全文获取类型
收费全文 | 2453篇 |
免费 | 131篇 |
国内免费 | 10篇 |
专业分类
化学 | 1916篇 |
晶体学 | 10篇 |
力学 | 51篇 |
数学 | 279篇 |
物理学 | 338篇 |
出版年
2023年 | 40篇 |
2022年 | 41篇 |
2021年 | 62篇 |
2020年 | 106篇 |
2019年 | 88篇 |
2018年 | 59篇 |
2017年 | 37篇 |
2016年 | 93篇 |
2015年 | 64篇 |
2014年 | 75篇 |
2013年 | 116篇 |
2012年 | 203篇 |
2011年 | 270篇 |
2010年 | 96篇 |
2009年 | 79篇 |
2008年 | 159篇 |
2007年 | 145篇 |
2006年 | 153篇 |
2005年 | 97篇 |
2004年 | 94篇 |
2003年 | 78篇 |
2002年 | 54篇 |
2001年 | 16篇 |
2000年 | 26篇 |
1999年 | 10篇 |
1998年 | 17篇 |
1996年 | 18篇 |
1995年 | 7篇 |
1994年 | 9篇 |
1993年 | 22篇 |
1992年 | 17篇 |
1991年 | 14篇 |
1990年 | 15篇 |
1989年 | 13篇 |
1988年 | 14篇 |
1987年 | 14篇 |
1986年 | 16篇 |
1985年 | 16篇 |
1984年 | 15篇 |
1983年 | 10篇 |
1982年 | 11篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1979年 | 7篇 |
1976年 | 7篇 |
1975年 | 9篇 |
1973年 | 10篇 |
1968年 | 7篇 |
1967年 | 6篇 |
1966年 | 6篇 |
排序方式: 共有2594条查询结果,搜索用时 15 毫秒
911.
Composite Polymer/Oxide Hollow Fiber Contactors: Versatile and Scalable Flow Reactors for Heterogeneous Catalytic Reactions in Organic Synthesis
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. Eric G. Moschetta Dr. Solymar Negretti Kathryn M. Chepiga Dr. Nicholas A. Brunelli Dr. Ying Labreche Dr. Yan Feng Dr. Fateme Rezaei Prof. Ryan P. Lively Prof. William J. Koros Prof. Huw M. L. Davies Prof. Christopher W. Jones 《Angewandte Chemie (International ed. in English)》2015,54(22):6470-6474
Flexible composite polymer/oxide hollow fibers are used as flow reactors for heterogeneously catalyzed reactions in organic synthesis. The fiber synthesis allows for a variety of supported catalysts to be embedded in the walls of the fibers, thus leading to a diverse set of reactions that can be catalyzed in flow. Additionally, the fiber synthesis is scalable (e.g. several reactor beds containing many fibers in a module may be used) and thus they could potentially be used for the large‐scale production of organic compounds. Incorporating heterogeneous catalysts in the walls of the fibers presents an alternative to a traditional packed‐bed reactor and avoids large pressure drops, which is a crucial challenge when employing microreactors. 相似文献
912.
Synthesis of a Neutral Mixed‐Valence Diferrocenyl Carborane for Molecular Quantum‐Dot Cellular Automata Applications
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)
John A. Christie Ryan P. Forrest Dr. Steven A. Corcelli Dr. Natalie A. Wasio Dr. Rebecca C. Quardokus Dr. Ryan Brown Dr. S. Alex Kandel Dr. Yuhui Lu Dr. Craig S. Lent Dr. Kenneth W. Henderson 《Angewandte Chemie (International ed. in English)》2015,54(51):15448-15451
The preparation of 7‐Fc+‐8‐Fc‐7,8‐nido‐[C2B9H10]? (Fc+FcC2B9?) demonstrates the successful incorporation of a carborane cage as an internal counteranion bridging between ferrocene and ferrocenium units. This neutral mixed‐valence FeII/FeIII complex overcomes the proximal electronic bias imposed by external counterions, a practical limitation in the use of molecular switches. A combination of UV/Vis‐NIR spectroscopic and TD‐DFT computational studies indicate that electron transfer within Fc+FcC2B9? is achieved through a bridge‐mediated mechanism. This electronic framework therefore provides the possibility of an all‐neutral null state, a key requirement for the implementation of quantum‐dot cellular automata (QCA) molecular computing. The adhesion, ordering, and characterization of Fc+FcC2B9? on Au(111) has been observed by scanning tunneling microscopy. 相似文献
913.
John T. Petroff II Scott Grady Christopher K. Arnatt Ryan D. McCulla 《Photochemistry and photobiology》2020,96(1):67-73
Dibenzothiophene 5,5-dioxide (DBTOO) derivatives have recently been shown to processes utility as fluorescent cell dyes. In an effort to extend the functionality of DBTOO-based dyes to include the visualization of cellular membranes, two lipophilic DBTOO were synthesized and their ability to incorporate into the plasma membrane of HeLa cells was examined by fluorescent microscopy. The photophysical properties of the two new DBTOO derivatives were determined and both have good fluorescent quantum yields and a visible blue emission. Due to agreeable wavelengths of excitation and emission, a standard 4′,6-diamindino-2-phenylindole (DAPI) filter set worked well with these dyes. After co-staining, it was confirmed that both DBTOO dyes localized in the plasma membrane. The quality of the overlap was quantified using Pearson correlation coefficient, which indicated a strong overlap between the DBTOO dyes and the standard plasma membrane dye. The novel dyes also displayed relatively low toxicity to the HeLa cells with IC50 between 10 and 100 µm . Thus, this work reports a new use of DBTOO derivatives as fluorescent microscopy stains. 相似文献
914.
