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   537篇
  免费   33篇
  国内免费   1篇
耳鼻咽喉   3篇
儿科学   14篇
妇产科学   3篇
基础医学   54篇
口腔科学   12篇
临床医学   67篇
内科学   97篇
皮肤病学   13篇
神经病学   97篇
特种医学   19篇
外国民族医学   1篇
外科学   65篇
综合类   16篇
预防医学   33篇
眼科学   13篇
药学   44篇
中国医学   3篇
肿瘤学   17篇
  2024年   2篇
  2023年   5篇
  2022年   23篇
  2021年   23篇
  2020年   10篇
  2019年   19篇
  2018年   15篇
  2017年   18篇
  2016年   15篇
  2015年   15篇
  2014年   36篇
  2013年   38篇
  2012年   46篇
  2011年   46篇
  2010年   31篇
  2009年   18篇
  2008年   42篇
  2007年   29篇
  2006年   22篇
  2005年   20篇
  2004年   36篇
  2003年   20篇
  2002年   12篇
  2001年   2篇
  2000年   2篇
  1999年   2篇
  1998年   3篇
  1997年   2篇
  1996年   2篇
  1995年   2篇
  1994年   1篇
  1991年   1篇
  1990年   1篇
  1989年   1篇
  1988年   1篇
  1987年   2篇
  1985年   2篇
  1984年   3篇
  1976年   1篇
  1975年   1篇
  1973年   1篇
排序方式: 共有571条查询结果,搜索用时 15 毫秒
31.
Summary: Culdocentesis was carried out in 92 suspected cases of ectopic pregnancy and was positive in 90%. Laparotomy confirmed the accuracy of culdocentesis in 97.5% of the cases of acute tubal rupture, 87.5% of tubal abortions and 80% of 'intact' tubal pregnancies.  相似文献   
32.
Anticoagulation is usually indicated in patients receiving continuous renal replacement therapy (CRRT) to prevent clotting of the extra-corporeal circuit. While heparin is the most frequently used anticoagulant, regional citrate anticoagulation is becoming the preferred choice in those patients at high risk for bleeding. However, it has been widely claimed that to avoid citrate toxicity, CRRT with citrate anticoagulation should utilize diffusive clearance (e.g., continuous venovenous hemodialysis). We studied citrate clearance in five children who received citrate anticoagulation during CRRT with a COBE PRISMA machine and an M-60 (AN-69) filter. The blood flow rate ranged from 50 to 150 ml/min (2.1-8.0 ml/kg per min). Citrate was infused in the circuit circulation as an acid citrate dextrose (ACD) solution at a rate of 1.6-3.7% of the blood flow rate to maintain the circuit ionized calcium (iCa) <0.5 mmol/l. Calcium-free replacement fluid with reduced alkali (NaHCO3 20 mEq/l) was infused in pre-filter mode at a rate of 1,800-2,000 ml/h per 1.73 m(2). In a separate central line, CaCl2 (0.8%) was infused (rate 25-50% of ACD infusion) to maintain systemic iCa between 1.0 and 1.3 mmol/l. Citrate concentration was measured using an enzymatic assay. Total CRRT duration was 1,224 h. Twenty-four filters were changed due to clotting, with a mean filter life of 51 h. Mean (range) citrate levels (mmol/l) were (1) before initiating CRRT ( n=2): patient baseline 0.13 (0.1-0.15), (2) during CRRT ( n=7): circuit 4.54 (3.95-6.25), effluent 4.31 (3.95-5.46), and patient 0.69 (0.30-1.13). Sieving coefficients for urea and citrate were 0.88-0.97 and 0.88-1.0, respectively. Citrate clearance (31-38 ml/min per 1.73 m(2)) was similar to that of urea (31-38 ml/min per 1.73 m(2)), and when evaluated in two patients, remained unchanged after substituting half of the convective clearance [continuous venovenous hemofiltration (CVVH)] by diffusive clearance [continuous venovenous hemodiafiltration (CVVHDF)]. The post-filter citrate load (mean+/-SD) delivered to the five patients during CRRT was 1.06+/-0.62 mmol/kg per hour. With the exception of alkalosis in one patient, no other complications were observed. Renal function recovered in all patients. We conclude that citrate anticoagulation in children is feasible, effective, and safe. Sufficient citrate clearance to prevent its toxic accumulation is achieved by convective clearance (CVVH) alone and diffusive clearance (CVVHDF) does not appear to be mandatory when utilizing citrate anticoagulation during CRRT.  相似文献   
33.
