全文获取类型
收费全文 | 3453篇 |
免费 | 655篇 |
国内免费 | 560篇 |
专业分类
化学 | 2652篇 |
晶体学 | 39篇 |
力学 | 165篇 |
综合类 | 35篇 |
数学 | 433篇 |
物理学 | 1344篇 |
出版年
2024年 | 8篇 |
2023年 | 88篇 |
2022年 | 94篇 |
2021年 | 138篇 |
2020年 | 161篇 |
2019年 | 172篇 |
2018年 | 148篇 |
2017年 | 136篇 |
2016年 | 185篇 |
2015年 | 205篇 |
2014年 | 212篇 |
2013年 | 256篇 |
2012年 | 292篇 |
2011年 | 314篇 |
2010年 | 256篇 |
2009年 | 237篇 |
2008年 | 260篇 |
2007年 | 199篇 |
2006年 | 184篇 |
2005年 | 168篇 |
2004年 | 115篇 |
2003年 | 78篇 |
2002年 | 112篇 |
2001年 | 76篇 |
2000年 | 61篇 |
1999年 | 69篇 |
1998年 | 39篇 |
1997年 | 51篇 |
1996年 | 65篇 |
1995年 | 67篇 |
1994年 | 49篇 |
1993年 | 40篇 |
1992年 | 20篇 |
1991年 | 29篇 |
1990年 | 17篇 |
1989年 | 14篇 |
1988年 | 11篇 |
1987年 | 4篇 |
1986年 | 9篇 |
1985年 | 7篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 7篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1965年 | 3篇 |
1936年 | 1篇 |
排序方式: 共有4668条查询结果,搜索用时 15 毫秒
81.
YongGuang Tu GuoNing Xu XiaoYu Yang YiFei Zhang ZhaoJie Li Rui Su DeYing Luo WenQiang Yang Ying Miao Rong Cai LuHua Jiang XiaoWei Du YanChu Yang QianShi Liu Yang Gao Shuai Zhao Wei Huang QiHuang Gong Rui Zhu 《中国科学:物理学 力学 天文学(英文版)》2019,(7)
<正>The metal halide perovskite materials demonstrate outstanding performance in photovoltaics because of their excellent optoelectronic properties [1-7]. The perovskite solar cells (PSCs) exhibiting outstanding efficiency [8,9], high power-per-weight [10], and excellent radiation resistance[11-13] are considered to be promising for developing the new-generation energy technology for space application.However, the extreme space environment would impose 相似文献
82.
83.
Herein we report a novel visible-light-mediated external reductant-free reductive cross coupling for the construction of C sp~2–C sp~3 bonds. A variety of benzylammonium salts underwent selective coupling with(hetero)aryl nitriles to deliver important diarylmethanes under mild reaction conditions. Importantly, photocatalysts can be omitted for many cases, which might involve the electron donor acceptor(EDA) complex. Mechanistic studies indicated benzylic radicals might be involved as the key intermediates. Moreover, the in situ generated NMe_3 via cleavage of C–N bond in ammonium salts acts as the electron donor,thus avoiding the use of external-reductant. 相似文献
84.
Lvye Ai Mengzhen Liu Xiaoming Ji Miao Lai Mingqin Zhao Tianbao Ren 《Journal of heterocyclic chemistry》2019,56(9):2389-2397
To expand the library of pyrrole‐containing flavor precursors, two new flavor precursors—methyl N‐benzyl‐2‐methyl‐5‐formylpyrrole‐3‐carboxylate (NBMF) and methyl N‐butyl‐2‐methyl‐5‐formylpyrrole‐3‐carboxylate (NUMF)—were synthesized by cyclization, oxidation, and alkylation reactions. Thermogravimetry (TG), differential scanning calorimeter, and pyrolysis–gas chromatography/mass spectrometry were utilized to analyze the thermal degradation behavior and thermal degradation products of NBMF and NUMF. The TG‐DTG curve indicated that the maximum mass loss rates of NBMF and NUMF appear at 310 and 268°C, respectively. The largest peaks of NBMF and NUMF showed by the differential scanning calorimeter curve were 315 and 274°C, respectively. Pyrolysis–gas chromatography/mass spectrometry detected small molecule fragrance compounds appeared during thermal degradation, such as 2‐methylpyrrole, 1‐methylpyrrole‐2‐carboxylic acid methyl ester, limonene, and methyl formate. Finally, the thermal degradation mechanism of NBMF and NUMF was discussed, which provided a theoretical basis for their application in tobacco flavoring additives. 相似文献
85.
