首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2319篇
  免费   71篇
  国内免费   25篇
  2023年   27篇
  2022年   12篇
  2021年   33篇
  2020年   78篇
  2019年   133篇
  2018年   131篇
  2017年   107篇
  2016年   94篇
  2015年   45篇
  2014年   136篇
  2013年   244篇
  2012年   32篇
  2011年   103篇
  2010年   51篇
  2009年   80篇
  2008年   83篇
  2007年   79篇
  2006年   84篇
  2005年   51篇
  2004年   50篇
  2003年   56篇
  2002年   49篇
  2001年   19篇
  2000年   15篇
  1999年   15篇
  1998年   19篇
  1997年   12篇
  1996年   12篇
  1995年   18篇
  1994年   22篇
  1993年   18篇
  1992年   25篇
  1991年   13篇
  1990年   7篇
  1989年   9篇
  1987年   8篇
  1986年   6篇
  1985年   55篇
  1984年   54篇
  1983年   21篇
  1982年   48篇
  1981年   43篇
  1980年   52篇
  1979年   50篇
  1978年   36篇
  1977年   25篇
  1976年   17篇
  1975年   10篇
  1974年   6篇
  1973年   16篇
排序方式: 共有2415条查询结果,搜索用时 70 毫秒
81.
Abstract

A series of new 2,4-bis[(substituted-aminomethyl)phenyl]quinoline, 1,3-bis[(substituted-aminomethyl)phenyl]isoquinoline, and 2,4-bis[(substituted-aminomethyl)phenyl]quinazoline derivatives was designed, synthesised, and evaluated in?vitro against three protozoan parasites (Plasmodium falciparum, Leishmania donovani, and Trypanosoma brucei brucei). Biological results showed antiprotozoal activity with IC50 values in the µM range. In addition, the in?vitro cytotoxicity of these original molecules was assessed with human HepG2 cells. The quinoline 1c was identified as the most potent antimalarial candidate with a ratio of cytotoxic to antiparasitic activities of 97 against the P. falciparum CQ-sensitive strain 3D7. The quinazoline 3h was also identified as the most potent trypanosomal candidate with a selectivity index (SI) of 43 on T. brucei brucei strain. Moreover, as the telomeres of the parasites P. falciparum and Trypanosoma are possible targets of this kind of nitrogen heterocyclic compounds, we have also investigated stabilisation of the Plasmodium and Trypanosoma telomeric G-quadruplexes by our best compounds through FRET melting assays.  相似文献   
82.
ABSTRACT

Lead tetraacetate (LTA) oxidation of α-Phenyl-N-(4-biphenyl)nitrone (8) to give a new ultimate carcinogen, N-acetoxy-N-benzoyl-4-aminobiphenyl (9) which was reacted with deoxyguanosine (dG) at pH 6.9 to give nucleoside derivative, N-(benzoyl)-N-(deoxyguanosin-8-yl)-4-aminobiphenyl (10). Following debenzoylation with sodium carbonate-methanol leads to N-(2′-deoxyguanosin-8-yl)-4-aminobiphenyl (11).  相似文献   
83.
ABSTRACT

