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991.
Yuki Seo 《Linear algebra and its applications》2000,320(1-3)
As a converse of the arithmetic–geometric mean inequality, W. Specht [Math. Z. 74 (1960) 91–98] estimated the ratio of the arithmetic mean to the geometric one. In this paper, we shall show complementary inequalities to the matricial generalization of Oppenheim's inequality and the Golden–Thompson type inequalities on the Hadamard product by T. Ando [Linear Algebra Appl. 26 (1979) 203; Linear Algebra Appl. 241–243 (1996) 105], in which Specht's ratio plays an important role. As an application, we shall obtain a complementary inequality to the Hadamard determinant inequality. 相似文献
992.
Ryu Hashimoto Masafumi Minoshima Souhei Sakata Fumihito Ono Hirokazu Ishii Yuki Watakabe Tomomi Nemoto Saeko Yanaka Koichi Kato Kazuya Kikuchi 《Chemical science》2022,13(25):7462
In photoactivation strategies with bioactive molecules, one-photon visible or two-photon near-infrared light-sensitive caged compounds are desirable tools for biological applications because they offer reduced phototoxicity and deep tissue penetration. However, visible-light-sensitive photoremovable protecting groups (PPGs) reported so far have displayed high hydrophobicity and low uncaging cross sections (εΦ < 50) in aqueous media, which can obstruct the control of bioactivity with high spatial and temporal precision. In this study, we developed hydroxylated thiazole orange (HTO) derivatives as visible-light-sensitive PPGs with high uncaging cross sections (εΦ ≈ 370) in aqueous solution. In addition, 2PE photolysis reactions of HTO-caged glutamate were achieved using a NIR laser (940 nm). Moreover, HTO-caged glutamate can activate N-methyl-d-aspartic acid receptors in Xenopus oocytes and mammalian cells with green-light illumination, thus allowing optical control of biological functions.A hydroxylated thiazole orange (HTO)-caged glutamate efficiently releases a glutamate for temporal activation of ion channels under visible-to-NIR light in aqueous media. 相似文献
993.
Yuki Yoshikawa Keisuke Yuzu Naoki Yamamoto Ken Morishima Rintaro Inoue Masaaki Sugiyama Tetsushi Iwasaki Masatomo So Yuji Goto Atsuo Tamura Eri Chatani 《Molecules (Basel, Switzerland)》2022,27(13)
Amyloid fibrils have been an important subject as they are involved in the development of many amyloidoses and neurodegenerative diseases. The formation of amyloid fibrils is typically initiated by nucleation, whereas its exact mechanisms are largely unknown. With this situation, we have previously identified prefibrillar aggregates in the formation of insulin B chain amyloid fibrils, which have provided an insight into the mechanisms of protein assembly involved in nucleation. Here, we have investigated the formation of insulin B chain amyloid fibrils under different pH conditions to better understand amyloid nucleation mediated by prefibrillar aggregates. The B chain showed strong propensity to form amyloid fibrils over a wide pH range, and prefibrillar aggregates were formed under all examined conditions. In particular, different structures of amyloid fibrils were found at pH 5.2 and pH 8.7, making it possible to compare different pathways. Detailed investigations at pH 5.2 in comparison with those at pH 8.7 have suggested that the evolution of protofibril-like aggregates is a common mechanism. In addition, different processes of evolution of the prefibrillar aggregates have also been identified, suggesting that the nucleation processes diversify depending on the polymorphism of amyloid fibrils. 相似文献
994.
Naohiro Oshima Maho Saito Mina Niino Yuki Hiraishi Kana Ueki Kazuki Okoshi Takashi Hakamatsuka Noriyasu Hada 《Molecules (Basel, Switzerland)》2022,27(3)
To elucidate the interactions between crude drugs in Kampo medicines (traditional Japanese medicines), it is important to determine the content of the constituents in a cost-effective and simple manner. In this study, we quantified the constituents in crude drug extracts using thin-layer chromatography (TLC), an inexpensive and simple analytical method, to elucidate the chemical interactions between crude drugs. We focused on five crude drugs, for which quantitative high-performance liquid chromatography (HPLC) methods are stipulated in the Japanese Pharmacopoeia XVIII (JP XVIII) and compared the analytical data of HPLC and TLC, confirming that the TLC results corresponded with the HPLC data and satisfied the criteria of JP XVIII. (Z)-ligustilide, a major constituent in Japanese Angelica Root, for which a method of quantification has not been stipulated in JP XVIII, was also quantitatively analyzed using HPLC and TLC. Furthermore, Japanese Angelica Root was combined with 26 crude drugs to observe the variation in the (Z)-ligustilide content from each combination by TLC. The results revealed that combinations with Phellodendron Bark, Citrus Unshiu Peel, Scutellaria Root, Coptis Rhizome, Gardenia Fruit, and Peony Root increased the (Z)-ligustilide content. Quantifying the constituents in crude drug extracts using the inexpensive and simple TLC method can contribute to elucidating interactions between crude drugs in Kampo medicines, as proposed by the herbal-pair theory. 相似文献
995.
