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   420篇
  免费   21篇
  441篇
  2023年   1篇
  2022年   3篇
  2021年   11篇
  2020年   9篇
  2019年   12篇
  2018年   13篇
  2017年   9篇
  2016年   10篇
  2015年   12篇
  2014年   20篇
  2013年   21篇
  2012年   30篇
  2011年   20篇
  2010年   11篇
  2009年   21篇
  2008年   21篇
  2007年   18篇
  2006年   21篇
  2005年   26篇
  2004年   25篇
  2003年   18篇
  2002年   17篇
  2001年   10篇
  2000年   9篇
  1999年   8篇
  1998年   4篇
  1997年   4篇
  1996年   3篇
  1995年   2篇
  1993年   4篇
  1992年   8篇
  1991年   5篇
  1990年   6篇
  1989年   5篇
  1988年   4篇
  1985年   2篇
  1983年   1篇
  1982年   4篇
  1981年   1篇
  1979年   3篇
  1977年   3篇
  1976年   1篇
  1974年   1篇
  1970年   1篇
  1966年   1篇
  1965年   2篇
排序方式: 共有441条查询结果,搜索用时 18 毫秒
431.
Only one out of 19 soil sampling sites chosen for isolation of H. capsulation studies yielded positive results. The stations were located in Cueva Oscura, which is part of the Aguas Buenas Caves system. The habitat characteristics of these station are believed to be responsible for the presence of the fungus.This study was supported by the Department of Natural Resources in cooperation with the Department of Health and the Municipality of Aguas Buenas, all from Puerto Rico.  相似文献   
432.
The activation of interleukin receptor associated kinases (IRAK) is an important event in several inflammatory processes. However, exposing monocytes to a nitric oxide (NO) donor inhibits the activity of IRAK-1 and its molecular interaction with TNF receptor associated factor-6 (TRAF6). Despite the fact that NO is known to regulate many events in the immune and vascular system, the mechanism that underlies this inhibition remains unknown. We have recently demonstrated that IRAK-M inhibits the TLR/IRAK pathway during endotoxin tolerance and thus, we hypothesized that IRAK-M may be involved in the inhibition of IRAK-1 activity in the presence of NO. Hence, we have analyzed the expression of IRAK-M in human monocytes following exposure to a NO donor (GSNO) and we have observed that GSNO was capable of inducing IRAK-M mRNA and protein expression 8 and 20 h after stimulation, respectively. It is known that NO induces the expression of TNF-alpha in monocytes and we found that exposure to TNF-alpha induced IRAK-M mRNA expression in human monocytes within 2 h of stimulation. Furthermore, the expression of IRAK-M induced by GSNO was inhibited by the presence of a blocking antibody raised against TNF-alpha. Thus, our data indicate that stimulation of human monocytes with a NO donor results in a clear induction of IRAK-M and this is dependent on the release of TNF-alpha by this kind of cells.  相似文献   
433.
Context: Prognostic value of ST2 levels and dynamics has not been investigated in acute heart failure (AHF) using prospective real-life measurements.

Objective: The objective of this study is to investigate the prognostic value of ST2 in AHF.

Methods: ST2 levels were determined at admission (n?=?182) and discharge (n?=?85). Primary endpoint was the composite of all-cause death and HF rehospitalisation at one year.

Results: Discharge ST2 (HR 2.42 [95% CI 1.46–4], p?=?0.001) and ΔST2 (HR 2.32 [95% CI 1.21–4.57], p?=?0.01) but not admission ST2, remained independently prognostic for the primary endpoint after comprehensive multivariable adjustment. ST2 significantly improved prognosis stratification on top of clinical variables and NTproBNP.

