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   487篇
  免费   44篇
  2023年   3篇
  2022年   11篇
  2021年   15篇
  2020年   15篇
  2019年   17篇
  2018年   23篇
  2017年   7篇
  2016年   20篇
  2015年   32篇
  2014年   28篇
  2013年   41篇
  2012年   34篇
  2011年   24篇
  2010年   25篇
  2009年   18篇
  2008年   15篇
  2007年   23篇
  2006年   22篇
  2005年   16篇
  2004年   19篇
  2003年   20篇
  2002年   12篇
  2001年   7篇
  2000年   4篇
  1999年   6篇
  1998年   9篇
  1997年   10篇
  1996年   9篇
  1995年   9篇
  1994年   4篇
  1993年   8篇
  1992年   2篇
  1991年   2篇
  1990年   4篇
  1989年   3篇
  1988年   5篇
  1987年   1篇
  1985年   2篇
  1984年   1篇
  1983年   1篇
  1979年   1篇
  1978年   2篇
  1974年   1篇
排序方式: 共有531条查询结果,搜索用时 765 毫秒
421.
Erythema multiforme is an acute self-limited cutaneous syndrome associated in more than 50% of the cases with herpes simplex virus infection; but it can also be a consequence of other infectious agents or drugs. We report on a 24 year-old female patient with erythema multiforme secondary to Trichophyton mentagrophytes var. mentagrophytes cutaneous infection acquired from contact with animals in a research laboratory.  相似文献   
422.
Nowadays, because of increasing employment of swine for experimental studies and medical training, it is hopeful to investigate novel and effective anaesthetic protocols for preserving the animal welfare in medical investigation and concurrently improving the quality of research. Therefore, the aim of this study was to investigate a novel and effective anaesthetic protocol in swine undergoing major surgery, by translating know-how of combined anaesthesia from human protocols. Seven landrace swine were anaesthetized for three hours by a combined trial anaesthetic protocol (sedation: medetomidine, acepromazine, atropine and tramadol; induction: propofol, medetomidine and acepromazine; anaesthesia: isofluorane, propofol, medetomidine and acepromazine) and both clinical and haemodynamic parameters were compared with those of five swine anaesthetized with a control protocol (sedation: diazepam, ketamine and atropina; induction: diazepam and ketamine; anaesthesia: isofluorane). Both cardiac frequency (CF) and mean blood pressure (MBP) were significantly (P<0.05) more stable in trial protocol (CF: 78.3 ± 4.6-81.1 ± 5, MBP: 63.9 ± 10.7-96.4 ± 13.0) compared to control protocol (CF: 93.7 ± 5.5-102.5 ± 8.5, MBP: 71.0 ± 6.6-108.7 ± 7.2). The body temperature remained stable in trial protocol (°C: 36.9 ± 0.7-37.2 ± 0.3) compared to control anaesthesia (°C: 36.4 ± 0.3-37.3 ± 0.2, P<0.05). Haematosis improved undergoing combined anaesthesia (+2%, P<0.05) whereas did not change in control animals. There were no differences in respiratory rate between trial and control protocols. This study demonstrates that the proposed balanced intravenous-inhalant protocol permits to carry out a very effective, stable and safe anaesthesia in swine undergoing deep anaesthesia.  相似文献   
423.
Of the 22 species currently recognized as valid in the Cryptosporidium genus, C. parvum and C. hominis account for most cases of human infections worldwide. However, C. meleagridis, C. canis, C. felis, C. suis, C. muris, as well as the cervine, rabbit and monkey Cryptosporidium genotypes, have also been recognized as the etiologic cause of both sporadic and epidemic cryptosporidiosis in humans. Molecular methods are necessary to distinguish species and genotypes of Cryptosporidium, due to the lack of reliable morphological variations. The aim of this work was to determine the genetic polymorphisms in a fragment of the A135 gene in isolates of C. parvum, C. hominis, C. meleagridis, C. canis, C. muris, C. andersoni and the Cryptosporidium cervine genotype. Primers were designed on conserved regions identified on a multiple alignment of the C. parvum, C. hominis and C. muris sequences, the three species for which information is available at the genome level. PCR amplification and direct sequencing of a 576 bp fragment revealed the presence of numerous single nucleotide polymorphisms (SNPs) among the species/genotype tested. The genetic variability was exploited to design a PCR-RFLP assay useful for a rapid identification of the most important human pathogens in the genus Cryptosporidium.  相似文献   
424.
425.
1 Larvae of Thaumetopoea pityocampa (Lepidoptera: Notodontidae) develop throughout the winter, although their feeding activity and survival can be impaired by adverse climatic factors. The present study investigated the survival at low temperature of larvae originating from a population with range expansion in an alpine valley in Northern Italy.
2 The supercooling point of individually analysed larvae averaged at −7 °C. This value insufficiently described the cold hardiness of the larvae; 39% of the tested larvae were alive when returned to room temperature immediately after freezing. When larval colonies inside their nest were exposed to −17 °C for 1 h after gradual temperature decrease, survival was 70.4%.
3 Rearing of larvae in the laboratory at different day/night temperatures indicated an effect of cumulative chill injury on larvae. A logistic regression explained the relationship between negative thermal sum (h°C below 0 °C) received in the laboratory experiment and larval survival. A similar relationship was demonstrated between negative thermal sum and survival of larval colonies in the field.
4 In the laboratory experiment, some tested larvae were able to survive for up to 8 weeks without feeding depending on rearing temperature. As expected, feeding occurred only when larvae were reared at temperatures of 9 °C day/0 °C night.
5 We classify the larvae of T. pityocampa as being moderate freezing tolerant. The winter behaviour allows this species to track climate warming by a rapid expansion into those areas that become compatible with the insect's development.  相似文献   
426.

