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171.
Sano S Shimizu H Kim K Lee WS Shiro M Nagao Y 《Chemical & pharmaceutical bulletin》2006,54(2):196-203
Diethyl alpha-alkynyl-alpha-methoxymalonates (2a--e) were smoothly hydrolyzed and then decarboxylated under alkaline conditions employing 1 N KOH in EtOH to give conjugated allenyl esters (6a--e) in high yields, and similar alkaline treatment of diethyl alpha-alkynyl-alpha-acetylaminomalonates (5a, b, d, e) furnished unexpectedly the oxazoles (7a, b, d, e) having three substituent groups in excellent yields. 相似文献
172.
Kobayashi S Shinohara H Tabata K Yamamoto N Miyai A 《Chemical & pharmaceutical bulletin》2006,54(12):1633-1638
The aim of this study was to elucidate the structure-activity relationship of bisphenol A (BPA) analogs using absolute hardness (eta) and absolute electronegativity (chi) (chemical hardness) and to design a non-estrogen active BPA. To determine the structure-activity relationships of BPA analogs, we investigated MCF-7 cell proliferation stimulated by BPA analogs and an eta-chi diagram based on the electronic structure of the BPA analogs. The results show that the actions of the environmental hormones BPA analogs have two chemical properties; (i) 'stereo structure-controlled' and (ii) 'electronic structure-controlled' estrogen-like chemical activities. Therefore, we designed and synthesized BPA analogs which do not possess these 2 characteristics, ((i) and (ii)), and demonstrate the non-estrogen activity of the analog. 相似文献
173.
Inerbaev TM Saito S Belosludov RV Mizuseki H Takahashi M Kawazoe Y 《The Journal of chemical physics》2006,125(23):234702
As it has been found experimentally [K. Clays and B. Coe, Chem. Mater. 15, 642 (2003); B. J. Coe et al., 126, 10418 (2004)], elongation of the conjugation path length and N-arylation in stilbazolium chromophores both lead to substantial enhancement of the molecular optical nonlinearities. In the present contribution the authors perform a quantum chemical analysis of the excited state properties and quadratic nonlinear optical responses of a series of this type of dyes. Nonlinear optical responses are estimated by both finite-field and two-state model approaches that demonstrate an excellent qualitative mutual agreement. Time-dependent density functional theory calculations on the isolated cations predict redshift in the energy of the intramolecular charge transfer transition that is overestimated for cations with the longer conjugation path length. At the same time, in comparison with the Stark spectroscopy measurements the differences between the excited and ground state dipole moments are grossly underestimated for all compounds. The inclusion of solvent effect by polarizable continuum model affords a better agreement with experiment for these quantities. The authors' calculations demonstrate the crucial dependence of the electronic excitation properties on the way of the investigated compound geometry optimization. The origin of such dependence is discussed. 相似文献
174.
We consider a class of planar self-affine tiles T = M-1 a∈D(T + a) generated by an expanding integral matrix M and a collinear digit set D as follows:M =(0-B 1-A),D = {(00),...,(|B|0-1)}.We give a parametrization S1 →T of the boundary of T with the following standard properties.It is H¨older continuous and associated with a sequence of simple closed polygonal approximations whose vertices lie on T and have algebraic preimages.We derive a new proof that T is homeomorphic to a disk if and only if 2|A| |B + 2|. 相似文献
175.
We calculated numerically the values of -functions of four typical elliptic curves in the critical strip in the range . We found that all the non-trivial zeros in this range lie on the critical line and are simple except the one at . The method we employed in this paper is the approximate functional equation with incomplete gamma functions in the coefficients. For incomplete gamma functions, we continued them holomorphically to the right half plane , which enables us to calculate for large . Furthermore we remark that a relation exists between Sato-Tate conjecture and the generalized Riemann Hypothesis.
176.
Hiroyuki Kakei Riichiro Tsuji Dr. Takashi Ohshima Dr. Hiroyuki Morimoto Shigeki Matsunaga Dr. Masakatsu Shibasaki Prof. Dr. 《化学:亚洲杂志》2007,2(2):257-264
The full details of the asymmetric epoxidation of α,β‐unsaturated esters catalyzed by yttrium complexes with biaryldiol ligands are described. An yttrium–biphenyldiol catalyst, generated from Y(OiPr)3–biphenyldiol ligand–triphenylarsine oxide (1:1:1), is suitable for the epoxidation of various α,β‐unsaturated esters. With this catalyst, β‐aryl α,β‐unsaturated esters gave high enantioselectivities and good yields (≤99 % ee). The reactivity of this catalyst is good, and the catalyst loading could be decreased to as little as 0.5–2 mol % (the turnover number was up to 116), while high enantiomeric excesses were maintained. For β‐alkyl α,β‐unsaturated esters, an yttrium–binol catalyst, generated from Y(OiPr)3–binol ligand–triphenylphosphine oxide (1:1:2), gave the best enantioselectivities (≤97 % ee). The utility of the epoxidation reaction was demonstrated in an efficient synthesis of (?)‐ragaglitazar, a potential antidiabetes agent. 相似文献
177.
