全文获取类型
收费全文 | 121401篇 |
免费 | 29512篇 |
国内免费 | 21882篇 |
专业分类
化学 | 80383篇 |
晶体学 | 1519篇 |
力学 | 8041篇 |
综合类 | 340篇 |
数学 | 14690篇 |
物理学 | 67822篇 |
出版年
2023年 | 1600篇 |
2022年 | 1664篇 |
2021年 | 2167篇 |
2020年 | 2713篇 |
2019年 | 3149篇 |
2018年 | 2931篇 |
2017年 | 3432篇 |
2016年 | 4342篇 |
2015年 | 4478篇 |
2014年 | 4802篇 |
2013年 | 7370篇 |
2012年 | 8318篇 |
2011年 | 10022篇 |
2010年 | 11980篇 |
2009年 | 11972篇 |
2008年 | 6319篇 |
2007年 | 5607篇 |
2006年 | 4998篇 |
2005年 | 4971篇 |
2004年 | 5245篇 |
2003年 | 4271篇 |
2002年 | 4045篇 |
2001年 | 4043篇 |
2000年 | 3193篇 |
1999年 | 3440篇 |
1998年 | 2914篇 |
1997年 | 2683篇 |
1996年 | 3023篇 |
1995年 | 3360篇 |
1994年 | 3386篇 |
1993年 | 3284篇 |
1992年 | 2866篇 |
1991年 | 2481篇 |
1990年 | 2073篇 |
1989年 | 2104篇 |
1988年 | 2027篇 |
1987年 | 1296篇 |
1986年 | 1336篇 |
1985年 | 984篇 |
1984年 | 1068篇 |
1982年 | 946篇 |
1981年 | 779篇 |
1980年 | 820篇 |
1979年 | 547篇 |
1978年 | 546篇 |
1977年 | 643篇 |
1976年 | 1056篇 |
1973年 | 448篇 |
1972年 | 538篇 |
1971年 | 434篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
1.
Yuanbo Gao Tingting Yang Xueli Wang Jizong Chen Yong He 《Journal of polymer science. Part A, Polymer chemistry》2022,60(10):1610-1623
Two series of novel alternating copolyoxamides (PAnT-alt-n2 and PAn2-alt-62) are synthesized via solution/solid-state polycondensation (SSP). The alternating structures are analyzed carefully with 1H NMR and 13C NMR spectra. The melting behaviors, thermal stabilities, crystal structures and crystallinities are systematically evaluated by DSC, TGA and WAXD. The results reveal that these alternating copolyoxamides possess almost perfect alternating chain structures and have high melting temperature (Tm > 270 °C), high crystallinity (Xc > 32%) and high decomposition temperature (T5 > 405 °C) as well as low saturated water absorption (<3.5 wt%), which suggests that they have high potential as engineering plastic of high heat resistant. 相似文献
2.
Zhang Bing Yang Jie-qin Liu Ying Hu Bin Yang Yang Zhao Li Lu Qiang 《Cellulose (London, England)》2022,29(12):6565-6578
Cellulose - Heating is essential in various biomass pre-treatments and thermal conversion processes. It is of practical significance to study the characteristics of cellulose-lignin and... 相似文献
3.
Nonlinear Dynamics - The perovskite solar cell (PSC) is one of the most promising photovoltaic candidates along with the highly increasing demand for green electricity. One of the main concerns... 相似文献
4.
Song Zhang Luke A. Galuska Xiaodan Gu 《Journal of polymer science. Part A, Polymer chemistry》2022,60(7):1108-1129
Thin films with a nanometer-scale thickness are of great interest to both scientific and industrial communities due to their numerous applications and unique behaviors different from the bulk. However, the understanding of thin-film mechanics is still greatly hampered due to their intrinsic fragility and the lack of commercially available experimental instruments. In this review, we first discuss the progression of thin-film mechanical testing methods based on the supporting substrate: film-on-solid substrate method, film-on-water tensile tests, and water-assisted free-standing tensile tests. By comparing past studies on a model polymer, polystyrene, the effect of different substrates and confinement effect on the thin-film mechanics is evaluated. These techniques have generated fruitful scientific knowledge in the field of organic semiconductors for the understanding of structure–mechanical property relationships. We end this review by providing our perspective for their bright prospects in much broader applications and materials of interest. 相似文献
5.
