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   58420篇
  免费   3127篇
  国内免费   1452篇
耳鼻咽喉   414篇
儿科学   931篇
妇产科学   778篇
基础医学   4082篇
口腔科学   314篇
临床医学   8140篇
内科学   14275篇
皮肤病学   101篇
神经病学   3661篇
特种医学   5167篇
外国民族医学   2篇
外科学   8637篇
综合类   9186篇
现状与发展   3篇
预防医学   1417篇
眼科学   561篇
药学   3385篇
  35篇
中国医学   1258篇
肿瘤学   652篇
  2024年   99篇
  2023年   842篇
  2022年   1610篇
  2021年   2274篇
  2020年   2039篇
  2019年   1812篇
  2018年   1832篇
  2017年   1647篇
  2016年   1681篇
  2015年   1876篇
  2014年   3921篇
  2013年   3750篇
  2012年   3213篇
  2011年   3537篇
  2010年   3054篇
  2009年   3033篇
  2008年   3171篇
  2007年   3186篇
  2006年   2910篇
  2005年   2408篇
  2004年   1923篇
  2003年   1670篇
  2002年   1350篇
  2001年   1309篇
  2000年   970篇
  1999年   890篇
  1998年   884篇
  1997年   825篇
  1996年   616篇
  1995年   640篇
  1994年   536篇
  1993年   478篇
  1992年   426篇
  1991年   340篇
  1990年   295篇
  1989年   257篇
  1988年   245篇
  1987年   218篇
  1986年   175篇
  1985年   210篇
  1984年   168篇
  1983年   89篇
  1982年   141篇
  1981年   102篇
  1980年   85篇
  1979年   78篇
  1978年   63篇
  1977年   41篇
  1976年   33篇
  1975年   16篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
Objectives To evaluate uterine artery resistance during multiovulation induction in relation to the implantation rate in patients attendingin vitro fertilization (IVF) cycles.Patients Multiovulation induction for IVF was monitored by daily determination of the pulsatility index (PI) of the uterine arteries, obtained by a transvaginal probe (6.5 MHz) implemented with color-flow imaging. Doppler data were obtained from 5 days before hCG administration to the day of follicular aspiration. One IVF cycle was monitored in 70 patients. In 17 patients, 41 IVF cycles were monitored until a successful attempt occurred.Results In the 70 patients studied during one IVF attempt, the PI of the uterine arteries significantly varied (P < 0.001) in the different phases of the cycle. In the 24 patients who conceived, a significantly lower PI (P < 0.03) was found throughout the cycle. This result was mainly due to a highly significant difference of PI values observed the day after hCG administration (P < 0.005). In the 17 patients who conceived after 1 to 4 negativein vitro fertilizations, no significant difference in PI was observed in the uterine artery resistance in cycles in which implantation was or was not successful.Conclusions Uterine artery resistance varies significantly during phases of the induction therapy. Uterine artery resistance is lower throughout the course of multiovulation induction in patients with higher pregnancy rates. The PI on the day after hCG administration was the best index of pregnancy rate. Low uterine artery resistance was present even in negative attempts in patients who eventually achieved a successful implantation. PI values 3 can be considered a favorable prognostic factor for future IVF cycles.Presented at the 49th Annual Meeting of the American Fertility Society, Montreal, 1993 and the 50th Annual Meeting of the American Fertility Society, November 5–10, 1994, San Antonio, Texas.  相似文献   
132.
