全文获取类型
收费全文 | 527篇 |
免费 | 15篇 |
国内免费 | 3篇 |
专业分类
化学 | 365篇 |
晶体学 | 2篇 |
力学 | 11篇 |
数学 | 88篇 |
物理学 | 79篇 |
出版年
2022年 | 8篇 |
2021年 | 8篇 |
2020年 | 2篇 |
2019年 | 7篇 |
2018年 | 7篇 |
2017年 | 4篇 |
2016年 | 20篇 |
2015年 | 16篇 |
2014年 | 17篇 |
2013年 | 38篇 |
2012年 | 35篇 |
2011年 | 35篇 |
2010年 | 23篇 |
2009年 | 24篇 |
2008年 | 30篇 |
2007年 | 27篇 |
2006年 | 31篇 |
2005年 | 27篇 |
2004年 | 26篇 |
2003年 | 26篇 |
2002年 | 16篇 |
2001年 | 6篇 |
2000年 | 5篇 |
1999年 | 8篇 |
1998年 | 5篇 |
1997年 | 4篇 |
1996年 | 6篇 |
1995年 | 7篇 |
1994年 | 7篇 |
1993年 | 5篇 |
1992年 | 8篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 6篇 |
1984年 | 5篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1976年 | 2篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1940年 | 1篇 |
排序方式: 共有545条查询结果,搜索用时 15 毫秒
141.
We study properties of weakly disconjugate linear Hamiltonian systems. We characterize this concept in terms of a nonoscillation condition. We then show how to approximate a weakly disconjugate system by one with an exponential dichotomy. 相似文献
142.
Andreasson-Ochsner M Fu Z May S Xiu LY Nallani M Sinner EK 《Langmuir : the ACS journal of surfaces and colloids》2012,28(4):2044-2048
To improve the stability of cell membrane mimics, there has been growing interest in the use of block copolymers. Here, we present an easy approach to create an array of planar polymeric matrices capable of hosting membrane proteins. The array of polymeric matrices was formed by the selective deposition of triblock copolymers onto an array of hydrophilic islands situated within a hydrophobic background. The thickness of these matrices corresponds to the length of a single polymer chain. These polymeric matrices were used to host cell-free expressed membrane proteins, and offers a prototype from which a membrane protein array can be created for diagnostics or drug discovery purposes. 相似文献
143.
Vanderheiden S Bulat B Zevaco T Jung N Bräse S 《Chemical communications (Cambridge, England)》2011,47(32):9063-9065
A novel access to deuterated and D(3)CO-substituted arenes has been developed using immobilized triazenes as precursors. The linker system and the deuterating cleavage methodology could be shown to be compatible with various functional groups and are therefore suitable for the synthesis of derivatives only hardly available via comparable protocols. 相似文献
144.
145.
Determination of deoxynivalenol (vomitoxin) by high-performance liquid chromatography with electrochemical detection 总被引:2,自引:0,他引:2
V L Sylvia T D Phillips B A Clement J L Green L F Kubena N D Heidelbaugh 《Journal of chromatography. A》1986,362(1):79-85
A rapid method for the analysis of deoxynivalenol (DON) was developed using high-performance liquid chromatography (HPLC) with reductive electrochemical detection (ED). Deoxynivalenol produced by Fusarium roseum growing on solid cornmeal and rice substrates and from naturally contaminated wheat was extracted and quantitated via ED. DON levels in wheat were verified by gas chromatography and structurally confirmed by mass spectrometry. DON was optimally resolved by HPLC employing a radially compressed octadecylsilane column and a mobile phase of deoxygenated methanol-40 mM borate buffer (35:65) at a flow-rate of 1.0 ml/min. Under these conditions DON exhibited an average retention time of 3.6 min. Reductive ED (-1.4 V) allowed a 12-fold increase in sensitivity and greater selectivity than classical UV absorption at 224 nm. A detection limit for DON of 25 pg/microliter was achieved under these conditions. The determination of DON in crude grain extracts was hindered by extractable interfering substances, whereas ED was more functional-group selective (i.e. reduction of the carbonyl moiety). ED permits a direct quantitation of DON from crude grain extracts and may facilitate the determination of this agent and associated metabolites in biological samples. 相似文献
146.
