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   1872篇
  免费   145篇
  国内免费   10篇
耳鼻咽喉   24篇
儿科学   14篇
妇产科学   15篇
基础医学   264篇
口腔科学   102篇
临床医学   148篇
内科学   510篇
皮肤病学   53篇
神经病学   117篇
特种医学   65篇
外科学   272篇
综合类   8篇
预防医学   64篇
眼科学   54篇
药学   136篇
中国医学   3篇
肿瘤学   178篇
  2023年   11篇
  2022年   17篇
  2021年   31篇
  2020年   23篇
  2019年   30篇
  2018年   37篇
  2017年   42篇
  2016年   47篇
  2015年   39篇
  2014年   44篇
  2013年   69篇
  2012年   87篇
  2011年   105篇
  2010年   47篇
  2009年   47篇
  2008年   91篇
  2007年   106篇
  2006年   109篇
  2005年   104篇
  2004年   92篇
  2003年   113篇
  2002年   77篇
  2001年   47篇
  2000年   48篇
  1999年   46篇
  1998年   27篇
  1997年   29篇
  1996年   16篇
  1995年   29篇
  1993年   10篇
  1992年   29篇
  1991年   34篇
  1990年   39篇
  1989年   20篇
  1988年   28篇
  1987年   12篇
  1986年   26篇
  1985年   21篇
  1984年   16篇
  1983年   19篇
  1981年   11篇
  1980年   9篇
  1979年   18篇
  1978年   9篇
  1977年   11篇
  1972年   14篇
  1971年   12篇
  1969年   10篇
  1968年   13篇
  1967年   9篇
排序方式: 共有2027条查询结果,搜索用时 10 毫秒
51.
Endocrine gland-derived vascular endothelial growth factor (EG-VEGF) is an endothelial cell mitogen, expressed essentially in steroidogenic cells. Recently, the expression of EG-VEGF in normal human pancreas and pancreatic adenocarcinoma has been demonstrated. Epidemiologically, pancreatic carcinogenesis is more frequent in males than females, and given that androgen receptors and testosterone biotransformation have been described in pancreas, we hypothesized that testosterone could participate in the regulation of EG-VEGF expression. In this study, we investigated the regulation of EG-VEGF gene expression by testosterone in normal rat pancreatic tissue and rat insulinoma cells (RINm5F). Total RNA was extracted from rat pancreas and cultured cells. Gene expression was studied by real-time PCR and protein detection by immunohistochemistry. Serum testosterone was quantified by RIA. Results showed that EG-VEGF is expressed predominantly in pancreatic islets and vascular endothelium, as well as in RINm5F cells. EG-VEGF gene expression was lower in the pancreas of rats with higher testosterone serum levels. A similar effect that was reverted by flutamide was observed in testosterone-treated RINm5F cells. In summary, testosterone down-regulated EG-VEGF gene expression in rat pancreatic tissue and RINm5F cells. This effect could be mediated by the androgen receptor. To our knowledge, this is the first time that a direct effect of testosterone on EG-VEGF gene expression in rat pancreas and RINm5F cells is demonstrated.  相似文献   
52.
Afibrinogenaemia usually induces a bleeding tendency during infancy, whereas protein C deficiency increases susceptibility to thrombosis in children or adolescence. Mutations of these genes have been, therefore, established as independent risk factors for coagulation disorders. We describe the homozygous mutation of the fibrinogen alpha chain gene and additional heterozygous mutation of the protein C gene in a male infant who showed prolonged umbilical bleeding after birth. On examination, the plasma fibrinogen was undetectable, and the activity and antigen level of protein C were reduced. The patient showed no fibrinogen Aalpha chain as well as Bbeta and gamma chains by Western blotting. The sequencing analysis showed the homozygous deletion of 1238 bases from intron 3 at position 2008 to intron 4 at position 3245 in the fibrinogen alpha chain gene. Both parents were heterozygous carriers of this mutation. In this patient, an additional mutation was also detected in the protein C gene: the heterozygous deletion of exon 7 at position 6161-6163 or 6164-6166, resulting the deletion of one amino acid (Lys150 or 151). His mother was also a carrier of this mutation. As the simultaneous mutation of the fibrinogen alpha chain and protein C genes has not been previously reported, the influence of the interaction between these two mutations on the clinical manifestations of this patient should be carefully monitored for a long period.  相似文献   
53.
