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781.
本文以Ni70Mn25Co5和Fe64Ni36合金及其复合合金作为触媒,采用高温高压温度梯度法在5.6 GPa压力下,对不同温度下沿(100)晶面生长的Ⅰb型金刚石的生长特性进行了研究,研究表明:以Fe64Ni36触媒合成出的金刚石在以(111)晶面为主的晶形高温生长范围内出现了一段约50 K范围的裂晶生长区,而以Ni70Mn25Co5触媒合成的金刚石在生长温度范围内,特别是在以(111)晶面为主的晶体生长高温区域内容易出现连晶缺陷;高温下Fe64Ni36触媒过度熔融可能是晶体容易产生裂晶的原因,Ni70Mn25Co5触媒熔体黏性较低可能是容易形成连晶的原因;采用两种触媒复合的方式有效避免了裂晶和连晶的产生;拉曼光谱表征发现连晶的晶体内部质量与单晶的晶体质量相近,裂晶中晶格畸变和杂质较多,晶体内应力较大,复合触媒体系合成的金刚石晶体内应力小,质量好。 相似文献
782.
783.
Hermann Neitz Dr. Irene Bessi Valentin Kachler Manuela Michel Prof. Dr. Claudia Höbartner 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2023,135(1):e202214456
Arene-fluoroarene interactions offer outstanding possibilities for engineering of supramolecular systems, including nucleic acids. Here, we implement the tolane-perfluorotolane interaction as base pair replacement in DNA. Tolane (THH) and perfluorotolane (TFF) moieties were connected to acyclic backbone units, comprising glycol nucleic acid (GNA) or butyl nucleic acid (BuNA) building blocks, that were incorporated via phosphoramidite chemistry at opposite positions in a DNA duplex. Thermodynamic analyses by UV thermal melting revealed a compelling stabilization by THH/TFF heteropairs only when connected to the BuNA backbone, but not with the shorter GNA linker. Detailed NMR studies confirmed the preference of the BuNA backbone for enhanced polar π-stacking. This work defines how orthogonal supramolecular interactions can be tailored by small constitutional changes in the DNA backbone, and it inspires future studies of arene-fluoroarene-programmed assembly of DNA. 相似文献
784.
Kevin S. Li Deondre Jordan Linda Y. Lin Sawyer E. McCarthy Dr. John S. Schneekloth Jr. Dr. Liliya A. Yatsunyk 《Angewandte Chemie (International ed. in English)》2023,62(26):e202301666
An i-motif is a non-canonical DNA structure implicated in gene regulation and linked to cancers. The C-rich strand of the HRAS oncogene, 5′-CGCCC GTGCCC TGCGCCC GCAACCC GA-3′ (herein referred to as iHRAS), forms an i-motif in vitro but its exact structure was unknown. HRAS is a member of the RAS proto-oncogene family. About 19 % of US cancer patients carry mutations in RAS genes. We solved the structure of iHRAS at 1.77 Å resolution. The structure reveals that iHRAS folds into a double hairpin. The two double hairpins associate in an antiparallel fashion, forming an i-motif dimer capped by two loops on each end and linked by a connecting region. Six C−C+ base pairs form each i-motif core, and the core regions are extended by a G−G base pair and a cytosine stacking. Extensive canonical and non-canonical base pairing and stacking stabilizes the connecting region and loops. The iHRAS structure is the first atomic resolution structure of an i-motif from a human oncogene. This structure sheds light on i-motifs folding and function in the cell. 相似文献
785.
Han-Bin Xu Dr. Hua-Ying Chen Dr. Jian Lv Dr. Bin-Bin Chen Ze-Rui Zhou Shuai Chang Ya-Ting Gao Wen-Fei Huang Ming-Jie Ye Zi-Jian Cheng Dr. Mahmoud Elsayed Hafez Prof. Ruo-Can Qian Prof. Da-Wei Li 《Angewandte Chemie (International ed. in English)》2023,62(44):e202311002
Artificially performing chemical reactions in living biosystems to attain various physiological aims remains an intriguing but very challenging task. In this study, the Schiff base reaction was conducted in cells using Sc(OTf)3 as a catalyst, enabling the in situ synthesis of a hollow covalent organic polymer (HCOP) without external stimuli. The reversible Schiff base reaction mediated intracellular Oswald ripening endows the HCOP with a spherical, hollow porous structure and a large specific surface area. The intracellularly generated HCOP reduced cellular motility by restraining actin polymerization, which consequently induced mitochondrial deactivation, apoptosis, and necroptosis. The presented intracellular synthesis system inspired by the Schiff base reaction has strong potential to regulate cell fate and biological functions, opening up a new strategic possibility for intervening in cellular behavior. 相似文献
786.
Dr. Xun Liu Ziyin Zhao Wei Li Yajie Li Qiang Yang Ningyu Liu Prof. Yongbing Chen Prof. Lichen Yin 《Angewandte Chemie (International ed. in English)》2023,62(45):e202307664
Protein therapeutics targeting intracellular machineries hold profound potential for disease treatment, and hence robust cytosolic protein delivery technologies are imperatively demanded. Inspired by the super-negatively charged, nucleotide-enriched structure of nucleic acids, adenylated pro-proteins (A-proteins) with dramatically enhanced negative surface charges have been engineered for the first time via facile green synthesis. Then, thymidine-modified polyethyleneimine is developed, which exhibits strong electrostatic attraction, complementary base pairing, and hydrophobic interaction with A-proteins to form salt-resistant nanocomplexes with robust cytosolic delivery efficiencies. The acidic endolysosomal environment enables traceless restoration of the A-proteins and consequently promotes the intracellular release of the native proteins. This strategy shows high efficiency and universality for a variety of proteins with different molecular weights and isoelectric points in mammalian cells. Moreover, it enables highly efficient delivery of CRISPR-Cas9 ribonucleoproteins targeting fusion oncogene EWSR1-FLI1, leading to pronounced anti-tumor efficacy against Ewing sarcoma. This study provides a potent and versatile platform for cytosolic protein delivery and gene editing, and may benefit the development of protein pharmaceuticals. 相似文献
787.
Dr. Peng Chen Shun-Zhong Tan Dr. Lei Zhu Prof. Dr. Qin Ouyang Prof. Dr. Zhi-Jun Jia Prof. Dr. Wei Du Prof. Dr. Ying-Chun Chen 《Angewandte Chemie (International ed. in English)》2023,62(23):e202301519
σ-Lewis base-catalyzed regio- and enantioselective aza-Morita–Baylis–Hillman (MBH) reaction of α,β,γ,δ-unsaturated systems remains a challenge due to the intrinsic covalent activation mode. Here we demonstrate that a Pd0 complex can mediate the dehydrogenative reaction of γ,δ-unsaturated compounds to give corresponding electron-poor dienes, which further undergo δ-regioselective umpolung Friedel–Crafts-type addition to imines via auto-tandem Pd0-π-Lewis base catalysis. After β-H elimination of in situ formed PdII-complexes, unprecedented and chemically inverse aza-MBH-type adducts are finally furnished with fair to outstanding enantioselectivity, and a diversity of functional groups and both ketimine and aldimine acceptors can be well tolerated. Moreover, switchable α-regioselective normal aza-MBH-type reaction also can be realized by tuning catalytic conditions, whereas moderate to good enantioselectivity with low to excellent Z/E-selectivity is attained. 相似文献