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   1706篇
  免费   252篇
  国内免费   21篇
耳鼻咽喉   13篇
儿科学   78篇
妇产科学   27篇
基础医学   90篇
口腔科学   73篇
临床医学   272篇
内科学   445篇
皮肤病学   41篇
神经病学   65篇
特种医学   295篇
外科学   128篇
综合类   18篇
预防医学   294篇
眼科学   11篇
药学   40篇
肿瘤学   89篇
  2023年   48篇
  2022年   13篇
  2021年   13篇
  2020年   41篇
  2019年   21篇
  2018年   53篇
  2017年   36篇
  2016年   45篇
  2015年   54篇
  2014年   97篇
  2013年   119篇
  2012年   36篇
  2011年   53篇
  2010年   65篇
  2009年   82篇
  2008年   54篇
  2007年   75篇
  2006年   55篇
  2005年   46篇
  2004年   44篇
  2003年   17篇
  2002年   20篇
  2001年   26篇
  2000年   26篇
  1999年   41篇
  1998年   66篇
  1997年   91篇
  1996年   80篇
  1995年   60篇
  1994年   63篇
  1993年   53篇
  1992年   16篇
  1991年   13篇
  1990年   31篇
  1989年   42篇
  1988年   31篇
  1987年   35篇
  1986年   33篇
  1985年   32篇
  1984年   13篇
  1983年   13篇
  1982年   24篇
  1981年   30篇
  1980年   17篇
  1979年   7篇
  1978年   5篇
  1977年   15篇
  1976年   14篇
  1975年   10篇
  1969年   2篇
排序方式: 共有1979条查询结果,搜索用时 156 毫秒
31.
Hypospadias trends in two US surveillance systems   总被引:6,自引:0,他引:6  
OBJECTIVE: Hypospadias is a common congenital anomaly, the cause of which is unknown. Unexplained increases in the rates of hypospadias occurred in five European countries in the 1970s and 1980s. We examined data from two birth defects surveillance systems in the United States for evidence of similar trends. METHODOLOGY: The Metropolitan Atlanta Congenital Defects Program (MACDP) provided birth prevalence rates from 1968 to 1993. The nationwide Birth Defects Monitoring Program (BDMP) provided rates from 1970 to 1993. MACDP data are population-based and could be categorized by the severity of the hypospadias. BDMP data allowed analysis of rate trends for the four census regions of the United States. RESULTS: Data from both surveillance systems showed an approximate doubling of hypospadias rates in the 1970s and 1980s. MACDP data showed that the rate of severe cases increased while the ratio of mild to severe cases decreased. BDMP data showed that hypospadias rates increased markedly in all four regions of the United States. CONCLUSIONS: The observed increases are unlikely to be attributable to increased sensitivity of the surveillance systems or the identification of more mild cases by physicians over time, because either trend would have increased rather than decreased the ratio of mild to severe cases. If real, these trends represent the largest number of cases and the first report of an increase in hypospadias rates outside of Europe. Additional investigation of a possible increase in hypospadias rates is warranted.  相似文献   
32.
CONTEXT: Advance directives promote patient autonomy and encourage greater awareness of final care options while reducing physician and family uncertainty regarding patient preferences. PURPOSE: To investigate differences in decision making authority and the use of advance directives among nursing home residents admitted from urban and rural areas. METHODS: A total of 551,208 admission assessments in the Minimum Data Set were analyzed for all residents admitted to a nursing facility in 2001. Using the Rural Urban Commuting Areas (RUCA) methodology and ZIP code of primary residence before admission, these residents were classified into 4 urban/rural areas. FINDINGS: Residents from rural areas were significantly more likely to have executed a durable power of attorney for health care or for financial decisions than residents admitted from the other areas, with the largest differences observed between residents admitted from urban and rural areas. Almost 6 residents in 10 from urban areas had no advance directives in place at admission compared with only 4 residents in 10 admitted from rural areas. CONCLUSIONS: Health providers and social workers in both rural and urban areas should advise patients about the value of advance directives.  相似文献   
33.
