全文获取类型
收费全文 | 1043篇 |
免费 | 28篇 |
国内免费 | 4篇 |
专业分类
化学 | 661篇 |
晶体学 | 13篇 |
力学 | 31篇 |
数学 | 11篇 |
物理学 | 359篇 |
出版年
2023年 | 3篇 |
2022年 | 8篇 |
2021年 | 8篇 |
2020年 | 15篇 |
2019年 | 10篇 |
2018年 | 11篇 |
2017年 | 8篇 |
2016年 | 14篇 |
2015年 | 12篇 |
2014年 | 19篇 |
2013年 | 64篇 |
2012年 | 55篇 |
2011年 | 54篇 |
2010年 | 26篇 |
2009年 | 47篇 |
2008年 | 76篇 |
2007年 | 78篇 |
2006年 | 70篇 |
2005年 | 66篇 |
2004年 | 51篇 |
2003年 | 46篇 |
2002年 | 44篇 |
2001年 | 21篇 |
2000年 | 15篇 |
1999年 | 12篇 |
1998年 | 11篇 |
1997年 | 8篇 |
1996年 | 29篇 |
1995年 | 15篇 |
1994年 | 12篇 |
1993年 | 4篇 |
1992年 | 10篇 |
1991年 | 8篇 |
1990年 | 8篇 |
1988年 | 4篇 |
1987年 | 13篇 |
1984年 | 5篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 10篇 |
1979年 | 10篇 |
1978年 | 7篇 |
1977年 | 8篇 |
1976年 | 10篇 |
1974年 | 7篇 |
1973年 | 11篇 |
1972年 | 5篇 |
1971年 | 9篇 |
1970年 | 4篇 |
1967年 | 6篇 |
排序方式: 共有1075条查询结果,搜索用时 15 毫秒
61.
Channing C. Pletka Dr. Ridvan Nepravishta Prof. Junji Iwahara 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(4):1481-1484
Due to a high density of negative charges on its surface, DNA condenses cations as counterions, forming the so-called “ion atmosphere”. Although the release of counterions upon DNA–protein association has been postulated to have a major contribution to the binding thermodynamics, this release remains to be confirmed through a direct observation of the ions. Herein, we report the characterization of the ion atmosphere around DNA using NMR spectroscopy and directly detect the release of counterions upon DNA–protein association. NMR-based diffusion data reveal the highly dynamic nature of counterions within the ion atmosphere around DNA. Counterion release is observed as an increase in the apparent ionic diffusion coefficient, which directly provides the number of counterions released upon DNA–protein association. 相似文献
62.
Toshiki Yoshizawa Michika Onoda Takeshi Ueki Ryota Tamate Aya Mizutani Akimoto Ryo Yoshida 《Angewandte Chemie (International ed. in English)》2020,59(10):3871-3875
Various biological behaviors are fueled by “respiration”, which is an example of catabolism. So far, we have reported various self‐oscillating soft materials exhibiting bioinspired dynamic movements. These autonomous polymer systems are driven by the Belousov–Zhabotinsky (BZ) reaction, which is analogous to the tricarboxylic acid (TCA) cycle that is an integral part of respiration. However, in the BZ reaction, the external addition of an oxidizing agent is necessary to initiate the oxidation process, which is realized by intracellular moieties such as ubiquinone in living systems. Herein, we realized self‐oscillating micelles that are driven without the external addition of an oxidizing agent. This was achieved by embedding the oxidizing source into the structure of the self‐oscillating AB diblock copolymers. This strategy introduces a new function equivalent to intracellular oxidizing moieties, and is useful for the design of completely autonomous bioinspired materials. 相似文献
63.
