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   1460篇
  免费   54篇
  国内免费   10篇
耳鼻咽喉   77篇
儿科学   24篇
妇产科学   16篇
基础医学   195篇
口腔科学   17篇
临床医学   108篇
内科学   329篇
皮肤病学   34篇
神经病学   70篇
特种医学   65篇
外科学   268篇
综合类   7篇
预防医学   28篇
眼科学   27篇
药学   93篇
中国医学   6篇
肿瘤学   160篇
  2023年   7篇
  2022年   13篇
  2021年   21篇
  2020年   16篇
  2019年   24篇
  2018年   25篇
  2017年   18篇
  2016年   17篇
  2015年   33篇
  2014年   46篇
  2013年   45篇
  2012年   95篇
  2011年   115篇
  2010年   57篇
  2009年   42篇
  2008年   80篇
  2007年   89篇
  2006年   90篇
  2005年   69篇
  2004年   103篇
  2003年   103篇
  2002年   86篇
  2001年   33篇
  2000年   17篇
  1999年   22篇
  1998年   32篇
  1997年   15篇
  1996年   24篇
  1995年   13篇
  1994年   9篇
  1993年   11篇
  1992年   23篇
  1991年   13篇
  1990年   20篇
  1989年   11篇
  1988年   15篇
  1987年   9篇
  1986年   10篇
  1985年   3篇
  1984年   10篇
  1983年   5篇
  1982年   6篇
  1981年   10篇
  1980年   5篇
  1979年   5篇
  1976年   2篇
  1975年   2篇
  1971年   1篇
  1970年   1篇
  1967年   1篇
排序方式: 共有1524条查询结果,搜索用时 0 毫秒
21.
The carcinoembryonic antigen (CEA) in the cyst fluid of ovarian mucinous and serous tumors was investigated. The molecular weight and antigenicity of the CEA from both ovarian tumors were very similar to those of colon cancer CEA as determined by SDS electrophoresis and double immunodiffusion on agar plates. In the cyst fluid of ovarian mucinous tumors, the amount of CEA was generally high and CEA of molecular weight (MW) 200,000 was increased. In contrast, in the cyst fluid of ovarian serous tumors, the CEA amount was low and CEA variants of MW 370,000 and 180,000 were present in addition to the main CEA of MW 200,000. Immunohistochemically, CEA was stained mainly in the intestinal type epithelium of ovarian mucinous tumors, and the CEA revealed a tendency to be stained more frequently and strongly with increasing degree of tumor malignancy. Thus, ovarian mucinous tumors (especially the intestinal type epithelium) produced large amounts of CEA which closely resembled colon cancer CEA, whereas ovarian serous tumors produced small amounts of CEA, including some CEA variants. In the study of ovarian epithelial tumors, CEA may be useful as a marker for the malignant transformation of ovarian mucinous tumors.  相似文献   
22.
Antiherpetic activities of sulfated polysaccharides from green algae   总被引:3,自引:0,他引:3  
In order to evaluate the potency of novel antiviral drugs, 11 natural sulfated polysaccharides (SPs) from 10 green algae ( Enteromorpha compressa, Monostroma nitidum, Caulerpa brachypus, C. okamurai, C. scapelliformis, Chaetomorpha crassa, C. spiralis, Codium adhaerens, C. fragille, and C. latum) and 4 synthetic sulfated xylans (SXs) prepared from the beta-(1,3)-xylan of C. brachypus, were assayed for anti-Herpes simplex virus type 1 (HSV-1) activity. Except for one from E. compressa, all SPs showed potent anti-HSV-1 activities with 50 % inhibitory concentrations (IC (50)) of 0.38 - 8.5 microg/mL, while having low cytotoxicities with 50 % inhibitory concentrations of >2900 microg/mL. Anti-HSV-1 activities of SXs were dependent on their degrees of sulfation. To delineate the drug-sensitive phase, 4 polysaccharides, which showed potent anti-HSV-1 activities, were applied to time-of-addition experiments. Among the polysaccharides tested, 3 polysaccharides (SX4, SP4 from C. brachypus, and SP11 from C. latum) showed strong anti-HSV-1 activities with IC (50) of 6.0, 7.5, and 6.9 microg/mL, respectively, even when added to the medium 8 h post-infection. These experiments demonstrated that some sulfated polysaccharides not only inhibited the early stages of HSV-1 replication, such as virus binding to and penetration into host cells, but also interfered with late steps of virus replication. These results revealed that some sulfated polysaccharides from green algae should be promising candidates of antiviral agents which might act on different stages in the virus replication cycle.  相似文献   
23.
Evaluation of extensive lymph node dissection for carcinoma of the stomach   总被引:10,自引:0,他引:10  
We compared the results of curative resection for carcinoma of the stomach in 254 patients who underwent simple resection (SR) and 454 patients who underwent extensive regional lymph node dissection (ELD). The 5-year survival rates of the 2 procedures were significantly different in carcinoma involving the serosa of the stomach; it was 45% in the ELD group and 18% in the SR group (p<0.001). In patients with regional lymph node metastasis we obtained a 5-year survival rates of 39% and 18% by ELD and SR, respectively (p<0.001). The incidence of metastasis to the secondary lymph nodes, removable only by ELD, was higher in cases with carcinomatous invasion of the deeper layers of the gastric wall, and this may have been the reason why ELD proved to be more effective than SR. ELD is discussed in relation to the site of the primary carcinoma and the extent of lymph node metastasis.  相似文献   
24.
