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   4723篇
  免费   362篇
  国内免费   50篇
耳鼻咽喉   25篇
儿科学   161篇
妇产科学   120篇
基础医学   558篇
口腔科学   109篇
临床医学   404篇
内科学   918篇
皮肤病学   97篇
神经病学   393篇
特种医学   247篇
外科学   476篇
综合类   734篇
一般理论   3篇
预防医学   413篇
眼科学   36篇
药学   195篇
中国医学   3篇
肿瘤学   243篇
  2021年   44篇
  2020年   36篇
  2019年   50篇
  2018年   58篇
  2017年   44篇
  2016年   47篇
  2015年   51篇
  2014年   103篇
  2013年   153篇
  2012年   128篇
  2011年   159篇
  2010年   121篇
  2009年   113篇
  2008年   219篇
  2007年   256篇
  2006年   285篇
  2005年   249篇
  2004年   253篇
  2003年   229篇
  2002年   127篇
  2001年   124篇
  2000年   134篇
  1999年   142篇
  1998年   98篇
  1997年   98篇
  1996年   74篇
  1995年   59篇
  1994年   57篇
  1993年   53篇
  1992年   84篇
  1991年   85篇
  1990年   69篇
  1989年   98篇
  1988年   77篇
  1987年   91篇
  1986年   68篇
  1985年   64篇
  1984年   71篇
  1983年   47篇
  1981年   34篇
  1980年   39篇
  1979年   59篇
  1977年   38篇
  1975年   37篇
  1974年   38篇
  1973年   58篇
  1972年   43篇
  1971年   39篇
  1970年   36篇
  1968年   42篇
排序方式: 共有5135条查询结果,搜索用时 15 毫秒
71.
72.
Up to now, we have identified 77 X-linked conditions in which mental retardation is the primary or a major component manifestation. These conditions were subdivided into 2 categories, designated respectively "X-linked mental retardation syndromes" and "Non-specific X-linked mental retardation". Forty genes have been regionally mapped onto the X chromosome. However, in several instances the data were derived from a single family and most lod scores were less than 3.0.  相似文献   
73.
Carbon monoxide diffusing capacity of the lungs (DLCO) was measured in bullfrogs, Rana catesbeiana (mean body weight 260 g) along with oxygen uptake, pulmonary perfusion and lung volume. The measurements were all performed by methods depending on mass-spectrometry. Pulmonary oxygen uptake, DLCO and perfusion all increased with body temperature. At 20 degrees C O2-uptake was 0.49 ml STPD . kg-1 . min-1 at rest and DLCO was 0.022 ml STPD . kg-1 . min-1 . Torr-1. At 30 degrees C the values for O2-uptake and DLCO approximately doubled. Lung volume was large (90 ml . kg-1) and independent of body temperature. Oxygen uptake and DLCO of the bullfrog were small compared to values for a similar-sized mammal but the ratios of DLCO to O2-uptake quite similar. Analysis of available data on DLCO and O2-uptake in ectotherms also suggests a close correlation between O2-uptake and DLCO.  相似文献   
74.
We have sequenced the genes encoding the inner capsid protein VP6 and the nonstructural proteins NSP1 and NSP4 of the Indian neonatal serotype P8[11]G9 human/bovine reassortant candidate vaccine rotavirus strain 116E. These three genes share a high degree of sequence and deduced amino acid homology with human prototype strain Wa. Our results confirm and extend those of previous RNA-RNA hybridization studies which suggested that these genes are of human origin, and will facilitate examination of the host immune response to 116E induced by natural infection and vaccination. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   
75.