Vimal RL 《Vision research》2002,42(5):599-611
In this study, we have compared foveal SF discriminations for luminance and color-defined stimuli using two different tasks (criteria): in criterion-A, the discrimination is based on spatial (size of the stimuli) and/or spatial frequency; in criterion-B, it is based on apparent motion (contraction/expansion). We used high contrast (75%) spatially localized D6 stimuli and cosine gratings (0.25-9.5 cpd). The SF discrimination was measured by the method of constant stimuli with a two-interval forced-choice procedure. Data show that: (i) for criterion-A, the discrimination thresholds for color stimuli were lower than that for luminance stimuli at low SFs, but similar or higher at higher SFs; for criterion-B, the thresholds to chromatic stimuli were higher than that to achromatic stimuli for all SFs; (ii) SF discrimination was best at inter-stimulus-interval (ISI) of about 200 ms for color stimuli and at ISI of 0 ms for luminance stimuli; (iii) SF discrimination got better with stimulus duration and reached to plateau at 200 ms (or more) for color stimuli and at 67 ms (or more) for luminance stimuli; (iv) SF discrimination threshold (mean Delta(f)=0.19 octaves) is about one-tenth of the full bandwidth (mean=1.96 octaves) of SF tuned mechanisms and is in hyperacuity range; both (discrimination and hyperacuity) can be explained by the relative activities within a population of tuned mechanisms. We conclude that color and luminance SF discrimination thresholds have a different SF dependence. While color appears to perform better than luminance vision at low SFs, this effect is lost or even reversed at high SFs. Data imply that color and form interact, but color and motion are largely segregated (i.e. they weakly interact).  相似文献   
34.
The synergistic effects of nicorandil (KATP-channel opener) and amlodipine (calcium-channel blocker) on heart mitochondrial enzymes and the mitochondrial antioxidant defence system was examined on isoproterenol-induced myocardial infarction in rats. The rats given isoproterenol (150 mg kg(-1) daily, i.p.) for two days showed significant changes in marker enzymes, mitochondrial enzymes and the mitochondrial defence system. Pre-co-treatment with nicorandil (2.5 mg kg(-1) daily, p.o.) and amlodipine (5.0 mg kg(-1) daily, p.o.) for 3 days significantly prevented these alterations and restored enzyme activity to near normal. These findings demonstrate the protective and synergistic effect of nicorandil and amlodipine in combination against isoproterenol-induced cardiac damage.  相似文献   
35.
The authors examined the role of impaired glucose metabolism in the pathophysiology of tardive dyskinesia in schizophrenic patients with and without persistent TD. Glucose tolerance and insulin levels were determined in 86 patients with persistent tardive dyskinesia and in 108 patients without tardive dyskinesia. Dyskinesias were assessed by the abnormal involuntary movement scale (AIMS) and extrapyramidal symptoms by the Simpson--Angus rating scale (SARS). Fasting blood glucose levels were significantly lower while the first and second hour glucose levels did not reveal any differences in patients with tardive dyskinesia compared with those without tardive dyskinesia. Insulin levels did not differ in these two groups. Our cross-sectional epidemiological study does not suggest hyperglycemia to be a risk factor for tardive dyskinesia. However, prospective long-term studies with multiple assessment points are needed to clarify the role of glucose metabolism in the development of tardive dyskinesia.  相似文献   
36.
Recently, we have shown that a single high dose of the adrenal steroid precursor hormone deoxycorticosterone (DOC) has potent anticonvulsant effects in 15-day-old rats. To better define the actions of DOC, the present study established dose-, time-, age-, and sex-response curves for the anticonvulsant actions of DOC. Methods. Dose- and time-response studies were done using two different seizure models: (1) maximal pentylenetetrazol seizures (MMT) and (2) maximal electroconvulsive shock (MES) seizures. Subsequently, age- and sex-response studies were done using MMT seizures and two different DOC doses, one low (nonsedating) and one high (sedating). Results. In dose-response studies, DOC suppressed MMT seizures with an ED(50) of about 5 mg/kg (sc). Higher doses were necessary to suppress MES seizures, where the ED(50) was about 20 mg/kg. In time-response studies, DOC's effects were rapid in onset. Complete suppression of seizures was seen by 5 min in the MES model and by 15 min in the MMT model. In developmental studies, both a low nonsedating and a high sedating dose of DOC suppressed MMT seizures in neonatal, infant, weanling, and juvenile rats of either sex. The suppressive effects of low-dose DOC were lost after puberty, however. The suppressive effects of high-dose DOC also declined after puberty, especially in males. Conclusion. DOC has significant anticonvulsant actions that occur in prepubertal, but not postpubertal subjects. DOC might have clinical importance in the future treatment of childhood seizure disorders.  相似文献   
37.
