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621.
Rao YK Damu AG Rao AJ Venkatesan S Kuo PC Rao CV Wu TS 《Chemical & pharmaceutical bulletin》2003,51(12):1374-1376
Phytochemical investigation of the whole plant of Andrographis viscosula has led to the isolation of three new 2'-oxygenated flavonoids, (2R)-5-hydroxy-7,2',3'-trimethoxyflavanone (1), 7,2',5'-trimethoxyflavone (2), 5,7,2',3'-tetramethoxyflavone (3), and eight known flavones, 5,7,2'-trimethoxyflavone (4), 5,7,2',4',5'-pentamethoxyflavone (5), echioidinin (6), 5,2',6'-trihydroxy-7-methoxyflavone (7), 5-hydroxy-7,2'-dimethoxyflavone (8), echioidin (9), echioidinin 5-O-glucoside (10), and 5,2',6'-trihydroxy-7-methoxyflavone 2'-O-glucoside (11). The structures of 1-11 were elucidated by physical and spectral methods, including extensive 2D NMR studies. The presence of 2'-oxygenated flavonoids is apparently restricted to Andrographis species in Acanthaceae. Therefore, 2'-oxygenated flavonoids are regarded as chemotaxonomic markers of Andrographis genus in the Acanthaceae family. 相似文献
622.
Uranium–cerium mixed oxides of three different compositions (U0.2Ce0.8)O2, (U0.5Ce0.5)O2 and (U0.8Ce0.2)O2, were prepared by combustion synthesis and characterized by XRD. The compositional characterization was done by ICP-AES. Heat capacity measurements employed a heat flux type differential scanning calorimeter from 280 to 820 K. The heat capacity values of (U0.2Ce0.8)O2, (U0.5Ce0.5)O2 and (U0.8Ce0.2)O2 at 298 K are 62.8, 64.2 and 70.1 J K−1 mol−1, respectively. Enthalpy increment, entropy and Gibbs energy function were computed from the heat capacity data. 相似文献
623.
Ahmed Kamal B. Rajendra Prasad A. Venkata Ramana A. Hari Babu K. Srinivasa Reddy 《Tetrahedron letters》2004,45(17):3507-3509
The tetrahydroquinoline moiety is an important structural component of a number of natural products. The reaction of aryl azides with 3,4-dihydro-2H-pyran in the presence of FeCl3-NaI affords the corresponding tetrahydroquinoline derivatives in an efficient manner. Most of the cyclizations exhibited cis selectivity. 相似文献
624.
Gowravaram Sabitha Chittapragada Maruthi ErigalaVenkata Reddy Chitti Srinivas JhilluS. Yadav SamitK. Dutta AjitC. Kunwar 《Helvetica chimica acta》2006,89(11):2728-2731
A novel, efficient synthesis of a series of functionalized, benzo‐annelated decahydrofuro[3,2‐h][1,6]naphthyridine derivatives 3 has been achieved. The protocol is based on the intramolecular hetero‐Diels–Alder (IMHDA) reaction of in situ formed imines derived from an N‐prenylated sugar aldehyde 1 and different aromatic amines 2 in the presence of bismuth(III) chloride as catalyst. The reactions could be run under very mild conditions at room temperature, and were complete within 30 min, affording exclusively and stereoselectively the corresponding trans‐fused products 3 in good‐to‐excellent yields (Table). 相似文献
625.
Oligonucleotides containing the 5‐substituted 2′‐deoxyuridines 1b or 1d bearing side chains with terminal C?C bonds are described, and their duplex stability is compared with oligonucleotides containing the 5‐alkynyl compounds 1a or 1c with only one nonterminal C?C bond in the side chain. For this, 5‐iodo‐2′‐deoxyuridine ( 3 ) and diynes or alkynes were employed as starting materials in the Sonogashira cross‐coupling reaction (Scheme 1). Phosphoramidites 2b – d were prepared (Scheme 3) and used as building blocks in solid‐phase synthesis. Tm Measurements demonstrated that DNA duplexes containing the octa‐1,7‐diynyl side chain or a diprop‐2‐ynyl ether residue, i.e., containing 1b or 1d , are more stable than those containing only one triple bond, i.e., 1a or 1c (Table 3). The diyne‐modified nucleosides were employed in further functionalization reactions by using the protocol of the CuI‐catalyzed Huisgen–Meldal–Sharpless [2+3] cycloaddition (‘click chemistry’) (Scheme 2). An aliphatic azide, i. e., 3′‐azido‐3′‐deoxythymidine (AZT; 4 ), as well as the aromatic azido compound 5 were linked to the terminal alkyne group resulting in 1H‐1,2,3‐triazole‐modified derivatives 6 and 7 , respectively (Scheme 2), of which 6 forms a stable duplex DNA (Table 3). The Husigen–Meldal–Sharpless cycloaddition was also performed with oligonucleotides (Schemes 4 and 5). 相似文献
626.