Yujie Gao Zhiye Qiu Lei Liu Mengmeng Li Bingjie Xu Dan Yu Dongming Qi Jindan Wu 《Journal of polymer science. Part A, Polymer chemistry》2022,60(15):2191-2212
Refractory wounds have always been an important issue to healthcare systems, whose healing process is always delayed by multiple factors, including bacterial infections, chronic inflammation, and excessive exudates, etc. Employing multifunctional wound dressings is recognized as an effective strategy to deal with refractory wounds, which has yielded promising outcomes in recent years. Among these advanced wound dressings, fibrous dressings have gained growing attention due to their unique merits. Such wound dressings have demonstrated great potential in delivering theranostic agents, such as antibacterial agents, anti-inflammatory drugs, growth factors, and diagnostic probes, etc., for the purposes of accelerating wound healing. This paper reviews the development of multifunctional fibrous dressings and their applications in treating refractory wounds. The construction approaches of novel fibrous dressing with capabilities of antibacterial, anti-inflammation, exudate management and diagnosis were also introduced. Furthermore, the existing problems and challenges are also discussed briefly. 相似文献
6.
High Energy Chemistry - Modification of Polyvinylidene fluoride (PVDF) by radiation grafting is a research hotspot in recent years. In this study, the monomer 2-Hydroxyethyl methacrylate (HEMA) was... 相似文献
7.
8.
Saqib Kamal Arif I. Inamdar Kuan-Ru Chiou Batjargal Sainbileg Muhammad Usman Jenq-Wei Chen Tzuoo-Tsair Luo Michitoshi Hayashi Chen-Hsiung Hung Wen-Feng Liaw Kuang-Lieh Lu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(30):e202103905
The dielectric properties of coordination polymers has been a topic of recent interest, but the role of different functional groups on the dielectric properties of these polymers has not yet been fully addressed. Herein, the effects of electron-donating (R=NH2) and electron-withdrawing (R=NO2) groups on the dielectric behavior of such materials were investigated for two thermally stable and guest-free Zn-based coordination polymers, [Zn(L1)(L2)]n ( 1 ) and [Zn(L1)(L3)]n ( 2 ) [L1=2-(2-pyridyl) benzimidazole (Pbim), L2=5-aminoisophthalate (Aip), and L3=5-nitroisophthalate (Nip)]. The results of dielectric studies of 1 revealed that it possesses a high dielectric constant (κ=65.5 at 1 kHz), while compound 2 displayed an even higher dielectric constant (κ=110.3 at 1 kHz). The electron donating and withdrawing effects of the NH2 and NO2 substituents induce changes in the polarity of the polymers, which is due to the inductive effect from the aryl ring for both NO2 and NH2. Theoretical results from density functional theory (DFT) calculations, which also support the experimental findings, show that both compounds have a distinct electronic behavior with diverse wide bandgaps. The significance of the current work is to provide information about the structure-dielectric property relationships. So, this study promises to pave the way for further research on the effects of different functional groups on coordination polymers on their dielectric properties. 相似文献
9.
Hao Lu Xiaodong Wang Hang Wang Andong Zhang Xinming Zheng Na Yu Zheng Tang Xinjun Xu Yahui Liu Ya-Nan Chen Zhishan Bo 《中国科学:化学(英文版)》2022,65(3):594-601
Three nonfused ring electron acceptors (NFREAs) TTC6,TT-C8T and TT-TC8 were purposefully designed and synthesized.The molecular geometry can be adjusted by the steric hindrance of lateral substituents.According to the DFT calculations,from TTC6 to TT-C8T and TT-TC8,planarity of the molecular backbone is gradually improved,accompanying with the enhancing of intramolecular charge transfer effect.As for TT-TC8,the two phenyl substituents are almost perpendicular to the molecular backbone,which endues the acceptor with good solubility and suppresses it to form over-aggregation.Multidirectional regular molecular orientation and closer molecular stacking are formed in TT-TC8 film.As a result,TT-TC8 based devices afford the highest PCE of 13.13%,which is much higher than that of TTC6 (4.41%) and TT-C8T (10.42%) and among the highest PCE values based on NFREAs. 相似文献
10.