全文获取类型
收费全文 | 102037篇 |
免费 | 5275篇 |
国内免费 | 4787篇 |
专业分类
化学 | 42983篇 |
晶体学 | 1174篇 |
力学 | 8003篇 |
综合类 | 402篇 |
数学 | 34553篇 |
物理学 | 24984篇 |
出版年
2023年 | 471篇 |
2022年 | 599篇 |
2021年 | 780篇 |
2020年 | 1133篇 |
2019年 | 1135篇 |
2018年 | 11194篇 |
2017年 | 11013篇 |
2016年 | 7297篇 |
2015年 | 2224篇 |
2014年 | 1860篇 |
2013年 | 2336篇 |
2012年 | 6173篇 |
2011年 | 12898篇 |
2010年 | 7410篇 |
2009年 | 7813篇 |
2008年 | 8490篇 |
2007年 | 10362篇 |
2006年 | 1791篇 |
2005年 | 2661篇 |
2004年 | 2589篇 |
2003年 | 2844篇 |
2002年 | 1903篇 |
2001年 | 958篇 |
2000年 | 899篇 |
1999年 | 637篇 |
1998年 | 513篇 |
1997年 | 428篇 |
1996年 | 468篇 |
1995年 | 333篇 |
1994年 | 277篇 |
1993年 | 252篇 |
1992年 | 185篇 |
1991年 | 168篇 |
1990年 | 146篇 |
1989年 | 132篇 |
1988年 | 110篇 |
1987年 | 100篇 |
1986年 | 101篇 |
1985年 | 90篇 |
1984年 | 70篇 |
1983年 | 60篇 |
1982年 | 57篇 |
1981年 | 52篇 |
1980年 | 51篇 |
1979年 | 48篇 |
1914年 | 45篇 |
1913年 | 40篇 |
1912年 | 40篇 |
1909年 | 41篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
52.
Pengcheng Li Jie Dai Yi Xu Qichao Ran Yi Gu 《Journal of polymer science. Part A, Polymer chemistry》2019,57(14):1587-1592
A difunctional benzoxazine (coPh‐apa) with a conjugated alkyne group is synthesized by the oxidative coupling reaction from a monocycle‐benzoxazine (Ph‐apa) containing an alkyne group. A model compound, 1,4‐diphenylbutadiyne (coPa), is used to study the curing reaction process of coPh‐apa by DSC, Fourier transform infrared spectroscopy, and 13C NMR, and the results suggest that the conjugated alkyne groups are involved in the crosslinking reaction via the trimerization reaction of the conjugated alkynyl groups and the Diels–Alder reaction. Furthermore, thermal properties of the polybenzoxazine are studied by dynamic thermomechanical analysis and thermogravimetric analysis. A glass‐transition temperature (Tgs) of as high as 412 °C and a char yield of 75.6% at 800 °C under nitrogen are obtained with the aid of the conjugated alkyne groups. Its excellent heat resistance dominates most thermosetting resins and will serve for heat shields. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1587–1592 相似文献
53.
Yi Yang Yi Qiu Dr. Pifu Gong Dr. Lei Kang Gaomin Song Xiaomeng Liu Prof. Junliang Sun Prof. Zheshuai Lin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(22):5648-5651
The first alkaline-earth metal tin(II) phosphate, BaSn2(PO4)2, has been discovered, which consists of layered structures constructed from strictly alternating [SnO3]4− and [PO4]3− moieties. This compound is expected to have a large birefringence with Δn≈0.071 at 1064 nm, owing to the presence of stereochemically active lone pair metal cations. 相似文献
54.
55.
A novel tiled Ti:sapphire(Ti:S)amplifier was experimentally demonstrated with>1 J amplified chirped pulse output.Two Ti:S crystals having dimensions of 14 mm×14 mm×25 mm were tiled as the gain medium in a four-pass amplifier.Maximum output energy of 1.18 J was obtained with 2.75 J pump energy.The energy conversion efficiency of the tiled Ti:S amplifier was comparable with a single Ti:S amplifier.The laser pulse having the maximum peak power of 28 TW was obtained after the compressor.Moreover,the influence of the beam gap on the far field was discussed.This novel tiled Ti:S amplifier technique can provide a potential way for 100 PW or EW lasers in the future. 相似文献
56.
Acta Mathematica Sinica, English Series - In this paper, we give some sufficient conditions for extended neighborhood coronas to have Laplacian perfect state transfer. We also give some conditions... 相似文献
57.
58.
Li Zhisheng Jiang Haokai Cheng Yanying Gao Yunji Chen Longfei Zhang Yuchun Li Tao Xing Shaoshuai 《Journal of Thermal Analysis and Calorimetry》2022,147(21):12139-12154
Journal of Thermal Analysis and Calorimetry - Few investigations have focused on the influence of longitudinal fire source location on the temperature profile of smoke induced by fire in a tunnel... 相似文献
59.
Zhao Yi Liang Kaitai Zhao Yanqi Yang Bo Ming Yang Panaousis Emmanouil 《Designs, Codes and Cryptography》2022,90(4):921-937
Designs, Codes and Cryptography - An algorithm substitution attack (ASA) can undermine the security of cryptographic primitives by subverting the original implementation. An ASA succeeds when it... 相似文献
60.
This paper concerns with the problem of how to running an insurance company to maximize his total discounted expected dividends. In our model, the dividend rate is limited in and the company is allowed to transfer any proportion of risk by reinsuring. So there are two strategies which we call dividend strategy and reinsurance strategy. The objective function and the corresponding optimal two strategies are the solution and the two free boundaries of the following Barenblatt parabolic equation under certain boundary conditions on an angular domain The main effort is to analyze the properties of the solution and the free boundaries to show the optimal decision for the insurance company. 相似文献