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排序方式: 共有3567条查询结果,搜索用时 31 毫秒
931.
Mohammad Reza Ganjali Simindokht Shirvani-Arani Parviz Norouzi Morteza Rezapour Masoud Salavati-Niasari 《Mikrochimica acta》2004,146(1):35-41
A novel PVC-based membrane sensor based on the Co(II)-salophen complex (CSC) is described. The electrode revealed a Nernstian response over a wide nitrite ion concentration range (1.0×10–6–1.0×10–1M). The detection limit of the sensor is 8.0×10–7M. The best performance was obtained with a membrane composition of 33% PVC, 61% ortho-nitrophenyloctyl ether, 3% cobalt(II)-salophen, and 3% hexadecyltrimethylammonium bromide. The potentiometric response of the sensor is independent of the pH of solution in the pH range 4.5–11.9. The electrode exhibits a very fast response time and good selectivity over a variety of common inorganic and organic anions, including fluoride, bromide, iodide, sulfite, nitrate, thiocyanate, thriiodide and perchlorate. The selectivity behavior of the proposed sensor shows substantial improvements compared to the previously reported electrodes for nitrite ion. The membrane sensor can be used for at least 2 months without any divergence in potential. The electrode was successfully applied to the monitoring of nitrite ion in water, sausage, flour, wheat, cheese and milk. 相似文献
932.
The electrochemical properties of hydrazine studied at the surface of a carbon paste electrode spiked with p‐bromanil (tetrabromo‐p‐benzoquinone) using cyclic voltammetry (CV), double potential‐step chronoamperometry and differential pulse voltammetry (DPV) in aqueous media. The results show this quinone derivative modified carbon paste electrode, can catalyze the hydrazine oxidation in an aqueous buffered solution. It has been found that under the optimum conditions (pH 10.00), the oxidation of hydrazine at the surface of this carbon paste modified electrode occurs at a potential of about 550 mV less positive than that of a bar carbon paste electrode. The electrocatalytic oxidation peak current of hydrazine showed a linear dependent on the hydrazine concentrations and linear analytical curves were obtained in the ranges of 6.00×10?5 M–8.00×10?3 M and 7.00×10?6 M–8.00×10?4 M of hydrazine concentration with CV and differential pulse voltammetry (DPV) methods, respectively. The detection limits (3σ) were determined as 3.6×10?5 M and 5.2×10?6 M by CV and DPV methods. This method was also used for the determination of hydrazine in the real sample (waste water of the Mazandaran wood and paper factory) by standard addition method. 相似文献
933.
The electrochemical behavior of L ‐cysteine studied at the surface of ferrocenedicarboxylic acid modified carbon paste electrode (FDCMCPE) in aqueous media using cyclic voltammetry, differential pulse voltammetry and double potential step chronoamperometry. It has been found that under optimum condition (pH 8.00) in cyclic voltammetry, the oxidation of L ‐cysteine occurs at a potential about 200 mV less positive than that of an unmodified carbon paste electrode. The kinetic parameters such as electron transfer coefficient, α, and catalytic reaction rate constant, kh were also determined using electrochemical approaches. The electrocatalytic oxidation peak current of L ‐cysteine showed a linear dependent on the L ‐cysteine concentration and linear analytical curves were obtained in the ranges of 3.0×10?5 M–2.2×10?3 M and 1.5×10?5 M–3.2×10?3 M of L ‐cysteine concentration with cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods respectively. The detection limits (3σ) were determined as 2.6×10?5 M and 1.4×10?6 M by CV and DPV methods. 相似文献
934.
Hai-Feng Ji Robert L. Hettich Gilbert M. Brown Reza Dabestani 《Photochemistry and photobiology》1999,70(6):882-886
We have synthesized two derivatives of alkylanthracene covalently bonded to 1,3-alternate calix[4]aza-crown-6 at the nitrogen position to study the effect of alkali metal ion complexation on the emission properties of anthracene fluorophore. The mono- and dianthryl-substituted probes are weakly fluorescent because their emission is partially quenched by photoinduced electron transfer (PET) from the nitrogen lone pair to the excited singlet state of anthracene. Upon complexation of alkali metal ions (e.g. K+, Cs+) by the crown moiety, the nitrogen lone pair can no longer participate in the PET process causing an enhancement in the emission of anthracene fluorophore (fluorescent turn on). The maximum fluorescence enhancement observed upon complexation of cesium ions by mono- and dianthryl-substituted calix[4]aza-crown-6 relative to the uncomplexed form was 8.5- and 11.6-fold, respectively. 相似文献
935.
