全文获取类型
收费全文 | 5935篇 |
免费 | 380篇 |
国内免费 | 206篇 |
专业分类
化学 | 3960篇 |
晶体学 | 50篇 |
力学 | 221篇 |
综合类 | 16篇 |
数学 | 742篇 |
物理学 | 1532篇 |
出版年
2023年 | 54篇 |
2022年 | 87篇 |
2021年 | 105篇 |
2020年 | 116篇 |
2019年 | 102篇 |
2018年 | 125篇 |
2017年 | 82篇 |
2016年 | 185篇 |
2015年 | 175篇 |
2014年 | 212篇 |
2013年 | 366篇 |
2012年 | 400篇 |
2011年 | 428篇 |
2010年 | 289篇 |
2009年 | 268篇 |
2008年 | 370篇 |
2007年 | 349篇 |
2006年 | 330篇 |
2005年 | 275篇 |
2004年 | 233篇 |
2003年 | 221篇 |
2002年 | 179篇 |
2001年 | 136篇 |
2000年 | 137篇 |
1999年 | 90篇 |
1998年 | 83篇 |
1997年 | 54篇 |
1996年 | 95篇 |
1995年 | 63篇 |
1994年 | 56篇 |
1993年 | 61篇 |
1992年 | 54篇 |
1991年 | 49篇 |
1990年 | 39篇 |
1989年 | 35篇 |
1988年 | 34篇 |
1987年 | 36篇 |
1986年 | 33篇 |
1985年 | 57篇 |
1984年 | 35篇 |
1983年 | 36篇 |
1982年 | 27篇 |
1981年 | 44篇 |
1980年 | 33篇 |
1979年 | 28篇 |
1978年 | 33篇 |
1977年 | 33篇 |
1976年 | 24篇 |
1975年 | 29篇 |
1974年 | 39篇 |
排序方式: 共有6521条查询结果,搜索用时 62 毫秒
211.
Denis C. K. Wong 《Mathematics in Computer Science》2016,10(2):223-227
In this paper, we construct some families of binary linear and nonlinear codes by using various bipartite graphs. Furthermore, we also determine some conditions for the constructed binary linear code to be a maximum distance separable code. 相似文献
212.
Bis‐clickable Mesoporous Silica Nanoparticles: Straightforward Preparation of Light‐Actuated Nanomachines for Controlled Drug Delivery with Active Targeting
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Achraf Noureddine Dr. Magali Gary‐Bobo Dr. Laure Lichon Dr. Marcel Garcia Prof. Jeffrey I. Zink Dr. Michel Wong Chi Man Dr. Xavier Cattoën 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(28):9624-9630
Bis(clickable) mesoporous silica nanospheres (ca. 100 nm) were obtained by the co‐condensation of TEOS with variable amounts (2–5 % each) of two clickable organosilanes in the presence of CTAB. Such nanoparticles could be easily functionalized with two independent functions using the copper‐catalyzed alkyne‐azide cycloaddition (CuAAC) reaction to transform them into nanomachines bearing cancer cell targeting ligands with the ability to deliver drugs on‐demand. The active targeting was made possible after anchoring folic acid by CuAAC click reaction, whereas the controlled delivery was performed by clicked azobenzene fragments. Indeed, the azobenzene groups are able to obstruct the pores of the nanoparticles in the dark whereas upon irradiation in the UV or in the blue range, their trans‐to‐cis photoisomerization provokes disorder in the pores, enabling the delivery of the cargo molecules. The on‐command delivery was proven in solution by dye release experiments, and in vitro by doxorubicin delivery. The added value of the folic acid ligand was clearly evidenced by the difference of cell killing induced by doxorubicin‐loaded nanoparticles under blue irradiation, depending on whether the particles featured the clicked folic acid ligand or not. 相似文献
213.
214.
215.
A series of imidazolium chlorides for the formation of tridentate CNO‐donor palladium(II) complexes featuring N‐heterocyclic carbene moieties have been developed from cheap and readily available starting materials with high yields. Their palladium complexes were prepared by reactions between the ligand precursors and PdCl2 using K2CO3 as base in pyridine with reasonable yields. These air‐stable metal complexes were characterized using 1H NMR and 13C{1H} NMR spectroscopy and elemental analyses. Heteronuclear multiple bond correlation experiments were performed to identify key NMR signals of these compounds. The structures of two of the complexes were also established by single‐crystal X‐ray diffraction analysis. One of these complexes was successfully applied in the direct C―H functionalization reactions between heterocyclic compounds and aryl bromides, producing excellent yields of coupled products. The coupling reactions were scalable, allowing grams of coupled products to be obtained with a mere 2 mol% of Pd loading. The catalyst system developed allowed the large‐scale preparation of several push–pull chromophores straightforwardly. Photophysical properties based on UV–visible and fluorescence spectroscopy for these chromophores were investigated. Deep blue photoluminescence with moderate quantum efficiency and twisted intramolecular charge transfer excited state were observed for these chromophores. Density functional theory (DFT) and time‐dependent DFT calculations were performed to support the experimental results. 相似文献
216.
Dr. Valerie H. L. Wong Dr. Sai V. C. Vummaleti Prof. Luigi Cavallo Dr. Andrew J. P. White Prof. Steven P. Nolan Dr. King Kuok Hii 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(37):13320-13327
A general synthetic route was used to prepare 15 new N‐heterocyclic carbene (NHC)–AgI complexes bearing anionic carboxylate ligands [Ag(NHC)(O2CR)], including a homologous series of complexes of sterically flexible ITent ligands, which permit a systematic spectroscopic and theoretical study of the structural and electronic features of these compounds. The complexes displayed a significant ligand‐accelerated effect in the intramolecular cyclisation of propargylic amides to oxazolidines. The substrate scope is highly complementary to that previously achieved by NHC–Au and pyridyl–AgI complexes. 相似文献
217.
A one-pot synthesis of the trisubstituted imidazole derivatives from α-acetoxy-α-chloro-β-keto-esters, aldehydes, and ammonium acetate has been developed. 相似文献
218.
219.
220.
We have recently established preparative procedures for titanium(III) reduction of sulfoxides to sulfides1 and nitroarenes to amines.2 In continuation of this program which is aimed at exploring the synthetic potential of titanium(III) ion, we have found that α-haloketones undergo facile dehalogenation upon treatment with titanium trichloride. 相似文献