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81.
Yasukazu Sugiyama Kento Yamada Daiki Kaneko Yuya Kusagawa Dr. Toshitaka Okamura Prof. Dr. Takaaki Sato 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2024,136(6):e202317290
A reductive (3+2) annulation of lactams through iridium-catalyzed hydrosilylation and photoredox coupling with α-bromoacetic acid was developed. The iridium-catalyzed hydrosilylation of the lactam carbonyl group and subsequent elimination provide a transient cyclic enamine, which undergoes iridium-catalyzed photoredox coupling with α-bromoacetic acid in a one-pot process. The developed conditions show high functional-group tolerance and provide cyclic N,O-acetals containing a quaternary carbon center. The resulting N,O-acetals undergo a variety of acid-mediated nucleophilic addition reactions via iminium ions to give substituted cyclic amines. The developed sequence including reductive (3+2) annulation and acid-mediated nucleophilic addition was successfully applied to the four-step total synthesis of (±)-eburnamonine. 相似文献
82.
A novel straightforward synthesis of 3‐(1H‐tetrazol‐5‐yl)coumarins (=3‐(1H‐tetrazol‐5‐yl)‐2H‐1‐benzopyran‐2‐ones) 6 via domino Knoevenagel condensation, Pinner reaction, and 1,3‐dipolar cycloaddition of substituted salicylaldehydes (=2‐hydroxybenzaldehydes), malononitrile (propanedinitrile), and sodium azide in H2O is reported (Scheme 1 and Table 2). This general protocol provides a wide variety of 3‐(1H‐tetrazol‐5‐yl)coumarins in good yields under mild reaction conditions. 相似文献
83.
The reaction of ortho-alkynylated benzaldehydes 1 with allyltrimethylsilane under the Pd(OAc)2-CuCl2 catalyst system gave the isochromene derivatives 2 together with the chlorinated products 3. When the reaction was conducted in the presence of half equiv of H2O, the formation of 3 was suppressed and 2 was obtained in good to high yields. When the reaction of 1a was carried out with trimethylsilylcyanide instead of allylsilane, the cyano group-substituted isochromene 9 was obtained in 94% yield. 相似文献
84.
Szilvia Hajdok 《Tetrahedron letters》2007,48(29):5073-5076
Laccase initiated domino reactions of cyclohexane-1,3-diones with catechols using air as an oxidant afford 3,4-dihydro-7,8-dihydroxy-2H-dibenzofuran-1-ones with yields ranging from 70% to 97%. 相似文献
85.
H. Iwasaki T. Motobayashi H. Akiyoshi Y. Ando N. Fukuda H. Fujiwara Zs. Fülöp K. I. Hahn Y. Higurashi M. Hirai I. Hisanaga N. Iwasa T. Kijima A. Mengoni T. Minemura T. Nakamura M. Notani S. Ozawa H. Sagawa H. Sakurai S. Shimoura S. Takeuchi T. Teranishi Y. Yanagisawa M. Ishihara 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):55-58
Experimental studies on in-beam γ-ray spectroscopy using a 12Be radioactive beam are presented. Inelastic scattering of the neutron-rich 12Be nucleus on 208Pb, 12C, and (CH2)n targets has been studied by measuring de-excitation γ-rays in coincidence with scattered particles. The level schemes and
transition probabilities are determined for low-lying excited states in 12Be. The present paper presents a brief review of the spectroscopic results, which may be associated with the N = 8 shell quenching near the drip line.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
86.
Kersten M. Gericke 《Tetrahedron》2008,64(26):6002-6014
The synthesis of novel tetracyclic fused pyrroles from 1-(2-iodophenyl)-1H-pyrrole and various bromoalkyl-aryl alkynes via a palladium(0)-catalyzed and norbornene-mediated threefold domino reaction is reported. PdCl2 and tri-2-furylphosphine (TFP) in the presence of norbornene and Cs2CO3 in CH3CN at 90 °C gave a variety of tetracyclic fused pyrroles in usually high yields. In the described reaction sequence two of the three carbon-carbon bonds are formed by functionalization of an unactivated aryl C-H bond. 相似文献
87.
Malihe Javan Khoshkholgh Hamid Reza Bijanzadeh Jürgen H. Gross 《Tetrahedron letters》2008,49(49):6965-6968
An efficient synthesis of tetracyclic uracil derivatives (polycyclic pyrans) is achieved via domino Knoevenagel-hetero-Diels-Alder reactions of O-propargylated salicylaldehyde derivatives with 1,3-dimethylbarbituric acid in water as solvent in the presence of CuI. The products are formed in good yields. 相似文献
88.
The study of excited 55Mn levels with the 52Cr(α, pγ) reaction was extended to levels up to 3161 keV. With a Ge(Li) detector, DSA measurements in gold-backed targets were made, as well as angular correlations; both of these experiments were done in coincidence with protons detected near 180°. A multiple-detector NaI(Tl) array was also used in the same reaction geometry for better γ-ray detection efficiency. Mean lifetimes of 12 levels from 2727 to 3161 keV are reported. Spins and sometimes parities of the following levels were deduced from the angular-correlation analyses and lifetime results: 1885 keV, ?; 2199 keV, (?); 2311 keV, (); 2366keV, ?; 2727 keV, ; 2823 keV, . Multipole mixing ratios and M1 and E2 transition rates of the radiations from these and from the 1292 keV level are presented. The similarity of the low-lying level structure and of interlevel transitions in 55Mn to those in certain other f3 nuclei is examined. 相似文献
89.
A “Coulomb-modified” dispersion relation is applied to low-energy p-4He forward elastic scattering. To check the validity of the modification, the results are compared with those deduced from n-4He elastic scattering. Completely analogous information is obtained for the two processes. The exchange of three bound nucleons is found to contribute strongly to N-4He forward scattering. The corresponding 4He-3H-p and 4He-3He-n coupling constants are evaluated as Rp = 3.8±0.3 and Rn = 3.0±0.3, respectively. These constants are related to the strength of the asymptotic wave function of nucleons in 4He and thus to the tail of the nucleon distribution. A comparison of Rp with the empirical proton distribution in 4He as deduced from e-4He elastic scattering shows excellent agreement. From Rp and Rn the effective ranges of the singlet 3H-p and 3He-n interactions in the ground state of 4He are determined to be equal, in accordance with charge symmetry, and to have a value of reff = 1.072±0.006 fm. 相似文献
90.
The reactions (α, 3nγ) and (α, α′nγ) on 88Sr, 90Zr and 92Mo were used to populate excited states in 89Zr, 91Mo and 93Ru. The de-excitation of these states was studied by in-beam γ-ray spectroscopy. The short-lived radioactivity of the 92Mo target was measured in order to study the decay of 93Ru. Many new levels were observed, particularly in 91Mo. They are interpreted as due to the coupling of a neutron hole with known excited states in 90Zr, 92Mo and 94Ru. 相似文献