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   11524篇
  免费   892篇
  国内免费   140篇
耳鼻咽喉   113篇
儿科学   431篇
妇产科学   222篇
基础医学   1577篇
口腔科学   217篇
临床医学   1070篇
内科学   2562篇
皮肤病学   238篇
神经病学   1019篇
特种医学   614篇
外国民族医学   1篇
外科学   1791篇
综合类   126篇
一般理论   4篇
预防医学   807篇
眼科学   151篇
药学   686篇
中国医学   34篇
肿瘤学   893篇
  2023年   65篇
  2022年   122篇
  2021年   257篇
  2020年   164篇
  2019年   289篇
  2018年   346篇
  2017年   255篇
  2016年   254篇
  2015年   285篇
  2014年   388篇
  2013年   491篇
  2012年   630篇
  2011年   669篇
  2010年   453篇
  2009年   388篇
  2008年   483篇
  2007年   591篇
  2006年   522篇
  2005年   501篇
  2004年   417篇
  2003年   374篇
  2002年   364篇
  2001年   334篇
  2000年   343篇
  1999年   331篇
  1998年   192篇
  1997年   181篇
  1996年   189篇
  1995年   145篇
  1994年   145篇
  1993年   122篇
  1992年   206篇
  1991年   226篇
  1990年   194篇
  1989年   205篇
  1988年   153篇
  1987年   183篇
  1986年   149篇
  1985年   130篇
  1984年   88篇
  1983年   64篇
  1982年   53篇
  1981年   57篇
  1980年   51篇
  1979年   65篇
  1978年   56篇
  1977年   53篇
  1976年   58篇
  1975年   46篇
  1973年   36篇
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
61.
62.
We have studied the cross-reactivity between L. perenne, S. cereale, P. pratense, C. dactylon, and Ph. communis. The results obtained demonstrate that L. perenne, S. cereale, and P. pratense have strong cross-reactivity. C. dactylon has a number of allergens that cross-react with the rest of the grasses studied but they are minor allergens. Ph. communis possesses a moderate cross-reactivity with the species of the group but it has, as well, individual allergens.  相似文献   
63.
64.
The last decade has witnessed increasing application of human cytogenetic technology to prenatal chromosome analysis. However, unlike the rather uniform peripheral blood T-lymphocyte system which has provided most of our experience in human cytogenetics, long-term amniotic-fluid cell cultures display extreme cellular heterogeneity and disproportionate growth of certain cell types as a consequence of clonal amplification. When they enter cell culture, many of these cells are approching the terminal stages of their respective life spans and may have accumulated chromosomal aberrations. Concern about the possibility of true fetal mosaicism seems warranted chiefly in situations were multiple colonies display potentially viable aberrations. Clonal analysis, preferable of multiple clonal types, and attention to details of clonal morphology are likely to minimize diagnostic errors and undue apprehension resulting from mosaicism in amniotic-fluid cell cultures.  相似文献   
65.
Calcium phosphate cements are used for bone defect filling and they may also be used as delivery systems for active agents. The physicochemical behaviour of an ionic cement, with a final composition of hydroxyapatite, containing tetracycline hydrochloride was investigated. Chemical characterisation, X-ray diffraction analysis, compressive strength and tensile strength were performed. It is known that the antibiotic can be adsorbed on calcium phosphate compounds and the presence of chloride ions can strongly influence the behaviour of the cement. Adding more than 1% (w/w) of 95% pure tetracycline hydrochloride in the solid phase led to a cement with poor mechanical properties, but which, in addition to hydroxyapatite, contained residual starting reagents. For this reason, experiments were also performed with tetracycline previously treated with a calcium sulphate solution. Using a treated tetracycline, it was possible to introduce at least 7% (w/w) of active ingredient whilst still allowing the reaction to proceed to completion i.e. the formation of hydroxyapatite with good mechanical properties. Therefore, treating the tetracycline HCI with calcium sulphate solution prior to reaction conserved the activity of the antibiotic, limited the influence of the antibiotic on the cement evolution and retained the physical properties of the cement.  相似文献   
66.
