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   7576篇
  免费   473篇
  国内免费   28篇
耳鼻咽喉   102篇
儿科学   241篇
妇产科学   106篇
基础医学   1259篇
口腔科学   191篇
临床医学   633篇
内科学   1674篇
皮肤病学   227篇
神经病学   581篇
特种医学   439篇
外国民族医学   2篇
外科学   1215篇
综合类   94篇
一般理论   1篇
预防医学   495篇
眼科学   94篇
药学   371篇
中国医学   3篇
肿瘤学   349篇
  2022年   47篇
  2021年   112篇
  2020年   63篇
  2019年   87篇
  2018年   115篇
  2017年   87篇
  2016年   141篇
  2015年   144篇
  2014年   172篇
  2013年   241篇
  2012年   322篇
  2011年   376篇
  2010年   180篇
  2009年   202篇
  2008年   323篇
  2007年   363篇
  2006年   344篇
  2005年   286篇
  2004年   280篇
  2003年   316篇
  2002年   274篇
  2001年   244篇
  2000年   275篇
  1999年   227篇
  1998年   110篇
  1997年   95篇
  1996年   67篇
  1995年   65篇
  1994年   64篇
  1993年   56篇
  1992年   122篇
  1991年   123篇
  1990年   109篇
  1989年   115篇
  1988年   125篇
  1987年   142篇
  1986年   121篇
  1985年   124篇
  1984年   88篇
  1983年   74篇
  1981年   51篇
  1979年   75篇
  1978年   65篇
  1976年   48篇
  1974年   61篇
  1973年   74篇
  1972年   53篇
  1971年   52篇
  1970年   49篇
  1968年   51篇
排序方式: 共有8077条查询结果,搜索用时 15 毫秒
61.
Prolonged chair restraint and social isolation in the rhesus monkey led to a reduction in the urinary excretion of HVA (4-hydroxy-3-methoxyphenylacetic acid), DOPAC (3,4-dihydroxyphenylacetic acid), VMA methoxy-4-hydroxymandelic acid), and MHPG (3-methoxy-4-hydroxyphenylethylglycol) over a 3 week period. This adaptation to a chronically "stressful" situation corresponds to earlier studies on the rhesus monkey indicating a gradual reduction in the urinary excretion of norepinephrine and epinephrine after initiation of restraint. The following basic information on the urinary excretion of catecholamine metabolites was obtained: (1) the rate of excretion of the dopamine metabolites (HVA and DOPAC) is about four times higher than the rate of excretion of adrenergic metabolites (VMA and MHPG): (2) MHPG is the major adrenergic metabolite in the rhesus monkey; and (3) the excretion rates of the urinary metabolites varied considerably between animals.  相似文献   
62.
An outbreak of a fatal haemolytic anaemia in a dairy herd of cattle in Switzerland was shown to be associated with infections with five vector-borne pathogens, namely Anaplasma marginale, A. phagocytophilum, Babesia bigemina, a Theileria spp belonging to the buffeli/sergenti/orientalis complex and haemotrophic Mycoplasma spp. The latter three had not been documented before this outbreak in Switzerland. To characterise the haematological and blood chemical changes in these unique cows, packed cell volume was determined in all 286 blood samples, blood smears, and complete haematology were performed from 285 and 173 blood samples, respectively, and biochemical parameters were assayed in 105 serum samples. Regenerative anaemia was the key sign of illness. Red blood cells of anaemic cattle were hypochromic and macrocytic. Anaemic animals had reduced platelet cell counts and increased total white cell counts. In addition, increased serum bilirubin, blood aspartate aminotransferase, gamma glutamyltransferase, glutamic dehydrogenase and blood urea nitrogen and decreased magnesium, calcium and albumin levels were found in anaemic cattle when compared to animals with normal packed cell volume. Most changes could not be attributed to a single infection. A. marginale seemed to be important in causing the outbreak, but co-infections may have aggravated the disease development and clinical signs. Thus, when encountering cattle with haemolytic anaemia, all of the mentioned pathogens should be included as differential diagnosis.  相似文献   
63.
64.
Summary The pharmacokinetics of high-dose metoclopramide (10 mg/kg body wt. in five infusions of 2 mg/kg body wt. each) was studied in 11 patients (5 females, 6 males) in two groups: group A with and group B (consisting of five patients) without forced diuresis. When the drug was infused, forced diuresis had no influence on the pharmacokinetics of metoclopramide (serum level after the 1st infusion was 851±361 ng/ml in group A versus 840±348 ng/ml in group B; after the 5th infusion it was 2,005±588 ng/ml in group A versus 2,463±1,350 ng/ml in group B). There were significant differences in the 24-h serum levels (582±308 ng/ml in group A versus 379±170 ng/ml in group B;P<0.05) and in the elimination half life (8.5±2.6 h in group A versus 6.1±1.1 h in group B;P<0.05). The results demonstrate that the dosage regimen originally suggested by Gralla for cytostatic drugs, with forced diuresis for high-dose metoclopramide therapy, may also be applied, with no dosage reduction, with to other cytostatic drugs which do not require forced diuresis.  相似文献   
65.
