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231.
232.
An attempted reaction of 4‐bromomethylcoumarin with 2‐hydroxy aromatic aldehyde/2‐hydroxy aromatic ketone at room temperature in the presence of a mild base resulted in the formation of cis‐2′,3′‐dihydro‐3‐hydroxybenzofuranylcoumarins by carbanion addition across the carbonyl carbon. 相似文献
233.
Sodium cleaves elemental tellurium, TeX, quantitatively to Te2– 2 and Te2- in anhydrous tetrahydrofuran in the presence of catalytic amounts of naphthalene. Subsequent addition of alkylating agent affords dialkyl tellurides and dialkyl ditellurides in excellent yields. 相似文献
234.
A novel azophenol-quinazoline dyad 1 has been designed, synthesized and demonstrated as an efficient reversible multichannel pH indicator through distinct signalling in aqueous media. Owing to the competence between highly fluorescent quinazoline moiety and a well known fluorescence quencher diazo group, dyad 1 is moderately fluorescent in nature. Under acidic conditions 1 displays diverse fluorogenic changes (blue emission at pH 4.25; green at pH 1.80) while under basic condition (pH 11.80) chromogenic changes were observed. 相似文献
235.
The complexation equilibria of Fe(III) with two buffer families, which are ubiquitous in biological system studies, were studied by potentiometric measurements at a constant ionic strength of I = 0.1 mol·dm?3 NaNO3 in aqueous solutions at 298.15 K. The members of TRIS family are tris(hydroxymethyl)aminomethane (TRIS), N-[tris(hydroxymethyl)methyl]-2-aminoethanesulfonic acid (TES), N-[tris(hydroxymethyl)methyl]-3-aminopropanesulfonic acid (TAPS), N-[tris(hydroxymethyl)methyl]-3-amino-2-hydroxypropanesulfonic acid (TAPSO), and N-tris(hydroxymethyl)methyl-4-aminobutanesulfonic acid (TABS) buffers. The members of morpholine family are 4-morpholineethanesulfonic acid (MES), 4-morpholinepropanesulfonic acid (MOPS), 3-morpholino-2-hydroxypropanesulfonic acid (MOPSO), and 4-(N-morpholino) butanesulfonic acid (MOBS) buffers. The overall stability constants were determined from pH-metric data using the least-squares curve-fitting program HYPERQUAD 2008. Based on the best-fit results, the species formed at equilibrium are ML, ML2, ML2H?1, and ML3 in the systems with TRIS family buffers. The complex species ML, ML2, ML2H?1, and MLH?1 are formed in the MOPSO-containing system, while ML, ML2, and ML2H?1 are formed in the systems with MES, MOPS, and MOBS. The stabilities of the complexes fall in the order TABS > TRIS > TAPS > TAPSO > TES and MOBS > MOPS > MOPSO > MES for the TRIS family and morpholine families, respectively. 相似文献
236.
The increasing accumulation of poly(ethylene terephthalate) polymer and poor recycle/disposal practices have made them omnipresent and a major culprit for environmental pollution. Currently global research efforts are focused on primary and secondary recycling of PET waste or through landfills. Chemical recycling of PET through hydrolytic or aminolytic route has been attempted by many researchers however with limited end applications. In our investigations we have used PET waste as a synthon and chemically converted it through a new non-catalytic route into several benzamide derivatives. We have successfully tested them for antistripping performance in bitumen. Our results as elaborated in the paper indicate a comparable performance of the new chemistry products based on PET, to commercially used antistripping chemicals. Our research work thus opens a new route for the recycling of used PET in bituminous concrete roads which may help in alleviating a major environmental problem and disposal of waste PET polymer in large scale. 相似文献
237.
A. Mohammad R. Gupta Nazrul Haq Mu. Naushad G. E. El-Desoky 《Journal of Dispersion Science and Technology》2013,34(8):1179-1184
Aqueous ethylene glycol (ethane 1,2 diol) as a green mobile phase has been used for thin layer chromatographic (TLC) studies of cationic surfactants on alumina layers. Nineteen solvent systems were used to examine the mobility of the surfactants and to discover the best TLC system for the selective separation of dodecyl trimethylammonium bromide (DTAB) from multi-component mixture of other surfactants. Among the TLC systems studied, M3 (ethylene glycol: water, 8:2) was best for achieving the selective separation of DTAB from multi-component mixture of other surfactants because in this mobile phase mobility of all surfactants except DTAB were insignificant. Effect of organic additives in aqueous ethylene glycol mobile phase on the mobility of surfactants was examined. The results obtained on laboratory made alumina TLC plates and commercially available precoated alumina HPTLC plates were compared. The lower limits of detection of DTAB, CPC, CTAB, HDTAC, and TTAB were 0.02, 0.05, 0.04, 0.06, or 0.08 µg per zone respectively. The resolution of mixture of cationic surfactants was also examined in the presence metal cations as an impurity in the analyzed sample. 相似文献
238.