Background

Synchronous midgut carcinoids with gastrointestinal adenocarcinoma are a rare but recognised association.

Case presentation

The patient, a 74 year old woman, underwent anterior resection for a low rectal adenocarcinoma. Intra-operatively 3 serosal deposits of tumour were noted in the distal ileum. Histology revealed these to be ileal carcinoids.

Conclusion

During resection of a gastrointestinal tumour, a thorough inspection of the abdominal cavity should be undertaken to investigate the possibility of metastatic secondaries or a synchronous tumour as is reported in this case.  相似文献   
427.
428.
Chronic inflammation is now accepted to have a critical role in the onset of several diseases as well as in vascular pathology, where macrophage transformation into foam cells contributes in atherosclerotic plaque formation. Endothelial cells (EC) have a critical function in recruitment of immune cells, and proinflammatory cytokines drive the specific expression of several adhesion proteins. During inflammatory responses several cells produce hyaluronan matrices that promote monocyte/macrophage adhesion through interactions with the hyaluronan receptor CD44 present on inflammatory cell surfaces. In this study, we used human umbilical chord vein endothelial cells (HUVECs) as a model to study the mechanism that regulates hyaluronan synthesis after treatment with proinflammatory cytokines. We found that interleukin 1β and tumor necrosis factors α and β, but not transforming growth factors α and β, strongly induced HA synthesis by NF-κB pathway. This signaling pathway mediated hyaluronan synthase 2 (HAS2) mRNA expression without altering other glycosaminoglycan metabolism. Moreover, we verified that U937 monocyte adhesion on stimulated HUVECs depends strongly on hyaluronan, and transfection with short interference RNA of HAS2 abrogates hyaluronan synthesis revealing the critical role of HAS2 in this process.  相似文献   
429.
Summary Geomyces and Chrysosporium species isolated from Antarctica were compared with a strain isolated from Italian soil. The Italian and Antarctic strains had different growth rates and membrane fatty acids at different temperatures.  相似文献   
430.
Cpa135 is a multidomain antigenic protein secreted at the sporozoite stage of the Apicomplexa protozoan Cryptosporidium parvum. Previous studies have shown that the protozoan flagellate parasite Giardia duodenalis is a suitable system for the heterologous expression of secreted proteins of Apicomplexa. Here, we designed three different Cpa135 variants fused to a C-terminal HA tag in order to test their expression in G. duodenalis under the control of the inducible promoter of the cyst wall protein 1 gene (cwp1). The three Cpa135 chimeras encompassed different portions of the protein; CpaG encodes the entire polypeptide of 1574 amino acids (aa); CpaGΔC includes the first 826 aa at the N-terminus; and CpaGΔN consists in of the final 833 aa at the C-terminus. Immunoblot experiments showed that CpaG and CpaGΔN maintained the epitopes recognized by anti-C. parvum-specific human serum. The intracellular localization and transport of the three Cpa135 variants were studied by immunofluorescence in combination with G. duodenalis-specific antibodies. CpaGΔC was mainly accumulated in the endoplasmic reticulum and the intact form was also excreted in the medium. Differently, the Cpa135 chimeras possessing an intact C-terminus (CpaG and CpaGΔN) were transported towards the forming cyst wall possibly and were not detected in the medium. Furthermore, the full-length CpaG was incorporated into the cyst wall. The data presented suggest that the C-terminus of Cpa135, which includes a cysteine reach domain, could influence the secretion of the chimeric proteins.  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