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991.
Meija J Mester Z D'Ulivo A 《Journal of the American Society for Mass Spectrometry》2006,17(7):1028-1036
Three conceptually different mathematical methods are presented for accurate mass spectrometric determination of H2O/HOD/D2O and H2Se/HDSe/D2Se concentrations from mixtures. These are alternating least-squares, weighted two-band target entropy minimization, and a statistical mass balance model. The otherwise nonmeasurable mass spectra of partially deuterated isotopologues (HOD and HDSe) are mathematically constructed. Any recorded isotopologue mixture mass spectra are then deconvoluted by least-squares into their components. This approach is used to study the H2O/D2O exchange reaction, and is externally validated gravimetrically. The H2O/D2O exchange equilibrium constant is also measured from the deconvoluted 70 eV electron impact GC/MS data (K = 3.85 +/- 0.03). 相似文献
992.
S. I. Lopatin V. L. Stolyarova V. G. Sevast’yanov P. Ya. Nosatenko V. V. Gorskii D. V. Sevast’yanov N. T. Kuznetsov 《Russian Journal of Inorganic Chemistry》2012,57(2):219-225
Silicon evaporation has been investigated by high-temperature mass spectrometry, and the saturation vapor pressure of silicon
over its melt has been determined over the temperature range from 1739 and 2326 K. The saturation vapor pressure data obtained
via silicon evaporation from Knudsen cells made of molybdenum, tungsten, molybdenum disilicide-lined molybdenum, and graphite
silicided by the gas-phase method are compared. Among these materials, silicided graphite is the most inert toward silicon
vapor. The silicon partial pressures measured in the silicided graphite cell are close to the recommended values. 相似文献
993.
A major challenge in the area of DNA detection is the development of rapid methods that do not require polymerase chain reaction
(PCR) amplification of the genetic sample. The PCR amplification step increases the cost of the assay, the complexity of the
detection, and the quantity of DNA required for the assay. In this context, methods that are able to perform DNA analyses
with ultrasensitivity have recently been investigated with the aim of developing new PCR-free detection protocols. Functionalized
gold nanoparticles have played a central role in the development of such methods. Here, possibilities offered by functionalized
gold nanoparticle in the ultrasensitive detection of DNA are discussed. The different functionalization protocols available
for gold nanoparticles and the principal DNA detection methods that are able to detect DNA at the femtomolar to attomolar
level are presented. 相似文献
994.
A. P. Avdeenko S. A. Konovalova O. N. Mikhailichenko S. V. Shelyazhenko V. V. Pirozhenko L. M. Yagupol’skii 《Russian Journal of Organic Chemistry》2012,48(2):221-233
In reactions with sodium sulfinates of N-substituted 1,4-benzoquinone monoimines with the quinoid ring having free positions
2 and/or 6 the fraction of products of 1,4-addition of the sulfinate ion grows in the series ArSO2 → MeSO2 → CF3SO2. In the case of 2,6-dimethyl derivatives the 1,6-addition is preferable, and the amount of products of 6,1-addition decreases. 相似文献
995.
Alexander O. Terent’ev Igor B. Krylov Vera A. Vil’ Zhanna Yu. Pastukhova Sergey A. Fastov Gennady I. Nikishin 《Central European Journal of Chemistry》2012,10(2):360-367
It was found that oximes undergo deoximation in the presence of the H2O2aq-HBraq system to form ketones and bromo ketones. This reaction provided the basis for the synthesis of dibromo ketones in yields
varying from 40% to 94%. This method is environmentally friendly, sustainable, and easy to perform. The results of this investigation
extend the potential of the use of oximes for the protection of carbonyl group, thus offering the ability to perform not only
conventional deoximation but also the subsequent bromination of ketones. The reaction is easily scaled up and dibromo ketones
can be prepared in gram amounts.
相似文献
996.
