全文获取类型
收费全文 | 5809篇 |
免费 | 580篇 |
国内免费 | 393篇 |
专业分类
化学 | 2394篇 |
晶体学 | 35篇 |
力学 | 898篇 |
综合类 | 4篇 |
数学 | 1128篇 |
物理学 | 2323篇 |
出版年
2024年 | 5篇 |
2023年 | 219篇 |
2022年 | 193篇 |
2021年 | 236篇 |
2020年 | 301篇 |
2019年 | 164篇 |
2018年 | 212篇 |
2017年 | 288篇 |
2016年 | 223篇 |
2015年 | 286篇 |
2014年 | 364篇 |
2013年 | 429篇 |
2012年 | 448篇 |
2011年 | 467篇 |
2010年 | 401篇 |
2009年 | 418篇 |
2008年 | 413篇 |
2007年 | 321篇 |
2006年 | 297篇 |
2005年 | 194篇 |
2004年 | 130篇 |
2003年 | 117篇 |
2002年 | 119篇 |
2001年 | 125篇 |
2000年 | 56篇 |
1999年 | 92篇 |
1998年 | 61篇 |
1997年 | 40篇 |
1996年 | 5篇 |
1995年 | 6篇 |
1994年 | 13篇 |
1993年 | 22篇 |
1992年 | 21篇 |
1991年 | 16篇 |
1990年 | 13篇 |
1989年 | 11篇 |
1988年 | 10篇 |
1987年 | 3篇 |
1986年 | 9篇 |
1985年 | 8篇 |
1984年 | 4篇 |
1983年 | 8篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1979年 | 3篇 |
1971年 | 7篇 |
排序方式: 共有6782条查询结果,搜索用时 46 毫秒
81.
Dr. Shuang Zhang Dr. Behafarid Ghalandari Dr. Aiting Wang Dr. Sijie Li Dr. Youming Chen Dr. Qingwen Wang Dr. Lai Jiang Prof. Xianting Ding 《Angewandte Chemie (International ed. in English)》2023,62(45):e202309806
Mass spectrometry has emerged as a mainstream technique for label-free proteomics. However, proteomic coverage for trace samples is constrained by adsorption loss during repeated elution at sample pretreatment. Here, we demonstrated superparamagnetic composite nanoparticles functionalized with molecular glues (MGs) to enrich proteins in trace human biofluid. We showed high protein binding (>95 %) and recovery (≈90 %) rates by anchor-nanoparticles. We further proposed a Streamlined Workflow based on Anchor-nanoparticles for Proteomics (SWAP) method that enabled unbiased protein capture, protein digestion and pure peptides elution in one single tube. We demonstrated SWAP to quantify over 2500 protein groups with 100 HEK 293T cells. We adopted SWAP to profile proteomics with trace aqueous humor samples from cataract (n=15) and wet age-related macular degeneration (n=8) patients, and quantified ≈1400 proteins from 5 μL aqueous humor. SWAP simplifies sample preparation steps, minimizes adsorption loss and improves protein coverage for label-free proteomics with previous trace samples. 相似文献
82.
Longbin Li Xiannong Tang Senhe Huang Dr. Chenbao Lu Prof. Dirk Lützenkirchen-Hecht Prof. Kai Yuan Prof. Xiaodong Zhuang Prof. Yiwang Chen 《Angewandte Chemie (International ed. in English)》2023,62(22):e202301642
Iron phthalocyanine-based polymers (PFePc) are attractive noble-metal-free candidates for catalyzing oxygen reduction reaction (ORR). However, the low site-exposure degree and poor electrical conductivity of bulk PFePc restricted their practical applications. Herein, laminar PFePc nanosheets covalently and longitudinally linked to graphene (3D-G-PFePc) was prepared. Such structural engineering qualifies 3D-G-PFePc with high site utilization and rapid mass transfer. Thence, 3D-G-PFePc demonstrates efficient ORR performance with a high specific activity of 69.31 μA cm−2, a high mass activity of 81.88 A g−1, and a high turnover frequency of 0.93 e s−1 site−1 at 0.90 V vs. reversible hydrogen electrode in O2-saturated 0.1 M KOH, outperforming the lamellar PFePc wrapped graphene counterpart. Systematic electrochemical analyses integrating variable-frequency square wave voltammetry and in situ scanning electrochemical microscopy further underline the rapid kinetics of 3D-G-PFePc towards ORR. 相似文献
83.
