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   2477篇
  免费   238篇
  国内免费   158篇
耳鼻咽喉   2篇
儿科学   5篇
妇产科学   9篇
基础医学   143篇
口腔科学   6篇
临床医学   59篇
内科学   40篇
皮肤病学   7篇
神经病学   3篇
特种医学   22篇
外国民族医学   1篇
外科学   45篇
综合类   452篇
预防医学   39篇
眼科学   4篇
药学   1117篇
中国医学   594篇
肿瘤学   325篇
  2024年   10篇
  2023年   53篇
  2022年   46篇
  2021年   71篇
  2020年   83篇
  2019年   79篇
  2018年   97篇
  2017年   110篇
  2016年   80篇
  2015年   110篇
  2014年   181篇
  2013年   206篇
  2012年   161篇
  2011年   208篇
  2010年   123篇
  2009年   107篇
  2008年   132篇
  2007年   128篇
  2006年   106篇
  2005年   96篇
  2004年   74篇
  2003年   67篇
  2002年   58篇
  2001年   73篇
  2000年   52篇
  1999年   50篇
  1998年   41篇
  1997年   31篇
  1996年   37篇
  1995年   22篇
  1994年   17篇
  1993年   23篇
  1992年   21篇
  1991年   17篇
  1990年   17篇
  1989年   13篇
  1988年   17篇
  1987年   9篇
  1986年   8篇
  1985年   4篇
  1984年   8篇
  1983年   2篇
  1982年   3篇
  1981年   3篇
  1980年   5篇
  1979年   4篇
  1978年   3篇
  1975年   2篇
  1974年   3篇
  1973年   1篇
排序方式: 共有2873条查询结果,搜索用时 296 毫秒
1.
林世翼  贾景明  王安华 《中草药》2020,51(1):256-264
狼毒Euphorbiae Ebracteolatae Radix为大戟科(Euphorbiaceae)植物狼毒大戟Euphorbia fischeriana或月腺大戟E.ebracteolata的干燥根,是一种广泛应用,具有广阔开发前景的中药材。狼毒含有多种生物活性成分,其中二萜类化合物是最为重要的一个部分,主要包括松香烷型、巴豆烷型、海松烷型、玫瑰烷型、西松烷型、巨大戟烷型、贝壳杉烷型、阿替斯烷型8种类型,此外还有少量二萜二聚体及其他类型的二萜类化合物。狼毒二萜类化学成分具有显著的抗肿瘤、抗炎、抗菌、抗病毒等药理作用。对狼毒二萜类化学成分及其药理作用进行综述,以期为更好地开发狼毒资源及其临床应用提供参考。  相似文献   
2.
苦碟子抗肿瘤作用的实验性研究   总被引:4,自引:0,他引:4  
目的 研究苦碟子对动物移植性肿瘤的作用。方法 以小鼠移植性肉瘤180(S180)和艾氏腹水瘤(EAC)为模型,观察苦碟子的抗肿瘤作用,并分别计算出抑瘤率和生命延长率。结果 不同剂量的苦碟子对小鼠肉瘤S180的抑制率分别为39.86%,38.14%和35.73%(与对照组相比差异有显著性,P<0.01),苦碟子也能延长荷艾氏腹水瘤(EAC)小鼠的存活期,生命的延长率分别为41.27%、29.79%和17.88%(高剂量组和中等剂量组与对照组相比差异有显著性,P<0.01)。结论 苦碟子在动物体内可能具有抗肿瘤作用,可作为一种有前途的抗肿瘤药物进行研究。  相似文献   
3.