Yuki Yamamoto Fumiya Sato Qiqi Chen Shintaro Kodama Akihiro Nomoto Akiya Ogawa 《Molecules (Basel, Switzerland)》2022,27(3)
Although diaryl tellurides are parent organotellurium compounds, their synthesis methods, especially for unsymmetrical ones, are limited. This may be due to the instability of diaryl tellurides and their synthesis intermediates under reaction conditions. Radical reactions are known to exhibit excellent functional group selectivity; therefore, we focused on a bimolecular homolytic substitution (SH2) reaction between the aryl radical and diaryl ditelluride. Aryl radicals are generated from arylhydrazines in air and captured by diaryl ditellurides, resulting in a selective formation of unsymmetrical diaryl tellurides with high yields. The electronic effects of the substituents on both arylhydrazines and diaryl ditellurides on the SH2 reaction of tellurium are also discussed in detail. 相似文献
996.
997.
998.
Structure and dynamics of room temperature ionic liquids with bromide anion: results from 81Br NMR spectroscopy 下载免费PDF全文
Takatsugu Endo Mamoru Imanari Yuki Hidaka Hiroko Seki Keiko Nishikawa Sabyasachi Sen 《Magnetic resonance in chemistry : MRC》2015,53(5):369-378
We report the results of a comprehensive 81Br NMR spectroscopic study of the structure and dynamics of two room temperature ionic liquids (RTILs), 1‐butyl‐3‐methylimidazolium bromide ([C4mim]Br) and 1‐butyl‐2,3‐dimethylimidazolium bromide ([C4C1mim]Br), in both liquid and crystalline states. NMR parameters in the gas phase are also simulated for stable ion pairs using quantum chemical calculations. The combination of 81Br spin‐lattice and spin‐spin relaxation measurements in the motionally narrowed region of the stable liquid state provides information on the correlation time of the translational motion of the cation. 81Br quadrupolar coupling constants (CQ) of the two RTILs were estimated to be 6.22 and 6.52 MHz in the crystalline state which were reduced by nearly 50% in the liquid state, although in the gas phase, the values are higher and span the range of 7–53 MHz depending on ion pair structure. The CQ can be correlated with the distance between the cation–anion pairs in all the three states. The 81Br CQ values of the bromide anion in the liquid state indicate the presence of some structural order in these RTILs, the degree of which decreases with increasing temperature. On the other hand, the ionicity of these RTILs is estimated from the combined knowledge of the isotropic chemical shift and the appropriate mean energy of the excited state. [C4C1mim]Br has higher ionicity than [C4mim]Br in the gas phase, while the situation is reverse for the liquid and the crystalline states. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
999.
Stable but Reactive Perfluoroalkylzinc Reagents: Application in Ligand‐Free Copper‐Catalyzed Perfluoroalkylation of Aryl Iodides 下载免费PDF全文
Dr. Kohsuke Aikawa Yuzo Nakamura Yuki Yokota Wataru Toya Prof. Dr. Koichi Mikami 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(1):96-100
The aromatic perfluoroalkylation catalyzed by a copper(I) salt with bis(perfluoroalkyl)zinc reagents Zn(RF)2(DMPU)2, which were prepared and then isolated as a stable white powder from perfluoroalkyl iodide and diethylzinc, was accomplished to provide the perfluoroalkylated products in good‐to‐excellent yields. The advantages of this reliable and practical catalytic reaction are 1) air‐stable and easy‐to‐handle bis(perfluoroalkyl)zinc reagents can be utilized, 2) the reagent is reactive and hence the operation without activators and ligands is simple, and 3) not only trifluoromethylation but also perfluoroalkylation can be attained. 相似文献
1000.