全文获取类型
收费全文 | 88275篇 |
免费 | 24656篇 |
国内免费 | 4112篇 |
专业分类
化学 | 96745篇 |
晶体学 | 701篇 |
力学 | 3318篇 |
综合类 | 205篇 |
数学 | 6794篇 |
物理学 | 9280篇 |
出版年
2024年 | 190篇 |
2023年 | 4252篇 |
2022年 | 2024篇 |
2021年 | 3217篇 |
2020年 | 6378篇 |
2019年 | 5452篇 |
2018年 | 3120篇 |
2017年 | 1805篇 |
2016年 | 8011篇 |
2015年 | 8171篇 |
2014年 | 7858篇 |
2013年 | 8831篇 |
2012年 | 6647篇 |
2011年 | 4470篇 |
2010年 | 6360篇 |
2009年 | 6226篇 |
2008年 | 4333篇 |
2007年 | 3291篇 |
2006年 | 2512篇 |
2005年 | 2511篇 |
2004年 | 2151篇 |
2003年 | 1885篇 |
2002年 | 2603篇 |
2001年 | 1819篇 |
2000年 | 1616篇 |
1999年 | 736篇 |
1998年 | 322篇 |
1997年 | 289篇 |
1996年 | 288篇 |
1995年 | 325篇 |
1994年 | 237篇 |
1993年 | 330篇 |
1992年 | 201篇 |
1991年 | 189篇 |
1989年 | 158篇 |
1988年 | 158篇 |
1981年 | 170篇 |
1980年 | 201篇 |
1979年 | 191篇 |
1978年 | 196篇 |
1977年 | 315篇 |
1976年 | 368篇 |
1975年 | 460篇 |
1974年 | 473篇 |
1973年 | 287篇 |
1972年 | 369篇 |
1971年 | 356篇 |
1970年 | 542篇 |
1969年 | 414篇 |
1968年 | 456篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
Simultaneous quantitative determination of 20 active components in the traditional Chinese medicine formula Zhi‐Zi‐Da‐Huang decoction by liquid chromatography coupled with mass spectrometry: application to study the chemical composition variations in different combinations 下载免费PDF全文
Zheng Tang Ran Yin Kaishun Bi Heyun Zhu Fei Han Kelin Chen Fenrong Wang 《Biomedical chromatography : BMC》2015,29(9):1406-1414
92.
Marius Lupu Adnana Zaulet Prof. Dr. Francesc Teixidor Prof. Dr. Eliseo Ruiz Prof. Dr. Clara Viñas 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(18):6888-6897
The metallacarborane [3,3′‐Co(1,2‐closo‐C2B9H11)2]? has been synthesized. This species allows the formation of redox couples in which both partners are negatively charged. The E1/2 potential can be tuned by adjusting the nature and number of substituents on B and C. The octaiodinated species [3,3′‐Co(1,2‐closo‐C2B9H7I4)2]? is the most favorable, as it is isolatable and stable in air. A DFT study on stability and redox potentials of complexes has been performed. 相似文献
93.
Hui Li Jian Liu Juan Zhao Huiting He Dr. Dabo Jiang Prof. Steven Robert Kirk Prof. Qiong Xu Dr. Xianxiang Liu Prof. Dulin Yin 《ChemistryOpen》2021,10(4):477-485
A series of tetraimidazolium salts with different anions was prepared and applied in the isomerization of β-pinene oxide. After examining the activity of different catalysts, a remarkable enhancement of the selectivity of perillyl alcohol (47 %) was obtained over [PEimi][HNO3]4 under mild reaction conditions and using DMSO as the solvent. Furthermore, noncovalent interactions between solvent molecules and the catalyst were found by FT-IR spectroscopy and confirmed by computational chemistry. The homogeneous catalyst showed excellent stability and was reused up to six times without significant loss. 相似文献
94.
在管式反应器中采用苯甲酸、聚乙二醇、固体古马隆树脂(S)、液体古马隆树脂(L)为添加剂来降低煤沥青中有害物质苯并芘的含量,以期使得煤沥青可绿色化应用。采用紫外-可见分光光度计分析煤沥青中苯并芘含量。考察了反应温度、反应时间、添加剂添加量、催化剂等工艺条件对添加剂脱除煤沥青中苯并芘的影响。结果表明,不同工艺条件能降低煤沥青中苯并芘的含量。在优化条件下,不同添加剂对苯并芘脱除率由高到低依次为:液体古马隆树脂、聚乙二醇、苯甲酸和固体古马隆树脂。分析其反应机理,这与催化剂的酸性相关,发生亲电取代反应。结果表明,液体古马隆树脂(L)在催化剂存在下对煤沥青中苯并芘脱除率可达73.0%,显示了良好的应用前景。 相似文献
95.
96.
Sergio Ayala‐Mar Javier Donoso‐Quezada Roberto C. Gallo‐Villanueva Victor H. Perez‐Gonzalez Jos Gonzlez‐Valdez 《Electrophoresis》2019,40(23-24):3036-3049
Exosomes are nanovesicles secreted by most cellular types that carry important biochemical compounds throughout the body with different purposes, playing a preponderant role in cellular communication. Because of their structure, physicochemical properties and stability, recent studies are focusing in their use as nanocarriers for different therapeutic compounds for the treatment of different diseases ranging from cancer to Parkinson's disease. However, current bioseparation protocols and methodologies are selected based on the final exosome application or intended use and present both advantages and disadvantages when compared among them. In this context, this review aims to present the most important technologies available for exosome isolation while discussing their advantages and disadvantages and the possibilities of being combined with other strategies. This is critical since the development of novel exosome‐based therapeutic strategies will be constrained to the effectiveness and yield of the selected downstream purification methodologies for which a thorough understanding of the available technological resources is needed. 相似文献
97.
Particularly-shaped silver nanostructures are successfully applied in many scientific fields, such as nanotechnology, catalysis, (nano)engineering, optoelectronics, and sensing. In recent years, the production of shape-controlled silver-based nanostructures and the knowledge around this topic has grown significantly. Hence, on the basis of the most recent results reported in the literature, a critical analysis around the driving forces behind the synthesis of such nanostructures are proposed herein, pointing out the important role of surface-regulating agents in driving crystalline growth by favoring (or opposing) development along specific directions. Additionally, growth mechanisms of the different morphologies considered here are discussed in depth, and critical points highlighted. 相似文献
98.
Back Cover: Reactions of Group 4 Metallocenes with Monosubstituted Acetonitriles: Keteniminate Formation versus CC Coupling (Chem. Eur. J. 8/2015) 下载免费PDF全文
99.
100.
Triazines are widely used in agriculture around the world as selective pre‐ and post‐emergence herbicides for the control of broad leaf and grassy weeds. With high toxicity and persistence, triazines can contaminate the environment and crops, so the development of rapid and sensitive methods for the determination of different triazines is necessary. Capillary electrophoresis comprises a group of techniques used to separate chemical mixtures. Analytical separation is based on different electrophoretic mobilities. This review focuses on the analysis of triazine herbicides with different modes of capillary electrophoresis, including capillary zone electrophoresis, micellar electrokinetic capillary electrophoresis, capillary electrochromatography and nonaqueous capillary electrophoresis. Determinations of triazines in various matrices such as surface water, groundwater, vegetables, soil and grains are emphasized. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献