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   26588篇
  免费   1454篇
  国内免费   62篇
耳鼻咽喉   418篇
儿科学   1150篇
妇产科学   875篇
基础医学   4289篇
口腔科学   606篇
临床医学   2186篇
内科学   5293篇
皮肤病学   552篇
神经病学   2591篇
特种医学   1140篇
外国民族医学   14篇
外科学   3800篇
综合类   134篇
一般理论   3篇
预防医学   1373篇
眼科学   501篇
药学   1387篇
中国医学   19篇
肿瘤学   1773篇
  2022年   215篇
  2021年   359篇
  2020年   238篇
  2019年   330篇
  2018年   421篇
  2017年   351篇
  2016年   494篇
  2015年   482篇
  2014年   655篇
  2013年   838篇
  2012年   1188篇
  2011年   1266篇
  2010年   659篇
  2009年   699篇
  2008年   1161篇
  2007年   1244篇
  2006年   1164篇
  2005年   1191篇
  2004年   988篇
  2003年   987篇
  2002年   906篇
  2001年   903篇
  2000年   934篇
  1999年   794篇
  1998年   370篇
  1997年   300篇
  1996年   252篇
  1995年   228篇
  1994年   198篇
  1993年   195篇
  1992年   482篇
  1991年   508篇
  1990年   489篇
  1989年   417篇
  1988年   397篇
  1987年   416篇
  1986年   401篇
  1985年   396篇
  1984年   274篇
  1983年   214篇
  1982年   143篇
  1981年   153篇
  1979年   262篇
  1978年   185篇
  1977年   159篇
  1976年   157篇
  1975年   164篇
  1974年   192篇
  1973年   167篇
  1972年   154篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Apolipoprotein E isoforms were determined in 139 unrelated patients with retinitis pigmentosa (RP). When compared to prevalence rates for the general population in Germany, an increased prevalence was observed for phenotypes E2/E2: 10.1 vs. 1.0% (p less than 0.001), E2/E3: 19.4 vs. 12.0% (p less than 0.05), and E2/E4: 5.8 vs. 1.5% (n.s.), while the prevalence appeared to be reduced for phenotypes E3/E3: 48.9 vs. 59.8% (n.s.) E3/E4: 13.7 vs. 22.9% (p less than 0.05), and E4/E4: 2.2 vs. 2.8% (n.s.). These findings suggest that genetically determined abnormalities of plasma lipoprotein metabolism may be associated with some forms of RP.  相似文献   
12.
Spontaneous and surgery-associated bleeding in patients with von Willebrand disease (vWD) cannot always be controlled with desmopressin or replacement therapy. This paper presents results on the use of recombinant-activated factor VII (rFVIIa) in patients with vWD included in the internet registry Haemostasis.com. Twenty-eight reports on the use of rFVIIa in vWD were identified from the database and included in this analysis. The bleeding episodes were classified as mild (n = 7), moderate (n = 16), or severe (n = 2), and were unspecified in three cases. The median dose of rFVIIa administered was 94 microg/kg body weight (40-127.3 microg/kg). Bleeding stopped in 23 of 27 evaluable patients (85%) and markedly decreased in three patients; the total response rate was 96% (26/27 patients). Response did not correlate with the type of vWD, the site or severity of the initial bleed, or the rFVIIa dose. Other replacement therapies were infrequently used, and their use was similar in the 24 h before and after rFVIIa administration. Eighteen patients also received antifibrinolytic treatment, but its impact on response was not recorded. Only one adverse event (mild fever) was observed. These cases suggest a role for rFVIIa as a safe and effective therapy for vWD.  相似文献   
13.
Back pain in in-vitro fertilized and spontaneous pregnancies   总被引:1,自引:0,他引:1  
The influence of ovarian stimulation in in-vitro fertilization (IVF) on the prevalence of back pain with onset during pregnancy was studied in 31 women who became pregnant after IVF treatment and compared with that of 200 spontaneously pregnant women. A two times higher prevalence rate of sacral pain in late pregnancy was reported among IVF pregnant women (P < 0.0001), as well as a significantly higher prevalence rate of positive results of pelvic pain provocation tests performed in late pregnancy (0.0001 < or = P < or = 0.015), as compared with that of the spontaneously pregnant women. Among the IVF pregnant women, there was a significant positive correlation between relaxin concentrations in early pregnancy and the outcome of pelvic pain provocation tests (0.44 < or = r < or = 0.51, P < 0.05). In addition, the serum relaxin concentration was the factor that best explained differences in sacral pain prevalence. When the influence of serum relaxin concentration on back pain prevalence was taken into account, women carrying multiple pregnancies had no more pain than women carrying singletons, and IVF pregnant women had no more pain than spontaneously pregnant women. These results support the hypothesis that relaxin is involved in the generation of pelvic pain in pregnant women.   相似文献   
14.
