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   85864篇
  免费   5791篇
  国内免费   2871篇
耳鼻咽喉   396篇
儿科学   1165篇
妇产科学   1099篇
基础医学   15498篇
口腔科学   1277篇
临床医学   4826篇
内科学   12916篇
皮肤病学   1248篇
神经病学   14250篇
特种医学   1126篇
外国民族医学   21篇
外科学   5149篇
综合类   8673篇
现状与发展   11篇
预防医学   2275篇
眼科学   901篇
药学   15151篇
  9篇
中国医学   2049篇
肿瘤学   6486篇
  2024年   156篇
  2023年   1059篇
  2022年   1873篇
  2021年   2637篇
  2020年   2222篇
  2019年   2235篇
  2018年   2349篇
  2017年   2347篇
  2016年   2437篇
  2015年   2757篇
  2014年   4526篇
  2013年   5940篇
  2012年   4465篇
  2011年   5152篇
  2010年   4304篇
  2009年   4431篇
  2008年   4740篇
  2007年   4276篇
  2006年   3753篇
  2005年   3274篇
  2004年   3058篇
  2003年   2790篇
  2002年   2267篇
  2001年   1989篇
  2000年   1805篇
  1999年   1619篇
  1998年   1815篇
  1997年   1724篇
  1996年   1548篇
  1995年   1279篇
  1994年   1197篇
  1993年   1059篇
  1992年   841篇
  1991年   771篇
  1990年   590篇
  1989年   556篇
  1988年   454篇
  1987年   439篇
  1986年   446篇
  1985年   630篇
  1984年   547篇
  1983年   413篇
  1982年   460篇
  1981年   375篇
  1980年   326篇
  1979年   198篇
  1978年   127篇
  1977年   88篇
  1976年   70篇
  1975年   38篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
The spectral response curve (amplitude versus wavelength) of the R2 of the early receptor potential (ERP) was studied in normal, protan, and deutan subjects. The R2 amplitude peaked at 520nm in most normal subjects. The R2 at long wavelengths was smaller than normal in protans and larger than normal in deutans when the maximum amplitudes were normalized to 100% at the peak. The ratio of the R2 amplitude at 460 nm to that at 600 nm clearly differed between protans and deutans. The ERP and the rapid off-response, which is mainly due to the cessation of the late receptor potential, were recorded in the same subjects. The ratio of the sensitivity of the rapid off-response at 500 nm to that at 600 nm was correlated with the ratio of the R2 amplitude at 460 nm to that at 600nm (correlation coefficient, 0.823, p < 0.001). This study, in conjunction with our previous study, indicates that the abnormality is in the outer segments of the cones in protans and deutans.  相似文献   
62.
本文将聚乙二醇(PEG)比浊法和固相酶联免疫法(ELISA)结合,建立了—较灵敏的免疫复合物(IC)直接固相吸附抗原特异性检测法。利用牛清蛋白(BSA)为已知抗原组份的IC模型,分别对IC直接固相吸附的条件和影响因素、方法的灵敏度、重复性等进行了研究。结果发现IC在解离状态下直接固相吸附后的抗原特异性检测灵敏度明显高于未解离者。该法具有简单易行,灵敏度较高、适于临床测定大量血清样品等优点。  相似文献   
63.
The changes in spike activity of single neurons of the compact part of the substantia nigra, evoked by nucleus caudatus stimulation under conditions of long-term registration of the single and multiple, isolated and combined actions of GABA, GABA-amide, glutamine, and ethanolamine-O-sulfate (EOS) were studied in albino rats. Inhibition of poststimulus activity under GABA action was recorded and the inhibitory effect of GABA-amide was revealed. Primary excitatory and subsequent inhibitory effects of glutamine in combination with EOS were shown. The subsequent administration of bacterial melanin, synthesized by a mutant culture of Bacillus thuringiensis (BT-M) evoked a clear-cut and prolonged excitatory reaction during all the combined actions of GABA, GABA-amide, glutamine, and EOS. Preliminary administration of BT-M abolished the inhibitory poststimulus effects of GABA, GABA-amide, and EOS, as well as glutamine-induced excitation.  相似文献   
64.
Background BMS-747158-02 is a novel fluorine 18-labeled pyridazinone derivative designed for cardiac imaging. The uptake and retention mechanisms of F-18 BMS-747158-02 in cardiac myocytes were studied in vitro, and the biodistribution of F-18 BMS-747158-02 was studied in vivo in mice. Methods and Results Fluorine 19 BMS-747158-01 inhibited mitochondrial complex I (MC-I) in bovine heart submitochondrial particles with an IC50 of 16.6±3 nmol/L that was comparable to the reference inhibitors of MC-1, rotenone, pyridaben, and deguelin (IC50 of 18.2±6.7 nmol/L, 19.8±2.6 nmol/L, and 23.1±1.5 nmol/L, respectively). F-18 BMS-747158-02 had high uptake in monolayers of neonatal rat cardiomyocytes (10.3%±0.7% of incubated drug at 60 minutes) that was inhibited by 200 nmol/L of rotenone (91%±2%) and deguelin (89%±3%). In contrast, an inactive pyridaben analog, P-0 (IC50 value>4 μmol/L in MC-1 assay), did not inhibit the binding of F-18 BMS-747158-02 in cardiomyocytes. Uptake and washout kinetics for F-18 BMS-747158-02 in rat cardiomyocytes indicated that the time to half-maximal (t1/2) uptake was very rapid (approximately 35 seconds), and washout t1/2 for efflux of F-18 BMS-747158-02 was greater than 120 minutes. In vivo biodistribution studies in mice showed that F-18 BMS-747158-02 had substatial myocardial uptake (9.5%±0.5% of injected dose per gram) at 60 minutes and heart-to-lung and heart-to-liver ratios of 14.1±2.5 and 8.3±0.5, respectively. Positron emission tomography imaging in the mouse allowed clear cardiac visualization and demonstrated sustained myocardial uptake through 55 minutes. Conclusions F-18 BMS-747158-02 is a novel positron emission tomography cardiac tracer targeting MC-I in cardiomyocytes with rapid uptake and slow washout. These characteristics allow fast and sustained accumulation in the heart.  相似文献   
65.
