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   595篇
  免费   53篇
  国内免费   3篇
耳鼻咽喉   3篇
儿科学   17篇
妇产科学   23篇
基础医学   99篇
口腔科学   18篇
临床医学   68篇
内科学   102篇
皮肤病学   79篇
神经病学   17篇
特种医学   31篇
外科学   34篇
综合类   9篇
预防医学   66篇
眼科学   3篇
药学   19篇
肿瘤学   63篇
  2021年   4篇
  2020年   6篇
  2019年   13篇
  2018年   5篇
  2017年   6篇
  2016年   9篇
  2015年   9篇
  2014年   15篇
  2013年   19篇
  2012年   15篇
  2011年   23篇
  2010年   17篇
  2009年   21篇
  2008年   31篇
  2007年   30篇
  2006年   21篇
  2005年   26篇
  2004年   20篇
  2003年   17篇
  2002年   28篇
  2001年   14篇
  2000年   24篇
  1999年   23篇
  1998年   14篇
  1997年   16篇
  1996年   9篇
  1995年   16篇
  1994年   9篇
  1993年   12篇
  1992年   20篇
  1991年   11篇
  1990年   12篇
  1989年   17篇
  1988年   15篇
  1987年   13篇
  1986年   5篇
  1985年   11篇
  1984年   8篇
  1983年   9篇
  1982年   10篇
  1981年   9篇
  1980年   8篇
  1979年   4篇
  1977年   3篇
  1976年   3篇
  1972年   2篇
  1971年   2篇
  1968年   2篇
  1967年   2篇
  1961年   2篇
排序方式: 共有651条查询结果,搜索用时 62 毫秒
1.
Annals of Surgical Oncology - The role of sentinel lymph node biopsy (SLNB) when ductal carcinoma in situ with microinvasion (DCISM) is identified on core biopsy is unclear. Our aim was to assess...  相似文献   
2.
OBJECTIVE: Our purpose was to determine whether the incidence of postoperative endometritis and wound infection is associated with the method of placental removal at the time of cesarean section.STUDY DESIGN: Parturients undergoing cesarean delivery were prospectively randomized to have the placenta removed manually or spontaneously. Patients were excluded from participation if they had received intrapartum prophylactic antibiotics or had been determined to have chorioamnionitis. After delivery of the infant women in the manual group had the placenta extracted by the primary surgeon, whereas women in the spontaneous group had the placenta delivered by gentle traction on the umbilical cord. All study subjects received perioperative prophylactic antibiotics. The primary outcome variable was a postcesarean infection, defined as postcesarean endometritis or wound cellulitis requiring drainage and antibiotic therapy.RESULTS: A total of 333 women were enrolled in the investigation, with 165 assigned to the manual removal group and 168 allocated to have spontaneous removal. There were no statistically significant differences in mean gestational age, frequency or duration of ruptured membranes, frequency or duration of labor, or mean number of vaginal examinations between the two study groups. Postoperative infections occurred in 25 of 168 (15%) women in the spontaneous delivery group compared with 44 of 165 (27%) women in which the placenta was manually extracted (relative risk 0.6, 95% confidence interval 0.4 to 0.9, p = 0.01). Subset analysis of patients delivered with ruptured membranes similarly demonstrated a statistically significant reduction in the incidence of postoperative infections with spontaneous placental removal compared with manual extraction (20% vs. 38%, relative risk 0.5, 95% confidence interval 0.3 to 0.9, p = 0.02). There was a similar trend toward a reduction in postdelivery infections associated with spontaneous placental removal in women with intact membranes; however, this difference did not attain statistical significance.CONCLUSIONS: Spontaneous delivery of the placenta after cesarean delivery is associated with a decrease in the incidence of postcesarean infections. (Am J Obstet Gynecol 1997;176:1250-4.)  相似文献   
3.
4.
Diagnosis of perirenal fibrosis by MR imaging   总被引:1,自引:0,他引:1  
A case of retroperitoneal perirenal fibrosis resulting in bilateral proximal ureteral obstruction is reported. Magnetic resonance imaging provided tissue specific diagnosis of the disease.  相似文献   
5.
