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   23215篇
  免费   2419篇
  国内免费   1549篇
耳鼻咽喉   157篇
儿科学   360篇
妇产科学   251篇
基础医学   2923篇
口腔科学   348篇
临床医学   3146篇
内科学   3606篇
皮肤病学   214篇
神经病学   1539篇
特种医学   985篇
外国民族医学   20篇
外科学   2098篇
综合类   3576篇
现状与发展   5篇
一般理论   5篇
预防医学   1408篇
眼科学   810篇
药学   2500篇
  34篇
中国医学   1420篇
肿瘤学   1778篇
  2024年   96篇
  2023年   399篇
  2022年   1073篇
  2021年   1326篇
  2020年   982篇
  2019年   868篇
  2018年   906篇
  2017年   738篇
  2016年   732篇
  2015年   1007篇
  2014年   1392篇
  2013年   1124篇
  2012年   1671篇
  2011年   1742篇
  2010年   1070篇
  2009年   910篇
  2008年   1124篇
  2007年   1097篇
  2006年   1181篇
  2005年   1069篇
  2004年   682篇
  2003年   726篇
  2002年   603篇
  2001年   466篇
  2000年   581篇
  1999年   562篇
  1998年   366篇
  1997年   374篇
  1996年   269篇
  1995年   252篇
  1994年   210篇
  1993年   126篇
  1992年   201篇
  1991年   142篇
  1990年   130篇
  1989年   101篇
  1988年   109篇
  1987年   98篇
  1986年   96篇
  1985年   76篇
  1984年   33篇
  1983年   29篇
  1979年   35篇
  1974年   35篇
  1973年   27篇
  1970年   23篇
  1969年   31篇
  1968年   23篇
  1967年   29篇
  1966年   30篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
目的 研究应用行为干预治疗及生物反馈治疗对老年高血压患者降压药物的影响。方法 在应用降压药物的基础上,增加行为干预及生物馈治疗,观察综合性行为干预措施对降压疗效的影响。结果 增加行为干预及生物反馈治疗后,降压和情绪障碍矫正的效果比单用药物明显改善。结论 老年高血压患者给予综合性行为干预措施可增加降压药物的疗效。  相似文献   
52.
目的 分析临床急性感染性疾病所致肝功能损害的特点及其恢复时间。方法 对 135例急性感染性疾病患者入院肝功能指标进行分析 ,观察治疗第 2周及第 4周时患者异常肝功能指标恢复情况。结果 除 6例死亡外 ,其余患者异常肝功能指标升高多在正常值上限 3倍以内 ,治疗第 4周异常肝功能指标治愈率分别为 AL T92 .4%、AST91.6 %、GGT75 .6 %、AL P91.3%、 SB10 0 %、 SB’ 10 0 %和 TBA 85 .7% ,HBs Ag ( )携带者与 HBs Ag (- )者治疗第 4周上述指标治愈率无显著差异。第 4周时 GGT仍升高者恢复缓慢或不易恢复正常。结论 急性感染性疾病致肝功能损害多呈轻度及一过性升高 ;HBs Ag ( )携带者肝脏应急储备及修复功能较正常人无明显下降 ;GGT恢复缓慢或不易恢复正常者可能留有持久性的肝内毛细胆管损伤  相似文献   
53.
通过对低仟伏、中仟伏、高仟伏摄影胸部正位片各500 例的照片等级、胸部细微结构及重要解剖结构的显示、清晰度、对比度及层次的对比研究,得出胸部中仟伏摄影提高了照片有用信息量,照片对比度,清晰度较好,照片质量较高,认为胸部中仟伏摄影应作为常规检查方法推广使用。  相似文献   
54.
Gastrodia elata is an achlorophyllous and fully mycoheterotrophic orchid which obtains carbon and other nutrients from Armillaria species in its life cycle. Many researchers suggested that plant hormones, as signing molecules, play a central role in the plant–fungi interaction. In the process of Armillaria gallica 012 m cultivation, both exogenous indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) distinctly stimulated the growth of mycelia in solid media. The differential expression genes (DEGs) of A. gallica 012 m with IAA versus blank control (BK) and IBA versus BK were investigated. The results showed that more than 80% of DEGs of the IAA group were coincident with the DEGs of the IBA group, and more than half of upregulated DEGs and most of the downregulated DEGs of the IAA group coincided with those DEGs of the IBA group. Above research implied that A. gallica 012 m could perceive IAA and IBA, and possess similar responses and signaling pathways to IAA and IBA. The overlapping differential genes of the IAA group and IBA group were analyzed by GO term, and the results showed that several DEGs identified were related to biological processes including positive regulation of the biological process and biological process. The downregulated NmrA-like and FKBP_C genes might be benefit to the growth of mycelia. Those results can explain that exiguous IAA and IBA improved the growth of A. gallica to some extent. We speculate that IAA and IBA are signaling molecules, and regulate the expression of growth-related genes of A. gallica 012 m by the same signaling pathway.  相似文献   
55.
