全文获取类型
收费全文 | 861篇 |
免费 | 25篇 |
国内免费 | 7篇 |
专业分类
化学 | 655篇 |
晶体学 | 5篇 |
力学 | 23篇 |
数学 | 64篇 |
物理学 | 146篇 |
出版年
2023年 | 5篇 |
2022年 | 10篇 |
2021年 | 17篇 |
2020年 | 15篇 |
2019年 | 7篇 |
2018年 | 9篇 |
2017年 | 14篇 |
2016年 | 35篇 |
2015年 | 18篇 |
2014年 | 20篇 |
2013年 | 38篇 |
2012年 | 59篇 |
2011年 | 73篇 |
2010年 | 34篇 |
2009年 | 32篇 |
2008年 | 61篇 |
2007年 | 62篇 |
2006年 | 61篇 |
2005年 | 49篇 |
2004年 | 34篇 |
2003年 | 29篇 |
2002年 | 29篇 |
2001年 | 11篇 |
2000年 | 15篇 |
1999年 | 9篇 |
1998年 | 15篇 |
1997年 | 11篇 |
1996年 | 7篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1984年 | 5篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1975年 | 9篇 |
1974年 | 4篇 |
1973年 | 5篇 |
1971年 | 4篇 |
1970年 | 2篇 |
1969年 | 4篇 |
1932年 | 3篇 |
1930年 | 2篇 |
排序方式: 共有893条查询结果,搜索用时 0 毫秒
31.
Analysis of non‐derivatised bacteriohopanepolyols by ultrahigh‐performance liquid chromatography/tandem mass spectrometry 下载免费PDF全文
32.
Philip J. Hammond C. Dennis Hall 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3):351-353
Abstract Cis-1-alkyl (or aryl)-2,5-dimethyl-3-phospholens isomerize to the trans-isomers in deuteriochloroform and the isomerization is probably due to small quantities of phosgene in the solvent. 相似文献
33.
34.
Structural and electrochemical properties of spray deposited molybdenum trioxide (α-MoO3) thin films
Khalate S. A. Kate R. S. Pathan H. M. Deokate R. J. 《Journal of Solid State Electrochemistry》2017,21(9):2737-2746
Journal of Solid State Electrochemistry - Nanostructured molybdenum trioxide (α-MoO3) thin films were deposited to investigate effect of substrate temperature on microstructural,... 相似文献
35.
Supaporn Kradtap Hartwell Alison Kehling Somchai Lapanantnoppakhun Kate Grudpan 《Analytical letters》2013,46(11):1640-1671
This review focuses on the developments of the various parts of instrumentation and the operation of low to medium pressure flow injection and sequential injection chromatography (FIC and SIC) systems. The report and discussion include solution delivery system, separation column, flow cell and detector, mobile phase management, and online sample pretreatment. Applications of FIC and SIC and their differences as compared to HPLC are also presented. 相似文献
36.
Tatiana A. Shmigol Samantha Hammond James B. Phillips James I. Bruce Alexander J. MacRobert Mikhail V. Malakhov Jon P. Golding 《Photochemistry and photobiology》2013,89(1):139-149
Phthalocyanine photosensitizers are effective in anticancer photodynamic therapy (PDT) but suffer from limited solubility, limited cellular uptake and limited selectivity for cancer cells. To improve these characteristics, we synthesized isopropylidene‐protected and partially deprotected tetra β‐glycosylated zinc (II) phthalocyanines and compared their uptake and accumulation kinetics, subcellular localization, in vitro photocytotoxicity and reactive oxygen species generation with those of disulfonated aluminum phthalocyanine. In MCF‐7 cancer cells, one of the compounds, zinc phthalocyanine {4}, demonstrated 10‐fold higher uptake, 5‐fold greater PDT‐induced cellular reactive oxygen species concentration and 2‐fold greater phototoxicity than equimolar (9 μm ) disulfonated aluminum phthalocyanine. Thus, isopropylidene‐protected β‐glycosylation of phthalocyanines provides a simple method of improving the efficacy of PDT. 相似文献
37.
