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   3784篇
  免费   220篇
  国内免费   31篇
耳鼻咽喉   25篇
儿科学   51篇
妇产科学   15篇
基础医学   494篇
口腔科学   47篇
临床医学   290篇
内科学   1337篇
皮肤病学   71篇
神经病学   215篇
特种医学   188篇
外科学   467篇
综合类   32篇
预防医学   165篇
眼科学   50篇
药学   242篇
中国医学   2篇
肿瘤学   344篇
  2023年   57篇
  2022年   114篇
  2021年   207篇
  2020年   94篇
  2019年   114篇
  2018年   143篇
  2017年   86篇
  2016年   108篇
  2015年   100篇
  2014年   127篇
  2013年   105篇
  2012年   188篇
  2011年   170篇
  2010年   106篇
  2009年   88篇
  2008年   159篇
  2007年   162篇
  2006年   145篇
  2005年   137篇
  2004年   139篇
  2003年   139篇
  2002年   122篇
  2001年   101篇
  2000年   96篇
  1999年   96篇
  1998年   51篇
  1997年   27篇
  1996年   32篇
  1995年   23篇
  1994年   29篇
  1993年   24篇
  1992年   71篇
  1991年   64篇
  1990年   56篇
  1989年   72篇
  1988年   48篇
  1987年   44篇
  1986年   52篇
  1985年   51篇
  1984年   27篇
  1983年   29篇
  1982年   13篇
  1981年   17篇
  1979年   25篇
  1977年   26篇
  1976年   13篇
  1974年   16篇
  1973年   13篇
  1971年   12篇
  1966年   12篇
排序方式: 共有4035条查询结果,搜索用时 0 毫秒
51.
World Journal of Surgery - We started performing sentinel node navigation surgery (SNNS) for patients with early gastric cancer (EGC) using infrared ray electronic endoscopy (IREE) with indocyanine...  相似文献   
52.
Seventeen patients with adrenal adenoma causing Cushing's syndrome, eight patients with Cushing's disease due to hypersecretion of ACTH, and five patients with primary aldosteronism due to an aldosteronoma were studied for their computed tomographic (CT) patterns, hormonal profiles, and macroscopic and microscopic findings of the adrenal gland. Black (or brown) adrenal adenomas were found in 71% of the patients with Cushing's syndrome, but not in patients with aldosteronoma. The adrenal tissue of patients with Cushing's disease was predominantly yellow. The number of compact cells was larger in black or brown adenomas than in yellow tumors or hyperplastic adrenal tissue. In patients with Cushing's syndrome, urinary excretion of 17-ketosteroids (17-KS) and serum aldosterone concentrations were lower in those with black or brown adenomas than in those with yellow adenomas (P less than 0.05). Patients with Cushing's disease had even higher 17-KS and serum aldosterone levels. No difference was found in serum cortisol concentrations and dexamethasone suppressibility in two types of adenomas causing Cushing's syndrome. Visual estimation of radiological density of the adrenal tissue relative to the kidney on CT scan and quantitative measurement of it by CT number revealed a difference between the two types of adrenal tumors causing Cushing's syndrome. Adrenal tumors with decreased density on CT scan were yellow adenomas with predominantly clear cells, and those with equal or increased density were black or brown adenomas with predominantly compact cells. All aldosteronomas had decreased density and consisted of clear cells. It is suggested that black or brown adenomas of the adrenal gland have higher radiological density and accompanying lower serum aldosterone and urinary 17-KS levels than ordinary yellow tumors. The abundance of compact cells may have some significance for the development of this particular type of adrenal tumor.  相似文献   
53.