The MICs of ceftiofur and other antimicrobial agents, tested for comparison, for 515 bacterial isolates of pigs from the United States, Canada, and Denmark with various diseases were compared. The organisms tested included Actinobacillus pleuropneumoniae, Escherichia coli, Pasteurella multocida, Salmonella choleraesuis, Salmonella typhimurium, Streptococcus suis, Streptococcus dysgalactiae subsp. equisimilis, Streptococcus equi subsp. equi, and Streptococcus equi subsp. zooepidemicus. In addition to ceftiofur, the following antimicrobial agents or combinations were tested: enrofloxacin, ampicillin, sulfamethazine, trimethoprim-sulfadiazine (1:19), erythromycin, lincomycin, spectinomycin, lincomycin-spectinomycin (1:8), tilmicosin, and tetracycline. Tilmicosin was only tested against the U.S. isolates. Overall, ceftiofur and enrofloxacin were the most active antimicrobial agents tested against all isolates, with MICs inhibiting 90% of isolates tested (MIC90s) of < or = 2.0 and < or = 1.0 microgram/ml, respectively. Erythromycin, sulfamethazine, spectinomycin, and lincomycin demonstrated limited activity against all of the organisms tested, with MIC90s of > or = 8.0, > or = 256.0, > or = 32.0, and > or = 16.0 micrograms/ml, respectively. Trimethoprim-sulfadiazine was active against isolates of A. pleuropneumoniae, S. choleraesuis, S. typhimurium, P. multocida, S. equi, and S. suis (MIC90s, < or = 0.5 microgram/ml) but was less active against the E. coli strains tested (MIC90, > 16.0 micrograms/ml). Ampicillin was active against the P. multocida, S. suis, and S. equi isolates tested (MIC90s, 0.5, 0.06, and 0.06 micrograms/ml, respectively) and was moderately active against S. typhimurium (MIC90s, 2.0 micrograms/ml). However, this antimicrobial agent was much less active when it was tested against A. pleuropneumoniae, S. cholerae-suis, and E. coli (MIC90s, 16.0, > 32.0, and 32.0 micrograms/ml, respectively). Against the U.S. isolates of A. pleuropneumoniae and P. multocida, tilmicosin was moderately active (MIC90s, 4.0 and 8.0 micrograms/ml, respectively). However, this compound was not active against the remaining U.S. isolates (MIC90s, > 64.0 micrograms/ml). Differences in the MICs from one country to another were not detected with enrofloxacin, ceftiofur, or lincomycin for the strains tested, but variations in the MICs of the remaining antimicrobial agents were observed.  相似文献   
6.
Veterinary diagnostic microbiology is a unique specialty within microbiology. Although isolation and identification techniques are similar to those used for human pathogens, many veterinary pathogens require unique cultivation or identification procedures. Commercial identification systems provide rapid, accurate identification of human pathogens. However, the accuracy of these systems with veterinary pathogens varies widely depending on the bacterial species and the host animal from which it was isolated. Increased numbers of veterinary strains or species in the data bases of the various systems would improve their accuracy. Current procedures and interpretive criteria used for antimicrobial susceptibility testing of veterinary pathogens are based on guidelines used for human pathogens. The validity of these guidelines for use with veterinary pathogens has not been established. As with fastidious human pathogens, standardized methodologies and quality control isolates are needed for tests of organisms such as Actinobacillus pleuropneumoniae and Haemophilus somnus. Furthermore, interpretive criteria for veterinary antimicrobial agents based on the MIC for veterinary pathogens, the pharmacokinetics of the antimicrobial agent in the host animal, and in vivo efficacy of the antimicrobial agent are needed. This article reviews both the commercial identification systems evaluated with veterinary pathogens and current methods for performing and interpreting antimicrobial susceptibility tests with veterinary pathogens. Recommendations for future improvements in both areas are discussed.  相似文献   
7.
