全文获取类型
收费全文 | 1975篇 |
免费 | 76篇 |
国内免费 | 11篇 |
专业分类
化学 | 1403篇 |
晶体学 | 23篇 |
力学 | 65篇 |
数学 | 163篇 |
物理学 | 408篇 |
出版年
2024年 | 1篇 |
2023年 | 14篇 |
2022年 | 57篇 |
2021年 | 64篇 |
2020年 | 59篇 |
2019年 | 51篇 |
2018年 | 37篇 |
2017年 | 41篇 |
2016年 | 62篇 |
2015年 | 55篇 |
2014年 | 75篇 |
2013年 | 139篇 |
2012年 | 148篇 |
2011年 | 151篇 |
2010年 | 91篇 |
2009年 | 86篇 |
2008年 | 151篇 |
2007年 | 118篇 |
2006年 | 121篇 |
2005年 | 91篇 |
2004年 | 100篇 |
2003年 | 53篇 |
2002年 | 75篇 |
2001年 | 32篇 |
2000年 | 42篇 |
1999年 | 18篇 |
1998年 | 10篇 |
1997年 | 8篇 |
1996年 | 20篇 |
1995年 | 10篇 |
1994年 | 17篇 |
1993年 | 15篇 |
1992年 | 9篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1969年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有2062条查询结果,搜索用时 15 毫秒
991.
Yong‐Hyok Kwon Robert Ossig Frank Hubenthal Heinz‐Detlef Kronfeldt 《Journal of Raman spectroscopy : JRS》2012,43(10):1385-1391
We present experimental results to quantify and optimize the surface‐enhanced Raman scattering (SERS) activity of naturally grown silver nanoparticles. Ag nanoparticle ensembles with mean equivalent radii ranging from 10.6 to 20.3 nm were prepared under ultrahigh vacuum conditions by Volmer–Weber growth on quartz plates. A tuning of the localized surface plasmon polariton resonance wavelength from 453 to 548 nm was performed by varying the morphology of the silver nanoparticles. The dependence of the SERS activity on the plasmon resonance wavelength was investigated with a Raman set‐up containing a microsystem light source with an emission line at 488 nm. Shifted excitation Raman difference spectroscopy was applied to remove the fluorescence‐based background from the SERS spectra of pyrene in water using two slightly different emission wavelengths (487.61 and 487.91 nm) of the microsystem light source. We demonstrate that the Raman activities for all SERS substrates are available in the nanomolar range in a water sample. However, the Raman activity crucially depends on the plasmon resonance wavelength of the nanoparticle ensembles. Although for an on‐resonance ensemble the limit of detection for pyrene in water is very low and was estimated to be 2 nmol/L, it increases rapidly to several tens of nanomol for slightly off‐resonance ensembles. Hence, the highest SERS activity was obtained with a nanoparticle ensemble exhibiting a plasmon resonance wavelength at 491 nm, which almost coincides with the excitation wavelengths. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
992.
Nam TS Choi SH Rah SY Kim SY Jang W Im MJ Kwon HJ Kim UH 《Experimental & molecular medicine》2006,38(6):718-726
ADP-ribosyl cyclase (ADPR-cyclase) produces a Ca2+-mobilizing second messenger, cyclic ADP- ribose (cADPR), from beta-NAD+. A prototype of mammalian ADPR-cyclases is a lymphocyte antigen CD38. Accumulating evidence indicates that ADPR-cyclases other than CD38 are expressed in various cells and organs. In this study, we discovered a small molecule inhibitor of kidney ADPR-cyclase. This compound inhibited kidney ADPR-cyclase activity but not CD38, spleen, heart or brain ADPR-cyclase activity in vitro. Characterization of the compound in a cell-based system revealed that an extracellular calcium-sensing receptor (CaSR)- mediated cADPR production and a later long-lasting increase in intracellular Ca2+ concentration ([Ca2+]i) in mouse mesangial cells were inhibited by the pre-treatment with this compound. In contrast, the compound did not block CD3/TCR-induced cADPR production and the increase of [Ca2+]i in Jurkat T cells, which express CD38 exclusively. The long-lasting Ca2+ signal generated by both receptors was inhibited by pre-treatment with an antagonistic cADPR derivative, 8-Br-cADPR, indicating that the Ca2+ signal is mediated by the ADPR-cyclase metabolite, cADPR. Moreover, among structurally similar compounds tested, the compound inhibited most potently the cADPR production and Ca2+ signal induced by CaSR. These findings provide evidence for existence of a distinct ADPR-cyclase in the kidney and basis for the development of tissue specific inhibitors. 相似文献
993.
Yee SB Baek SJ Park HT Jeong SH Jeong JH Kim TH Kim JM Jeong BK Park BS Kwon TK Yoon I Yoo YH 《Experimental & molecular medicine》2006,38(6):634-642
In a preliminary study, we found that benzyloxycarbonyl-Val-Ala-Asp(OMe)-fluoromethylketone (zVAD- fmk), unlike Boc-aspartyl(OMe)-fluoromethylketone (BocD-fmk), at usual dosage could not prevent genistein-induced apoptosis of p815 mastocytoma cells. This study was undertaken to reveal the mechanism underlying the incapability of zVAD-fmk in preventing this type of apoptosis. We observed that 14-3-3 protein level was reduced in genistein-treated cells and that BocD-fmk but not zVAD-fmk prevented the reduction of 14-3-3 protein level and the release of Bad from 14-3-3. We also demonstrated that truncated Bad to Bcl-xL interaction in genistein- treated cells was prevented by BocD-fmk but not by zVAD-fmk treatment. Our data indicate that BocD- fmk, compared to zVAD-fmk, has a certain preference for inhibiting 14-3-3/Bad signalling pathway. We also elucidated that this differential efficacy of BocD-fmk and zVAD-fmk resulted from the different effect in inhibiting caspase-6 and that co-treatment of zVAD-fmk and caspase-6 specific inhibitor substantially prevented genistein-induced apoptosis. Our data shows that caspase-6 plays a role on Bad/14-3-3 pathway in genistein-induced apoptosis of p815 cells, and that the usual dose of zVAD-fmk, in contrast to BocD-fmk, did not prevent caspase-6 acting on 14-3-3/Bad-mediated event. 相似文献
994.
