全文获取类型
收费全文 | 880篇 |
免费 | 20篇 |
国内免费 | 97篇 |
专业分类
化学 | 960篇 |
晶体学 | 12篇 |
力学 | 1篇 |
综合类 | 3篇 |
物理学 | 21篇 |
出版年
2024年 | 1篇 |
2023年 | 6篇 |
2022年 | 9篇 |
2021年 | 15篇 |
2020年 | 19篇 |
2019年 | 29篇 |
2018年 | 18篇 |
2017年 | 27篇 |
2016年 | 18篇 |
2015年 | 21篇 |
2014年 | 40篇 |
2013年 | 82篇 |
2012年 | 41篇 |
2011年 | 43篇 |
2010年 | 27篇 |
2009年 | 29篇 |
2008年 | 47篇 |
2007年 | 43篇 |
2006年 | 52篇 |
2005年 | 55篇 |
2004年 | 60篇 |
2003年 | 45篇 |
2002年 | 42篇 |
2001年 | 35篇 |
2000年 | 32篇 |
1999年 | 28篇 |
1998年 | 25篇 |
1997年 | 25篇 |
1996年 | 21篇 |
1995年 | 13篇 |
1994年 | 11篇 |
1993年 | 11篇 |
1992年 | 15篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1973年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有997条查询结果,搜索用时 14 毫秒
971.
972.
Eiji Ihara Shinsuke Tanaka Kenzo Inoue 《Journal of polymer science. Part A, Polymer chemistry》2002,40(23):4302-4315
Molybdenum chloride (MoCl5 or 1a ) and tungsten chloride (WCl6 or 1b )/phenyllithium (PhLi)/triisobutylaluminum (iBu3Al) systems were found to be quite effective for controlling the anionic polymerization of methyl methacrylate (MMA), affording high molecular weight poly(methyl methacrylate)s (PMMAs; number‐average molecular weight > 100,000) with narrow molecular weight distributions (weight‐average molecular weight/number‐average molecular weight < 1.25) quantitatively at 0 °C for 1 h in toluene. Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) analyses of PMMAs obtained with the 1a and 1b /organolithium (RM; n‐butyllithium, PhLi)/iBu3Al systems revealed that the initiation of MMA with the systems occurred by a nucleophilic attack of H? to the monomer. In addition, the MALDI‐TOF MS analyses indicated that the presence of iBu3Al was responsible for the controlled polymerization by improving the uniformity of the polymerization with respect to initiation and termination and by preventing a backbiting reaction. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4302–4315, 2002 相似文献
973.
Itaru Natori Shizue Natori Anna Kanasashi Kosuke Tsuchiya Kenji Ogino 《Journal of Polymer Science.Polymer Physics》2013,51(5):368-375
Thin films composed of zinc tetraphenylporphyrin-end-functionalized polycyclohexane (ZnTPP-PCHE) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blends were prepared to investigate their potential as light-harvesting systems within polymer solar cells (PSCs). Both the microphase separation characteristics and the extent of π–π interactions in these ZnTPP-PCHE/PCBM blends had significant effects on the optical properties of the films. The extent to which the absorption bands of the films overlapped the terrestrial solar spectrum was increased considerably when the blends formed a co-continuous structure, even though films of pure ZnTPP-PCHE or PCBM exhibited only weak absorption over that wavelength region. We conclude that these polymer blend films may be considered as viable candidates for light-harvesting systems within PSCs. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013 相似文献
974.
Takeru Iwamura Kazufumi Ashizawa Kaoru Adachi Masato Takasaki 《Journal of polymer science. Part A, Polymer chemistry》2019,57(24):2415-2419
Anionic hydrogen‐transfer homopolymerization of N‐isopropylacrylamide (NIPAAm) was carried out using t‐BuOK as an initiator in DMF under microwave irradiation. After 100 W of microwave was irradiated to the reaction mixture at 140°C for 6 h in the temperature control mode, corresponding polymer was obtained in 10% yield. In the case of conventional oil bath heating, by contrast, corresponding polymer was not obtained in similar anionic polymerization conditions. With 100 W and 2.45 GHz of microwave irradiation, formation of the polymer was obtained. Microwave‐assisted anionic hydrogen‐transfer copolymerization of NIPPAm and acrylamide (AAm) led to the formation of thermo‐sensitive copolymers whose thermo‐sensitivity was controlled by the NIPAAm/AAm unit ratio. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2415–2419 相似文献
975.