15.
Objectives.To test the safety, efficacy, and toxicity of gene therapy using wild-type p53-expressing adenovirus (Ad-CMV-p53) in a nude mouse model with intraperitoneal (ip) 2774 human ovarian cancer cell line that contains a p53 mutation.Study design.An initial study of adenovirus tolerance was determined in nude mice by a single ip injection of increasing doses of Ad-CMV-p53. Nude mice were implanted with an LD100dose of 1 × 107cells. To study the efficacy and specificity of Ad-CMV-p53 treatment, the mice received treatment with different adenovirus constructs. One group received Ad-CMV-p53 and another group received a control adenovirus construct, Ad-CMV-βgal. To study the treatment response to Ad-CMV-p53, the mice were divided into groups and received various treatment schedules of 1 × 108pfu of Ad-CMV-p53.Results.The mice tolerated Ad-CMV-p53 without adverse effects at doses of 1 × 108pfu. The response to Ad-CMV-p53 showed significant survival duration in each dose regimen, with a survival time greater than that of untreated animals (P= 0.0173). However, no statistically significant survival advantage was observed between Ad-CMV-p53- and Ad-CMV-βgal-treated mice.Conclusions.These studies show that at the adenovirus dose and administration regimen used, there is effective but not specific 2774 tumor growth inhibitionin vivo.Efficient introduction of biologically active genes into tumor cells would greatly facilitate cancer therapy. Thus, although promising, these results caution that much effort will be required to realize the potential for clinical application of adenovirus-based ovarian cancer gene therapy.  相似文献   
16.
 The organization of the time frames for perceiving, generating, and updating information in the CNS has as of yet received little attention despite its elementary character for human behavior. We investigated temporal epochs in perceiving, acting, and updating in patients with anterior and posterior lesions of the left and right hemisphere, in patients with lesions in the left hemisphere without aphasia, and in healthy controls. Three temporal ranges, 30, 300, and 3000 ms, were assessed with different psychophysical paradigms. Prolongation of the temporal perception of order (30 ms) was most pronounced with left posterior lesions, of repetitive action (300 ms) with left anterior lesions, and updating (3000 ms) with left and right anterior lesions. Temporal deficits are group as well as parameter specific. Our results support the notion of coordinated coexistence of different temporal mechanisms.  相似文献   
17.
18.
19.
Replication-defective retroviruses expressing the t- neu oncogene, or a hybrid protein with the neu tyrosine kinase linked to the external region of the human epidermal growth factor receptor ( egfr-neu ), were used to establish lines of murine oligodendroglial precursor cells. Differentiation of the t- neu lines into myelin-associated glycoprotein (MAG)-positive oligodendrocytes was induced by dibutyryl cAMP, and the egfr-neu line showed limited differentiation in vitro upon withdrawal of epidermal growth factor. Cerebellar granule cell neurons expressed mitogens for the cell lines. Upon transplantation into demyelinated lesions, t- neu line cells engaged with the demyelinated axons whereas the egfr-neu line cells differentiated further and ensheathed the axons. These cell lines thus interact with neurons in vitro and in vivo and can be used as tools to define the molecules involved in different stages of neuron-glia interaction.  相似文献   
20.
Summary During the past few years, a new tumor type has emerged in the pediatric and adolescent group of cancer patients, which has been designated malignant peripheral neuroectodermal tumor (MPNT). This tumor has some clinical and pathological signs in common with either soft-tissue sarcomas or classic Ewing's sarcoma, but is defined as a distinct entity because of its immunohistological characteristics. The tumor expresses neuronal markers, but the pattern varies: chromogranin, neuron-specific enolase, synaptophysin, protein S-100 and others. MPNT can occur in the urogenital region. The differential diagnosis on clinical grounds must include Ewing's and soft tissue sarcomas, and also Wilms' tumor and its variants. MPNT are often wide spread in the urogenital region when first diagnosed. Response to radiotherapy and combination chemotherapy is limited. Radical surgery is not always possible. The prognosis therefore remains rather poor at this time. A selection of MPNT patients is presented to demonstrate the various problems associated with this diagnosis. MRI and CT of all patients showed large tumors with direct infiltration of the surrounding structures. MRI is the best imaging modality for diagnosis and therapy monitoring in these tumors, because of its high soft-tissue contrast.  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