全文获取类型
收费全文 | 966篇 |
免费 | 45篇 |
国内免费 | 27篇 |
出版年
2023年 | 13篇 |
2022年 | 13篇 |
2021年 | 18篇 |
2020年 | 23篇 |
2019年 | 22篇 |
2018年 | 33篇 |
2017年 | 28篇 |
2016年 | 21篇 |
2015年 | 28篇 |
2014年 | 47篇 |
2013年 | 85篇 |
2012年 | 20篇 |
2011年 | 43篇 |
2010年 | 28篇 |
2009年 | 32篇 |
2008年 | 37篇 |
2007年 | 37篇 |
2006年 | 29篇 |
2005年 | 25篇 |
2004年 | 21篇 |
2003年 | 17篇 |
2002年 | 18篇 |
2001年 | 17篇 |
2000年 | 8篇 |
1999年 | 23篇 |
1998年 | 12篇 |
1997年 | 23篇 |
1996年 | 7篇 |
1995年 | 5篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1991年 | 7篇 |
1990年 | 3篇 |
1989年 | 9篇 |
1988年 | 9篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 30篇 |
1984年 | 20篇 |
1983年 | 30篇 |
1982年 | 45篇 |
1981年 | 40篇 |
1980年 | 30篇 |
1979年 | 25篇 |
1978年 | 12篇 |
1977年 | 12篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1974年 | 4篇 |
1973年 | 6篇 |
排序方式: 共有1038条查询结果,搜索用时 46 毫秒
991.
Ji-Hong Gu Jun-Shan Liu Jia-Hui Lin Fen Liu Zhen-Long Wu Yuan-Ru Zheng Wen-Cai Ye Lei Wang 《化学与生物多样性》2023,20(2):e202201111
Leptosperols C−G ( 1 – 5 ), five new phenylpropanoyl phloroglucinol derivatives were isolated from the leaves of Leptospermum scoparium. Compounds 1–3 are phenylpropanoyl phloroglucinol-sesquiterpene adducts with new carbon skeletons. Their structures with absolute configurations were elucidated by detailed spectroscopic analyses, single-crystal X-ray diffraction, and electronic circular dichroism (ECD) calculation. Compounds 2 and 3 exhibited moderate anti-inflammatory activity in zebrafish acute inflammatory models. 相似文献
992.
Tetranitromethane was used to selectively modify tyrosine residues of a humanized anti-cocaine mAb (h2E2), under development for the treatment of cocaine use disorders. The effect of mild tyrosine nitration on the affinity of cocaine and two high affinity cocaine metabolites, cocaethylene and benzoylecgonine, was assessed using differential scanning fluorimetry to measure ligand affinities via ligand-induced thermal stabilization of the mAb antigen binding region. Nitrated tyrosine residues were identified by mass spectral analysis of thermolysin peptides. One objective was to understand the binding affinity differences observed for these three ligands, which are not explained by the published crystal structure of the h2E2 mAb Fab fragment co-crystalized with benzoylecgonine, since the carboxylic acid of benzoylecgonine that is esterified to form cocaine and cocaethylene is not in contact with the mAb. Importantly, the binding affinity of the cocaine metabolite benzoylecgonine was not decreased by mild nitration, whereas the binding affinities of cocaine and cocaethylene were decreased about two-fold. These ligands differ only in the substituent attached to the carboxylate moiety of the compound, with benzoylecgonine having an unesterified carboxylate, and cocaine and cocaethylene having methyl and ethyl esters, respectively, at this position. The results are consistent with nitration of light chain tyrosine residue 34, resulting in a less favorable interaction with cocaine and cocaethylene carboxylate esters, while not affecting binding of benzoylecgonine. Thus, light chain Tyr34 residue may have molecular interactions with cocaine and cocaethylene not present for benzoylecgonine, leading to the observed affinity differences for these three ligands. 相似文献
993.
Alberto Ramos Angel Vizoso Aymeé Edreira José Betancourt Mercedes Décalo 《Mutation Research - Genetic Toxicology and Environmental Mutagenesis》1997,390(3):233
Mutagenicity of a substituted nitroalkene, 1-(5-bromofur-2-il)-2-bromo-2-nitroethene (BNF) was tested in the Salmonella/microsome assay using the strains TA 98, TA 100 and TA 100NR (nitroreductase deficient). BNF was a direct mutagen in TA 98 and TA 100; the response was lowered when exogenous metabolic activation (S9) was used. A further decrease in mutagenicity was observed in strain TA 100NR, as compared to the parental TA 100, which showed the involvement of nitroreduction in the overall response elicited by BNF. The micronucleus assay was carried out in Swiss male mice which were given a single i.p. dose of 10–20 mg/kg of BNF dissolved in peanut oil, bone marrow being sampled 24 and 48 h later. The micronucleated polychromatic erythrocyte counts (MNPCE) showed a weak response in the dose range of 10–17.5 mg/kg at the second sampling (48 h) and a significant rise for 20 mg/kg at 24 and 48 h. 相似文献
994.
995.