Jiashen Zhou Lin Zhang Yiran Wang Wenyan Song Yuzhou Huang Yajuan Mu Werner Schmitz Shu-Yu Zhang Houwen Lin Hong-Zhuan Chen Fei Ye Liang Zhang 《Angewandte Chemie (International ed. in English)》2023,62(46):e202313109
The short-chain dehydrogenase/reductase (SDR) superfamily members acyl-ACP reductases FabG and FabI are indispensable core enzymatic modules and catalytic orientation controllers in type-II fatty acid biosynthesis. Herein, we report their distinct substrate allosteric recognition and enantioselective reduction mechanisms. FabG achieves allosteric regulation of ACP and NADPH through ACP binding across two adjacent FabG monomers, while FabI follows an irreversible compulsory order of substrate binding in that NADH binding must precede that of ACP on a discrete FabI monomer. Moreover, FabG and FabI utilize a backdoor residue Phe187 or a “rheostat” α8 helix for acyl chain length selection, and their corresponding triad residues Ser142 or Tyr145 recognize the keto- or enoyl-acyl substrates, respectively, facilitating initiation of nucleophilic attack by NAD(P)H. The other two triad residues (Tyr and Lys) mediate subsequent proton transfer and (R)-3-hydroxyacyl- or saturated acyl-ACP production. 相似文献
84.
Yicong Luo Yuqi Ma Guanlin Li Xiaohong Huo Wanbin Zhang 《Angewandte Chemie (International ed. in English)》2023,62(47):e202313838
Fluorinated amino acids and related peptides/proteins have been found widespread applications in pharmaceutical and agricultural compounds. However, strategies for introducing a C−F bond into amino acids in an enantioselective manner are still limited and no such asymmetric catalysis strategy has been reported. Herein, we have successfully developed a Pd/Cu/Li ternary system for stereodivergent synthesis of chiral fluorinated amino acids. This method involves a sequential desymmetrization of geminal difluoromethylenes and allylic substitution with amino acid Schiff bases via Pd/Li and Pd/Cu dual activation, respectively. A series of non-natural amino acids bearing a chiral allylic/benzylic fluorine motif are easily synthesized in high yields with excellent regio-, diastereo-, and enantioselectivities (up to >20 : 1 dr and >99 % ee). A density functional theory (DFT) study revealed the F−Cu interaction of the allylic substrate and the Cu catalyst significantly influence the stereoselectivity. 相似文献
85.
Dr. Yu Nie Dr. Qianjia Yuan Prof. Dr. Wanbin Zhang 《Chemical record (New York, N.Y.)》2023,23(10):e202381001
The design and synthesis of chiral ligands plays an important role in asymmetric catalytic reactions. Over the past decades, various types of chiral phosphine-oxazolines (PHOX ligands) have been developed and have greatly advanced the field of asymmetric catalysis. Novel chiral PHOX ligand with an axis-unfixed biphenyl backbone, developed by our group, have shown interesting coordination behavior and excellent chiral inducing ability in various transition-metal-catalyzed asymmetric reactions. This personal account focuses on our developed axis-unfixed biphenylphosphine-oxazoline ligand (BiphPHOX), including an overview of its design and applications, which will provide inspiration for the exploration of novel ligands and related reactions. 相似文献
86.
Vinay Naithani Soumia Cheddah Kaige Yang Zihang Xia Weiwei Wang Yan Wang Chao Yan 《Journal of separation science》2023,46(10):2200711
An open tubular capillary electrochromatography column covalently bonded with polystyrene sulfonate was prepared via in situ polymerization using functionalized Azo-initiator 4,4′-Azobis(4-cyanopentanoyl chloride). Scanning electron, fluorescence, and atomic force microscopy techniques showed the formation of a relatively rough layer of polymer. In addition, –CN and C = O stretching vibrations from infrared spectroscopy proved the successful immobilization of the azo-initiator through covalent bonding and X-ray photoelectron spectroscopy confirmed the elemental composition of the formed polymer layer. The prepared column was found to be appropriate for small and medium-sized molecules separation. Compared to bare fused silica capillary column higher selectivity and resolution were obtained for the separation of alkaloids, sulfonamides, and peptides as a result of the electrostatic and pi-pi stacking interactions between the small organic molecules and the coated column without compromising the electroosmotic flow mobility. Separation efficiency was also increased compared to the bare capillary for the separation of alkaloids (about 1.5 times). Moreover, intraday, inter-day, intra-batch, and inter-batch relative standard deviation values of retention time and peak area of peptides were within 2% and 10%, respectively, indicating good repeatability of the column preparation procedure. The developed method for the covalent bonding of polymers through a functionalized azo-initiator could represent a promising stable method for the preparation of an open tubular column. 相似文献
87.
