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   90482篇
  免费   6530篇
  国内免费   5086篇
耳鼻咽喉   327篇
儿科学   1530篇
妇产科学   527篇
基础医学   6543篇
口腔科学   634篇
临床医学   12414篇
内科学   10218篇
皮肤病学   277篇
神经病学   11116篇
特种医学   5420篇
外国民族医学   2篇
外科学   16150篇
综合类   17598篇
现状与发展   4篇
一般理论   1篇
预防医学   4018篇
眼科学   1103篇
药学   8410篇
  40篇
中国医学   5107篇
肿瘤学   659篇
  2024年   282篇
  2023年   1329篇
  2022年   2489篇
  2021年   3535篇
  2020年   3203篇
  2019年   2560篇
  2018年   2623篇
  2017年   2987篇
  2016年   3192篇
  2015年   3109篇
  2014年   5526篇
  2013年   6576篇
  2012年   5391篇
  2011年   5968篇
  2010年   5161篇
  2009年   4898篇
  2008年   5022篇
  2007年   5049篇
  2006年   4746篇
  2005年   4225篇
  2004年   3473篇
  2003年   3168篇
  2002年   2693篇
  2001年   2391篇
  2000年   1994篇
  1999年   1648篇
  1998年   1397篇
  1997年   1283篇
  1996年   1000篇
  1995年   867篇
  1994年   691篇
  1993年   547篇
  1992年   484篇
  1991年   410篇
  1990年   333篇
  1989年   258篇
  1988年   234篇
  1987年   188篇
  1986年   174篇
  1985年   228篇
  1984年   164篇
  1983年   92篇
  1982年   106篇
  1981年   108篇
  1980年   93篇
  1979年   54篇
  1978年   40篇
  1977年   42篇
  1976年   30篇
  1975年   15篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Changes in MAP2 and clathrin immunoreactivity were studied in gerbil hippocampus after transient cerebral ischemia. MAP2 immuno-reactivity decreased significantly by 1 h in the subiculum-CA1 and CA2 areas which correspond to reactive change, while no decrease was observed in CA1 until day 4. Before the initiation of delayed neuronal death, MAP2 immunoreactivity was not changed in CA1. On the other hand clathrin immunoreactivity increased in the pyramidal cell layer of CA1 by 3 h after ischemia and remained high for 2 days. Clathrin immunoreactivity in the pyramidal cell layer of CA1 diminished after delayed neuronal death. The transient change of clathrin was noted especially in CA1 in the period prior to delayed neuronal death. These results imply an abnormal change in clathrin turnover after ischemia, which may participate in the pathogenesis of delayed neuronal death.  相似文献   
52.
Prostaglandin E1 (PGE1) was used in renal transplant recipients with living related donors. The drug was given intravenously from day 1 to day 7 after transplantation at a dose of 40 µg/kg twice a day. A total of 45 patients were studied divided into two groups: 25 patients were treated with PGE1 (group B) and the remaining 20 patients did not receive the drug (group A). In group B, 24-h creatinine clearance (Ccr) was 66 ± 12.8 ml/min compared with 40.3 ± 13.4 ml/min in group A on the fifth postoperative day (P < 0.05). Urinary levels of N-acetyl-β-d -glucosaminidase (NAG) and serum levels of platelet factor 4 (PF4) in group B were significantly lower than in group A. On the fourth postoperative day, the urinary excretion of thromboxan B2 (TxB2) in group A was higher than in group B, but not significantly (5.1 ± 3.0 ng/day and 2.8 ± 1.1 ng/day, respectively). Acute rejection occurred in four patients in group B and in 10 patients (40%) in group A. The percentage of Leu2a-positive lymphocytes in group B was higher than in group A. We conclude that postoperative administration of PGE1 improves graft function in kidneys from living related donors.  相似文献   
53.
To clarify the role of serotonin in cerebral ischemia, we examined the effects of selective serotonin reuptake inhibitors, citalopram and clomipramine, on ischemic neuronal damage in the gerbil. Pretreatment with citalopram (40 mg/kg i.p.) and clomipramine (20 mg/kg i.p.) protected against neuronal destruction of hippocampal CA1 pyramidal cells following 5 min of forebrain ischemia. Furthermore, microdialysis assays showed that a striking increase in extracellular excitatory amino acid levels during ischemia was significantly inhibited by pretreatment with citalopram and clomipramine. However, citalopram (40 mg/kg i.p.) did not alter the extracellular amino acid concentrations in normal gerbils. Thus, serotonin reuptake inhibitors have a protective effect against ischemic neuronal damage. Furthermore, the present result suggests that the protective effect is mediated through prevention of the accumulation of extracellular excitatory amino acids during and after ischemia.  相似文献   
54.
A 66-year-old man with atrial fibrillation was referred soon after developing left lower limb and abdominal pain with rectal bleeding. An immediate flush aortogram showed embolic occlusion of the left distal superficial femoral artery and superior mesenteric artery (SMA), 3 cm from its ostium. Recombinant tissue plasminogen activitor (rtPA) 40 mg was selectively in stilled in the SMA in two boluses. Abdominal symptoms resolved within 48 h, and complete recanalization of the SMA was shown on angiography. Exploratory laparotomy after 72 h showed a normal small bowel and right colon, and was completed by femoropopliteal embolectomy. Six months later, the patient remained asymptomatic.  相似文献   
55.