Lee EA Kim JE Seo JH Kwon BS Nam SH Kwon B Cho HR 《Experimental & molecular medicine》2006,38(6):606-615
Our previous study has demonstrated that there is a significant delay of Balb/c cardiac allograft rejection in the C57BL/6 4-1BB-deficient knockout recipient. In this study, we examined the effect of combined blockade of the 4-1BB and CD28 costimulatory pathways on cardiac allograft rejection in the C57BL/6-->Balb/c model. A long-term cardiac allograft survival was induced in CD28/4-1BB- deficient mice (>100 days survival in 3 of 4 mice), which was comparable with CD28-deficient mice (>100 days survival in 2 of 5 mice; P<0.2026). There was no long-term cardiac allograft survival in either wild-type (WT) or 4-1BB-deficient mice, even though 4-1BB-deficient recipients showed a significant delay of cardiac allograft rejection than WT mice. An in vitro mixed leukocyte reaction (MLR) assay showed that 4-1BB-deficient and WT mouse T cells had a similar responsiveness to allostimulation, whereas CD28- and CD28/4-1BB-deficient mouse T cells had a defective responsiveness to allostimulation. Furthermore, 4-1BB-deficient mice showed a similar CTL but an elevated Ab response against alloantigens as compared to WT mice, and the alloimmune responses of 4-1BB-deficient mice were abrogated in the CD28-deficient background. Overall, these results indicate that the CD28 costimulatory pathway plays a major role in the alloimmune response and that 4-1BB signals are dependent upon CD28 signals. 相似文献
995.
996.
997.
Yun Jung Jang Byung-Sik Moon Min Sun Park Ji Young Kwon Yeo Joon Yoon Juyoung Yoon 《Tetrahedron letters》2006,47(16):2707-2710
New cavitand derivatives (1, 2) bearing four coumarin groups were synthesized, and the binding properties of these cavitands towards metal ions were examined through their fluorescent changes. Cavitand 1 effectively recognized the Cu2+ ions among the metal ions examined. The recognition of cavitand 1-Cu2+ with dicarboxlyates is also described. 相似文献
998.
We have synthesized several new quinophenoxazine analogues and tested their cytotoxicity activities. The results showed that the compounds, 4a and 4b, possessing phenyl ring in the structure have almost same pharmacological capacity with A-62176. This finding suggests that the phenyl ring portion is important to this series of compounds for the activity expression. 相似文献
999.
Oh JK Tang C Gao H Tsarevsky NV Matyjaszewski K 《Journal of the American Chemical Society》2006,128(16):5578-5584
A new methodology for the synthesis and functionalization of nanometer-sized colloidal particles consisting of well-defined, water-soluble, functional polymers with narrow molecular weight distribution (M(w)/M(n) < 1.3) was developed, utilizing atom transfer radical polymerization (ATRP) of water-soluble monomers in an inverse miniemulsion. The optional introduction of a disulfide-functionalized cross-linker allowed for the synthesis of cross-linked (bio)degradable nanogels. Dynamic light scattering (DLS) and atomic force microscopy (AFM) measurements indicated that these particles possessed excellent colloidal stability. ATRP in inverse miniemulsion led to materials with several desirable features. The colloidal particles preserved a high degree of halogen chain-end functionality, which enabled further functionalization. Cross-linked nanogels with a uniformly cross-linked network were prepared. They were degraded to individual polymeric chains with relatively narrow molecular weight distribution (M(w)/M(n) < 1.5) in a reducing environment. Higher colloidal stability, higher swelling ratios, and better controlled degradability indicated that the nanogels prepared by ATRP were superior to their corresponding counterparts prepared by conventional free radical polymerization (RP) in inverse miniemulsion. 相似文献
1000.
We report here an enzyme-amplified, sandwich-type immunosensor for detecting the biospecific interaction between an antibody and antigen using redox mediation. We employed biotin/anti-biotin IgG as a model immunosensing pair. Partially ferrocenyl-tethered dendrimer (Fc-D), whose ferrocene moiety acts as a redox mediator, was immobilized to the electrode surface by covalent binding between the dendrimer amines and the carboxylic acids of a self-assembled monolayer. The unreacted amines of the immobilized Fc-D were modified with biotin groups to allow the specific binding of goat anti-biotin IgG. Rabbit anti-goat IgG-conjugated alkaline phosphatase was bound to goat anti-biotin IgG to catalyze conversion of p-aminophenyl phosphate monohydrate to p-aminophenol. This product is oxidized to quinoimide by the reduction of ferrocenium back to ferrocene, producing an electrocatalytic anodic current. Cyclic voltammograms and surface plasmon resonance experiments showed that the binding of nonspecific proteins is not significant on the biotinylated Fc-D surface. We also examined the change in peak current according to the concentration of anti-biotin IgG and found that the detection range of this immunosensing scheme is between 0.1 and 30 microg mL(-1). 相似文献