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951.
In this paper, 1,2-bis(2-acetamido-6-pyridyl)ethane, receptor 1, having an ethylene spacer is reported to recognise dicarboxylic acids. The binding study in the solution phase is carried out using 1H NMR (1:1) and UV–vis experiments and in the solid phase by single-crystal X-ray analysis. In 1H NMR, the downfield shifts of specific amide protons of receptor 1 in 1:1 complexes of receptor and guest diacids, and in the UV–vis experiment, the appearance of an isosbestic point as well as significant binding constants are observed, which thus unambiguously support the complexation of receptor 1 with dicarboxylic acids in solution. Receptor 2, simple 2-acetamido-6-methylpyridine, has lower binding constants than receptor 1 due to cooperative binding of two pyridine amide groups with two acid groups of diacids. In the solid phase, the ditopic receptor 1 shows a grid-like polymeric hydrogen-bonded network that changes to a polymeric wave-like 1:1 anti-perpendicular network instead of the syn–syn polymeric 1:1 (Goswami, S.; Dey, S.; Fun, H.-K.; Anjum, S.; Rahman, A.-U. Tetrahedron Lett. 2005, 46, 7187–7191), anti–anti polymeric 1:1 (Goswami, S.; Jana, S.; Dey, S.; Razak, I.A.; Fun, H.-K. Supramol. Chem. 2006 , 18, 571–574; Goswami, S.; Jana, S.; Fun, H.-K. Cryst. Eng. Comm. 2008, 10, 507–517; Goswami, S.; Jana, S.; Dey, S.; Sen, D.; Fun, H.-K.; Chantrapromma, S. Tetrahedron 2008, 64, 6426–6433), syn–syn 2:2 (Karle, I.L.; Ranganathan, D.; Haridas, V. J. Am. Chem. Soc. 1997 , 119, 2777–2783) or top–bottom-bound 1:1 (Garcia-Tellado, F.; Goswami, S.; Chang, S.K.; Geib, S.J.; Hamilton, A.D. J. Am. Chem. Soc. 1990 , 112, 7393–7394) co-crystals. 相似文献
952.
Manoj Kumar J. Nagendra babu Vandana Bhalla Navdeep Singh Athwal 《Supramolecular chemistry》2013,25(7):511-516
A new chromogenic receptor based on 1,2-phenylene derivative containing thiourea moieties is synthesized and examined for its anion binding ability by UV–Vis and 1H NMR studies. The results show that the receptor has selective colorimetric sensing of fluoride over all other anions like chloride, bromide, iodide, nitrate, hydrogen sulphate and acetate. 相似文献
953.
In this work a cloud-point extraction has been used for the preconcentration of the trace amounts of titanium after complex formation with morin (2′,3,4′,5,7-pentahydroxyflavone) using Triton X-114 as surfactant. The chemical variables affecting the phase separation and the viscosity affecting the detection by flame atomic absorption spectrometry (FAAS) were optimized. At pH 4.5, preconcentration of 50 mL of sample in the presence of 0.08% Triton X-114 and 1.0 × 10?4 M morin enabled the detection limit (c L = 3S b/m) of 2.9 ng/mL titanium and linear range 0.02–2.0 μg/mL to be achived. The preconcentration factor was 61, and the relative standard deviation was 3.8% for 0.1 μg/mL solution of Ti(IV) by repeated assays (n = 9). The proposed method has been applied to the determination of titanium in well water, spiked water and plant (Haloxylon). 相似文献
954.
955.
Hossein Reza Darabi Abbas Darestani Farahani Mohammad Hashemi Karouei Kioumars Aghapoor Rohoullah Firouzi Rainer Herges 《Supramolecular chemistry》2013,25(9):653-657
A new E,E-stilbenophane was synthesised and characterised. The crystal structure of this cyclophane shows that this molecule has a cup-shaped structure, which hosts a phenyl ring of neighbouring molecule as guest in its cavity with a π–π distance of about 3.7 Å. Moreover, the NMR spectra and theoretical analysis (gauge-independent atomic orbitals (GIAO) and quantum theory of atoms in molecules (QTAIM)) suggest that the silver recognition by E,E-stilbenophane host molecules is based on cation–π interactions in which the π-electrons of the double bonds play a major role. 相似文献
956.
