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   7943篇
  免费   587篇
  国内免费   31篇
耳鼻咽喉   136篇
儿科学   302篇
妇产科学   187篇
基础医学   1103篇
口腔科学   123篇
临床医学   710篇
内科学   1447篇
皮肤病学   97篇
神经病学   897篇
特种医学   222篇
外科学   1133篇
综合类   105篇
一般理论   15篇
预防医学   563篇
眼科学   206篇
药学   569篇
中国医学   10篇
肿瘤学   736篇
  2023年   79篇
  2022年   145篇
  2021年   264篇
  2020年   189篇
  2019年   213篇
  2018年   264篇
  2017年   222篇
  2016年   241篇
  2015年   254篇
  2014年   327篇
  2013年   422篇
  2012年   626篇
  2011年   536篇
  2010年   352篇
  2009年   262篇
  2008年   399篇
  2007年   439篇
  2006年   380篇
  2005年   352篇
  2004年   340篇
  2003年   322篇
  2002年   324篇
  2001年   131篇
  2000年   109篇
  1999年   134篇
  1998年   63篇
  1997年   58篇
  1996年   44篇
  1995年   38篇
  1994年   29篇
  1993年   29篇
  1992年   71篇
  1991年   63篇
  1990年   55篇
  1989年   68篇
  1988年   51篇
  1987年   52篇
  1986年   50篇
  1985年   58篇
  1984年   42篇
  1983年   35篇
  1982年   34篇
  1981年   28篇
  1979年   48篇
  1978年   26篇
  1977年   25篇
  1976年   25篇
  1975年   22篇
  1973年   26篇
  1972年   26篇
排序方式: 共有8561条查询结果,搜索用时 78 毫秒
991.
Mucormycosis is caused principally by members of the genus Rhizopus, especially R arrhizus and R. oryzae. Infection attributable to R. rhizopodiformis has rarely been documented. Of 13 cases of mucormycosis diagnosed during a 4-year period (1974 to 1978) at The Mount Sinai Hospital, 6 cases, occurring within 9 months, were caused by R. rhizopodiformis. The six isolates were identified mainly by: growth at 50 degrees C; production of short, sometimes branched, sporangiophores arising from opposite rhizoids; elongated columellae; and small spherical-to-elliptical, smooth-to-finely striated sporangiospores. The possibility that this explosive occurrence of R. rhizopodiformis at our institution was because of nosocomial acquisition was strongly supported by the recovery of this same mycotic agent from adhesive bandages used in the cardiac intensive care unit, where a patient developed subcutaneous R. rhizopodiformis infection after cardiac surgery. The invasive potential of R. rhizopodiformis was manifested by the extensive subcutaneous and systemic infections in each of the six patients, three of whom developed antibody against this mucormycotic agent.  相似文献   
992.
To examine whether growth hormone (GH) secretion is adversely affected by chronic renal insufficiency (CRI), the GH secretory response of dispersed anterior pituitary cells perifused with GH-releasing hormone (GHRH) was investigated in 5/6 nephrectomized (CRI, N = 18) and sham-operated (N = 18) rats. Two weeks after nephrectomy, during a period of stable uremia, CRI rats had significantly higher serum concentrations (mean +/- SEM) of urea nitrogen and creatinine than sham rats, 16.8 +/- 1.4 mmol/liter (47 +/- 4 mg/dl) and 79.6 +/- 0.0 mumol/liter (0.9 +/- 0.0 mg/dl) versus 6.1 +/- 0.4 mmol/liter (17 +/- 1 mg/dl) and 35.4 +/- 0.0 mumol/liter (0.4 +/- 0.0 mg/dl), respectively (P less than 0.0001). Incremental gains in body weight and nose to tail-tip length of CRI rats over two weeks were also significantly depressed, 53.3 +/- 5.38 g (CRI) versus 87.0 +/- 3.78 g (sham; P less than 0.0001) and 3.2 +/- 0.2 cm (CRI) versus 3.6 +/- 0.1 cm (sham; P less than 0.05). The cumulative food intake as well as food efficiency (g food consumed/g weight gain) were also adversely influenced by the uremic state: food intake 304 +/- 1 g (CRI) versus 397 +/- 6 g (sham; P less than 0.0001) and food efficiency 0.173 +/- 0.013 g/g of weight gain (CRI) versus 0.219 +/- 0.008 g/g of weight gain (sham). No significant difference in GH secretory rate (ng/min/10(7) cells) was found between the uremic and sham animals under basal conditions, 65.2 +/- 2.1 (CRI) and 67.9 +/- 2.2 (sham) or in response to GH-releasing hormone, 282.8 +/- 42.4 (CRI) versus 306.2 +/- 42.6 (sham).(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
993.
