全文获取类型
收费全文 | 995篇 |
免费 | 265篇 |
国内免费 | 63篇 |
专业分类
化学 | 610篇 |
晶体学 | 3篇 |
力学 | 29篇 |
综合类 | 5篇 |
数学 | 14篇 |
物理学 | 662篇 |
出版年
2024年 | 1篇 |
2023年 | 13篇 |
2022年 | 36篇 |
2021年 | 33篇 |
2020年 | 40篇 |
2019年 | 24篇 |
2018年 | 27篇 |
2017年 | 32篇 |
2016年 | 67篇 |
2015年 | 77篇 |
2014年 | 75篇 |
2013年 | 88篇 |
2012年 | 87篇 |
2011年 | 80篇 |
2010年 | 52篇 |
2009年 | 63篇 |
2008年 | 66篇 |
2007年 | 83篇 |
2006年 | 59篇 |
2005年 | 45篇 |
2004年 | 43篇 |
2003年 | 38篇 |
2002年 | 26篇 |
2001年 | 27篇 |
2000年 | 21篇 |
1999年 | 16篇 |
1998年 | 16篇 |
1997年 | 19篇 |
1996年 | 14篇 |
1995年 | 4篇 |
1994年 | 12篇 |
1993年 | 11篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1990年 | 7篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有1323条查询结果,搜索用时 9 毫秒
21.
Chitosan/Ce(IV) redox polymerization‐based amplification for detection of DNA point mutation 下载免费PDF全文
Yanjun Cui Tianwei Tan Jing Yang 《Journal of polymer science. Part A, Polymer chemistry》2016,54(13):1929-1937
Polymerization‐based signal amplification, a technique developed for use in rapid diagnostic tests, hinges on the ability to localize initiators as a function of interfacial binding events. We report here a new DNA detection method in which polymer growth in redox‐polymerization is used as a means to amplify detection signals. The introduction of biotin‐labeled chitosan (biotin‐CS) with highly dense amino groups into the polymerization amplification as macromolecular reducing agent, beneficially simplifies amplification operation, as well as, provides a large amount of initiation points to improve the sensitivity of detection. DNA hybridization, SA and biotin binding reactions led to the attachment of CS on a solid surface where specific DNA sequences were located. With the addition of the mixture containing monomer AM, crosslinker PEGDA and oxidant CAN onto the CS location, the growth of polymer films was triggered to render the corresponding spots readily distinguishable to the naked eye. Direct visualization of 0.21 fmol target DNA molecules of interest was demonstrated. Non‐small cell lung cancer p53 sequence was further selected as a proof‐of‐principle to detect DNA point mutation. The proposed method exhibited an efficient amplification performance for molecule detection, and paved a new way for visual diagnosis of biomolecules. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1929–1937 相似文献
22.
Cheng Wang Yuxin Leng Chuang Li Baozhen Zhao Zhizhan Xu 《Optics & Laser Technology》2010,42(4):657-661
A decentered grating stretcher for chirped pulse amplification systems is analyzed with oblique meridional ray tracing. Several formulae and conclusions are developed to design and optimize the stretcher. On basis of an analytical phase expression with an explicit significance, the expressions of the second-, third- and approximate fourth-order phases at the central wavelength are presented with only independent variables. These simplify the parameter design for this kind of stretcher and the phase compensation design of the whole amplifier system, which has been demonstrated with a practical example. 相似文献
23.
24.
25.
A novel strategy for selective collection and detection of breast cancer cells (MCF-7) based on aptamer–cell interaction was developed. Mucin 1 protein (MUC1) aptamer (Apt1) was covalently conjugated to magnetic beads to capture MCF-7 cell through affinity interaction between Apt1 and MUC1 protein that overexpressed on the surface of MCF-7 cells. Meanwhile, a nano-bio-probe was constructed by coupling of nucleolin aptamer AS1411 (Apt2) to CdTe quantum dots (QDs) which were homogeneously coated on the surfaces of monodispersed silica nanoparticles (SiO2 NPs). The nano-bio-probe displayed similar optical and electrochemical performances to free CdTe QDs, and remained high affinity to nucleolin overexpressed cells through the interaction between AS1411 and nucleolin protein. Photoluminescence (PL) and square-wave voltammetric (SWV) assays were used to quantitatively detect MCF-7 cells. Improved selectivity was obtained by using these two aptamers together as recognition elements simultaneously, compared to using any single aptamer. Based on the signal amplification of QDs coated silica nanoparticles (QDs/SiO2), the detection sensitivity was enhanced and a detection limit of 201 and 85 cells mL−1 by PL and SWV method were achieved, respectively. The proposed strategy could be extended to detect other cells, and showed potential applications in cell imaging and drug delivery. 相似文献
26.
