全文获取类型
收费全文 | 1653篇 |
免费 | 108篇 |
国内免费 | 11篇 |
专业分类
化学 | 1355篇 |
晶体学 | 17篇 |
力学 | 39篇 |
数学 | 164篇 |
物理学 | 197篇 |
出版年
2024年 | 3篇 |
2023年 | 5篇 |
2022年 | 49篇 |
2021年 | 53篇 |
2020年 | 51篇 |
2019年 | 92篇 |
2018年 | 48篇 |
2017年 | 34篇 |
2016年 | 87篇 |
2015年 | 56篇 |
2014年 | 68篇 |
2013年 | 148篇 |
2012年 | 133篇 |
2011年 | 120篇 |
2010年 | 70篇 |
2009年 | 51篇 |
2008年 | 79篇 |
2007年 | 70篇 |
2006年 | 77篇 |
2005年 | 72篇 |
2004年 | 60篇 |
2003年 | 44篇 |
2002年 | 60篇 |
2001年 | 19篇 |
2000年 | 20篇 |
1999年 | 11篇 |
1998年 | 5篇 |
1997年 | 8篇 |
1996年 | 11篇 |
1995年 | 13篇 |
1994年 | 8篇 |
1993年 | 6篇 |
1992年 | 13篇 |
1991年 | 7篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1988年 | 5篇 |
1987年 | 10篇 |
1986年 | 7篇 |
1985年 | 10篇 |
1984年 | 10篇 |
1983年 | 6篇 |
1982年 | 12篇 |
1981年 | 3篇 |
1979年 | 5篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1973年 | 6篇 |
1960年 | 2篇 |
1959年 | 2篇 |
排序方式: 共有1772条查询结果,搜索用时 390 毫秒
161.
Nadia Morcos Manar Omran Hala Ghanem Mahmoud Elahdal Nashwa Kamel Elbatoul Attia 《Photochemistry and photobiology》2015,91(4):942-951
One inescapable feature of life on the earth is exposure to ionizing radiation. The thyroid gland is one of the most sensitive organs to gamma‐radiation and endocrine disrupters. Low‐level laser therapy (LLLT) has been used to stimulate tissue repair, and reduce inflammation. The aim of this study was to gauge the value of using Helium–Neon laser to repair the damaged tissues of thyroid gland after gamma‐irradiation. Albino rats were used in this study (144 rats), divided into control, gamma, laser, and gamma plus laser‐irradiated groups, each group was divided into six subgroups according to time of treatment (total six sessions). Rats were irradiated once with gamma radiation (6 Gy), and an external dose of laser (Wavelength 632.8 nm, 12 mW, CW, Illuminated area 5.73 cm2, 2.1 mW cm?2, 120 s, 1.4 J, 0.252 J cm?2) twice weekly localized on thyroid region of the neck, for a total of six sessions. Animals were sacrificed after each session. Analysis included thyroid function, oxidative stress markers, liver function and blood picture. Results revealed improvement in thyroid function, liver function and antioxidant levels, and the blood cells count after LLLT. 相似文献
162.
Exploiting the 1,2,3‐Triazole Moiety to Generate Carbazole Molecular Architectures through Click Approach
下载免费PDF全文
![点击此处可从《Journal of heterocyclic chemistry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Mohamed A. Ameen Kamal M. El‐Shaieb Asmaa H. Mohamed Fathy F. Abdel‐Latif 《Journal of heterocyclic chemistry》2015,52(6):1718-1722
Reaction of 3,6‐dichlorocarbazole with propargyl bromide in the presence of a basic medium gave an N‐propargylated carbazole. The latter compound was converted into molecular architectures containing 1,2,3‐triazole moiety through Cu(I)‐catalyzed 1,3‐cycloaddition reaction with different azides. Similarly, 2‐azidomethyl benzothiazole was cliched with N‐Boc‐protected N´‐propargyl glutamate to give the biomolecule 2‐triazolylmethyl product. 相似文献
163.