构建了一种基于框架核酸的高通量生物检测芯片.利用超微量移液自动化平台,将包含框架核酸探针的液滴按照预设命令固定至生物芯片微阵列上,在探针捕获核酸靶标后利用集成的基因芯片扫描仪对芯片进行成像,通过分析荧光强度定量化分析靶标浓度.结果表明,此框架核酸芯片能够实现框架核酸探针的高通量制备, 24 h即可制备具有15万个点的微阵列,且点间距离的相对偏差W≤10%、荧光强度的变异系数CV=3.30%,具有较高的稳定性,远高于国家标准.此外,该芯片具备高灵敏度、可寻址的高通量生物分析能力,对核酸靶标的检测限可达100 pmol/L.随着多种探针技术的发展,生物检测微阵列技术在高通量生物分析领域展示出巨大的潜力. 相似文献
88.
Nanocomposites comprising flexible polymers and high dielectric constant inorganic nanoparticles are considered to be one of the promising candidates for electrostatic capacitor dielectrics.However,the effect of interfacial property on electrical ene rgy storage of dielectric polymer nanocomposites is still not clear.Herein,the role of the polarity of the interfacial region is investigated.For this purpose,three polymers with different polarity,polymethyl methacrylate(PMMA),polyglycidyl methacrylate,and polymethylsulfonyl ethyl methacrylate(PMSEMA) are attached onto BaTi03(BT) na noparticle surface via surface-initiated reversible addition-fragmentation chain transfer polymerization.It is found that the polarity of shell polymers shows an apparent effect on the dielectric and energy storage of dielectric polymer nanocomposites.For example,PMSEMA@BT(shell polymer possesses the highest polarity)increases dielectric loss and decreases the breakdown strength of the nanocomposites,leading to lower ene rgy storage capability.However,PMMA@BT(shell polymer possesses the lowest polarity) can induce higher breakdown strength of the nanocomposites.As a result,the PMMA@BT nanocomposite exhibits the highest electrical energy sto rage capability among the three nanocomposites.This re search provides new insight into the design of core-shell nanofillers for dielectric energy storage applications. 相似文献
89.
《中国化学快报》2021,32(11):3416-3420
Tracking the movement of droplets in digital microfluidics is essential to improve its control stability and obtain dynamic information for its applications such as point-of-care testing, environment monitoring and chemical synthesis. Herein, an intelligent, accurate and fast droplet tracking method based on machine vision is developed for applications of digital microfluidics. To continuously recognize the transparent droplets in real-time and avoid the interferes from background patterns or inhomogeneous illumination, we introduced the correlation filter tracker, enabling online learning of the multi-features of the droplets in Fourier domain. Results show the proposed droplet tracking method could accurately locate the droplets. We also demonstrated the capacity of the proposed method for estimation of the droplet velocity as faster as 20 mm/s, and its application in online monitoring the Griess reaction for both colorimetric assay of nitrite and study of reaction kinetics. 相似文献
90.
Wei Yang Hao-Guo Yue Dong Zhao Hui Yan Kang-Li Cao Jin-Sheng Zhao Qing Zhang 《高分子科学》2021,39(2):147-153
Direct arylation methods have been used to polymerize thienylmethylene oxindoles(TEIs) and 3,3-bis[[(2-ethylhexyl)oxy]methyl]-3,4-dihydro-2 H-thieno-[3,4-b][1,4]dioxepin(ProDOT) for new donor-acceptor conjugated polymers. The polymers exhibited blue hues in neutralstate with distinct color-to-transmissive reversible electrochromic switching under applied potentials from 0 V to +1.5 V, and showed high coloration efficiencies(436-438 cm~2·C~(-1)) in near-infrared regions with high switching speeds around 1-2 s under ambient conditions. 相似文献