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41.
Aliphatic and aromatic 1,3‐dithiane are oxidized to the corresponding carbonyl compounds in good yields under mild conditions by N,N′‐diiodo‐N,N′‐1,2‐ethanediyl‐bis(p‐toluenesulphonamide) [NIBTS] and silver nitrate. 相似文献
42.
Jonathan P. Blitz Nigel T. Lucas Mark G. Humphrey 《Journal of organometallic chemistry》2002,650(1-2):133-140
The 60-electron tetrahedral clusters W2Ir2(μ-L)(CO)8(η5-C5H4Me)2 [L=dppe (2), dppf (3)] have been prepared from reaction between W2Ir2(CO)10(η5-C5H4Me)2 (1) and the corresponding diphosphine in 52 and 66% yields, respectively. A structural study of 2 reveals that three edges of a WIr2 face are spanned by bridging carbonyls, that the iridium-ligated diphosphine coordinates diaxially and that the tungsten-bound methylcyclopentadienyls coordinate axially and apically with respect to the plane of bridging carbonyls. A structural study of 3 reveals that the dppf ligand bridges an Ir---Ir bond which is also spanned by a bridging carbonyl; tungsten-ligated methylcyclopentadienyl ligands and terminal carbonyls result in electronic asymmetry (17e and 19e iridium atoms) in the electron-precise cluster. Both clusters show two reversible one-electron oxidation processes and an irreversible two-electron reduction; the dppf-containing cluster 3 has a further, irreversible, one-electron oxidation process. UV–vis-NIR spectroelectrochemical studies of the 2→2+→22+ progression reveal the appearance of a low-energy transition on oxidation to 2+ which persists on further oxidation to 22+. 相似文献
43.
E MeichelTh Stein J KralikG Rheinwald H Lang 《Journal of organometallic chemistry》2002,649(2):191-198
Treatment of [Ti](Cl)(CCSiMe3) (1) {[Ti]=(η5-C5H5)2Ti} with Ni(CO)4 (2) in a 1:1 molar ratio produces the heterobimetallic early-late transition metal complex {[Ti](Cl)(CCSiMe3)}Ni(CO) (3), which features a low-valent Ni(CO) entity stabilized by a datively bonded Cl and a η2-coordinated Me3SiCC ligand. As side-products [Ti]Cl2 (8) and {[Ti](CCSiMe3)2}Ni(CO) (5) are formed. The latter complex can also be synthesized by the reaction of [Ti](CCSiMe3)2 (4) with equimolar amounts of 2. If 3 is reacted with stoichiometric amounts of P(OR)3 (6a, R=C6H5; 6b, R=C6H4CH3-2; 6c, R=C6H4tBu-2) the bis(alkynyl) titanocene 4, (CO)2Ni[P(OR)3]2 (7a, R=C6H5; 7b, R=C6H4CH3-2; 7c, R=C6H4tBu-2), complex 8, {[Ti](μ,η1:η2-CCSiMe3)}2 (9) along with Me3SiCCCCSiMe3 (10) is produced. A possible mechanism for the formation of these species is presented. The solid-state structure of 7b is reported. Complex 7b crystallizes in the tetragonalic space group P-421c with the following parameters: a=14.852(2), b=14.852(2), c=19.410(4) Å, V=4281.5(12) Å3, Z=4 and ρ=1.271 g cm−3. Mononuclear 7b features a Ni(0) centre in a pseudo-tetrahedral environment, caused by the CO and P(OC6H4CH3-2)3 ligands. 相似文献
44.
The synthesis of acylals from structurally diverse aldehydes has been performed in excellent yields under solvent-free conditions using HClO4-SiO2 as a mild, convenient, reusable, and heterogeneous catalyst. The procedure is operationally simple, environmentally benign and has the advantage of enhanced atom utilization. Furthermore, the catalyst can be recovered simply and reused efficiently a number of times without appreciable loss of activity. 相似文献
45.
