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81.
Temperature-modulated differential scanning calorimetry (TMDSC) is known to have the ability to measure heat capacity of materials
more accurately than the conventional differential scanning calorimeter. However, the accuracy of the measured heat capacity
displays significant dependence on various experimental parameters such as period of modulation (p), amplitude of modulation (a), geometry of sample (g), heating rate (r), etc. One of the key features of this system is the ability to measure heat capacity under quasi-isothermal conditions.
In the present investigation, heat capacity of a well-established system namely sapphire and thoria was measured by TMDSC
under dynamic mode and also under quasi-isothermal mode. The experimental parameters, mentioned above p, a, g, and r are varied to establish the conditions for measuring heat capacity accurately. 相似文献
82.
G. Panneerselvam R. Venkata Krishnan K. Nagarajan M. P. Antony 《Journal of Thermal Analysis and Calorimetry》2010,101(1):169-173
Dysprosium hafnate is a candidate material for as control rods in nuclear reactor because dysprosium (Dy) and hafnium (Hf)
have very high absorption cross-sections for neutrons. Dysprosium hafnate (Dy2O3·2HfO2-fluorite phase solid solution) was prepared by solid-state as well as wet chemical routes. The fluorite phase of the compound
was characterized by using X-ray diffraction (XRD). Thermal expansion characteristics were studied using high temperature
X-ray diffraction (HTXRD) in the temperature range 298–1973 K. Heat capacity measurements of dysprosium hafnate were carried
out using differential scanning calorimetry (DSC) in the temperature range 298–800 K. The room temperature lattice parameter
and the coefficient of thermal expansion are 0.5194 nm and 7.69 × 10−6 K−1, respectively. The heat capacity value at 298 K is 232 J mol−1 K−1. 相似文献
83.
This paper obtains solutions to the Ostrovsky equation by employing the mapping method. Several solutions are determined including
the cnoidal waves, shock waves, solitary waves, periodic singular waves and others in the case of no rotation. Finally, the
ansatz method is applied to solve the equation with the rotation term present. 相似文献
84.
85.
Solutions to the Zakharov-Kuznetsov equation with higher order nonlinearity are obtained using the mapping method. Several
solutions are determined inclusing the cnoidal waves, shock waves, solitary waves, periodic singular waves and others. Finally,
the ansatz method is applied to solve the equation with power law nonlinearity. It has been proved that the shock waves or
topological solitons exist only for specific values of the power law parameter. 相似文献
86.
Shyam Krishnan 《Tetrahedron letters》2007,48(43):7571-7573
A method for the synthesis of 3,3-disubstituted oxindole derivatives is described. This involves the base-mediated addition of malonate esters to 3-halo-3-alkyloxindoles. The addition is tolerant of a range of alkyl substituents at position 3 of the oxindole. Addition to an aryl chloro-oxindole is also described. 相似文献
87.
Separable routing is the first of a number of routing schemes for circuit switched telephone traffic invented at Bellcore. These routing schemes are state dependent, in the sense that, for each call attempt, a routing decision is made on the basis of the state of the network (defined in terms of the numbers of busy and idle trunks in the various trunk groups at the moment of the call attempt). In this paper, we describe separable routing and its mathematical background. Simulation results we have presented elsewhere show that the family of state-dependent routing schemes, of which separable routing is a member, is very attractive in terms of blocking rate, built-in network management features, and behavior in the presence of traffic forecast error. 相似文献
88.
J. K. Varma P. Santhana Gopala Krishnan Veena Choudhary 《Journal of Thermal Analysis and Calorimetry》1990,36(7-8):2611-2622
The paper describes the synthesis of urethane methacrylate resins by reaction of tolylene diisocyanate (TDI), butanol-1 (B) and 2-hydroxyethylmethacrylate (HEMA) by a two step procedure. Characterisation was done using FT-IR, FT-NMR, Mass Spectroscopy. The effect of temperature on the UV-curing behaviour was investigated by differential photocalorimetry. An activation energy of 8.4 kJ/mole was found in the temperature range of 50–100°C. Free radical polymerisation in presence of benzoyl peroxide was also investigated. The polymers were stable upto 200°C in N2 atmosphere. A two step decomposition was observed in the temperature range of 200–500°C.
