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   137248篇
  免费   11575篇
  国内免费   5890篇
耳鼻咽喉   1742篇
儿科学   1889篇
妇产科学   2248篇
基础医学   19447篇
口腔科学   2426篇
临床医学   16005篇
内科学   23045篇
皮肤病学   2863篇
神经病学   9384篇
特种医学   6063篇
外国民族医学   53篇
外科学   15414篇
综合类   11305篇
现状与发展   22篇
一般理论   38篇
预防医学   8647篇
眼科学   4411篇
药学   13345篇
  67篇
中国医学   4619篇
肿瘤学   11680篇
  2024年   288篇
  2023年   1555篇
  2022年   4141篇
  2021年   5657篇
  2020年   3822篇
  2019年   4109篇
  2018年   4502篇
  2017年   3634篇
  2016年   4230篇
  2015年   5841篇
  2014年   7178篇
  2013年   7045篇
  2012年   10390篇
  2011年   10636篇
  2010年   6521篇
  2009年   5166篇
  2008年   7279篇
  2007年   7065篇
  2006年   6947篇
  2005年   6559篇
  2004年   4946篇
  2003年   4413篇
  2002年   3802篇
  2001年   2963篇
  2000年   2880篇
  1999年   2974篇
  1998年   1706篇
  1997年   1634篇
  1996年   1265篇
  1995年   1207篇
  1994年   1017篇
  1993年   752篇
  1992年   1217篇
  1991年   1139篇
  1990年   1025篇
  1989年   1010篇
  1988年   963篇
  1987年   886篇
  1986年   746篇
  1985年   710篇
  1984年   529篇
  1983年   413篇
  1982年   285篇
  1981年   274篇
  1980年   228篇
  1979年   365篇
  1978年   282篇
  1977年   198篇
  1974年   230篇
  1973年   238篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
背景:临床中为了解决颈椎翻修/骨质疏松/长节段固定等问题,一般选择进行前、后路联合内固定来获得满意的术后稳定性,难免加重患者的手术创伤,增加术后并发症概率及住院费用.而颈前路反向椎弓根内固定可通过一次前路手术获得前后路联合内固定的稳定性,但临床缺少适用的颈前路椎弓根内固定系统.目的:依据颈椎相关解剖结构研制出新型颈椎前...  相似文献   
992.
本研究探讨大鼠肝部分切除65%和32%后1、2、3、7、14天期间,胰岛细胞数目和分泌活动的变化。取胰尾,用醛品红,Grimelius 法和 Hellerstrom—Hellman 法分别显示胰岛 B、A 和 D 细胞,计算上述三种岛细胞染色深度和分泌颗柱数量百分数,作为判断岛细胞分泌活动的指标。结果如下:1、A、B、D 三种岛细胞的数目均无明显改变,2、65%肝邵分切除后,胰岛细胞分泌活动的变化是:术后第1、2天,B 细胞分泌减弱,A 细胞稍强;术后第3天,B 细胞的分泌活动明显增强,A 细胞分泌继续增强,D 细胞分泌一直保持正常水平;术后第7天,B 细胞的分泌大为减弱,到术后第14天尚未恢复正常,在此期间,A 细胞分泌仍加强,D 细胞分泌也增强,3、32%肝部分切除后,岛细胞分泌活动的变化情况基本如上,只是变化的幅度较小和进程较快,其中以 B 细胞最明显。上述变化均与肝再生过程密切相伴。B细胞的变化似乎直接与肝再生相关,A 和 D 细胞可能起协同作用。  相似文献   
993.

目的:探讨胰岛素治疗与2型糖尿病视网膜病变的关系。

方法:收集2016-06/2018-01于我院内分泌科住院的2型糖尿病患者415例830眼。根据不同降糖用药、眼底造影检查结果、胰岛素用量分别进行分组,收集各组患者一般资料,采集清晨空腹静脉血,测量空腹血糖、糖化血红蛋白(HbA1c)、空腹C肽等指标。分析不同用药和不同视网膜病变组间患者空腹血糖、HbA1c、空腹C肽的变化以及胰岛素用量和糖尿病视网膜病变的相关关系。

结果:不同用药组间糖尿病视网膜病变程度不同,不同视网膜病变组间患者的胰岛素用量不同(P<0.05),2型糖尿病患者并发视网膜病变的胰岛素用量切点值为37.5U/d。胰岛素用量>37.5U/d组中2型糖尿病患者的视网膜病变较多,且胰岛素用量与2型糖尿病患者视网膜病变程度呈正相关。