Antifungal activity of natural products is being studied widely. Saponins are known to be antifungal and antibacterial. We have isolated eight steroid saponins from Tribulus terrestris L. , namely TTS-8, TTS-9, TTS-10, TTS-11, TTS-12, TTS-13, TTS-14 and TTS-15. TTS-12 and TTS-15 were identified as tigogenin-3-O-β-D-xylopyranosyl(1→ 2)-[-β-D-xylopyranosyl( 1 → 3 ) 3-β- D-glucopyranosyl ( 1 → 4 )- 1- α-L-rhamnopyranosyl ( 1 → 2 ) 3-β-D-galactopyranoside and tigogenin-3-O-β-D-glucopyranpyranosyl(1→2)-[-β-D-xylopyranosyl(1→ 3)3-β-D-glucopyranosyl(1→4)-β-D-galactopyranoside, respectively. The in vitro antifungal activities of the eight saponins against six fluconazole-resistant yeasts, Candida albicans, Candida glabrata, Candida para psilosis , Candida tropicalis , Candida krusei , and Cryptococcus neo f ormans were studied using microbroth dilution assay. The results showed that TTS-12 and TTS-15 were very effective against several pathogenic candidal species and C. neoformans in vitro. It is noteworthy that TTS-12 and TTS-15 were very active against fluconazole-resistant C. albicans (MIC80 = 4.4, 9.4 mg/ml), C. neoformans (MIC80 =10.7, 18.7 mg/ml) and inherently resistant C. krusei (MIC80 =8.8, 18.4 mg/ml). So in vivo activity of TTS-12 in a vaginal infection model with fluconazole-resistant C. albicans was studied in particular. Our studies revealed TTS-12 also showed in vivo activities against fluconazole-resistant yeasts. In conclusion, steroid saponins TTS-12 and TTS-15 from Tribulus terrestris L. have significant in vitro antifungal activity against fluconazole-resistant fungi, especially TTS-12 also showed in vivo activity against fluconazole-resistant C. albicans.  相似文献   
34.
Buprenorphine is considered one of the most effective treatments for opioid use disorder and significantly reduces risk of overdose death. However, concerns about its diversion and misuse have often taken center stage in public discourse and in the design of practices and policies regarding its use. This has been to the detriment of many vulnerable patient populations, especially those involved in the criminal justice system. Policies that restrict access to buprenorphine in criminal justice and other settings due to concerns of diversion do not accurately reflect the relative risks and safety profile associated with it, creating unnecessary barriers that drive an illicit market of this much-needed medication. Although proper regulation of all controlled medications should be a priority, in most instances the benefits of buprenorphine highly outweigh its risks. In the midst of a national crisis, efforts should be focused on expanding, and not restricting, access to this lifesaving treatment.  相似文献   
35.
36.
37.
38.
Aim: To describe gut colonization in preterm infants using standard culture and 16S gene rRNA profiling, exploring differences in healthy infants and those who developed NEC/late onset sepsis (LOS). Methods: Ninety‐nine stools from 38 infants of median 27‐week gestation were cultured; 44 stools from 27 infants had their microbial profiles determined by 16S. Ordination analyses explored effects of patient variables on gut communities. Results: Standard microbiological culture identified a mean of two organisms (range 0–7), DGGE 12 (range 3–18) per patient. Enterococcus faecalis and coagulase negative staphylococci (CONS) were most common by culture (40% and 39% of specimens). Meconium was not sterile. No fungi were cultured. Bacterial community structures in infants with NEC and LOS differed from healthy infants. Infants who developed NEC carried more CONS (45% vs 30%) and less Enterococcus faecalis (31% vs 57%). 16S identified Enterobacter and Staphylococcus presence associated with NEC/LOS, respectively. Conclusions: Important differences were found in the gut microbiota of preterm infants who develop NEC/LOS. The relationship of these changes to current practices in neonatal intensive care requires further exploration.  相似文献   
39.
40.
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