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   32536篇
  免费   1669篇
  国内免费   410篇
耳鼻咽喉   232篇
儿科学   775篇
妇产科学   160篇
基础医学   2719篇
口腔科学   85篇
临床医学   4871篇
内科学   8399篇
皮肤病学   79篇
神经病学   4474篇
特种医学   1101篇
外科学   3183篇
综合类   3363篇
预防医学   800篇
眼科学   891篇
药学   2022篇
  10篇
中国医学   935篇
肿瘤学   516篇
  2023年   422篇
  2022年   853篇
  2021年   1228篇
  2020年   1055篇
  2019年   1126篇
  2018年   1185篇
  2017年   1048篇
  2016年   921篇
  2015年   1057篇
  2014年   2143篇
  2013年   2193篇
  2012年   1599篇
  2011年   1821篇
  2010年   1468篇
  2009年   1525篇
  2008年   1546篇
  2007年   1467篇
  2006年   1386篇
  2005年   1077篇
  2004年   947篇
  2003年   758篇
  2002年   691篇
  2001年   591篇
  2000年   496篇
  1999年   452篇
  1998年   419篇
  1997年   447篇
  1996年   460篇
  1995年   365篇
  1994年   332篇
  1993年   312篇
  1992年   302篇
  1991年   248篇
  1990年   204篇
  1989年   188篇
  1988年   191篇
  1987年   168篇
  1986年   159篇
  1985年   218篇
  1984年   239篇
  1983年   132篇
  1982年   168篇
  1981年   140篇
  1980年   145篇
  1979年   106篇
  1978年   77篇
  1977年   91篇
  1976年   93篇
  1975年   76篇
  1973年   65篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
李明秋  童荣原 《肿瘤》1995,15(6):435-437
作者对15例贲门癌患者行根治术同时,采用食管残胃间插入带蒂空肠并附加贲门再造术,通过SPECT胃食管返流指数测定、食管下端pH检测及返流症状评定方法,并与单纯食管胃套叠吻合术进行随机对比分析,证明该术式具有单向住屏障作用,能有效地预防返流性食管炎的发生。  相似文献   
62.
The distribution and source of a galanin-like innervation of rat salivary glands has been examined. Additionally, submandibular and sublingual acinar cell membrane responses to galanin or a cholinergic agonist were studied. Galanin-immunoreactive fibers were observed throughout the submandibular and sublingual glands in association with ducts and acini. A subset of submandibular ganglion cells expresses galanin immunoreactivity. Parasympathectomy resulted in a marked decrease in galanin immunoreactivity in the glands. Sympathectomy resulted in marked reduction of dopamine beta-hydroxylase immunoreactivity with no appreciable change in galanin immunoreactivity. Retrograde labeling experiments demonstrated that galanin-immunoreactive sensory neurons in the trigeminal ganglion do not innervate the submandibular or sublingual gland. These results indicate that the galanin-like innervation of rat salivary glands is derived from parasympathetic nerves to the glands. Since rat sublingual glands contain largely mucous acini while rat submandibular gland acini are seromucous, electrophysiological responses to galanin and the muscarinic agonist, bethanechol, were compared. Agonist-induced voltage shifts varied between the two glands. The galanin-induced response at the level of the resting membrane potential in submandibular acinar cells was a hyperpolarization, while that in sublingual acinar cells was a depolarization. There was also a greater voltage dependence to the galanin-induced submandibular response than to the sublingual response. Differences were also noted in the acinar cell response to cholinergic stimulation between these glands. These results demonstrate the existence of a galanin-like innervation to salivary glands that may be functionally relevant. Moreover, the results challenge the idea that agonist-induced membrane responses are similar among acinar cells of different glands.  相似文献   
63.
Our study aimed to investigate the cardiovascular autonomic regulation related to the wearing-off phenomenon in Parkinson's disease (PD). We measured blood pressure (BP) and heart rate (HR) at rest and during orthostatic test in 16 patients with PD with wearing-off and in 15 patients with PD without wearing-off both before (baseline) and repetitively at 1-h intervals for up to 4 h after the morning PD medication dose.
The patients with wearing-off had fluctuation of BP during the observation period, BP increasing when the motor performance worsened and vice versa. The mean supine BP was at its highest at the baseline measurement (patients with wearing-off, 145 ± 18 mmHg; patients without wearing-off, 138 ± 17 mmHg), fell during the first hour (patients with wearing-off, 119 ± 17 mmHg; patients without wearing-off, 126 ± 18 mmHg), and then rose again toward the end of the observation period (patients with wearing-off, 136 ± 15 mmHg; patients without wearing-off, 138 ± 18 mmHg). This BP change was statistically significant only in PD patients with wearing-off ( P  < 0.001).
In conclusion, BP seems to fluctuate with motor impairment in PD patients with wearing-off. This fluctuation may represent autonomic dysfunction caused by the PD process itself, the effect of PD medication, or both.  相似文献   
64.