Lan-Lan Zhang Dr. Wen-Ke Miao Dr. Li-Jun Ren Yu-Kun Yan Dr. Yue Lin Prof. Wei Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(58):13396-13401
Organic polymers and inorganic clusters belong to two different disciplines and have completely different properties and structures. When a cluster is attached to the backbone of a polymer as a pendant, the resultant hybrid polymers (polyclusters) exhibit unique behaviours totally different from those of conventional polymers owing to the nanoscale size of the cluster and its particular interactions. Herein, the aggregation of a poly(polyoxometalate)—a polynorbornene backbone with inorganic polyoxometalate cluster pendants—upon addition of a non-solvent to its dilute solution is reported. A three-dimensional network of tangled and snake-like nanothreads was observed. Direct visualisation of individual nanoscale clusters enabled identification of single chains within the nanothreads. These observations suggest that during the process of aggregation, the hybrid polymer forms curved or extended chains as a consequence of an armouring effect in which the collapsed cluster pendants wrap around the backbone. The collapse occurs because they become less soluble in the solvent/non-solvent mixture. The extended chains then become entwined and form nanoropes consisting of multiple chains wound around each other. This study provides a deeper understanding of the nature of polyclusters and should also prove useful for their future development and application. 相似文献
86.
A star edge coloring of a graph is a proper edge coloring such that every connected 2-colored subgraph is a path with at most 3 edges. Deng et al. and Bezegová et al. independently show that the star chromatic index of a tree with maximum degree is at most , which is tight. In this paper, we study the list star edge coloring of -degenerate graphs. Let be the list star chromatic index of : the minimum such that for every -list assignment for the edges, has a star edge coloring from . By introducing a stronger coloring, we show with a very concise proof that the upper bound on the star chromatic index of trees also holds for list star chromatic index of trees, i.e. for any tree with maximum degree . And then by applying some orientation technique we present two upper bounds for list star chromatic index of -degenerate graphs. 相似文献
87.
Hongming He Qian‐Qian Zhu Chuanqi Zhang Ying Yan Jing Yuan Jing Chen Cheng‐Peng Li Miao Du 《化学:亚洲杂志》2019,14(7):917-917
88.
Dr. Longyu Li Qianming Lin Miao Tang Dr. Andrew J. E. Duncan Prof. Dr. Chenfeng Ke 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(46):10768-10781
The rapid development of additive manufacturing techniques, also known as three-dimensional (3D) printing, is driving innovations in polymer chemistry, materials science, and engineering. Among current 3D printing techniques, direct ink writing (DIW) employs viscoelastic materials as inks, which are capable of constructing sophisticated 3D architectures at ambient conditions. In this perspective, polymer designs that meet the rheological requirements for direct ink writing are outlined and successful examples are summarized, which include the development of polymer micelles, co-assembled hydrogels, supramolecularly cross-linked systems, polymer liquids with microcrystalline domains, and hydrogels with dynamic covalent cross-links. Furthermore, advanced polymer designs that reinforce the mechanical properties of these 3D printing materials, as well as the integration of functional moieties to these materials are discussed to inspire new polymer designs for direct ink writing and broadly 3D printing. 相似文献
89.
Acta Mathematicae Applicatae Sinica, English Series - For a graph G = (V, E) without isolated vertex, a function f: E(G) → {−1, 1} is said to be a signed star dominating function of G... 相似文献
90.