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   1007篇
  免费   90篇
  国内免费   3篇
耳鼻咽喉   19篇
儿科学   82篇
妇产科学   23篇
基础医学   109篇
口腔科学   59篇
临床医学   105篇
内科学   200篇
皮肤病学   9篇
神经病学   22篇
特种医学   17篇
外科学   196篇
综合类   35篇
一般理论   1篇
预防医学   57篇
眼科学   53篇
药学   79篇
肿瘤学   34篇
  2023年   8篇
  2022年   28篇
  2021年   37篇
  2020年   17篇
  2019年   41篇
  2018年   49篇
  2017年   32篇
  2016年   24篇
  2015年   32篇
  2014年   36篇
  2013年   38篇
  2012年   58篇
  2011年   74篇
  2010年   32篇
  2009年   30篇
  2008年   52篇
  2007年   66篇
  2006年   57篇
  2005年   38篇
  2004年   34篇
  2003年   32篇
  2002年   34篇
  2001年   17篇
  2000年   20篇
  1999年   14篇
  1998年   5篇
  1997年   5篇
  1996年   9篇
  1995年   5篇
  1994年   4篇
  1992年   19篇
  1991年   16篇
  1990年   12篇
  1989年   10篇
  1988年   6篇
  1985年   6篇
  1984年   4篇
  1983年   5篇
  1982年   4篇
  1981年   8篇
  1979年   11篇
  1978年   5篇
  1976年   3篇
  1975年   8篇
  1974年   9篇
  1973年   11篇
  1972年   6篇
  1970年   3篇
  1967年   3篇
  1966年   3篇
排序方式: 共有1100条查询结果,搜索用时 15 毫秒
11.
Titanium dioxide engineered nanoparticles (nano-TiO2) are widely used in the manufacturing of a number of products. Due to their size (<100 nm), when inhaled they may be deposited in the distal lung regions and damage Clara cells. We investigated the mechanisms by which short-term (1-h) incubation of human airway Clara-like (H441) cells to nano-TiO2 (6 nm in diameter) alters the ability of H441 cells to adhere to extracellular matrix. Our results show that 1 h post-incubation, there was a 3-fold increase of extracellular H2O2, increased intracellular oxidative stress as demonstrated by 2′,7′-dichlorodihydrofluorescein diacetate (DCFH-DA) oxidation, and a 5-fold increase of phosphor-ERK1/2 as measured by Western blotting. These changes were accompanied by a 25% decrease of H441 adherence to fibronectin (p < 0.05 compared to vehicle incubated H441 cells). Pretreatment with the ERK1/2 inhibitor U0126 for 3 h, partially prevented this effect. In conclusion, short-term exposure of H441 cells to nano-TiO2 appears to reduce adherence to fibronectin due to oxidative stress and activation of ERK1/2.  相似文献   
12.
Electrical and magnetic sensors can be lithographically fabricated on top of diamond substrates and encapsulated in a protective layer of chemical vapor deposited single crystalline diamond. This process when carried out on single crystal diamond anvils employed in high pressure research is termed as designer diamond anvil fabrication. These designer diamond anvils allow researchers to study electrical and magnetic properties of materials under extreme conditions without any possibility of damaging the sensing elements. We describe a novel method for the fabrication of designer diamond anvils with the use of maskless lithography and chemical vapor deposition in this paper. This method can be utilized to produce diamond based sensors which can function in extreme environments of high pressures, high and low temperatures, corrosive and high radiation conditions. We demonstrate applicability of these diamonds under extreme environments by performing electrical resistance measurements during superconducting transition in rare earth doped iron-based compounds under high pressures to 12 GPa and low temperatures to 10 K.  相似文献   
13.
Objective: To evaluate the relationship between first and second trimester maternal serum-free β-hCG and the risk of spontaneous preterm delivery (PTD).

Study design: This was a case-control study of women evaluated and delivered at our institution from 2011 to 2015. Spontaneous PTD was defined as delivery before 37 weeks due to spontaneous preterm labor or premature rupture of membranes. Patient with multifetal gestation and those with medically indicated term or PTD were excluded.

Results: Of 877 women meeting the inclusion criteria, 173 delivered preterm and 704 delivered at term, and 8.1% had high free β-hCG in one or both trimesters. High maternal first and/or second trimester free β-hCG (≥95th percentile) was associated with lower rates of PTD. Thirty-two women with high free β-hCG in both first and second trimesters delivered at term. Gestational age at delivery and birth weights were lower in women who did not have high free β-hCG in any trimester. Low free β-hCG (≤5th percentile) in either trimester was not associated with an increased or decreased likelihood of PTD. Logistic regression demonstrated an independent association of high free β-hCG (≥95th percentile) with a reduced likelihood of PTD. Stratified analysis revealed a stronger impact of this association in women with no prior history of PTD.

