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51.
Extraction of nitric, perchloric, and hydrochloric acid by N,N-dibutyl diethyl carbamyl phosphonate in carbon tetrachloride was investigated. The data obtained are treated in terms of stepwise neutralization of the acid with the formation of species y · HA and y · 2HA in the organic phase, where y stands for the extractant and HA for the acid. The equilibrium constants, K?1 and K?2 for nitric acid were found to equal 0.24 ± 0.02 and 0.017 ± 0.005, respectively. In case of HClO4 and HCl K?1 were found to equal 0.031 ± 0.003 and 0.0039 ± 0.0005, respectively. A third phase was observed when extraction of HClO4 was performed using acid concentration higher than 3.5 molar. The preference for partition of different acids was discussed on the light of the competition of the proton between the acid anion, water and the basic extractant as well as the degree of the ionization of different acids. 相似文献
52.
N. M. Hassan K. Adu-Wusu J. C. Marra 《Journal of Radioanalytical and Nuclear Chemistry》2005,262(3):579-586
Batch equilibrium measurements were conducted at 25±2 °C with a granular resorcinol-formaldehyde (RF) resin to determine the distribution coefficients (K
d
) for cesium. In the tests, Hanford Site actual waste sample containing radioactive cesium (137Cs) and a pretreated waste sample that was spiked with non-radioactive 133Cs were used. Initial concentrations of non-radioactive cesium in the waste sample were varied to generate an equilibrium isotherm for cesium. Majority of the tests were conducted at 25±2 °C using a liquid to solid phase ratio of 100 ml/g and at a contact time of 72 hours. Two additional tests were conducted at a liquid to solid phase ratio of 10 and at contact time of 120 hours. The measured distribution coefficient (K
d
) for radioactive cesium (137Cs) was 948 ml/g, the K
d
for non-radioactive cesium (133Cs) was 1039 ml/g. The K
d
for nonradioactive cesium decreased from 1039 to 691 ml/g with increased initial cesium concentration from 8 to 64 g/ml. Very little change of the K
d
was observed at initial cesium concentration above 64 g/ml. The maximum sorption capacity for cesium on granular RF resin was 1.17 mmole/g dry resin. This value was calculated from the fit of the equilibrium isotherm data to the Dubinin-Radushkevich equation. Previously, a total capacity of 2.84 mmole/g was calculated by Bibler and Wallace for air-dried RF resin.This work was conducted at the Savannah River Technology Center in Aiken, SC, which is operated for the U. S. Department of Energy (DOE) by Westinghouse Savannah River Company under Contract DE-AC09-96SR18500. The Hanford River Protection Project-Waste Treatment Plant (RPP-WTP) funded this work. The authors are very grateful to Karen Palmer, Betty Mealer, and Yvonne Simpkins for their assistance in the experimental work. 相似文献
53.
Summary Organo phosphorus compounds are decomposed by closed-flask combustion. The phosphate ions produced are then converted to phosphomolybdic acid and extracted withiso- butyl acetate. The 12molybdate ions associated with each original phosphate ion are spectrophotometrically determined by reactions with alkaline hydrogen peroxide, hydrogen peroxide and benzidine and gallic acid. The colours are measured at 450, 400 and 400nm respectively.
This paper is taken from the Master's Thesis of S. A. I. Thoria. 相似文献
Zusammenfassung Organische Phosphorverbindungen werden im Schöniger-Kolben mineralisiert. Das Phosphat wird zu Phosphormolybdänsäure umgesetzt, miti-Butylacetat extrahiert und dann spektrophotometrisch bestimmt. Dazu bedient man sich der Reaktionen mit alkalischem Wasserstoffperoxid, mit Wasserstoffperoxid und Benzidin oder mit Gallussäure. Die Messungen erfolgen bei 450 nm im ersten Fall, bei 400 nm im Fall der beiden letztgenannten Farbreaktionen.
This paper is taken from the Master's Thesis of S. A. I. Thoria. 相似文献
54.
Kariuki NN Luo J Maye MM Hassan SA Menard T Naslund HR Lin Y Wang C Engelhard MH Zhong CJ 《Langmuir : the ACS journal of surfaces and colloids》2004,20(25):11240-11246
This paper reports findings of an investigation of the synthesis of monolayer-capped binary gold-silver (AuAg) bimetallic nanoparticles that is aimed at understanding the control factors governing the formation of the bimetallic compositions. The synthesis of alkanethiolate-capped AuAg nanoparticles was carried out using two related synthetic protocols using aqueous sodium borohydride as a reducing agent. One involves a two-phase reduction of AuCl(4)(-), which is dissolved in organic solution, and Ag(+), which is dissolved in aqueous solution. The other protocol involves a two-phase reduction of AuCl(4)(-) and AgBr(2)(-), both of which are dissolved in the same organic solution. AuAg nanoparticles of 2-3 nm core sizes with different compositions in the range of 0-100% Au have been synthesized. The two synthetic routes were compared in terms of bimetallic composition and size properties. Our new findings have allowed us to establish the correlation between synthetic feeding of metals and metal compositions in the bimetallic nanoparticles, which have important implications to the exploration of gold-based bimetallic nanoparticles for constructing sensing and catalytic nanomaterials. 相似文献
55.
