全文获取类型
收费全文 | 471篇 |
免费 | 13篇 |
国内免费 | 1篇 |
专业分类
化学 | 351篇 |
晶体学 | 3篇 |
力学 | 13篇 |
数学 | 55篇 |
物理学 | 63篇 |
出版年
2021年 | 2篇 |
2020年 | 7篇 |
2019年 | 5篇 |
2018年 | 2篇 |
2017年 | 6篇 |
2016年 | 6篇 |
2015年 | 9篇 |
2014年 | 13篇 |
2013年 | 20篇 |
2012年 | 26篇 |
2011年 | 28篇 |
2010年 | 13篇 |
2009年 | 14篇 |
2008年 | 29篇 |
2007年 | 33篇 |
2006年 | 33篇 |
2005年 | 22篇 |
2004年 | 27篇 |
2003年 | 14篇 |
2002年 | 25篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 8篇 |
1997年 | 2篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1992年 | 10篇 |
1991年 | 8篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1985年 | 10篇 |
1984年 | 11篇 |
1982年 | 10篇 |
1981年 | 8篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 7篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1974年 | 6篇 |
1973年 | 4篇 |
1968年 | 2篇 |
1964年 | 2篇 |
1959年 | 1篇 |
排序方式: 共有485条查询结果,搜索用时 31 毫秒
91.
Yoshikazu Okamoto Graham J. Kemp Tomonori Isobe Eisuke Sato Yuji Hirano Junichi Shoda Manabu Minami 《Magnetic resonance imaging》2014
Several studies have proposed the cell membrane as the main water diffusion restricting factor in the skeletal muscle cell. We sought to establish whether a particular form of exercise training (which is likely to affect only intracellular components) could affect water diffusion. The purpose of this study is to characterise prospectively the changes in diffusion tensor imaging (DTI) eigenvalues of thigh muscle resulting from hybrid training (HYBT) in patients with non-alcoholic fatty liver disease (NAFLD). Twenty-one NAFLD patients underwent HYBT for 30 minutes per day, twice a week for 6 months. Patients were scanned using DTI of the thigh pre- and post-HYBT. Fractional anisotropy (FA), apparent diffusion coefficient (ADC), the three eigenvalues lambda 1 (λ1), λ2, λ3, and the maximal cross sectional area (CSA) were measured in bilateral thigh muscles: knee flexors (biceps femoris (BF), semitendinosus (ST), semimembranous (SM)) and knee extensors (medial vastus (MV), intermediate vastus (IV), lateral vastus (LV), and rectus femoris (RF)), and compared pre- and post-HYBT by paired t-test. Muscle strength of extensors (P < 0.01), but not flexors, increased significantly post-HYBT. For FA, ADC and eigenvalues, the overall picture was of increase. Some (P < 0.05 in λ2 and P < 0.01 in λ1) eigenvalues of flexors and all (λ1-λ3) eigenvalues of extensors increased significantly (P < 0.01) post-HYBT. HYBT increased all 3 eigenvalues. We suggest this might be caused by enlargement of muscle intracellular space. 相似文献
92.
K Mori K Watanabe Y Terai Y Fujiwara H Yamashita 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(36):11371-11378
[Pt(tpy)Cl]Cl (tpy: terpyridine) was successfully anchored to a series of mesoporous-silica materials that were modified with (3-aminopropyl)triethoxysilane with the aim of developing new inorganic-organic hybrid photocatalysts. Herein, the relationship between the luminescence characteristics and photocatalytic activities of these materials is examined as a function of Pt loading to define the spatial distribution of the Pt complex in the mesoporous channel. At low Pt loading, the Pt complex is located as an isolated species and exhibits strong photoluminescence emission at room temperature owing to metal-to-ligand charge-transfer ((3) MLCT) transitions (at about 530?nm). Energy- and/or electron-transfer from (3) MLCT to O(2) generate potentially active oxygen species, which are capable of promoting the selective photooxidation of styrene derivatives. On the other hand, short Pt???Pt interactions are prominent at high loading and the metal-metal-to-ligand charge-transfer ((3) MMLCT) transition is at about 620?nm. Such Pt complexes, which are situated close to each other, efficiently catalyze H(2) -evolution reactions in aqueous media in the presence of a sacrificial electron donor (EDTA) under visible-light irradiation. This study also investigates the effect of nanoconfinement on anchored guest complexes by considering the differences between the pore dimensions and structures of mesoporous-silica materials. 相似文献
93.
Yoshikazu AritakeTakashiro Akitsu 《Polyhedron》2012,31(1):278-284
Chiral Schiff base complexes containing azo-groups, bis(N-R-1-cyclohexylethyl-4-phenyldiazenylsalicydenaminato) nickel(II), copper(II) and zinc(II) complexes, and without azo-groups, bis(N-R-1-cyclohexylethyl-3,5-dichlorosalicydenaminato) nickel(II), copper(II) and zinc(II) complexes, affording a distorted square planar trans-[MN2O2] coordination geometry were prepared. Organic/inorganic hybrid materials in polymethylmethacrylate (PMMA) spincoat films of the complexes (both the azobenzene (AZ) containing type and the latter complexes of the AZ separated type) were assembled for a comparison of polarized UV light induced molecular arrangement caused by the Weigert effect. Investigation of the parameters for the optical anisotropy of the metal complexes as well as AZ suggested that the degree of increasing optical anisotropy of the containing type was higher than that of the separated type based on π-π∗ (of which a characteristic band appeared around 380 nm) and n-π∗ bands of polarized absorption electronic spectra. In the AZ containing type, the rigid nickel(II) or zinc(II) complexes easily increase the optical anisotropy compared to the flexible copper(II) complexes. In the AZ separated type, interestingly, enhancement of some CD bands suggests the role of chiral dopants of some complexes without azo-groups for AZ. 相似文献
94.
