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131.
The discovery and design of new materials with competitive optical frequency conversion efficiencies can accelerate the development of scalable photonic quantum technologies. Metal–organic framework (MOF) crystals without inversion symmetry have shown potential for these applications, given their nonlinear optical properties and the combinatorial number of possibilities for MOF self-assembly. In order to accelerate the discovery of MOF materials for quantum optical technologies, scalable computational assessment tools are needed. We develop a multi-scale methodology to study the wavefunction of entangled photon pairs generated by selected non-centrosymmetric MOF crystals via spontaneous parametric down-conversion (SPDC). Starting from an optimized crystal structure, we predict the shape of the G(2) intensity correlation function for coincidence detection of the entangled pairs, produced under conditions of collinear type-I phase matching. The effective nonlinearities and photon pair correlation times obtained are comparable to those available with inorganic crystal standards. Our work thus provides fundamental insights into the structure–property relationships for entangled photon generation with metal–organic frameworks, paving the way for the automated discovery of molecular materials for optical quantum technology.

The discovery and design of new materials with competitive optical frequency conversion efficiencies can accelerate the development of scalable photonic quantum technologies.  相似文献   
132.
Methodological alternatives for the preparation of highly strained, highly pyramidalized dodecahedrene 2 (Estr=87.3 kcal mol?1; ?=43.5°, MM2) and 1,16-dodecahedradiene 3 (Estr=105.3 kcal mol?1; ?=42.9°, MM2) have been explored, protection/deprotection strategies have been tested—with the eye on their utilization for the generation of higher unsaturated dodecahedranes (e.g. 1,4, 16-triene 4, 1,4,10 (14),16-tetraene 5). For the acquisition of preparative quantities of monoene 2 the “P2F” catalyzed cis-β-elimination in bromododecahedrane, of diene 3 the FVP fragmentation of a “twofold protected” precursor (bis-furan adduct) have become the protocols of choice, which both profit from the recent synthetic advances along the pagodane → dodecahedrane scheme. Because of unusually effective steric protection the highly tilted C=C double bonds of 2 (λmax (CH3CN) = 254 nm, ν C=C = 1658 cm?1, δC=C = 164.4) and 3 (δC=C = 170.5) enter into thermal stabilization pathways (dimerization, oligomerization) only at higher temperatures (for 2 ca. 50% consumption after 5 h at 100°C in a 3·10?3 molar toluene solution); extreme sensitivity to oxygen is primarily attributed to kinetically and thermodynamically promoted allylic hydrogen abstraction.  相似文献   
133.
Five polyimide films prepared from 3,3′,4,4′-benzophenone tetracarboxylic acid'dianhydride (BTDA) and diamines, 4,4′-oxydianiline (ODA), 3,3′-diaminobenzophenone (DABP), or 3,3′-diaminodiphenylcarbinol (DADPC) and doped with Li2PdCl4 (LTP) or Pd[(CH3)2S]2Cl2 (PDS) were selected for a detailed x-ray photoelectron spectroscopic (XPS) study to determine the oxidation state of palladium and the relative distribution of this and other elements in these films, especially as they relate to electrical resistivity. XPS shows that Pd in the films is present as a mixture of zero and +2 valence states. Films that contain lithium as part of the dopant all show that metal is present as Li+ and Li2O, a fact that may have a bearing on film electrical properties. An Auger electron spectroscopic (AES) or XPS profiling was performed on two of the electrically conductive films. A film doped with PDS reveals a majority of palladium at the surface as Pd(0) and much smaller amounts in film bulk as a mixture of Pd(0) and Pd(II). Film behavior is similar to a metal-vapor deposited film. An LTP doped film, by contrast, exhibits a homogeneous composition with a mixture of Pd(0) and Pd(II). These studies support others that use chemical etching on the film surfaces. Scanning electron microscopy (SEM) has been used to provide surface evaluations.  相似文献   
134.
Current solution NMR experiments for characterizing conformational exchange processes in large proteins are limited to exchange rates ca. 500-3000 s-1. A TROSY-based constant relaxation time (R1rho - R1) experiment is designed to extend this capability to measure motion with rates up to 105 s-1 in large macromolecules. The experiment combines off-resonance spin-lock rf fields, which provide access to the faster time-scale dynamics, with TROSY coherence selection, which extends the molecular-weight range available for study. When implemented on the 53-kDa dimeric enzyme triosephosphate isomerase, the experiment yielded substantial gains in signal-to-noise (up to 60%) over current experiments at modest static magnetic fields (14.1 T). The TROSY (R1rho - R1) experiment should therefore be of general utility for investigation of fast conformational exchange events in large proteins.  相似文献   
135.