Three acylphloroglucinol derivatives have been isolated from the hexane and acetone extracts of the aerial parts of Hypericum densiflorum Pursch. The compounds were characterized by NMR spectroscopy and mass spectrometry and identified as 4‐geranyloxy‐2,6‐dihydroxybenzophenone (1), 4‐geranyloxy‐1‐(2‐methylpropanoyl)‐ phloroglucinol (2) and 4‐geranyloxy‐1‐(2‐methylbutanoyl)‐phloroglucinol (3). Compounds 1–3 were evaluated for in vitro cell proliferation inhibitory activity against human breast (MCF‐7), lung (NCI H460), CNS (SF‐268), stomach (AGS) and colon (HCT‐116) tumor cell lines; antibacterial activity against methicillin‐resistant Staphylococcus aureus (MRSA); inhibition of cyclooxygenase (COX‐1 and ‐2) enzymes; and antioxidant activity in the lipid peroxidation (LPO) assay. All three compounds showed moderate to strong antitumor, antibacterial, antioxidant and inhibition of COX‐2 activities. Also, this is the first reported occurrence of compound 3 in the Hypericum genus. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   
4.
Ganoderma sinensis has been used widely in Oriental countries for the prevention and treatment of various diseases including cancer. Previous studies have shown that the lipid extract from Ganoderma exhibits direct cytotoxicity against tumor cells. Here, it is reported that the lipid extract from germinating G. sinensis spores, at lower concentrations that have no direct tumoricidal activity, induce potent antitumor immune responses in human monocytes/macrophages. Upon stimulation with the lipid extract, monocytes/macrophages exhibited markedly increased production of proinflammatory cytokines and surface expression of costimulatory molecules. Conditioned medium from stimulated cells effectively suppressed the growth of tumor cells. Apparently, the lipid extract triggered macrophage activation via a mechanism different from that associated with LPS. Moreover, it was observed that the lipid extract could partially re‐establish the antitumor activity of the immunosuppressive tumor‐associated macrophages. These results indicated that in addition to its direct tumoricidal activity, the lipid extract from G. sinensis spores could exert antitumor activity by stimulating the activation of human monocytes/macrophages. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   
5.
研究了十字花科蔬菜提取物6320(主要含异硫氰酸酯)的抗肿瘤活性。体外实验应用MTT法、观察细胞形态、测定细胞生长曲线、流式细胞仪分析细胞凋亡及细胞周期观察提取物6320对不同肿瘤细胞生长的影响。并通过建立小鼠B16实体瘤模型来考察提取物6320的体内抗肿瘤作用。结果表明提取物6320在体内外均可明显抑制肿瘤的生长及增殖,并诱导细胞凋亡,但有可能对机体的免疫系统造成一定的影响。  相似文献   
6.
We evaluated nitric oxide induction in antitumor therapy consisting of anti–CD3 monoclonal antibody (anti–CD3) and interleukin–2 (IL–2), then determined the effect of nitric oxide reduction with L–NG–monomethyl arginine (LNMA) on the therapeutic methods. Female C57BL/6 mice, MCA102 (a non immunogenic, NK–resistant murine fibrosarcoma cell line), and 145–2C11 (hamster anti–murine–CD3 mAb) were utilized in an experimental hepatic metastasis model developed by injecting a tumor cell suspension into the spleen of mice. A marked increase in serum NO2+ NO1 was observed at 19 hours after anti–CD3 (10 μ, IV) and additional IL–2 administrations (40times101 U, twice, If) induced a further increase. The NO2, + NO3- elevation in spot urine in the combination therapy was not suppressed with LNMA at a dose of 100 μg/h but was significantly lowered at 300 μg/h. The efficacy of the anti–CD3 + IL–2 therapy was not diminished by LNMA administration either at 100 μg/h or at 300 μg/h.  相似文献   
7.
4-个甲氧基-2-巯基-N-氧化吡啶钠(4-甲氧基巯氧吡啶钠,SodiumMethoxypyridinethione,SMPT)在试管内0.01mg·L-1可抑制多种传代人癌细胞林,抑制细胞有丝分裂和损害细胞膜相结构,单用对动物移植性肿瘤无效,但明显增强氟脲嘧啶对小鼠S180的抑癌作用。使胸腺和脾脏重量明显减轻,抑制SRBC诱导的小鼠血清溶血素反应,抑制DNCB诱导的豚鼠皮肤迟发型超敏反应,抑制PHA诱导的大鼠3H-TdR参入的淋巴细胞转化。与2-巯基-N-氧化吡啶钠(巯氧吡啶钠,SodiumPyridinethione.SPT)比较,小鼠LD50(ip)增大,而试管内抑瘤的IC50相近。  相似文献   
8.