The hydrolysis of phosphatidylinositol-4,5-bisphosphate (PIP2) by rat sciatic nerve cytosolic phosphoinositidase C [phosphoinositide-specific phospholipase C (PIC)] was studied at neutral pH and at ionic concentrations that approximate intracellular conditions. The principal water-soluble product formed was shown to be inositol trisphosphate by anion exchange chromatography. The maximum hydrolysis rate (2.5 nmol/min/mg protein) was achieved at less than 100 nM Ca2+. Hydrolysis was markedly increased to 15 nmol/min/mg protein by inclusion of K+ in the reaction mixture. In the presence of 200 mM K+, the optimum Ca2+ was increased to approximately 600 nM. Higher Ca2+ concentrations progressively inhibited PIP2 hydrolysis. Mg2+ also inhibited the reaction, but the presence of equimolar amounts of ATP and Mg2+ had no effect. Appreciable degradation of phosphatidylinositol-4-phosphate (PIP) also occurred in the nanomolar Ca2+ range, whereas breakdown of phosphatidylinositol (PI) required millimolar Ca2+. The presence of PIP but not PI inhibited PIP2 hydrolysis. Upon subcellular fractionation of nerve, more than 50% of recovered PIC activity was in the cytosol and about 20% was located in a myelin-enriched fraction. Using PIP2 as substrate, PIC activities in nerves from normal and streptozotocin-induced diabetic animals were not different. However, the myelin-associated enzyme from diabetic animals was more labile to freezing and thawing.  相似文献   
65.
Amiodarone was injected endoneurially at increasing doses into the exposed tibial nerve of rats to study its electrophysiologic and pathologic effects on peripheral nerve fibers. Forty-five male Wistar rats were used, and each of the following concentrations was injected into 15 nerves: 25 micrograms/mL, 50 micrograms/mL, and 100 micrograms/mL. Microinjection of a 25 micrograms/mL concentration of amiodarone resulted in a subacute, incomplete conduction block evident at day 3 postinjection. This conduction block remained stable until day 10 and recovery was complete at day 35. Microinjection of a 50 micrograms/mL concentration of amiodarone produced a faster evolving conduction block, and significant axon degeneration (approximately 40% of fibers). Injection of a 100 micrograms/mL concentration resulted in severe acute motor axon degeneration followed by complete but delayed regeneration. Results of morphological studies closely correlated with electrophysiological findings. Amiodarone thus seems to have a direct toxic effect on axons at high concentrations in the peripheral nerve, and we suggest that different pathological changes described in human amiodarone neuropathy could be related to different concentrations of the drug in the nerve, perhaps due to variability of blood-nerve barrier efficacy.  相似文献   
66.
Nerve conduction velocities were studied in the median, posterior tibial, radial and sural nerves of 50 juvenile diabetics, average age 13 +/- 1.3 years and mean duration of diabetes 2.3 +/- 1.4 years. Motor conduction velocity (MCV) in the median nerve was reduced in 10% of the subjects, and in the posterior tibial in 32%. Sensory conduction velocity (SCV) in the radial nerve was reduced in 30% of the subjects, and in the sural in 44%. No relationship was found between the reduction in conduction velocity and the duration of diabetes; nevertheless, a correlation was observed between this reduction and the degree of glycaemic control represented by the glycosylated haemoglobin concentration. The authors emphasize the importance of good glycaemic control for the prevention of diabetic neuropathy.  相似文献   
67.
超声心动图诊断原发性心脏肿瘤   总被引:1,自引:1,他引:0  
目的:探讨原发性心脏肿瘤超声心动图(ECG)特征。方法:利用ECG检查42例心脏肿瘤。其中粘液瘤38例,恶性肉瘤2例,均经手术病理证实。横纹肌瘤2例,经随访证实。结果:ECG对38例粘液瘤,2例横纹肌瘤全部做出正确诊断。2例恶性肿瘤提示相应部位占位病变。粘液瘤多发生在左房,有明确的瘤蒂,肿瘤回声稀疏,活动度大。恶性肿瘤回声较强、无蒂,活动度小。横纹肌瘤多发生在室壁心肌内,呈结节状,与正常心肌间有明确的界限。结论:ECG对原发心脏肿瘤的诊断具有重要意义,可初步区分良、恶性肿瘤。  相似文献   
68.
本文报告心脏创伤35例。年龄最小7岁,最大68岁,其中包括心脏刺伤患者10例,心肌挫伤患者25例,死亡5例。作者强调快速确定诊断,紧急剖胸心包切开减压和心脏修补止血是心脏刺伤救治成功的关键。同时,对心肌挫伤的临床表现、早期诊断和及时处理等问题进行了讨论。  相似文献   
69.
Summary A case is described of symmetrical cavitating brain stem necrosis produced by cardiac arrest in a premature infant. Two months after birth this 25-week gestational age infant suffered a prolonged episode of bradycardia. She was resuscitated and then died 3 weeks later. The autopsy revealed striking bilateral cavitation of the brain stem tegmentum extending in a columnar fashion from the upper portion of the spinal cord to the hypothalamus. The findings in this case are identical to the brain stem injury experimentally produced by complete cardiac arrest in the rhesus monkey.  相似文献   
70.
Summary The aim of the study was to use a novel combination of two methods for the simultaneous evaluation of two effects of oral cisapride in 10 diabetic patients with autonomic neuropathy; gastric emptying time was measured by following radio-opaque markers and orocaecal transit time by the sulphasalazine-sulphapridine method. The study was of double-blind, randomized, placebo-controlled, cross-over design.It was possible to evaluate the effect of a prokinetic drug on gastric emptying and orocaecal transit times using these two noninvasive techniques at the same time. Cisapride significantly reduced both the gastric emptying (1.2 h versus 2.1 h) and orocaecal tansit (5.9 h versus 7.7 h) times.  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