Horst Pommer 《Angewandte Chemie (International ed. in English)》1977,16(7):423-429
The effects of a scientific discovery on industrial practice are illustrated with reference to the Wittig reaction. The aim of utilizing the Wittig reaction of linking terpenoid building blocks to give vitamin A and carotenoids on an industrial scale prompted extensive research and development work of a synthetic and chemical engineering nature. The importance of the Wittig reaction and its variants in the synthesis of active compounds and fine chemicals in industrial research is demonstrated in the present article. 相似文献
46.
A highly efficient strategy for Cu(OTf)2 mediated SN2-type nucleophilic ring opening followed by [4+2] cycloaddition reactions of enantiopure 2-phenyl-N-tosylazetidines with various aldehydes and ketones afforded a variety of substituted 1,3-oxazinanes and 1,3-amino alcohols in excellent yields, excellent de and good to excellent ee. The proposed SN2-type mechanism of the cycloaddition reaction is supported by experimental evidence. 相似文献
47.
本文研究了饱和硫化钠溶液对土壤样品中硫化汞的浸取效率(其加标回收率达100%),以及用硝酸和硫化钠溶液对样品中汞的选择性浸取并研究了土壤中硫化汞垂直分布。提出了利用硝酸、饱和硫化钠溶液浸取,由冷原子荧光法选择性测定土壤及河流沉积物中硫化汞的新方法。用该方法对同一样品进行8次测定,其相对标准偏差为7.1%。 相似文献
48.
Static pressure usually increases the transition temperatures of polymers by decreasing their free volume. If the pressurizing medium is soluble in the polymer matrix, the opposing effect of increasing the free volume is possible. Those shifts of transition temperatures were monitored with a medium-pressure Differential Scanning Calorimetry (DSC) device. The influences of sorbed and surrounding gas molecules are demonstrated by changes occurring in the transition temperature regions. The results show the severe plasticizing effect of CO2 on poly(p-phenylene sulphide) (PPS). The glass transition temperature TG and the temperature of crystallization TC are influenced by sorbed gas molecules. They decrease due to sorbed CO2 molecules. Glass transition is lowered, but is difficult to interpret, as relaxation phenomena which diminish with increasing pressure occur during DSC runs. In crystallites no gas solution is usually possible, so that the melting point of PPS is mainly affected by influences other than plasticization. 相似文献
49.
O. V. Shishkin 《Monatshefte für Chemie / Chemical Monthly》1996,127(8-9):883-886
Summary The molecular geometry of 4-oxo derivatives of 1,4-dihydropyridine, 1,4-dihydropyrimidine, 1,4-dihydropyridazine, and 1,4-dihydro-1,3,5-triazine has been calculated by the semi-empirical quantum-chemical AM1 method. It could be shown that the dihydrocycle in these compounds is not conformationally rigid. Changing the angle between the endocyclic double bond planes ±15° causes less than 1 kcal/mol increase of energy.
Konformative Flexibilität von 1,4-Dihydroazin-carbonyl-Derivaten (Kurze Mitt.)
Zusammenfassung Die molekulare Geometrie von 4-Oxo-Derivaten von 1,4-Dihydropyridin, 1,4-Dihydropyrimidin, 1,4-Dihydropyridazin und 1,4-Dihydro-1,3,5-triazin wurde mittels der semiempirischen quantenchemischen AM1-Methode berechnet. Es konnte gezeigt werden, daß der zweifach hydrierte Ring in diesen Verbindungen nicht starr ist. Eine Änderung des Winkels zwischen den Ebenen der endocyclischen Doppelbindungen um ±15° bewirkt eine Energieerhöhung von weniger als 1 kcal/mol.相似文献
50.
Co(acac)2·2H2O efficiently catalyzes SnCl2-mediated Barbier coupling in water between carbonyls, including aromatic, aliphatic and α,β-unsaturated aldehydes, ketones, sugars and allyl bromide to afford the corresponding homoallylic alcohols in high yields. The catalyst was reused for several cycles with consistent activity. 相似文献