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991.
Raft domain reorganization driven by short- and long-chain ceramide: a combined AFM and FCS study 总被引:2,自引:0,他引:2
Chiantia S Kahya N Schwille P 《Langmuir : the ACS journal of surfaces and colloids》2007,23(14):7659-7665
Naturally occurring long-chain ceramides (Cer) are known to alter the lateral organization of biological membranes. In particular, they produce alterations of microdomains that are involved in several cellular processes, ranging from apoptosis to immune response. In order to induce similar biological effects, short-chain Cer are extensively used in in vivo experiments to replace their long-chain analogues. In this work, we used the combined approach of atomic force microscopy (AFM) and fluorescence correlation spectroscopy (FCS) to investigate the effect of Cer chain length in lipid bilayers composed of sphingomyelin, dioleoyl-phosphatidylcholine, and cholesterol. Our results show that only long-chain Cer, like C18 and C16, are able to segregate from the liquid-ordered phase, forming separate Cer-enriched domains. Conversely, short-chain Cer do not form a separate phase but alter the physical properties of the liquid-ordered domains, decreasing their stability and viscosity and perturbing the lipid packing. These differences may contribute to the explanation of the different physiological effects that are often observed for the long- and short-chain Cer. 相似文献
992.
993.
Gruber CC Nestl BM Gross J Hildebrandt P Bornscheuer UT Faber K Kroutil W 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(29):8271-8276
Racemization is the key step to turn a kinetic resolution process into dynamic resolution. A general strategy for racemization under mild reaction conditions by employing stereoselective biocatalysts is presented, in which racemization is achieved by employing a pair of stereocomplementary biocatalysts that reversibly interconvert an sp3 to a sp2 center. The formal interconversion of the enantiomers proceeds via a prochiral sp2 intermediate the formation of which is catalyzed either by two stereocomplementary enzymes or by a single enzyme with low stereoselectivity. By choosing appropriate reaction conditions, the amount of the prochiral intermediate is kept to a minimum. This general strategy, which is applicable to redox enzymes (e.g., by acting on R2CHOH and R2CHNHR groups) and lyase-catalyzed addition-elimination reactions, was proven for the racemization of secondary alcohols by employing alcohol dehydrogenases. Thus, enantiopure chiral alcohols were used as model substrates and were racemized either with highly stereoselective biocatalysts or by using (rarely found) non-selective enzymes. 相似文献
994.
Organometallic Compounds of Copper. XVIII. On the Reaction of the Alkyne Copper(I) Complexes [CuX(S‐Alkyne)] (X = Cl, Br, I; S‐Alkyne = 3,3,6,6‐Tetramethyl‐1‐thiacyclohept‐4‐yne) with the Phosphanes PMe3 and Ph2PCH2CH2PPh2 (dppe) The alkyne copper(I) halide complexes [CuX(S‐Alkyne)]n ( 2 ) ( 2 a : X = Cl, 2 b : X = Br, 2 c : X = I; S‐Alkyne = 3,3,6,6‐tetramethyl‐1‐thiacyclohept‐4‐yne; n = 2, ∞) add the phosphanes PMe3 and Ph2PCH2CH2PPh2 (dppe) to form the mono‐ and dinuclear copper compounds [(S‐Alkyne)CuX(PMe3)] ( 6 ) ( 6 a : X = Cl, 6 b : X = Br) and [(S‐Alkyne)CuX(μ‐dppe)CuX(S‐Alkyne)] ( 7 a : X = Cl, 7 b : X = Br, 7 c : X = I), respectively. By‐product in the reaction of 2 a with dppe is the tetranuclear complex [(S‐Alkyne)Cu(μ‐X)2Cu(μ‐dppe)2Cu(μ‐X)2Cu(S‐Alkyne)] ( 8 ). In case of the compounds 7 prolonged reaction times yield the alkyne‐free dinuclear copper complexes [Cu2X2(dppe)3] ( 9 ) ( 9 a : X = Cl, 9 b : X = Br, 9 c : X = I)). X‐ray diffraction studies were carried out with the new compounds 6 a , 6 b , 7 b , 8 , and 9 c . 相似文献
995.
The reaction of Rb2S3, Ta and S in a 1.3 : 1 : 5.6 molar ratio at 400 °C yields red‐orange crystals of the new ternary compound Rb6Ta4S22 being the first tantalum polysulfide containing the dimeric complex anion [Ta4S22]6–. The polysulfide anions are composed of two Ta2S11 subunits which are linked to Ta4S22 units via terminal sulfur ligands. The Ta5+ centers are coordinated by S22– and S2– ligands according to [(Ta2(μ2‐η2,η1‐S2)3(η2‐S2)(S)2)2(μ2‐η1,η1‐S2)]6–. Every Ta5+ ion is surrounded by seven sulfur ions forming a strongly distorted pentagonal bipyramid. In the crystal structure the discrete [Ta4S22]6– anions are stacked parallel to the crystallographic b‐axis. The Rb+ cations are located between these stacks. Rb6Ta4S22 crystallizes in the monoclinic space group P21/c (No. 14) with a = 11.8253(9) Å, b = 7.9665(4) Å, c = 19.174(2) Å, β = 104.215(9)°, V = 1751.0(2) Å3, Z = 2. 相似文献
996.
