全文获取类型
收费全文 | 417篇 |
免费 | 31篇 |
国内免费 | 21篇 |
专业分类
化学 | 354篇 |
力学 | 3篇 |
综合类 | 31篇 |
数学 | 6篇 |
物理学 | 75篇 |
出版年
2023年 | 3篇 |
2022年 | 16篇 |
2021年 | 16篇 |
2020年 | 17篇 |
2019年 | 11篇 |
2018年 | 5篇 |
2017年 | 7篇 |
2016年 | 17篇 |
2015年 | 15篇 |
2014年 | 16篇 |
2013年 | 26篇 |
2012年 | 30篇 |
2011年 | 26篇 |
2010年 | 29篇 |
2009年 | 37篇 |
2008年 | 30篇 |
2007年 | 31篇 |
2006年 | 25篇 |
2005年 | 15篇 |
2004年 | 18篇 |
2003年 | 12篇 |
2002年 | 11篇 |
2001年 | 9篇 |
2000年 | 6篇 |
1999年 | 8篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
排序方式: 共有469条查询结果,搜索用时 31 毫秒
151.
郭松梅 《广东微量元素科学》2016,(8):68-70
全世界每年死于乙型肝炎病毒相关疾病的人数已达60万人,应用荧光定量PCR法检测能够提高乙肝病毒基因的检出率,正确掌握该技术方法能够更加有效地进行疾病诊断和预防工作。基于此,研究针对荧光定量PCR法检测乙肝病毒基因的方法进行探讨。 相似文献
152.
153.
Mannina L Sobolev AP Capitani D Iaffaldano N Rosato MP Ragni P Reale A Sorrentino E D'Amico I Coppola R 《Talanta》2008,77(1):433-444
The nuclear magnetic resonance (NMR) technique was used as analytical tool to determine the complete metabolic profiling of sea bass extracts: water-soluble metabolites belonging to different classes such as sugars, amino acids, dipeptides and organic acids as well as metabolites soluble in organic solvent such as lipids, sterols and fatty acids were identified. The metabolite profiling together with a suitable statistical analysis were used to discriminate between wild and cultured sea bass samples. Preliminary results show that discrimination between wild and cultured sea bass was obtained not only using fatty acid composition but also cholesterol and phosphatidylethanolamine and some water-soluble metabolites such as choline, trimethylamine oxide, glutamine, fumaric and malic acids. 相似文献
154.
Samadi-Maybodi A Darzi SK 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,70(5):1167-1172
Resolution of binary mixtures of vitamin B12, methylcobalamin and B12 coenzyme with minimum sample pre-treatment and without analyte separation has been successfully achieved by methods of partial least squares algorithm with one dependent variable (PLS1), orthogonal signal correction/partial least squares (OSC/PLS), principal component regression (PCR) and hybrid linear analysis (HLA). Data of analysis were obtained from UV-vis spectra. The UV-vis spectra of the vitamin B12, methylcobalamin and B12 coenzyme were recorded in the same spectral conditions. The method of central composite design was used in the ranges of 10-80mgL(-1) for vitamin B12 and methylcobalamin and 20-130mgL(-1) for B12 coenzyme. The models refinement procedure and validation were performed by cross-validation. The minimum root mean square error of prediction (RMSEP) was 2.26mgL(-1) for vitamin B12 with PLS1, 1.33mgL(-1) for methylcobalamin with OSC/PLS and 3.24mgL(-1) for B12 coenzyme with HLA techniques. Figures of merit such as selectivity, sensitivity, analytical sensitivity and LOD were determined for three compounds. The procedure was successfully applied to simultaneous determination of three compounds in synthetic mixtures and in a pharmaceutical formulation. 相似文献
155.
Vegetative insecticidal protein (Vip), a unique class of insecticidal protein, is now part of transgenic plants for conferring
resistance against lepidopteron pests. In order to address the imminent regulatory need for detection and labeling of vip3A carrying genetically modified (GM) products, we have developed a standard single PCR and a multiplex PCR assay. As far as
we are aware, this is the first report on PCR-based detection of a vip3A-type gene (vip-s) in transgenic cotton and tobacco. Our assay involves amplification of a 284-bp region of the vip-s gene. This assay can possibly detect as many as 20 natural wild-type isolates bearing a vip3A-like gene and two synthetic genes of vip3A in transgenic plants. The limit of detection as established by our assay for GM trait (vip-s) is 0.1%. Spiking with nontarget DNA originating from diverse plant sources had no inhibitory effect on vip-s detection. Since autoclaving of vip-s bearing GM leaf samples showed no deterioration/interference in detection efficacy, the assay seems to be suitable for processed
food products as well. The vip-s amplicon identity was reconfirmed by restriction endonuclease assay. The primer set for vip-s was equally effective in a multiplex PCR assay format (duplex, triplex and quadruplex), used in conjunction with the primer
sets for the npt-II selectable marker gene, Cauliflower mosaic virus 35S promoter and nopaline synthetase terminator, enabling concurrent detection of the transgene, regulatory sequences and
marker gene. Further, the entire transgene construct was amplified using the forward primer of the promoter and the reverse
primer of the terminator. The resultant amplicon served as a template for nested PCR to confirm the construct integrity. The
method is suitable for screening any vip3A-carrying GM plant and food. The availability of a reliable PCR assay method prior to commercial release of vip3A-based transgenic crops and food would facilitate rapid and efficient regulatory compliance.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
An application for an Indian patent (1891/DEL2006/17.08.07) comprising a substantive part of this study has been filed.