Thrombosis of the hepatic artery (HAT) is a severe complication of liver transplantation, and most cases need regrafting. The aim of this study was to review our experience with this complication. From January 1986 through January 1992, 76 liver transplants were performed in 59 pediatric patients at the Children's Hospital La Paz, Madrid. The diagnosis of HAT was made in 12 cases (15.7%). The common patterns of clinical presentation were: fulminant liver necrosis (5), bile leak due to necrosis of the bile duct (4), and relapsing bacteremia (3). Clinical symptoms of fulminant liver necrosis started within the first 2 weeks after transplantation, with rapid deterioration and steep rises in SGOT and SGPT levels. All these patients were retransplanted on an urgent basis, but only 1 is alive 4 years later. Four patients developed bile leaks 13 to 60 days after transplantation; SGOT, SGPT, and total bilirubin were only slightly increased. Three children were retransplanted electively and are alive with a mean follow-up of 3 years. One exceptional patient had a Roux-en-Y jejunostomy and is doing well 30 months later with his original graft. The 3 remaining children had episodes of septicemia with hepatic abscess, liver infarction, and pleural effusion. Liver function tests were normal, with bilirubin levels below 2 mg/dl. All patients were retransplanted, but only 1 is alive and well 13 months later. In the present series, we found that early HAT produces fulminant clinical deterioration requiring an urgent regraft. Late HAT presenting with either infection or bile leak allows time for treatment by elective retransplantation. The best survival was obtained in the latter group. Correspondence to: J. Vázquez  相似文献   
133.
大鼠局灶性脑缺血模型及其与C反应蛋白变化的关系   总被引:34,自引:1,他引:33  
目的 改进大鼠大脑中动脉梗塞法,建立更接近于临床缺血性脑卒中及其再扩灌注的可靠模型,并观察其与血甭C反应蛋白变化的。方法沿大鼠右颈内动脉插入长2.1 ̄2.3cm直径0.205mm的单股尼龙丝,直达大脑中动脉起始部开口,阻断其血流,观察大鼠神经病学改变及脑组织形态学变化,并测定血清C反应蛋白含量。结果 术后大鼠表现特殊体态及典型追尾征,6h大脑中动脉供血区出现缺血性外观(TTC染色)及相应组织学变化  相似文献   
134.
135.
Background: Colic ischemia is a serious complication that can occur after abdominal aortic surgery. It has been described in two patients after laparoscopic aortic surgery. The goal of the current experiment was to determine the feasibility of inferior mesenteric artery (IMA) reimplantation during laparoscopic aortobifemoral bypass (LAFB). Methods: Six piglets were submitted to the laparoscopic approach according to the ``apron' technique previously described. The infrarenal aorta was clamped and an LAFB was performed using a dacron graft. The IMA was reimplanted in the body of the graft with a running 5-0 polypropylene suture. Results: Mean operation and dissection times were 282.5 min (range, 270–310 min) and 123 min (range, 110–140 min), respectively, with a mean blood loss of 108 ml (range, 80–150 ml). Aortic clamping and anastomotic times were 123 min (range, 110–135 min) and 33 min (range, 24–45 min), respectively. The IMA reimplantation took 55 min (range, 45–70 min). At autopsy, all anastomoses were patent with no stenosis nor leak. Conclusion: Laparoscopic IMA reimplantation during laparoscopic aortobifemoral bypass is feasible. Received: 10 July 1998/Accepted: 15 November 1998  相似文献   
136.
Vascular anatomy of the pancreaticoduodenal region: A review   总被引:4,自引:0,他引:4  
Vascular anatomy of the pancreaticoduodenal region has been the subject of numerous studies. However, several essential areas of confusion remain in interpretation of the vascular configuration. We note and discuss three key points in relation to this confusion: (1) a missing vascular arcade, (2) a rearrangement of the arcade by collateral and/or transverse vessels, and (3) a solitary vessel without an accompanying comites vein or artery. In addition, we consider that different interpretations as well as varying reported incidences depend on different "thresholds" when observations are made. Consideration of new aspects of vascular anatomy of the pancreaticoduodenal region is required for further improvement of surgical procedures. In terms of the selection of lymph node resection procedure, we discuss mainly the inferior arterial origin. Special attention should be paid to the ligation of inferior arteries because of the high incidence of the common trunk formation of the upper jejunal and inferior pancreaticoduodenal arteries. With regard to duodenum-preserving pancreatic head resection for benign tumors, our observations are introduced in view of either arterial or venous configuration. First, a communicating artery between the anterior and posterior arterial arcades is noted because of its possible critical role in blood supply to the papilla of Vater. Second, a venous drainage route from the duodenum to the retroperitoneal space in "normal" specimens is described. Received for publication on June 17, 1998; accepted on July 27, 1998  相似文献   
137.