A tandem stereoselective reduction-olefination reaction of ethyl 2-acyl-2-fluoro-2-diethylphosphonoacetate employing NaBH4 in EtOH was developed. The one-pot reaction gave α-fluoro-α,β-unsaturated esters with excellent (Z)-selectivity. A plausible mechanism involving a diastereoselective reduction predicted by the Felkin-Anh model, followed by olefination similar to the Horner-Wadsworth-Emmons reaction, has been proposed. 相似文献
178.
Matsumoto K Ajiro H Habaue S Okamoto Y 《Rapid communications in mass spectrometry : RCM》2003,17(7):678-684
The oxidation numbers of metals in inorganic compounds were identified by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) by using their acetylacetonates, which are soluble in acetone. For the MALDI analysis of inorganic species insoluble in common solvents used for matrices, such as acetone, methanol, water, etc., a suspension method of sample preparation was developed. Turbid suspensions of inorganic species in the solvent were spotted on the sample holder with chelating reagents, as in the conventional sample preparation for MALDI-MS. Chemical reaction between the inorganic species and the chelating reagents occurred in the plume after irradiation by laser light. Metal oxides were also analyzed by this method, and samples with different oxidation numbers gave different mass spectra. These results suggest that many other metal oxides with different oxidation numbers could be identified if suitable chelating reagents are chosen for sample preparation for MALDI-MS. 相似文献
179.
Matsunaga S Yoshida T Morimoto H Kumagai N Shibasaki M 《Journal of the American Chemical Society》2004,126(28):8777-8785
Full details of a direct catalytic asymmetric Mannich-type reaction of a hydroxyketone using a Et2Zn/(S,S)-linked-BINOL complex are described. By choosing the proper protective groups on imine nitrogen, either anti- or syn-beta-amino alcohol was obtained in good diastereomeric ratio, yield, and excellent enantiomeric excess using the same zinc catalysis. N-Diphenylphosphinoyl (Dpp) imine 3 gave anti-beta-amino alcohols in anti/syn = up to >98/2, up to >99% yield, and up to >99.5% ee, while Boc-imine 4 gave syn-beta-amino alcohols in anti/syn = up to 5/95, up to >99% yield, and up to >99.5% ee. The high catalyst turnover number (TON) is also noteworthy. Catalyst loading was successfully reduced to 0.02 mol % (TON = up to 4920) for the anti-selective reaction and 0.05 mol % (TON = up to 1760) for the syn-selective reaction. The Et2Zn/(S,S)-linked-BINOL complex exhibited far better TON than in previous reports of catalytic asymmetric Mannich-type reactions. Mechanistic studies to clarify the reason for the high catalyst efficiency as well as transformations of Mannich adducts are also described. 相似文献
180.
Kimura H Kanesaka S Kuroki S Ando I Asano A Kurosu H 《Magnetic resonance in chemistry : MRC》2005,43(3):209-216
The structure of poly(diethylsiloxane) (PDES) has been characterized using solid-state NMR of (17)O. The sample studied had a weight-average molecular weight of 2.45 x 10(5). The sample was prepared by utilizing the cationic ring-opening polymerization of (17)O-enriched hexacyclotrisiloxane. Solid-state NMR of (17)O-enriched PDES was measured on the low-temperature beta(1) phase, the high-temperature beta(2) phase, the two-phase system consisting of the liquid crystal and isotropic liquid phase and the isotropic phase. From these data, the molecular structure and dynamics of PDES in the various phases were characterized via the chemical shifts of (17)O, and electric field gradient parameters were determined from NMR and ab initio molecular orbital (MO) calculations. In addition to the solid-state NMR of (1)H, (13)C and (29)Si previously reported on these samples, knowledge of the dynamic behavior of PDES as inferred from the NMR of (17)O in the present study was enhanced significantly. Further, the potential of combining the experimental NMR of (17)O with ab initio MO calculations to characterize the dynamics of polymers containing oxygen is demonstrated. 相似文献