结论:不同降糖治疗对糖尿病视网膜病变的影响不同,使用胰岛素治疗与2型糖尿病性视网膜病变的发病及严重程度呈正相关。  相似文献   

994.
我国宠物医院快速发展, X射线诊断应用也随之增多, 其工作人员和同室协助人员的防护问题值得关注。本文从国际上宠物医院的X射线诊断放射防护相关管理和研究进展出发, 结合我国宠物医院X射线诊断的现状、存在的问题以及各部门的管理规定, 从中总结出我国宠物医院放射防护中政府部门、宠物医院、放射工作人员以及同室协助人员可能出现的典型问题, 并提出当前我国宠物医院放射防护工作的重点, 有助于为政府决策提供科学建议, 规范完善宠物医院的各项放射防护工作。  相似文献   
995.
996.
Efforts to develop satisfactory intraluminal gastrointestinal contrast agents for magnetic resonance (MR) imaging have focused on depicting only the bowel lumen to exclude possible involvement by a pathologic process. To determine whether the bowel wall can be adequately imaged with use of the contrast agent and whether bowel wall visualization is a better index of the utility of the contrast agent for MR imaging, perfluoroocytlbromide (PFOB) was studied in human subjects. Twenty consecutive patients referred for abdominal or pelvic MR imaging were selected. All patients were given 400-1,000 mL of PFOB orally. MR imaging was performed at 0.38 and 1.5 T with T1- and T2-weighted spin-echo pulse sequences before and after administration of PFOB. The images were graded independently by three blinded readers. All readers reported significantly superior conspicuity of the bowel lumen and wall after PFOB than before PFOB administration (P less than .002). Among the post-PFOB studies, those with superior bowel wall visualization demonstrated superior overall image quality. In three patients, lesions were optimally demonstrated because the relationship of the process to the bowel wall, rather than just to the lumen, was identified. In two patients, masses arising within the bowel wall could be identified prospectively only when the bowel wall was adequately imaged. The authors conclude that while lumen identification is improved with PFOB, its greatest clinical utility may be in facilitating intestinal wall visualization.  相似文献   
997.
Acute acalculous cholecystitis (AAC) is usually seen as a complication of major surgery or trauma. Although this entity is well-known in the surgical literature, little has been written about it in the radiologic literature. A review of patient records from 1975 through 1982 revealed 16 patients with pathologically confirmed AAC on whom at least 1 sonographic study had been performed. Thickening of the gallbladder wall, a subserosal "halo" of edema, pericholecystic abscess, and marked gallbladder distention were consistent findings in AAC. In the proper clinical setting, these otherwise nonspecific findings allow a prompt and accurate diagnosis.  相似文献   
998.
Dopamine receptor stimulation causes vascular and neurohumoral responses that may be beneficial in patients with heart failure. Oral inactivity, emesis and adrenergic-induced arrhythmias have limited the use of currently available compounds. Fenoldopam (SKF-82526-J) is a new, orally available, selective, dopamine-receptor agonist with potent renal vasodilating properties (six times that of dopamine) without positive inotropic or adrenergic activity. Drug efficacy was clinically evaluated in 10 patients with heart failure after single oral doses of placebo and 50, 100 and 200 mg of medication. Placebo produced no changes. Peak efficacy was noted 30 minutes to 1 hour after the 200 mg dose with mean blood pressure decreasing from 96 +/- 15 (mean +/- SD) to 83 +/- 8 mm Hg (p less than 0.05), pulmonary capillary wedge pressure decreasing from 23 +/- 6 to 20 +/- 8 mm Hg (p less than 0.05) and mean pulmonary artery pressure decreasing from 32 +/- 9 to 29 +/- 8 mm Hg (p less than 0.05). Systemic vascular resistance decreased from 1,987 +/- 887 to 1,191 +/- 559 dynes.s.cm-5 (p less than 0.05) with a subsequent 55% increase in cardiac index from 2.2 +/- 1.1 to 3.1 +/- 1.3 liters/min per m2 (p less than 0.05). Heart rate and right atrial pressure did not change (p greater than 0.05). No emesis or new tachycardia was noted at any dose. Baseline hemodynamics generally returned within 3 to 4 hours. Fenoldopam, therefore, is a short-acting, orally effective drug that decreases systemic vascular resistance and increases cardiac index in patients with heart failure and represents a new class of oral compounds that may be useful in treating such patients.  相似文献   
999.
Somatostatin-like immunofluorescence occurs in the hypothalamus and neurohypophysis of three euryhaline teleosts: tilapia, killifish, and mudsucker. This immunofluorescence was eliminated by incubating the primary antibody with excess somatostatin or somatostatin-28 but not with urotensin II, a partial analogue of somatostatin. In all three fishes, the strongest reaction was seen in the proximal pars distalis and parts of the pars intermedia. Strongly fluorescing processes from cells of the preoptic nucleus extend toward the pituitary. Distinct fluorescence was also associated with the neurohypophysis penetrating into the rostral pars distalis in the tilapia but not in the killifish or mudsucker. In the tilapia, an extensive network of immunofluorescent fibers and small cells were present in the anterior dorsolateral telencephalon, in addition to a moderately fluorescing group of cells anterolateral to the preoptic nucleus. A small area of diffuse fluorescence was also seen in the anterior dorsolateral midbrain tegmentum. Previous physiological studies have implicated somatostatin as a regulator of prolactin cell activity in tilapia. The present study demonstrates the route by which somatostatin may be delivered to the rostral pars distalis to inhibit prolactin secretion.  相似文献   
1000.
High right atrial pacing (abrupt initiation and random coupling to the spontaneous rhythm) was performed in 285 pediatric cardiac patients for diagnostic purposes. Nine patients (3%) were found to have pacing-induced infra-His conduction block. In two patients this occurred following a preceding long cycle as well as a preceding short-to-long sequence cycle length change. In five patients block occurred with an abrupt shortening of the coupling H-H interval (in three patients the infra-His block initiated a series of 2:1 infra-His block). In two patients with type II second-degree atrioventricular block the initiating events were not recorded. In one of them, when the rapid atrial pacing was incremented to the same cycle length with infra-His block, the atrioventricular response became 1:1 with normal conduction. These findings of pacing-induced infra-His conduction block can be explained by the normal response of the His-Purkinje system to changes in the preceding cycle lengths, and to the abrupt shortening of the coupling interval.  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