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   22643篇
  免费   1914篇
  国内免费   1053篇
耳鼻咽喉   215篇
儿科学   270篇
妇产科学   400篇
基础医学   2974篇
口腔科学   338篇
临床医学   2634篇
内科学   4190篇
皮肤病学   510篇
神经病学   1097篇
特种医学   844篇
外国民族医学   5篇
外科学   2970篇
综合类   2252篇
现状与发展   1篇
一般理论   10篇
预防医学   1271篇
眼科学   637篇
药学   2310篇
  15篇
中国医学   830篇
肿瘤学   1837篇
  2024年   40篇
  2023年   242篇
  2022年   655篇
  2021年   953篇
  2020年   632篇
  2019年   683篇
  2018年   700篇
  2017年   646篇
  2016年   688篇
  2015年   1010篇
  2014年   1195篇
  2013年   1207篇
  2012年   1662篇
  2011年   1663篇
  2010年   1208篇
  2009年   1060篇
  2008年   1126篇
  2007年   1138篇
  2006年   1177篇
  2005年   1022篇
  2004年   826篇
  2003年   793篇
  2002年   728篇
  2001年   475篇
  2000年   418篇
  1999年   439篇
  1998年   342篇
  1997年   340篇
  1996年   290篇
  1995年   260篇
  1994年   178篇
  1993年   165篇
  1992年   161篇
  1991年   128篇
  1990年   120篇
  1989年   99篇
  1988年   105篇
  1987年   90篇
  1986年   73篇
  1985年   59篇
  1984年   41篇
  1983年   32篇
  1979年   37篇
  1978年   33篇
  1958年   63篇
  1957年   61篇
  1956年   59篇
  1955年   52篇
  1954年   43篇
  1949年   26篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Deoxycholic acid (DA) caused a dose-related release of histamine (HR) from mast cells of rat peritoneum (RPMC) and mucosal cells of guinea pig rectocolon (RCMC). In both cell populations, DA-induced HR was: (1) accompared by a parallel release of lactate dehydrogenase (LDH), (2) not affected by metabolic inhibitors, (3) dependent on time of incubation, temperature and pH, and affected by Ca++ concentration in RPMC but not in RCMC. DA-induced HR from RCMC may be involved in certain functional disorders of the colon.  相似文献   
32.
BACKGROUND: Masseteric muscle hypertrophy is an uncommon dition represented as a swelling of the masseter muscle. Recent reports have demonstrated the successful use of botulinum in the treatment of masseteric hypertrophy. OBJECTIVE: This study was a prospective trial to evaluate the effectiveness of botulinum toxin type A (Botox) in the treatment of masseteric muscle hypertrophy according to doses of 10, 20, and 30 U. MATERIALS AND METHODS: Twenty-two patients were referred to the dermatologic clinic for the management of masseteric muscle hypertrophy. Ultrasonographic measurements of the thickness of the masseter muscle were performed, and clinical photographs were taken before treatment and 1, 2, 3, 4, 6, and 9 months after the treatment. RESULTS. The median values of percentage reduction of muscle mass were 10.3%, 16.5%, 23.7%, 24.7%, 21.6%, 16.5% in the 10 U group; 11.9%, 18.8%, 24.8%, 27.7%, 26.7%, and 21.8% in the 20 U group; and 12.0%, 19.4%, 25.0%, 27.8%, 37.8%, and 24.1% in the 30 U group. CONCLUSION. The adequate dose of botulinum toxin type A for treatment of masseteric muscle hypertrophy should be above 20 U. The effect of botulinum toxin type A is maintained for at least 9 months as the treatment of masseteric muscle hypertrophy.  相似文献   
33.
We used molecular modeling to examine the binding of 1, 2-dioctanoyl-sn-glycero-3-phosphocholine (a lecithin), 1-octanoyl-sn-glycero-3-phosphocholine (a lysolecithin) and their tetrahedral intermediates in the catalytic site of phospholipase A2 (PLA2). We performed energy minimization on each complex, computed the binding energy, determined the relative binding energy among the complexes and calculated the difference in inter- and intramolecular energies of the components in the complexes. We found that the calculated orientation of the sn-1 ester bond of lysolecithin in the active site is similar to that of the sn-2 ester bond in lecithin, thus permitting PLA2 to hydrolyze lysolecithin using the same mechanism as it uses to hydrolyze lecithin. On the other hand, the binding of lecithin is energetically more favorable by 4.5 kcal/mol than the binding of lysolecithin to the enzyme, and the binding of the lecithin tetrahedral intermediate is also energetically more favorable by 19.7 kcal/mol than the binding of the lysolecithin tetrahedral intermediate to the enzyme, which explains why lecithin is a better substrate than lysolecithin in the catalytic site. These results indicate that the activation energy for the hydrolysis of lysolecithin is higher than that for lecithin, consistent with the observed slower rate for the hydrolysis of lysolecithin.  相似文献   
34.
