全文获取类型
收费全文 | 5252篇 |
免费 | 269篇 |
国内免费 | 24篇 |
专业分类
化学 | 4072篇 |
晶体学 | 49篇 |
力学 | 129篇 |
综合类 | 1篇 |
数学 | 344篇 |
物理学 | 950篇 |
出版年
2023年 | 24篇 |
2022年 | 58篇 |
2021年 | 117篇 |
2020年 | 104篇 |
2019年 | 132篇 |
2018年 | 63篇 |
2017年 | 68篇 |
2016年 | 167篇 |
2015年 | 164篇 |
2014年 | 205篇 |
2013年 | 342篇 |
2012年 | 415篇 |
2011年 | 501篇 |
2010年 | 315篇 |
2009年 | 235篇 |
2008年 | 379篇 |
2007年 | 297篇 |
2006年 | 280篇 |
2005年 | 287篇 |
2004年 | 233篇 |
2003年 | 169篇 |
2002年 | 207篇 |
2001年 | 108篇 |
2000年 | 105篇 |
1999年 | 69篇 |
1998年 | 49篇 |
1997年 | 28篇 |
1996年 | 42篇 |
1995年 | 34篇 |
1994年 | 32篇 |
1993年 | 29篇 |
1992年 | 16篇 |
1991年 | 24篇 |
1990年 | 25篇 |
1989年 | 19篇 |
1988年 | 18篇 |
1987年 | 8篇 |
1986年 | 9篇 |
1985年 | 21篇 |
1984年 | 9篇 |
1983年 | 12篇 |
1982年 | 7篇 |
1981年 | 14篇 |
1980年 | 9篇 |
1979年 | 11篇 |
1978年 | 8篇 |
1977年 | 12篇 |
1976年 | 10篇 |
1975年 | 6篇 |
1974年 | 7篇 |
排序方式: 共有5545条查询结果,搜索用时 468 毫秒
991.
A Pd(II)-catalyzed reaction engaging alkenyl β-keto esters is reported that leads to the formation of 1-naphthols and an unexpected generation of arylpalladium(II) species. Interception of the in situ generated arylpalladium(II) species in a Mizoroki-Heck reaction, together with additional mechanistic studies, provided strong evidence in support of the first aromatization-driven β-carbon elimination process. A single Pd catalyst served to promote a series of both C-C bond forming and cleavage events in an unprecedented manner. 相似文献
992.
Cyclo[m]pyridine[n]pyrroles: hybrid macrocycles that display expanded π-conjugation upon protonation
Zhang Z Lim JM Ishida M Roznyatovskiy VV Lynch VM Gong HY Yang X Kim D Sessler JL 《Journal of the American Chemical Society》2012,134(9):4076-4079
Novel hybrid cyclo[m]pyridine[n]pyrroles have been synthesized using Suzuki coupling. Their NMR and optical spectroscopic features and solid state structural parameters provide support for the proposal that these species are best described as locally aromatic compounds devoid of long-range intersubunit conjugation. However, an extension of the π-conjugation in the macrocycles can be realized through protonation, as inferred from optical spectroscopic and X-ray diffraction-based structural studies. 相似文献
993.
Highly luminescent InP/GaP/ZnS nanocrystals and their application to white light-emitting diodes 总被引:1,自引:0,他引:1
Kim S Kim T Kang M Kwak SK Yoo TW Park LS Yang I Hwang S Lee JE Kim SK Kim SW 《Journal of the American Chemical Society》2012,134(8):3804-3809
Highly stable and luminescent InP/GaP/ZnS QDs with a maximum quantum yield of 85% were synthesized by in situ method. The GaP shell rendered passivation of the surface and removed the traps. TCSPC data showed an evidence for the GaP shell. InP/GaP/ZnS QDs show better stability than InP/ZnS. We studied the optical properties of white QD-LEDs corresponding to various QD concentrations. Among various concentrations, the white QD-LEDs with 0.5 mL of QDs exhibited a luminous efficiency of 54.71 lm/W, Ra of 80.56, and CCT of 7864 K. 相似文献
994.
Baek S Kutchukian PS Verdine GL Huber R Holak TA Lee KW Popowicz GM 《Journal of the American Chemical Society》2012,134(1):103-106
Mdm2 is a major negative regulator of the tumor suppressor p53 protein, a protein that plays a crucial role in maintaining genome integrity. Inactivation of p53 is the most prevalent defect in human cancers. Inhibitors of the Mdm2-p53 interaction that restore the functional p53 constitute potential nongenotoxic anticancer agents with a novel mode of action. We present here a 2.0 ? resolution structure of the Mdm2 protein with a bound stapled p53 peptide. Such peptides, which are conformationally and proteolytically stabilized with all-hydrocarbon staples, are an emerging class of biologics that are capable of disrupting protein-protein interactions and thus have broad therapeutic potential. The structure represents the first crystal structure of an i, i + 7 stapled peptide bound to its target and reveals that rather than acting solely as a passive conformational brace, a staple can intimately interact with the surface of a protein and augment the binding interface. 相似文献
995.