Ernst Bayer Petra Gfrrer Claus Rentel 《Angewandte Chemie (International ed. in English)》1999,38(7):992-995
By on-line addition of a central atom (for example, AgI, BIII, PdII, LiI) positively or negatively charged complexes of analytes can be formed for CIS-MS. This technique is applicable to both polar and nonpolar compounds—for example, for alcohols, ethers, and a large number of olefins, polyolefins, and arenes as well as steroids, vitamins of the D and E families, carotinoids, polystyrols, terpenes, and unsaturated fatty acids—and can be readily coupled with separation techniques. 相似文献
997.
Oxalato‐ and Squarato‐Bridged Threedimensional Networks: The Crystal Structures of La2(C2O4)(C4O4)2(H2O)8 · 2.5 H2O and K[Bi(C2O4)2] · 5 H2O The title compounds have been formed by hydrolysis of amino‐ and thioderivatives of squaric acid in the presence of LaIII and BiIII ions. Both compounds are threedimensional coordination polymers in the solid state, as shown by single crystal X‐ray crystallography. In La2(C2O4)(C4O4)2(H2O)8 · 2.5 H2O oxalato‐bridged pairs of LaO9 polyhedra are connected with identical neighbouring polyhedra by squarate ions. In K[Bi(C2O4)2] · 5 H2O each Bi atom is fourfold linked to other Bi atoms by the oxalate ions. The resulting 3D network shows a diamond‐like topology with square‐shaped channels. In both structures the channels are partially filled by water molecules. 相似文献
998.
999.
Gabriella Di Lena Jose Sanchez del Pulgar Massimo Lucarini Alessandra Durazzo Petra Ondrejí
kov Florin Oancea Rodica-Mihaela Frincu Altero Aguzzi Stefano Ferrari Nicoli Irene Casini Paolo Gabrielli Roberto Caproni Igor erve Ginevra Lombardi-Boccia 《Molecules (Basel, Switzerland)》2021,26(22)
Rapeseed meal (RSM), a by-product of oilseed extraction connected to the agri-food and biofuel sectors, is currently used as animal feed and for other low-value purposes. With a biorefinery approach, RSM could be valorized as a source of bio-based molecules for high-value applications. This study provides a chemical characterization of RSM in the perspective of its valorization. A qualitative study of main functional groups by fourier transform infrared (FTIR) spectroscopy was integrated with a chemical characterization of macronutrients, minerals by inductively coupled plasma optical emission spectrometry (ICP-OES), phenolic acids and lipid components by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), HPLC-diode-array detector (HPLC-DAD) and gas chromatography-mass spectrometry/flame ionization detector (GC-MS/FID). The study, conducted on different lots of RSM collected over a one-year period from an oil pressing factory serving a biofuel biorefinery, highlighted a constant quality over time of RSM, characterized by high protein (31–34%), fiber (33–40%) and mineral (5.5–6.8%) contents. Polyphenol extracts showed a significant antioxidant activity and a prevalence of sinapic acid, accounting for more than 85% of total phenolic acids (395–437 mg kg−1 RSM). Results highlight the potentialities of RSM for further valorization strategies that may lead to the creation of new cross-sector interconnections and bio-based value chains with improvement of the economics and sustainability of the bioeconomy sectors involved. 相似文献
1000.
Organometallic Compounds of Copper. XX On the Reaction of the Alkyne Copper(I) Complexes [CuCl(S‐Alkyne)] and [Cu2Br2(S‐Alkyne)(dms)] (S‐Alkyne = 3,3,6,6‐Tetramethyl‐1‐thiacyclohept‐4‐yne; dms = Dimethylsulfide) with the Lithiumorganyls Phenyllithium und Fluorenyllithium The alkyne copper(I) bromide complex [Cu2Br2(S‐Alkyne)(dms)] ( 3 b ) (S‐Alkyne = 3,3,6,6‐tetramethyl‐1‐thiacyclohept‐4‐yne; dms = dimethylsulfide) reacts with phenyllithium to form a tetranuclear copper(I) complex of the composition [Cu4(C6H5)2(S‐Alkenyl)2] ( 7 ) in low yield (4%). The reaction of the alkyne copper(I) chloride complex [CuCl(S‐Alkyne)] ( 2 a ) with fluorenyllithium in tetrahydrofuran (thf) affords a lithium cuprate of the composition [Li(thf)4]+ [Cu2(fluorenyl)3(S‐Alkyne)2]– ( 8 ) (yield 32%). The structures of both new complexes 7 and 8 were determined by X–ray diffraction. 相似文献