全文获取类型
收费全文 | 2841篇 |
免费 | 122篇 |
国内免费 | 8篇 |
专业分类
化学 | 2348篇 |
晶体学 | 22篇 |
力学 | 21篇 |
数学 | 163篇 |
物理学 | 417篇 |
出版年
2023年 | 26篇 |
2022年 | 21篇 |
2021年 | 39篇 |
2020年 | 68篇 |
2019年 | 56篇 |
2018年 | 20篇 |
2017年 | 14篇 |
2016年 | 64篇 |
2015年 | 64篇 |
2014年 | 80篇 |
2013年 | 141篇 |
2012年 | 177篇 |
2011年 | 194篇 |
2010年 | 105篇 |
2009年 | 88篇 |
2008年 | 204篇 |
2007年 | 188篇 |
2006年 | 195篇 |
2005年 | 188篇 |
2004年 | 183篇 |
2003年 | 138篇 |
2002年 | 140篇 |
2001年 | 41篇 |
2000年 | 44篇 |
1999年 | 47篇 |
1998年 | 37篇 |
1997年 | 40篇 |
1996年 | 24篇 |
1995年 | 23篇 |
1994年 | 19篇 |
1993年 | 16篇 |
1992年 | 17篇 |
1991年 | 14篇 |
1989年 | 17篇 |
1988年 | 15篇 |
1987年 | 12篇 |
1985年 | 27篇 |
1984年 | 23篇 |
1983年 | 12篇 |
1982年 | 21篇 |
1981年 | 22篇 |
1980年 | 17篇 |
1979年 | 14篇 |
1978年 | 7篇 |
1977年 | 13篇 |
1976年 | 10篇 |
1975年 | 6篇 |
1974年 | 6篇 |
1973年 | 7篇 |
1972年 | 7篇 |
排序方式: 共有2971条查询结果,搜索用时 31 毫秒
951.
We propose a scalable and practical implementation of spin amplification which does not require individual addressing nor a specially tailored spin network. We have demonstrated a gain of 140 in a solid-state nuclear spin system of which the spin polarization has been increased to 0.12 using dynamic nuclear polarization with photoexcited triplet electron spins. Spin amplification scalable to a higher gain opens the door to the single spin measurement for a readout of quantum computers as well as practical applications of nuclear magnetic resonance spectroscopy to infinitesimal samples which have been concealed by thermal noise. 相似文献
952.
Yoshihiro Furukawa Kiyoharu Tadanaga Akitoshi Hayashi Masahiro Tatsumisago 《Solid State Ionics》2011,192(1):185-187
This study demonstrates that humidity, temperature, and the interlayer anions influence ionic conductivities of Mg–Al layered double hydroxides (LDHs) intercalated with inorganic anions. Results show that Mg–Al LDH intercalated with Br? exhibited the highest ionic conductivity among Mg–Al LDHs intercalated with CO32?, Cl?, Br?, NO3? and SO42?. Its ionic conductivity was 1.1 × 10? 2 S cm? 1 at 80 °C under 80% relative humidity. The electromotive force for the hydroxide ion concentration cell using Mg?Al CO32? LDH showed the same behavior with that using an anion exchange membrane, indicating that Mg–Al CO32? LDH can be a hydroxide ion conductor. 相似文献
953.
Ki‐Young Lee Zhenhao Fang Masahiro Enomoto Genevieve Gasmi‐Seabrook Le Zheng Shohei Koide Mitsuhiko Ikura Christopher B. Marshall 《Angewandte Chemie (International ed. in English)》2020,59(27):11037-11045
KRAS homo‐dimerization has been implicated in the activation of RAF kinases, however, the mechanism and structural basis remain elusive. We developed a system to study KRAS dimerization on nanodiscs using paramagnetic relaxation enhancement (PRE) NMR spectroscopy, and determined distinct structures of membrane‐anchored KRAS dimers in the active GTP‐ and inactive GDP‐loaded states. Both dimerize through an α4–α5 interface, but the relative orientation of the protomers and their contacts differ substantially. Dimerization of KRAS‐GTP, stabilized by electrostatic interactions between R135 and E168, favors an orientation on the membrane that promotes accessibility of the effector‐binding site. Remarkably, “cross”‐dimerization between GTP‐ and GDP‐bound KRAS molecules is unfavorable. These models provide a platform to elucidate the structural basis of RAF activation by RAS and to develop inhibitors that can disrupt the KRAS dimerization. The methodology is applicable to many other farnesylated small GTPases. 相似文献
954.
