全文获取类型
收费全文 | 851篇 |
免费 | 57篇 |
国内免费 | 3篇 |
专业分类
化学 | 738篇 |
晶体学 | 8篇 |
力学 | 3篇 |
数学 | 82篇 |
物理学 | 80篇 |
出版年
2023年 | 3篇 |
2022年 | 13篇 |
2021年 | 14篇 |
2020年 | 25篇 |
2019年 | 12篇 |
2018年 | 15篇 |
2017年 | 11篇 |
2016年 | 26篇 |
2015年 | 30篇 |
2014年 | 31篇 |
2013年 | 46篇 |
2012年 | 65篇 |
2011年 | 77篇 |
2010年 | 34篇 |
2009年 | 31篇 |
2008年 | 57篇 |
2007年 | 63篇 |
2006年 | 54篇 |
2005年 | 46篇 |
2004年 | 48篇 |
2003年 | 42篇 |
2002年 | 30篇 |
2001年 | 5篇 |
2000年 | 5篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1996年 | 7篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1991年 | 6篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1979年 | 6篇 |
1977年 | 8篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1974年 | 5篇 |
1973年 | 3篇 |
1972年 | 8篇 |
1971年 | 2篇 |
1969年 | 3篇 |
1967年 | 6篇 |
1962年 | 2篇 |
排序方式: 共有911条查询结果,搜索用时 125 毫秒
81.
82.
83.
84.
A sealed tube dry combustion method that is simple, accurate, and precise for ultramicro determination of halogens in organic compounds has been developed. Samples below 1 mg are heated at 580 °C for 1 h in an electric furnace. After the combustion and absorption of the gaseous halogen, the interior of the tube is rinsed. Subsequent titration is carried out potentiometrically with silver nitrate and yielded standard deviations of 0.21% for chlorine, 0.17% for bromine, and 0.25% for iodine. 相似文献
85.
K Ukawa E Imamiya H Yamamoto T Aono Y Kozai T Okutani H Nomura Y Honma M Hozumi I Kudo 《Chemical & pharmaceutical bulletin》1989,37(12):3277-3285
A new series of amphiphilic 1-octadecyl glycerolipids (eleven compounds, 1a-k) were designed and synthesized, in which the 3-phosphocholine portion of platelet-activating factor (1-alkyl-2-acetyl-sn-glycero-3-phosphocholine, PAF) was replaced by the 2-(2-trimethylammonioethoxy)ethyl group and congeneric groups having oligo(ethyleneoxy)ethyl bridges of various lengths at position 3, together with modification at position 2 (lower alkyl, acetonyl, acetoacetyl, carboxymethyl and pyrimidin-2-yl groups). These ether lipids, characterized by a nonphosphorus lysoglycerolipid structure, showed potent antitumor activity in vitro (human promyelocytic leukemia cells, HL-60, and human epidermoid carcinoma cells, KB) and in vivo (mouse sarcoma S180 and mouse mammary carcinoma MM46). Maximal in vitro potency was obtained with 1-O-octadecyl-2-O-(2-pyrimidinyl)-3-O-[2-(2-trimethylammonioethoxy )ethyl] glycerol (1g; IC50 values for both HL-60 and KB were 0.32 microgram/ml, indicating a higher activity than alkyl-lysophospholipid, ET18-OMe). Several appropriately 2-substituted 1-octadecylglycerolipids with the 3-[2-(2-trimethylammonioethoxy)ethyl] group (e.g., methyl, 1b; butyl, 1f; 2,2,2-trifluoroethyl, 1j; and acetonyl, 1k) showed a potent life-span-prolonging effect on mice with ascites sarcoma S180 and on those with mammary carcinoma MM46, when administered intraperitoneally at 16.5 and 12.5 mg/kg/d, respectively. Compounds 1b and 1k showed definite tumor growth inhibition against solid sarcoma S180 in mice, whether given p.o. or i.v. at 16.5 mg/kg/d. Studies on the structure-activity relationships indicate that the metabolic stability to phospholipase C or related enzymes is at least partly responsible for the potent antitumor activity of this series of ether lipids. 相似文献
86.