Synthetic studies of analogues of cytidine monophosphate (CMP)-sialic acid as transition state mimics for sialylation are reported, applying selective monohydrolysis of a symmetric diester and a subsequent buffer-mediated regio- and stereospecific rearrangement we reported earlier. 相似文献
627.
Ramesh B. Sadanand D. Thomas Reddy S. Gopikanth Venkata Swamy K. Saiprakash P. K. 《Transition Metal Chemistry》2000,25(6):639-643
Hydrogenation of 1-hexene, 1-heptene and 1-octene was carried out using anchored montmorillonitebipyridinepalladium(II) acetate (CI), montmorillonitebipyridinepalladium(II) chloride (CII) and montmorillonitediphenylphosphinopalladium(II) chloride (CIII) in THF. Under the reaction conditions 100% saturation of the carbon–carbon double bond was observed. The observed rates were first order with respect to the partial pressure of hydrogen and fractional order with respect to [substrate] and [catalyst]. The hydrogenation rates were found to be: 1-hexene > 1-heptene > 1-octene for all three catalysts. The reactivity order of various catalysts is: CI > CII > CIII. Thermodynamic and activation parameters were evaluated. A rate law and a plausible mechanism has been proposed. 相似文献
628.
Vijay Kumar Reddy Avula Venkata Ramaiah Chintha Swetha Vallela Jaya Shree Anireddy Naga Raju Chamarthi Rajendra Wudayagiri 《Journal of heterocyclic chemistry》2019,56(1):209-217
An efficient method has been developed for the synthesis of N‐alkylated 2′‐oxo‐3‐phenylspiro[cyclopropane‐1,3′‐indoline]‐2,2‐dicarbonitrile from 3‐chloroindolin‐2‐one and 2‐benzylidenemalononitrile by using triethylamine as a base at room temperature and obtained the products in moderate to good yields. In extension, the scope of the reaction has been investigated by stepwise and one‐pot methods. Furthermore, in silico antibacterial activity was carried out in order to understand possible binding modes of novel derivatives with the active site of DNA gyrase A enzyme, and the results were well complemented. Additionally, absorption, distribution, metabolism, and excretion properties of compounds have shown drug likeness with good oral absorption and moderate blood–brain barrier permeability. 相似文献
629.
Suresh Narva Surendar Chitti Suresh Amaroju Sridhar Goud Mallika Alvala Debanjan Bhattacharjee Nishant Jain Chandra Sekhar Kondapalli Venkata Gowri 《Journal of heterocyclic chemistry》2019,56(2):520-532
A series of 28 novel 2‐(4‐aminophenyl)benzothiazole analogues have been synthesized and characterized using various analytical techniques like 1H NMR, 13C NMR, electrospray ionization mass spectrometry, and IR and bioevaluated for their antiproliferative activity over a group of three human cancer cell lines, namely, lung cancer (A549), cervical cancer (HeLa), and breast cancer (MDA‐MB‐231), using sulforhodamine B assay method. Few synthesized molecules ( 5a , 5c , 5d , 5f , 7b , and 7j ) displayed effective growth inhibition (GI50) activity against the tested human cancer cell lines at lower micromolar concentration (GI50) values in the range 0.2–1.7 μM. Noticeably, compound 7b exhibited reasonable activity in all three cancer cell lines in the GI50 range 0.55–1.2 μM. Further, when 7b was screened for tubulin polymerization inhibition, it exhibited more than 55% inhibition at concentration of 5.0 μM. The molecular docking simulations supported the molecular interactions of the derivatives with the targeted receptor. These derivatives may serve as lead structures for development of potential anticancer drug candidates, and 7b might act as a potential microtubule polymerization inhibitor. 相似文献
630.
Ramakrishnam Raju Addada Venkata Reddy Regalla Sivarami Reddy Gangireddy Venkata Venkata Naresh Vema Venkateswara Rao Anna 《Journal of heterocyclic chemistry》2019,56(3):815-817
A stereoselective total synthesis of parvistone C, an oxygenated natural styryllactone, has been accomplished in excellent overall yield by employing asymmetric aldol reaction, asymmetric epoxidation and regioselective epoxide ring opening as the key steps. Our synthetic strategy is very simple, concise and no use of protecting groups. 相似文献