Genetic diversity and haplotype structure of 21 Y‐STRs,including nine noncore loci,in South Tunisian Population: Forensic relevance
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)
Faten Makki‐Rmida Arwa Kammoun Nadia Mahfoudh Adnene Ayadi Abdullah Ahmed Gibriel Bakhta Mallek Leila Maalej Zouheir Hammami Samir Maatoug Hafedh Makni Saber Masmoudi 《Electrophoresis》2015,36(23):2908-2913
Y chromosome STRs (Y‐STRs) are being used frequently in forensic laboratories. Previous studies of Y‐STR polymorphisms in different groups of the Tunisian population identified low levels of diversity and discrimination capacity (DC) using various commercial marker sets. This definitely limits the use of such systems for Y‐STRs genotyping in Tunisia. In our investigation on South Tunisia, 200 unrelated males were typed for the 12 conventional Y‐STRs included in the PowerPlex® Y System. Additional set of nine noncore Y‐STRs including DYS446, DYS456, DYS458, DYS388, DYS444, DYS445, DYS449, DYS710, and DYS464 markers were genotyped and evaluated for their potential in improving DC. Allele frequency, gene diversity, haplotype diversity (HD), and DC calculation revealed that DYS464 was the most diverse marker followed by DYS710 and DYS449 markers. The standard panel of 12 Y‐STRs (DC = 80.5%) and the nine markers were combined to obtain DC of 99%. Among the 198 different haplotypes observed, 196 haplotypes were unique (HD = 99.999). Out of the nine noncore set, six Y‐STRs (DYS458, DYS456, DYS449, DYS710, DYS444, and DYS464) had the greatest impact on enhancing DC. Our data provided putative Y‐STRs combination to be used for genetic and forensic applications. 相似文献
164.
Tailoring of carboxyl‐decorated magnetic latex particles using seeded emulsion polymerization
下载免费PDF全文
![点击此处可从《先进技术聚合物》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Talha Jamshaid Mohamed M. Eissa Quentin Lelong Anne Bonhommé Geraldine Augsti Nadia Zine Abdelhamid Errachid Abdelhamid Elaissari 《先进技术聚合物》2017,28(9):1088-1096
In this research, submicron and carboxyl‐functionalized magnetic latex particles were elaborated by using seeded emulsion polymerization technique in presence of oil‐in‐water (o/w) magnetic emulsion as seed. The polymerization conditions were optimized in order to get well‐defined latex particles with magnetic core and polymer shell bearing carboxylic (–COOH) functionality. Starting from (o/w) magnetic emulsion as seed, synthesis process was performed by copolymerization of styrene (St) monomer with the cross‐linker divinylbenzene (DVB) in presence of 4,4′‐azobis(4‐cyanopentanoic acid) (ACPA) as a carboxyl‐bearing initiator. The prepared magnetic latex particles were first characterized in terms of particle size, chemical composition, morphology, magnetic properties, magnetic content, and colloidal stability using various techniques, e.g. particle size analyzer using dynamic light scattering (DLS) technique, Fourier transform infrared, transmission electron microscopy, vibrating sample magnetometer, thermogravimetric analysis, and zeta potential measurements as a function of pH of the dispersion media, respectively. The prepared magnetic latex particles were then used as second seed for further functionalization with methacrylic acid (MAA) in order to enhance carboxylic groups on the magnetic particle's surface. The results showed that final magnetic latex particles possessed spherical morphology with core‐shell structure and enriched carboxylic acid functionality. More importantly, they exhibited superparamagnetism with high magnetic content (58.42 wt%) and high colloidal stability, which considered as the main requirements for their application in the biomedical diagnostic domains. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
165.
JPC – Journal of Planar Chromatography – Modern TLC - A simple and robust thin-layer chromatography (TLC) method has been developed and validated for the simultaneous quantitative... 相似文献
166.
Michaël Gabay Nadia Brauner Vladimir Kotov 《4OR: A Quarterly Journal of Operations Research》2017,15(2):183-199
We use game theory techniques to automatically compute improved lower bounds on the competitive ratio for the bin stretching problem. Using these techniques, we improve the best lower bound for this problem to 19/14. We explain the technique and show that it can be generalized to compute lower bounds for any online or semi-online packing or scheduling problem. 相似文献
167.