Manabu Kiguchi Tatsuya Konishi Shinichi Miura Kei Murakoshi 《Physica E: Low-dimensional Systems and Nanostructures》2005,29(3-4):530
We have mechanically fabricated Ni and Cu nano-constrictions in solution to study their quantized conductance behavior under electrochemical potential control. Conductance quantization was observed at both metals in solution at room temperature for the first time. The conductance of Cu nano-constriction was quantized in units of G0(=2e2/h). A sharp 1G0 peak was observed in the conductance histogram. For Ni, a rather broad peak at 1–1.5G0 was observed in the histogram. The conductance quantization behavior was discussed by comparing previously documented results of nano-constrictions fabricated in air or ultra-high vacuum conditions, with those fabricated in solution. 相似文献
87.
Dr. Kei Kitamura Dr. Naoyuki Shimada Dr. Craig Stewart Dr. Abdurrahman C. Atesin Prof. Tülay A. Ateşin Prof. Dr. Marcus A. Tius 《Angewandte Chemie (International ed. in English)》2015,54(21):6288-6291
A Pd0‐catalyzed asymmetric Nazarov‐type cyclization is described. The optimized ligand for the reaction incorporates a weakly coordinating pyridine ring into a TADDOL‐derived phosphoramidite (TADDOL=α,α,α,α‐tetraaryl‐1,3‐dioxolane‐4,5‐dimethanol). The reaction leads to the formation of cyclopentenones as single diastereoisomers that incorporate two contiguous asymmetric centers, one tertiary and one an all‐carbon‐atom quaternary stereocenter, in high yield and optical purity. It is noteworthy that the reaction does not require that substrates should be activated by aryl substituents. 相似文献
88.
Back Cover: CH Activation Generates Period‐Shortening Molecules That Target Cryptochrome in the Mammalian Circadian Clock (Angew. Chem. Int. Ed. 24/2015)
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Tsuyoshi Oshima Dr. Iori Yamanaka Dr. Anupriya Kumar Dr. Junichiro Yamaguchi Dr. Taeko Nishiwaki‐Ohkawa Kei Muto Rika Kawamura Dr. Tsuyoshi Hirota Prof. Dr. Kazuhiro Yagita Prof. Dr. Stephan Irle Prof. Dr. Steve A. Kay Prof. Dr. Takashi Yoshimura Prof. Dr. Kenichiro Itami 《Angewandte Chemie (International ed. in English)》2015,54(24):7200-7200
89.
Supramolecular Polyelectrolyte Complexes of Bone Morphogenetic Protein‐2 with Sulfonated Polyrotaxanes to Induce Enhanced Osteogenic Differentiation
下载免费PDF全文
![点击此处可从《Macromolecular bioscience》网站下载免费的PDF全文](/ch/ext_images/free.gif)
90.
This paper is a review of the recent progress on gas sensors using graphene oxide (GO). GO is not a new material but its unique features have recently been of interest for gas sensing applications, and not just as an intermediate for reduced graphene oxide (RGO). Graphene and RGO have been well known gas-sensing materials, but GO is also an attractive sensing material that has been well studied these last few years. The functional groups on GO nanosheets play important roles in adsorbing gas molecules, and the electric or optical properties of GO materials change with exposure to certain gases. Addition of metal nanoparticles and metal oxide nanocomposites is an effective way to make GO materials selective and sensitive to analyte gases. In this paper, several applications of GO based sensors are summarized for detection of water vapor, NO2, H2, NH3, H2S, and organic vapors. Also binding energies of gas molecules onto graphene and the oxygenous functional groups are summarized, and problems and possible solutions are discussed for the GO-based gas sensors. 相似文献