Azusa Kondoh Masafumi Oishi Hikaru Tezuka Masahiro Terada 《Angewandte Chemie (International ed. in English)》2020,59(19):7472-7477
In the field of chiral Brønsted base catalysis, a new generation of chiral catalysts has been highly anticipated to overcome the intrinsic limitation of pronucleophiles that are applicable to the enantioselective reactions. Herein, we reveal conceptually new chiral Brønsted base catalysts consisting of two different organobase functionalities, one of which functions as an organosuperbase and the other as the substrate recognition site. Their prominent activity, which stems from the distinctive cooperative function by the two organobases in a single catalyst molecule, was demonstrated in the unprecedented enantioselective direct Mannich‐type reaction of α‐phenylthioacetate as a less acidic pronucleophile. The present achievement would provide a new guiding principle for the design and development of chiral Brønsted base catalysts and significantly broaden the utility of Brønsted base catalysis in asymmetric organic synthesis. 相似文献
955.
Mineto Uchiyama Masahiro Osumi Kotaro Satoh Masami Kamigaito 《Angewandte Chemie (International ed. in English)》2020,59(17):6832-6838
Thiol‐ene cationic and radical reactions were conducted for 1:1 addition between a thiol and vinyl ether, and also for cyclization and step‐growth polymerization between a dithiol and divinyl ether. p‐Toluenesulfonic acid (PTSA) induced a cationic thiol‐ene reaction to generate a thioacetal in high yield, whereas 2,2′‐azobisisobutyronitrile resulted in a radical thiol‐ene reaction to give a thioether, also in high yield. The cationic and radical addition reactions between a dithiol and divinyl ether with oxyethylene units yielded amorphous poly(thioacetal)s and crystalline poly(thioether)s, respectively. Under high‐dilution conditions, the cationic and radical reactions resulted in 16‐ and 18‐membered cyclic thioacetal and thioether products, respectively. Furthermore, concurrent cationic and radical step‐growth polymerizations were realized using PTSA under UV irradiation to produce polymers having both thioacetal and thioether linkages in the main chain. 相似文献
956.
Eiki Tomita Kodai Yamada Yu Shibata Ken Tanaka Masahiro Kojima Tatsuhiko Yoshino Shigeki Matsunaga 《Angewandte Chemie (International ed. in English)》2020,59(26):10474-10478
The synthesis, characterization, and catalytic performance of iridium(III) catalysts that bear an amide‐pendant cyclopentadienyl ligand ([CpAIrI2]2) is reported. These [CpAIrI2]2 catalysts were obtained from the complexation of a CpA ligand precursor with [Ir(cod)OAc]2 followed by oxidation. Double aromatic homologation reactions of benzamides with alkynes by fourfold C?H activation proceeded in good to high yield with these [CpAIrI2]2 catalysts, demonstrating their superior catalytic performance in this challenging transformation. 相似文献
957.
Yusuke Masuda Hiromu Tsuda Masahiro Murakami 《Angewandte Chemie (International ed. in English)》2020,59(7):2755-2759
Unprotected aldoses in water undergo an isomerization reaction via a radical pathway when irradiated with light in the presence of water‐soluble benzophenone. Whereas its anomeric carbon (C1) is oxidized to a carboxy group, the hydroxy group on the C2 carbon is replaced by hydrogen. The generated 2‐deoxy lactones are readily reduced to the corresponding 2‐deoxy aldoses, which are often contained in bioactive compounds. 相似文献
958.
