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991.
Dunru Zhu Xiaolei Zhu Li Xu Sichang Shao S. Shanmuga Sundara Raj Hoong-Kun Fun Xiaozeng You 《Journal of chemical crystallography》2000,30(6):429-432
The 4-(p-methoxyphenyl)-3,5-bis(4-pyridyl)-1,2,4-triazole has been synthesized and its crystal structure has been determined by X-ray diffraction methods. It crystallizes in the monoclinic space group P21/n, with a = 12.5832(6) Å, b = 7.0512(5) Å, c = 18.4669(12) Å, = 96.826(1)°, and Dcalc = 1.345 g cm–1 for Z = 4. In the structure, two pyridyl rings, phenyl ring, and triazole ring do not share a common plane. The most favored orientation of the pyridyl rings in the crystal is that their planes are inclined toward opposite directions with respect to the triazole ring. 相似文献
992.
K.M. Abdul Malik Samiran Mitra Raj Kumar Bhubon Singh 《Journal of chemical crystallography》1999,29(8):877-883
Complexes [Co(tren)(Tsal)]ClO4·H2O 1 and [Ni(pn)(py)2(NCS)2] 2, (tren = tris(2-aminoethyl)amine, Tsal = thiosalicylate ion, pn = 1, 2-diamino propane and py = pyridine) have been synthesized and structurally characterized. Both complexes crystallize in the monoclinic space group C2/c with a = 21.3340(6), b = 11.7754(2), c = 14.8076(5) Å, = 100.3831(10)°, Z = 8 (1), and a = 7.2573(8), b = 17.8810(11), c = 15.2681(12) Å, = 101.170(2)°, Z = 4 (2). The metal atoms in both cases have distorted octahedral geometry. In 1, the tren ligand is quadridentate and Tsal is bidentate chelate. In 2, the pn ligand forms a bidentate chelate with the NCS ligands in trans positions. Complex 1 is diamagnetic whereas 2 shows paramagnetism with a magnetic moment of 3.10 B. M. 相似文献
993.
The anion recognition property of a naphthalene based receptor (L) was investigated by naked-eye, UV-Vis, fluorescence, 1H NMR and computational methods. The receptor L showed fluoride selective naked-eye detectable colorimetric and UV-Vis spectral changes over other tested anions due to the formation of hydrogen bonding complex in 1:1 stoichiometry and/or deprotonation between fluoride and the receptor. Interestingly, the fluorescence of L was quenched by fluoride but enhanced by acetate. 相似文献
994.
N. V. S. Rao P. R. Kishore T. F. S. Raj M. N. Avadhanlu C. R. K. Murty 《Molecular Crystals and Liquid Crystals》2013,570(1-2):65-73
The effects of external de and af electric fields of strengths up to 25kV/cm on the nematic liquid crystal p-ehtoxybenzylidene-[pacute]-n-butyl aniline (EBBA) are investigated. The effectiveness of electric fields and of high magnetic fields in producing molecular alignment are compared. Changes in the molecular alignment are observed in terms of changes in the rf dielectric constant. These measurements are as fruitful as microwave measurements in studying the degree of ordering of molecules in bulk samples of liquid crystals. The threshold voltages for chevron formation in the dielectric regime are found to be considerably lower than the threshold voltages necessary induce changes in dielectric constant in the same regime. 相似文献
995.
In this paper we report the results obtained from inelastic neutron scattering measurements on Zr2NiH1.9 and Zr2NiH4.6 using triple-axis spectrometer at Dhruva reactor, Trombay. The spectrum up to 35 meV represents largely the lattice modes
of Zr and Ni atoms. The vibrational frequencies of hydrogen atoms are expected predominantly at higher energies. The phonon
spectra from 35–180 meV were recorded using a Be filter as analyser. In order to analyse the observed neutron spectra, we
assume a set of Ein-stein modes due to the hydrogen atoms which are delta functions in energy. These delta functions are broadened
by the resolution of the instrument. The vibrational frequencies obtained from the fitting of the observed phonon spectra
have been assigned to various tetrahedral sites in both the compounds. 相似文献
996.
A Call center may be defined as a service unit where a group of agents handle a large volume of incoming telephone calls for
the purpose of sales, service, or other specialized transactions. Typically a call center consists of telephone trunk lines,
a switching machine known as the automatic call distributor (ACD) together with a voice response unit (VRU), and telephone
sales agents. Customers usually dial a special number provided by the call center; if a trunk line is free, the customer seizes
it, otherwise the call is lost. Once the trunk line is seized, the caller is instructed to choose among several options provided
by the call center via VRU. After completing the instructions at the VRU, the call is routed to an available agent. If all
agents are busy, the call is queued at the ACD until one is free. One of the challenging issues in the design of a call center
is the determination of the number of trunk lines and agents required for a given call load and a given service level. Call
center industries use the Erlang-C and the Erlang-B formulae in isolation to determine the number of agents and the number
of trunk lines needed respectively.
