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   426篇
  免费   26篇
  国内免费   1篇
  2021年   5篇
  2019年   3篇
  2018年   3篇
  2016年   6篇
  2015年   8篇
  2014年   13篇
  2013年   18篇
  2012年   18篇
  2011年   12篇
  2010年   19篇
  2009年   18篇
  2008年   29篇
  2007年   20篇
  2006年   21篇
  2005年   18篇
  2004年   16篇
  2003年   23篇
  2002年   16篇
  2001年   15篇
  2000年   10篇
  1999年   13篇
  1998年   15篇
  1997年   10篇
  1996年   9篇
  1995年   4篇
  1994年   9篇
  1993年   4篇
  1992年   7篇
  1991年   4篇
  1990年   11篇
  1988年   4篇
  1987年   4篇
  1986年   3篇
  1985年   5篇
  1984年   3篇
  1983年   7篇
  1982年   3篇
  1980年   3篇
  1977年   2篇
  1975年   3篇
  1974年   5篇
  1972年   2篇
  1971年   3篇
  1970年   4篇
  1969年   3篇
  1968年   2篇
  1967年   2篇
  1966年   3篇
  1965年   2篇
  1894年   2篇
排序方式: 共有453条查询结果,搜索用时 15 毫秒
61.
Trypanosoma cruzi infection triggers a chronic inflammatory process in human host and purinergic system ecto-enzymes play an important role in modulating the inflammatory and immune responses. In this study, it was investigated ecto-nucleoside triphosphate diphosphohydrolase (E-NTPDase; EC 3.6.1.5; CD39) and ecto-adenosine deaminase (E-ADA; EC 3.5.4.4) activities in lymphocytes from patients with indeterminate form of Chagas' disease (IFCD). Twenty-five IFCD patients and 25 healthy subjects (control group) were selected. The peripheral lymphocytes were isolated and E-NTPDase and E-ADA activities were determined. Adenine nucleotides and adenosine levels were determined in serum by HPLC and the E-NTPDase1 expression in lymphocytes by Western blot analysis. E-NTPDase (ATP and ADP as substrates) and E-ADA (adenosine as substrate) activities were decreased in lymphocytes from IFCD patients (P<0.05 and P<0.01, respectively), while the E-NTPDase1 expression presented no changes in these patients. Serum ATP levels showed to be decreased (P<0.05) and both AMP (P<0.01) and adenosine (P<0.001) levels were increased in the IFCD group. The enzymatic alterations observed are in agreement with the immune response against T. cruzi infection in IFCD patients, since the decreased extracellular ATP and the increased adenosine levels trigger a Th2 anti-inflammatory response, which it is associated to adaptation of host to parasite, preventing clinical progress of disease.  相似文献   
62.
Chagas disease (CD) is a chronic and endemic illness caused by the parasite Trypanosoma cruzi. Microvascular disturbances play an important role in the progress of the disease. The purinergic signaling system participates in regulatory functions, such as immunomodulation, neuroprotection, and thromboregulation. This study aimed to investigate the activities of purinergic system ecto-enzymes present on the platelet surface and the platelet aggregation profile from patients with indeterminate form of Chagas disease (IFCD). Thirty patients diagnosed with IFCD and 30 healthy subjects were selected. Ecto-nucleoside triphosphate diphosphohydrolase (E-NTPDase), ecto-nucleotide pyrophosphatase/phosphodiesterase (E-NPP), ecto-5′-nucleotidase (E-5′-NT) and ecto-adenosine deaminase (E-ADA) activities were measured in platelets isolated from these individuals as well as the platelet aggregation. Results demonstrated an increase of 21 % in the E-NPP activity and 30 % in the E-5′-NT activity in IFCD group (P < 0.05); however, a decrease of 34 % in the E-ADA activity was determined in the same group (P < 0.001). A significant decrease of 12.7 % and 12.8 % in the platelet aggregation of IFCD group in two different concentrations of ADP (5 and 10 μM) was observed, respectively (P < 0.05). Increased E-NPP and E-5-NT activities as well as decreased E-ADA activity in platelets of patients with IFCD contributed to decrease platelet aggregation, suggesting that the purinergic system is involved in the thromboregulation process in these patients, since adenosine (the final product of ATP hydrolysis) has cardioprotective and vasodilator effects that prevent the clinical progress of the disease.  相似文献   
63.