Synthesis and Properties of Partially Silylated Tri- and Tetraphosphanes. Reaction of Lithiated Diphosphanes with Chlorophosphanes The reactions of Li(Me3Si)P? P(SiMe3)(CMe3) 1 , Li(Me3Si)P? P(CMe3)2 2 , and Li(Me3C)P? P(SiMe3)(CMe3) 3 with the chlorophosphanes P(SiMe3)(CMe3)Cl, P(CMe3)2Cl, or P(CMe3)Cl2 generate the triphosphanes [(Me3C)(Me3Si)P]2P(SiMe3) 4 , (Me3C)(Me3Si)P? P(SiMe3)? P(CMe3)2 6 , [(Me3C)2P]2P(SiMe3) 7 , and (Me3C)(Me3Si)P? P(SiMe3)? P(CMe3)Cl 8 . The triphosphane (Me3C)2P? P(SiMe3)? P(SiMe3)2 5 is not obtainable as easily. The access to 5 starts by reacting PCl3 with P(SiMe3)(CMe3)2, forming (Me3C)2 P? PCl2, which then with LiP(SiMe3)2 gives (Me3C)2 P? P(Cl)? P(SiMe3)2 11 . Treating 11 with LiCMe3 generates (Me3C)2P? P(H)? P(SiMe3)2 16 , which can be lithiated by LiBu to give (Me3C)2P? P(Li)? P(SiMe3)2 13 and after reacting with Me3SiCl, finally yields 5 . 8 is stable at ?70°C and undergoes cyclization to P3(SiMe3)(CMe3)2 in the course of warming to ambient temperature, while Me3SiCl is split off. 7 , reacting with MeOH, forms [(Me3C)2P]2PH. (Me3C)2P? P(Li)? P(SiMe3)2 18 , which can be obtained by the reaction of 5 with LiBu, decomposes forming (Me3C)2P? P(Li)(SiMe3), P(SiMe3)3, and LiP(SiMe3)2, in contrast to either (Me3C)2P? P(Li)? P(SiMe3)(CMe3) 19 or [(Me3C)2P]2PLi, which are stable in ether solutions. The Li phosphides 1 , 2 , and 3 with BrH2C? CH2Br form the n-tetraphosphanes (Me3C)(Me3Si)P? [P(SiMe3)]2? P(SiMe3)(CMe3) 23 , (Me3C)2P? [P(SiMe3)]2? P(CMe3)2 24 , and (Me3C)(Me3Si)P? [P(CMe3)]2? P(SiMe3)(CMe3) 25 , respectively. Li(Me3Si)P? P(SiMe3)2, likewise, generates (Me3Si)2P? [P(SiMe3)]2? P(SiMe3)2 26 . Just as the n-triphosphanes 4 , 5 , 6 , and 7 , the n-tetraphosphanes 23 , 24 , and 25 can be isolated as crystalline compounds. 23 , treated with LiBu, does nor form any stable n-tetraphosphides, whereas 24 yields (Me3C)2P? P(Li)? P(SiMe3)? P(CMe3)2, that is stable in ethers. With MeOH, 24 , forms crystals of (Me3C)2P? P(H)? P(SiMe3)? P(CMe3)2.  相似文献   
136.
The nucleophilic attack of hydroxylamine at the 5 position of 2-aryl-4-trifluoroacetyl-5-amino-oxazoles leads to a mixture of stereoisomeric isoxazolines. Dehydration of these isomeric isoxazolines in the presence of trifluoroacetic anhydride gives 3-amino-4-acylamino-5-trifluoromethylisoxazoles. The structures and spectroscopic data of these compounds are discussed.  相似文献   
137.
