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111.
Tutusaus O Viñas C Kivekäs R Sillanpää R Teixidor F 《Chemical communications (Cambridge, England)》2003,(19):2458-2459
Designed ligands have been synthesised to produce the first arene-like metallacarborane. For arene-like coordination the number of electronegative elements on the coordinating site must be kept to a minimum. Choosing ligands with bulky substituents on the heteroatom allows easy rearrangement and arene-like coordination. This is more hampered the higher the number of hetereoatoms to be re-located. 相似文献
112.
[reaction: see text] The dipolarophilic reactivity of enantiopure (Z)-3-p-tolylsulfinylacrylonitriles (1) has been evaluated with diazoalkanes. 3-Cyanopyrazoles are obtained when R = H, but with R = alkyl (Bn, n-Bu, and t-Bu) only one cycloadduct (4 or 5) is formed in high yield under mild conditions, therefore evidencing a complete control of the regioselectivity and the endo/exo and pi-facial selectivities. These reactions are a new straightforward entry to the synthesis of pyrazolines and related structures and reveal the excellent dipolarophilic features of (Z)-sulfinylacrylonitriles. 相似文献
113.
Ponce AM Blanco SE Molina AS García-Domenech R Gálvez J 《Journal of chemical information and computer sciences》2000,40(4):1039-1045
A study was performed on xanthine-oxidase inhibition by 22 flavonoids, including flavones, flavonols, flavanones, and chalcones, using UV spectroscopy for experimental data and molecular topology to establish the structure-activity relationship (SAR) model. The flavonoids were classified into four groups according to their activity on xanthine-oxidase (inactive, low, significant, or high), and linear discriminant analysis was used to classify each compound within a group. The results led to a very good model, which was able to classify correctly as xanthine oxidase inhibitors, along with a test set of molecules including a variety of different compounds such as allopurinol, caffeic acid, esculetin, and alloxantin. 相似文献
114.
We solve the Klein–Gordon equation in the presence of a spatially one-dimensional cusp potential. The scattering solutions are obtained in terms of Whittaker functions and the condition for the existence of transmission resonances is derived. We show the dependence of the zero-reflection condition on the shape of the potential. In the low-momentum limit, transmission resonances are associated with half-bound states. We express the condition for transmission resonances in terms of the phase shifts. 相似文献
115.
Experimental molar conductivity data for KCl, NaCl and LiCl in glycerol at 298.15?K were analysed by least-square fitting in the concentration range 0.5–100?mol?m?3in order to compute the values of the molar conductivity at infinite dilution Λ0and the Onsager constant S. Using previously measured transference numbers and assuming the Kohlrausch infinite dilution law, the limiting ionic mobilities were deduced. The results obtained show that the transport mechanisms in this solvent and other similar hydrogen-bonded solvents such as water and ethylene glycol are the same. The data were also interpreted in terms of ion–ion and ion–solvent interactions using the Fuoss paired ion model in the concentration range 0.5–100?mol?m?3. The fitting of Fuoss’ equation of 1978 to these data led us to an estimate of the ionic association by computing the conductimetric pairing constants. The latter were further analysed by Gilkerson's equation to yield the difference between the solvation energy of the free ions and the ion pairs. The computed values allow an estimation of whether the electrolyte is a structure maker or a structure breaker. 相似文献
116.
Pablo Salvador Julia Real Clara Zamorano Antonio Villanueva 《Mathematical and Computer Modelling》2011,53(1-2):42-54
In recent years, ground vibrations have become an important issue due to the growing awareness of the society about environmental living conditions. In this way, vibrations caused by trains running near houses or workplaces are considered disturbing for residents. Within this framework, this paper presents a procedure to estimate the vibration path caused by the passing of a train. In order to achieve this, the equations which describe the physical phenomenon are set in the frequency and wavenumber domain and solved by using the Fourier Transform. The obtained analytical solution is transformed back into the time and space domain by means of the Fourier series. The obtained theoretical results are compared with experimental measurements carried out in the Madrid–Barcelona High Speed Line in order to analyse the performance of this procedure. 相似文献
117.
A. Viña Orjales M. I. Turnes Carou M. C. Prieto Blanco P. López Mahía S. Muniategui Lorenzo D. Prada Rodríguez 《Chromatographia》2000,51(1-2):77-82
Summary A systematic investigation of operational buffer systems, sample preparation and instrument parameters for achieving the best
possible performance for determinating an homologous series of N-benzyl-N-alkyl-N,N-dimethylammonium chloride compounds by
capillary zone electrophoresis with direct UV detection. The most effective separation was achieved within 3.5 min with the
addition of acetonitrile (40%) in a phosphate buffer (20 mM pH 5.2) using a 40 cm fused-silica capillary operating at 25 KV
and 20°C. Degassing of all electrolyte solutions and samples was very important. The linearity and repeatability for each
compounds were satisfactory. To improve detection limits, on-column sample preconcentration, sample stacking, was investigated
achieving a tenfold enrichment factor and quantitation limits about 10−7M. 相似文献
118.
Temperature measurements of shock heated materials using multispectral pyrometry: Application to bismuth 总被引:1,自引:0,他引:1
A new device for temperature measurements of shock heated materials has been developed in order to refine their equations
of state. We present temperature measurements for bismuth samples in contact with a lithium fluoride window. The shock pressure
of these experiments ranges from 18 to 97 GPa.
Received 2 June 1997 / Accepted 26 January 1998 相似文献
119.
The preparation of various (hex-5-ynyl)silanes was achieved following two different synthetic approaches from readily available materials such as 4-bromobutene, 6-iodohexyne and chlorosilanes. Different reaction conditions for intramolecular hydrosilylation were tested to prepare the corresponding 2-methylidene-1-silacyclohexanes. Notably, the use of Speier’s catalyst allowed the regioselective formation of the desired products in moderate yields. 相似文献
120.
Control of crystalline phases in magnetic Fe nanoparticles inserted inside a matrix of porous carbon
M.P. Fernández D.S. Schmool A.S. Silva M. Sevilla A.B. Fuertes P. Gorria J.A. Blanco 《Journal of magnetism and magnetic materials》2010,322(9-12):1300-1303
Two magnetic composites made up of Fe nanoparticles (Fe-NPs) embedded in a porous amorphous carbon matrix are presented. One of the samples, Fe-S-AC, was obtained with the aid of sucrose and the other, Fe-AC, in the absence of this substance. The XRD patterns show Bragg diffraction peaks associated with α-Fe and γ-Fe crystalline phases in the Fe-AC sample, while only peaks corresponding to the α-Fe phase are observed for Fe-S-AC powders. The Fe-NPs exhibit broad particle-size distributions for both samples, 5–50 nm for Fe-AC, whereas two populations (2–8 and 10–70 nm) for the Fe-S-AC composite are found. This fact gives rise to poorly defined blocking temperatures, as it can be deduced from the broad maxima observed in MZFC(T) variations. In addition, M(H) curves for both Fe-AC and Fe-S-AC samples reveal the existence of exchange-bias effect for T<60 K, probably due to a magnetic coupling within a core/shell structure of the Fe-NPs, although this effect was observed to be less significant for Fe-S-AC. 相似文献