全文获取类型
收费全文 | 37689篇 |
免费 | 6603篇 |
国内免费 | 5420篇 |
专业分类
化学 | 28148篇 |
晶体学 | 443篇 |
力学 | 2310篇 |
综合类 | 415篇 |
数学 | 4186篇 |
物理学 | 14210篇 |
出版年
2024年 | 129篇 |
2023年 | 746篇 |
2022年 | 1353篇 |
2021年 | 1308篇 |
2020年 | 1534篇 |
2019年 | 1502篇 |
2018年 | 1340篇 |
2017年 | 1249篇 |
2016年 | 1955篇 |
2015年 | 1856篇 |
2014年 | 2240篇 |
2013年 | 2853篇 |
2012年 | 3364篇 |
2011年 | 3453篇 |
2010年 | 2402篇 |
2009年 | 2359篇 |
2008年 | 2667篇 |
2007年 | 2322篇 |
2006年 | 2148篇 |
2005年 | 1917篇 |
2004年 | 1447篇 |
2003年 | 1232篇 |
2002年 | 1238篇 |
2001年 | 976篇 |
2000年 | 857篇 |
1999年 | 783篇 |
1998年 | 587篇 |
1997年 | 538篇 |
1996年 | 563篇 |
1995年 | 514篇 |
1994年 | 406篇 |
1993年 | 322篇 |
1992年 | 295篇 |
1991年 | 258篇 |
1990年 | 216篇 |
1989年 | 169篇 |
1988年 | 136篇 |
1987年 | 121篇 |
1986年 | 86篇 |
1985年 | 81篇 |
1984年 | 46篇 |
1983年 | 41篇 |
1982年 | 21篇 |
1981年 | 27篇 |
1980年 | 14篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1957年 | 13篇 |
1936年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 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.
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
3.
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
4.
5.
为提高煤与瓦斯突出矿井瓦斯抽放效果,建立了3个一级指标、14个二级指标的突出矿井瓦斯抽放限制影响因素评价指标体系,利用AHP和熵权法分别确定指标因子主、客观权重.通过实地调研分析和反馈验证了AHP-熵权法的可行性和正确性,利用加权平均法确定评价模型的综合权重.研究表明:封孔方式、钻孔半径、抽放时间、煤体裂隙发育程度和抽放负压是目前影响煤矿瓦斯抽放效果的主控因素. 相似文献
6.
7.
The Ramanujan Journal - We calculate the dimensions of the spaces of invariant vectors under the Klingen congruence subgroup of level $${\mathfrak {p}}^2$$ for all irreducible, admissible... 相似文献
8.
Science China Mathematics - Linear factor models are familiar tools used in many fields. Several pioneering literatures established foundational theoretical results of the quasi-maximum likelihood... 相似文献
9.
10.
Pengjin Qin Li-An Wang Prof. Joseph M. O'Connor Prof. Kim K. Baldridge Yifan Li Burak Tufekci Jiyue Chen Prof. Arnold L. Rheingold 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(41):18114-18121
Triene 6π electrocyclization, wherein a conjugated triene undergoes a concerted stereospecific cycloisomerization to a cyclohexadiene, is a reaction of great historical and practical significance. In order to circumvent limitations imposed by the normally harsh reaction conditions, chemists have long sought to develop catalytic variants based upon the activating power of metal–alkene coordination. Herein, we demonstrate the first successful implementation of such a strategy by utilizing [(C5H5)Ru(NCMe)3]PF6 as a precatalyst for the disrotatory 6π electrocyclization of highly substituted trienes that are resistant to thermal cyclization. Mechanistic and computational studies implicate hexahapto transition-metal coordination as responsible for lowering the energetic barrier to ring closure. This work establishes a foundation for the development of new catalysts for stereoselective electrocyclizations. 相似文献