全文获取类型
收费全文 | 25875篇 |
免费 | 4844篇 |
国内免费 | 3882篇 |
专业分类
化学 | 19225篇 |
晶体学 | 430篇 |
力学 | 1615篇 |
综合类 | 274篇 |
数学 | 2665篇 |
物理学 | 10392篇 |
出版年
2024年 | 66篇 |
2023年 | 513篇 |
2022年 | 1034篇 |
2021年 | 967篇 |
2020年 | 1159篇 |
2019年 | 1150篇 |
2018年 | 998篇 |
2017年 | 986篇 |
2016年 | 1325篇 |
2015年 | 1401篇 |
2014年 | 1616篇 |
2013年 | 2056篇 |
2012年 | 2547篇 |
2011年 | 2572篇 |
2010年 | 1789篇 |
2009年 | 1868篇 |
2008年 | 1906篇 |
2007年 | 1660篇 |
2006年 | 1573篇 |
2005年 | 1326篇 |
2004年 | 972篇 |
2003年 | 699篇 |
2002年 | 687篇 |
2001年 | 587篇 |
2000年 | 467篇 |
1999年 | 432篇 |
1998年 | 351篇 |
1997年 | 312篇 |
1996年 | 245篇 |
1995年 | 231篇 |
1994年 | 178篇 |
1993年 | 179篇 |
1992年 | 152篇 |
1991年 | 132篇 |
1990年 | 96篇 |
1989年 | 58篇 |
1988年 | 56篇 |
1987年 | 40篇 |
1986年 | 38篇 |
1985年 | 42篇 |
1984年 | 27篇 |
1983年 | 24篇 |
1982年 | 10篇 |
1981年 | 13篇 |
1980年 | 9篇 |
1979年 | 12篇 |
1975年 | 5篇 |
1971年 | 5篇 |
1965年 | 4篇 |
1957年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
921.
Yixuan Xie Chao Peng Yunyi Gao Xiaohong Liu Tianbo Liu Abraham Joy 《Journal of polymer science. Part A, Polymer chemistry》2017,55(23):3908-3917
Glycopolymers have been widely used to understand the interactions between carbohydrates and lectins, which facilitate the diagnosis and detection of disease and pathogens as well as the development of vaccines. While studies have been focused on the correlation of glycopolymer structure and their binding to lectins, graft‐type glycopolyesters are uncommon. Herein, we report the design and synthesis of mannose‐based graft polyesters by “grafting‐from” method and investigate their interactions with Concanavalin A (Con A). As confirmed by 1H NMR spectroscopy and sulfuric acid‐UV method, graft polyesters with different lengths of mannose graft were successfully synthesized. Our results from turbidimetry binding assay showed that graft polyesters with longer mannose graft exhibit higher initial binding rate (ki). Isothermal titration calorimetry measurements of these graft polyesters with Con A showed that polymers exhibit higher binding affinity (ka) with the number of side chain mannose. This study provides understanding of the interaction between Con A and mannose‐based graft polyesters, which can be employed for the development of glycopolymeric therapeutics. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3908–3917 相似文献
922.
This paper is intended mainly to present some generic uniqueness results for a class of vector Ky Fan inequalities. By employing
the methods of set-valued analysis, we prove that, in the sense of Baire category, most of the problems in a complete metric
space, consisting of vector Ky Fan inequalities satisfying some conditions, have unique solution and that every vector Ky
Fan inequality, possessing more than one solution, can be approached arbitrarily by a sequence of vector Ky Fan inequalities
each of which has a unique solution. Our discussions are under two different settings. One setting is related to vector Ky
Fan inequalities defined on a compact set; the other is related to vector Ky Fan inequalities defined on a noncompact set.
The corollaries of our results generalized the corresponding results in the literature. 相似文献
923.
