974年 | 19011篇 |
1973年 | 19490篇 |
1972年 | 14014篇 |
1968年 | 11889篇 |
1967年 | 12269篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
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
102.
Dr. Manussada Ratanasak Takumi Murata Taishin Adachi Prof. Jun-ya Hasegawa Prof. Tadashi Ema 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(58):e202202210
BPh3 catalyzes the N-methylation of secondary amines and the C-methylenation (methylene-bridge formation between aromatic rings) of N,N-dimethylanilines or 1-methylindoles in the presence of CO2 and PhSiH3; these reactions proceed at 30–40 °C under solvent-free conditions. In contrast, B(C6F5)3 shows little or no activity. 11B NMR spectra suggested the generation of [HBPh3]−. The detailed mechanism of the BPh3-catalyzed N-methylation of N-methylaniline ( 1 ) with CO2 and PhSiH3 was studied by using DFT calculations. BPh3 promotes the conversion of two substrates (N-methylaniline and CO2) into a zwitterionic carbamate to give three-component species [Ph(Me)(H)N+CO2−⋅⋅⋅BPh3]. The carbamate and BPh3 act as the nucleophile and Lewis acid, respectively, for the activation of PhSiH3 to generate [HBPh3]−, which is used to produce key CO2-derived species, such as silyl formate and bis(silyl)acetal, essential for the N-methylation of 1 . DFT calculations also suggested other mechanisms involving water for the generation of [HBPh3]− species. 相似文献
103.
Meihua Shen Dr. Xinpeng Zhao Dr. Lu Han Nanxi Jin Prof. Song Liu Prof. Tao Jia Prof. Zhijun Chen Prof. Xiuhua Zhao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(20):e202104137
Solar-driven interfacial vaporization by localizing solar-thermal energy conversion to the air−water interface has attracted tremendous attention. In the process of converting solar energy into heat energy, photothermal materials play an essential role. Herein, a flexible solar-thermal material di-cyan substituted 5,12-dibutylquinacridone (DCN−4CQA)@Paper was developed by coating photothermal quinacridone derivatives on the cellulose paper. The DCN−4CQA@Paper combines desired chemical and physical properties, broadband light-absorbing, and shape-conforming abilities that render efficient photothermic vaporization. Notably, synergetic coupling of solar-steam and solar-electricity technologies by integrating DCN−4CQA@Paper and the thermoelectric devices is realized without trade-offs, highlighting the practical consideration toward more impactful solar heat exploitation. Such solar distillation and low-grade heat-to-electricity generation functions can provide potential opportunities for fresh water and electricity supply in off-grid or remote areas. 相似文献
104.
Journal of Applied Spectroscopy - The elemental composition of one- and two-rupee coins issued in different years by the Reserve Bank of India (RBI) was investigated using laser-induced breakdown... 相似文献
105.
Doklady Mathematics - Two classes of Taylor-type formulas for arbitrary continuous functions on intervals are obtained using Bernstein polynomials. These formulas are applicable to both smooth... 相似文献
106.
Danilov Felix I. Bogdanov Dmytro A. Smyrnova Olena V. Korniy Sergiy A. Protsenko Vyacheslav S. 《Journal of Solid State Electrochemistry》2022,26(4):939-957
Journal of Solid State Electrochemistry - The electrochemical deposition of a nickel–iron alloy from a plating solution based on a deep eutectic solvent (a eutectic mixture of ethylene glycol... 相似文献
107.
Dr. Ruijuan Yao Prof. Di Liu Dr. Huihui Wan Dr. Yongqiang Mei Jiahui Wang Dr. Rui Cai Dr. Huimin Zhang Dr. Yuzhen Zhao Dr. Zemin He 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(71):e202202269
By linking the carbazole unit to the nitrogen atom of acridone through phenyl or pyridyl, two compounds, named 10-(4-(9H-carbazol-9-yl)phenyl)acridin-9(10H)-one (AC-Ph-Cz) and 10-(5-(9H-carbazol-9-yl)pyridin-2-yl)acridin-9(10H)-one (AC-Py-Cz) were designed and synthesized. These two materials, characterized with highly twisted and rigid structure, good thermal stability, and balanced carrier-transporting properties, were employed as host materials for green phosphorescent and thermally activated delayed fluorescent organic light-emitting diodes (OLEDs). The carbazole group, despite its small contribution to the highest occupied molecular orbitals (HOMOs) of these two materials, plays an essential role as an intramolecular host in energy delivering and improving the hole transporting ability of these two hosts. The incorporation of the electron-deficient pyridyl group as a linking group slightly improves the electron transporting capability of AC-Py-Cz. The green phosphorescent OLED (PhOLED) based on AC-Py-Cz exhibited excellent device performance with a turn-on voltage of 2.5 V, a maximum power efficiency and an external quantum efficiency (ηext) of 89.8 lm W−1 and 25.2 %, respectively, benefitting from the better charge-balancing ability of AC-Py-Cz host due to the presence of the pyridyl bridge. More importantly, all the devices based on these two hosts showed low efficiency roll-off at high brightness due to the suppressed non-radiative transition in the emitting layer. In particular, the AC-Py-Cz-hosted green PhOLED exhibited an efficiency roll-off of 1.6 % from the maximum next at a high brightness of 1000 cd m−2 and a roll-off of 15.9 % at an extremely high brightness of 10000 cd m−2. This study manifests that acridone-based host materials have great potential in fabricating OLEDs with low efficiency roll-off. 相似文献
108.
Siberian Mathematical Journal - We give a simple proof of one assertion used in solving Waring’s problem. 相似文献
109.
McElroy Tucker S. Politis Dimitris N. 《Statistical Inference for Stochastic Processes》2022,25(3):471-483
Statistical Inference for Stochastic Processes - The problem of linear interpolation in the context of a multivariate time series having multiple (possibly non-consecutive) missing values is... 相似文献
110.
Siberian Mathematical Journal - A lattice homomorphism between quasi-Banach lattices is known to be compact if and only if it is a sum of a series of rank one lattice... 相似文献