子宫内膜息肉中雌、孕激素受体的表达   总被引:2,自引:0,他引:2  
目的检测子宫内膜息肉雌激素受体(ER)、孕激素受体(PR)的表达,探索子宫内膜息肉形成的原因及机制。方法子宫内膜息肉48例为观察组,正常子宫内膜36例为对照组,采用免疫组化SP法,行半定量分析,检测ER、PR的表达。结果增殖期的息肉组织中PR表达的评分结果为(2.89±2.16),低于增殖内膜的评分(4.04±1.73),差异有统计学意义(P<0.05);分泌期的内膜息肉中ER表达的评分结果为(3.80±1.64),高于分泌期内膜中的评分(2.64±1.45),差异有统计学意义(P<0.05)。结论增殖期的子宫内膜息肉中PR的表达降低及分泌期的息肉中ER表达增高可能参与了子宫内膜息肉的形成及发展。  相似文献   
66.
王莉 《世界肿瘤杂志》2005,4(3):243-244,F0003
近年来陆续发现了许多新的趋化因子和受体,研究发现趋化因子及其受体参与机体的多种生理和病理过程,并在肿瘤的侵袭转移中通过不同机制发挥着重要作用。本文对其进行简要综述。  相似文献   
67.
Interdigestive human small bowel motility is characterized by the migrating motor complex (MMC). The aims of this study were to: (i) establish the normal range of variables of the nocturnal jejunal MMC and (ii) incorporate these data in a subsequent meta-analysis. Eighty-one recordings were performed by prolonged (24 h) ambulatory manometry in 51 subjects in two centres. Quantitative analysis was undertaken of 419 Phase III and 332 Phase II episodes. Adjusted mean values of seven variables were calculated using a mixed-effects model. Meta-analysis of pooled published data to generate a reliable 95% reference range was also performed. Adjusted mean values and confidence intervals are presented for all seven variables. Intrasubject variances were large in comparison with intersubject. Meta-analysis of 19 studies (356 pooled patients) meeting inclusion criteria produced wide reference ranges. At least five such ranges are useful for the detection of abnormality in the individual. This is the largest study of normal volunteers presented to date, with ranges for many variables produced using appropriate statistical methodology. A model for definition of abnormality has been proposed. We recommend that these data may be used by investigators in this field as a complement to other existing indicators of small bowel dysmotility.  相似文献   
68.
Graft thrombosis is the most common cause of first year graft failure in pediatric renal transplantation. The North American Pediatric Renal Transplant Cooperative Study (NAPRTCS) database was analyzed for cases of graft failure due to thrombosis among patients transplanted from 1998 to 2004. The impact of interleukin-2 (IL-2) receptor antagonists as induction therapy was determined. There were a total of 51 graft failures due to thrombosis among the 2750 reported renal transplants (1.85%) (95% CI (1.39%, 2.41%)). This represents the most common cause of graft loss during the first year post-transplant accounting for 35% of first year losses and 18% of all graft losses. The incidence of thrombosis among patients who received IL-2 receptor antibodies was 1.07% (12/1126) compared to 2.40% (39/1624) among patients who did not (OR 0.44, 95% CI 0.23, 0.84, p = 0.014). Use of IL-2 receptor blockade was the only significant prognostic factor in a multivariate model with previously identified risk factors. Analysis of NAPRTCS data found that the use of IL-2 receptor antibodies as induction therapy is associated with a significantly decreased risk of graft failure due to thrombosis. This provocative finding requires further investigation to determine whether thrombotic failure can be decreased by this therapeutic strategy.  相似文献   
69.
Radiotherapy(RT)is an important ap-proach for treatment of esophageal carcinoma(EC),especially for patients who have missedthe chance of surgical section.The efficacy ofRTis not satisfactory for its1-year,3-year and5-year survival rates being merely50%,20%,and10%respectively(1).Researches in recent years showed thatbetter efficacy can be obtained by combiningRTwith Chinese herbal medicines for EC thatincapable to be resected.Kang ai Injection(康艾注射液,KAI)is a Chinese herbal prep-arati…  相似文献   
70.
We studied 44 cases of Hodgkin's disease for the presence of Epstein-Barr virus (EBV) DNA, its localization and the expression of the EBV receptor on the tumour cells. EBV DNA was found in 52% (16/31) of the Hodgkin's lymphomas using the polymerase chain reaction. With a very sensitive non-radioactive DNA in situ hybridization technique in combination with immunohistochemistry for CD 30 or CD 15 antigens, EBV DNA was localized to Reed-Sternberg cells and its mononuclear variants. The relationship between the presence of EBV DNA and the expression of the EBV-receptor CR2 (CD 21) on Reed-Sternberg cells was studied using the same techniques and two different monoclonal anti-CD 21 antibodies. CR2 could be detected on a substantial number of the Reed-Sternberg cells in EBV DNA positive Hodgkin's lymphomas (9/12; 75%), whereas in EBV negative cases positivity with anti-CD 21 was rare (1/13; 8%). The results indicate that CR2 expression on Reed-Sternberg cells and the presence of EBV DNA sequences are frequently associated in Hodgkin's lymphomas.  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