全文获取类型
收费全文 | 603篇 |
免费 | 11篇 |
国内免费 | 5篇 |
专业分类
化学 | 430篇 |
晶体学 | 16篇 |
力学 | 2篇 |
数学 | 34篇 |
物理学 | 137篇 |
出版年
2023年 | 3篇 |
2022年 | 4篇 |
2021年 | 3篇 |
2020年 | 3篇 |
2019年 | 6篇 |
2018年 | 3篇 |
2016年 | 10篇 |
2015年 | 11篇 |
2014年 | 12篇 |
2013年 | 25篇 |
2012年 | 19篇 |
2011年 | 28篇 |
2010年 | 13篇 |
2009年 | 15篇 |
2008年 | 19篇 |
2007年 | 33篇 |
2006年 | 32篇 |
2005年 | 36篇 |
2004年 | 25篇 |
2003年 | 32篇 |
2002年 | 30篇 |
2001年 | 10篇 |
2000年 | 4篇 |
1999年 | 11篇 |
1998年 | 4篇 |
1997年 | 16篇 |
1996年 | 6篇 |
1995年 | 10篇 |
1994年 | 3篇 |
1993年 | 7篇 |
1992年 | 5篇 |
1991年 | 7篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 10篇 |
1987年 | 7篇 |
1986年 | 13篇 |
1985年 | 10篇 |
1984年 | 10篇 |
1983年 | 9篇 |
1982年 | 11篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1978年 | 15篇 |
1977年 | 11篇 |
1976年 | 10篇 |
1975年 | 7篇 |
1974年 | 7篇 |
1973年 | 11篇 |
排序方式: 共有619条查询结果,搜索用时 15 毫秒
561.
En Zhang Natalia Fulik Guang‐Ping Hao Han‐Yue Zhang Katsumi Kaneko Lars Borchardt Eike Brunner Stefan Kaskel 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(37):13194-13199
A new asymmetric capacitor concept is proposed providing high energy storage capacity for only one charging direction. Size‐selective microporous carbons (w<0.9 nm) with narrow pore size distribution are demonstrated to exclusively electrosorb small anions (BF4?) but size‐exclude larger cations (TBA+ or TPA+), while the counter electrode, an ordered mesoporous carbon (w>2 nm), gives access to both ions. This architecture exclusively charges in one direction with high rectification ratios (RR=12), representing a novel capacitive analogue of semiconductor‐based diodes (“CAPode”). By precise pore size control of microporous carbons (0.6 nm, 0.8 nm and 1.0 nm) combined with an ordered mesoporous counter electrode (CMK‐3, 4.8 nm) electrolyte cation sieving and unidirectional charging is demonstrated by analyzing the device charge‐discharge response and monitoring individual electrodes of the device via in situ NMR spectroscopy. 相似文献
562.
Yuya Nishio Kotaro Yubata Yutaro Wakai Kotaro Notsu Katsumi Yamamoto Hideki Fujiwara Hiroshi Matsubara 《Tetrahedron》2019,75(10):1398-1405
Although molecular bromine (Br2) is a useful brominating reagent, it is not easy to handle. Herein, we describe the preparation of a novel air-stable bromine complex prepared from 1,3-dimethyl-2-imidazolidinone (DMI) and Br2, which was identified to be (DMI)2HBr3 by spectral and X-ray techniques. This complex was then used to brominate olefins, carbonyl compounds, and aromatics, as well as in the Hofmann rearrangement. Yields of reaction products using this complex were almost the same or superior to those using other bromine alternatives. 相似文献
563.
Tanaka H Kanoh H Yudasaka M Iijima S Kaneko K 《Journal of the American Chemical Society》2005,127(20):7511-7516
H(2) and D(2) adsorption on single-wall carbon nanohorns (SWNHs) have been measured at 77 K, and the experimental data were compared with grand canonical Monte Carlo simulations for adsorption of these hydrogen isotopes on a model SWNH. Quantum effects were included in the simulations through the Feynman-Hibbs effective potential. The simulation predictions show good agreement with the experimental results and suggest that the hydrogen isotope adsorption at 77 K can be successfully explained with the use of the effective potential. According to the simulations, the hydrogen isotopes are preferentially adsorbed in the cone part of the SWNH with a strong potential field, and quantum effects cause the density of adsorbed H(2) inside the SWNH to be 8-26% smaller than that of D(2). The difference between H(2) and D(2) adsorption increases as pressure decreases because the quantum spreading of H(2), which is wider than that of D(2), is fairly effective at the narrow conical part of the SWNH model. These facts indicate that quantum effects on hydrogen adsorption depend on pore structures and are very important even at 77 K. 相似文献
564.