Malignancy may adversely influence the quality and behaviour of oocytes   总被引:1,自引:1,他引:1  
A case series of eight cycles of in-vitro fertilization (IVF) in five women diagnosed with malignant disorders is presented. These patients chose to defer definitive treatment for a chance for preservation of potential fertility. The response of these patients to ovarian stimulation, and the outcome, was compared with 17 IVF cycles in 12 age- matched patients with isolated tubal infertility. An apparent adverse influence of malignant disease on the quality and behaviour of oocytes was observed. Despite a comparable total number of oocytes per cycle in the two groups, a significantly reduced percentage of mature oocytes was retrieved per cycle from patients with malignant diseases. The oocytes from patients with malignant disorders were of a poorer quality and exhibited a significantly impaired fertilization rate compared to the controls. We propose that neoplastic processes, irrespective of the site or cell of origin, may have a detrimental impact on the biology of oocytes, an effect akin to that seen on spermatozoa in men with certain malignancies.   相似文献   
8.

Background  

The role of both microglial activation and alpha-synuclein deposition in Parkinson's disease remain unclear. We have tested the hypothesis that if microglia play a primary role in Parkinson's disease pathogenesis, the microglial "activated" phenotype should be associated with histopathological and/or clinical features of the disease.  相似文献   
9.
The effects of colchicine and vinblastine on tanycytes of the rat median eminence have been studied using the electron microscope. Colchicine and vinblastine were administered by intraventricular cannulation into the third ventricle and demonstrated distinct morphological effects on tanycyte microtubules. Highest drug doses administered were 50.0 mug in 5.0 mul of saline initially, followed by an additional 50.0 mug of these agents infused in a volume of 13.0 mul saline over an hour. Colchicine treatment resulted in the formation of large crystalloids within tanycytes, coincident with the disappearance of microtubules, all along the ventricular surface. Nonetheless the tanycytes appeared able to maintain a continuous, tight lining, as in controls, although some crystalloids were observed beneath the ventricular surface, either within tanycyte processes or within neuronal processes. Vinblastine treatment also resulted in the formation of identical crystalloids but at highest doses thoroughly destroyed the tanycyte lining of the median eminence and exposed cellular elements below the surface to the drug. Portal capillaries approaching the ventricular surface were generally free of any signs of drug response to either colchicine or vinblastine.  相似文献   
10.
Siderophore Production by Pathogenic Neisseria spp   总被引:6,自引:13,他引:6       下载免费PDF全文
Previous studies have established the importance of iron acquisition to the growth and virulence of Neisseria meningitidis and Neisseria gonorrhoeae. Although preliminary evidence that the Neisseria spp. produce siderophores has been presented, the exact mechanism of iron acquisition has remained obscure. Siderophore production by N. gonorrhoeae and N. meningitidis was induced in two different low-iron media. The iron-reactive siderophores, “gonobactin” and “meningobactin,” were partially purified by ion exchange chromatography followed by extraction with phenol-chloroform-ether or by gel filtration. The compounds were of low molecular weight, their synthesis was repressed by iron in the medium, and they appeared to be hydroxamic acids since they were stimulatory for Arthrobacter flavescens JG-9 (a hydroxamate auxotroph) and gave a positive Csáky reaction for bound hydroxylamine. In the iron form, the compounds had an absorption maximum of approximately 420 nm. Although meningobactin stimulated growth of the gonococcus in low-iron media and vice versa, the homologous activity was more marked, indicating that the compounds, though similar, were probably not identical. As determined by A. flavescens assay the meningococcus produced three to five times more siderophore than did the gonococcus; however, the amount of siderophore present in the culture fluids of even the meningococcus was 100- to 1,000-fold lower than the concentration of hydroxamate siderophores reported to be produced by Bacillus megaterium or Aerobacter aerogenes. Virulent, colony type 1 N. gonorrhoeae produced significantly more gonobactin than did the avirulent colony type 3 gonococci.  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