ITRC communication no. 2516. 相似文献
156.
《Arabian Journal of Chemistry》2023,16(4):104593
A multiplex polymerase chain reaction (PCR) detection method for the simultaneous detection of animal-derived components from deer, cow, sheep, pig and horse in edible meat was established, and a multiplex PCR detection kit for the rapid detection of animal-derived components was developed. According to the mitochondrial cytochrome b (Cyt b) gene of bovine species, sheep species, pig species and horse species and the mitochondrial cytochrome c oxidase subunit I (COX 1) gene of sika deer and red deer as the target gene sequences of primers, the specific primers of five different species were designed, the PCR system was optimized, and the multiplex PCR identification method of five animal-derived components was established. The minimum detection amount was determined by sensitivity test. The results showed that five meat specific amplification bands could be found at the same time in the same reaction system, including 173 bp fragment for venison, 148 bp for beef, 261 bp for pork, 100 bp for mutton and 424 bp for horse, indicating that the method is specific and stable. The minimum detection limit by this method was 1 ng/μL, showing a high sensitivity. According to the different sites in different areas of animal mitochondrial genes, a multiplex PCR detection method was established and a detection kit was developed, and the rapid, sensitive, stable and high-throughput detection of five animal-derived components and adulterated animal components in edible meat can be realized by using the kit. 相似文献
157.
Simultaneous determination of hydrazine (HZ) and thiosemicarbazide (TSC) by partial least squares (PLS) and principle component regression (PCR) was carried out based on kinetic data of novel potentiometry. The rate of chloride ion production in reaction of HZ and TSC with N‐chlorosuccinimide (NCS) was monitored by a chloride ion‐selective electrode. The experimental dada shows not only the good ability of ion‐selective electrodes (ISEs) as detectors for the direct determination of chloride ions but also for simultaneous kinetic‐potentiometric analysis using chemometrics methods. The methods are based on the difference observed in the production rate of chloride ions. The results show that simultaneous determination of HZ and TSC can be performed in their concentration ranges of 0.7‐20.0 and 0.5‐20.0 μg mL?1, respectively. The total relative standard error for applying PLS and PCR methods to 9 synthetic samples in the concentration ranges of 0.8‐10 μg mL?1 of TSC and 1.0‐12.0 μg mL?1 of HZ was 4.62 and 4.98, respectively. The effects of certain foreign ions upon the reaction rate were determined for the assessment of the selectivity of the method. Both methods (PLS and PCR) were validated using a set of synthetic sample mixtures and then applied for simultaneous determination of HZ and TSC in water samples. 相似文献
158.
Petr Michalek Simona Dostalova Hana Buchtelova Natalia Cernei Ludmila Krejcova David Hynek Vedran Milosavljevic Ana Maria Jimenez Jimenez Pavel Kopel Zbynek Heger Vojtech Adam 《Electrophoresis》2016,37(14):2025-2035
Annual epidemics of influenza cause death of hundreds of thousands people and they also have a significant economic impact. Hence, a need for fast and cheap influenza diagnostic method is arising. The conventional methods for an isolation of the viruses are time‐consuming and require expensive instrumentation as well as trained personnel. In this study, we modified the surface of nanomaghemite (γ‐Fe2O3) paramagnetic core with tetraethyl orthosilicate and (3‐aminopropyl)triethoxysilane and the resulting particles were utilized for the isolation of H7N7 influenza virions. Consequently, we designed γ‐Fe2O3 paramagnetic core modified with calcium tripolyphosphate which was employed for the isolation of viral nucleic acid after virion's lysis. Both of these procedures can be performed rapidly in less than 10 min and, in combination with the RT‐PCR, the whole influenza detection can be shortened to few hours. Moreover, the whole protocol could be easily automated and/or miniaturized, and thus can serve as a basis for use in a lab‐on‐a‐chip device. We assume that magnetic isolation is an exceptional procedure which can significantly accelerate the diagnostic possibilities of a broad spectrum of diseases. 相似文献
159.
Expansion of a SNaPshot assay to a 55‐SNP multiplex: Assay enhancements,validation, and power in forensic science
下载免费PDF全文
![点击此处可从《Electrophoresis》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Qian Wang Lihong Fu Xiaojing Zhang Xinyu Dai Mei Bai Guangping Fu Bin Cong Shujin Li 《Electrophoresis》2016,37(10):1310-1317
A previously developed multiplex assay with 44 individual identification SNPs was expanded to a 55plex assay. Fifty‐four highly informative SNPs and an amelogenin sex marker were amplified in one PCR reaction and then detected with two SNaPshot reactions using CE. PCR primers for four loci, 28 single‐base extension primers, and the reaction conditions were altered to improve the robustness of the method. A detailed approach for allele calling was developed to guide analysis of the electropherogram. One hundred and eighty unrelated individuals and 100 father‐child‐mother trios of the Han population in Hebei, China were analyzed. No mutation was found in the SNP loci. The combined mean match probability and cumulative probability of exclusion were 1.327 × 10?22 and 0.999932, respectively. Analysis of the 54 SNPs and 26 STRs (included in the AmpFLSTR Identifiler and Investigator HDplex kits) showed no significant linkage disequilibriums. Our research shows that the expanded SNP multiplex assay is an easily performed and valuable method to supplement STR analysis. 相似文献
160.