Conclusions: High free β-hCG, in the absence of risk factors for medically indicated PTD, is associated with a reduced likelihood of spontaneous PTD and may represent a marker indicating lower risk.  相似文献   

14.
Congenital factor VII deficiency is an autosomal recessive serious disorder of blood coagulation with wide genotypic and phenotypic variations. The clinical presentation can vary from asymptomatic patients to patients with major bleedings in severe deficiency (factor VII <1%). Investigations show prolonged PT and low factor VII. Treatment modalities include FFP and repeated recombinant factor VII infusions. We hereby report the first successful LRLT for factor VII deficiency in an infant, the first‐ever youngest baby reported worldwide. A six‐month‐old male child presented with easy bruisability, ecchymotic patches, hematuria, and convulsions. CT of the head showed subdural hemorrhage, which was treated conservatively. He had markedly increased PT (120 s) with normal platelets, and aPTT with factor VII level <1%. Despite the treatment by rFVIIa administration weekly, which was very expensive, he still had repeated life‐threatening bleeding episodes. LRLT was performed with mother as the donor, whose factor VII level was 57%. A factor VII infusion plan for pre‐, intra‐ and postoperative periods was formulated and TEG followed. Postoperatively, his factor VII started increasing from third day and was 38% on 24th day with PT <14 s. He had uneventful intraoperative and postoperative courses. LT is a safe and definite cure for factor VII deficiency.  相似文献   
15.
Radiofrequency ablation for cure of atrial flutter   总被引:1,自引:0,他引:1  
Abstract Background: Atrial flutter is a common arrhythmia which frequently recurs after cardioversion and is relatively difficult to control with antiarrhythmic agents.
Aims: To evaluate the success rate, recurrence rate and safety of radiofrequency (RF) ablation for atrial flutter in a consecutive series of patients with drug refractory chronic or paroxysmal forms of the arrhythmia.
Methods: Electrophysiologic evaluation of atrial flutter included activation mapping with a 20 electrode halo cadieter placed around the tricuspid annulus and entrainment mapping from within the low right atrial isthmus. After confirmation of the arrhythmia mechanism with these techniques, an anatomic approach was used to create a linear lesion between the inferior tricuspid annulus and the eustachian ridge at the anterior margin of the inferior vena cava. In order to demonstrate successful ablation, mapping techniques were employed to show that bi-directional conduction block was present in the low right atrial isthmus.
Results: Successful ablation was achieved in 26/27 patients (96%). In one patient with a grossly enlarged right atrium, isthmus block could not be achieved. Of the 26 patients with successful ablation, mere has been one recurrence of typical flutter (4%) during a mean follow-up period of 5.5±2.7 months. This patient underwent a successful repeat ablation procedure. Of eight patients with documented clinical atrial fibrillation (in addition to atrial flutter) prior to the procedure, five continued to have atrial fibrillation following the ablation. There were no procedural complications and all patients had normal AV conduction at the completion of the ablation.
Conclusions: RF ablation is a highly effective and safe procedure for cure of atrial flutter. In patients with chronic or recurrent forms of atrial flutter RF ablation should be considered as a first line therapeutic option.  相似文献   
16.
Background: Catheter ablation of the atrioventricular (AV) junction using stored direct current (DC) energy from a standard DC Cardioverter defibrillator was first reported in 1982. Since then many patients have been treated using this procedure for refractory supraventricular arrhythmias, usually atrial fibrillation and flutter. Undesirable thermal effects such as barotrauma and arcing are largely responsible for complications associated with the use of DC energy. This report details our experience of catheter ablation of the AV junction using radiofrequency (RF) energy in a series of 30 consecutive patients. Methods: RF ablations were performed using steerable Mansfield (Webster Laboratories) 4 mm tipped electrodes and locally assembled RF energy delivery system. Results: The procedure was successful in 27/30 (90%) patients using RF energy, while three patients required DC energy to achieve successful AV junction ablation. General anaesthesia was required in nine patients, six of whom required this for cardioversion to sinus rhythm so that an adequate His Bundle spike could be recorded and three for DC ablation. Dual chamber permanent pacemakers with automatic mode switching were implanted in four patients who had paroxysmal atrial fibrillation or flutter and the remainder had ventricular rate responsive pacemakers. Conclusions: In patients with drug refractory paroxysmal atrial fibrillation and flutter and in patients with established atrial fibrillation where control of the ventricular rate is difficult, catheter ablation of the AV junction using RF energy is a safe and effective procedure with a high success rate.  相似文献   
17.
Proceedings of the National Academy of Sciences, India Section B: Biological Sciences - Ocimum, an important commercial aromatic crop, is well known for the industrially acclaimed essential oil. In...  相似文献   
18.
19.

Objective

Breast cancer is the most common cancer among women worldwide. Given the advances in extending survival, the number of recently diagnosed breast cancer patients and longer-term breast cancer survivors is growing. The goals of this study were to better understand (1) perceptions of provider cancer recurrence risk communication, (2) perceived risk of breast cancer recurrence in cancer patients and survivors, and (3) accuracy of perceived risk.

Methods

A survey was conducted on women with a prior breast cancer (n = 141).

Results

Approximately 40% of women perceived that providers had not talked about their breast cancer recurrence risk; although only 1 person reported not wanting a physician to talk to her about her risk. Women were largely inaccurate in their assessments of risk. Greater worry, living in a rural area, and longer time since diagnosis were associated with greater inaccuracy. Women tended to think about distal recurrence of cancer as often of local recurrence.

Conclusions

Perceived risk of breast cancer recurrence was inaccurate, and patients desired more communication about recurrence risk.

Practice implications

Consistent with findings from other studies, greater efforts are needed to improve the communication of cancer recurrence risk to patients. Attention should be paid to those from rural areas and to distal cancer recurrence in women with a previous history of breast cancer.  相似文献   
20.
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