Qiyao Li Dr. Ying Li Tianliang Min Junyi Gong Dr. Lili Du Prof. David Lee Phillips Junkai Liu Dr. Jacky W. Y. Lam Dr. Herman H. Y. Sung Prof. Ian D. Williams Dr. Ryan T. K. Kwok Prof. Chun Loong Ho Prof. Kai Li Prof. Jianguo Wang Prof. Ben Zhong Tang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(24):9557-9564
Pathogen infections and cancer are two major human health problems. Herein, we report the synthesis of an organic salt photosensitizer (PS), called 4TPA-BQ, by a one-step reaction. 4TPA-BQ presents aggregation-induced emission features. Owing to the aggregation-induced reactive oxygen species generated and a sufficiently small ΔEST, 4TPA-BQ shows a satisfactorily high 1O2 generation efficiency of 97.8 %. In vitro and in vivo experiments confirmed that 4TPA-BQ exhibited potent photodynamic antibacterial performance against ampicillin-resistant Escherichia coli with good biocompatibility in a short time (15 minutes). When the incubation duration persisted long enough (12 hours), cancer cells were ablated efficiently, leaving normal cells essentially unaffected. This is the first reported time-dependent fluorescence-guided photodynamic therapy in one individual PS, which achieves ordered and multiple targeting simply by varying the external conditions. 4TPA-BQ reveals new design principles for the implementation of efficient PSs in clinical applications. 相似文献
915.
Dr. Menghua Wang Dr. Haruka Niikura Dr. Hai-Yan He Phillip Daniel-Ivad Prof. Dr. Katherine S. Ryan 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(10):3909-3913
The formation of a N−N bond is a unique biochemical transformation, and nature employs diverse biosynthetic strategies to activate nitrogen for bond formation. Among molecules that contain a N−N bond, biosynthetic routes to diazeniumdiolates remain enigmatic. We here report the biosynthetic pathway for the diazeniumdiolate-containing amino acid l -alanosine. Our work reveals that the two nitrogen atoms in the diazeniumdiolate of l -alanosine arise from glutamic acid and aspartic acid, and we clarify the early steps of the biosynthetic pathway by using both in vitro and in vivo approaches. Our work demonstrates a peptidyl-carrier-protein-based mechanism for activation of the precursor l -diaminopropionate, and we also show that nitric oxide can participate in non-enzymatic diazeniumdiolate formation. Furthermore, we demonstrate that the gene alnA, which encodes a fusion protein with an N-terminal cupin domain and a C-terminal AraC-like DNA-binding domain, is required for alanosine biosynthesis. 相似文献
916.
917.
Andrew J. Onstad Christopher J. Elkins Frank Medina Ryan B. Wicker John K. Eaton 《Experiments in fluids》2011,50(6):1571-1585
Open-celled foam geometries show great promise in heat/mass transfer, chemical treatment, and enhanced mixing applications.
Flow measurements on these geometries have consisted primarily of observations of the upstream and downstream effects the
foam has on the velocity field. Unfortunately, these observations give little insight into the flow inside the foam. We have
performed quantitative flow measurements inside a scaled replica of a metal foam, ϕ = 0.921, D
Cell = 2.5 mm, by Magnetic Resonance Velocimetry to better understand the fluid motion inside the foam and give an alternative
method to determine the foam cell and pore sizes. Through these 3-D, spatially resolved measurements of the flow field for
a cell Reynolds number of 840, we have shown that the transverse motion of the fluid has velocities 20–30% of the superficial
velocity passing through the foam. This strong transverse motion creates and dissipates streamwise jets with peak velocities
2–3 times the superficial velocity and whose coherence length is strongly correlated to the cell size of the foam. This complex
fluid motion is described as “mechanical mixing” and is attributed to the geometry of the foam. A mechanical dispersion coefficient,
D
M, was formed which demonstrates the transverse dispersion of this geometry to be 14 times the kinematic viscosity and 10 times
the thermal diffusivity of air at 20°C and 1 atm. 相似文献
918.
919.
A dendrimer-based building block for theranostics was designed. The multifunctional dendrimer is polyamide-based and contains nine azide termini, nine amine termini, and fifty-four terminal acid groups. Orthogonal functionalization of the multifunctional dendrimer with a near-infrared (NIR) cyanine dye afforded the final dendrimer that shows fluorescence in the NIR region and no toxicity toward T98G human cells. The synthetic strategy described here might be promising for fabricating the next generation of materials for theranostics. 相似文献
920.
Bonaparte AC Betush MP Panseri BM Mastarone DJ Murphy RK Murphree SS 《Organic letters》2011,13(6):1447-1449
Primary alkyl aryl sulfones are converted to the corresponding carboxylic acids in fair to excellent yield through double deprotonation and exposure to atmospheric oxygen. The methodology allows for the convenient synthesis of (13)C labeled carboxylic acids. 相似文献