Aziz N. Abdel 《Fluid Dynamics》1993,28(5):736-738
The phenomenon of thermal relaxation of the gas bubbles in a fluid behind a shock front is analyzed. The approach to solving the problem of heat transfer between a gas bubble and a fluid developed by the author is used to obtain a solution describing the initial stage of bubble collapse behind the shock front.Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 5, pp. 187–189, September–October, 1993. 相似文献
168.
Synthesis,Reactions, Characterization and Biological Evaluation of 2,3′‐Bipyridine Derivatives (III)
下载免费PDF全文
![点击此处可从《Journal of heterocyclic chemistry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Fawzy A. Attaby Azza M. Abdel‐Fattah Labeeb M. Shaif Mohamed M. Elsayed 《Journal of heterocyclic chemistry》2014,51(4):927-936
1‐Pyridin‐3‐yl‐3‐(2‐thienyl of 2‐furyl)prop‐2‐en‐1‐ones 1a , 1b reacted with 2‐cyanoethanethioamide 2 to afford the corresponding 4‐(thiophen‐2‐yl or furan‐2‐yl)‐6‐sulfanyl‐2,3′‐bipyridine‐5‐carbonitriles 3a , 3b . The synthetic potentiality of compounds 3a , 3b were investigated in the present study via their reactions with several active halogen containing compounds 4a , 4b , 4c , 4d , 4e , 4f , 4g , 4h , 5 , 5a , 5b . Our aim here is the synthesis of 4‐(2‐thienyl or 2‐furyl)‐6‐pyridin‐3‐ylthieno[2,3‐b]pyridin‐3‐amines 6a , 6b , 6c , 6d , 6e , 6g , 6h , 6i , 6j , 6k , 6l , 6m , 6n ,via 6‐(alkyl‐thio)‐4‐(2‐thienyl or 2‐furyl)‐2,3′‐bipyridine‐5‐carbonitriles 5a , 5b , 5c , 5d , 5e , 5i , 5j , 5k , 5l , 5m . The structures of all newly synthesized heterocyclic compounds were elucidated by considering the data of IR, 1H‐NMR, mass spectra, as well as that of elemental analyses. Anti‐cancer, anti‐Alzheimer, and anti‐COX‐2 activities were investigated for all the newly synthesized heterocyclic compounds. 相似文献
169.
Synthesis of Novel Modified Guanidines: Reaction of Dicyandiamide with Amino Acids,Amides, and Amines in Aqueous Medium
下载免费PDF全文
![点击此处可从《Journal of heterocyclic chemistry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ahmed M. Soliman Shaaban K. Mohamed Mahmoud. Abd El Aleem. Ali. Ali. El‐Remaily H. Abdel‐Ghany 《Journal of heterocyclic chemistry》2014,51(5):1322-1326
Reaction of dicyandiamide with series of amino acids afforded guanidinyl pyrazolones 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , respectively. Although reaction of dicyandiamide with urea, acetamide, bezamide, allantion, p‐aminobenzoic acid, sulphanilic acid, and adenine gave biguanides 20 , 21 , 22 , 23 , 24 , 25 , 26 , respectively. All compounds have been characterized on the basis of IR and 1H‐NMR. 相似文献
170.
Ahmed M. M. Soliman Mahmoud. Abd El‐Aleem. Ali. Ali. El‐Remaily Adel. A. Sultan Hossam. Abdel‐Ghany 《Journal of heterocyclic chemistry》2014,51(5):1476-1481
5‐Amino‐3‐anilino‐1H‐pyrazole‐4‐carbonitrile 1 was alkylated with various halo reagents under phase transfer conditions to give the corresponding imidazopyrazole derivatives 2a , 2b , 2c , 3 , 4 , 5 , 6 . Pyrazolo[1,5‐a] pyrimidine derivatives 11 , 12 , 13 , 14 were prepared by treating compound 1 with different dicarbonyl reagents, namely, diethymalonate, ethyl 3‐oxo‐3‐phenylpropanoate, pentane‐2,4‐dione or ethyl 3‐oxobutanoate. 相似文献