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   1988篇
  免费   335篇
  国内免费   8篇
耳鼻咽喉   2篇
儿科学   59篇
妇产科学   284篇
基础医学   116篇
口腔科学   27篇
临床医学   862篇
内科学   305篇
皮肤病学   51篇
神经病学   25篇
特种医学   236篇
外科学   58篇
综合类   70篇
预防医学   125篇
眼科学   6篇
药学   47篇
肿瘤学   58篇
  2023年   44篇
  2021年   7篇
  2020年   35篇
  2019年   18篇
  2018年   59篇
  2017年   92篇
  2016年   77篇
  2015年   101篇
  2014年   102篇
  2013年   102篇
  2012年   40篇
  2011年   68篇
  2010年   104篇
  2009年   102篇
  2008年   51篇
  2007年   51篇
  2006年   44篇
  2005年   29篇
  2004年   27篇
  2003年   36篇
  2002年   26篇
  2001年   46篇
  2000年   18篇
  1999年   50篇
  1998年   94篇
  1997年   109篇
  1996年   106篇
  1995年   94篇
  1994年   63篇
  1993年   50篇
  1992年   31篇
  1991年   31篇
  1990年   22篇
  1989年   40篇
  1988年   44篇
  1987年   28篇
  1986年   41篇
  1985年   35篇
  1984年   18篇
  1983年   18篇
  1982年   21篇
  1981年   14篇
  1980年   16篇
  1979年   9篇
  1978年   18篇
  1977年   18篇
  1976年   18篇
  1975年   20篇
  1973年   6篇
  1972年   6篇
排序方式: 共有2331条查询结果,搜索用时 15 毫秒
101.
102.

Background

Gloriosa superba produces an array of alkaloids including colchicine, a compound of interest in the treatment of various diseases. The tuber of Gloriosa superba is a rich source of colchicine which has shown anti-gout, anti-inflammatory, and anti-tumor activity. However, this promising compound remains expensive and Gloriosa superba is such a good source in global scale. Increase in yield of naturally occurring colchicine is an important area of investigation.

Materials and Methods

The effects of inoculation by four arbuscular mycorrhizal (AM), fungi, Glomus mossae, Glomus fasciculatum, Gigaspora margarita and Gigaspora gilmorei either alone or supplemented with P-fertilizer, on colchicine concentration in Gloriosa superba were studied. The concentration of colchicine was determined by high-performance thin layer chromatography.

Results

The four fungi significantly increased concentration of colchicine in the herb. Although there was significant increase in concentration of colchicine in non-mycorrhizal P-fertilized plants as compared to control, the extent of the increase was less compared to mycorrhizal plants grown with or without P-fertilization. This suggests that the increase in colchicine concentration may not be entirely attributed to enhanced P-nutrition and improved growth. Among the four AM fungi Glomus mossae was found to be best. The total colchicine content of plant (mg / plant) was significantly high in plants inoculated with Glomus mossae and 25 mg kg−1phosphorus fertilizer (348.9 mg /plant) while the control contain least colchicine (177.87 mg / plant).