Hassan Rabaâ Bernd Engels Thomas Hupp A. Stephen K. Hashmi 《International journal of quantum chemistry》2007,107(2):359-365
A general scheme for the endo‐ and exo‐cyclization of furan reactivity with [L ‐AuIII, IClx] with (x = 3, 1 and L ‐acetylene and vinylidene) complexes is investigated using density functional theory (DFT) code. Two conceivable mechanisms via a [4 + 2] Diels–Alder process or carbene complex are analyzed. According to the activation energy values of the gold (III and I) catalyst, the first mechanism, which implies the Diels–Alder reaction of AuIII, is thermodynamically favored and gives more evidence of the intramolecular addition of the furan with the alkynes. The second mechanism, presumably assisted by the spontaneous formation of the exo‐vinylidene complexes and intermediates of gold (III, I) by forming the carbene complex, is kinetically favored. Additionally, we compare our results with other structures with intramolecular additions that exhibit the quasi‐similarity of gold analogue structures. Differences in activation energies are observed, according to the functional used. Finally, we probe the solvent effects, which decrease the energy barrier in the path. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 相似文献
56.
Alcaide B Almendros P Alonso JM Aly MF 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(14):3415-3426
Imines derived from 4-oxoazetidine-2-carbaldehydes have been found to be versatile Diels-Alder reagents in that they exhibit two reactivity patterns. 2-Azetidinone-tethered imines undergo diastereoselective reaction with Danishefsky's diene in the presence of different Lewis acids. The effect of the amount of catalyst on the conversion rate as well as on the product ratio has been studied. Under standard reaction conditions, indium(III) chloride and zinc(II) iodide provided the best yields, and indium(III) triflate the highest diastereoselectivity in the Lewis acid promoted aza-Diels-Alder cycloaddition. Treatment of the aforementioned imines with cyclopentadiene, 2,3-dimethyl-1,3-butadiene or 3,4-dihydro-2 H-pyran led to cycloadducts arising from inverse electron-demand condensation involving the beta-lactam-tethered aryl imine as the heterodiene component. In addition, the first methodology for preparing indolizidines from beta-lactams has been developed. This process involves amide bond cleavage of the beta-lactam ring in the aza-Diels-Alder cycloadducts with concomitant cyclization. Full chirality transfer occurs when the reaction is performed with an enantiomerically pure substrate. 相似文献
57.
A new route has been developed for the micro-determination of227Ac in geological materials by neutron activation. The method is based on intense neutron irradiation of the analysed samples followed by separation and α-spectrometric determination of228Th, the β-decay product of the 6.1 hrs228Ac isotope formed. Two alternatives are considered for analysis related to the origin of the analysed matrix. The high sensitivity of the method is documented by the determination of 10?17 g227Ac/g sample. The method is successfully applied for age determination of five uranium containing materials and old uranium glass from Bohemia, CSSR. 相似文献
58.
Hood BL Lucas DA Kim G Chan KC Blonder J Issaq HJ Veenstra TD Conrads TP Pollet I Karsan A 《Journal of the American Society for Mass Spectrometry》2005,16(8):1221-1230
With advancements in the analytical technologies and methodologies in proteomics, there is great interest in biomarker discovery in biofluids such as serum and plasma. Current hypotheses suggest that the low molecular weight (LMW) serum proteome possesses an archive of clipped and cleaved protein fragments that may provide insight into disease development. Though these biofluids represent attractive samples from which new and more accurate disease biomarkers may be found, the intrinsic person-to-person variability in these samples complicates their discovery. Mice are one of the most extensively used animal models for studying human disease because they represent a highly controllable experimental model system. In this study, the LMW serum proteome was compared between xenografted tumor-bearing mice and control mice by differential labeling utilizing trypsin-mediated incorporation of the stable isotope of oxygen, 18O. The digestates were combined, fractionated by strong cation exchange chromatography, and analyzed by nanoflow reversed-phase liquid chromatography coupled online with tandem mass spectrometry, resulting in the identification of 6003 proteins identified by at least a single, fully tryptic peptide. Almost 1650 proteins were identified and quantitated by two or more fully tryptic peptides. The methodology adopted in this work provides the means for future quantitative measurements in comparative animal models of disease and in human disease cohorts. 相似文献
59.
Synergistic extraction of samarium with TTA(HA) and TPPO or TOPO (B) mixtures were investigated. The extracted complex was proved to have the general formula SmA3 · 2B. A graphical determination for the formation constants of these complexes gave the values 3.9 × 1013 and 8.2 × 1010 for SmA3 · 2TOPO and SmA3 · 2TPPO in benzene, respectively. 相似文献
60.
R. Shabana S. M. Khalifa S. Abdalla H. F. Aly 《Journal of Radioanalytical and Nuclear Chemistry》1986,106(1):55-63
Extraction of WO
4
2–
and ReO
4
–
by Adogen-381, tricaprylmethylammonium chloride, Hyamine 10-X, trioctylphosphine oxide or dibenzylsulphoxide in xylene from HNO3, HCl or H2SO4 acid medium was investigated. Based on the separation factors obtained, the separation of ReO
4
–
from WO
4
2–
was elucidated. ReO
4
–
was separated from WO
4
2–
in high radiochemical purity: >99.9% by three successive extractions and strippings using Adogen-381 from HCl or HNO3 acid medium. 相似文献