全文获取类型
收费全文 | 23682篇 |
免费 | 734篇 |
国内免费 | 185篇 |
专业分类
化学 | 16724篇 |
晶体学 | 205篇 |
力学 | 698篇 |
综合类 | 1篇 |
数学 | 3457篇 |
物理学 | 3516篇 |
出版年
2022年 | 208篇 |
2021年 | 298篇 |
2020年 | 359篇 |
2019年 | 319篇 |
2018年 | 279篇 |
2017年 | 232篇 |
2016年 | 513篇 |
2015年 | 452篇 |
2014年 | 536篇 |
2013年 | 1150篇 |
2012年 | 1286篇 |
2011年 | 1600篇 |
2010年 | 801篇 |
2009年 | 671篇 |
2008年 | 1320篇 |
2007年 | 1364篇 |
2006年 | 1432篇 |
2005年 | 1346篇 |
2004年 | 1198篇 |
2003年 | 1049篇 |
2002年 | 950篇 |
2001年 | 323篇 |
2000年 | 277篇 |
1999年 | 229篇 |
1998年 | 253篇 |
1997年 | 271篇 |
1996年 | 350篇 |
1995年 | 239篇 |
1994年 | 248篇 |
1993年 | 210篇 |
1992年 | 196篇 |
1991年 | 185篇 |
1990年 | 157篇 |
1989年 | 137篇 |
1988年 | 184篇 |
1987年 | 165篇 |
1986年 | 140篇 |
1985年 | 275篇 |
1984年 | 272篇 |
1983年 | 189篇 |
1982年 | 291篇 |
1981年 | 246篇 |
1980年 | 246篇 |
1979年 | 232篇 |
1978年 | 230篇 |
1977年 | 209篇 |
1976年 | 204篇 |
1975年 | 170篇 |
1974年 | 183篇 |
1973年 | 169篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Yuwei Wang Jia-Jun Yan Shengnan Hu Prof. David James Young Prof. Hong-Xi Li Prof. Zhi-Gang Ren 《化学:亚洲杂志》2021,16(18):2681-2686
A photoluminescent bimetallic cluster [Ag10Cu6(bdppthi)2(C≡CPh)12(MeOH)2(H2O)](ClO4)4 ( 1 , bdppthi=N,N’-bis(diphenylphosphanylmethyl)-tetrahydroimidazole} was synthesized from the PNNP type ligand bdppthi generated in-situ. Upon excitation at 365 nm, 1 exhibited strong phosphorescent emission at 630 nm, which was selectively quenched by NH3 in air or water. The sensing of NH3 was rapid and recoverable, with detection limits of 53 ppm (v/v) in N2 and 21 μmol/L (0.36 ppm, w/w) for NH3 ⋅ H2O in water. Cluster 1 could potentially serve as a bifunctional chemical sensor for the efficient detection of ammonia in waste-gas and waste-water. 相似文献
2.
3.
Control over Nanostructures and Associated Mesomorphic Properties of Doped Self‐Assembled Triarylamine Liquid Crystals 下载免费PDF全文
Dr. Yuya Domoto Dr. Eric Busseron Prof. Dr. Mounir Maaloum Dr. Emilie Moulin Prof. Dr. Nicolas Giuseppone 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(5):1938-1948
We have synthesized a series of triarylamine‐cored molecules equipped with an adjacent amide moiety and dendritic peripheral tails in a variety of modes. We show by 1H NMR and UV/Vis spectroscopy that their supramolecular self‐assembly can be promoted in solution upon light stimulation and radical initiation. In addition, we have probed their molecular arrangements and mesomorphic properties in the bulk by integrated studies on their film state by using differential scanning calorimetry (DSC), variable‐temperature polarizing optical microscopy (VT‐POM), variable‐temperature X‐ray diffraction (VT‐XRD), and atomic force microscopy (AFM). Differences in the number and the disposition of the peripheral tails significantly affect their mesomorphic properties associated with their lamellar‐ or columnar‐packed nanostructures, which are based on segregated stacks of the triphenylamine cores and the lipophilic/lipophobic periphery. Such structural tuning is of interest for implementation of these soft self‐assemblies as electroactive materials from solution to mesophases. 相似文献
4.
5.
6.
7.
Foundations of Chemistry - 相似文献
8.
Mara K. Kuenen James A. Mullin Rachel A. Letteri 《Journal of polymer science. Part A, Polymer chemistry》2021,59(19):2212-2221
With a vast, synthetically accessible compositional space and highly tunable hydrolysis rates, poly(β-amino ester)s (PBAEs) are an attractive degradable polymer platform. Leveraging PBAEs in a wide range of applications hinges on the ability to program degradation, which, thus far, has been frustrated by multiple confounding phenomena contributing to the degradation of these charged polyesters. Basic conditions accelerate hydrolysis, yet reduce solubility, limiting water access to amines and esters. Further, the high buffering capacity of PBAEs can render buffers ineffective at controlling solution pH. To unify understanding of PBAE degradation and solution properties, this study examines PBAE hydrolysis as a function of pH and buffer concentration as well as polymer hydrophobicity. At low buffer concentrations, the PBAE amines and the acid produced during hydrolysis control solution pH. Meanwhile, at high buffer concentrations that afford relatively constant pH, hydrolysis rate increases with pH, despite the reduced PBAE solubility. Increasing the hydrophobic content of PBAEs eventually hinders the capacity of the polymer to accept protons from solution, limiting the pH increase and slowing hydrolysis. These studies showcase the role of buffering on the pH-dependent degradation and solution properties of PBAEs, providing guidance for programming degradation in applications ranging from drug delivery to thermosets. 相似文献
9.
10.
Brian R. Holder Colleen A. McNaney David Luchetti Eric Schaeffer Dieter M. Drexler 《Biomedical chromatography : BMC》2015,29(9):1375-1379
Acetyl‐l ‐carnitine (ALCAR) is a potential biomarker for the modulation of brain neurotransmitter activity, but is also present in cerebrospinal fluid (CSF). Recent studies have utilized hydrophilic interaction liquid chromatography–tandem mass spectrometry (HILIC‐MS/MS) based assays to detect and quantify ALCAR within biofluids such as urine, plasma and serum, using various sample pretreatment procedures. In order to address the need to quantify ALCAR in CSF on a high‐throughput scale, a new and simple HILIC‐MS/MS assay has been successfully developed and validated. For rapid analysis, CSF sample pretreatment was performed via ‘dilute and shoot’ directly onto an advanced HILIC column prior to MS/MS detection. This newly developed HILIC‐MS/MS assay shows good recoveries of ALCAR without the need for chemical derivatization and multistep sample extraction procedures. The employment of this assay is suitable for the high‐throughput bioanalysis and quantification of ALCAR within the CSF of various animal models and human clinical studies. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献