Dr. Jiang Peng Jiakun Bai Xiumian Cao Jieting He Prof. Weiqing Xu Dr. Junhui Jia 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(64):16036-16042
Elastic organic single crystals with light-emitting and multi-faceted bending properties are extremely rare. They have potential application in optical materials and have attracted the extensive attention of researchers. In this paper, we reported a structurally simple barbituric derivative DBDT , which was easily crystallized and gained long needle-like crystals (centimeter-scale) in DCM/CH3OH (v/v=2/8). Upon applying or removing the mechanical force, both the (100) and (040) faces of the needle-like crystal showed reversible bending behaviour, showing the nature of multi-faceted bending. The average hardness (H) and elastic modulus (E) were 0.28±0.01 GPa and 4.56±0.03 GPa for the (040) plane, respectively. Through the analysis of the single crystal data, it could be seen that the van der waals (C−H⋅⋅⋅π and C−H⋅⋅⋅C), H-bond (C−H⋅⋅⋅O) and π⋅⋅⋅π interactions between molecules were responsible for the generation of the crystal elasticity. Interestingly, elastic crystals exhibited optical waveguide characteristics in straight or bent state. The optical loss coefficients measured at 627 nm were 0.7 dBmm−1 (straight state) and 0.9 dBmm−1 (bent state), while the optical loss coefficient (α) were 1.5 dBmm−1 (straight state) and 1.8 dBmm−1 (bent state) at 567 nm. Notably, the elastic organic molecular crystal based on barbituric derivative could be used as the candidate for flexible optical devices. 相似文献
924.
925.
926.
Pua Aileen Goh Rui Min Vivian Ee Kim-Huey Huang Yunle Liu Shao Quan Lassabliere Benjamin Yu Bin 《Chromatographia》2021,84(5):507-515
Chromatographia - The separation of isomers is one of the key issues in analysing complex natural matrices, thus commanding a higher separating power from the applied analytical system. In this... 相似文献
927.
Combined effect of modified zeolite 13X and β-nucleating agent on improving β-crystal content and toughening polypropylene random copolymer 总被引:1,自引:0,他引:1
Although addition of β-NUCLEATING agent directly into homo-polypropylene(PPH) is a useful method to improve β-CRYSTAL content and toughen PPH, polypropylene random copolymer(PPR) makes this method powerless due to its random structure and low crystallinity. In this study, the-nucleated PPR with high β-CRYSTAL content was prepared by a novel high effective β-NUCLEATING system which consists of-nucleation agent(TMB-5) and modified zeolite 13X(M13X). It was found that M13X and TMB-5 had a synergistic influence on improving β-CRYSTAL content and toughening PPR. The content of β-CRYSTAL in PPR/M13X/TMB-5 was significantly larger than the sum of that in PPR/M13X and PPR/TMB-5. Besides,fracture behavior, phase morphology and relaxation of matrix chain segments were also investigated. The results showed that M13X and TMB-5 improved the mobility of amorphous chain segments at low temperature and contributed to much energy dissipation. This work provides a powerful method to modify PPR. 相似文献
928.
929.
Dr. Bo Chen Cheng Fang Prof. Peng Liu Prof. Joseph M. Ready 《Angewandte Chemie (International ed. in English)》2017,56(30):8780-8784
We describe the synthetically useful enantioselective addition of Br−CX3 (X=Cl or Br) to terminal olefins to introduce a trihalomethyl group and generate optically active secondary bromides. Computational and experimental evidence supports an asymmetric atom-transfer radical addition (ATRA) mechanism in which the stereodetermining step involves outer-sphere bromine abstraction from a [(bisphosphine)RhIIBrCl] complex by a benzylic radical intermediate. This mechanism appears unprecedented in asymmetric catalysis. 相似文献
930.
Gold‐Catalyzed Tandem Cycloisomerization–Halogenation of Chiral Homopropargyl Sulfonamides
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Chao Shu Long Li Cang‐Hai Shen Peng‐Peng Ruan Chao‐Yue Liu Prof. Dr. Long‐Wu Ye 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(7):2282-2290
Two new gold‐catalyzed tandem cycloisomerization–halogenation reactions of chiral homopropargyl sulfonamides have been developed. Various enantioenriched 3,3‐diiodopyrrolidin‐2‐ols and 3‐fluoropyrrolidin‐2‐ols were obtained in moderate‐to‐good yields with excellent enantio‐ and diastereoselectivity. 相似文献