Ui M Tanaka Y Araki Y Wada T Takei T Tsumoto K Endo S Kinbara K 《Chemical communications (Cambridge, England)》2012,48(39):4737-4739
A chimeric protein (N-PYP-Hla), consisting of staphylococcal pore-forming toxin α-hemolysin (Hla) and photoactive yellow protein (PYP), exhibited photoresponsive hemolytic activities, where visible light irradiation gave rise to retardation of hemolysis at 25 °C. 相似文献
95.
Hyung Woo Choi Yasuhiko Sakata Yoshikazu Kurihara Tooru Ooya Toshifumi Takeuchi 《Analytica chimica acta》2012
Reflectometric interference spectroscopy (RIfS) is a label-free, time-resolved technique, and suitable for detecting antibody–antigen interaction. This work describes a continuous flow biosensor for C-reactive protein (CRP), involving an effective immobilization method of a monoclonal antibody against CRP (anti-CRP) to achieve highly sensitive RIfS-based detection of CRP. The silicon nitride-coated silicon chip (SiN chip) for the RIfS sensing was first treated with trimethylsilylchloride (TMS), followed by UV-light irradiation to in situ generation of homogeneous silanols on the surface. Following amination by 3-aminopropyltriethoxysilane, carboxymethyldextran (CMD) was grafted, and subsequently, protein A was immobilized to create the oriented anti-CRP surface. The immobilization process of protein A and anti-CRP was monitored with the RIfS system by consecutive injections of an amine coupling reagent, protein A and anti-CRP, respectively, to confirm the progress of each step in real time. The sensitivity was enhanced when all of the processes were adopted, suggesting that the oriented immobilization of anti-CRP via protein A that was coupled with the grafted CMD on the aminated surface of TMS-treated SiN chip. The feasibility of the present sensing system was demonstrated on the detection of CRP, where the silicon-based inexpensive chips and the simple optical setup were employed. It can be applied to other target molecules in various fields of life science as a substitute of surface plasmon resonance-based expensive sensors. 相似文献
96.
Yoshikazu Suzuki Paola Laurino D. Tyler McQuade Peter H. Seeberger 《Helvetica chimica acta》2012,95(12):2578-2588
Supported transition‐metal catalysts offer the promise of catalyst reuse in order to make chemical transformations more environmentally friendly and less expensive; however, catalysts that are supported on insoluble scaffolds often exhibit significantly reduced selectivities and rates. A capture/release strategy that unites the benefits of heterogeneous and homogeneous catalysis would overcome these current shortcomings. Herein, we report on a novel capture‐and‐release flow system that takes advantage of a non‐covalent pyrene? single wall nanotube (SWNT) interaction. We demonstrate that a Pd complex containing one or two pyrene arms is captured and released from a SWNT column at different rates and can be utilized for the homogeneous catalysis of Suzuki and Heck reactions. 相似文献
97.
Yamaguchi T Watanabe S Matsumura Y Tokuoka Y Yokoyama A 《Chemical & pharmaceutical bulletin》2012,60(4):508-512
Vanadium complexes with different ligands were synthesized and evaluated for antiproliferative activity on U937 cells. The alkyl chain length of the ligands affected the antiproliferative activity, and two complexes-3b and 4-exhibited strong activities with IC(50) values of 6.02 and 3.90 μM respectively. Annexin V staining and DNA ladder formation indicated that these complexes induced apoptosis in U937 cells. 相似文献
98.
Yasumori Atsuo Katsuyama Tomokazu Kameshima Yoshikazu Okada Kiyoshi 《Journal of Sol-Gel Science and Technology》2000,19(1-3):237-242
Composite materials which consist of ferro- or ferrimagnetic fine particles in a glass matrix are expected to have a large residual magnetization and coercive force because of their fine magnetic domain structure, and has potential for superior magneto-optical properties compared with single or polycrystalline materials. In this study, the sodium borosilicate (NBS) glass containing Bi-substituted yttrium iron garnet (Bi
x
Y3–x
Fe5O12: BiYIG) fine particles, which show a superior magneto-optical effect, was prepared by the sol-gel method. BiYIG fine particles were stable in NBS gel-glass matrix during densification because the sintering temperature (580°C) of NBS gel was low enough to avoid pyrolysis of BiYIG and the reaction between BiYIG fine particles and the matrix. The Faraday rotation angle spectrum of the composite after deducting the contribution of the NBS glass matrix was intermediate between the reported ones of YIG and Bi0.25YIG polycrystalline thin films. The change of the Faraday rotation angles of the composite with imposing magnetic field showed a hysteresis loop. It was in good agreement with that of the magnetization curve of the composite. 相似文献
99.
Chaotic dynamics in systems having many degrees of freedom are investigated from the viewpoint of harnessing chaos and is applied to complex control problems to indicate that chaotic dynamics has potential capabilities for complex control functions by simple rule(s). An important idea is that chaotic dynamics generated in these systems give us autonomous complex pattern dynamics itinerating through intermediate state points between embedded designed attractors in high-dimensional state space. A key point is that, with the use of simple adaptive switching between a weakly chaotic regime and a strongly chaotic regime, complex problems can be solved. As an actual example, a two-dimensional maze, where it should be noted that the set context is one of typical ill-posed problems, is solved with the use of chaos in a recurrent neural network model. Our computer experiments show that the success rate over several hundreds trials is much better, at least, than that of a random number generator. Our functional simulations indicate that harnessing of chaos is one of essential ideas to approach mechanisms of brain functions. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
100.