Ohkubo T Konishi T Hattori Y Kanoh H Fujikawa T Kaneko K 《Journal of the American Chemical Society》2002,124(40):11860-11861
Hydration structures of "nanosolutions" around both cation and anion for rubidium bromide confined in nanospaces (pore width = 1.1 nm) of activated carbon fiber were determined with EXAFS measurements and related analysis. The analytical results indicate that the ionic solutions confined in hydrophobic nanospaces tend to form an incomplete dehydration structure, because of the spatial restriction by the nanospace and capturing water molecules in the ordered structure. 相似文献
565.
We demonstrate delayed four-wave Raman mixing in hydrogen gas and discuss the polarization of multiple rotational Raman radiation in the sub-100-fs regime. The mechanism of sideband generation through the interaction between a probe pulse and coherence of molecular motions induced by a pump pulse in hydrogen is revealed. One can artificially control the ellipticity of the polarization of the rotational Raman sidebands by changing the pump pulse polarization. 相似文献
566.
We demonstrate the generation of 10-microJ coherent extreme-ultraviolet (XUV) light at wavelengths from 73.6 to 42.6 nm, using high-order harmonics. The peak power of this coherent XUV light is estimated to be 0.13 GW at 62.3 nm, and the peak brightness achieved was 3x10(28) photons/(mm(2)mrad(2)s) . To our knowledge, this XUV energy is the highest value achieved with high-order harmonics. 相似文献
567.
Hiroyuki Tsuda Katsumi Fukamachi Jiegou Xu Kazunori Sekine Shigetoshi Ohkubo Nobuo Takasuka Masaaki Iigo 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2006,82(7):208-215
Increasing attention is being paid to chemopreventive agents for individuals at high risk of cancer. We have concentrated on bovine lactoferrin (bLF), an 80 kDa iron-binding glycoprotein known to have anti-microbial and immunoprotective effects. Lactoferrin is particularly abundant in colostrum, and is also present in tears, saliva and seminal and uterine secretions. However, only little is known regarding its influence on carcinogenesis. We have shown preventive effects of bLF and its fragment peptide, lactoferricin (bLFcin), consisting of a 25 amino acid sequence without iron binding capacity, on chemically-induced colon carcinogenesis in the rat and transplanted carcinoma cell metastasis in the mouse. The mechanisms are wide-spectrum, including elevation of caspase-1 and IL-18 in the small intestine, enhancement of the cell killing activity of cytotoxic T and natural killer (NK) cells, and anti-inflammatory and anti-angiogenic effects. It also inhibits the induction of liver CYP1A2, a carcinogen activating enzyme, and induces apoptosis in the colon epithelium of carcinogen treated rats. Thus, bLF possesses multi-functional potential to suppress carcinogenesis and is a good candidate for practical application in humans. 相似文献
568.
Basic configurations and system requirements for subcarrier multiplexing (SCM)-based optically fed wireless communication systems are summarized. The key issues for their fast deployment are improving performance and reducing the initial introduction cost. Major enabling technologies are introduced such as development of highly linear LDs, the multiple-LD method to improve carrier-to-noise ratio (CNR), super wideband frequency modulation to obtain a large power margin, and low-cost feeder design with a Fabry–Perot LD and multimode fiber. The introduction of optical feeders, which will increase the flexibility of the wireless system, is inevitable for providing multimedia services. 相似文献
569.
Two kinds of cross-linked chitosan beads were evaluated as the stationary phase for microcolumn liquid chromatography. The phase with aminoalkyl substituent can be expected to function similarly to commonly known aminopropyl bonded phases. Separation of PAH with the chitosan phase bearing phenyl group substituents has been accomplished in the gradientelution mode with acetonitrile-water as the mobile phase. Planarity recognition capability comparable with that of monomeric octadecylsilica phase was observed. 相似文献
570.
We demonstrate a high-throughput and high-damage-threshold beam splitter for high-order harmonics in the soft-x-ray region that uses Si and (or) SiC plates set at Brewster's angle with respect to the pump wavelength. The beam splitters are guaranteed to have a damage threshold of at least 0.8 TW/cm2 (average power density, 0.25 W/cm2) and an attenuation rate of 10(-4)-10(-5) for a 30-fs pump pulse. The measured reflection efficiency at the 27th harmonic (29.6 nm) was 0.56 for Si and 0.45 for SiC. These beam splitters are useful not only for high harmonics but also for longitudinally pumped x-ray lasers. 相似文献