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   6153篇
  免费   256篇
  国内免费   22篇
耳鼻咽喉   23篇
儿科学   107篇
妇产科学   54篇
基础医学   838篇
口腔科学   79篇
临床医学   349篇
内科学   1549篇
皮肤病学   61篇
神经病学   533篇
特种医学   287篇
外科学   1258篇
综合类   19篇
预防医学   180篇
眼科学   131篇
药学   365篇
中国医学   5篇
肿瘤学   593篇
  2023年   36篇
  2022年   69篇
  2021年   130篇
  2020年   78篇
  2019年   99篇
  2018年   123篇
  2017年   96篇
  2016年   110篇
  2015年   121篇
  2014年   176篇
  2013年   229篇
  2012年   370篇
  2011年   395篇
  2010年   199篇
  2009年   168篇
  2008年   344篇
  2007年   400篇
  2006年   391篇
  2005年   410篇
  2004年   389篇
  2003年   402篇
  2002年   357篇
  2001年   60篇
  2000年   56篇
  1999年   76篇
  1998年   98篇
  1997年   94篇
  1996年   87篇
  1995年   79篇
  1994年   64篇
  1993年   62篇
  1992年   58篇
  1991年   52篇
  1990年   60篇
  1989年   44篇
  1988年   37篇
  1987年   39篇
  1986年   38篇
  1985年   24篇
  1984年   42篇
  1983年   34篇
  1982年   40篇
  1981年   20篇
  1980年   27篇
  1979年   11篇
  1978年   15篇
  1977年   13篇
  1976年   12篇
  1974年   15篇
  1973年   11篇
排序方式: 共有6431条查询结果,搜索用时 13 毫秒
41.
Estrogen: one of the risk factors in milk for prostate cancer   总被引:7,自引:0,他引:7  
Studies to elucidate the cause of prostate cancer have met with little success to date. Epidemiological studies suggested that milk consumption is probably as one of the risk factors for prostate cancer. The studies thus focused on the fat and calcium in milk, but reached no definitive conclusion. According to the measurements of estrogen levels in milk by different studies, it was suggested that estrogen in milk was a possible risk to cause prostate cancer. One reason supporting this hypothesis is that Western diet (characterized by milk/dairy products and meat) causes a trend of increasing levels of estrogens, and Western males show a higher incidence rate of prostate cancer than Asia males. Estrogen levels in prostate fluid are also correlated very well with the prostate cancer. During several decades, estrogens, together with testosterone, was commonly used to induce the rodent model of prostate cancer. Our hypothesis also was supported by the presence of estrogen receptors in the prostate gland and the genotoxic role of estrogens on the prostate gland, as possible mechanisms. Therefore, if modern milk consumption does expose consumers to high levels of estrogen and plays an adverse role in prostate cancer, action should be taken to produce the noncontaminant milk.  相似文献   
42.
43.
A second group of hepatitis C viruses   总被引:7,自引:0,他引:7  
cDNA clone 11–7 was isolated by immunoscreening a cDNA library that was prepared from a pooled plasma of non-A non-B hepatitis (NANBH) patients using expression vector gt 11. This cDNA corresponds to known nucleotide positions 3983–4745 of the genome of hepatitis C virus (HCV). This clone was used as a probe for screening the HCV-related cDNAs in a cDNA library similarly prepared by using gt 10. As a result, six more cDNA clones were isolated and analyzed for their nucleotide sequences. The results strongly suggested that there are at least two groups of HCV, group I and group II. According to our classification, the prototype HCV and clone 11–7 belong to group I HCV, and their nucleotide and deduced amino acid sequences were diverged from those of group II HCV. Genetic variation observed in the nucleotide and the amino acid sequences between the two groups resembles that in the NS3 region of the genome between Japanese encephalitis virus and West Nile fever virus. Polypeptides produced inEscherichia coli carrying a clone 11–7 or a group II cDNA clone E reacted with antibodies in the blood of 12 or 4 out of 14 individual chronic NANBH patients, respectively. Our data clearly indicate the existence of a second group of HCV.  相似文献   
44.
A 7-year-old boy with moyamoya disease developed sustained hypertension, nephrotic syndrome, hyperreninemia, and occlusion of the right renal artery. After right nephrectomy, hyperreninemia and hypertension improved. Proteinuria was resolved after nephrectomy, in parallel with the decrease in plasma renin activity. Moyamoya disease can cause nephrotic-range proteinuria, which is caused hemodynamically by hyperreninemia.  相似文献   
45.