Formation of Organosilicon Compounds. 89. Selective Photobromination of Si-methylated Carbosilanes A selective photobromination of the C atoms in the skeleton of Si-methylated carbosilanes is reported. (me3Si? CH2)2Sime2 reacts to me3Si? CBr2? Sime2? CH2? Sime3 in good yields (me = CH3); the second CH2 group is considerably slower brominated. Photobromination of (me2Si? CH2)3 consecutively yields a and b . Also from (me2Si? CH2)4 the derivative with one CBr2 group is accessible. Bromination of tertiary CH groups is highly preferred; this is shown by the selective formation of c . The C-bromination of SiBr-substituted carbosilanes is significantly more difficult; nevertheless (Brme2Si)2CH2 selectively forms (Brme2Si)2CBr2. Brme2Si? CH2? Sime2? CH2? Sime3 forms Brme2Si? CH2? Sime2? CBr2? Sime3, i. e., only the CH2 group non-adjacent to SiBr is attacked. The formation of CHBr groups could not be detected. Higher temperatures and longer reaction times increase the formation of polymers.  相似文献   
138.
N-Acylnitroso derivatives 6 which were prepared by in-situ oxidation of the corresponding hydroxamic acids 5 reacted instantaneously and in high yields with dihydropyridine 4 . The Diels-Alder adducts 8 were formed regiospecifically with the acylnitroso dienophiles 6a–c , whereas the dienophiles 6d–f gave mixtures of both regioisomers 7 and 8 . These and some other results [2] were best explained by the FMO theory. The Diels-Alder adducts 7 and 8 gave the corresponding ‘anti’-cis-glycols when reacted with OsO4/N-methylmorpholine N-oxide. Hydrogenolysis of the N–O bond followed by peracetylation led to the expected aminolyxose derivatives 14 and 16 . A similar sequence, using 4 and the hydroxamic-acid derivative 18 of (+)-D-mandelic acid led, with a poor asymmetric induction, to a mixture of the expected optically active aminolyxose compounds 19A / 19B .  相似文献   
139.
Summary Organic Compounds carrying groups containing both nitrogen and oxygen, such as nitro- and nitroso compounds, oximes, hydroxamic acids, azoxy compounds, and amine oxides yield nitrous acid when they are heated dry (pyrolysis). This product can be readily detected in the gas phase by theGriess nitrite reaction. This behavior provides a rapid preliminary test for members of these classes of compounds. Micro analytical limits of identification are readily obtained within the technique of spot test analysis.
Zusammenfassung Organische Verbindungen mit Stickstoff- und sauerstoffhaltigen Atomgruppen, demnach Nitro- und Nitrosoverbindungen, Oxime, Hydroxamsäuren, Azoxy verbindungen und Aminoxyde spalten bei trockenem Erhitzen (Pyrolyse) salpetrige Säure ab, die in der Gasphase durch dieGriesssche Nitritreaktion empfindlich nachweisbar ist. Dieses Verhalten ermöglicht eine schnelle Vorprüfung auf Angehörige der genannten Verbindungsklassen. In der Technik der Tüpfelanalyse werden mikroanalytische Erfassungsgrenzen erreicht.

Résumé Les combinaisons organiques porteuses d'un groupement azoté et oxygéné telles que les combinaisons nitrées et nitrosées, les oximes, les acides hydroxamiques, les composés azoxy et les oxydes d'aminés, libèrent de l'acide nitreux par chauffage à sec (pyrolyse); cet acide peut être identifié en phase gazeuse par la sensible réaction deGriess des nitrites. Ce comportement permet d'effectuer un essai préliminaire rapide sur les composés appartenant aux classes précédentes. Lorsqu'on met en oeuvre la technique de l'analyse à la touche, les limites de sensibilité atteintes permettent de travailler dans le domaine microanalytique.
  相似文献   
140.
Formation of Organosilicon Compounds. LI. Reactions of Various Chlorinated 1.3.5-Trisilacyclohexanes with CH3MgCl and their 29SiNMR Spectra The reaction of (a) with meMgCl starts with the formation of a Grignard compound of (a) and forms (c) via (b). The reaction sequence will be described. The ring contraction of the six-membered ringsystem is also observed with compound (d) leading to (e), whereas (f) reacts to (g), the ringsystem being maintained. No ring-contraction is observed when investigating the reactions of the derivatives containing Si? H- and C? Cl-groups. Compound (i) gives rise to (j), (k) to (l) whereas cleavage occurs with (m) and (n) does not react under the conditions applied. According to the PMR and 29SiNMR spectra, the polarity of the Si? Cl-bond decreases in the compounds containing Si? Cl and CCl-groups by increasing the number of CCl2 groups. In the compounds containing Si? H and C? Cl-groups the polarity of the Si? H-bond increases with the degree of chlorination at the C-atom. By that, the different chemical behaviour can be understood. The preparations of the starting compounds are described.  相似文献   
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