报道3β,5α,6β三羟基胆烷24酸及其衍生物的合成及对小鼠L1210白血病细胞的体外抗癌活性.实验表明3β,5α,6β三羟基胆烷24酸,3β,5α,6β三羟基胆烷24酸甲酯及3β,6β二乙酰氧基5α羟基胆烷24酸甲酯有较好的抗癌活性  相似文献   
9.
In search of potential drugs for the treatment of estrogen- and androgen-dependent cancer as well as the prophylaxis of metastases, tetralones, tetralins, and dihydronaphthalenes bearing a OCH3 substituent at the benzene nucleus and an imidazol-4-yl, imidazol-1-yl, or 1,2,4-triazol-1-yl substituent in 2-position were synthesized with and without C1-spacer between the rings (compounds 2 – 26 ). The compounds were tested in vitro for inhibition of the three target enzymes P450 arom (human placental microsomes), P450 17 (rat testicular microsomes), and P450 TxA2 (citrated human whole blood). To examine selectivity, some compounds were further tested in vitro for inhibition of P450 18 (bovine adrenal mitochondria), P450 see (bovine adrenal mitochondria) and corticoid formation (aldosterone, corticosterone; ACTH stimulated rat adrenal tissue). In vivo, selected compounds were examined in Sprague Dawley rats regarding P450 TxA2 inhibition, reduction of plasma testosterone concentration, antiuterotrophic activity (inhibition of the uterotrophic activity of androstenedione), reduction of plasma estradiol concentration (pregnant mares' serum gonadotropin-primed rats), and mammary tumor inhibiting activity (dimethylbenzanthracene-induced tumor; pre- and postmenopausal model). In the series of imidazol-4-yl compounds, which represent a novelty in the field of azole inhibitors of steroidogenic P450 enzymes, strong inhibitors of P450 arom and/or P450 17 were found: 7-OCH3-2-(imidazol-4-ylmethylene)-1-tetralone ( 4 ) and 7-OCH3-2-(imidazol-4-ylmethyl)-tetralin ( 12 ) are among the most potent inhibitors of P450 arom in vitro known so far. Compound 4 is a selective inhibitor, whereas 12 shows in addition strong inhibition of P450 17. In contrast to 12 , the 6-OCH3 derivative (compound 11 ) is a selective inhibitor of P450 17, being 50 times more potent than ketoconazole. Some imidazol-1-yl compounds show a marked inhibition of P450 TxA2: 2-(imidazol-1-ylmethyl)-1-tetralone ( 13 ) is a selective inhibitor of P450 TxA2, whereas 7-OCH3-2-(imidazol-1-ylmethyl)-tetralin ( 17 ) as well as 2-(imidazol-1-ylmethyl)-tetralin ( 16 ) and 7-OCH3-2-imidazol-1-yl-3,4-dihydronaphthalene ( 25 ) additionally show strong inhibition of P450 arom and P450 17. Regarding the other steroidogenic P450 enzymes as well as corticosterone formation, the compounds show only little inhibitory activity. Aldosterone formation, however, is inhibited at low concentrations. Nevertheless, 4 and 12 are more selective, i.e. inhibit aldosterone synthesis less than the well known inhibitor of P450 arom fadrozole. The compounds show activity in the aforementioned in vivo tests.  相似文献   
10.
Summary The chromophore-modified derivative of doxorubicin, 4-demethyl-6-0-methyl-doxorubicin, has been tested for antitumor activity in a range of experimental murine tumor systems. In contrast to the inactive 6-0-methyl derivative of daunorubicin, 4-demethyl-6-0-methyl-doxorubicin provided antitumor effects comparable to that of the parent compound. In addition, detailed DNA-interaction studies showed that the doxorubicin derivative retains the ability to bind DNA by the intercalation mechanism. However, the binding affinity was appreciably reduced following structural modification in the anthraquinone chromophore. On the basis of the proposed models of intercalation, these results could be rationalized in terms of steric influence of the bulky methoxy group. The results of this study are in agreement with the correlation already observed between DNA binding and relative antitumor activity of anthracyclines.  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