目的:研究铼.188标记生物分子在肿瘤治疗中的应用。方法:选取小白鼠作为实验的研究对象,将荷瘤鼠的肉瘤切成小块接种到小白鼠身上,达到试验条件时使用,即将没有明显差异的小白鼠16只随机分为4组,每组4只,注射含有铼一188的药物后分别在不同的时间将其处死,之后取出重要器官进行测量分析,进而得出铼一188的应用效果。结果:瘤内注射的要去在不同时间放射性在瘤内的保持率分别为(90.5±7.7)D%(1h),(92.2±8.6)D%(24h),(88.3±10.9)D%(48h)和(91.5±7.6)D%(72h),在荷瘤鼠内注入生理盐水、非放硫化铼和188Re.硫化铼混悬液,肿瘤质量分别为2885.3±1241.3、2839.9±1965.2和98.4±45.5mg。188Re-硫化铼混悬液在生理盐水、磷酸盐缓冲液和小牛血清中均可稳定72h,而且188W-188Re发生器的应用还可以降低188Re-硫化铼混悬液的价格。随着处死时间的延迟,小鼠肿瘤质量和体积逐渐减小,相临两组比较,后组测定值均明显小于前组,数据经统计学比较具有显著差异(P〈0.05)。结论:188Re-硫化铼混悬液是一种适宜的肿瘤治疗剂。  相似文献   
64.

Background  

In August 2006 a major epidemic of bluetongue virus serotype 8 (BTV8) started off in North-West Europe. In the course of 2007 it became evident that BTV8 had survived the winter in North-West Europe, re-emerged and spread exponentially. Recently, the European Union decided to start vaccination against BTV8. In order to improve the understanding of the epidemiological situation, it was necessary to execute a cross-sectional serological study at the end of the BT vector season. Cattle were the target species for cross-sectional serological studies in Europe at the end of 2006 and 2007. However, there was no information on the BTV8-seroprevalence in sheep and goats.  相似文献   
65.
The design synthesis and SAR of a series of chiral ring-constrained norepinephrine reuptake inhibitors with improved physicochemical properties is described. Typical compounds are potent (IC(50)s<10 nM), selective against the other monoamine transporters, weak CYP2D6 inhibitors (IC(50)s>1 microM) and stable to oxidation by human liver microsomes. In addition, the compounds exhibit a favorable polarity profile.  相似文献   
66.
The design, synthesis and SAR of a series of heterocyclic ring-constrained norepinephrine reuptake inhibitors are described. As racemates, the best compounds compare favorably with atomoxetine (IC(50)'s<10 nM) in potency at the transporter.  相似文献   
67.
ARC is an apoptotic regulatory protein expressed almost exclusively in myogenic cells. It contains a caspase recruitment domain (CARD) through which it has been shown to block the activation of some initiator caspases. Because ARC also blocks caspase-independent events associated with apoptosis, such as hypoxia-induced cytochrome c release, we examined its role in cell death triggered by exposure to hydrogen peroxide (H(2)O(2)) in the myogenic cell line, H9c2. Cell death in this model was caspase-independent and characterized by dose-dependent reduction in ARC expression accompanied by disruption of the mitochondrial membrane potential (Delta psi(m)) and loss of plasma membrane integrity, typical of necrotic cell death. Ectopic expression of ARC prevented both H(2)O(2)-induced mitochondrial dysfunction and cell death without affecting the stress kinase response, suggesting that ARCs protective effects were downstream of early signaling events and not due to quenching of H(2)O(2). ARC was also effective in blocking H(2)O(2)-induced loss of membrane integrity and/or disruption of Delta psi(m) in two human cell lines in which it is not normally expressed. These results demonstrate that, in addition to its ability to block caspase-dependent and -independent events in apoptosis, ARC also prevents necrosis-like cell death via the preservation of mitochondrial function.  相似文献   
68.
The beta-lactamase-inhibiting activity of 6m-ethyl-pyrid-2-yl-ammine palladium-dichloride (Pd 25681) and cis-dichloro-diammine-platinum(II) was studied and compared with the enzyme inhibitory action of potassium clavulanate and the penicillanic acid sulfone CP 45899. Using the nitrocefin test method and the Titertek/Microtiter equipment CP 45899 and potassium clavulanate were the strongest inhibitors of the Bacillus cereus beta-lactamase. Cis-dichloro-diammine-platinum(II) was fourfold less active than the palladium complex PD 25681 in ?quimolar concentration. The following ID50 values were found: CP 45899: 0.0281 microgram; K-clavulanate: 0.1274 microgram; Pd 25681: 3.8603 microgram; cis-dichlorodiammine-platinum(II): 12.5120 microgram/100 microliter.  相似文献   
69.
The proportions of the different bibionid genera are used to estimate the temperature changes between the Late Eocene and the Late Miocene in Western Europe. The genus Plecia is a good indicator of the warm Cenozoic palaeoclimates. We propose a new approach for the estimation of the value of the palaeoclimatic information that could be obtained by actualistic inferences using extinct taxa. Other taxa (i.e. Mastotermitidae) that could appear a priori better palaeoclimatic indicators result to be less sensitive than bibionids to temperature changes. Intraspecific and intrageneric morphological diversity is explored for the genera Bibio, Penthetria and Plecia, showing the difficulties to characterize the fossil bibionid species.  相似文献   
70.
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