S. A. Amitina I. V. El’tsov T. V. Rybalova Yu. V. Gatilov I. A. Grigor’v 《Russian Chemical Bulletin》2004,53(8):1700-1703
Reactions of alicyclic 2-hydroxyamino oximes with pentafluorophenylglyoxal afford mixtures of annelated derivatives of 2-pentafluorophenylpyrazine 1,4-dioxide and tetrafluoro- 10H-imidazo[1,2-b][1,2]benzooxazin-10-one. The structures of the latter were established by X-ray diffraction analysis.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1636–1639, August, 2004. 相似文献
997.
V. S. Dutka G. G. Midyana Yu. V. Dutka E. Ya. Pal’chikova 《Russian Journal of General Chemistry》2015,85(12):2703-2709
Thermolysis of lauroyl peroxide in various organic solvents was studied. It was shown that the primary homolytic dissociation of the peroxide group is accompanied by secondary reactions of chain-induced decomposition. The reaction medium affects the rate of both the primary homolytic dissociation and secondary induced decomposition processes. Correlation equations between the rate constants of the reactions in study and the physicochemical parameters of the solvents were proposed. 相似文献
998.
Sergey G. Il’yasov Viktor A. Cherkashin Gennady V. Sakovich Dmitri A. Parkhomenko 《Chemical Papers》2015,69(11):1445-1453
The chemical structures of Miscanthus var. ‘Soranovskii’ lignin fractions released via extraction of lignin from the lignocellulosic feedstock using moderately heated acetone under atmospheric pressure, without acidic and alkaline catalysts, were studied. A blend of Miscanthus stems and leaves was pretreated with water under thermobaric conditions. The acetone organosolv process subsequently afforded a substance related to a lignin-like matter-acetone organosolv Miscanthus lignin (AOML). Non-destructive analytical techniques such as FTIR spectroscopy, gas chromatography-mass spectrometry, size-exclusion chromatography, and 2D NMR were used. The IR and NMR spectroscopies revealed the AOML structure to comprise all the three major types of phenylpropane units: guaiacyl (G), syringyl (S), and p-hydroxyphenyl (H). The resultant acetone-organosolv lignin exhibits good solubility in polar solvents, moderate solubility in aromatic chemicals, and is insoluble in non-polar solvents, exhibiting the physicochemical properties of a thermoplastic polymer with a softening point of 67.0°C (onset 33.0°C, endset 81.5°C). 相似文献
999.
E. V. Kabin V. A. Emel’yanov I. A. Baidina T. I. Nedoseykina V. A. Vorob’yov 《Journal of Structural Chemistry》2010,51(1):73-80
The structure of trans-[RuNO(NH3)4(H2O)](NO3)3 (I) and trans-[RuNO(NH3)4(NO3)](NO3)2 (II) was determined by XRD. Crystallographic data are as follows: space group I41/a; a = b = 18.280(1) Å, c = 15.129(1) Å, R = 0.0244 (I), and space group Cm, a = 11.5620(3) Å, b = 7.9934(2) Å, c = 7.7864(2) Å, β = 127.124(1)°, R = 0.0139 (II). Interatomic distances for complex particles of fac- and mer- [RuNO(NH3)2(NO3)3] (III and IV, respectively) were determined by EXAFS. 相似文献
1000.
Philippe d’Antuono Edith Botek Benoît Champagne Laetitia Maton Dorothée Taziaux Jean-Louis Habib-Jiwan 《Theoretical chemistry accounts》2010,125(3-6):461-470
1H and 13C NMR chemical shifts of coumarin derivatives have been determined using first principles approaches with and without accounting for the effects of the solvent and compared to experiment in order to assess their reliability. Good linear relationships are obtained between theory and experiment, which allows correcting the calculated values for systematic errors. This is particularly the case when using the PCM scheme to model the solvent effects because the δ values larger than 150 ppm are more difficult to reproduce. The final accuracy of the method amounts to about 1 ppm for 13C and 0.05 ppm for 1H. 相似文献