Urinary type calcium hydrogen phosphate dihydrate (CHPD) or Brushite crystals were grown by the single diffusion gel technique in silica hydro-gels. The gel framework acts as a three dimensional crucible in which the crystal nuclei are delicately held in the position of their formation and nutrients are supplied for their growth. This technique can be utilized as a simplified screening model to study the growth and dissolution of urinary stones in vitro. The action of the putatively litholytic medicinal plants Tribulus terrestris and Bergenia ligulata on the growth of CHPD crystals was studied . The effects of artificial reference urine (ARU) and human urine (HU), along with the plant extracts, are also reported. Attempts were made to understand the role of these inhibitors on urinary crystal formation. HU, ARU, extracts of B. ligulata and T. terrestris exhibit appreciable amounts of inhibition, but B.ligulata and T.terrestris with ARU and HU do not show inhibition at all.  相似文献   
38.
Edwards HE  Vimal S  Burnham WM 《Epilepsia》2005,46(12):1888-1897
PURPOSE: The mechanisms that mediate the acute anticonvulsant effects of deoxycorticosterone (DOC) were investigated in young rats. METHODS: Fifteen-day-old rats were pretreated with a variety of compounds, including (a) agonists of the receptors that bind DOC (mineralocorticoid receptors); (b) the DOC 5alpha- and 5alpha-3alpha-reduced metabolites, plus agonists that bind the receptors of the 5alpha-reduced metabolite of DOC (progesterone receptors); and (c) DOC itself in the presence and absence of metabolism and receptor blockers. Fifteen minutes later, pentylenetetrazol (PTZ) was administered, and maximal pentylenetetrazol (MMT) seizure responses were scored. RESULTS: Agonists of mineralocorticoid receptors increased the latency to forelimb flexion in PTZ seizures and sometimes suppressed the seizures completely. At low, nonconvulsant doses, spironolactone (a mineralocorticoid-receptor antagonist) blocked the anticonvulsant effects of a nonsedating, but not a sedating, dose of DOC. These data suggest the possible direct involvement of mineralocorticoid receptors in the anticonvulsant effects of DOC. At low, nonconvulsant doses, finasteride (which blocks the metabolism of DOC) partially blocked the protective effects of DOC, suggesting the contribution of metabolites to the anticonvulsant actions of DOC. Dihydrodeoxycorticosterone (DHDOC)-the first metabolite of DOC, an agonist at progesterone receptors, and an allosteric modulator of the gamma-aminobutyric acid (GABA)(A) receptor-and tetrahydrodeoxycorticosterone, a secondary metabolite of DOC and an allosteric modulator of the GABA(A) receptor, both blocked MMT seizures. CONCLUSIONS: These findings suggest that both DOC and its metabolites may contribute to the anticonvulsant effects seen in young rats, perhaps acting via interactions with several different receptors.  相似文献   
39.
A prospective study on 27 cases of chronic dacryocystitis was done to see the outcome of management by End-DCR in Indian population and to look for advantages or disadvantages over Ext-DCR from available datas in literature All cases were diagnosed clinically by regurgitation test and lacrimal syringing In selected cases Jones dye test, dacryocystogram and CT scan of nose and paranasal sinuses (PNS) was done to confirm the site of obstruction and find out the cause Cases having hyperlacrumation due to other causes and epiphora due to presaccal stenosis were excluded Cause of NLD obstruction was atrophic rhinitis (4 cases), chronic sinusitis (4 cases), enlarged agger nasi cells (4 cases), faciomaxillary injury (1 case) and unknown in rest of cases All cases were treated by End-DCR under local anaesthesia Concommitent nose and PNS surgeries were done in selected cases where it was supposed to be the cause Average follow-up was from 3 months to 1 year Primary success rate was 92 6% and after revision in two cases final success was 96% Success rate was 100% in cases of atrophie rhinitis Major complication was not found in any case Our result of End-DCR was as good as Ext-DCR Our results of End-DCR are better than those who had used lacnmal stent, lasers, microdebriders, dacryoendoscope and electrocautery It was finally concluded that end-DCR by using simple instruments is a safe and effective procedure  相似文献   
40.
Atrophic rhinitis is a chronic inflammatory disease of the nose, which is more common in India. Chronic dacryocystitis is its rare complication. The authors found four cases of chronic dacryocystitis from March 2002 to October 2003 due to atrophic rhinitis. It was diagnosed clinically by the regurgitation test and lacrimal syringing. These cases were treated conservatively for a period of six weeks to make the nasal mucosa healthier and were then subjected to endoscopic dacryocystorhinostomy (end-DCR) under local anaesthesia. The procedure was found to be more difficult due to bleeding and the healing time was prolonged as compared to other cases of end-DCR. After one to one and half years of follow-up the primary success rate was 75 per cent but after revision surgery in one case, all cases were successful. Hence it was concluded that atrophic rhinitis is no more a contraindication for end-DCR. However, meticulous initial preparation and post-operative follow-up is necessary to improve the result.  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