全文获取类型
收费全文 | 26041篇 |
免费 | 5880篇 |
国内免费 | 2614篇 |
专业分类
化学 | 12379篇 |
晶体学 | 404篇 |
力学 | 1476篇 |
综合类 | 235篇 |
数学 | 2245篇 |
物理学 | 17796篇 |
出版年
2024年 | 30篇 |
2023年 | 271篇 |
2022年 | 549篇 |
2021年 | 783篇 |
2020年 | 1040篇 |
2019年 | 769篇 |
2018年 | 720篇 |
2017年 | 875篇 |
2016年 | 1096篇 |
2015年 | 1066篇 |
2014年 | 1452篇 |
2013年 | 2228篇 |
2012年 | 1666篇 |
2011年 | 1824篇 |
2010年 | 1542篇 |
2009年 | 1665篇 |
2008年 | 1658篇 |
2007年 | 1744篇 |
2006年 | 1758篇 |
2005年 | 1449篇 |
2004年 | 1397篇 |
2003年 | 1241篇 |
2002年 | 1079篇 |
2001年 | 925篇 |
2000年 | 886篇 |
1999年 | 705篇 |
1998年 | 660篇 |
1997年 | 578篇 |
1996年 | 451篇 |
1995年 | 377篇 |
1994年 | 336篇 |
1993年 | 286篇 |
1992年 | 228篇 |
1991年 | 175篇 |
1990年 | 176篇 |
1989年 | 156篇 |
1988年 | 122篇 |
1987年 | 89篇 |
1986年 | 103篇 |
1985年 | 72篇 |
1984年 | 64篇 |
1983年 | 20篇 |
1982年 | 39篇 |
1981年 | 44篇 |
1980年 | 35篇 |
1979年 | 18篇 |
1978年 | 24篇 |
1977年 | 11篇 |
1975年 | 11篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Multipod structures of lamellae‐forming diblock copolymers in three‐dimensional confinement spaces: Experimental observation and computer simulation 下载免费PDF全文
Takeshi Higuchi Marco Pinna Andrei V. Zvelindovsky Hiroshi Jinnai Hiroshi Yabu 《Journal of Polymer Science.Polymer Physics》2016,54(17):1702-1709
The three‐dimensional (3D) confinement effect on the microphase‐separated structure of a diblock copolymer was investigated both experimentally and computationally. Block copolymer nanoparticles were prepared by adding a poor solvent into a block copolymer solution and subsequently evaporating the good solvent. The 3D structures of the nanoparticles were quantitatively determined with transmission electron microtomography (TEMT). TEMT observations revealed that various complex structures, including tennis‐ball, mushroom‐like, and multipod structures, were formed in the 3D confinement. Detailed structural analysis, showed that one block of the diblock copolymer slightly prefers to segregate into the particle surface compared with the other block. The observed structures were further elaborated using cell dynamics computer simulation. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1702–1709 相似文献
992.
993.
Rachael Fay Prof. Dr. Jason P. Holland 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(15):4893-4897
Photochemistry provides a wide range of alternative reagents that hold potential for use in bimolecular functionalisation of proteins. Here, we report the synthesis and characterisation of metal ion binding chelates derivatised with disubstituted tetrazoles for the photoradiochemical labelling of monoclonal antibodies (mAbs). The photophysical properties of tetrazoles featuring extended aromatic systems and auxochromic substituents to tune excitation toward longer wavelengths (365 and 395 nm) were studied. Two photoactivatable chelates based on desferrioxamine B (DFO) and the aza-macrocycle NODAGA were functionalised with a tetrazole and developed for protein labelling with 89Zr, 64Cu and 68Ga radionuclides. DFO-tetrazole ( 1 ) was assessed by direct conjugation to formulated trastuzumab and subsequent radiolabelling with 89Zr. Radiochemical studies and cellular-based binding assays demonstrated that the radiotracer remained stable in vitro retained high immunoreactivity. Positron emission tomography (PET) imaging and biodistribution studies were used to measure the tumour specific uptake and pharmacokinetic profile in mice bearing SK-OV-3 xenografts. Experiments demonstrate that tetrazole-based photochemistry is a viable approach for the light-induced synthesis of PET radiotracers. 相似文献
994.
This article proposes a parsimonious alternative approach for modeling the stochastic dynamics of mortality rates. Instead of the commonly used factor-based decomposition framework, we consider modeling mortality improvements using a random field specification with a given causal structure. Such a class of models introduces dependencies among adjacent cohorts aiming at capturing, among others, the cohort effects and cross generations correlations. It also describes the conditional heteroskedasticity of mortality. The proposed model is a generalization of the now widely used AR-ARCH models for random processes. For such a class of models, we propose an estimation procedure for the parameters. Formally, we use the quasi-maximum likelihood estimator (QMLE) and show its statistical consistency and the asymptotic normality of the estimated parameters. The framework being general, we investigate and illustrate a simple variant, called the three-level memory model, in order to fully understand and assess the effectiveness of the approach for modeling mortality dynamics. 相似文献
995.
