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排序方式: 共有394条查询结果,搜索用时 46 毫秒
101.
Władysław Janusz Svetlana Khalameida Volodymyr Sydorchuk Ewa Skwarek Valery Zazhigalov Jadwiga Skubiszewska-Zięba Roman Leboda 《Adsorption》2010,16(4-5):333-341
Mechanochemical modification of vanadium phosphates doped with Bi, Zr, Mo has been studied. Milled samples have been investigated by means of XRD, DTA-TG, FTIR, nitrogen adsorption, electrokinetic measurements. It was found that phase composition of the phosphates does not change upon the mechanochemical modification process. Milling in water causes formation of porous materials. Modification of surface results in changes of the electrokinetic and adsorption properties of the milled samples. 相似文献
102.
Tosylamino-substituted 2-arylbenzimidazoles have blue or green fluorescence in the crystalline state and in toluene at room temperature. The effect of the substituents on the position of the absorption and fluorescence bands and on the strength of the intramolecular hydrogen bond was investigated. An anomalously large Stokesian shift within the limits 8800–11450 cm¡1 is characteristic for compounds that contain an o-tosylamino group. 相似文献
103.
Jadwiga Walczak Izabella Rychłowska-Himmel Elżbieta Mikos-Nawłatyna 《Journal of Thermal Analysis and Calorimetry》1995,43(2):427-431
The phase equilibria established up to the solidus line in the system Fe2V4O13−WO3, one of the intersections of the three-component system Fe2O3−V2O5−WO3, have been studied. The system appears not to be a real two-component system.
Zusammenfassung Es wurde eine Untersuchung des Phasengleichgewichtes durchgeführt, welches bezüglich der Solidus-Linie im System Fe2V4O13−WO3, einer der Zwischenbereiche im Dreikomponentensystem Fe2O3−V2O5−WO3, nachgewiesen wurde. Dieses System scheint kein echtes Zweikomponentensystem zu sein.相似文献
104.
A simple GF-AAS method for speciation analysis of chromium in mineral waters and salinas was developed. Cr(VI) species were separated from Cr(III) by solid-phase extraction with APDC (ammonium pyrrolidinedithiocarbamate). The APDC complexes were formed in the sample solution under proper conditions, adsorbed on Diaion HP-2MG resin and the resin was separated from the sample. After elution with concentrated nitric acid Cr(VI) was determined by GF-AAS. Total chromium was determined by GF-AAS directly in the sample and Cr(III) concentration was calculated as the difference between those results.
The detection limit of the method defined as 3 s of background variation was 0.03 μg l−1 for Cr(VI) and 0.3 μg l−1 for total chromium. RSD for Cr(VI) determination at the concentration of 0.14 μg l−1 was 9%, and for total chromium at the concentration of 5.6 μg l−1 was 5%. The recovery of Cr(VI) was in the range of 94–100%, dependently on type of the sample.
The investigation of recovery of the spiked Cr(VI) showed that at concentration levels near 1 μg l−1 and lower recovery may be reduced significantly even by pure reagents that seem to be free from any reductants. 相似文献
105.
L. Zalotai T. Turányi T. Bérces F. Márta 《Reaction Kinetics and Catalysis Letters》1993,51(2):401-408
The two-channel thermal decomposition of 1,1,2,2-tetrafluorocyclobutane (TFCB) and 1-methyl-2,2,3,3-tetrafluorocyclobutane (MTFCB) have been studied in the temperature range of 730–805 K at pressures varied from 1.1 Pa up to 4.6 kPa. In the pressure independent range, Arrhenius expressions were obtained for TFCB decomposition into 2 CH2CF2 (k1) and C2H4+C2F4 (k2), respectively. The same kinetic equations were determined for the decomposition of MTFCB into C3H4F2+C2H2F2 (k3) and C3H6+C2F4(k4). From the study of the pressure dependence of the homogeneous decomposition rates, the average downward energy transfer values of 1800±200 cm–1 and 1600±200 cm–1 were obtained for the TFCB and MTFCB molecules, respectively. 相似文献
106.
P. B. Kurapov N. A. Klyuev L. Sh. Afanasiadi I. N. Tur I. I. Grandberg 《Chemistry of Heterocyclic Compounds》1986,22(3):334-339
The electronic absorption and emission spectra in the crystals, solutions, vapor, and ethanol-ether (77 °K) were investigated for the series of 2-(4-pyridyl)-5-aryl-substituted oxazoles at various temperatures. The conjugation between the rings of the system was investigated by mass spectrometry. The combination of spectral data shows that the configurations of such molecules both in the ground state and in the excited state depends substantially on the state of aggregation and on the temperature.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 407–412, March, 1986. 相似文献
107.
