全文获取类型
收费全文 | 3081篇 |
免费 | 106篇 |
国内免费 | 19篇 |
专业分类
化学 | 2428篇 |
晶体学 | 32篇 |
力学 | 44篇 |
数学 | 305篇 |
物理学 | 397篇 |
出版年
2023年 | 17篇 |
2022年 | 24篇 |
2021年 | 47篇 |
2020年 | 71篇 |
2019年 | 69篇 |
2018年 | 45篇 |
2017年 | 34篇 |
2016年 | 75篇 |
2015年 | 71篇 |
2014年 | 85篇 |
2013年 | 119篇 |
2012年 | 260篇 |
2011年 | 318篇 |
2010年 | 127篇 |
2009年 | 106篇 |
2008年 | 236篇 |
2007年 | 260篇 |
2006年 | 225篇 |
2005年 | 234篇 |
2004年 | 205篇 |
2003年 | 163篇 |
2002年 | 166篇 |
2001年 | 40篇 |
2000年 | 35篇 |
1999年 | 17篇 |
1998年 | 19篇 |
1997年 | 17篇 |
1996年 | 25篇 |
1995年 | 8篇 |
1994年 | 9篇 |
1993年 | 11篇 |
1992年 | 7篇 |
1991年 | 4篇 |
1989年 | 5篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 7篇 |
1972年 | 2篇 |
1971年 | 2篇 |
排序方式: 共有3206条查询结果,搜索用时 281 毫秒
991.
C.-Y. YenS.-R. Jian G.-J. ChenC.-M. Lin H.-Y. LeeW.-C. Ke Y.-Y. LiaoP.-F. Yang C.-T. WangY.-S. Lai Jason S.-C. JangJ.-Y. Juang 《Applied Surface Science》2011,257(17):7900-7905
ZnO thin films grown on Si(1 1 1) substrates by using atomic layer deposition (ALD) were annealed at the temperatures ranging from 300 to 500 °C. The X-ray diffraction (XRD) results show that the annealed ZnO thin films are highly (0 0 2)-oriented, indicating a well ordered microstructure. The film surface examined by the atomic force microscopy (AFM), however, indicated that the roughness increases with increasing annealing temperature. The photoluminescence (PL) spectrum showed that the intensity of UV emission was strongest for films annealed at 500 °C. The mechanical properties of the resultant ZnO thin films investigated by nanoindentation reveal that the hardness decreases from 9.2 GPa to 7.2 GPa for films annealed at 300 °C and 500 °C, respectively. On the other hand, the Young's modulus for the former is 168.6 GPa as compared to a value of 139.5 GPa for the latter. Moreover, the relationship between the hardness and film grain size appear to follow closely with the Hall-Petch equation. 相似文献
992.
It is well established that nanosized surface topography significantly affects cell response at a biomaterial surface. Here we used a through-mask anodization technique to fabricate well-defined titania nanopillars with tunable feature sizes from 15 to 100 nm on bulk titanium (Ti) substrates and studied their effects on initial attachment and spreading of osteoblast-like cells (MG63). An increase of titania pillar height from 15 to 100 nm resulted in reduced spreading of MG63 osteoblast-like cells and the higher pillar structures also gave rise to heavily elongated cells. By using a FIB/SEM dual beam microscope the interface between MG63 cells and nanopatterned Ti surfaces could be studied in more detail. It was found that the higher pillar structures prevented the cells to conform to the surface topography leaving voids in between the cells and the substrates. The results found in this study agree with previous studies that cells response better to surfaces with smaller (<20 nm) features. 相似文献
993.
Jeishla L. M. Matos Samantha A. Green Yuge Chun Vuong Q. Dang Russell G. Dushin Paul Richardson Jason S. Chen David W. Piotrowski Brian M. Paegel Ryan A. Shenvi 《Angewandte Chemie (International ed. in English)》2020,59(31):12998-13003
Preparative reactions that occur efficiently under dilute, buffered, aqueous conditions in the presence of biomolecules find application in ligation, peptide synthesis, and polynucleotide synthesis and sequencing. However, the identification of functional groups or reagents that are mutually reactive with one another, but unreactive with biopolymers and water, is challenging. Shown here are cobalt catalysts that react with alkenes under dilute, aqueous, buffered conditions and promote efficient cycloisomerization and formal Friedel–Crafts reactions. The constraining conditions of bioorthogonal chemistry are beneficial for reaction efficiency as superior conversion at low catalyst concentration is obtained and competent rates in dilute conditions are maintained. Efficiency at high dilution in the presence of buffer and nucleobases suggests that these reaction conditions may find broad application. 相似文献
994.
Benny Febriansyah Tetiana Borzda Daniele Cortecchia Stefanie Neutzner Giulia Folpini Teck Ming Koh Yongxin Li Nripan Mathews Annamaria Petrozza Jason England 《Angewandte Chemie (International ed. in English)》2020,59(27):10791-10796
Published studies of layered (2D) (100)‐oriented hybrid lead‐bromide perovskites evidence a correlation between increased inter‐octahedral (Pb‐Br‐Pb) distortions and the appearance of broadband white light emission. However, the impact of distortions within their constituent [PbBr6]4? octahedra has yet to be assessed. Herein, we report two new (100)‐oriented 2D Pb‐Br perovskites, whose structures display unusually high intra‐octahedral distortions, whilst retaining minimal inter‐octahedral distortions. Using a combination of temperature‐dependent, power‐dependent and time‐resolved photoluminescence spectroscopic measurements, we show that increased intra‐octahedral distortion induces exciton localization processes and leads to formation of multiple photoinduced emissive colour centres. Ultimately, this leads to highly Stokes‐shifted, ultrabroad white light emission at room temperature. 相似文献
995.
