全文获取类型
收费全文 | 1633篇 |
免费 | 342篇 |
国内免费 | 153篇 |
专业分类
化学 | 2035篇 |
晶体学 | 3篇 |
力学 | 1篇 |
物理学 | 89篇 |
出版年
2023年 | 30篇 |
2022年 | 43篇 |
2021年 | 90篇 |
2020年 | 149篇 |
2019年 | 105篇 |
2018年 | 108篇 |
2017年 | 87篇 |
2016年 | 126篇 |
2015年 | 123篇 |
2014年 | 148篇 |
2013年 | 127篇 |
2012年 | 131篇 |
2011年 | 121篇 |
2010年 | 123篇 |
2009年 | 113篇 |
2008年 | 113篇 |
2007年 | 69篇 |
2006年 | 76篇 |
2005年 | 57篇 |
2004年 | 56篇 |
2003年 | 38篇 |
2002年 | 38篇 |
2001年 | 13篇 |
2000年 | 4篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 12篇 |
1994年 | 10篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1987年 | 1篇 |
排序方式: 共有2128条查询结果,搜索用时 15 毫秒
1.
Dr. Wenyan Hao Yuchen Sha Dr. Yi Deng Yi Luo Li Zeng Shan Tang Dr. Yue Weng Prof. Dr. Chien-Wei Chiang Prof. Dr. Aiwen Lei 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(19):4931-4934
An in situ generated oxidation species of nickel quinolinylpropioamide intermediate was produced. Characterization by X-ray absorption near edge structure (XANES) and EPR provides complementary insights into this oxidized nickel species. With aliphatic amides and isocyanides as substrates, a nickel-catalyzed facile synthesis of structurally diverse five-membered lactams could be achieved. 相似文献
2.
Kozo Matsumoto Tatsuya Miyano Yojiro Kotake 《Journal of polymer science. Part A, Polymer chemistry》2019,57(24):2420-2425
A polycarbosilane having lactose‐derived structures was synthesized, and its thermal property, cytotoxicity, chemical crosslinking, and protein adsorption properties were investigated. The polycarbosilane (PSB‐Lac) was prepared by a thiol‐ene reaction between precursor poly(1‐(3‐butenyl)‐1‐methylsilacyclubane) (PSB) and heptaacetyl lactose that carried a thiol group at the anomeric position, and the successive deprotection of the acetyl groups. The lactose introduction efficiency determined by 1H NMR measurement was 75%. TGA and DSC revealed that the polymer had a 5 wt% decomposition temperature of 260 °C and glass transition temperature (Tg) of 84 °C, which indicated that PSB‐Lac was a thermally stable polymer. PSB‐Lac had no significant cytotoxicity, which was evaluated by human liver cancer cell line HepG2 cultivation on the polystyrene dishes coated with the polymer. Urethane‐crosslinked PSB‐Lac films were prepared by casting solutions of PSB‐Lac and hexamethylene diisocyanate and heating at 120 °C after evaporation of the solvent. The crosslinked PSB‐Lac showed higher adsorption of bovine serum albumin than the similarly crosslinked polycarbosilane that had a glucose structure (PSB‐Glc). © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2420–2425 相似文献
3.
Dr. Martin Pichette Drapeau Prof. Dr. Lukas J. Gooßen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(52):18654-18677
The selective transformation of C?H bonds is one of the most desirable approaches to creating complexity from simple building blocks. Several directing groups are efficient in controlling the regioselectivity of catalytic C?H bond functionalizations. Among them, carboxylic acids are particularly advantageous, since they are widely available in great structural diversity and at low cost. The carboxylate directing groups can be tracelessly cleaved or may serve as the anchor point for further functionalization through decarboxylative couplings. This Minireview summarizes the substantial progress made in the last few years in the development of reactions in which carboxylate groups direct C?H bond functionalizations with formation of C?C, C?O, C?N, or C?halogen bonds at specific positions. It is divided into sections on C?C, C?O, C?N, and C?halogen bond formation, each of which is subdivided by reactions and product classes. Particular emphasis is placed on methods that enable multiple derivatizations by combining carboxylate‐directed C?H functionalization with decarboxylative couplings. 相似文献
4.
Facile synthesis of thermosensitive functional polyaspartamide derivatives by click chemistry 下载免费PDF全文
Guangyan Zhang Yunti Zhang Yanfeng Chu Yingying Ma Renxi Zhuo Xulin Jiang 《Journal of polymer science. Part A, Polymer chemistry》2015,53(10):1296-1303
Biodegradable and thermosensitive polyaspartamide derivatives containing pendant azide groups P(Asp‐Az)X‐HPAs were synthesized from poly(l ‐succinimide) via the ring‐opening reaction with 2‐azidoethylamine (Az) and 5‐hydroxypentylamine (HPA). Then hydrophobic phenethyl (PEA) and imidazole (IMZ) moieties were introduced successfully with very high reaction efficiency above 90% to the side chains of P(Asp‐Az)X‐HPA by click reaction to obtain thermoresponsive polyaspartamide derivatives containing pendant aromatic rings P(Asp‐Az)X‐HPA‐PEAs and the thermo/pH‐responsive polyaspartamide derivatives containing pendant imidazole rings P(Asp‐Az)X‐HPA‐IMZs, respectively. The thermoresponsive behaviors of P(Asp‐Az)X‐HPA‐PEAs and P(Asp‐Az)X‐HPA‐IMZs were confirmed by dynamic light scattering (DLS) and transmittance measurements, and the cloud point can be tuned by designed amounts of azide groups and can be further adjusted by the grafting molar percentage of hydrophobic phenethyl or imidazole moieties to the side chains of P(Asp‐Az)X‐HPA via click chemistry. The pH‐responsive behavior of P(Asp‐Az)X‐HPA‐IMZs can also be tuned. These results indicate that the obtained polyaspartamide‐based functional polymers can be further functionalized with hydrophilic long PEG chain and/or targeted moieties via click chemistry for drug delivery. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1296–1303 相似文献
5.