The effects of lentinan on peripheral blood mononuclear cell (PBMC) expression of IL-2 receptor in patients with chronic hepatitis B in vitro and in vivo were studied. The expression percentage of IL-2 receptor in 44 patients with chronic hepatitis before treatment was 36.74 +/- 7.74, which was lower than healthy subjects, and was 48.92 +/- 3.79 after 2 months treatment of lentinan, which was approximated the normal control. PBMC from 30 patients with chronic hepatitis B were cultured in vitro with or without lentinan. The percentage of expression IL-2 receptor was 12.81 +/- 2.62 without lentinan and was 35.70 +/- 4.87 in the presence of lentinan. The concentration of lentinan stimulating expression of IL-2 receptor was between 0.2 to 200 g.ml-1. The results suggest that lentinan stimulates expression of IL-2 receptor on PBMC, which is associated with the therapeutic effectiveness of lentinan treatment.  相似文献   
35.
A national screening programme for antibody to hepatitis C virus (HCV) in blood donors in Taiwan began in July 1992 using a second-generation immunoassay. To study the impact of this screening on post-transfusion hepatitis in Taiwan, a prospective study on post-transfusion hepatitis, that was started in 1987, was continued. As of June 1994, 245 patients who received a blood transfusion after July 1992 had completed a follow-up period for more than 6 months post-transfusion. Of them, seven (2.8%) recipients developed acute post-transfusion hepatitis. The hepatitis in six cases could not be attributed to infection by hepatitis A, B, C, D, E viruses or cytomegalovirus (CMV) or Epstein-Barr virus (EBV). The remaining patient seroconverted to both IgG and IgM anti-CMV. All seven patients recovered in 6 months without development of chronicity, and the mean peak alanine aminotransferase level was lower compared with that of the cases before anti-HCV screening (i.e. pre-July 1992). These results indicate that the current anti-HCV screening has effectively interrupted HCV transmission through blood transfusion in Taiwan.  相似文献   
36.
白内障超声乳化吸出及囊袋内人工晶体植入术   总被引:1,自引:0,他引:1  
为观察和评价超声乳化白内障吸出术的临床效果、特点、并发病及防治措施,对41 眼白内障施行超声乳化吸出术及小切口(6mm)囊袋内人工晶体植入术,并以同期的白内障患者41眼行现代囊外摘除及后房型人工晶体植入做对照。结果:术后6个月,视力≥1.0者占43.9%>0.8者占70.7≥0.5者占92.7%,均明显高于对照组(P<0.001),术后平均散光为1.04±0.81,1,低于对照组(P<0.01)。白内障超声乳化吸出并囊袋内人工晶体植入术的复明效果优于囊外摘除并后房型人工晶体植入术。  相似文献   
37.
脐血CD34~+细胞体外短期培养扩增研究   总被引:2,自引:0,他引:2       下载免费PDF全文
为寻找更有效的体外扩增脐血CD34 + 细胞的造血细胞因子组合 ,采集健康产妇脐带血 ,用免疫磁珠法分选CD34 + 细胞。采用SCF、FLT3 L、TPO和IL 34种具有早期作用的细胞因子的不同组合进行脐血CD34 + 细胞短期无血清液体培养 ,观察培养前后有核细胞、CD34 + 细胞、CD34 + /CD38- 细胞、CFU GEMM、CFU GM和BFU E数量的变化。结果在 3种不同的细胞因子组合中 ,同时应用SCF、FLT3 L、TPO和IL 34种细胞因子培养 7d的扩增效果最好。突出的发现是在这种条件下CD34 + /CD38- 细胞亚群达到平均 1 97.9倍的扩增效果。提示 :SCF、FLT3 L、TPO和IL 34种细胞因子是脐血CD34 + 细胞体外扩增理想的细胞因子组合  相似文献   
38.
556例遗传咨询病例细胞遗传学分析   总被引:1,自引:0,他引:1  
目的 :分析染色体异常与临床疾病的关系。方法 :应用细胞培养染色体分析技术对 5 5 6例遗传咨询病例进行细胞遗传学检查。结果 :发现 47例染色体结构或数目异常 ,占受检人数的 8.4% ,其中常染色体异常 39例 ,性染色体异常 8例。此外检出 46例 ,XY女性反转综合征 2例。结论 :反复自然流产和不孕不育夫妇及怀疑 Down综合征者应进行染色体检查  相似文献   
39.
40.
OBJECTIVE: To evaluate the short-term therapeutic effect of percutaneous transluminal coronary angioplasty (PTCA) with stent implantation in the treatment of myocardial infarction with severe pump failure. METHODS: The clinical data of 73 patients receiving PTCA and stent implantation for myocardial infarction with severity pump failure were analyzed and grouped according the occurrence of complications, degree of the vascular lesions and the complexity of the surgical procedures. Preoperative and postoperative ventricular ejection fractions (LVEF) were compared in each case. RESULTS: The degree of vascular lesions and surgical complexity were not shown to relate to the occurrence of the complications. Except in cases complicated by chronic renal dysfunction, significant improvement was achieved in the patients 7 d after the operation (P<0.05), regardless of different degrees of vascular lesions and surgical complexity. CONCLUSION: PTCA with stent implantation is effective to improve the short-term cardiac function of patients with myocardial infarction and severe pump failure.  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