Purpose: To evaluate the effects of topical timolol and apraclonidine on retrobulbar blood flow velocity waveforms in a group of healthy volunteers.Methods: Apraclonidine 1% and timolol maleate 0.5% single dose administrations were crossed over double masked in 12 healthy volunteers. The intraocular pressure measurements were followed by Doppler examination of the ophthalmic artery and the central retinal artery.Results: Intraocular pressure was reduced significantly on both treated and fellow eyes after timolol (p = 0.003, p = 0.04 respectively) and after apraclonidine (p = 0.002, p = 0.01 respectively). After apraclonidine administration end diastolic velocity, mean velocity decreased and pulsatility index increased in the ophthalmic artery of both treated and fellow eyes. Resistivity index increased and peak systolic velocity decreased only in the ophthalmic artery of treated eyes. All Doppler indices remained nonsignificant for central retinal artery of both eyes.After timolol administration there were no significant changes of the Doppler indices in the ophthalmic artery and central retinal artery of the treated and fellow eyes.Conclusion: Topical timolol and apraclonidine significantly reduced the intraocular pressure. Single dose administration of apraclonidine 1% increased the vascular impedance distal to the ophthalmic artery. On the other hand, timolol 0.5% had no effect on vascular impedance.  相似文献   
138.
报告3例RK术后严重眼球破裂伤的手术效果。方法部分穿透性角膜移植及联合瞳孔孔成形,前段玻璃体切除,角膜裂伤修补及后段玻璃体切除视网膜复位术。结果3例均保存了眼球。结论RK术后眼球破裂伤虽然严重而复杂,但通过穿透性角膜移植术及联合手术治疗,仍有可能保存眼球和恢复部分视力。  相似文献   
139.
Background: Exercise echocardiography (EE) is being used increasingly as an investigative technique now that dynamic images can be captured digitally. Its equivalent reliability with scintigraphic methods has been demonstrated in a hospital setting. This study analyzes its impact on daily practice. Materials and Methods: Standardized progressive stress was produced by supine bicycle ergometry. Echocardiographic images of complete cardiac cycles were obtained in standard apical and parasternal short-axis views before, during, and after maximum effort, and digitized for simultaneous analysis of synchronized images at rest and during exercise. Two hundred sixteen patients (175 men and 41 women; mean age 58 ± 10 years) were studied. Results: Image quality was suboptimal in 4 cases. In the remaining 212 cases, ischemia was detected in 91 cases, and the test was negative in 114 cases and doubtful in 7 cases. Control by selective coronary angiography, as indicated by the clinical situation, was performed in 52 cases. In this particular group, EE showed 87% sensitivity, which is significantly higher than the 59% recorded for conventional exercise testing (P > 0.0001). Conclusions: EE by bicycle ergometer in the supine position is a valid, noninvasive investigative technique that can be used in an outpatient situation (feasibility 95%) since it is readily available. Its value appears to be greatest in cases in which exercise ECG is not conclusive. A negative result enables the initial cardiologist to reassure the patient immediately, which has been demonstrated in the literature to have favorable prognostic value.  相似文献   
140.
We have studied the effects of idazoxan in rat aorta and small mesenteric artery. In the aorta, idazoxan behaved as a partial agonist (pKA=6.30). Prazosin produced rightward shift (pA2=9.88) and steepening of the idazoxan curve. In contrast, idazoxan had no effect of basal tension in the mesenteric artery, but shifted the noradrenaline curve to the right in a parallel manner (pA2=6.12). The selective al-adrenoceptor agonist, indanidine, also behaved as a partial agonist in the aorta and produced no significant contractions of the small mesenteric artery. Since idazoxan and indanidine have been reported to raise blood pressure in the pithed rat via an action at vascular 1-adrenoceptors, these results call into question the reliability of the small mesenteric artery assay as a predictor for 1-adrenoceptor-mediated pressor activity in vivo.  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