Abstract The concentrations of heavy metals in agricultural soils are increasing gradually from various diffuse sources. The metals can transfer from contaminated soils into the growing plants or may affect the respiration rate of soil microorganisms. In the first part of this paper, the following simple model to predict the biorelevant metal concentration in anthropogenically or artificially contaminated soils is reported: log Mp = α + β log [MNaNO3] log MR = α' + β' log [MNaNO3] log MP = log Metal concentration in test plant (mg/kg dry weight) log MR = log percent Redution in the respiration or enzyme activity [MNaNO3] = Metal concentration in NaNO3-soil extract (mg/kg soil) α and β & α' + β' = Intercepts and slopes of the linear regression lines. The model has been tested in laboratory experiments, in growth experiments either in a greenhouse or in the field. Also, an attempt is made to present a theoretical interpretation. Critical concentrations are calculated with the help of the relationship between metal concentration in soil solution [MNaNO3] and metal concentration in plants. The critical concentration, which is able to induce either phyto- or zootoxic concentrations in the plant parts (productive or vegetative) or reduce their growth or to reduce significantly the growth of soil microorganisms, are found to be uniform in a wide range of soils (pH 3 to 8 and CEC 10–50 millimol/100g soil), the critical concentrations of NaNO3 in soil extracts are comparable with the values obtained with plant growth experiments in nutrient solution and also with the concentrations obtained from soil respiration experiments reported in literature. 相似文献
239.
Dr. Manivannan Ethirajan Dr. Ping Chen Dr. Tymish Y. Ohulchanskyy Dr. Lalit N. Goswami Dr. Anurag Gupta Dr. Avinash Srivatsan Dr. Mahabeer P. Dobhal Joseph R. Missert Prof. Paras N. Prasad Prof. Karl M. Kadish Prof. Ravindra K. Pandey 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(21):6670-6684
We report herein a simple and efficient approach to the synthesis of a variety of meso‐substituted purpurinimides. The reaction of meso ‐ substituted purpurinimide with N‐bromosuccinimide regioselectively introduced a bromo functionality at the 20‐position, which on further reaction with a variety of boronic acids under Suzuki reaction conditions yielded the corresponding meso‐substituted analogues. Interestingly, the free base and the metalated analogues showed remarkable differences in photosensitizing efficacy (PDT) and tumor‐imaging ability. For example, the free‐base conjugate showed significant in vitro PDT efficacy, but limited tumor avidity in mice bearing tumors, whereas the corresponding NiII derivative did not produce any cell kill, but showed excellent tumor‐imaging ability at a dose of 0.3 μmol kg?1 at 24, 48, and 72 h post‐injection. The limited PDT efficacy of the NiII analogue could be due to its inability to produce singlet oxygen, a key cytotoxic agent required for cell kill in PDT. Based on electrochemical and spectroelectrochemical data in DMSO, the first one‐electron oxidation (0.52 V vs. SCE) and the first one‐electron reduction (?0.57–0.67 V vs. SCE) of both the free base and the corresponding NiII conjugates are centered on the cyanine dye, whereas the second one‐electron reduction (?0.81 V vs. SCE) of the two conjugates is assigned to the purpurinimide part of the molecule. Reduction of the cyanine dye unit is facile and occurs prior to reduction of the purpurinimide group, which suggests that the cyanine dye unit as an oxidant could be the driving force for quenching of the excited triplet state of the molecules. An interaction between the cyanine dye and the purpurinimide group is clearly observed in the free‐base conjugate, which compares with a negligible interaction between the two functional groups in the NiII conjugate. As a result, the larger HOMO–LUMO gap of the free‐base conjugate and the corresponding smaller quenching constant is a reason to decrease the intramolecular quenching process and increase the production of singlet oxygen to some degree. 相似文献
240.
Results in Mathematics - The link operator $${P_{\alpha}^\rho(f,x)=\sum_{k=1}^\infty s_{\alpha,k}(x)\int_0^\infty \theta_{\alpha,k}^\rho(t)f(t)dt+e^{-\alpha x}f(0)}$$ , $${\alpha, \rho >... 相似文献