Vasoconstrictor effect of neuropeptide Y (NPY) on canine coronary artery   总被引:2,自引:0,他引:2  
The effect of neuropeptide Y (NPY) on the coronary circulation of the closed-chest dogs (n = 7) was studied. The left circumflex artery was cannulated and perfused with arterial blood withdrawn from the femoral artery. The flow was kept constant by a roller pump and it was monitored by an electromagnetic flowmeter. An increase in the perfusion pressure which was characterized by a slow onset and long-lasting effect (more than 10 min) was found in each dog after NPY. There were no significant changes in the arterial blood pressure, central venous pressure and heart rate. The peak rise was observed at about 1 min; from 108 +/- 9 mmHg to 144 +/- 13 mmHg (mean +/- SE) (p less than 0.01). This increase in the perfusion pressure resulted from vasoconstriction distal to the cannula. When the doses of NPY was changed, a dose-response relation was found (n = 4). Phentolamine did not inhibit the vasoconstrictor effect of NPY (n = 4). The endogeneous substance NPY might be engaged in the regulation of myocardial perfusion and can be a candidate responsible for coronary spasm.  相似文献   
54.
Inflow characteristics of left and right ventricular filling were assessed in 40 patients with myocardial infarction and in 10 normal subjects by pulsed Doppler echocardiography. Patients with myocardial infarction were subdivided into four groups, focusing on the involvement of right ventricular and septal branches of the coronary arteries. Group I consisted of 11 patients with anterior infarction who showed an obstructive lesion of the proximal left anterior descending branch involving the first septal perforator with a patent right coronary artery. Group II consisted of 10 patients with inferior infarction who showed an obstructive lesion of the proximal right coronary artery involving the right ventricular branch. Group III consisted of 12 patients with both anterior and inferior infarction who showed obstructive lesions of both the proximal left anterior descending branch and the right coronary artery involving the right ventricular branch. Group IV consisted of seven patients with lateral infarction who showed an obstructive lesion of the diagonal branch or branches of the circumflex coronary artery with a patent left anterior descending branch and right coronary artery. Three measurements were performed from the transmitral and transtricuspidal inflow velocity patterns to assess the left and right ventricular diastolic behaviors. These measurements were: acceleration half-time, deceleration half-time of early diastolic rapid inflow, and the ratio of the peak velocity of early diastolic rapid inflow to that of the late diastolic inflow due to the atrial contraction. Impaired diastolic filling of the left ventricle compensated by enhanced left atrial contraction was observed in patients with myocardial infarction from groups I, II, III and IV.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
55.
T Aizawa  P M Hinkle 《Endocrinology》1985,116(3):909-919
The sequence of PRL and GH release from GH4C1 cells was studied in perifusion and static culture systems. The secretory pattern elicited by TRH differed from those caused by depolarizing concentrations of KCl (Ca2+-initiated secretion), vasoactive intestinal peptide (VIP), 8-bromo-cAMP, and forskolin (cAMP-mediated secretion), and 12-O-tetradecanoylphorbol-13-acetate (TPA) (protein kinase C activation). TRH, K+, VIP, and TPA all caused secretion within 1 min in the perifusion system but the peak response to TRH and depolarization occurred earlier than the peak responses to TPA and VIP. PRL and GH release in response to a pulsatile application of TRH (0.4-min pulse every 5 min for 25 min) did not decline with a low dose, indicating that acute desensitization does not occur, but did decrease with a high concentration. When cells in the perifusion system were subjected to continuous stimulation, TRH caused a biphasic response with a 2- to 3-min period of high secretion followed by a second phase in which GH and PRL secretion were 60-70% the rates in the first phase. KCl caused predominantly first-phase secretion, and TPA caused a biphasic secretory pattern with a delay in its peak of action. VIP caused a modest but prolonged response whether administered in a pulsatile or sustained manner. When GH-cells were exposed to 100 nM TRH for 2 days, [3H] [N3-methyl-His2]TRH binding was decreased (down-regulation), intracellular PRL was increased (170% of control), and intracellular GH was decreased (65% of control). In these down-regulated cells, baseline PRL and GH secretion were changed in proportion to the relative intracellular hormone content. The responsiveness to TRH, KCl, and TPA during the initial 10-min period (first phase) was reduced; however, the responsiveness to these substances in the subsequent 50-min period (second phase) was unchanged. The ED50 for TRH stimulation of hormone release was increased 2- to 4-fold in down-regulated cells, but the dose-response curves for other secretagogues were not shifted. These data suggest that the initial burst of hormone release caused by TRH is mediated by Ca2+, and that prolonged exposure to TRH causes homologous desensitization.  相似文献   
56.