6.
Intramolecular trans‐Dicarbofunctionalization of Alkynes by a Formal anti‐Carbopalladation/Stille Cascade 下载免费PDF全文
Bastian Milde Andreas Reding Finn J. Geffers Prof. Dr. Peter G. Jones Prof. Dr. Daniel B. Werz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(41):14544-14547
An intramolecular Pd‐catalyzed trans‐dicarbofunctionalization of internal alkynes using aryl bromides and aryl stannanes is presented. Tetrasubstituted double bonds embedded in an oligocyclic ring system are obtained in a regio‐ and diastereoselective fashion. The transformation features a broad substrate scope and functional‐group tolerance. 相似文献
7.
In‐Depth Understanding of the Chemical Properties of Rarely Explored Carbide Cluster Metallofullerenes: A Case Study of Sc2C2@C3v(8)‐C82 that Reveals a General Rule 下载免费PDF全文
Wenting Cai Muqing Chen Lipiao Bao Dr. Yunpeng Xie Prof. Dr. Takeshi Akasaka Prof. Dr. Xing Lu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(8):3449-3454
The chemical properties of carbide‐cluster metallofullerenes (CCMFs) remain largely unexplored, although several new members of CCMFs have been discovered recently. Herein, we report the reaction between Sc2C2@C3v(8)‐C82, which is viewed as a prototypical CCMF because of its high abundance, and 3‐triphenylmethyl‐5‐oxazolidinone ( 1 ) to afford the corresponding pyrrolidino derivative Sc2C2@C3v(8)‐C82(CH2)2NTrt ( 2 ; Trt=triphenylmethyl). Single‐crystal X‐ray crystallography studies of 2 revealed that the reaction takes place at a [6,6]‐bond junction, which is directly over the encapsulated C2 unit and is far from either of the two scandium atoms. On the basis of theoretical calculations and by considering previously reports, we have found that a hexagonal carbon ring on the cage of Sc2C2@C3v(8)‐C82 is highly reactive toward different reagents due to the overlap of high p‐orbital axis vector (POAV) angles and large LUMO coefficients. We propose that this highly concentrated area of reactivity is generated by the encapsulation of the Sc2C2 cluster because this region is absent from the empty fullerene C3v(8)‐C82. Moreover, the absorption and electrochemical results confirm that derivative 2 is more stable than pristine Sc2C2@C3v(8)‐C82, thus illuminating its potential applications. 相似文献
8.
Facile synthesis of dopa‐functional polycarbonates via thiol‐Ene‐coupling chemistry towards self‐healing gels 下载免费PDF全文
Kristina Olofsson Michael Malkoch Anders Hult 《Journal of polymer science. Part A, Polymer chemistry》2016,54(15):2370-2378
Since extraction of the naturally occurring mussel‐foot proteins is expensive and time‐consuming, routes towards synthetic analogues are continuously being explored. Often, these methods involve several protection and deprotection steps, making the synthesis of synthetic analogues time‐consuming and expensive as well. Herein, we show that UV‐initiated thiol‐ene coupling between a thiol‐functional dopamine derivative and an allyl‐functional aliphatic polycarbonate can be used as a fast and facile route to dopa‐functional materials. Different thiol‐to‐allyl ratios and irradiation protocols were used and it was found that nearly 50% of the allyl groups could be functionalized with dopa within short reaction times, without the need of protecting the catechol. It is also demonstrated herein that the dopa‐functional polymers can be used to form self‐healing gels through complexation with Fe3+ ions at increased pH. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2370–2378 相似文献
9.
Xiao-Guang Yang Feng-Huan Du Jun-Jie Li Prof. Dr. Chi Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(27):e202200272
The development of convenient new methods for the synthesis of organic azides is highly desirable. Herein, we report a practical method for dehydroxyazidation of alcohols via an SN2 pathway involving PPh3 and trifunctional benziodazolone-based hypervalent azido-iodine(III) reagents, which function as an electrophilic center, an azido source, and a base. This mild, chemoselective method was used for late-stage azidation of structurally complex alcohols, as well as for a new synthetic route to the antiepileptic drug rufinamide. The reaction mechanism was also investigated both experimentally and computationally. 相似文献
10.