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   3884篇
  免费   309篇
  国内免费   19篇
耳鼻咽喉   21篇
儿科学   182篇
妇产科学   125篇
基础医学   421篇
口腔科学   95篇
临床医学   387篇
内科学   937篇
皮肤病学   59篇
神经病学   280篇
特种医学   190篇
外国民族医学   1篇
外科学   470篇
综合类   97篇
一般理论   1篇
预防医学   413篇
眼科学   14篇
药学   214篇
中国医学   3篇
肿瘤学   302篇
  2021年   50篇
  2020年   36篇
  2019年   59篇
  2018年   57篇
  2017年   48篇
  2016年   50篇
  2015年   50篇
  2014年   99篇
  2013年   132篇
  2012年   182篇
  2011年   169篇
  2010年   136篇
  2009年   110篇
  2008年   142篇
  2007年   198篇
  2006年   188篇
  2005年   175篇
  2004年   147篇
  2003年   145篇
  2002年   116篇
  2001年   103篇
  2000年   129篇
  1999年   107篇
  1998年   77篇
  1997年   64篇
  1996年   63篇
  1995年   47篇
  1994年   50篇
  1993年   40篇
  1992年   78篇
  1991年   77篇
  1990年   59篇
  1989年   65篇
  1988年   75篇
  1987年   56篇
  1986年   52篇
  1985年   39篇
  1984年   53篇
  1983年   36篇
  1981年   31篇
  1980年   44篇
  1978年   42篇
  1977年   34篇
  1974年   44篇
  1972年   32篇
  1970年   49篇
  1969年   33篇
  1968年   34篇
  1967年   31篇
  1966年   35篇
排序方式: 共有4212条查询结果,搜索用时 15 毫秒
91.
OBJECTIVE: Hormonal stimulation with secretin or cholecystokinin (CCK) is the most sensitive means of assessing pancreatic function. Secretin is not available, and current CCK tests are cumbersome, requiring dual tube intubation and marker perfusion techniques. The aim of this study was to test the efficacy of a new CCK-stimulated pancreatic function test measuring peak lipase concentration. METHODS: A Dreiling gastroduodenal tube was inserted to the ligament of Treitz, and fluid was collected on ice for 80 min in four 20-min aliquots. CCK was infused i.v. at a constant rate of 40 ng/kg/h. Gastric aspirations were discarded. Duodenal aspirates were analyzed for volume and enzyme concentration with a clinical laboratory autoanalyzer. RESULTS: Nineteen healthy volunteers and 18 chronic pancreatitis patients were studied. Lipase concentration and secretory volume showed a peak response by 40 min of stimulation, whereas amylase response was variable. The mean peak lipase concentrations (+/-SEM) for normal volunteers and mild, moderate, and advanced chronic pancreatitis patients were 16.9+/-1.9, 7.9+/-1.7, 3.7+/-1.2, and 2.1+/-0.6 x 10 5 IU/L, respectively. Lower peak lipase concentrations were significantly associated with more advanced chronic pancreatitis (p < 0.001). The receiver operating characteristic curve area for all chronic pancreatitis patients was 0.944 (95% CI = 0.825-0.985). A peak lipase concentration of 780,000 IU/L provided a sensitivity and specificity of 0.833 and 0.867, respectively. This CCK test was well tolerated and without complications. CONCLUSIONS: Lipase concentration in duodenal fluid increases nearly 3-fold from baseline after CCK stimulation in healthy volunteers but is markedly reduced in patients with chronic pancreatic disease. Peak lipase concentration is a significant predictor of chronic pancreatitis and correlates with severity of pancreatic disease. Aspiration of duodenal drainage fluid with a Dreiling tube and analysis with a laboratory autoanalyzer are less cumbersome than marker perfusion and back titration techniques. Measurement of enzyme concentration instead of output could lead to the development of an endoscopic or through-the-scope screening method for assessing patients with suspected chronic pancreatitis or chronic abdominal pain.  相似文献   
92.