We report herein an exonuclease-assisted aptamer-based target recycling amplification strategy for sensitive and selective chemiluminescence (CL) determination of adenosine. This aptasensor is based on target-induced release of aptamers from capture probes immobilized on the 96-well plate surface, and thus leading to a decreased hybridization with gold nanoparticle-functionalized reporter sequences followed by a CL signal. The introduction of exonuclease III catalyzes the stepwise removal of mononucleotides from 3′-hydroxyl termini of duplex DNAs of aptamers, liberating the adenosine. Therefore, a single copy of target adenosine can lead to the release and digestion of numerous aptamer strands from the 96-well plates and ultimately an enhanced sensitivity is achieved. Experimental results revealed that the exonuclease-assisted recycling strategy enabled the monitoring of adenosine with wide working ranges and low detection limits (LOD: 0.5 nM). This new CL strategy might create a novel technology for the detection of various targets and could find wide applications in the environmental and biomedical fields. 相似文献
27.
28.
Precise characterization method of antibody‐conjugated magnetic nanoparticles for pathogen detection using stuffer‐free multiplex ligation‐dependent probe amplification 下载免费PDF全文
Boram Chung Gi Won Shin Woong Choi Jinmyoung Joo Sangmin Jeon Gyoo Yeol Jung 《Electrophoresis》2014,35(23):3283-3289
Antibody‐conjugated magnetic nanoparticles (Ab‐MNPs) have potential in pathogen detection because they allow target cells to be easily separated from complex sample matrices. However, the sensitivity and specificity of pathogen capture by Ab‐MNPs generally vary according to the types of MNPs, antibodies, and sample matrices, as well as preparation methods, including immobilization. Therefore, achieving a reproducible analysis utilizing Ab‐MNPs as a pathogen detection method requires accurate characterization of Ab‐MNP capture ability and standardization of all handling processes. In this study, we used high‐resolution CE‐single strand conformational polymorphism coupled with a stuffer‐free multiplex ligation‐dependent probe amplification system to characterize Ab‐MNPs. The capture ability of Ab‐MNPs targeting Salmonella enteritidis and nine pathogens, including S. enteritidis, was analyzed in phosphate buffer and milk. The effect of storage conditions on the stability of Ab‐MNPs was also assessed. The results showed that the stuffer‐free multiplex ligation‐dependent probe amplification system has the potential to serve as a standard characterization method for Ab‐MNPs. Moreover, the precise characterization of Ab‐MNPs facilitated robust pathogen detection in various applications. 相似文献
29.
Rapid and sensitive detection of lower respiratory tract infections by stuffer‐free multiplex ligation‐dependent probe amplification 下载免费PDF全文
Boram Chung Gi Won Shin Chan Kwon Park Woong Choi Yeun‐Jun Chung Hyung Kyu Yoon Gyoo Yeol Jung 《Electrophoresis》2014,35(4):511-514
Lower respiratory tract infection is one of the most common infectious diseases. However, conventional methods for detecting infectious pathogens are time‐consuming, and generally have a limited impact on early therapeutic decisions. We previously reported a rapid and sensitive method for detecting such pathogens using stuffer‐free multiplex ligation‐dependent probe amplification coupled with high‐resolution CE‐SSCP. In this study, we report an application of this method to the detection of respiratory pathogens. As originally configured, this method was capable of simultaneously detecting seven bacterial species responsible for lower respiratory tract infections, but its detection limit and assay time were insufficient to provide useful information for early therapeutic decisions. To improve sensitivity and shorten assay time, we added a target‐specific preamplification step, improving the detection limit from 50 pg of genomic DNA to 500 fg. We further decreased time requirements by optimizing the hybridization step, enabling the entire assay to be completed within 7 h while maintaining the same detection limit. Taken together, these improvements enable the rapid detection of infectious doses of pathogens (i.e. a few dozen cells), establishing the strong potential of the refined method, particularly for aiding early treatment decisions. 相似文献
30.
Construction of a portable sample preparation device with a magnetic poly(methacrylic acid‐co‐ethylene dimethacrylate) monolith as the extraction medium and its application in the enrichment of UV filters in water samples 下载免费PDF全文
Jing Li Li Xu Qiong‐Wei Yu Zhi‐Guo Shi Ting Zhang Yan Liu 《Journal of separation science》2014,37(19):2732-2737
A portable sample preparation device with a magnetic polymer monolith as the extraction medium was constructed. The monolith was synthesized by polymerizing methacrylic acid and ethylene dimethacrylate around a cylindrical magnet. In this way, the monolith with a magnetic core could be readily attached to the extraction device by magnetism. The constructed device was evaluated for the enrichment of UV filters in water samples, followed by high‐performance liquid chromatographic analysis. The extraction efficiency for the targets was satisfactory with no matrix interference. Good linearities were obtained for the UV filters with the correlation coefficients >0.9986. The limits of detection and quantification for the UV filters were 0.3–0.8 and 1.0–2.4 ng/mL, respectively. The recoveries of the UV filters from the spiked water samples at the concentration of 100 ng/mL were 95.3–101.7%, with relative standard deviations <10%. Accordingly, the proposed portable device was demonstrated to be suitable for on‐site simultaneous sampling, purification, and preconcentration within a single step. 相似文献