Shokichi Tsukamoto Masahiro Takeuchi Takeharu Kawaguchi Emi Togasaki Atsuko Yamazaki Yasumasa Sugita Tomoya Muto Shio Sakai Yusuke Takeda Chikako Ohwada Emiko Sakaida Naomi Shimizu Keigo Nishii Meizi Jiang Koutaro Yokote Hideaki Bujo Chiaki Nakaseko 《Experimental & molecular medicine》2014,46(4):e89
LR11, also known as SorLA or SORL1, is a type-I membrane protein from which a large extracellular part, soluble LR11 (sLR11), is released by proteolytic shedding on cleavage with a disintegrin and metalloproteinase 17 (ADAM17). A shedding mechanism is presumed to have a key role in the functions of LR11, but the evidence for this has not yet been demonstrated. Tetraspanin CD9 has been recently shown to regulate the ADAM17-mediated shedding of tumor necrosis factor-α and intercellular adhesion molecule-1 on the cell surface. Here, we investigated the role of CD9 on the shedding of LR11 in leukocytes. LR11 was not expressed in THP-1 monocytes, but it was expressed and released in phorbol 12-myristate 13-acetate (PMA)-induced THP-1 macrophages (PMA/THP-1). Confocal microscopy showed colocalization of LR11 and CD9 proteins on the cell surface of PMA/THP-1. Ectopic neo-expression of CD9 in CCRF-SB cells, which are LR11-positive and CD9-negative, reduced the amount of sLR11 released from the cells. In contrast, incubation of LR11-transfected THP-1 cells with neutralizing anti-CD9 monoclonal antibodies increased the amount of sLR11 released from the cells. Likewise, the PMA-stimulated release of sLR11 increased in THP-1 cells transfected with CD9-targeted shRNAs, which was negated by treatment with the metalloproteinase inhibitor GM6001. These results suggest that the tetraspanin CD9 modulates the ADAM17-mediated shedding of LR11 in various leukemia cell lines and that the association between LR11 and CD9 on the cell surface has an important role in the ADAM17-mediated shedding mechanism. 相似文献
959.
Silylation Improves the Photodynamic Activity of Tetraphenylporphyrin Derivatives In Vitro and In Vivo
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)
Prof. Hiroaki Horiuchi Prof. Masahiro Hosaka Hiroyuki Mashio Motoki Terata Prof. Shintaro Ishida Prof. Soichiro Kyushin Prof. Tetsuo Okutsu Prof. Toshiyuki Takeuchi Prof. Hiroshi Hiratsuka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(20):6054-6060
The effects of silyl and hydrophilic groups on the photodynamic properties of tetraphenylporphyrin (TPP) derivatives have been studied in vitro and in vivo. Silylation led to an improvement in the quantum yield of singlet oxygen sensitization for both sulfo and carboxy derivatives, although the silylation did not affect other photophysical properties. Silylation also improved the cellular uptake efficiency for both sulfo and carboxy derivatives, enhancing the in vitro photodynamic activity of the photosensitizer in U251 human glioma cells. The carboxy derivative (SiTPPC4) was found to show higher cellular uptake efficiency and in vitro photodynamic activity than the corresponding sulfo derivative (SiTPPS4), which indicates that the carboxy group is a more promising hydrophilic group than the sulfo group in the silylated porphyrin. SiTPPC4 was found to show high selective accumulation efficiency in tumors, although almost no tumor selectivity was observed for the nonsilylated porphyrin. The concentration of SiTPPC4 in tumors was 13 times higher than that in muscle 12 h after drug administration. We also studied tumor response after treatment and found that silylation enhanced in vivo photodynamic activity significantly. SiTPPC4 shows higher photodynamic activity than NPe6 with white light irradiation. 相似文献
960.
Efficient Synthesis of Eight‐Membered Nitrogen Heterocycles from O‐Propargylic Oximes by Rhodium‐Catalyzed Cascade Reactions
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)
Prof. Dr. Itaru Nakamura Yoshinori Sato Keisuke Takeda Prof. Dr. Masahiro Terada 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(33):10214-10219
Azocine derivatives were successfully synthesized from O‐propargylic oximes by means of a Rh‐catalyzed 2,3‐rearrangement/heterocyclization cascade reaction. Moreover, the chirality of the substrate was maintained throughout the cascade process to afford the corresponding optically active azocines. 相似文献