Conclusions: Routine clinical use of discharge ST2 and ST2 dynamics provide independent prognostic information.  相似文献   
434.
In this paper we study aspects of the breeding system of Hormathophylla spinosa (Crucifcrae) to identify the factors responsible for seed production in the absence of insect pollinators. The pollinator-exclusion experiments show that H. spinosa, under natural conditions, does not produce seed by apomixis or spontaneous autogamy. H. spinosa appears to be self-incompatible but slightly geitonogamous. Thus, this plant species needs pollen vectors for reproduction. The results of the wind-exclusion experiments performed during two different years in two populations of H. spinosa support the hypothesis that the wind acts as a pollen vector; flowers excluded from the wind had a lower fruit set and female fertility than flowers excluded from all pollinator insects (winged and wingless). This generalist pollination system (insects and wind) permits this species to colonize and sustain viable populations in high mountains, where this species is the only woody shrub living above 3000 m above sea level in the Sierra Nevada.  相似文献   
435.
The effects of increasing levels of dietary dextrin on growth performance, body composition, blood chemistry and hepatic triglycerides and glycogen levels were evaluated for juvenile Lebranche mullet, Mugil liza Valenciennes 1836, Mugilidae). Five diets were formulated to be isonitrogenous (350 g kg?1) and isolipidic (6 g kg?1) with increasing dextrin levels (D150: 150 g kg?1; D200: 200 g kg?1; D250: 250 g kg?1; D300: 300 g kg?1; D350: 350 g kg?1). The experimental diets were offered to the fish for 34 days, four times per day, until apparent satiation. Each treatment was tested in triplicate, with nine fish per tank (mean weight 4.69 ± 0.31 g). Fish were reared in a recirculating aquatic system of 15 fibreglass tanks each containing 50 L of saltwater. Growth parameters and body composition of the mullets were not significantly affected (P > 0.05) by the dietary treatments. Plasma glucose concentration declined (P < 0.05) when dietary dextrin increased from D250 to D300, but recovered to the previous values (in reference to D150 and D200) when fish were fed with D350. Glycated haemoglobin, plasma proteins, triglycerides and cholesterol showed no significant differences among these treatments. Hepatic glycogen reached a maximum in treatment D250, followed by D350, D200 and D300, with the lowest concentration of liver glycogen found in D150 (P < 0.05). The concentration of liver triglycerides showed an increase (P < 0.05) in treatments D300 and D350 compared with D200. In conclusion, Mugil liza juveniles can be fed diets with high levels of dietary dextrin with no deleterious effects to their growth or plasma biochemistry, hepatic glycogen or triglycerides.  相似文献   
436.

Background  

The phase-space relationship between simultaneously measured myoplasmic [Ca2+] and isovolumetric left ventricular pressure (LVP) in guinea pig intact hearts is altered by ischemic and inotropic interventions. Our objective was to mathematically model this phase-space relationship between [Ca2+] and LVP with a focus on the changes in cross-bridge kinetics and myofilament Ca2+ sensitivity responsible for alterations in Ca2+-contraction coupling due to inotropic drugs in the presence and absence of ischemia reperfusion (IR) injury.  相似文献   
437.
Summary Isolated medio-basal hypothalami of adult rats were continuously superfused in a chamber with controllable inputs and outputs, for periods from 30 to 240 min. The median eminence was prepared for transmission electron microscopy under carefully controlled conditions by immersion fixation with osmium tetroxide. The ultrastructure of superfused median eminence was compared with that of directly fixed, non-superfused median eminence. Even after 4h of superfusion, the median eminence displays remarkably well preserved histological and cytological patterns; cytomembranes, cell organelles, intercellular relationships, and extracellular spaces were remarkably similar in superfused and non-superfused tissues. As a consequence of osmium tetroxide fixation, microtubules were not observable. The ultrastructural information obtained from unstimulated rat median eminence superfused in vitro provides a basis for future morphofunctional correlations in the study of neurosecretion.  相似文献   
438.
1. Partial hepatectomy (25% of liver mass removed) has been performed on rainbow trout using a procedure allowing a high level of survival. 2. The liver regeneration was complete from the point of view of liver weight, at the 30th post-operative day. 3. During the first weeks after surgery, the NH-excretion rate in both hepatectomized and shamoperated trout was higher than in intact controls. Likewise, the food intake was lower in the operated animals. 4. Both facts can be attribute to the stress situation caused by the surgical manipulations rather than the removal of the liver.  相似文献   
439.
BACKGROUND:Cesarean delivery is the most common surgical procedure worldwide. Intrapartum fetal surveillance is routinely offered to improve neonatal outcomes, but the effects of different methods on the risk of emergency cesarean deliveries remains uncertain. We conducted a systematic review and network meta-analysis to evaluate the effectiveness of different types of fetal surveillance.METHODS:We searched MEDLINE, Embase and CENTRAL until June 1, 2020, for randomized trials evaluating any intrapartum fetal surveillance method. We performed a network meta-analysis within a frequentist framework. We assessed the quality and network inconsistency of trials. We reported primarily on intrapartum emergency cesarean deliveries and other secondary maternal and neonatal outcomes using risk ratios (RRs) and 95% confidence intervals (CIs).RESULTS:We included 33 trials (118 863 patients) evaluating intermittent auscultation with Pinard stethoscope/handheld Doppler (IA), cardiotocography (CTG), computerized cardiotocography (cCTG), CTG with fetal scalp lactate (CTG-lactate), CTG with fetal scalp pH analysis (CTG-FBS), CTG with fetal pulse oximetry (FPO-CTG), CTG with fetal heart electrocardiogram (CTG-STAN) and their combinations. Intermittent auscultation reduced the risk of emergency cesarean deliveries compared with other types of surveillance (IA v. CTG: RR 0.83, 95% CI 0.72–0.97; IA v. CTG-FBS: RR 0.71, 95% CI 0.63–0.80; IA v.CTG-lactate: RR 0.77, 95% CI 0.64–0.92; IA v. FPO-CTG: RR 0.75, 95% CI 0.65–0.87; IA v.FPO-CTG-FBS: RR 0.81, 95% CI 0.67–0.99; cCTG-FBS v. IA: RR 1.21, 95% CI 1.04–1.42), except STAN-CTG-FBS (RR 1.17, 95% CI 0.98–1.40). There was a similar reduction observed for emergency cesarean deliveries for fetal distress. None of the evaluated methods was associated with a reduced risk of neonatal acidemia, neonatal unit admissions, Apgar scores or perinatal death.INTERPRETATION:Compared with other types of fetal surveillance, intermittent auscultation seems to reduce emergency cesarean deliveries in labour without increasing adverse neonatal and maternal outcomes.