The detection of viable myocardium in infarcted regions, i.e. hibernating myocardium, is a major goal in clinical cardiology today. We applied combined planar and single photon emission tomography (SPET) to the non-invasive estimation of the left ventricular ejection fraction (LVEF), myocardial blood flow and free fatty acid uptake in the heart. Of the 31 patients with coronary artery disease, 25 (81%) had had a previous myocardial infarction. All patients had at least one persistent perfusion defect on the stress-rest technetium-99m hexakis-2-methoxyisobutyl isonitrile (Sestamibi) study, and the results revealed 57/124 (46%) persistent perfusion defects. As a part of the perfusion study, the LVEF was measured at rest using the first-pass 99mTc-Sestamibi injection, and the mean LVEF was 47% ±9% (mean ± 1 standard deviation). Iodine-123 phenylpentadecanoic acid (123I-pPPA) imaging at rest was performed within 2 weeks from the perfusion study. Then 6-mm transaxial, sagittal and coronal slices of the perfusion and 123I-pPPA studies were reconstructed. The bull's eye displays of the coronal slices were visually surveyed and divided into 4 quadrants: anterior, lateral, posterior and septal. The following image score was used: 0 = fixed defect, 1 = partial uptake and 2 =normal uptake. Moreover an index of metabolic reserve (MR) was calculated by dividing the bull's eye of the 123I-pPPA study by the bull's eye of resting 99mTc-Sestamibi, and its maximum value was normalized to 100%. Fourteen segments (25%) had a normal 123I-pPPA uptake with a MR value of 96% ±8%. Twenty-two segments (39%) had a partial 123I-pPPA uptake with a MR of 74% ±20%, whereas 21 segments (36%) had no 123I-pPPA uptake and a very low MR of 36%±34%. There was a highly significant correlation (r =0.70) between LVEF and MR. These findings suggest that it is possible to identify viable myocardium by measuring contractile function (first-pass, multiple-gated 99mTc-Sestamibi) and myocardial perfusion (stress-rest 99mTc-Sestamibi) and by combining these parameters with myocardial fatty acid uptake (1231-pPPA) studies. Correspondence to: IT Kuikka  相似文献   
994.
995.
Achenbach Child Behavior Checklist ratings were collected on boys aged 6 to 11 years screened as not having significant behavior problems, as clinic-referred boys, and as boys diagnosed as having Attention Deficit-Hyperactivity Disorder alone or together with Oppositional-Defiant Disorder or Conduct Disorder. Cluster analysis resulted in a classification system related to DSM-III-R classification of the boys and parent self-report of mildly antisocial acts. Clusters also enhanced the ability of the instrument to detect Attention Deficit Hyperactivity Disorder and disruptive behavior disorders.  相似文献   
996.
Episodic ataxia type 1 is a paroxysmal neurological disorder characterized by short-lived attacks of recurrent midline cerebellar dysfunction and continuous motor activity. Mutations in KCN1A, the gene encoding Kv1.1, a voltage-gated neuronal potassium channel, are associated with the disorder. Although rare, the syndrome highlights the fundamental features of genetic ion-channel diseases and serves as a useful model for understanding more common paroxysmal disorders, such as epilepsy and migraine. This review examines our current understanding of episodic ataxia type 1, focusing on its clinical and genetic features, pathophysiology, and treatment.  相似文献   
997.