目的 对抗辐射菌D.radioudurans 的DNA结合蛋白(DBP) 进行N- 末端氨基酸(AA) 序列分析,探讨其抗辐射分子学组成的特性。方法 采用地高辛(DIG) 标记染色体DNA 作为探针,SouthWestern 印迹法检测DBP,在N- 端AA 自动序列仪上分析AA序列。结果 野生型抗辐射菌存有8 种DBP的特性蛋白(分子量分别为122、93、33、29、16、15、14 和12kd);AA 序列分析发现其中93kd 和33kd 可能为新的蛋白质;两种新DBP 的表达水平随不同培养基和培养时间而变化。结论 抗辐射菌的DBP,尤其是93kd 和33kd 的DBP与其辐射耐受性可能有密切关系  相似文献   
56.
57.
Prevention of stroke in urban China: a community-based intervention trial   总被引:26,自引:0,他引:26  
BACKGROUND AND PURPOSE: Stroke has been the second leading cause of death in large cities in China since the 1980s. Meanwhile, the prevalences of hypertension and smoking have steadily increased over the last 2 decades. Therefore, a community-based intervention trial was initiated in 7 Chinese cities in 1987. The overall goal of the study was to evaluate the effectiveness of an intervention aimed at reducing multiple risk factors for stroke. The primary study objective was to reduce the incidence of stroke by 25% over 3.5 years of intervention. METHODS: In May 1987 in each of 7 the cities, 2 geographically separated communities with a registered population of about 10 000 each were selected as either intervention or control communities. In each community, a cohort containing about 2700 subjects (>/=35 years old) free of stroke was sampled, and a survey was administered to obtain baseline data and screen the eligible subjects for intervention. In each city, a program of treatment for hypertension, heart disease, and diabetes was instituted in the intervention cohort (n approximately 2700) and health education was provided to the full intervention community (n approximately 10 000). A follow-up survey was conducted in 1990. Comparisons of intervention and control cohorts in each city were pooled to yield a single summary. RESULTS: A total of 18 786 subjects were recruited to the intervention cohort and 18 876 to the control cohort from 7 cities. After 3.5 years, 174 new stroke cases had occurred in the intervention cohort and 253 in the control cohort. The 3.5-year cumulative incidence of total stroke was significantly lower in the intervention cohort than the control cohort (0.93% versus 1.34%; RR=0.69; 95% CI, 0.57 to 0.84). The incidence rates of nonfatal and fatal stroke, as well as ischemic and hemorrhagic stroke, were significantly lower in the intervention cohort than the control cohort. The prevalence of hypertension increased by 4.3% in the intervention cohort and by 7.8% in the control cohort. The average systolic and diastolic blood pressures increased more in the control cohort than in the intervention cohort. Among hypertensive individuals in the intervention cohort, awareness of hypertension increased by 6.7% and the percentage of hypertensives who regularly took antihypertensive medication increased 13.2%. All of these indices became worse in the control cohort. The prevalence of heart diseases and diabetes increased significantly in the both cohorts (P<0.01). The prevalence of consumption of alcohol increased slightly, and that of smoking remained constant in both cohorts. CONCLUSIONS: A community-based intervention for stroke reduction is feasible and effective in the cities of China. The reduction, due to the intervention, in the incidence of stroke in the intervention cohort was statistically significant after 3.5 years of intervention. The sharp reduction in the incidence of stroke may be due to the interventions having blunted the expected increase in hypertension that accompanies aging as well as to better and earlier treatment of hypertension, particularly borderline hypertension. Applied health education to all the residents of the community may have prevented some normotensive individuals from developing hypertension and improved overall health awareness and knowledge.  相似文献   
58.
