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331.
High‐strength pressure‐free bonding is investigated using Cu nanoparticles as an alternative to conventional solders. Focus is placed on the morphology of Ni‐Sn intermetallic nanoparticles, an additive to a paste of Cu nanoparticles, for improvement of sinterability. The shear strength increases from 23.2 (Cu nanoparticles only) to 31.8 MPa, when 10 wt% of the newly synthesized 15‐nm Ni3Sn2 nanocubes is mixed with the Cu nanoparticle paste. This is the first example of the use of base metal nanoparticles under pressure‐free conditions to achieve the bonding strength of an ordinary Pb‐free solder (Sn‐Ag‐Cu). The addition of smaller Ni3Sn2 nanocubes 8 nm in size or irregularly shaped Ni3Sn2 nanoparticles (25.0 MPa) results in a limited increase in shear strength (26.6 MPa), while the addition of micrometer‐sized Ni3Sn2 particles results in a decrease in shear strength (21.5 MPa). The effects of the size and shape of the added Ni3Sn2 particles on the shear strength are discussed based on SEM observation of the sintered layers. 相似文献
332.
Dr. Ryota Suwa Assoc. Prof. Masayuki Hatta Prof. Kazuhiko Ichikawa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(42):13656-13661
CaCO3‐saturated saline waters at pH values below 8.5 are characterized by two stationary equilibrium states: reversible chemical calcification/decalcification associated with acid dissociation, Ca2++HCO3??CaCO3+H+; and reversible static physical precipitation/dissolution, Ca2++CO32??CaCO3. The former reversible reaction was determined using a strong base and acid titration. The saturation state described by the pH/PCO2‐independent solubility product, [Ca2+][CO32?], may not be observed at pH below 8.5 because [Ca2+][CO32?]/([Ca2+][HCO3?]) ?1. Since proton transfer dynamics controls all reversible acid dissociation reactions in saline waters, the concentrations of calcium ion and dissolved inorganic carbon (DIC) were expressed as a function of dual variables, pH and PCO2. The negative impact of ocean acidification on marine calcifying organisms was confirmed by applying the experimental culture data of each PCO2/pH‐dependent coral polyp skeleton weight (Wskel) to the proton transfer idea. The skeleton formation of each coral polyp was performed in microspaces beneath its aboral ectoderm. This resulted in a decalcification of 14 weight %, a normalized CaCO3 saturation state Λ of 1.3 at PCO2 ≈400 ppm and pH ≈8.0, and serious decalcification of 45 % and Λ 2.5 at PCO2 ≈1000 ppm and pH ≈7.8. 相似文献
333.
Surface‐Junction Effects on Interfacial Electron Transfer between Bis(terpyridine)iron(II) and Hydrogen‐Terminated Silicon(111) Electrode 下载免费PDF全文
Hiroaki Maeda Dr. Ryota Sakamoto Prof. Dr. Hiroshi Nishihara 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(10):2761-2764
Interfacial electron transfer at bis(tpy)–iron(II) complexes (tpy=2,2′:6′,2′′‐terpyridine) on Si(111) electrodes was investigated by using four types of surface‐anchor terpyridine ligands. Despite the greater distance, electron transfer between the bis(tpy)–iron(II) unit and the electrode is accelerated in surface‐anchor ligands with an additional phenylene group. 相似文献
334.
Nishinaga T Uto T Inoue R Matsuura A Treitel N Rabinovitz M Komatsu K 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(7):2067-2074
A detailed investigation has been made into the antiaromaticity and chemical reactivity of a planar cyclooctatetraene (COT) molecule fully annelated with bicyclo[2.1.1]hexane units 2. In spite of its planar 8pi-electronic structure, theoretical calculations have indicated that the antiaromaticity of COT 2 is considerably decreased in comparison with a planar COT 16 with D 4h symmetry. This behavior appears to be related to the wider HOMO-LUMO gap of 2 relative to 16, which is caused by the raised LUMO level as a result of the effective sigma-pi* orbital interaction between the strained bicyclic framework and the COT pi system. The two-electron reduction of 2 required the use of potassium mirror or a combination of lithium/corannulene in highly dried [D8]THF at -78 degrees C under vacuum. In contrast, the [4+2] cycloaddition of 2 with tetracyanoethylene (TCNE) proceeded quite smoothly owing to the high-lying HOMO. Reaction of 2 with meta-chloroperbenzoic acid gave all-trans tetraepoxide 23 in the same way as the corresponding benzene derivative 3. While the Simons-Smith-type cyclopropanation of benzene 3 gave tricyclopropanated derivative 21, the reaction of 2 only afforded isomers of dicyclopropanated derivatives 25 and 26. Yet, the reactivity of 2 is higher than the parent COT, which does not show any reactivity under the same conditions. On the basis of homodesmic reactions, it was concluded that release of strain is also an important factor for such relatively high reactivity in the epoxidation and cyclopropanation of bicycloannelated COT 2 as well as benzene 3. 相似文献
335.