We evaluated the acute toxicities of the main degradation products of pyridine triphenylborane (PTPB), namely, diphenylborane hydroxide (DPB), phenylborane dihydroxide (MPB), phenol, and biphenyl, to the alga Skeletonema costatum, the crustacean Tigriopus japonicus, and two teleosts, the red sea bream Pagrus major and the mummichog Fundulus heteroclitus. DPB was the most toxic of the degradation products to all four organisms. The acute toxicity values of DPB for S. costatum, T. japonicus, red sea bream, and mummichog were 55, 70, 100, and 200–310 μg/L, respectively. The degradation products were less toxic than PTPB to S. costatum and T. japonicus; however, the toxicities of DPB and PTPB to the fish species were similar. We also examined changes in the inhibition of growth rate of S. costatum as well as the percentage of immobilization of T. japonicus as end points of toxicity of PTPB after irradiation of PTPB with 432 ± 45 W/m2 of 290–700 nm wavelength light. After 7 days of irradiation with this light, the concentration of PTPB in the test solutions decreased markedly. A decrease in toxic effects closely coincided with the decrease in the concentration of PTPB caused by the irradiation. PTPB probably accounted for most of the toxicity in the irradiation test solutions. Because the concentrations of PTPB that were acutely toxic to S. costatum and T. japonicus were <10 % of the corresponding concentrations of its degradation products, PTPB probably accounted for most of the toxicity in the irradiation test solutions.  相似文献   
25.
26.
A 28-day in vivo treatment trial to evaluate the efficacy of pyrimethamine/sulfadoxine (Fansidar, PS) was conducted in 21 Lao patients with uncomplicated Plasmodium falciparum malaria. Sixteen patients (76%) were completely cured with PS without any reappearance of asexual stage parasitemia during the follow-up examination. On the other hand, 5 patients (24%) failed to respond to this trial medication, resulting in recrudescence of asexual stage P. falciparum malaria. PS resistance resulted in higher prevalence of post-treatment gametocytemia, 25% gametocyte carriers among PS sensitive cases versus 75% of the resistant cases. These findings suggest that although the level of PS resistance is still valid for treatment of malaria in the study area of Lao PDR, post-treatment induction of gametocytemia among resistant cases may result an increase in transmission rate of PS resistant falciparum malaria.  相似文献   
27.
Measles virus was isolated from the middle ear fluid (MEF) of two infant cases of acute otitis media (AOM) associated with measles. This is the first report on the isolation of measles virus from the MEF in patients with AOM, and possibility of the measles virus as a causative agent of AOM was suggested.  相似文献   
28.
We describe a gastric carcinoma cell line that has been maintained in vitro for more than 10 years and retains the capacity to produce a large amount of alpha-fetoprotein. This cell line was isolated from a metastatic lymph node of a 63-year-old male patient with advanced gastric carcinoma (T2N3P0H0M0) who showed high serum levels of alpha-fetoprotein. The primary tumor was moderately differentiated tubular adenocarcinoma and the lymph node was poorly differentiated adenocarcinoma without any particular pattern. The cultured cells grew as densely packed islet-like colonies with small polygonal cells. Electron microscopy revealed cells abundant in cytoplasmic organelles, with some cellular attachments being tight with junctional complexes and some being loose across intercellular spaces. The free cell surface had microvilli. The population doubling-time was 152 h at passage 58. Chromosomal analysis revealed the modal number to be 77, with numerous karyotype abnormalities. The tumorigenicity of the cultured cells in athymic nude mice was positive only when they were subcutaneously transplanted beneath a plastic plate, but when the cells were transplanted subcutaneously or administered by intrasplenic injection in intact or weakly irradiated nude mice, no tumorigenicty was shown. The cell line produced tumor-associated antigens, such as alpha-fetoprotein, carcinoembryonic antigen, and tissue polypeptide antigen. This cell line may be useful for comparative studies of different types of gastric carcinoma and alpha-fetoproteins of different origins.  相似文献   
29.
Perlman syndrome is a rare, autosomal recessive overgrowth disorder. Recently, the deletion of exon 9 and other mutations of the DIS3L2 gene have been reported in patients; however, the mechanism behind this deletion is still unknown. We report the homozygous deletion of exon 9 of DIS3L2 in a Japanese patient with Perlman syndrome. We identified the deletion junction, and implicate a non-allelic homologous recombination (NAHR) between two LINE-1 (L1) elements as the causative mechanism. Furthermore, the deletion junctions were different between the paternal and maternal mutant alleles, suggesting the occurrence of two independent NAHR events in the ancestors of each parent. The data suggest that the region around exon 9 might be a hot spot of L1-mediated NAHR.  相似文献   
30.
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