Galina Karabanovich Jaroslav Roh Zdeňka Padělková Zdeněk Novák Kateřina Vávrová Alexandr Hrabálek 《Tetrahedron》2013
1-Substituted-5-alkylsulfanyl-1H-tetrazoles are well known class of organic substances with various applications in medicinal chemistry or photographic industry. Their selenium analogues, 1-substituted-5-alkylselanyl-1H-tetrazoles are, however, much less explored because of the lack of suitable methods for their preparation. In this work we investigated the synthesis of 1-alkyl/aryl-5-alkylselanyl-1H-tetrazoles from synthetically available alkyl/arylisoselenocyanates. One-pot reactions of arylisoselenocyanates with sodium azide and alkylating agent led to the target 5-alkylselanyl-1-aryl-1H-tetrazoles but also to interesting side products, namely N-alkyl-N-arylcyanamides and (Z)-Se-alkyl-N-cyano-N,N′-diarylisoselenoureas. Nevertheless, when alkylisoselenocyanates were utilized as the substrates, the reactions led exclusively to the formation of 1-alkyl-5-alkylselanyl-1H-tetrazoles in good yields. This simple one-pot procedure brings new possibilities for the preparation of variously substituted selenium compounds. It also opens the way to further investigations of selenium isosteres of the widely utilized 5-thiotetrazole moiety in biomedical applications. 相似文献
38.
Kateřina Černovská Bedřich Košata Vladimíra Novotná Milada Glogarová 《Liquid crystals》2013,40(9):987-996
Several series of new benzofused thieno[3,2‐b]furan‐ and thieno[3,2‐b]thiophene‐based derivatives have been synthesized and their mesomorphic properties investigated. All the studied compounds exhibit a SmC* phase with very wide temperature interval. Additionally, some types of the compounds show the cholesteric, SmA or blue phase. In the ferroelectric SmC* phase we evaluated physical properties of relevance for possible applications. 相似文献
39.
Chen X Zhang L Zhou K Davies E Sugden K Bennion I Hughes M Hine A 《Optics letters》2007,32(17):2541-2543
Using an optical biosensor based on a dual-peak long-period fiber grating, we have demonstrated the detection of interactions between biomolecules in real time. Silanization of the grating surface was successfully realized for the covalent immobilization of probe DNA, which was subsequently hybridized with the complementary target DNA sequence. It is interesting to note that the DNA biosensor was reusable after being stripped off the hybridized target DNA from the grating surface, demonstrating a function of multiple usability. 相似文献
40.
Antennal morphology, structure and sensilla distribution in Microplitis pallidipes (Hymenoptera: Braconidae) 总被引:2,自引:0,他引:2
Microplitis pallidipes (Hymenoptera: Braconidae) is an important larval parasitoid of noctuid larval pests. In this study, we describe the morphology, ultrastructure and distribution of sensilla on the antennae of both male and female adults using scanning electron microscopy; complemented with transmission electron microscopy. Observations determined that the antennae of M. pallidipes were threadlike and the flagella were composed of 16 sub-segments. Totally, there were six types of sensilla found on the antennae. They were identified as Sensilla trichodea, Sensilla chaetica, Sensilla basiconica type I, S. basiconica type II, Sensilla coeloconicum, and elongated Sensilla placodea, respectively. The S. trichodea were the most abundant sensilla and distributed over the entire antennae, while S. basiconica I and II, S. coeloconicum, and elongated S. placodea were limited to the flagellum. S. chaetica were found on the scape and pedicle in very low numbers. The S. basiconica II and elongated S. placodea walls were full of pores as evident in transmission electron micrographs. Though the shape and structure of antennae between male and female adults were not basically different, the length and width of the antennae on male wasps were significantly greater than that of females. Also, the number, size and density of S. placodea of the male were significantly greater than those of females. The morphology and structure of these sensilla were compared with that found in other braconid wasps. Their possible functions are discussed in light of previously published literature. 相似文献