全文获取类型
收费全文 | 1478篇 |
免费 | 25篇 |
国内免费 | 4篇 |
专业分类
化学 | 1153篇 |
晶体学 | 9篇 |
力学 | 6篇 |
数学 | 53篇 |
物理学 | 286篇 |
出版年
2022年 | 18篇 |
2021年 | 19篇 |
2020年 | 15篇 |
2019年 | 20篇 |
2018年 | 17篇 |
2017年 | 13篇 |
2016年 | 18篇 |
2015年 | 16篇 |
2014年 | 16篇 |
2013年 | 54篇 |
2012年 | 53篇 |
2011年 | 74篇 |
2010年 | 45篇 |
2009年 | 40篇 |
2008年 | 84篇 |
2007年 | 85篇 |
2006年 | 70篇 |
2005年 | 75篇 |
2004年 | 79篇 |
2003年 | 48篇 |
2002年 | 50篇 |
2001年 | 24篇 |
2000年 | 31篇 |
1999年 | 23篇 |
1998年 | 19篇 |
1997年 | 24篇 |
1996年 | 12篇 |
1995年 | 12篇 |
1994年 | 18篇 |
1993年 | 22篇 |
1992年 | 26篇 |
1991年 | 26篇 |
1990年 | 30篇 |
1989年 | 29篇 |
1988年 | 26篇 |
1987年 | 17篇 |
1986年 | 15篇 |
1985年 | 27篇 |
1984年 | 24篇 |
1983年 | 14篇 |
1982年 | 22篇 |
1981年 | 16篇 |
1980年 | 9篇 |
1979年 | 24篇 |
1978年 | 13篇 |
1977年 | 15篇 |
1976年 | 18篇 |
1975年 | 14篇 |
1973年 | 6篇 |
1968年 | 6篇 |
排序方式: 共有1507条查询结果,搜索用时 15 毫秒
991.
The adsorption of phosphate from an aquatic environment using metal-loaded orange waste 总被引:5,自引:0,他引:5
Biswas BK Inoue K Ghimire KN Ohta S Harada H Ohto K Kawakita H 《Journal of colloid and interface science》2007,312(2):214-223
Phosphate removal from an aquatic environment was investigated using La(III)-, Ce(III)- and Fe(III)-loaded orange waste. The adsorption isotherm, the kinetics of adsorption and the effect of pH on the removal of phosphate have been examined. The % removal of phosphate using La(III)- and Ce(III)-loaded orange waste gel increases with increasing pH within the range of 5-7 but decreases when the pH is increased beyond this range. The equilibrium sorption was observed to be in accordance with Langmuir type adsorption and the maximum adsorption capacity was evaluated as 13.94 mg P/g of dry gel for all the three types of gels. Kinetic studies revealed that 15 h is enough to reach equilibrium in batch experiments. Fixed bed sorption experiments confirmed the continuous phosphate adsorption and elution capability of such simply modified gels. Due to their low cost, availability and significantly high adsorption capability, metal-loaded SOW gels can be effectively employed for the removal of phosphate from water. 相似文献
992.
Kamimura A Okawa H Morisaki Y Ishikawa S Uno H 《The Journal of organic chemistry》2007,72(9):3569-3572
Optically active N-sulfinimines underwent stereoselective Michael/nucleophilic addition domino reaction triggered by magnesium thiolate to give alpha-phenylthiomethyl-beta-(N-sulfinylamino) esters in high diastereomeric excess. The adducts were readily converted into optically active alpha-methylene-beta-(N-sulfinylamino)esters so that this reaction provides a useful asymmetric aza-Baylis-Hillman-equivalent method. 相似文献
993.
Saito S Suzuki R Danzaka N Hikichi A Yoshimoto K Maeda M Aoyama M 《Electrophoresis》2007,28(14):2448-2457
The low sensitivity of simple CZE for detecting metal ions is a long-standing problem even when an LIF detection system is employed. We have successfully achieved an ultrasensitive CE-LIF using a simple CZE mode (typical detection limit: 10(-11)-10(-10) mol/dm(3)). Both the design of a newly synthesized ligand and the combination of a precapillary derivatizing technique with an on-capillary ternary complexing technique have enabled us to achieve this extremely low LOD and high resolution of large metal complexes. The direct fluorescent detection of the paramagnetic metal ions was achieved for the first time despite their intrinsic fluorescent quenching nature. The fluorescent ligand (L) consists of a polyaminocarboxylate chelating moiety, a strongly emissive fluorescein moiety and a spacer connecting the two portions. The migration behavior of various metal-L complexes was investigated. The resolution among the complexes was improved by the introduction of a ternary complex equilibrium of the kinetically stable mother complexes with OH(-) ion. The analytical potential of our simple system was examined, and it was proved that the system was one of the most sensitive methods without the need for any preconcentration process. 相似文献
994.
