全文获取类型
收费全文 | 2270篇 |
免费 | 59篇 |
国内免费 | 11篇 |
专业分类
化学 | 1730篇 |
晶体学 | 18篇 |
力学 | 25篇 |
综合类 | 1篇 |
数学 | 95篇 |
物理学 | 471篇 |
出版年
2022年 | 16篇 |
2021年 | 25篇 |
2020年 | 36篇 |
2019年 | 46篇 |
2018年 | 17篇 |
2017年 | 19篇 |
2016年 | 32篇 |
2015年 | 45篇 |
2014年 | 46篇 |
2013年 | 106篇 |
2012年 | 114篇 |
2011年 | 129篇 |
2010年 | 64篇 |
2009年 | 52篇 |
2008年 | 138篇 |
2007年 | 137篇 |
2006年 | 117篇 |
2005年 | 111篇 |
2004年 | 92篇 |
2003年 | 93篇 |
2002年 | 99篇 |
2001年 | 58篇 |
2000年 | 50篇 |
1999年 | 24篇 |
1998年 | 18篇 |
1997年 | 15篇 |
1996年 | 23篇 |
1995年 | 15篇 |
1994年 | 26篇 |
1993年 | 27篇 |
1992年 | 27篇 |
1991年 | 29篇 |
1990年 | 25篇 |
1989年 | 19篇 |
1988年 | 23篇 |
1987年 | 32篇 |
1986年 | 24篇 |
1985年 | 38篇 |
1984年 | 24篇 |
1983年 | 17篇 |
1982年 | 21篇 |
1981年 | 15篇 |
1980年 | 22篇 |
1979年 | 23篇 |
1978年 | 28篇 |
1977年 | 23篇 |
1976年 | 20篇 |
1975年 | 30篇 |
1974年 | 22篇 |
1973年 | 18篇 |
排序方式: 共有2340条查询结果,搜索用时 15 毫秒
111.
Unsymmetrical oxamides are conveniently synthesized in good yields by a new trapping reaction of unstable carbamoyl lithiums with isocyanates. 相似文献
112.
Sulfonylurea derivatives including useful antidiabetics (Tolbutamide, Chlorpropamide) were synthesized in good yields from benzene-sulfonamides with thiocarbamates in the presence of DBU. Thiocarbamates were prepared by the selenium-assisted carbonylation of primary amines with carbon monoxide, sulfur, and methyl iodide under mild conditions. 相似文献
113.
Yiliang Wu Jun-Ichi Mamiya Osamu Tsutsumi Akihiko Kanazawa Takeshi Shiono Tomiki Ikeda 《Liquid crystals》2013,40(6):749-753
Photoinduced alignment in a polymer liquid crystal prepared from 6-{1-[4-(2-cyano-4-nitrophenylazo)phenyl]piperazino}hexyl acrylate and 4'-[6-(methacryloyloxy)hexyloxy]-4-cyanobiphenyl was investigated for the first time on irradiation with a polarized He-Ne laser beam at 633 nm. The azobenzene moieties as well as the inert cyanobiphenyl mesogenic units were aligned with the molecular long axis perpendicular to the polarization direction of the irradiation light. Alignment induced on short irradiation was reversible, while that induced under prolonged irradiation was irreversible due to the occurrence of crosslinking which might be caused by photoinduced decomposition of the azobenzene moieties during the photoirradiation process. 相似文献
114.
A novel oligonucleotide delivery system that is based on oligonucleotide–nanoparticle conjugates has been described. Installed oligonucleotides were modified with the carbohydrate at the 3′ terminus, accordingly, constructed nanoparticles display clustered carbohydrates on their outer layer for the targeted delivery of oligonucleotides. The method for the construction of ligand-functionalized nanoparticle was simple and reproducible. The stability of the nanoparticles displaying clustered carbohydrates greatly increased in serum compared to nanoparticles without carbohydrates. In order to investigate the targetability of oligonucleotide–nanoparticle conjugates into primary hepatic parenchymal cells, freshly isolated rat hepatocytes were incubated with nanoparticles and the amount of internalized gold nanoparticles was evaluated by an inductively coupled plasma mass spectroscopy analysis. Nanoparticles displaying clustered carbohydrates internalized more efficiently than nanoparticles without carbohydrate modifications. In particular, the cellular uptakes of oligonucleotide-conjugated gold nanoparticle increased 1.7 ~2.0-fold by galactose modification. Competition assay revealed that clustered galactose enhanced the internalization of the nanoparticle into primary hepatic parenchymal cells by a receptor-mediated process. Figure
A novel oligonucleotide delivery system that is based on oligonucleotide-nanoparticle conjugates has been described. Constructed nanoparticles display clustered carbohydrates on their outer layer. The stability of the nanoparticles displaying clustered carbohydrates increased in serum, and clustered galactose enhanced the internalization of the nanoparticle to hepatic parenchymal cells by a receptor-mediated process 相似文献
115.
116.
A one-pot approach to indolo[2,1-b]quinazolines from indole-3-carbaldehydes through the Dakin oxidation was developed. It was shown that the reaction proceeded through the condensation of indole-3-carbaldehydes with isatoic anhydrides, derived in situ from indole-3-carbaldehydes by the Dakin oxidation, and further oxidation/cyclization steps. 相似文献
117.
118.
Katsuya Oji Asako Igashira‐Kamiyama Nobuto Yoshinari Takumi Konno 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(7):2023-2027
A novel AuICoIII coordination system that is derived from the newly prepared [Co(D ‐nmp)2]− ( 1 −; D ‐nmp=N‐methyl‐D ‐penicillaminate) and a gold(I) precursor AuI is reported. Complex 1 − acts as a sulfur‐donating metallaligand and reacts with the gold(I) precursor to give [Au2Co2(D ‐nmp)4] ( 2 ), which has an eight‐membered AuI2CoIII2 metallaring. Treatment of 2 with [Au2(dppe)2]2+ (dppe=1,2‐bis(diphenylphosphino)ethane) leads to the formation of [Au4Co2(dppe)2(D ‐nmp)4]2+ ( 3 2+), which consists of an 18‐membered AuI4CoIII2 metallaring that accommodates a tetrahedral anion (BF4−, ClO4−, ReO4−). In solution, the metallaring structure of 3 2+ is readily interconvertible with the nine‐membered AuI2CoIII metallaring structure of [Au2Co(dppe)(D ‐nmp)2]+ ( 4 +); this process depends on external factors, such as solvent, concentration, and nature of the counteranion. These results reveal the lability of the Au S and Au P bonds, which is essential for metallaring expansion and contraction. 相似文献
119.
120.
We study the effects of metal-coated fiber near-field probes on the performance of nanophotonic devices. Employing a heterodyne near-field scanning optical microscope and analyzing transmission characteristics, we find that a metal-coated probe can typically introduce a 3 dB intensity loss and a 0.2 rad phase shift during characterization of a straight waveguide made in a silicon-on-insulator system. In resonant nanophotonic structures such as a 5 mum radius microring resonator, we demonstrate that the probe induces a 1 nm shift in resonant wavelength and decreases the resonator quality factor, Q, from 1100 to 480. 相似文献