全文获取类型
收费全文 | 3434篇 |
免费 | 211篇 |
国内免费 | 555篇 |
专业分类
化学 | 3661篇 |
晶体学 | 86篇 |
力学 | 15篇 |
综合类 | 49篇 |
数学 | 6篇 |
物理学 | 383篇 |
出版年
2024年 | 9篇 |
2023年 | 46篇 |
2022年 | 84篇 |
2021年 | 93篇 |
2020年 | 108篇 |
2019年 | 110篇 |
2018年 | 96篇 |
2017年 | 137篇 |
2016年 | 129篇 |
2015年 | 120篇 |
2014年 | 137篇 |
2013年 | 414篇 |
2012年 | 194篇 |
2011年 | 156篇 |
2010年 | 145篇 |
2009年 | 146篇 |
2008年 | 159篇 |
2007年 | 195篇 |
2006年 | 172篇 |
2005年 | 194篇 |
2004年 | 169篇 |
2003年 | 165篇 |
2002年 | 120篇 |
2001年 | 87篇 |
2000年 | 64篇 |
1999年 | 89篇 |
1998年 | 81篇 |
1997年 | 84篇 |
1996年 | 78篇 |
1995年 | 69篇 |
1994年 | 51篇 |
1993年 | 42篇 |
1992年 | 47篇 |
1991年 | 27篇 |
1990年 | 21篇 |
1989年 | 27篇 |
1988年 | 23篇 |
1987年 | 17篇 |
1986年 | 19篇 |
1985年 | 12篇 |
1984年 | 4篇 |
1982年 | 14篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1976年 | 7篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1973年 | 6篇 |
排序方式: 共有4200条查询结果,搜索用时 15 毫秒
21.
Tianeptine tablets are currently marketed to be designed for immediate-release tablets. The tianeptine has a short half-life, making it difficult to design for sustained-release tablets and achieve bioequivalence with the tianeptine immediate-release tablet (Stablon®). We established the in vitro–in vivo correlation (IVIVC) of three formulations of tianeptine sustained-release tablets according to their granule size. To evaluate sustained drug release, in vitro tests were performed in pH 1.2 media for 24 h. In vivo pharmacokinetic analysis was performed following oral administration of reference drug and test drug to beagle dogs. The dissolution profile revealed delayed release as the size of the granules increased. The dissolution results were confirmed in pharmacokinetic analysis, showing that the half-life was delayed as granule size increased. The final formulation and reference drug showed an equivalent area under the curve (AUC). Through this, IVIVC was established according to the size of the tianeptine sodium granules, which is the purpose of this study, and was used to predict in vivo pharmacokinetics from the formulation composition. This approach may be useful for determining optimal formulation compositions to achieve the desired pharmacokinetics when developing new formulations. 相似文献
22.
Ji-Myung Choi Huong Thu Vu Seong-Jin Shin Jun-Yong Ahn You-Jin Kim Sol Song Mi-Ran Han Jun-Haeng Lee Jong-Soo Kim Jonathan C. Knowles Hae-Hyoung Lee Ji-Sun Shin Jong-Bin Kim Jung-Hwan Lee 《Molecules (Basel, Switzerland)》2022,27(9)
Therapeutic iodoform (CHI3) is commonly used as a root-filling material for primary teeth; however, the side effects of iodoform-containing materials, including early root resorption, have been reported. To overcome this problem, a water-soluble iodide (NaI)-incorporated root-filling material was developed. Calcium hydroxide, silicone oil, and NaI were incorporated in different weight proportions (30:30:X), and the resulting material was denoted DX (D5~D30), indicating the NaI content. As a control, iodoform instead of NaI was incorporated at a ratio of 30:30:30, and the material was denoted I30. The physicochemical (flow, film thickness, radiopacity, viscosity, water absorption, solubility, and ion releases) and biological (cytotoxicity, TRAP, ARS, and analysis of osteoclastic markers) properties were determined. The amount of iodine, sodium, and calcium ion releases and the pH were higher in D30 than I30, and the highest level of unknown extracted molecules was detected in I30. In the cell viability test, all groups except 100% D30 showed no cytotoxicity. In the 50% nontoxic extract, D30 showed decreased osteoclast formation compared with I30. In summary, NaI-incorporated materials showed adequate physicochemical properties and low osteoclast formation compared to their iodoform-counterpart. Thus, NaI-incorporated materials may be used as a substitute for iodoform-counterparts in root-filling materials after further (pre)clinical investigation. 相似文献
23.
