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   11908篇
  免费   686篇
  国内免费   237篇
耳鼻咽喉   91篇
儿科学   528篇
妇产科学   167篇
基础医学   3287篇
口腔科学   201篇
临床医学   637篇
内科学   1705篇
皮肤病学   223篇
神经病学   1090篇
特种医学   133篇
外科学   597篇
综合类   1273篇
预防医学   567篇
眼科学   134篇
药学   1447篇
  1篇
中国医学   261篇
肿瘤学   489篇
  2023年   117篇
  2022年   189篇
  2021年   308篇
  2020年   293篇
  2019年   268篇
  2018年   293篇
  2017年   333篇
  2016年   323篇
  2015年   325篇
  2014年   614篇
  2013年   712篇
  2012年   531篇
  2011年   667篇
  2010年   480篇
  2009年   526篇
  2008年   581篇
  2007年   571篇
  2006年   529篇
  2005年   469篇
  2004年   420篇
  2003年   374篇
  2002年   264篇
  2001年   230篇
  2000年   231篇
  1999年   231篇
  1998年   221篇
  1997年   210篇
  1996年   210篇
  1995年   231篇
  1994年   192篇
  1993年   173篇
  1992年   152篇
  1991年   129篇
  1990年   119篇
  1989年   110篇
  1988年   117篇
  1987年   97篇
  1986年   81篇
  1985年   171篇
  1984年   122篇
  1983年   107篇
  1982年   98篇
  1981年   74篇
  1980年   84篇
  1979年   72篇
  1978年   34篇
  1977年   29篇
  1976年   25篇
  1975年   22篇
  1973年   19篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Ca(++)-dependent monoclonal antibody specific to gamma-carboxyglutamic acid (Gla) domain of protein C was produced. It did not cross-react to the other vitamin K-dependent plasma proteins but to protein C of the other species. Using this monoclonal antibody, PC01, rabbit (170 micrograms), rat (60 micrograms) and mouse (40 micrograms) protein Cs were isolated from 100 ml of their plasma by affinity chromatography. All of these protein Cs were two chain form linked by disulfide bond as well as human protein C and activated by thrombin-thrombomodulin complex. Rat and mouse protein Cs showed similar characters to human protein C. On the other hand rabbit protein C had different M(r) of heavy and light chains and showed lower anticoagulant activity compared with human protein C.  相似文献   
52.
李梅  蔡方成 《重庆医学》2003,32(4):406-408
目的:研究自由基在幼年鼠内毒素性脑水肿发病机理中的作用。方法:65只幼鼠,随机分为对照组(C组),单纯内毒素组(LPS组),静注免疫球蛋白治疗组(IVIG组)。于处理后2、6、12、24h(每时间点6-9只)取脑组织,用常规生化方法测定脑组织匀浆中丙二醛(MDA)、总巯基(TSH)和非蛋白巯基(NPSH)含量。结果:LPS组脑含水量、EB含量及MDA含量均明显高于C组,而TSH和NPSH含量明显低于C组(P<0.05或P<0.01);IVIG组脑含水量、EB含量及MDA含量与LPS组相比则有明显降低,以6h更明显(P<0.05或P<0.01),而TSH和NPSH含量分别在各时间点上比LPS组明显增高,但IVIG对NPSH含量影响与LPS组相比无显著差异(P>0.05),且各时间点与C组相比仍低(P<0.05或P<0.01)。结论:自由基参与了幼年鼠内毒素性脑水肿的发生发展,初步证实IVIG通过影响自由基,具有治疗幼年鼠内毒素性脑水肿的作用。  相似文献   
53.
Elevated serum immunoglobulin E (IgE) and increased prevalence of atopy is reported in patients infected with human immunodeficiency virus (HIV). The elevated serum IgE may be attributed to polyclonal stimulation of B cells or IgE production against allergens, viruses, fungi and bacteria. This study investigates the prevalence of atopy in perinatally HIV-infected children, and the relationships between serum IgE (and other serum immunoglobulins) with atopy, CD4+ cell count and HIV-disease stage. Serum immunoglobulin levels, epicutaneous skin test for common aeroallergens, clinical Centers for Disease Control and Prevention (CDC) classification, CD4+ cell counts and allergy history were extracted from the charts of perinatally HIV-infected children on highly active antiretroviral therapy. The prevalence of atopy (52%) and the pattern of aeroallergen sensitivity were comparable with the US pediatric population. Serum IgE levels did not correlate with clinical disease stage. However, in non-atopic patients, serum IgE levels increased with disease progression (p = 0.02). There was an inverse relationship between the prevalence of elevated serum IgE levels and atopy with progression of disease (p = 0.019). Serum IgE did not correlate with atopy, CD4+ cell count, or duration of HIV infection or levels of serum immunoglobulins. This is the first study to show no increased prevalence of atopy in perinatally HIV-infected children compared with the general population. In advanced stages of HIV, elevated serum IgE may be specific for antigens other than those known as allergens.  相似文献   
54.
葛根对小白鼠免疫功能的影响   总被引:8,自引:1,他引:7  
从免疫学方面探讨中药葛根的强身健体作用。方法 :用 10 0 %葛根水浸出液定期给小鼠灌胃 ,然后检测小鼠抗体产生能力、淋巴细胞转化率、巨噬细胞吞噬的功能。结果 :用药组小白鼠以上免疫学指标均有显著增强作用 ,与对照组相比有非常显著性差异 (P <0 .0 1)。未见有副作用。结论 :口服葛根可明显增强机体免疫功能。  相似文献   
55.