《Analytical letters》2012,45(11):2143-2156
Abstract A laser ablated plasma created by an ArF excimer laser of wavelength of 193 nm, laser power of 150-200 mJ, repetition rate of 1 Hz, and zinc, copper, iron and nickel targets was studied. Quantitative emission studies are reported that are both space and time resolved. The space results of the laser ablated plasma suggest a confined plasma with a gaussian type distribution of atoms and ions. The time resolved studies show a maximum emission signal occurring at approximately 20 μs with a lifetime of less than 100 μs. 相似文献
996.
Simulation of local ion transport in lamellar block copolymer electrolytes based on electron micrographs 下载免费PDF全文
Mahati Chintapalli Kenneth Higa X. Chelsea Chen Venkat Srinivasan Nitash P. Balsara 《Journal of Polymer Science.Polymer Physics》2017,55(3):266-274
A method is presented to relate local morphology and ionic conductivity in a solid, lamellar block copolymer electrolyte for lithium batteries, by simulating conductivity through transmission electron micrographs. The electrolyte consists of polystyrene‐block‐poly(ethylene oxide) mixed with lithium bis(trifluoromethanesulfonyl) imide salt (SEO/LiTFSI), where the polystyrene phase is structural phase and the poly(ethylene oxide)/LiTFSI phase is ionically conductive. The electric potential distribution is simulated in binarized micrographs by solving the Laplace equation with constant potential boundary conditions. A morphology factor, f, is reported for each image by calculating the effective conductivity relative to a homogenous conductor. Images from two samples are examined, one annealed with large lamellar grains and one unannealed with small grains. The average value of f is 0.45 ± 0.04 for the annealed sample, and 0.37 ± 0.03 for the unannealed sample, both close to the value predicted by effective medium theory, 1/2. Simulated conductivities are compared to published experimental conductivities. The value of fUnannealed/fAnnealed is 0.82 for simulations and 6.2 for experiments. Simulation results correspond well to predictions by effective medium theory but do not explain the experimental measurements. Observation of nanoscale morphology over length scales greater than the size of the micrographs (~1 μm) may be required to explain the experimental results. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 266–274 相似文献
997.
Dr. Lina M. Aguirre-Díaz Marcelo Echeverri Dr. Katherine Paredes-Gil Dr. Natalia Snejko Dr. Berta Gómez-Lor Prof. Dr. Enrique Gutiérrez-Puebla Prof. Dr. M. Ángeles Monge 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(16):5298-5306
Three new cadmium-based coordination polymers, denoted [Cd(hfipbb)(4,4’-bipy)] ( CdPF-1 ), [Cd(hfipbb)(2,2’-bipy)] ( CdPF-2 ), and [Cd(hfipbb)(1,10-phen)] ( CdPF-3 ), have been hydrothermally synthesized by using the well-known V-shaped organic linker 4,4’-(hexafluoroisopropylidene)bis(benzoic acid) (H2hfipbb), together with different nitrogenated auxiliary linkers. Considering the d10 configuration of the transition metal selected, the luminescent properties for these CdPF-n materials were explored, finding that materials CdPF-2 and CdPF-3 act as excellent sensors in the detection of explosive nitro aromatic compounds. The photoluminescence properties of CdPF-2 and CdPF-3 revealed that significant and sensitive fluorescence quenching was observed toward NP (nitrophenol) for CdPF-2 and PA (picric acid) for CdPF-3 in MeOH suspensions. 相似文献
998.
Angana Goswami 《光谱学快报》2013,46(5):253-260
Bioluminescence emissions from fireflies have been well-studied for over a century. From the apparent features of the emitted light, conclusions have been drawn and hypotheses put forward on the characteristics of the highly efficient light emitting system. The basic emitter oxyluciferin, being chemically unstable, is difficult to study in isolation and, therefore, its analogs have been prepared and analyzed. In this letter, the lifetimes of the excited-state emitter oxyluciferin are measured, and an inference is drawn on the chemiluminescence reaction in vivo. The light from the Indian species of firefly Luciola praeusta contains three color-sectors: green, yellow, and red, and hence three optical filters are used to study time-resolved emissions from these sectors at different temperatures. All the three color-sectors are observed to be temperature sensitive in the time domain. An exponential variation of lifetime with temperature is observed for the emissions in these three regions. 相似文献
999.
1000.
Dr. Stefanie Neubauer Dr. Florian Rechenmacher Dr. Ambros J. Beer Dr. Flavio Curnis Karolin Pohle Dr. Calogero D'Alessandria Prof. Dr. Hans‐Jürgen Wester Prof. Dr. Ute Reuning Prof. Dr. Angelo Corti Prof. Dr. Markus Schwaiger Prof. Dr. Horst Kessler 《Angewandte Chemie (International ed. in English)》2013,52(44):11666-11666