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991.
992.
A syn‐Selective Aza‐Aldol Reaction of Boron Aza‐Enolates Generated from N‐Sulfonyl‐1,2,3‐Triazoles and 9‐BBN‐H 下载免费PDF全文
Dr. Tomoya Miura Takayuki Nakamuro Sho Miyakawa Prof. Dr. Masahiro Murakami 《Angewandte Chemie (International ed. in English)》2016,55(30):8732-8735
A syn‐selective aza‐aldol reaction of boron aza‐enolates, generated from N‐sulfonyl‐1,2,3‐triazoles and 9‐BBN‐H, is reported. It provides a sequential one‐pot procedure for the stereoselective construction of 1,3‐amino alcohols, having contiguous stereocenters, starting from terminal alkynes. 相似文献
993.
Shohei Kobori Kazuki Matsui Hideki Kuwahara Takayuki Goto Xiao Zhang Yuki Nakano Sadafumi Nishihara Katsuya Inoue Takahiko Sasaki 《Hyperfine Interactions》2016,237(1):116
The two-legged spin ladder Cu(CO3)0.5(ClO4)(H2O)0.5(NH3)2.5 consists of a rung formed by two Cu(II)’s and of a spacing molecule CO\(_{3}^{2-}\) between each two rungs. The non-centrosymmetric shape of CO\(_{3}^{2-}\) molecule brings a slight bond alternation along the leg, and hence the system can be considered as an alternating spin chain, which is confirmed so far by the temperature dependence of magnetic susceptibility. In order to investigate its spin state at low temperatures, we have performed experiments of 1H-NMR, magnetization and specific heat under wide range of magnetic field, and have found the critical diverging of longitudinal relaxation rate 1/T 1, the spectral broadening and the lambda-type anomaly in specific heat at T N? 3.4 K, indicating the existence of long range magnetic order. In paramagnetic state well above T N, 1/T 1 showed a power-law temperature dependence, suggesting the realization of Tomonaga Luttinger liquid state. 相似文献
994.
RA‐dimer B,a New Dimeric RA‐series Cyclopeptide Incorporating Two Different Types of Cycloisodityrosine Units,from Rubia cordifolia L. 下载免费PDF全文
Dr. Yukio Hitotsuyanagi Takayuki Tsuchiya Masako Ohata Ayaka Yoshida Haruhiko Fukaya Hyun Sun Park Koichi Takeya Dr. Nobuo Kawahara 《化学:亚洲杂志》2016,11(23):3389-3397
RA‐dimer B, a new cytotoxic RA‐series peptide, was isolated from the roots of Rubia cordifolia L. Its structure was elucidated on the basis of spectroscopic analysis to be a dimeric cyclopeptide composed of deoxybouvardin and allo‐RA‐V. Those two cyclopeptide units are connected by an ether linkage between the phenolic oxygen atom of deoxybouvardin and the ?a carbon atom of Tyr‐6 of allo‐RA‐V. RA‐dimer B was synthesized by the coupling reaction of deoxybouvardin with the boronic acid derivative of allo‐RA‐V, and subsequent deprotection, confirming the relative stereochemistry and establishing the absolute configuration of this peptide. RA‐dimer B showed cytotoxic activity against human promyelocytic leukaemia HL‐60, human colonic carcinoma HCT‐116, and human renal cell carcinoma ACHN cells with IC50 values of 0.59, 0.54, and 0.74 μm , respectively. 相似文献
995.
Shota Ooi Dr. Takayuki Tanaka Kyu Hyung Park Prof. Dr. Dongho Kim Prof. Dr. Atsuhiro Osuka 《Angewandte Chemie (International ed. in English)》2016,55(22):6535-6539
The oxidation of 10–10′ singly linked corrole dimers with DDQ at low concentration in CHCl3 afforded meso–meso, β–β, β–β triply linked 2H‐corrole dimers (with two inner NH groups in each corrole unit), which exhibited characteristic 1H NMR and absorption spectra attributable to their nonaromatic electronic networks. These 2H‐corrole dimers were reduced with NaBH4 to aromatic 3H‐corrole dimers, which were unstable and easily oxidized back to the 2H‐corrole dimers upon exposure to air. Bis(zinc(II)) complexes of the 2H‐corrole dimers were synthesized and characterized as rare examples of nonaromatic zinc(II) corrole complexes. 相似文献
996.
Ryuichi Wada Satoru Takanashi Yuichiro Nakai Tomoki Nakayama Mai Ouchi 《Isotopes in environmental and health studies》2016,52(6):603-618
We conducted continuous, high time-resolution measurements of CO2 and water vapour isotopologues (16O12C16O, 16O13C16O and 18O12C16O for CO2, and H218O for water vapour) in a red pine forest at the foot of Mt. Fuji for 9 days from the end of July 2010 using in situ absorption laser spectroscopy. The δ18O values in water vapour were estimated using the δ2H–δ18O relationship. At a scale of several days, the temporal variations in δ18O-CO2 and δ18O-H2O are similar. The orders of the daily Keeling plots are almost identical. A possible reason for the similar behaviour of δ18O-CO2 and δ18O-H2O is considered to be that the air masses with different water vapour isotopic ratios moved into the forest, and changed the atmosphere of the forest. A significant correlation was observed between δ18O-CO2 and δ13C-CO2 values at nighttime (r2≈0.9) due to mixing between soil (and/or leaf) respiration and tropospheric CO2. The ratios of the discrimination coefficients (Δa/Δ) for oxygen (Δa) and carbon (Δ) isotopes during photosynthesis were estimated in the range of 0.7–1.2 from the daytime correlations between δ18O-CO2 and δ13C-CO2 values. 相似文献
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The structure of dibenzo-18-crown-6-ether (DB18C6) and its hydrated clusters has been investigated in a supersonic jet. Two conformers of bare DB18C6 and six hydrated clusters (DB18C6-(H(2)O)(n)) were identified by laser-induced fluorescence, fluorescence-detected UV-UV hole-burning and IR-UV double-resonance spectroscopy. The IR-UV double resonance spectra were compared with the IR spectra obtained by quantum chemical calculations at the B3LYP/6-31+G* level. The two conformers of bare DB18C6 are assigned to "boat" and "chair I" forms, respectively, among which the boat form is dominant. All the six DB18C6-(H(2)O)(n) clusters with n = 1-4 have a boat conformation in the DB18C6 part. The water molecules form a variety of hydration networks in the boat-DB18C6 cavity. In DB18C6-(H(2)O)(1), a water molecule forms the bidentate hydrogen bond with the O atoms adjacent to the benzene rings. In this cluster, the water molecule is preferentially hydrogen bonded from the bottom of boat-DB18C6. In the larger clusters, the hydration networks are developed on the basis of the DB18C6-(H(2)O)(1) cluster. 相似文献