Phase equilibria being established in the subsolidus area of the V2O5?Cr2(MoO4)3 system at the whole component concentration range have been studied basing on DTA and X-ray phase powder diffraction. It has been established that the system is not a real two-component system in the subsolidus area. The fact has been proved by the presence of fields in that area, where three solid phases remain in mutual equilibrium. 相似文献
108.
Leboda R Charmas B Skubiszewska-Zieba J Chodorowski S Oleszczuk P Gun'ko VM Pokrovskiy VA 《Journal of colloid and interface science》2005,284(1):39-47
Natural bentonite spent in the process of plant oil bleaching was used as an initial material for preparation of carbon-mineral adsorbents. The spent bleaching earth was treated using four procedures: T (thermal treatment); H (hydrothermal treatment); C (thermal treatment with addition of CCl4 vapor); M (modification of porous structure). Raw bentonite, RB (raw bleaching earth), and carbon materials prepared using plant oil were compared. The physicochemical characteristics of the adsorbents were determined using different methods: nitrogen adsorption/desorption, XRD, TEM, and MS-TPD. Carbon-mineral adsorbents contain from 5.23 to 19.92% C (w/w) and carbon adsorbents include from 84.2 to 91.18% C (w/w). Parallel processes of organic substance carbonization, porous structure modification, sublimation or evaporation of metal chlorides, and removal of hydrogen chloride take place during pyrolysis of waste mineral materials in the CCl4 atmosphere. 相似文献
109.
M. Tur D. Menashe Y. Japha Y. Danziger 《Journal of Optical and Fiber Communications Reports》2007,4(2):110-172
High-Order Mode Dispersion Compensating Modules (HOM-DCM) using spatial optical transformations for mode conversion are reviewed.
It is shown that mode transformers using this technology can be designed to transform the LP01 mode of SMF fibers to the LP02 mode of specially designed dispersion compensating High-Order Mode Fiber (HOMF), with typical insertion loss of ∼1 dB, and
typical extinction ratio to other modes less than -20 dB. The HOMF itself can provide high negative dispersion [typically
in the range of 400-600 ps/(nm km)], and high negative dispersion slope, allowing efficient compensation of all types of transmission
fiber. Combining two mode transformers with HOMF and possibly trim fiber for fine-tuning, results, for example, in a HOM-DCM
that compensates 100 km LEAF? fiber, with Insertion loss < 3.5 dB, and Multi-Path Interference (MPI) < -36 dB. MPI phenomena
in HOM-DCMs is characterized, and shown to comprise both coherent and incoherent parts, and to result from both the mode transformers
and fiber coupling within the HOMF. MPI values of < -36 dB have been shown to allow error free transmission of 10 Gb/s signals
over up to 6000 km. Finally, a number of applications well suited to the properties of HOM-DCMs are reviewed. 相似文献
110.
Tomasz Gubica Jadwiga Stroka Andrzej Temeriusz 《Journal of Physical Organic Chemistry》2007,20(6):375-383
A series of nitrophenyl β‐cyclodextrin derivatives: mono[6‐deoxy‐6‐(4‐nitrobenzamido)]‐per‐ O‐methyl‐β‐cyclodextrin (R1? Ph? NO2), mono[6‐deoxy‐6‐(3‐nitrobenzamido)]‐per‐O‐methyl‐β‐cyclodextrin (R2? Ph? NO2) and heptakis[6‐deoxy‐6‐(4‐nitrobenzamido)‐2,3‐di‐O‐methyl]‐β‐cyclodextrin [R3? (Ph? NO2)7] were synthesized. Purity and composition of the obtained substances were checked. Electroreduction of nitro groups of the new synthesized compounds was investigated on mercury electrode using cyclic voltammetry and chronocoulometry. The parameters of the reduction processes of ? NO2 groups of the investigated compounds were found not to be comparable to the reduction of nitrobenzene under the same experimental conditions. Moreover, the electroreduction of nitro groups in these nitrophenyl derivatives was dependent on pH, the type of the studied compound, and slightly on the solvent composition. All the reactants were strongly adsorbed on mercury electrode. In the case of R3? (Ph? NO2)7, its seven nitro groups were reduced practically at the same potential, and no radical anion formation was observed. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献