INTRODUCTION: Large population studies of adult patients suggest an incidence of cytomegalovirus (CMV) retinitis as high as 19% to 20% as a late complication of adult HIV infection. We conducted this prospective study of a large cohort of HIV-infected children to determine the incidence of CMV retinitis in HIV-infected children. METHODS: From January 1984 to August 1997, 173 HIV-infected children were followed up for an average of 55.3 months (13-164 months). The patients were seen in the Department of Pediatrics at least once every 6 months. Ophthalmologic examinations were initiated when a patient's CD4 count dropped below 50 or sooner if required for ophthalmologic or other indications. Ophthalmologic examination was then repeated every 6 months. RESULTS: A total of 116 (67%) of 173 patients underwent ophthalmologic examination. Four (3.4%) of 116 patients had CMV retinitis at a mean time of 17.3 months (8-38 months) after their CD4 counts dropped below 20. None of the 4 patients with CMV retinitis had subjective visual complaints despite advanced retinitis. Three patients had bilateral and 1 patient had unilateral CMV retinitis. CONCLUSIONS: CMV retinitis occurred infrequently in HIV-infected pediatric patients and was diagnosed only in patients with a CD4 count below 20. Routine ophthalmologic screening examinations may not be necessary in pediatric patients until the CD4 count is below 20. Because children may not complain of decreased vision, at-risk children should undergo frequent ophthalmologic examination.  相似文献   
59.
Regulation of complement activation by C-reactive protein.   总被引:22,自引:0,他引:22  
C-reactive protein (CRP) is an acute-phase serum protein and a mediator of innate immunity. CRP binds to microbial polysaccharides and to ligands exposed on damaged cells. Binding of CRP to these substrates activates the classical complement pathway leading to their uptake by phagocytic cells. Complement activation by CRP is restricted to C1, C4, C2 and C3 with little consumption of C5-9. Surface bound CRP reduces deposition of and generation of C5b-9 by the alternative pathway and deposition of C3b and lysis by the lectin pathway. These activities of CRP are the result of recruitment of factor H resulting in regulation of C3b on bacteria or erythrocytes. Evidence is presented for direct binding of H to CRP. H binding to CRP or C3b immobilized on microtiter wells was demonstrated by ELISA. Attachment of CRP to a surface was required for H binding. H binding to CRP was not inhibited by EDTA or phosphocholine, which inhibit ligand binding, but was inhibited by a 13 amino acid CRP peptide. The peptide sequence was identical to the region of CRP that showed the best alignment to H binding peptides from Streptococcus pyogenes (M6) and Neisseria gonorrhoeae (Por1A). The results suggest that CRP bound to a surface provides secondary binding sites for H resulting in greater regulation of alternative pathway amplification and C5 convertases. Complement activation by CRP may help limit the inflammatory response by providing opsonization with minimal generation of C5a and C5b-9.  相似文献   
60.
Steady state pharmacokinetics of morphine (M), morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G) were investigated in 6 patients with intractable cancer pain administered orally with MST (Mundipharma, Limburg, Germany) and, subsequently, rectally with MSR to make a judgment whether orally administered morphine can be replaced by rectally administered morphine. The parent drug and glucuronide metabolites were measured simultaneously using high-performance liquid chromatography (HPLC) and native fluorescence detection. The mean morphine area under the curve (AUC) value (0-8 h) was smaller (434.3 +/- 170.2 nmolL(-1)h) in the oral administration than in the rectal administration (574.8 +/- 285.0 nmolL(-1)h) (p < 0.05). The rectal administration resulted in less production of M3G and M6G. There were no significant differences in the mean steady state concentrations (C(ss)) of morphine, M3G, and M6G between the oral and rectal administrations (p > 0.05). The median AUC ratio--M3G/M and M6G/M, 12.58 and 1.85--following MSR rectal administration was smaller than following MST oral administration in 6 patients (19.97 and 2.59; p < 0.05), whereas the median AUC ratio M3G/M6G in the rectal dosing was 6.24 (range 5.2-7.6) was almost the same as the median ratio M3G/M6G in the oral dosing was 6.49 (range 5.8-8.5; p > 0.1). Four of the 6 patients had a greater Cmax of M3G and M6G after oral administration than after rectal administration. The same 4 had lower fluctuation rates for morphine, M3G (p < 0.05), and M6G (p < 0.05) after rectal administration. Therefore, during chronic morphine treatment, it still seems difficult to decide whether oral administration can be replaced by rectal administration.  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