Cesarean delivery is the most common surgical procedure worldwide, performed to expedite delivery and avoid neonatal complications. Fetal surveillance is routinely offered to patients in labour to reduce the risk of adverse neonatal outcomes, as well as the risk of unnecessary emergency cesarean deliveries and other maternal interventions. Fetal surveillance aims to detect intrapartum hypoxia from acute or subacute adverse events in labour requiring medical intervention and to reduce the risk of serious complications such as neonatal cerebral palsy, hypoxic–ischemic encephalopathy or stillbirth.Monitoring the fetal heart rate to detect intrapartum hypoxia using simple surveillance techniques, such as the Pinard stethoscope, has been practised for decades.1 Over the last 50 years, several newer surveillance methods have been evaluated, with varied uptake in practice.2 Cardiotocography (CTG) remains the most common surveillance method used in high-risk pregnancies.3 However, given its limited accuracy, many researchers have evaluated its use in combination with other surveillance methods, such as fetal heart electrocardiogram (STAN), fetal scalp pH analysis (FBS) or fetal pulse oximetry (FPO), and with computer-aided decision models (cCTG) to improve its diagnostic value.46 Despite extensive investment in clinical research, the overall effectiveness of such methods in improving maternal and neonatal outcomes remains debatable as stillbirth rates have plateaued worldwide, while cesarean delivery rates continue to rise.7,8Existing meta-analyses evaluating different intrapartum fetal surveillance methods remain limited to head-to-head comparisons of monitoring techniques, without a comprehensive assessment of their effectiveness in improving maternal and neonatal pregnancy outcomes.4,913 We conducted a systematic review of randomized trials and a network meta-analysis to evaluate the effectiveness of all available fetal surveillance methods in improving maternal and neonatal outcomes.  相似文献   
440.
Gene signatures have been developed for estrogen receptor-positive breast cancer to complement pathological factors in providing prognostic information. The 70-gene and the 21-gene signatures identify patients who may not require adjuvant chemotherapy. Gene signatures in triple-negative disease and HER2-positive disease have not been fully developed yet, although studies demonstrate heterogeneity within these subgroups. Further research is needed before genotyping will help in making clinical decisions in triple-negative and HER2-positive disease. Molecular subtyping of breast cancer led to define luminal, basal, and HER2-enriched subtypes, which have specific clinical behavior. This approach may lead to identify new subgroups requiring specific therapies. Standardization of techniques will be required to translate investigations to the clinic.  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