Encapsulated hepatocyte transplantation is a promising approach to cell transplantation without immunosuppression as an alternative to whole organ liver transplantation. However, the shortage of donor cells for hepatocyte transplantation has not been resolved, and at this critical point, it seems necessary to establish a method of hepatocyte cryopreservation to allow clinical application of hepatocyte transplantation and the development of a bioartificial liver system in the near future. In this study we demonstrated that cryopreserved microencapsulated rat and human hepatocytes can retain their hepatic function and that cryopreserved microencapsulated human hepatocytes transplanted into rat spleen remain viable without immunosuppression. Rat and human hepatocytes were isolated by a collagenase digestion method, and they were microencapsulated with poly-L-lysine. The microencapsulated rat hepatocytes were transferred to culture medium (DMEM containing 10% FBS and 10% DMSO) and immediately frozen in liquid nitrogen. A warm water bath (37 degrees C) was used to thaw the microencapsulated hepatocytes. Hepatic function, drug metabolism, and cell morphology were assessed after 90 days of cryopreservation. After 1 week of cryopreservation, microencapsulated hepatocytes were cultured for up to 2 weeks to assess their hepatic function and morphology. The morphology of human hepatocytes was assessed after 30 days of cryopreservation. Cryopreserved human hepatocytes were transplanted into rat spleen to assess their morphology. Cryopreserved microencapsulated hepatocytes retained their viability and were strongly positive for expression of albumin, OAT2, CYP3A2, and CYP3A9. Two weeks after cultivation, the cryopreserved microencapsulated rat hepatocytes had retained their hepatic function (urea synthesis). Cryopreserved microencapsulated human hepatocytes also mainly survived and retained their hepatic function for at least 30 days after cryopreservation. Moreover, entrapped cryopreserved human hepatocytes also survived and expressed albumin in rat spleen after transplantation. We demonstrated a novel method of long-term cryopreservation of rat and human hepatocytes by using an encapsulation technique, with retention of biological activity and excellent survival of the cryopreserved microencapsulated human hepatocytes transplanted into rat spleen. We believe that this novel approach to hepatocytes cryopreservation provides a new direction in encapsulated cell therapy with the goal of clinical application in the near future.  相似文献   
57.
Two patients with spinal Langerhans cell granulomatosis were followed by magnetic resonance imaging, and the observed signal changes were detailed. Both patients had no neurologic abnormalities but back pain. They were treated by immobilization with a brace and bed rest. Their back pain disappeared after about a month. At the first visit, the tumorous lesions involving vertebrae showed mainly low signal intensity on T1-weighted imaging (T1WI) and high intensity on T2-weighted imaging (T2WI). They were clearly enhanced by gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA). Their original intensities changed to iso-intensities on both T1WI and T2WI without enhancement by Gd-DTPA after a year. These signal changes might indicate the healing stage of the involved vertebrae and recommend the removal of the spinal brace.  相似文献   
58.
59.
60.
Background The impact of isolated diastolic dysfunction (IDD) and systolic dysfunction (SD) on health-related quality of life (HRQOL) is unknown. Methods and Results To evaluate HRQOL in patients with IDD and SD under treatment, information on outpatients aged 60-84 years was extracted from the records of 4,500 consecutive individuals who underwent echocardiographic examination at Sado General Hospital. The medical records of these patients were reviewed and a questionnaire, including the Medical Outcome Study Short Form 36, was mailed to 71 IDD and 99 SD patients; answers were obtained from 66 and 91 patients, respectively. The HRQOL of patients with cardiac dysfunction was impaired even when echocardiographic parameters improved with treatment. Patients with IDD showed an impairment of HRQOL similar to those with SD. Compared with males, female patients had a larger and more significant reduction in the physical and mental components of the HRQOL score. These scores correlated positively with exercise capacity in patients with IDD or SD. Conclusions Impaired HRQOL, in both its mental and physical components, is a serious problem for IDD and SD patients under treatment. Because exercise intolerance may underlie the reduced HRQOL, improving exercise capacity could be an important target for managing outpatients with heart failure. (Circ J 2008; 72: 1436 - 1442).  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