We carried out an experiment to analyze morphological differences in hearts of rats well adapted and poorly adapted to chronic hypoxia. Male and female Wistar rats, 1 week, 4 weeks and 9 weeks old, were employed on the assumption that adaptive ability was dependent on age and sex. These rats were raised at an altitude of 2,400 m and were kept for 7 to 9 weeks. Control groups were maintained at an altitude of 600 m during the same period of time. Each group consisted of 4 to 6 rats. At the end of the experiment, body weight, heart weight, ratio of heart weight to body weight and hematocrit were measured, and ventricular wall thickness, myocardial fiber diameter, capillary supply and mitochondria were morphometrically studied. Of the 6 experimental groups, the 4-week-old male rats (M2) had the highest body weight, as compared with the other experimental groups. In addition, relative to these other experimental groups, the following features were found for M2. Heart weight was intermediate, heart weight/body weight ratio was low and hematocrit was also low. Ventricular wall thickness was intermediate in the right ventricle (RV) and interventricular septum (IVS) but was thin in the left ventricle (LV). Myocardial fiber diameter was intermediate in the RV, large in the IVS and small in the LV. Capillary supply was intermediate in the RV and dense in the IVS and LV. Mitochondria were small but cristal density and percentage area, estimated from electron micrographs, were found to be high. These data showed that in well developed rats under chronic hypoxia, there is good development of capillary supply with corresponding restriction of cardiac hypertrophy, while hematocrit count and mitochondria are also affected.  相似文献   
46.
The genomic RNA of the Japanese encephalitis virus (JEV) Beijing-1 strain was reversely transcribed and the synthesized cDNA was molecularly cloned. Six continuous cDNA clones that cover the entire virus genome were established and sequenced to determine the complete nucleotide sequence of the JEV RNA. The precise genomic size was estimated as 10,965 bases long. With flanking 95 bases at the 5 and 583 bases at the 3 non-coding regions, one long open reading frame (ORF) was revealed encoding a virus polyprotein with 3,429 amino acid residues. Because of sequence homologies observed between JEV and other flaviviruses, the genome organization of JEV appears to be identical with other flaviviruses. Genetic variation detected among flavivirus genomes is consistent with the established serological relatedness between JEV and other members of flaviviruses. The secondary structure of the JEV genome is deduced and discussed concerning its involvement in genome replication.  相似文献   
47.
This is a case report of a malignant mesenchymoma of the esophagus in a 50?year-old Japanese man. The tumor was a sessile polypoid mass showing a downward invasion limited to the submucosa of the esophagus. Histologically, the lesion contained rhabdomyosarcomatous and osteosarcomatous areas, in addition to an ill-defined fibrosarcomatous element. In contrast with reports of carcinosarcoma up to the present, this tumor lacked any invasive lesion of an epithelial malignancy. The morphogenesis of these tumor groups was discussed from a hamartoblastomatous standpoint. Acta pathol. jpn. 34: 925~933, 1984.  相似文献   
48.
49.
50.
Rheumatoid arthritis (RA) is one of the immune complex (IC) diseases in which lymphoid germinal centers (GCs) are found in the synovial tissue. Simultaneously, patients with RA often show swelling of lymph nodes. The morphology and function of the lymph node GCs in patients with RA is not clear. The aim of this study was to evaluate the differences in morphology and immunoreactions to complement (C) components, their receptors, and lgM-rheumatoid factor (RF) between synovial GCs and lymph-node GCs in RA. Furthermore, the relationship between these immuno-reactive substances and follicular dendritic cells (FDCs) in GCs was investigated. The tissues examined were 41 RA synovial specimens, seven RA lymph nodes with massive lymphadenopathy, and 10 non-RA lymph nodes. The number of synovial GCs was relatively decreased in comparison with lymph-node GCs in RA, and the diameter of each synovial GC was smaller than that of each lymph-node GC. The synovial GCs were edematous and less cellular, and moreover, those from RF-seronegative cases were smaller than those from RF seropositive cases. On the other hand, the lymph-node GCs in RA were larger, more cellular and hyperplastic, but contained more tingible-body macro-phages (TBMs) and neutrophils. In the GCs of both synovial tissues and lymph nodes in RA, early C components (C1q, C4, C3c, C3d), IgM RF, and C3b receptor (C3bR) and C3d receptor (C3dR) were expressed as a lacy network by light microscopy, and were demonstrated on the surfaces of FDCs and lymphocytes, and in the intercellular spaces by electron microscopy. Furthermore, immuno-staining for dendritic reticulum cells (DRC, DAKO DRC1) was observed in a lacy pattern by light microscopy and on the cell surface of FDCs by electron microscopy. In the GCs of non-RA lymph nodes, early C components, C3bR, C3dR, and DRC showed a similar reaction pattern, but IgMRF did not. Consequently, no marked difference in immunoreactions in the GCs, except for the immunoreactions of late C components, was found between synovial tissues and lymph nodes in RA. On the basis of these findings, we discuss the possibility of the presence of a RF-IC.  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