A fundamental concern in the Quantitative Structure-Activity Relationship approach to toxicity evaluation is the generalization of the model over a wide range of compounds. The data driven modelling of toxicity, due to the complex and ill-defined nature of eco-toxicological systems, is an uncertain process. The development of a toxicity predicting model without considering uncertainties may produce a model with a low generalization performance. This study presents a novel approach to toxicity modelling that handles the involved uncertainties using a fuzzy filter, and thus improves the generalization capability of the model. The method is illustrated by considering a data set dealing with the fathead minnow (Pimephales promelas) toxicity of 568 organic compounds. 相似文献
957.
Madhavi N.L. Nalam Akbar Ali G.S. Kiran Kumar Reddy Hong Cao Saima G. Anjum Michael D. Altman Nese Kurt Yilmaz Bruce Tidor Tariq M. Rana Celia A. Schiffer 《Chemistry & biology》2013,20(9):1116-1124
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958.
Adnan J. Al-Rehaily Mohammad S. Ahmad Jamal Mustafa Mai M. Al-Oqail Wafaa H. Hassan Shabana I. Khan Ikhlas A. Khan 《Journal of Saudi Chemical Society》2013,17(1):67-76
Solanopubamine (3β-amino-5α, 22αH, 25βH-solanidan-23β-ol), a steroidal alkaloid was isolated from the alkaloidal fraction of Solanum schimperianum in significant yield. Its structure was established by IR, positive ESI-MS, 1D and 2D NMR. The presence of -3β-NH2 and -23β-OH groups was achieved through methylation, acetylation or coupling with octadecanoic and undec-11-enoic acids to produce six derivatives (2–7). Their structures were confirmed by spectroscopic analyses. Solanopubamine and semi-synthetic analogs are investigated for their in vitro cytotoxicity against a panel of human cancer cell lines and anti-microbial activity. Solanopubamine showed good antifungal activity only against Candida albicans and C. tenuis with MIC of 12.5 μg/mL. Semi-synthesized compounds (2–7) have failed to show anti-tumor and anti-microbial activities. 相似文献
959.
Vikas Verma Kuldeep Singh Ashok Kumar Devinder Kumar 《Journal of Thermal Analysis and Calorimetry》2013,112(1):339-344
The use of unconventional synthesis methods in the formation of CaO·2Al2O3 (CA2) is justified because it reduces the formation temperature of the compound. CA2 is formed by classical method at temperatures above 1,400 °C. The polymeric precursor method allows a significant temperature decrease in CA2 synthesis reaching temperatures of 1,000 °C. This paper deals with CA2 synthesis by “citrate” method which is often presented as Pechini method, starting from a mixture of citric acid, ethylene glycol and calcium, and aluminum nitrates. A method based on the formation of a polymeric precursor was also used, starting from a mixture of acrylic acid and nitrates of calcium and aluminum. The results showed a net difference in favor of samples obtained from acrylic acid, which by annealing at 800 °C for 1 h, contain pure CA2. The samples obtained from citric acid, after annealing at 800 °C are amorphous. After annealing at 900 °C in all samples CA2 is single phase. 相似文献
960.
Mohammad Hossein Keshavarz Somayeh Moradi Bahman Ebrahimi Saatluo Hadi Rahimi Ali Reza Madram 《Journal of Thermal Analysis and Calorimetry》2013,112(3):1453-1463
A novel general method is introduced to predict deflagration temperature of organic energetic compounds containing at least –NNO2, –ONO2, or –CNO2 groups. Deflagration temperature is an important safety parameter in working with dangerous energetic compounds and their environmental problems. It is shown that the contribution of some molecular structure parameters can be used to interpret thermal decomposition of an energetic compound. For 86 energetic materials (corresponding to 102 measured values) with different molecular structures, the new correlation has the root mean square (rms) and the average deviations of 23.8 and 19.0 K, respectively. The new method is also tested for some energetic compounds with complex molecular structures, e.g., two new organic energetic molecules N,N′-bis(1,2,4-triazol-3yl)-4,4′-diamino-2,2′,3,3′,5,5′,6,6′-octanitroazobenzene (BTDAONAB) and 2,4,6-trinitrophloroglucinol. 相似文献