Endocannabinoid signaling has recently been implicated in ethanol-seeking behavior. We analyzed the expression of endocannabinoid-related genes in key brain regions of reward and dependence, and compared them between the alcohol-preferring AA (Alko Alcohol) and nonpreferring ANA (Alko Non-Alcohol) rat lines. A decreased expression of fatty acid amidohydrolase (FAAH), the main endocannabinoid-degrading enzyme, was found in prefrontal cortex (PFC) of AA rats, and was accompanied by decreased enzyme activity in this region. Binding of the endocannabinoid-cannabinoid 1 (CB1) receptor ligand (3)[H]SR141716A, and [35S]GTPgammaS incorporation stimulated by the CB1 agonist WIN 55,212-2 were downregulated in the same area. Together, this suggests an overactive endocannabinoid transmission in the PFC of AA animals, and a compensatory downregulation of CB1 signaling. The functional role of impaired FAAH function for alcohol self-administration was validated in two independent ways. The CB1 antagonist SR141716A potently and dose-dependently suppressed self-administration in AA rats when given systemically, or locally into the PFC, but not in the striatum. Conversely, intra-PFC injections of the competitive FAAH inhibitor URB597 increased ethanol self-administration in nonselected Wistar rats. These results show for the first time that impaired FAAH function may confer a phenotype of high voluntary alcohol intake, and point to a FAAH both as a potential susceptibility factor and a therapeutic target.  相似文献   
998.
17 cases of focal epithelial hyperplasia of the oral mucosa (FEH, Heck's disease) were investigated for the presence of human papillomavirus (HPV) nucleic acid sequences by means of in situ DNA hybridization using biotinylated DNA probes of HPV types 1, 6, 11, 13, 16, 18, and 32. Ten of 17 cases were positive for HPV 13 DNA in contrast to 6 of 17 positive cases obtained after application of the HPV 32 probe, with a double infection in one case. The results of our study suggest, that HPV 13 and HPV 32 are very specifically found in lesions of FEH and can be detected in a high percentage of cases using in situ hybridization.  相似文献   
999.
CT of hepatic schistosomiasis mansoni   总被引:1,自引:0,他引:1  
Schistosomal periportal fibrosis produced a typical pattern on computed tomography in five patients. Low-density periportal tissue, present throughout the liver, enhanced strongly after the administration of contrast medium. While rounded in cross section, the thickened periportal tissue produced linear and branching patterns when imaged in longitudinal section. In all cases, the sonographic features were typical of schistosomal periportal fibrosis. A lack of awareness of the distinctive features of periportal fibrosis may result in a mistaken diagnosis of hepatic metastases.  相似文献   
1000.
G M Hanna  C A Lau-Cam 《Die Pharmazie》1984,39(12):816-818
Direct dissolution of the bulk material, capsule, or freeze-dried solution for injection and an internal standard in chloroform-d and recording of the PMR spectra provides a simple, specific, and accurate assay method form diphenhydramine hydrochloride [2-(diphenyl-methoxy)-N,N-dimethylethanamine hydrochloride] in pharmaceutical samples. The drug content can be calculated from the integral values for the N-methyl protons of diphenhydramine at ca. 2.85 ppm and for the methyl protons of tert-butyl alcohol at ca. 1.27 ppm. The mean +/- SD% recoveries from synthetic mixtures simulating capsules and injectables were 100.0 +/- 0.2 (n = 11) and 100.1 +/- 0.4 (n = 4), respectively. The method also permits the detection of degradation of diphenhydramine such as benzhydrol, diphenylchloromethane, and 2-(dimethylamino)ethanol to a minimum of about 2% of the parent compound.  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