Zusammenfassung Es wird über Erfahrungen bei der Typenbestimmung von 127 Tuberkelbakterien-Stämmen berichtet, die aus menschlichen Untersuchungsstoffen (95), Organen perlsüchtiger Rinder (15) und Organen tuberkulöser Hühner (17) gezüchtet wurden. Zur Differenzierung zogen wir die kulturmorphologischen Eigenschaften, den Bromkresolpurpur-Nährboden (Wagener u.Mitscherlich), die Feststellung des O2-Bedarfes (Lebek), die Katalase-Aktivität (Middlebrook), den Niacin-Test (Bönicke u.Lisboa), die Testung gegenüber Brenzschleimsäurehydracid (Bönicke u.Lisboa) und Tierversuche heran. Schwierigkeiten entstanden nur bei fermentschwachen und isoniazid-resistenten Stämmen beider Säugetiertypen der Tuberkelbakterien. Dabei verhielt sich keines der Verfahren immer typengerecht. Die Typendiagnose kann also nur unter Auswertung mehrerer Methoden gewonnen werden.Auf den kürzlich vonBönicke empfohlenen Nicotinamidase-Test zur Identifizierung schwierig einzuordnender, auch isoniazidresistenter Stämme wurde hingewiesen.Der Brenzschleimsäurehydrazid-Test und die Methode der Prüfung des O2-Bedarfes eignen sich nach unseren Beobachtungen nicht für die Erkennung von Geflügeltuberkelbakterien.  相似文献   
66.
Patient motion occurring during data acquisition in single photon emission computed tomography (SPET) can cause serious reconstruction artefacts. We have developed a new approach to correct for head motion in brain SPECT. Prior to motion, projections are assigned to conventional projections. When head motion occurs, it is measured by a motion monitoring system, and subsequent projection data are mapped to 'virtual' projections. The appropriate position of each virtual projection is determined by applying the converse of the patient's accumulated motion to the actual camera projection. Conventional and virtual projections, taken together, form a consistent set that can be reconstructed using a three-dimensional (3D) algorithm. The technique has been tested on a range of simulated rotational movements, both within and out of the transaxial plane. For all simulated movements, the motion corrected images exhibited better agreement with a motion free reconstruction than did the uncorrected images. This technique may help to overcome one of the major remaining limitations on image quality and quantitative accuracy in SPECT.  相似文献   
67.
A recombinant pseudorabies (Aujeszky’s disease) virus (PrV) designated as vE16lac was constructed by deleting a 3-kbp DNA segment spanning the junction of long and short components of the viral genome, and by replacing the deleted segment with a lacZ-expression cassette. The aim of constructing this mutant was (a) to determine whether the terminal repeat (Tr) can serve as a template for the regeneration of the internal repeat (Ir), and (b) whether this deletion causes a reduction in the neuroinvasiveness of the virus. To analyze the mechanism of equalization, revertant viruses were selected and structurally characterized from vE16lac infection of PK-15 cells, mice and pigs. Because all revertants acquired Ir sequences identical to that of the wild-type virus, the equalization process occurred using the Tr as a template to reconstitute the Ir. We also found that the recombinant virus vE16lac was virulent in both pigs and mice. The data are discussed in view of studies performed with similar PrV mutants by other authors (Rall et al., 1992, Dean and Cheung, 1995 and Dean et al., 1996). This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   
68.
The present study sought possible factors leading to the cytological diagnosis of atypical squamous cells of uncertain significance (ASCUS) in cases of high-grade squamous intraepithelial lesions (HSIL). Based on retrospective histopathological analysis of loop electrical excision procedure (LEEP) products that diagnosed HSIL, two study groups were randomly selected. The first was consisted of cases with two consecutive Papanicolaou (Pap) smears with the diagnosis of ASCUS. The second (control) group was represented by cases diagnosed as HSIL by cytology. From the Pap smears diagnosed as ASCUS, the sampling limitations was different from control group (P < 0.05). The median size of the largest lesion in each case with ASCUS was 2.66 mm (+/- 1.71 mm). In the control group, the median size of the largest lesion was 5.15 mm (+/-2.58 mm) (P < 0.05). The size of the lesion and sample limitations led patients with cervical intraepithelial neoplasms to be diagnosed as ASCUS for two consecutive times, after a 6-mo period.  相似文献   
69.
The telechelics 1 from methyl methacrylate and 1,1,2,2-tetraphenyl-1,2-diphenoxyethane, can be separated by adsorption chromatography. The structure of the dimers and trimers was identified by 1H NMR-spectroscopy. The free radical oligomerization is a process in which the syndiotactic structure is favoured above the isotactic one.  相似文献   
70.
Integrin-mediated cell-matrix interactions are essential for development, tissue homeostasis, and repair. Upon ligand binding, integrins are recruited into focal adhesions (FAs). Integrin-linked kinase (ILK) is an FA component that interacts with the cytoplasmic domains of integrins, recruits adaptor proteins that link integrins to the actin cytoskeleton, and phosphorylates the serine/threonine kinases PKB/Akt and GSK-3beta. Here we show that mice lacking ILK expression die at the peri-implantation stage because they fail to polarize their epiblast and to cavitate. The impaired epiblast polarization is associated with abnormal F-actin accumulation at sites of integrin attachments to the basement membrane (BM) zone. Likewise, ILK-deficient fibroblasts showed abnormal F-actin aggregates associated with impaired cell spreading and delayed formation of stress fibers and FAs. Finally, ILK-deficient fibroblasts have diminished proliferation rates. However, insulin or PDGF treatment did not impair phosphorylation of PKB/Akt and GSK-3beta, indicating that the proliferation defect is not due to absent or reduced ILK-mediated phosphorylation of these substrates in vivo. Furthermore, expression of a mutant ILK lacking kinase activity and/or paxillin binding in ILK-deficient fibroblasts can rescue cell spreading, F-actin organization, FA formation, and proliferation. Altogether these data show that mammalian ILK modulates actin rearrangements at integrin-adhesion sites.  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