Because of variations in tRNA sequences in evolution, tRNA synthetases either do not acylate their cognate tRNAs from other organisms or execute misacylations which can be deleterious in vivo. We report here the cloning and primary sequence of a 958-aa Saccharomyces cerevisiae alanyl-tRNA synthetase. The enzyme is a close homologue of the human and Escherichia coli enzymes, particularly in the region of the primary structure needed for aminoacylation of RNA duplex substrates based on alanine tRNA acceptor stems with a G3.U70 base pair. An ala1 disrupted allele demonstrated that the gene is essential and that, therefore, ALA1 encodes an enzyme required for cytoplasmic protein synthesis. Growth of cells harboring the ala1 disrupted allele was restored by a cDNA clone encoding human alanyl-tRNA synthetase, which is a serum antigen for many polymyositis-afflicted individuals. The human enzyme in extracts from rescued yeast was detected with autoimmune antibodies from a polymyositis patient. We conclude that, in spite of substantial differences between human and yeast tRNA sequences in evolution, strong conservation of the G3.U70 system of recognition is sufficient to yield accurate aminoacylation in vivo across wide species distances.  相似文献   
54.
Lactobacillus (LB) is a gram-positive rod-shaped bacterium that inhabits the oral cavity, gastrointestinal tract, vagina and nasal cavity. Although LB plays a role in the prevention of infections caused by pathogenic bacteria, it causes some critical infectious diseases such as infective endocarditis (IE). IE due to LB is rare; however, early diagnosis and early treatment are important because of its high mortality rate. We report the onset of IE after otologic treatment in a heavy drinker of alcohol, the second case of IE due to LB in Japan.  相似文献   
55.
A 41-year-old male patient with hepatitis B underwent right tri-segmentectomy and total caudate lobectomy for a huge hepatocellular carcinoma associated with complete occlusion of the inferior vena cava with thrombosis of the infrahepatic inferior vena cava due to tumor compression. Five months later, he was readmitted for ascites and hyperbilirubinemia. Venography revealed stenosis and tortuosity of the left hepatic vein and the inferior vena cava, for which balloon angioplasty of the left hepatic vein and the inferior vena cava was performed using an 8-mm and 10-mm balloon, respectively. The left hepatic venous pressure decreased from 65 mmHg to 25 mmHg after dilatation. The patient made a satisfactory recovery thereafter and remains well with normal liver functions and without ascites. Balloon angioplasty may be useful for liver failure due to hepatic vein stenosis after hepatic resection.  相似文献   
56.
57.
58.
59.
Annals of Nuclear Medicine - Somatostatin receptors are highly expressed in neuroendocrine tumors, and many radiolabeled somatostatin analogs for diagnosis and treatment have been developed. To...  相似文献   
60.
We re-evaluated the criteria for waist circumference to predict the accumulation of the components of metabolic syndrome. We used data for 3,185 Japanese, aged 20-79 years. Metabolic syndrome has recently been redefined by a new criterion in Japan, in which waist circumference cutoff points, i.e. 85 cm for men and 90 cm for women, are employed. Among the 3,185 Japanese considered in the present study, 335 men (26.8%) and 69 women (3.6%) were diagnosed as having metabolic syndrome. A cutoff point as a predictor for 2 or more components of metabolic syndrome was evaluated by sensitivity/specificity and a receiver operating characteristic (ROC) curve. The optimal point was estimated as being approximately 85 cm of waist circumference in men and 75 cm in women. We therefore recommend a cutoff value, 75 cm of waist circumference, for the criterion of metabolic syndrome in women.  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