Reaction of glycosyl isothiocyanate 1a-c with 3-indolylaminomethyl-ketone hydrochloride(2) yielded glycosylthiourea derivatives 3a-c. Cyclodehydration of 3a-c with acetic anhydride afforded 5-(indol-3-yl)-2-[N-per-O-acetyl-D-glycopyranosyl)amino]thiazoles 4a-c. Deacetylation of 4a-c gave 5-(indol-3-yl)-2-[N-(D-glycopyranosyl) amino]thiazoles 5a-c.  相似文献   
84.
BMS-986120 is a PAR4 antagonist that is being investigated as an antiplatelet agent in phase I clinical trial. An improved synthesis of BMS-986120 has been developed. Based on the novel synthetic approach to BMS-986120, a series of deuterated derivatives of BMS-986120 have been synthesized and biologically evaluated to search for more potent antiplatelet agents. The in vitro antiplatelet assay by turbidimetry demonstrated that PC-2 and PC-6 had IC50 values of 6.30?nM and 6.97?nM, respectively, versus BMS-986120 with an IC50 of 7.80?nM. The result of in vitro metabolic stability study showed that all of the deuterated compounds had similar half-life (T1/2) and intrinsic clearance (Clint) in comparison with BMS-986120. Further probing the metabolic profile of BMS-986120 is worth being conducted.  相似文献   
85.
In searchof the potenttherapeutic agent as an α-glucosidase inhibitor, we have synthesized twenty-five analogs (125) of quinoline-based Schiff bases as an inhibitoragainst α-glucosidase enzyme under positive control acarbose (IC50 = 38.45 ± 0.80 µM). From the activity profile it was foundthat analogs 1, 2, 3, 4, 11, 12 and 20with IC50values 12.40 ± 0.40, 9.40 ± 0.30, 14.10 ± 0.40, 6.20 ± 0.30, 14.40 ± 0.40, 7.40 ± 0.20 and 13.20 ± 0.40 µMrespectively showed most potent inhibition among the series even than standard drug acarbose (IC50 = 38.45 ± 0.80 µM). Here in the present study analog 4 (IC50 = 6.20 ± 0.30 µM) was found with many folds better α-glucosidase inhibitory activity than the reference drug. Eight analogs like 5, 7, 8, 16, 17, 22, 24 and 25 among the whole series displayed less than 50% inhibition. The substituents effects on phenyl ring thereby superficially established through SAR study. Binding interactions of analogs and the active site of ligands proteins were confirmed through molecular docking study. Spectroscopic techniques like 1H NMR, 13C NMR and ESIMS were used for characterization.  相似文献   
86.
Isoniazid-naphthoquinone hybrids were synthesized and evaluated against a susceptible (H37Rv) strain and two isoniazid-resistant strains (INHR1 and INHR2) of Mycobacterium tuberculosis. The antimycobacterial activity of the derivatives was determined based on the resazurin microtiter assay and their cytotoxicity in adhered mouse monocyte macrophage J774.A1 cells (ATCC TIB-67). Of the twenty-two compounds evaluated against the three strains of M. tuberculosis, twenty-one presented some activity against the H37Rv and INHR1 (katG S315T) or INHR2 (inhA C(−5)T) strains. Compounds 1a, 2a, and 8a were effective against the INHR1 strain, and compounds 1a, 1b, 2a, 3a, 5a, 5b and 8a were effective against the INHR2 strain, with MICs in the range of 3.12–6.25 µg/mL. Compounds 1b and 5b were the most active against H37Rv, with MIC of 0.78 µg/mL. Based on the selectivity index, 1b and 5b can be considered safe as a drug candidate compounds. These results demonstrate that quinoidal compounds can be used as promising scaffolds for the development of new anti-TB drugs and hybrids with activity against M. tuberculosis-susceptible and INH-resistant strains.  相似文献   
87.
Two series of moscatilin derivatives were designed, synthesized and evaluated as anti-tumor and anti-angiogenesis agents. Most of these compounds showed moderate-to-obvious cytotoxicity against five cancer cell lines (A549, HepG2, MDA-MB-231, MKN-45, HCT116). Among these cell lines, compounds had obvious effects on HCT116. Especially for 8Ae, the IC50 was low to 0.25 μM. 8Ae can inhibit the viability and induce the apoptosis of HCT116 cells but exhibit no cytotoxic activity in noncancerous NCM460 colon cells. 8Ae can also arrest the G2/M cell cycle in HCT116 cells by inhibiting the α-tubulin expression. Zebrafish bioassay-guided screen showed the 22 moscatilin derivatives had potent anti-angiogenic activities and compound 8Ae had better activities than positive compound. Molecular docking indicated 8Ae interacted with tubulin at the affinity of −7.2 Kcal/mol. In conclusion, compound 8Ae was a potential antitumor and anti-angiogenesis candidate for further development.  相似文献   
88.
In this investigation, a series of 1-phenyl-3-(5-(pyrimidin-4-ylthio)-1,3,4- thiadiazol-2-yl)urea receptor tyrosine kinase inhibitors were synthesized by a simple and efficient structure-based design. Structure-activity relationship (SAR) analysis of these compounds based on cellular assays led to the discovery of a number of compounds that showed potent activity against human chronic myeloid leukemia (CML) cell line K562, but very weak or no cellular toxicity through monitoring the growth kinetics of K562 cell during a period of 72 h using the real-time live-cell imaging. Among these compounds, 1-(5-((6-((3-morpholinopropyl) amino)pyrimidin-4-yl)thio)-1,3,4-thiadiazol-2-yl)-3-(4-(trifluoromethyl)phenyl)urea (7) exhibited the least cellular toxicity and better biological activity in cellular assays (K562, IC50: 0.038 μM). Compound 7 also displayed very good induced-apoptosis effect for human CML cell line K562 and exerted its effect via a significantly reduced protein phosphorylation of PI3K/Akt signal pathway by Human phospho-kinase array analysis. In vitro results indicate that 1-phenyl-3-(5-(pyrimidin-4-ylthio)-1,3,4- thiadiazol-2-yl)urea derivatives are lead molecules for further development as treatment of chronic myeloid leukemia and cancer.  相似文献   
89.
Bromodomain-containing protein 4 (BRD4) is a new therapeutic target for the treatment of diseases including cardiovascular diseases, cancer, inflammation and central nervous system (CNS) disorders. In this study, we introduced the pharmacophore of fibrates to a BRD4 inhibitor, RVX-208, to design dual-active hypolipidemic compounds, and found that some of new analogues showed favorable hypolipidemic activities. Synthetic accessibility towards this class of compounds optimized RVX-208 as well as would supply more thoughts on hypolipidemic drugs.  相似文献   
90.
Searching for CNS active cyclic amines derivatives containing heterocyclic xanthone core we designed and synthesized a set of fourteen novel 2- or 4-methylxanthone substituted by alkyl- or aryl-piperazine moieties. The compounds were evaluated in vivo for their potential antidepressant-like activity (in the forced swim test) and anxiolytic-like activity (four-plate test) and their inhibitory effect against rat 5-HT2 receptor was checked. The pharmacokinetic analysis of active compounds done by a non-compartmental approach have shown a rapid absorption of all studied molecules from intraperitoneal cavity and good penetration the blood-brain barrier after i.p. administration with brain to plasma ratios varied from 2.8 to 31.6. Genotoxicity and biotransformation of active compounds were studied. Compound 19 interactions with major classes of GPCRs, uptake systems and ion channels were tested and results indicated that it binds to 5-HT2A, 5-HT2B receptors and sodium channels.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号