表面活性剂的分子结构对蠕虫胶束的形成与性质有着重要影响。本文以十四酸和间苯三酚为起始原料,合成了一种三聚阴离子表面活性剂(2, 2', 2"-(苯基-1, 3, 5-三(氧))-三-十四酸钠,简写为Ph-TrisC14Na),并通过稳态和动态流变测试,研究了单组分的Ph-TrisC14Na和Ph-TrisC14Na/阳离子添加剂体系的粘弹性质。阳离子添加剂分别为正丁基三甲基溴化铵(C4TAB),正己基三甲基溴化铵(C6TAB)和正辛基三甲基溴化铵(C8TAB)。结果表明,依赖于独特的分子构型,Ph-TrisC14Na分子自身即可形成蠕虫胶束,使溶液表现出明显的粘弹性。阳离子添加剂的加入可进一步优化Ph-TrisC14Na的分子几何结构,促进蠕虫胶束更为快速地生长。随着阳离子添加剂疏水链长的增加,溶液的粘弹性显著增强,体系微结构对添加剂的敏感性也增加。对于50 mmol·L-1的Ph-TrisC14Na溶液来说,在C8TAB与Ph-TrisC14Na的摩尔比为0.5时,体系的零剪切粘度可达1535 Pa·s,蠕虫胶束的长度则达到4.0-7.5 μm。该体系体现出低聚表面活性剂在构筑表面活性剂粘弹溶液方面的优势,可拓展高粘弹性阴离子蠕虫胶束体系的研究范围。 相似文献
976.
The influence of acid-base polar modifiers (σ-μ complex): amine-alkoxide, amine-ether-alkoxide, and ether-alkoxide complexes on microstructure of polybutadiene obtained by anionic polymerization was studied. The content of butadiene isomeric structures was determined based on FT-IR-ATR, 1H, and 13C NMR data analyses. The results obtained indicated a very similar influence of all types of polar modifiers forming σ-μ complex on polymer microstructure leading to high vinyl polybutadiene with nearly equal ratios of cis-1,4 and trans-1,4 butadiene isomeric structures. 相似文献
977.
Glass-forming composition regions of aqueous CH3COOM (M = Li, Na, K, Rb, Cs, and Tl), CF3COOM (M = Li, Na, K, Rb, and Cs), and Et4NX (Et4 = C2H5, X = OH, CH3COO, Cl, Br, NO3, and SCN) solutions are reported as a function of water concentration R (R = moles of water per moles of salt). Glass transition temperatures (T
g) were measured by a simple differential thermal analysis (DTA) method with a cooling rate of about 600 K-min–1. The T
g of all solutions decrease with increasing R (decreasing salt concentration). It is found that T
g at the same R value decrease in the order Na+ > Li+ > K+ > Rb+ > Cs+ in all glass-forming composition regions of the alkali acetate salt and alkali trifluoroacetate salt solutions. T
g for Et4NX solutions decrease in the order CH3COO– ~OH– > Cl– > Br– > NO
3
–
> SCN–. The effects of the cation and anion on the glass-forming behavior in these aqueous solutions are discussed. 相似文献
978.
SPAPT-CTMAB-AS显色反应的研究及应用 总被引:2,自引:0,他引:2
合成的新试剂1-(4-磺酸基苯基)-3-[4-(苯基偶氮)苯基]-三氮烯(SPAPT)与阳离子表面活性剂溴化十六烷基三甲铵(CTMAB)和阴离子表面活性剂(AS)在三乙醇胺调节的碱性(pH
11.00~11.20)介质中形成三元显色配合物。配合物最大吸收λ位于590 nm,测定阴离子表面活性剂十二烷基苯磺酸钠(DBOSO 相似文献
979.
Takahide Mizawa Katsuhiko Takenaka Tomoo Shiomi 《Journal of polymer science. Part A, Polymer chemistry》1999,37(17):3464-3472
In order to synthesize end-functionalized polymers with conjugated dienyl groups, living polymeric anions of polystyrene and polyisoprene were allowed to react with 5-bromo-1,3-pentadiene, 1, and 7-bromo-1,3-heptadiene, 2. The reaction of polystyryl anion and/or polyisoprenyl anion with 1 gave polymers whose end-functionalities were 65–80% regardless of the reaction conditions. On the other hand, almost quantitative functionalization was achieved when a large excess amount of 2 was used as a terminator. When 1,1-diphenylalkyl anion and enolate anion derived from t-butyl methacrylate were used, the degree of end-functionality were 70–80% at best. The resulting end-functionalized polymers were characterized by size exclusion chromatography (SEC), 1H and 13C-NMR and thin layer chromatography coupled with a flame ionization detector (TLC-FID). © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3464–3472, 1999 相似文献
980.
Although glyphosate (Gly) is one of the most widely used agrochemicals, it is also of the most difficult to measure. Gly, its metabolites, and related compounds cannot be sought within the scope of multi-residue methods. Specific so-called single-residue methods are used instead. Liquid chromatography-mass spectrometry (LC-MS) is currently the most widely used technique for determining Gly and its metabolites. This review addresses the different LC-MS-based methods proposed for the determination of Gly and related species in food and environment matrices. Sample preparation (food and environment), as well as their determination based in novel liquid chromatography/mass spectrometry approaches including different specific stationary phases are presented and the specific analytical challenges, strengths and drawbacks are critically discussed. 相似文献