目的 :观察慢性氟中毒对小鼠切牙胚内釉上皮表达 TGF- beta1的影响 ,探讨TGF- beta1在氟牙症发生机制中的作用。方法 :给小鼠分别喂以含 0、5 0、1 0 0 ppm Na F的饮水 ,6周后免疫组化观察结果。结果 :图像分析显示加氟组 TGF- beta1的表达水平低于空白组。结论 :氟可能通过抑制 TGF- beta1的表达干扰内釉上皮的分化和基质分泌 ,导致氟牙症的发生。  相似文献   
56.
秦焱  胡美浩 《免疫学杂志》2004,20(5):393-396
目的 将人乳头瘤病毒16型(Human papillomavirus type 16,HPV-16)的晚期表达蛋白E7上的抗原24肽(从第38位氨基酸到第61位氨基6病毒感染防治酸)与人免疫球蛋白G的重链恒定区融合表达,并以此融合蛋白作为抗原,可能为HPV-1提供免疫治疗方法。方法 利用PCR方法分别扩增HPV-16 E7(38-61)24肽的DNA片段和人免疫球蛋白G的重链恒定区DNA片段,并构建到pEV21a表达载体上,转化入E.coli中表达,利用SDS-聚丙烯酰胺凝胶电泳(SDS-PAGE)和蛋白质免疫印迹(Western-blotting)的方法对表达结果进行鉴定。结果 构建的表达载体HPV16E7e/hIgGHCCR-pET21a经酶切鉴定和测序显示序列正确;通过SDS-PAGE和Western-blotting的鉴定,重组融合蛋白Mr约40000,表达量可占菌体蛋白的20%左右。结论 成功构建HPV16-E7的抗原多肽片段和人免疫球蛋白G的重链恒定区的融合蛋白,并可在E.coli中高效表达。  相似文献   
57.
An in vitro method for obtaining pressure/volume curves from the lungs of small animals is described. The excised lungs were inflated and deflated with saline or air by a motor-driven syringe controlled by a microcomputer. The computer was programmed to display the curves in real time, correcting when necessary for the compressibility of air in the system. Volume compliance (K=dV/dP×1/V) was calculated by differentiating a polynomial fitted to the measured pressure/volume points. Repeatable curves were obtained from mice aged 24h (body weight 1·3±0·14g (SD), residual lung volume 8·43±1·5 μl (SD). A nonlinear decrease in differential compliance (K=dV/dP×1/V) with increasing strain was observed while the ratio Ksaline/Kair increased from 2·5 to 10 over the range of strains investigated (ε=1–5). The relative surface tension (calculated from the difference between the pressures required to inflate the air and saline-filled organs to a given volume) increased exponentially with increasing volume. We conclude that it is now possible to obtain reproducible pressure/volume curves for lungs with a residual volume of less than 10 μl, from animals weighing approximately 1·5 g and, from these curves, estimate airway compliance and surface tension.  相似文献   
58.
Asymmetry in brain modulation of the immune system has been previously described. In mice, paw preference has been shown to be associated with immune reactivity but the mechanisms involved in such an association are not yet known. The autonomic nervous system and the neuroendocrine system are considered as major candidates for neural influences on the immune system. In the present study, the activity of the hypothalamic-pituitary-adrenal (HPA) axis of adult female mice selected for paw preference (left-handers vs. right-handers) was assessed by measuring both adrenocorticotropic hormone (ACTH) and corticosterone plasma levels, as well as the in vitro responses of hypothalamus and adrenocortical cells to various hormone releasing stimuli. The results reported here showed no difference in the activity of the HPA axis between left- and right-handed mice, suggesting that this neuroendocrine axis is not implicated in the association between functional brain asymmetry and immune reactivity. However, our results do not exclude the possibility that the HPA axis could play a role in such an association under other circumstances, such as during development or stressful situations.  相似文献   
59.
对150例IgA肾病的肾活检标本进行了光镜及透射电镜的形态学观察,[其组织学改变由轻微病变至弥漫性系膜增殖,根据病变的严重程度作者将其分为6个亚型。系膜基质的增生为其突出的超微结构改变,常显示为局灶节段性、球性系膜细胞增殖和显著的系膜基质的增加。电子致密沉着多见于系膜基质及内皮细胞下,这些沉着物的多少与病变的严重程度未见有肯定的联系。  相似文献   
60.
BALB/c mice were bilaterally implanted with bipolar electrodes either in anterodorsal (ADH) or posteroventral hippocampus (PVH) in order to compare the effects of postsession electrical stimulation on memory processes. For each experiment, 30 s after the end of the first session, the animals were stimulated during 80 s. For both hippocampal regions, the stimulation intensity was half of the afterdischarge threshold value. Control groups were naive, ADH and PVH implanted non-stimulated animals. Different appetitive and aversive tasks were used. Subseizure stimulation never created a deficit. Depending on the region of the hippocampus stimulated and on the learning task, a retention enhancement was eventually observed. These data are in agreement with the involvement of hippocampus in initial stages of memory consolidation. Further, the subseizure stimulation permitted a functional dissociation between the two hippocampal regions. Both regions seemed involved in the integration of information, but the anterodorsal part would be rather related to behavioral inhibition, while the posteroventral part would have the capacity to induce an arousal state allowing behavioral flexibility.  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