Background and purpose

Pneumonia is the most important respiratory problem in low‐to‐middle income countries. Airway clearance therapy continues to be used in children with pneumonia and secretion retention; however, there is lack of evidence to support or reject this treatment. This study aimed to investigate the feasibility of a randomized controlled trial (RCT) on the efficacy and safety of assisted autogenic drainage (AAD) compared to standard nursing care in children hospitalized with uncomplicated pneumonia.

Methods

A single‐blinded pilot RCT was conducted on 29 children (median age 3.5 months, IQR 1.5–9.4) hospitalized with uncomplicated pneumonia. The intervention group received standard nursing care with additional bi‐daily AAD, for 10 to 30 min. The control group only received standard nursing care, unless otherwise deemed necessary by the physician or physiotherapist. The primary outcome measure was duration of hospitalization. The secondary outcome measures included days of fever and supplemental oxygen support; respiratory rate (RR) and heart rate adjusted for age; RR and oxygen saturation pre‐, post‐, and 1‐hr post‐treatment; oxygen saturation; adverse events; and mortality.

Results

No difference was found for duration of hospitalization (median 7.5 and 7.0 days for the control and intervention groups, respectively); however, Kaplan–Meier analysis revealed a strong tendency towards a shorter time to discharge in the intervention group (p = .06). No significant differences were found for the other outcome measures at time of discharge. No adverse events were reported. Within the intervention group, a significant reduction in RR adjusted for age was found.

Discussion

As no adverse events were reported, and AAD did not prolong hospitalization; AAD might be considered as safe and effective in young children with uncomplicated pneumonia. However, a larger multicentred RCT is warranted to determine the efficacy of AAD compared to standard nursing care.  相似文献   
93.
94.
A 21-years-old with Down syndrome presented with respiratory distress. Initial investigations revealed a cardiac tamponade. On further evaluation, he had positive coronavirus disease-2019 (COVID-19), severe chest infection and severe hypothyroidism. He responded well to urgent pericardiocentesis, levothyroxine, hydrocortisone and tocilizumab.  相似文献   
95.
96.
97.
Thrombopoietin and its receptor (MPL) are important regulators of megakaryopoiesis. We have identified an activating mutation of MPL using a combination of a retrovirus-mediated gene transfer and polymerase chain reaction-driven random mutagenesis. This point mutation causes a single amino acid substitution from Ser498 to Asn498 in the transmembrane region and abrogates factor-dependency of all interleukin-3-dependent cell lines tested. Murine interleukin-3- dependent Ba/F3 cells expressing the mutated but not the normal form of MPL were tumorigenic when transduced into syngeneic mice. Analysis of intracellular signaling pathways indicated that the mutant MPL protein constitutively activated two distinct signaling pathways, SHC-Raf-MAPK and JAK2-STAT3/STAT5.  相似文献   
98.
99.
Since 1976, we have implanted bilateral phrenic nerve electrodes for diaphragm pacing in 33 infants and children. This population includes 23 patients with congenital central hypoventilation syndrome (CHS), two with late onset CHS and hypothalamic dysfunction, three with hypoventilation associated with Chiari II malformation and myelomeningocele, and five with quadriplegia. Our experience, totalling 192 system-years and 96 patient-years of pacing, has enabled us to document the nature and frequency of problems related to the implanted components of the Avery Laboratories (S-232-1) pacemaker system when used in a pediatric population. By life table analysis, the mean time to need for replacement of any implanted component was 56.3 months. A total of 26 failures requiring component replacement occurred and were classified into four types: (1) receiver failure (15 cases), (2) electrode wire or wire insulation breakage (six cases), (3) infection requiring diaphragm pacer system removal (three cases), and (4) mechanical nerve injury (two cases). We conclude that the present diaphragm pacing system is effective but not without risk of biomedical component failure. The present system might be substantially improved by (1) a modified receiver design with a hermetic seal to prevent fluid penetration, (2) stronger, better insulated electrode wires, and (3) modifications of surgical technique and electrode type to prevent phrenic nerve damage.  相似文献   
100.
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