996.
RK Yadav JO Baeg GH Oh NJ Park KJ Kong J Kim DW Hwang SK Biswas 《Journal of the American Chemical Society》2012,134(28):11455-11461
The photocatalyst-enzyme coupled system for artificial photosynthesis process is one of the most promising methods of solar energy conversion for the synthesis of organic chemicals or fuel. Here we report the synthesis of a novel graphene-based visible light active photocatalyst which covalently bonded the chromophore, such as multianthraquinone substituted porphyrin with the chemically converted graphene as a photocatalyst of the artificial photosynthesis system for an efficient photosynthetic production of formic acid from CO(2). The results not only show a benchmark example of the graphene-based material used as a photocatalyst in general artificial photosynthesis but also the benchmark example of the selective production system of solar chemicals/solar fuel directly from CO(2). 相似文献
997.
Lee MH Kim JY Han JH Bhuniya S Sessler JL Kang C Kim JS 《Journal of the American Chemical Society》2012,134(30):12668-12674
Presented here is a multicomponent synthetic strategy that allows for the direct, fluorescence-based monitoring of the targeted cellular uptake and release of a conjugated therapeutic agent. Specifically, we report here the design, synthesis, spectroscopic characterization, and preliminary in vitro biological evaluation of a RGD peptide-appended naphthalimide pro-CPT (compound 1). Compound 1 is a multifunctional molecule composed of a disulfide bond as a cleavable linker, a naphthalimide moiety as a fluorescent reporter, an RGD cyclic peptide as a cancer-targeting unit, and camptothecin (CPT) as a model active agent. Upon reaction with free thiols in aqueous media at pH 7.4, disulfide cleavage occurs. This leads to release of the free CPT active agent, as well as the production of a red-shifted fluorescence emission (λ(max) = 535 nm). Confocal microscopic experiments reveal that 1 is preferentially taken up by U87 cells over C6 cells. On the basis of competition experiments involving okadaic acid, an inhibitor of endocytosis, it is concluded that uptake takes place via RGD-dependent endocytosis mechanisms. In U87 cells, the active CPT payload is released within the endoplasmic reticulum, as inferred from fluorescence-based colocalization studies using a known endoplasmic reticulum-selective dye. The present drug delivery system (DDS) could represent a new approach to so-called theragnostic agent development, wherein both a therapeutic effect and drug uptake-related imaging information are produced and can be readily monitored at the subcellular level. In due course, the strategy embodied in conjugate 1 could allow for more precise monitoring of dosage levels, as well as an improved understanding of cellular uptake and release mechanisms. 相似文献
998.
A novel ferrocene-based anion receptor bearing amide and triazolium donor groups and its anion complexation have been reported. We found that it shows marked electrochemical selectivity to F(-), followed by AcO(-) > Cl(-) > Br(-) > I(-), which is in accordance with (1)H NMR titration results. 相似文献
999.
Polydiacetylene (PDA) liposomes possess unique properties that allow liposomes to change color and emit fluorescence in response to stimuli such as temperature, antibody-antigen interaction, pH, mechanical stress, and organic solvent. They have been studied extensively as signal transducers in biosensor applications. Here, we describe an antibody-based biosensor using PDA liposomes for detection of human immunoglobulin E (hIgE). Target hIgE chemically bound to hIgE monoclonal antibodies immobilized on PDA liposomes and the fluorescent signals were slightly increased depending on the target protein concentration. As the primary response, the hIgE could be detected to below 10 ng mL(-1). However, fluorescent signals were dramatically increased depending on the target protein concentration when gold nanoparticle-conjugated polyclonal antibody probes were added on the PDA liposomes after the primary immune reaction. A PDA liposome biosensor could detect the hIgE as low as 0.1 ng mL(-1) and the sensitivity was increased up to one hundred times higher than the primary response. As a result, we confirmed that gold nanoparticle-conjugated polyclonal antibody probes efficiently enhanced the fluorescent signal of the PDA liposome biosensor chip. This strategy can be useful to detect proteins of ultra-low concentration. 相似文献
1000.
We developed an olfactory-nanovesicle-fused carbon-nanotube-transistor biosensor (OCB) that mimics the responses of a canine nose for the sensitive and selective detection of hexanal, an indicator of the oxidation of food. OCBs allowed us to detect hexanal down to 1 fM concentration in real-time. Significantly, we demonstrated the detection of hexanal with an excellent selectivity capable of discriminating hexanal from analogous compounds such as pentanal, heptanal, and octanal. Furthermore, we successfully detected hexanal in spoiled milk without any pretreatment processes. Considering these results, our sensor platform should offer a new method for the assessment of food quality and contribute to the development of portable sensing devices. 相似文献