Our purpose is to design a high heat flux micro-evaporator that can remove more than 100 W/cm2. For this purpose a thin liquid film is evaporized. The liquid film is stabilized in micro-channels by capillary forces. The micro-channels are fabricated by chemical etching on silicon to reduce thermal resistance. For the experiments, the channel plate is heated by an ITO thin film heater deposited on the opposite side of the channel plate. Influence of heat flux, coolant flow rate, and inlet temperature on the temperature of the heater element are investigated. Water is used as working fluid. A maximal heat flux of 125 W/cm2 could be achieved for water inlet temperature of 90 °C and flow rate of 1.0 mL/min. The temperature of the heater element is kept constant at about 120 °C with fluctuations within 8 °C. The measured pressure drop is less than 1000 Pa. 相似文献
995.
Shingo Ishikawa Reuben Hudson Mitra Masnadi Mary Bateman Annie Castonguay Nadi Braidy Audrey Moores Chao-Jun Li 《Tetrahedron》2014
Simple bare copper-plated iron nanoparticles catalyzed the cyclopropanation of diazoesters with styrene derivatives. The reaction proceeded smoothly and provided the desired products in moderate to good yields, with selectivity for the trans isomer in neat conditions. The reaction scope was explored and di or tri-substituted cyclopropanes were synthesized. The catalysts could be magnetically separated and reusable up to five times. It was also characterized by TEM, XPS, and ICP-MS. A gram-scale reaction was performed with a yield of 72%. 相似文献
996.
Calcium ion (Ca2+) is one of the most important second messengers. However, conventional Ca2+ indicators cannot be applied in plant cells. In previous paper, we developed the first-generation protein-ligand tethered calcium indicator that can be applied for living plant cells.Here, we will report the development of second-generation indicator based on the detailed examination on physical properties of the first-generation to improve the drawbacks. Through the examination, we also found that cell permeability of the probe is strongly affected by their aggregation properties. Our findings will provide new strategy for the design of synthetic indicators. 相似文献
997.
Reactions of Difunctional Electrophiles with Functionalized Aryllithium Compounds: Remarkable Chemoselectivity by Flash Chemistry
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)
Dr. Aiichiro Nagaki Keita Imai Satoshi Ishiuchi Prof. Jun‐ichi Yoshida 《Angewandte Chemie (International ed. in English)》2015,54(6):1914-1918
Flash chemistry using flow microreactors enables highly chemoselective reactions of difunctional electrophiles with functionalized aryllithium compounds by virtue of extremely fast micromixing. The approach serves as a powerful method for protecting‐group‐free synthesis using organolithium compounds and opens a new possibility in the synthesis of polyfunctional organic molecules. 相似文献
998.
T. Inoue S. Ando T. Aoki H. Arikawa S. Ezure K. Harada T. Hayamizu T. Ishikawa M. Itoh K. Kato H. Kawamura A. Uchiyama T. Aoki K. Asahi T. Furukawa A. Hatakeyama K. Hatanaka K. Imai T. Murakami H. S. Nataraj T. Sato Y. Shimizu T. Wakasa H. P. Yoshida A. Yoshimi Y. Sakemi 《Hyperfine Interactions》2015,231(1-3):157-162
999.
Tomofumi Santa Osama Y. Al‐Dirbashi Takashi Yoshikado Takeshi Fukushima Kazuhiro Imai 《Biomedical chromatography : BMC》2009,23(4):443-446
Benzofurazan derivatization reagents, 4‐[2‐(N,N‐dimethylamino)ethylaminosulfonyl]‐7‐(2‐aminopentylamino)‐2,1,3‐benzoxadiazole (DAABD‐AP) and 4‐[2‐(N,N‐dimethylamino) ethylaminosulfonyl]‐7‐(2‐aminobutylamino)‐2,1,3‐benzoxadiazole (DAABD‐AB), for short‐chain carboxylic acids in liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI‐MS/MS) were synthesized. These reagents reacted with short chain carboxylic acids in the presence of the condensation reagents at 60°C for 60 min. The generated derivatives were separated on the reversed‐phase column and detected by ESI‐MS/MS with the detection limits of 0.1–0.12 pmol on column. Upon collision‐induced dissociation, a single and intense product ion at m/z 151 was observed. These results indicated that DAABD‐AP and DAABD‐AB are suitable as the derivatization reagents in LC/ESI‐MS/MS analysis. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
1000.
Formation of atomically smooth SiO2/SiC interfaces at ∼120 °C by use of nitric acid oxidation method
Conventional thermal oxidation of SiC requires heating at ∼1100 °C. In the present study, we have developed a method of oxidizing SiC at low temperatures (i.e., ∼120 °C) to form relatively thick silicon dioxide (SiO2) layers by use of nitric acid. When 4H-SiC(0 0 0 1) wafers are immersed in 40 wt% HNO3 at the boiling temperature of 108 °C and the boiling is kept for 5 h after reaching the azeotropic point (i.e., 68 wt% HNO3 at 121 °C), 8.1 nm thick SiO2 layers are formed on the SiC substrates. High resolution transmission electron microscopy measurements show that the SiO2/SiC interface is atomically flat and the SiO2 layer is uniform without bunching. When SiC is immersed in an azeotropic mixture of HNO3 with water from the first, the SiO2 thickness is less than 0.3 nm. The metal-oxide-semiconductor (MOS) diodes with the SiO2 layer formed by the nitric acid oxidation method possess a considerably low leakage current density. 相似文献