The absolute configuration of decipinone ( 2 ), a myrsinane‐type diterpene ester previously isolated from Euphorbia decipiens, has been determined by NMR study of its axially chiral derivatives (aR)‐ and (aS)‐N‐hydroxy‐2′‐methoxy‐1,1′‐binaphthalene‐2‐carboximidoyl chloride ((aR)‐MBCC ( 3a ) and (aS)‐MBCC ( 3b )). The absolute configurations at C(7) and C(13) of 2 determined were (R) and (S), respectively. Therefore, considering the relative configuration of 2 , the absolute configuration determined was (2S,3S,4R,5R,6R,7R,11S,12R,13S,15R). 相似文献
936.
937.
Ali Khalaj Morteza Pirali Hogatollah Matloubi Reza Dowlatabadi 《Monatshefte für Chemie / Chemical Monthly》2001,132(6):747-752
Summary. Several novel N-(2,3-dihydro-2-oxo-5-phenyl-1H-1,4-benzodiazepin-3-yl)-2-carboxamides were prepared by acyl coupling of 2-aminobenzophenones with α-(benzotriazol-1-yl)-N-acylglycines
followed by displacement of the benzotriazole ring with ammonia and cyclization of the resulting monoacyl aminals. In addition
to high yields and shorter reaction sequences due to avoiding deprotection and acylation of the protected 3-amino-1,4-benzodiazepin-2-one
intermediates, the present approach did not involve the use of toxic and odoriferous materials as is the case with other methods.
Received September 20, 2000. Accepted (revised) November 29, 2000 相似文献
938.
By considering the null space of incidence matrices of trivial designs over GF(2) (the space of 1- (v,k) trades overGF(2)) we obtain families of codes which are optimal for some v and k. Moreover, by generalizing the concept of bond space, the weight enumerator polynomials for these codes are obtained. 相似文献
939.
Shadpour E. Mallakpour Abdol‐Reza Hajipour Mohammad Reza Zamanlou 《Journal of polymer science. Part A, Polymer chemistry》2001,39(1):177-186
3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (4,4′‐carbonyldiphathalic anhydride) was reacted with L ‐leucine in a mixture of acetic acid and pyridine (3 : 2), and the resulting imide‐acid [N,N′‐(4,4′‐carbonyldiphthaloyl)‐bis‐L ‐leucine diacid] was obtained in quantitative yield. The compound was converted to the N,N′‐(4,4′‐carbonyldiphthaloyl)‐bis‐L ‐leucine diacid chloride by reaction with thionyl chloride. A new facile and rapid polycondensation reaction of this diacid chloride with several aromatic diamines such as 4,4′‐diaminodiphenyl methane, 2,4‐diaminotoluene, 4,4′‐sulfonyldianiline, p‐phenylenedi‐amine, 4,4′‐diaminodiphenylether, and m‐phenylenediamine was developed by using a domestic microwave oven in the presence of a small amount of a polar organic medium such as O‐cresol. The polymerization reactions proceeded rapidly compared with the conventional solution polycondensation and were completed within 6 min, producing a series of optically active poly(amide‐imide)s with a high yield and an inherent viscosity of 0.37–0.57 dL/g. All of the above polymers were fully characterized by IR, elemental analyses, and specific rotation. Some structural characterization and physical properties of these optically active poly(amide‐imide)s are reported. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 177–186, 2001 相似文献
940.
Oveisi Ali Reza Karimi Pouya Delarami Hojat Samareh Daliran Saba Khorramabadi-zad Ahmad Khajeh Mostafa Sanchooli Esmael Ghaffari-Moghaddam Mansour 《Molecular diversity》2020,24(2):335-344
Molecular Diversity - New trans-A2B2-porphyrins substituted at phenyl positions were synthesized from 4-methylphthalic acid as a starting material through sequential multistep reactions. These... 相似文献