全文获取类型
收费全文 | 1049篇 |
免费 | 43篇 |
专业分类
化学 | 847篇 |
晶体学 | 4篇 |
力学 | 8篇 |
数学 | 17篇 |
物理学 | 216篇 |
出版年
2023年 | 6篇 |
2022年 | 8篇 |
2021年 | 13篇 |
2020年 | 22篇 |
2019年 | 22篇 |
2018年 | 15篇 |
2017年 | 9篇 |
2016年 | 17篇 |
2015年 | 25篇 |
2014年 | 28篇 |
2013年 | 40篇 |
2012年 | 63篇 |
2011年 | 77篇 |
2010年 | 36篇 |
2009年 | 32篇 |
2008年 | 56篇 |
2007年 | 73篇 |
2006年 | 66篇 |
2005年 | 64篇 |
2004年 | 60篇 |
2003年 | 48篇 |
2002年 | 36篇 |
2001年 | 35篇 |
2000年 | 19篇 |
1999年 | 11篇 |
1998年 | 3篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1994年 | 9篇 |
1993年 | 8篇 |
1992年 | 7篇 |
1991年 | 7篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 10篇 |
1987年 | 10篇 |
1986年 | 12篇 |
1985年 | 30篇 |
1984年 | 14篇 |
1983年 | 5篇 |
1982年 | 13篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1979年 | 13篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1975年 | 3篇 |
1974年 | 5篇 |
1973年 | 6篇 |
排序方式: 共有1092条查询结果,搜索用时 15 毫秒
71.
Ayuko Tsuruoka Akira Takahashi Daisuke Aoki Hideyuki Otsuka 《Angewandte Chemie (International ed. in English)》2020,59(11):4294-4298
Crosslinked polymers (CLPs) exhibit exceptional mechanical properties as well as good chemical and solvent resistance. However, their reprocessing, recycling, and modification remain difficult. One promising approach to overcome this limitation is to introduce dynamic covalent bonds that enable chain‐exchange reactions and network‐structure rearrangements in identical polymer networks (A–A fusion), resulting in self‐healing and reprocessing properties. Reported here is the fusion of two distinct polymer networks (A–B fusion) by the dynamic behavior of bis(2,2,6,6‐tetramethylpiperidin‐1‐yl)disulfide (BiTEMPS) at the interface between different CLPs. The appearance, swelling behavior, and mechanical properties of the fused samples indicate exchange reactions of the BiTEMPS units and the formation of topological bonds at the interface, commensurate with the generation of a CLP that exhibits tunable properties. 相似文献
72.
Hayate Saito Keita Yamamoto Yosuke Sumiya Ling‐Jun Liu Keisuke Nogi Satoshi Maeda Hideki Yorimitsu 《化学:亚洲杂志》2020,15(16):2442-2446
C?H iodination of aromatic compounds has been accomplished with the aid of sulfinyl directing groups under palladium catalysis. The reaction proceeds selectively at the peri‐position of polycyclic aryl sulfoxides or at the ortho‐position of phenyl sulfoxides. The iodination products can be further converted via iterative catalytic cross‐coupling at the expense of the C?I and C?S bonds. Computational studies suggest that peri‐C?H palladation would proceed via a non‐directed pathway, wherein neither of the sulfur nor oxygen atom of the sulfinyl group coordinates to the palladium before and at the transition state. 相似文献
73.
Halilibrahim Ciftci Belgin Sever Firdevs Ocak Nilüfer Bayrak Mahmut Yldz Hatice Yldrm Hasan DeMirci Hiroshi Tateishi Masami Otsuka Mikako Fujita Ama Fatih TuYuN 《Molecules (Basel, Switzerland)》2022,27(3)
Plants have paved the way for the attainment of molecules with a wide-range of biological activities. However, plant products occasionally show low biological activities and/or poor pharmacokinetic properties. In that case, development of their derivatives as drugs from the plant world has been actively performed. As plant products, plastoquinones (PQs) have been of high importance in anticancer drug design and discovery; we have previously evaluated and reported the potential cytotoxic effects of a series of PQ analogs. Among these analogs, PQ2, PQ3 and PQ10 were selected for National Cancer Institute (NCI) for in vitro screening of anticancer activity against a wide range of cancer cell lines. The apparent superior anticancer potency of PQ2 on the HCT-116 colorectal cancer cell line than that of PQ3 and PQ10 compared to other tested cell lines has encouraged us to perform further mechanistic studies to enlighten the mode of anti-colorectal cancer action of PQ2. For this purpose, its apoptotic effects on the HCT-116 cell line, DNA binding capacity and several crucial pharmacokinetic properties were investigated. Initially, MTT assay was conducted for PQ2 at different concentrations against HCT-116 cells. Results indicated that PQ2 exhibited significant cytotoxicity in HCT-116 cells with an IC50 value of 4.97 ± 1.93 μM compared to cisplatin (IC50 = 26.65 ± 7.85 μM). Moreover, apoptotic effects of PQ2 on HCT-116 cells were investigated by the annexin V/ethidium homodimer III staining method and PQ2 significantly induced apoptosis in HCT-116 cells compared to cisplatin. Based on the potent DNA cleavage capacity of PQ2, molecular docking studies were conducted in the minor groove of the double helix of DNA and PQ2 presented a key hydrogen bonding through its methoxy moiety. Overall, both in vitro and in silico studies indicated that effective, orally bioavailable drug-like PQ2 attracted attention for colorectal cancer treatment. The most important point to emerge from this study is that appropriate derivatization of a plant product leads to unique biologically active compounds. 相似文献
74.