Conclusion

The study suggests a potential role of AM fungi in improving the concentration of colchicine in Gloriosa superba tuber.  相似文献   
103.
104.
BackgroundProgrammed death ligand 1 (PD-L1) contributes to tumor immunosuppression and is upregulated in aggressive meningiomas. We performed a phase II study of nivolumab, a programmed death 1 (PD-1) blocking antibody among patients with grade ≥2 meningioma that recurred after surgery and radiation therapy.MethodsTwenty-five patients received nivolumab (240 mg biweekly) until progression, voluntary withdrawal, unacceptable toxicity, or death. Tumor mutational burden (TMB) and quantification of tumor-infiltrating lymphocytes (TIL) were evaluated as potential immunocorrelative biomarkers. Change in neurologic function was prospectively assessed using the Neurologic Assessment in Neuro-Oncology (NANO) scale.ResultsEnrolled patients had multiple recurrences including ≥3 prior surgeries and ≥2 prior courses of radiation in 60% and 72%, respectively. Nivolumab was well tolerated with no unexpected adverse events. Six-month progression-free survival (PFS-6) rate was 42.4% (95% CI: 22.8, 60.7) and the median OS was 30.9 months (95% CI: 17.6, NA). One patient achieved radiographic response (ongoing at 4.5 years). TMB was >10/Mb in 2 of 15 profiled tumors (13.3%). Baseline TIL density was low but increased posttreatment in 3 patients including both patients with elevated TMB. Most patients who achieved PFS-6 maintained neurologic function prior to progression as assessed by NANO.ConclusionNivolumab was well tolerated but failed to improve PFS-6, although a subset of patients appeared to derive benefit. Low levels of TMB and TIL density were typically observed. NANO assessment of neurologic function contributed to outcome assessment. Future studies may consider rationally designed combinatorial regimens.  相似文献   
105.
Three glutamic acid analogues, N-methyl-D-aspartic (NMDA), quisqualic (QQ), and kainic (KAI) acids were applied topically to the ventral surface of the medulla (VMS) in paralyzed, vagotomized and carotid sinus denervated cats hyperventilated to apnea. Respiratory and vasomotor effects were assessed by changes in phrenic nerve activity and systemic arterial blood pressure. All three agents to varying degrees raised systemic blood pressure, but only NMDA consistently initiated phrenic nerve activity at pCO2 levels below that observed in control trials. KAI and QQ raised blood pressure even in those animals in which they had little effect on initiating phrenic nerve activity. Furthermore, respiratory responses were obtained from localized areas on VMS, namely the intermedio-caudal zone (I-C areas); whereas blood pressure elevations could be obtained from wider VMS areas including the rostral zone (R areas). In addition, the effects of the three amino acids on blood pressure were quantitatively different with KAI causing much greater increases in blood pressure than QQ or NMDA. The respiratory and vasomotor effects of NMDA and QQ were blocked by the use of 2-amino-5-phosphonovaleric acid and L-glutamic acid diethylester, their respective antagonists. The results suggest that neurons in the VMS which cause respiratory and vasomotor responses are not identical. Cells containing receptors stimulated by NMDA predominantly increase respiration, whereas cells containing receptors excited by KAI are more effective in eliciting vasomotor responses.  相似文献   
106.
At the 2013 Academic Emergency Medicine global health consensus conference, a breakout session to develop a research agenda for resuscitation was held. Two articles are the result of that discussion. This second article addresses data collection, management, and analysis and regionalization of postresuscitation care, resuscitation programs, and research examples around the world and proposes a strategy to strengthen resuscitation research globally. There is a need for reliable global statistics on resuscitation, international standardization of data, and development of an electronic standard for reporting data. Regionalization of postresuscitation care is a priority area for future research. Large resuscitation clinical research networks are feasible and can give valuable data for improvement of service and outcomes. Low‐cost models of population‐based research, and emphasis on interventional and implementation studies that assess the clinical effects of programs and interventions, are needed to determine the most cost‐effective strategies to improve outcomes. The global challenge is how to adapt research findings to a developing world situation to have an effect internationally.  相似文献   
107.
For several decades, there has been increasing interest in the possible use of resveratrol as a preventative agent in cardiovascular disease. Resveratrol exerts numerous effects on adipocyte, hepatocyte, and endothelial cell development and function. Many investigations have demonstrated the ability of resveratrol to regulate the adipocyte lifecycle, lipid synthesis, and improve hepatic lipid metabolism. Resveratrol has numerous vascular protective effects on endothelial tissue, including its antiplatelet activity. Resveratrol also reduces intracellular oxidative stress. Animal models of obesity and cardiovascular diseases have yielded important contributions to our understanding of the effects of resveratrol on the vasculature and the risk for pathology. In limited human studies, resveratrol reduces the release of proinflammatory cytokines and improves systemic glucose and insulin regulation and decreases cellular oxidative stress. Therefore, resveratrol has significant potential as both a prophylactic and treatment agent. However additional studies are required to more completely characterize its impacts on human physiology and its benefits in the setting of disease.  相似文献   
108.
109.
Objective  To determine which interventions for managing placenta accreta were associated with reduced maternal morbidity.
Design  Retrospective cohort study.
Setting  Two tertiary care teaching hospitals in Utah.
Population  All identified cases of placenta accreta from 1996 to 2008.
Methods  Cases of placenta accreta were identified using standard ICD-9 codes for placenta accreta, placenta praevia, and caesarean hysterectomy. Medical records were then abstracted for maternal medical history, hospital course, and maternal and neonatal outcomes. Maternal and neonatal complications were compared according to antenatal suspicion of accreta, indications for delivery, preoperative preparation, attempts at placental removal before hysterectomy, and hypogastric artery ligation.
Main outcome measures  Early morbidity (prolonged maternal intensive care unit admission, large volume of blood transfusion, coagulopathy, ureteral injury, or early re-operation) and late morbidity (intra-abdominal infection, hospital re-admission, or need for delayed re-operation).
Results  Seventy-six cases of placenta accreta were identified. When accreta was suspected, scheduled caesarean hysterectomy without attempting placental removal was associated with a significantly reduced rate of early morbidity compared with cases in which placental removal was attempted (67 versus 36%, P = 0.038). Women with preoperative bilateral ureteric stents had a lower incidence of early morbidity compared with women without stents (18 versus 55%, P = 0.018). Hypogastric artery ligation did not reduce maternal morbidity.
Conclusions  Scheduled caesarean hysterectomy with preoperative ureteric stent placement and avoiding attempted placental removal are associated with reduced maternal morbidity in women with suspected placenta accreta.  相似文献   
110.
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