Summary A total of 208 multiple trauma patients with head injury (HI) were investigated who had been treated in the period from 1990 to 1995. The average age was 35.2 ± 17.7 years; the injury severity according to ISS was 30.2 ± 8.6 points; 20.5 % died as a result of the HI; the mortality of all patients was 26.5 %. The Glasgow Coma Scale (GCS) was determined at an average of 22 min after trauma (8.0 ± 4.3 points) at the scene of accident. The patients were classified according to GCS into minor HI (group 1: 14–15 points), moderate HI (group 2: 9–13 points) and severe HI (group 3: 3–8 points). Patient outcome was assessed by the Glasgow Outcome Scale (GOS) and was classified as good (GOS 4 and 5) and poor (GOS 1, 2 and 3) outcome. At the latest, 2 h after trauma, a CT scan of the head (CCT) was done. The HI groups are compared regarding frequency of types of injury. In all HI groups the fractures of the bony face occurred at the same frequency (36.0–38.9 %). The frequency of calotte fractures (Kal-Fx) increased from group 1 (8.0 %) to 2 (19.2 %) and 3 (25.6 %); fractures of the skull base significantly differed between group 1 (16.0 %), 2 (7.8 %) and 3 (33.4 %). Epidural hemorrhage (EDB) appeared only in group 2 (7.8 %) and 3 (6.7); subdural hemorrhage was found in group 1 (2.7 %), 2 (7.8 %) and 3 (10.0 %). Subarachnoid hemorrhage (SAB) was significantly more frequently seen, dependent on HI severity, in group 3 (26.7 %) compared to group 2 (11.7 %) and 1 (8.0 %). Intracerebral contusion (ICK) significantly increased from group 1 (12.0 %) to 2 (27.3) and 3 (45.6 %). Brain swelling (BS) also significantly increased from group 1 (8.0 %) to 2 (19.5 %) and 3 (49.0 %) and lesions of ventricles (VL) from group 1 (2.7 %) to 2 (11.7 %) and 3 (20.0 %). Midline shift (13.4 %) and signs of herniation (4.5 %) only occurred in group 3. The analysis of correlation/regression and receiver operating characteristics was able to predict 79 % of patients' outcome accurately using GCS (r 0.54; P < 0.0001) alone, using CCT (r 0.65; P < 0.0001) 87 % were correctly predicted with significant variables Cal-Fx, EDB, SAB and BS. CCT with GCS (r 0.74; P < 0.0001) were able to predict 88 % accurately with significant variables Cal-Fx, EDB, BS and GCS. The combination of CCT with GCS, age and ISS (r 0.78; P < 0.0001) was able to predict only 87 % correctly, although the r value was the highest; significant variables were Kal-Fx, EDB, BS, VL, GCS, age and ISS.   相似文献   
56.
An atypical variant of reflex sympathetic dystrophy (RSD) is presented in a 45 year old female with a vascular malformation of the right arm and chest wall. The mechanism was thought to be compression of the brachial plexus by the malformation. The unique scintigraphic features of this presentation of RSD in the ulnar arterial distribution are illustrated.  相似文献   
57.
58.
59.
Spinal cord injury (SCI) produces an increase in extracellular excitatory amino acid (EAA) concentrations that results in glutamate receptor-mediated excitotoxic events. An important class of these receptors is the metabotropic glutamate receptors (mGluRs). mGluRs can activate a number of intracellular pathways that increase neuronal excitability and modulate neurotransmission. Group I mGluRs are known to modulate EAA release and the development of chronic central pain (CCP) following SCI; however, the role of group II and III mGluRs remains unclear. To begin evaluating group II and III mGluRs in SCI, we administered the specific agonists for group II, APDC, or group III, L-AP4, by interspinal injection immediately following SCI. Contusion injury was produced at spinal segment T10 with a New York University impactor (12.5-mm drop, 10-g rod 2 mm in diameter) in 30 adult male Sprague-Dawley rats (175-200 g). Evoked and spontaneous behavioral measures of CCP, locomotor recovery, changes in mGluR expression, and amount of spared tissue were examined. Neither APDC nor L-AP4 affected locomotor recovery or the development of thermal hyperalgesia; however, L-AP4 and APDC attenuated changes in mechanical thresholds and changes in exploratory behavior indicative of CCP. APDC- and L-AP4-treated groups had higher expression levels of mGluR2/3 at the epicenter of injury on post contusion day 28; however, there was no difference in the amount of spared tissue between treatment groups. These results demonstrate that treatment with agonists to group II and III mGluRs following SCI affects mechanical responses, exploratory behavior, and mGluR2/3 expression without affecting the amount of tissue spared, suggesting that the level of mGluR expression after SCI may modulate nociceptive responses.  相似文献   
60.
参附注射液对肠缺血-再灌注大鼠肿瘤坏死因子α的影响   总被引:5,自引:0,他引:5  
目的观察肿瘤坏死因子α(TNF-α)在大鼠肠缺血-再灌注损伤过程中的作用及参附注射液对TNF-α的影响,探讨参附注射液防治肠缺血-再灌注损伤机制。方法 SD大鼠随机分为肠缺血-再灌注组(IR组)、参附注射液预处理组(SF组)和假手术组(C组)。采用阻断肠系膜上动脉(SMA)的方法制造肠缺血-再灌注模型。分别测定各组动物血浆、肠组织TNF-α含量及血液动力学变化;光镜观察肠粘膜损伤情况。结果IR组再灌注后MAP下降,与C组和SF组比有显著性差异(P<0.01);SF组肠粘膜损伤程度减轻,与IR组比有显著性差异(P<0.01);SF组血浆及肠组织TNF-α水平降低,与IR组比有显著性差异(P<0.01)。结论参附注射液可明显防治大鼠肠缺血-再灌注导致的肠粘膜损伤,这种作用可能是通过抑制TNF-α的释放实现的。  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