The Instrument system of E. I. DuPont de Nemours & Co. is acknowledged for differential photocalorimeter studies. 相似文献
Zusammenfassung Vorliegende Arbeit beschreibt die Synthese von Urethan-methacrylat-Harzen durch die Reaktion von Toluylendiisocyanat (TDI), Butanol-1 (B) und 2-Hydroxyethylmethacrylat (HEMA) in einem zweistufigen Herstellungsverfahren. Charakterisiert wurden die Produkte mittels FT-IR, FT-NMR und Massenspektroskopie. Anhand von Differentialfotokalorimetrie wurde der Einfluß der Temperatur auf das UV-Aushärtungsverhalten untersucht. Im Temperaturbereich 50–100°C wurde eine Aktivierungsenergie von 8.4 kJ/mol gefunden. Weiterhin wurde auch die Radikalkettenpolimerisation in Gegenwart von Benzoylperoxid untersucht. In Stickstoffatmosphäre sind die Polymere bis 200°C stabil. Im Temperaturbereich 200–500°C wurde eine zweistufige Zersetzung beobachtet.
The Instrument system of E. I. DuPont de Nemours & Co. is acknowledged for differential photocalorimeter studies. 相似文献
89.
Balasubramanian Sridhar Jagadeesh Babu Nanubolu Krishnan Ravikumar 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(2):128-135
A new polymorph of cytosine, C4H5N3O, is reported half a century after the report of its first known crystal structure [Barker & Marsh (1964). Acta Cryst. 17 , 1581–1587]. Cytosine thus provides the first polymorphic example in the category of parent nucleobases. The new form, denoted (Ib), was observed unexpectedly during an attempt to cocrystallize cytosine with catechol. Form (Ib) crystallizes in the orthorhombic centrosymmetric space group Pccn with two molecules in the asymmetric unit. The previously known form, denoted (Ia), crystallizes in the orthorhombic noncentrosymmetric space group P212121. The cytosine molecule is planar in both forms. Hydrogen‐bonding interactions are also similar for both forms. Infinite one‐dimensional ribbons composed of cytosine base‐pair dimers in R22(8) arrangements are observed in both (Ia) and (Ib). However, the way that the ribbons are packed differs in (Ia) and (Ib). This appears to guide the centrosymmetric versus noncentrosymmetric space‐group selection through the formation of an inversion‐related motif in polymorph (Ib) and a helical propagation in polymorph (Ia). A few selected polymorphic systems have been gathered from the Cambridge Structural Database to understand possible structural features responsible for achiral molecules adopting centro‐ and noncentrosymmetric space groups. 相似文献
90.
Krishnan Ravikumar Balasubramanian Sridhar Jagadeesh Babu Nanubolu Tamilselvan Rajasekaran Basi Venkata Subba Reddy 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(4):322-329
Four structures of oxoindolyl α‐hydroxy‐β‐amino acid derivatives, namely, methyl 2‐{3‐[(tert‐butoxycarbonyl)amino]‐1‐methyl‐2‐oxoindolin‐3‐yl}‐2‐methoxy‐2‐phenylacetate, C24H28N2O6, (I), methyl 2‐{3‐[(tert‐butoxycarbonyl)amino]‐1‐methyl‐2‐oxoindolin‐3‐yl}‐2‐ethoxy‐2‐phenylacetate, C25H30N2O6, (II), methyl 2‐{3‐[(tert‐butoxycarbonyl)amino]‐1‐methyl‐2‐oxoindolin‐3‐yl}‐2‐[(4‐methoxybenzyl)oxy]‐2‐phenylacetate, C31H34N2O7, (III), and methyl 2‐[(anthracen‐9‐yl)methoxy]‐2‐{3‐[(tert‐butoxycarbonyl)amino]‐1‐methyl‐2‐oxoindolin‐3‐yl}‐2‐phenylacetate, C38H36N2O6, (IV), have been determined. The diastereoselectivity of the chemical reaction involving α‐diazoesters and isatin imines in the presence of benzyl alcohol is confirmed through the relative configuration of the two stereogenic centres. In esters (I) and (III), the amide group adopts an anti conformation, whereas the conformation is syn in esters (II) and (IV). Nevertheless, the amide group forms intramolecular N—H...O hydrogen bonds with the ester and ether O atoms in all four structures. The ether‐linked substituents are in the extended conformation in all four structures. Ester (II) is dominated by intermolecular N—H...O hydrogen‐bond interactions. In contrast, the remaining three structures are sustained by C—H...O hydrogen‐bond interactions. 相似文献