Jindou Yang Mi Sook Seo Kyung Ha Kim Yong‐Min Lee Shunichi Fukuzumi Jason Shearer Wonwoo Nam 《Angewandte Chemie (International ed. in English)》2020,59(32):13581-13585
A mononuclear nonheme cobalt(III) iodosylbenzene complex, [CoIII(TQA)(OIPh)(OH)]2+ ( 1 ), is synthesized and characterized structurally and spectroscopically. While 1 is a sluggish oxidant in oxidation reactions, it becomes a competent oxidant in oxygen atom transfer reactions, such as olefin epoxidation, in the presence of a small amount of proton. More interestingly, 1 shows a nucleophilic reactivity in aldehyde deformylation reaction, demonstrating that 1 has an amphoteric reactivity. Another interesting observation is that 1 can be used as an oxygen atom donor in the generation of high‐valent metal‐oxo complexes. To our knowledge, we present the first crystal structure of a CoIII iodosylbenzene complex and the unprecedented reactivity of metal‐iodosylarene adduct. 相似文献
996.
Crystallization of DNA‐Capped Gold Nanoparticles in High‐Concentration,Divalent Salt Environments 下载免费PDF全文
Dr. Shawn J. Tan Jason S. Kahn Thomas L. Derrien Dr. Michael J. Campolongo Mervin Zhao Dr. Detlef‐M. Smilgies Prof. Dan Luo 《Angewandte Chemie (International ed. in English)》2014,53(5):1316-1319
The multiparametric nature of nanoparticle self‐assembly makes it challenging to circumvent the instabilities that lead to aggregation and achieve crystallization under extreme conditions. By using non‐base‐pairing DNA as a model ligand instead of the typical base‐pairing design for programmability, long‐range 2D DNA–gold nanoparticle crystals can be obtained at extremely high salt concentrations and in a divalent salt environment. The interparticle spacings in these 2D nanoparticle crystals can be engineered and further tuned based on an empirical model incorporating the parameters of ligand length and ionic strength. 相似文献
997.
Remarkable Enhancement of Enantioselectivity in the Asymmetric Conjugate Addition of Dimethylzinc to (Z)‐Nitroalkenes with a Catalytic [(MeCN)4Cu]PF6–Hoveyda Ligand Complex 下载免费PDF全文
Dr. Xingzhong Zeng Joe J. Gao Dr. Jinhua J. Song Dr. Shengli Ma Dr. Jean‐Nicolas Desrosiers Dr. Jason A. Mulder Dr. Sonia Rodriguez Dr. Melissa A. Herbage Dr. Nizar Haddad Dr. Bo Qu Dr. Keith R. Fandrick Dr. Nelu Grinberg Dr. Heewon Lee Dr. Xudong Wei Dr. Nathan K. Yee Dr. Chris H. Senanayake 《Angewandte Chemie (International ed. in English)》2014,53(45):12153-12157
An enantioselective copper‐catalyzed asymmetric conjugate addition of Me2Zn to (Z)‐nitroalkenes led to the formation of all‐carbon quaternary stereogenic centers with high stereoselectivity. The key features of the new method are the unprecedented use of [(MeCN)4Cu]PF6 in conjunction with the Hoveyda ligand L1 and the use of (Z)‐nitroalkene substrates so that undesired nitroalkene isomerization is minimized and enantioselectivity is enhanced dramatically. We also describe a novel, practical, and highly (Z)‐selective nitroalkene synthesis. 相似文献
998.
Ryan Gianatassio Dr. Shuhei Kawamura Cecil L Eprile Dr. Klement Foo Jason Ge Dr. Aaron C. Burns Dr. Michael R. Collins Prof. Dr. Phil S. Baran 《Angewandte Chemie (International ed. in English)》2014,53(37):9851-9855
A simple method to convert readily available carboxylic acids into sulfinate salts by employing an interrupted Barton decarboxylation reaction is reported. A medicinally oriented panel of ten new sulfinate reagents was created using this method, including a key trifluoromethylcyclopropanation reagent, TFCS‐Na. The reactivity of six of these salts towards C? H functionalization was field‐tested using several different classes of heterocycles. 相似文献
999.
Visible‐Light‐Induced CO Release from a Therapeutically Viable Tryptophan‐Derived Manganese(I) Carbonyl (TryptoCORM) Exhibiting Potent Inhibition against E. coli 下载免费PDF全文
Jonathan S. Ward Dr. Jason M. Lynam Dr. James Moir Prof. Ian J. S. Fairlamb 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(46):15061-15068
The first visible‐light‐activated carbon‐monoxide‐releasing molecule (CO‐RM) to exhibit a potent effect against Escherichia coli is described. The easily prepared tryptophan‐derived manganese‐containing complex (TryptoCORM) released 1.4 moles of CO at 465 nm, and 2 moles at 400 nm. A comprehensive synthetic, mechanistic and microbiological study into the behaviour of TryptoCORM is reported. The complex is thermally stable (i.e., does not release CO in solution in the absence of light), shows low toxicity against mammalian cells and releases tryptophan on photoinduced degradation, all of which point to TryptoCORM being therapeutically viable. 相似文献
1000.
Kalon J. Iversen Dr. David J. D. Wilson Dr. Jason L. Dutton 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(43):14132-14138
A computational study has been carried out to examine the feasibility of generating a simple monocyclic cyclopentadienyl cation that may be sufficiently stable to isolate and handle at ambient temperatures. Using judicious placement of electron‐withdrawing groups (CF3) about the ring we have identified a derivative that may approach the stability of isolobal (and isolatable) borole rings, as evaluated by HOMO–LUMO and singlet–triplet gaps. These Cp+ derivatives may therefore be an attractive target for synthetic isolation. 相似文献