Y Imazaki E Shirakawa R Ueno T Hayashi 《Journal of the American Chemical Society》2012,134(36):14760-14763
Aryl triflates were transformed to aryl bromides/iodides simply by treating them with LiBr/NaI and [Cp*Ru(MeCN)(3)]OTf. The ruthenium complex also catalyzed the transformation of alkenyl sulfonates and phosphates to alkenyl halides under mild conditions. Aryl and alkenyl triflates undergo oxidative addition to a ruthenium(II) complex to form η(1)-arylruthenium and 1-ruthenacyclopropene intermediates, respectively, which are transformed to the corresponding halides. 相似文献
336.
KY Inoue M Matsudaira R Kubo M Nakano S Yoshida S Matsuzaki A Suda R Kunikata T Kimura R Tsurumi T Shioya K Ino H Shiku S Satoh M Esashi T Matsue 《Lab on a chip》2012,12(18):3481-3490
We have developed an LSI-based amperometric sensor called "Bio-LSI" with 400 measurement points as a platform for electrochemical bio-imaging and multi-point biosensing. The system is comprised of a 10.4 mm × 10.4 mm CMOS sensor chip with 20 × 20 unit cells, an external circuit box, a control unit for data acquisition, and a DC power box. Each unit cell of the chip contains an operational amplifier with a switched-capacitor type I-V converter for in-pixel signal amplification. We successfully realized a wide dynamic range from ±1 pA to ±100 nA with a well-organized circuit design and operating software. In particular, in-pixel signal amplification and an original program to control the signal read-out contribute to the lower detection limit and wide detection range of Bio-LSI. The spacial resolution is 250 μm and the temporal resolution is 18-125 ms/400 points, which depends on the desired current detection range. The coefficient of variance of the current for 400 points is within 5%. We also demonstrated the real-time imaging of a biological molecule using Bio-LSI. The LSI coated with an Os-HRP film was successfully applied to the monitoring of the changes of hydrogen peroxide concentration in a flow. The Os-HRP-coated LSI was spotted with glucose oxidase and used for bioelectrochemical imaging of the glucose oxidase (GOx)-catalyzed oxidation of glucose. Bio-LSI is a promising platform for a wide range of analytical fields, including diagnostics, environmental measurements and basic biochemistry. 相似文献
337.
Sakamoto R Tsukada S Nishihara H 《Dalton transactions (Cambridge, England : 2003)》2012,41(34):10123-10135
This Perspective addresses our recent studies relating to metalladithiolenes and their cluster complexes that exhibit peculiar electronic communication in mixed-valent (MV) states. Chapter 1 provides an introduction for the Perspective. Chapter 2 enumerates a series of phenylene-annulated π-conjugated trinuclear metalladithiolenes with intense electronic communication in the MV states. Chapter 3 treats heterometal cluster complexes synthesized by integrating zero-valent metal carbonyls on mononuclear metalladithiolenes, taking advantage of the coordination unsaturation of the latter. In the field of MV chemistry, their electronic communication through metal-metal bonds and potential inversion behavior are intriguing properties. Chapter 4 describes hexanuclear and nonanuclear heterometal cluster complexes created in combination with the methods introduced in Chapters 2 and 3. The resultant heterometal cluster complexes feature electronic communication through the vast phenylene-annulated π-conjugated trinuclear metalladithiolene frameworks, the intensity of which correlates with their planarity. Each chapter describes the synthesis, structural features, and electrochemical properties of the relevant compounds. 相似文献
338.
[reaction: see text] Unusual stereoselectivity changes, i.e., enhancement and inversion of enantioselectivity with increasing temperature, were observed in the asymmetric reduction of methyl benzoylformate with chiral 1,4-dihydropyridines possessing amino acid residues as ligating chiral auxiliaries. The differential activation parameters, DeltaDeltaH(S-R) and DeltaDeltaS(S-R), obtained from the Eyring plots demonstrate that the entropy term controls the enantiodifferentiating step, accounting for the observed unique temperature dependencies. 相似文献
339.
In order to improve the solubility of intensively fluorescent 2,5-bis(benzimidazol-2-yl)pyrazine (BBIP), we synthesized new BBIP derivatives (2, 3a,b, and 5a,b) possessing two alkyl chains at the N-1 and N-1′ positions of the two benzimidazole moieties. Characterization of these compounds demonstrated that they exhibit high fluorescence intensity even in protic solvents, as well as solvatochromic fluorescence, in which their fluorescence maxima in aqueous methanol exhibited bathochromic shift with increasing ?r value of the medium. We utilized 5a as a microenvironment polarity probe to indicate the variation in polarity around the backbone of the temperature-sensitive poly(N-isopropylacrylamide) by measuring the spectral change caused by the thermal phase transition of the polymer. 相似文献
340.