In this paper we propose and analyze a flow controlled network model to capture the role of the VRU as well as the agents.
Initially, we assume Poisson arrivals, exponential processing time at the VRU and exponential talk time. This model provides
a way to determine the number of trunk lines and agents required simultaneously. An alternative simplified model (that ignores
the role of the VRU) will be to use anM|M|S|N queueing model (whereS is the number of agents andN is the number of trunk lines) to determine the optimalS andN subject to service level constraints. We will compare the effectiveness of this simplified model and other approximate methods
with our model. We will also point out the drawbacks of using Erlang-C and Erlang-B formulae in isolation.
Contributed paper for the First Madrid Conference on Queueing Theory, held in Complutense University, Madrid, Spain, July
2–5, 2002 相似文献
997.
Rajni Sharma Raj Pal Sharma Ritu Bala Loretta Pretto Valeria Ferretti 《Journal of Molecular Structure》2006,800(1-3):93-99
The dipole, quadrupole, and other second moments have been determined at the equilibrium structures of the halogen azides, isocyanates, and isothiocyanates, for both principal axes and inertial axes. The theoretical procedures used are Möller–Plesset (MP2) and DFT (B3LYP) methodologies, with TZVP and cc-pVTZ basis sets. There is systematic variation in the calculated directions of the dipole moments in the present series, where B3LYP and MP2 methodologies show differences up to ∼20° for the directions. This discrepancy is largest in ClN3, but quite significant for several other compounds, such as XNCO (where X = Cl, Br and I). The dipole moments of the compounds rotate through a wide angle, as the halogen changes; in contrast, the axes of the second moments rotate to a much smaller degree. The properties are compared with the limited microwave spectral data so far available, in the hope that the present study will encourage further experimental study. There is an urgent need for new experimental data on the dipole moment a,b-components for these compounds. 相似文献
998.
An atom-efficient and environmentally friendly approach to the synthesis of 2,5-disubstituted-1,3,4-thidiazine derivatives has been developed. These compounds were synthesized by a reaction of 2-(2-bromoacetyl)benzofuran and thiocarbohydrazide with various aryl aldehydes, acetylacetones, and pthalic anhydrides in good yields. The advantages of this methodology are mild reaction conditions, easy workup procedure, clean reaction profile, shorter reaction time, and a wide range of substrate applicability. The structures of all synthesized compounds were confirmed from their analytical and spectral data. 相似文献
999.
Potentiostatic Electrochemical Preparation of Bismuth Nanoribbons and its Application in Biologically Poisoning Lead and Cadmium Heavy Metal Ions Detection
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Rajkumar Devasenathipathy Raj Karthik Shen‐Ming Chen Veerappan Mani V. S. Vasantha M. Ajmal Ali Mohamed S. Elshikh Bih‐Show Lou Fahad M. A. Al‐Hemaid 《Electroanalysis》2015,27(10):2341-2346
A simple and elegant electrochemical potentiostatic method has been described for the preparation of highly stable and electrocatalytically active bismuth nanoribbons (BiNRs). The average length and width of the BiNRs were of 100±50 nm and 10±5 µm, respectively. Here, disodium ethylene diamine tetraacetate was employed as a scaffold for the growth of BiNRs. The formation of BiNRs was confirmed by surface morphological, elemental and cyclic voltammetric analyses. The BiNRs exhibited excellent electrocatalytic ability in detecting biologically poisoning heavy metal ions such as lead and cadmium. The described BiNRs based sensor presents good linear dependence on lead and cadmium ions in the concentration range of 1–50 µg/L for both metal ions with a detection limit of 0.104 µg/L for lead and 0.145 µg/L for cadmium. 相似文献
1000.
Hem Raj Khatri Hai Nguyen James K. Dunaway Prof. Dr. Jianglong Zhu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(39):13553-13557
The first total synthesis of derhodinosylurdamycin A, an angucycline antitumor antibiotic, has been described. The synthesis features a Hauser annulation followed by pinacol coupling to construct the tetracyclic angular aglycon, a Stille coupling of glycal stannane and tetracyclic aryliodide followed by stereoselective reduction to afford the 2‐deoxy β‐C‐arylglycoside, and a late‐stage stereoselective glycosylation for the preparation of derhodinosylurdamycin A. This synthetic strategy should be amenable to the chemical synthesis of analogs of derhodinosylurdamycin A bearing diverse 2‐deoxy sugar subunits for structure and activity relationship studies. 相似文献