Lung carcinoids occur sporadically and rarely in association with multiple endocrine neoplasia type 1 (MEN1). There are no well defined genetic abnormalities known to occur in these tumors. We studied 11 sporadic lung carcinoids for loss of heterozygosity (LOH) at the locus of the MEN1 gene on chromosome 11q13, and for mutations of the MEN1 gene using dideoxy fingerprinting. Additionally, a lung carcinoid from a MEN1 patient was studied. In four of 11 (36%) sporadic tumors, both copies of the MEN1 gene were inactivated. All four tumors showed the presence of a MEN1 gene mutation and loss of the other allele. Observed mutations included a 1 bp insertion, a 1 bp deletion, a 13 bp deletion and a single nucleotide substitution affecting a donor splice site. Each mutation predicts truncation or potentially complete loss of menin. The remaining seven tumors showed neither the presence of a MEN1 gene mutation nor 11q13 LOH. The tumor from the MEN1 patient showed LOH at chromosome 11q13 and a complex germline MEN1 gene mutation. The data implicate the MEN1 gene in the pathogenesis of sporadic lung carcinoids, representing the first defined genetic alteration in these tumors.   相似文献   
76.
Paramagnetic macrocyclic chelates show promise as magnetic resonance (MR) imaging contrast agents due to stability and relaxivity comparable to those of DTPA-type chelates. For the three copper and manganese macrocyclic complexes studied in aqueous solution, T1 and T2 relaxivities ranged from 0.14 to 5.88 mM-1sec-1 at 6.25 MHz. In rats, the intravenous administration of 16 mumol/kg of Mn(cyclam) caused the liver T1 relaxation rate to double at 15 minutes after injection. T1 measurements by pulsed MR imaging and manganese analyses on excised tissue showed that both relaxation rate (1/T1) and manganese content of liver and kidney increase linearly with the dosage of Mn(cyclam). The linear relationship between 1/T1 and manganese content can be considered an "in tissue" relaxivity plot for the agent. The resulting relaxivity is 54 mM-1sec-1 in liver, compared with 3.1 mM-1sec-1 in aqueous solution. Although this work is preliminary, the implication for medical MR imaging applications is that macrocyclic contrast agents can be effective at approximately one-tenth the current typical dose used for gadolinium DTPA.  相似文献   
77.
The granulocyte phagocytosis test, Karnofsky index, and ASA standard were used in the context of 287 patients for general surgery, for the purpose of retrospective elucidation of the relationship between presurgical prognostication and postsurgical complications. Sensitivity, specificity, and "predictive values" were calculated. The highest information potential in terms of prognostication was recorded from objectively measurable granulocyte phagocytosis. Presurgical prognostication was found to be of clinical relevance only to surgical problem patients.  相似文献   
78.
Using magnetic resonance imaging, we studied 6 patients with the dysarthria-clumsy hand syndrome. All were found to have pontine infarctions contralateral to the symptomatic side. Clinically, these patients exhibited dysarthria; "clumsiness," characterized by dysmetria, dysrhythmia, dysdiadochokinesia and sometimes truncal and gait ataxia; and mild ipsilateral weakness. Previous clinical-anatomical correlations for this syndrome are limited by inconsistencies in clinical diagnostic criteria and low-resolution imaging methods. In our patients, and in a review of the literature, the overwhelming majority of patients with the dysarthria-clumsy hand syndrome had pontine infarcts. We conclude that if rigid clinical criteria are used, the label of the dysarthria-clumsy hand syndrome predicts a lesion in the contralateral basis pontis.  相似文献   
79.
Recent discoveries have implicated a number of "new" (i.e., previously unrecognized) infectious agents as important causes of outbreaks of gastroenteritis. Unfortunately, the ability to detect these agents in an outbreak can be limited by two factors: 1) the lack of appropriate assays-many of which are still in developmental stages and are not readily available to clinical laboratories, and 2) inadequately or improperly collected specimens. At CDC, many newly developed assays are being used for research and for outbreak investigations. The information in this report is especially intended for public health agencies that collaborate with CDC in investigating outbreaks of gastroenteritis. The report provides an update on guidelines and recommendations for the proper collection of specimens to be sent to CDC, gives general background information concerning some recently discovered pathogens, lists some of the tests available at CDC, and provides a list of CDC contacts. The guidelines and the general information provided on causes of outbreaks of gastroenteritis can be also used by public health workers for investigations when specific testing is available and appropriate.  相似文献   
80.
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