Hiroki Kobayashi Haruna Nishimura Norio Kudo Hiroyuki Osada 《Bioscience, biotechnology, and biochemistry》2020,84(10):2113-2120
ABSTRACT Small molecules that regulate cell stemness have the potential to make a major contribution to regenerative medicine. In the course of screening for small molecules that affect stemness in mouse embryonic stem cells (mESCs), we discovered that NPD13432, an aurone derivative, promoted self-renewal of mESCs. Normally, mESCs start to differentiate upon withdrawal of 2i/LIF. However, cells treated with the compound continued to express endogenous Nanog, a pluripotency marker protein essential for sustaining the undifferentiated state, even in the absence of 2i/LIF. Biochemical characterization revealed that NPD13432 inhibited GSK3α and GSK3β with IC50 values of 92 nM and 310 nM, respectively, suggesting that the compound promotes self-renewal in mESCs by inhibiting GSK3. The chemical structure of the compound is unique among known molecules with this activity, providing an opportunity to develop new inhibitors of GSK3, as well as chemical tools for investigating cell stemness. 相似文献
996.
Xiaoxia Zhu Ying Liu Yunwei Hu Xin Lv Zhaoxia Shi Yuanyuan Yu Xueyang Jiang Feng Feng Jian Xu 《化学与生物多样性》2021,18(8):e2100314
One new dioxolanone derivative, guignardianone G ( 1 ) and twelve known compounds ( 2 – 13 ) were isolated from the 95 % ethanol extract of the plant endophytic fungus Phyllosticta capitalensis cultured in rice medium. Among these known compounds, isoaltenuene ( 3 ), brassicasterol ( 7 ), 5,6-epoxyergosterol ( 8 ), citreoanthrasteroid A ( 9 ), demethylincisterol A ( 10 ), and chaxine C ( 11 ) were reported from Phyllosticta sp. for the first time. The structure of 1 was elucidated by 1D- and 2D-NMR experiments and HR-ESI-MS data analysis, and its absolute configuration was established through the comprehensive use of the methods of modified Mosher methods, calculations of ECD spectra and optical rotation values. The neuroprotective activity of compounds ( 1 – 9 , 11 – 13 ) were evaluated on PC12 cells damage induced by glutamate, and compounds 9 and 12 showed potential neuroprotective activities with half effective concentration (EC50) of 24.2 and 33.9 μM, respectively. 相似文献
997.
Ying Peng Qingzhu Liu Dong Xu Ke Li Hang Li Ling Qiu Jianguo Lin 《Cell biology international》2021,45(5):1015-1029
Bisphosphonates (BPs), especially zoledronic acid (ZOL), are clinically used to treat osteolytic bone lesions. However, serious side-effects may be also induced during the therapeutic process. To improve the BPs drugs, here, we investigated the effects of a series of ZOL derivatives with increasing number of methylene linker between the imidazole ring and the P–C–P backbone named IPrDP, IBDP, IPeDP, and IHDP on cell viability and receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast differentiation, function and apoptosis induction in mouse bone marrow-derived macrophages (BMMs). Our results suggested that IPeDP and IHDP, which contains 4 and 5 methylene linkers, respectively, exerted lower toxicity on BMMs compared with ZOL, IPrDP, and IBDP, which contains 1, 2, and 3 methylene linkers respectively. At concentrations below cytotoxicity threshold, IPeDP and IHDP possessed strong abilities of antiosteoclast formation, antibone absorption, and inducing osteoclast apoptosis, which were similar to ZOL and more powerful than IPrDP and IBDP. The mechanism behind these effects of IPeDP and IHDP might involve the interference of small GTPases prenylation through suppression of mevalonate pathway. The downregulation of JNK and Akt phosphorylation and subsequent inhibition of the expression of c-Fos and NFATc1 might also be involved. Our results supported the potential usage of IPeDP and IHDP to treat bone-related disorders involving increased osteoclastogenesis. Our attempt to extend the methylene linker between the imidazole ring and the P–C–P backbone of ZOL also reveals some regularities between the structure and properties of the BPs drugs. 相似文献
998.
999.
Gen Chen Hao Wan Wei Ma Ning Zhang Yijun Cao Xiaohe Liu Jun Wang Renzhi Ma 《Liver Transplantation》2020,10(11)
Layered metal hydroxides (LMHs) are regarded as a novel and important class of inorganic functional materials. They have unique layered structure and variable chemical compositions that can be readily tuned. In this review, summarized are the recent advances of synthetic routes to the LMHs with designed morphology, composition, and function for electrocatalysis. Versatile products can be readily derived by hybridization, anion‐exchange, surface modification, self‐assembly, etc. More importantly, LMHs can be artificially exfoliated into unilamellar nanosheets with a molecular‐level thickness of about 1 nm versus 2D lateral size in submicrometer or micrometer scale. Molecular‐scale assembly can be then applied to fabricate superlattice‐like composites and functional nanofilms with high quality. The hydroxides can be transformed into oxides, nitrides, or other compounds via different preparation procedures, which can further extend their application prospects. In this regard, the most promising electrocatalysis‐related applications of LMHs and their derivatives are reviewed, such as oxygen evolution reaction, oxygen reduction reaction, hydrogen evolution reaction, CO2 reduction reaction, alcohol or urea electrooxidation, etc. At last, future challenges are also discussed from the aspect of synthesis and application, as well as encouraging advancements are anticipated. 相似文献
1000.