Lensen MC van Dingenen SJ Elemans JA Dijkstra HP van Klink GP van Koten G Gerritsen JW Speller S Nolte RJ Rowan AE 《Chemical communications (Cambridge, England)》2004,(7):762-763
A giant porphyrin disc (M(w)= 15 kDa) has been synthesized and its self-assembly behaviour at an interface studied by liquid STM which reveals the presence of huge domains (>400 x 400 nm2) of very well ordered and molecularly resolved columnar stacks. 相似文献
147.
Induction of Proinflammatory Cytokines in Human Epidermoid Carcinoma Cells by in vitro Ultraviolet A1 Irradiation 总被引:4,自引:0,他引:4
Akimichi Morita Markus Grewe Susanne Grether-Beck Sylvia Olaizola-Horn Jean Krutmann 《Photochemistry and photobiology》1997,65(4):630-635
Abstract— Ultraviolet radiation-induced expression of cytokines by keratinocytes is important for the pathogenesis of polymorphous light eruption (PLE). Because UVA1 radiation rather than UVB radiation might be a more important trigger for PLE, cells from the human epidermoid carcinoma cell line KB were exposed in vitro to UVA1 radiation (30 J/cm2 ) and subsequently analyzed for cytokine expression. Ultraviolet A1 irradiation induced tumor necrosis factor (TNF)-a and interleukin (IL)-8 expression in KB cells at the mRNA and protein level. Upregulation of cytokine mRNA levels followed a Diphasic pattern. This effect was specific for TNFa and IL-8 because UVA1 radiation did not induce expression of IL-la or IL-6 in these cells. Ultraviolet Al radiation-induced expression of intercellular adhesion molecule-1 in KB cells previously was found to depend on the thiol status of these cells. Therefore, KB cells were treated with DL-buthionine-[S, R]-sulfoximine (BSO), a specific inhibitor of de novo glutathione synthesis. Exposure of BSO-pretreated KB cells to UVA1 radiation significantly induced IL-1α and IL-6 mRNA and protein expression. These studies demonstrate the capacity of UVA1 radiation to induce cytokine expression in human epidermoid carcinoma cells. This immunomodulatory effect may be mediated by thiol-status-dependent and -independent mechanisms. 相似文献
148.
Víctor Manríquez Marcelo Campos-Vallette Nelson Lara Nelson González-Tejeda Oscar Wittke Guillermo Díaz Sylvia Diez René Muñoz Lukas Kriskovic 《Journal of chemical crystallography》1996,26(1):15-22
The structures of [Cu(en)(H2O)2]SO4 (I), [Cu(en)2](NO3)2 (II) and [Cu(trien)I]I (III) have been determined by single crystal X-ray diffraction. ComplexI is monoclinic, space group C2/c, with unit cell parametera=7.232(1),b=11.725(2),c=9.768(1), =105.50(1)°, andZ=4. ComplexII is also monoclinic, space group P21/a, witha=7.978(2),b=9.982(4),c=8.218(3), =111.11(2)°, andZ=2. ComplexIII is orthorhombic, space group P212121, witha=8.098(1),b=11.902(1),c=13.682(2), andZ=4. The structures were solved by direct methods and refined by full-matrix least-squares to finalR values of 0.031, 0.043 and 0.036 for complexesI, II, andIII, respectively. ComplexesI andII show an octahedral coordination geometry. ComplexIII shows a square pyramidal coordination geometry. ComplexI forms infinite monodimensional chains where the SO
4
2–
ions acts as a bridge between two neighboringen molecules. The vibrational spectra of these complexes agree well with their crystal structures. Structure and stability of seven other related Cu(II) complexes of (trien), (dien)2, (en)2 and (en) are inferred in this study. 相似文献
149.
150.