Toru Doi Akira Akimoto Akikazu Matsumoto Takayuki Otsu 《Journal of polymer science. Part A, Polymer chemistry》1996,34(3):367-373
Radical copolymerization of N-methylmaleimide (MeMI) as well as other N-alkylmaleimides (RMI) and isobutene (IB) was carried out with 2,2′-azobis(isobutyronitrile) as an initiator at 60°C. The initial rate of the copolymerization (Rp) was dependent on the monomer composition and was maximum at the 40 mol % of MeMI in the feed. A solvent effect on the Rp and the monomer reactivity ratio was observed in this copolymerization system, i.e., copolymerization in chloroform produced a higher Rp and an alternating tendency compared with those in dioxane (rMeMI = 0.14, r1B = 0 in chloroform and rMeMI = 0.47, r1B = 0 in dioxane). The alternating copolymer of RMI and IB shows a high glass transition temperature (Tg) and excellent thermal stability, e.g., the Tg and the thermal decomposition temperature (Td) were 152 and 363°C, respectively, for the alternating copolymer of MeMI and IB. Both the Tg and Td increased as the concentration of the MeMI unit in the copolymers increased. Colorless transparent sheets were obtained from press molding the alternating copolymers. They showed excellent mechanical and optical properties. © 1996 John Wiley & Sons, Inc. 相似文献
64.
65.
Organic electroluminescent devices were fabricated using a poly(arylene ether sulfone)-containing tetraphenylbenzidine (PTPDES) and tris(8-quinolinolato)-aluminum(III) complex, Alq, as the hole transport layer and the electron-transporting emitter layer, respectively. A device structure of glass substrate/indium—tin oxide (ITO)/PTPDES/Alq/Mg : Ag was employed. Hole injection from ITO through the PTPDES layer to the Alq layer and concomitant electroluminescence from the Alq layer were observed. Bright green light with a luminance of 14,000 cd/m2 was observed at a drive voltage of 14 V, indicating that the polymer possesses a high hole mobility and a high electron-blocking capability. 相似文献
66.
67.
Masahisa Wada Takeshi Okano Junji Sugiyama Fumitaka Horii 《Cellulose (London, England)》1995,2(4):223-233
We have investigated unlignified tension wood and normally lignified wood celluloses inPopulus maximowiczii with particular reference to the composition of two crystalline phases I/I (triclinic/ monoclinic). Four independent techniques, which enable us to detect the two phases, CP/MAS13C NMR, Fourier transform infrared microscopy, selected-area electron diffraction, and X-ray diffraction were applied. Because of the low crystallinity of wood celluloses, particularly in the case of celluloses in the lignified cell wall, no single method was decisive enough to be able to determine the composition of the two phases as one can with highly crystalline materials. The I dominant structure (monoclinic crystal type) was, however, preferred for both tension and normal wood celluloses. 相似文献
68.
SPATIAL AND SEASONAL DISTRIBUTIONS OF ATMOSPHERIC CARBONACEOUS AEROSOLS IN PEARL RIVER DELTA REGION, CHINA 总被引:11,自引:0,他引:11
Concentrations and spatial distributions of organic carbon (OC) and elemental carbon (EC) in atmospheric particles were measured at 8 sites in four cities (Hong Kong, Guangzhou, Shenzhen and Zhuhai) of Pearl River Delta Region (PRDR), China during 2001 winter period and 2002 summer period. PM2.5 (particie diameter smaller than 2.5 um) and PM10 (particie diameter smaller than 10 um) samples were collected on pre-fired quartz filters with mini-volume samplers and analyzed using thermal optical reflectance (TOR) method. The average PM2.5and PM10 Ievel were 60.1 and 93.1 μg·m-3, respectively, with PM2.5 constituting 65.3% of the PM10 mass. The average OC and EC concentrations in PM2.5 were 12.0 and 5.1 μg·m-3, respectively, while those in PM10 were 16.0 and 6.5 μg·m-3, respectively. The carbo-naceous aerosol accounted for 37.2% of the PM2.5 and 32.8% of the PM10. The highest concentrations of OC and EC were observed at Guangzhou city in both vvinter and summer seasons. The average OC/EC ratios were 2. 相似文献
69.
Characteristics of uranium sorption on illite in a ternary system: effect of phosphate on adsorption
Liao Rong Shi Zeming Chen Yuejiao Zhang Junji Wang Xinyu Hou Yun Zhang Kailiang 《Journal of Radioanalytical and Nuclear Chemistry》2020,324(1):159-167
Journal of Radioanalytical and Nuclear Chemistry - Na, Mg, Al and Cl in Roman glasses and pottery were analyzed by PIGE with 2.5 MeV protons and 2.0 MeV deuteron activation... 相似文献
70.