An VK-Z-Rohren zur Herstellung von Polyamid wurden Verweilzeitspektren mit der Methode der radioaktiven Markierung und der Methode der Indikatoraktivierungsanalyse gemessen. Die nach den beiden Methoden ermittelten Verweilzeitspektren werden miteinander verglichen. Die Übereinstimmung der Verweilzeitspektren wird durch Gegenüberstellung der statistischen Momente und durch einen Test nach Kolmogoroff-Smirnov geprüft. Es wird der experimentelle Aufwand beider Verfahren diskutiert und eine Fehlerabschätzung durchgeführt. 相似文献
24.
D. Missbach 《Isotopes in environmental and health studies》2013,49(5):195-202
An verschiedenen Systemen chemischer Verbindungen wurden Versuche zur Anreicherung des stabilen Isotopes 34S unter Verwendung der Ionenaustauscher Wofatit L 150, SBW und SBK nach den Methoden der Frontalchromatographie und der Bandenverdrāngungschromatographie ausgeführt. Beim Isotopenaustauschsystem Hydrogensulfit (am Ionenaustauscher)/Schwefeldioxid (in wäβriger Lösung) wurden Verfahrensweise und Betriebsparameter hinsichtlich des Anreicherungsgrades optimiert. Mit Hilfe einer einfachen Methode gelang es, aus den Versuchsergebnissen Werle für den elementaren Trennfaktor und die Trennstufenhöhe zu berechnen. 相似文献
25.
26.
A new and green method for the synthesis of α,β-unsaturated arylsulfones had been achieved through the condensation of aromatic aldehydes,chloroacetonitrile,benzenesulfinic acid sodium salt in the presence of l-butyl-3-methyl imidazolium hydroxide([bmim]OH) in EtOH under reflux.The ionic liquid was recovered and recycled for subsequent reactions.The advantages of this protocol were non-toxic,easy work-up and good yields. 相似文献
27.
张振辉 《南昌大学学报(理科版)》1988,12(4):1
本文研究了钒(V)在乙酸介质中催化溴酸钾氧化钙试剂羧酸钠盐的褪色反应。本方法的灵敏度为2.5×101?g/ml,与同类方法相比为最高,测定范围为0~4ngV/25ml。本法已用于水样中超痕量钒测定。 相似文献
28.
Well-crystallized hematite was suspended in water and treated at room-temperature (RT) with sodium borohydride. The product
of the reaction is a highly magnetic black powder, which is stable at RT. The NaBH4 treatment converts about half of the hematite to an amorphous Fe–B alloy and to a small fraction of sub-micron sized, amorphous
metallic-Fe nodules. Heating at 400°C of this composite has resulted in the crystallization and/or oxidation of more than
half of the amorphous Fe–B phase to α-Fe and Fe3O4 and B2O3, respectively. After treatment at 800°C, the metallic Fe and the amorphous Fe–B have completely vanished, and the resulting
product consists of hematite and FeBO3 embedded in the matrix of α-Fe2O3. 相似文献
29.
Theoretical predictions of solubility, typically accomplished by comparing the chemical potential of pure solid and solution, currently suffer from a lack of accuracy. We suggest an alternative method for predicting solubility based on molecular dynamics simulations of the behaviour of a small seed crystalline cluster probe in solutions of varying concentrations. The size dynamics of a properly chosen seed cluster that dissolves in unsaturated solutions and grows in size in supersaturated solutions is indicative of the saturation point. This approach is illustrated by its application to NaCl in water. 相似文献
30.
Experimental results on changes in conductivity of N2+ and Ar+ bombarded thin copper, aluminium and bismuth films are given along with the preliminary observations on photoconductivity of N2+ bombarded Bi2O3 thin films. The performance of a low cost, medium resolution 200 keV ion implantation system, used in the above experiments is also discussed. 相似文献