Optical Review - We demonstrate distributed measurement of the polarization beat length along single-mode optical fibers (SMFs) using slope-assisted Brillouin optical correlation-domain... 相似文献
75.
A. Yamazaki Y. Inoue M. Koike T. Sakamoto R. Otsuka 《Journal of Thermal Analysis and Calorimetry》1993,40(1):85-97
Thomsonite with ideal chemical composition and with an ordered framework structure was synthesised hydrothermally from zeolite Na?A, which was ground to X-ray amorphous, with 0.05 mol dm?3 CaCl2 solution at 200°C. The dehydration behaviour of the prepared thomsonite was examined by TG-DTA. It was revealed that thomsonite lost most of zeolitic water below 450°C in three steps at about 180°, 340° and 390°C. The peak profiles of, the two higher-temperature endotherms were sharp and similar, and the weight loss at each step was approximately equal. 相似文献
76.
Dr. Kyohei Otsuka Naozumi Matsumoto Dr. Shintaro Ishida Prof. Dr. Soichiro Kyushin 《Angewandte Chemie (International ed. in English)》2015,54(27):7833-7836
The radical anion of octa‐tert‐butyloctasilacubane was generated and isolated. The EPR spectrum showed the satellites due to the tertiary 13C nuclei of the eight tert‐butyl groups. The X‐ray crystallographic analysis showed that the Si? Si bonds are shortened and the Si? C bonds are elongated compared with those of octa‐tert‐butyloctasilacubane. These results are well explained by the distribution of an unpaired electron in the singly occupied molecular orbital (SOMO). 相似文献
77.
Takashi Minoshima Yosuke Matsumoto Takanobu Amano 《Journal of computational physics》2011,230(17):6800-6823
We present a new numerical scheme for solving the advection equation and its application to Vlasov simulations. The scheme treats not only point values of a profile but also its zeroth to second order piecewise moments as dependent variables, for better conservation of the information entropy. We have developed one-and two-dimensional schemes and show that they provide quite accurate solutions within reasonable usage of computational resources compared to other existing schemes. The two-dimensional scheme can accurately solve the solid body rotation problem of a gaussian profile for more than hundred rotation periods with little numerical diffusion. This is crucially important for Vlasov simulations of magnetized plasmas. Applications of the one- and two-dimensional schemes to electrostatic and electromagnetic Vlasov simulations are presented with some benchmark tests. 相似文献
78.
Water‐ and Temperature‐Triggered Reversible Structural Transformation of Tetranuclear Cobalt(II) Cores Sandwiched by Polyoxometalates
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Yosuke Kuriyama Dr. Yuji Kikukawa Dr. Kosuke Suzuki Dr. Kazuya Yamaguchi Prof. Dr. Noritaka Mizuno 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(12):3962-3966
Although stimuli‐responsive structural transformations of inorganic materials have attracted considerable attention because of their potential use as functional switchable materials, multinuclear metal cores frequently suffer from unexpected dissociation of metal cations and/or irreversible transformations into infinite structures. In this study, we describe the successful demonstration of the water‐ and temperature‐triggered reversible structural transformation between cubane‐ and planar‐type tetranuclear CoII cores sandwiched by polyoxometalates. The arrangements and coordination geometries of the CoII cations were interconverted by simple hydration and dehydration, resulting in the manipulation of the magnetic and optical properties of these compounds. Moreover, this system showed unique thermochromism through temperature‐dependent reversible structural interconversion. 相似文献
79.
Relative intensity fluctuations in single-mode class B lasers, i.e., a laser diode (LD) and a microchip Nd YVO(4) solid-state laser (SSL), were examined. Experimental observations revealed significant difference in the characteristics of the LD and the SSL. A stochastic laser model and the Fokker-Planck equation approach were used, and reduced moment equations were developed. A close agreement was achieved between the theoretical and experimental results. As indicated by the theoretical analysis, the intrinsic parameter of the lasers; i.e., the time ratio between the lifetimes of the carrier density (population inversion) and the photons, is crucial to fluctuation dynamics. 相似文献
80.
Kon N Takemura H Otsuka K Tanoue K Nakashima S Yasutake M Tani K Kimoto J Shinmyozu T Inazu T 《The Journal of organic chemistry》2000,65(12):3708-3715
Macropolycyclic cage compounds were synthesized by a direct reaction between diamines and bis(bromomethyl) compounds. The procedure for constructing the polycyclic cage structure is simple and straightforward. The macropolycyclic compounds obtainable from this cyclization procedure are three-dimensional cage compounds, and any other isomers were not obtained except for two examples. Benzene, pyridine, and aliphatic units could be introduced into the cage structure. The macrocycles that have strong cation affinity were obtained as their potassium complexes. 相似文献