Impaired expression of the FMR1 gene is responsible for the fragile X mental retardation syndrome. The FMR1 gene encodes a cytoplasmic protein with RNA-binding properties. Its complex alternative splicing leads to several isoforms, whose abundance and specific functions in the cell are not known. We have cloned in expression vectors, cDNAs corresponding to several isoforms. Western blot comparison of the pattern of endogenous FMR1 proteins with these transfected isoforms allowed the tentative identification of the major endogenous isoform as ISO 7 and of a minor band as an isoform lacking exon 14 sequences (ISO 6 or ISO 12), while some other isoforms (ISO 4, ISO 5) were not expressed at detectable levels. Surprisingly, in immunofluorescence studies, the transfected splice variants that exclude exon 14 sequences (and have alternate C-terminal regions) were shown to be nuclear. Such differential localisation was however not seen in subcellular fractionation studies. Analysis of various deletion mutants suggests the presence of a cytoplasmic retention domain encoded in exon 14 and of a nuclear association domain encoded within the first eight exons that appear however to lack a typical nuclear localisation signal.   相似文献   
67.
68.
Examined the utility of a new parent-report measure designedspecifically for pediatric inpatients, the Behavioral Upsetin Medical Patients-Revised (BUMP-R). The BUMP-R was administeredto 151 mothers of hospitalized children ages 4–12 yearsthe day following the child's hospital admission. The BUMP-Rdemonstrated good internal consistency and a factor analysisrevealed four factors identified as negativity/agitation, amiability,dysphoria, and noncom-pliance. Children exhibiting behavioraldistress at home were more likely to experience adjustment problemsupon hospitalization. Demographic and illness-related variableswere not substantial risk factors for hospital adjustment difficulties.  相似文献   
69.
Heat shock protein 60 (HSP60) from Chlamydia pneumoniae was described to trigger in vitro inflammatory and cytokine responses including TNF and IL-12p40. Although it can be found in atherosclerotic plaques of patients, the stimulatory potential of chlamydial and other HSP60 in vivo is unclear. We now report that chlamydial HSP60 fails to induce TNF expression in vivo, and significant serum levels of IL-12p40 are only found upon intraperitoneal injection of high doses of HSP60 or after intravenous application. Upon purification of chlamydial HSP60 with polymyxin B-agarose columns, its ability to induce TNF secretion in vitro is much reduced. However, purified chlamydial HSP60 causes increased serum levels of the CXC chemokines KC and MIP2 in vivo, as well as a strong accumulation of polymorphonuclear neutrophils (PMN) in the peritoneal cavity upon intraperitoneal challenge. With respect to PMN accumulation, chlamydial HSP60 is more potent than endotoxin or the CpG oligonucleotide 1668. The responses observed are completely abolished in Toll-like receptor (TLR)2/4-double-deficient mice, while single-deficient mice respond almost normally. Furthermore, KC induction and PMN accumulation are largely dependent on MyD88. In conclusion, HSP60 from C. pneumoniae triggers inflammatory responses in vivo that differ from responses induced by endotoxin or CpG oligonucleotides and are dependent on TLR2 and 4.  相似文献   
70.
Respiratory syncytial virus (RSV) infection in adult rats causes exaggerated inflammation after sensory nerve stimulation in the extrapulmonary, but not in the intrapulmonary airways. The goal of this study was to analyze neurogenic inflammation in weanling F-344 rats infected with RSV 18 +/- 2 d after birth. Five days after RSV inoculation, the extravasation of Evans blue-labeled albumin after nerve stimulation was significantly greater in the intrapulmonary airways of RSV-infected weanling rats than in pathogen-free control rats. In contrast, no difference was found in the extrapulmonary airways. The level of messenger RNA (mRNA) encoding the substance P (SP) receptor (neurokinin 1 [NK1]) increased fourfold in RSV-infected lungs, whereas mRNA encoding the VIPR1 receptor for the antiinflammatory vasoactive intestinal peptide (VIP) increased to a much lesser degree. mRNAs encoding the other neurokinin (NK2) and VIP (VIPR2) receptors were not affected by the virus. Selective inhibition of the NK1 receptor abolished neurogenic inflammation in RSV-infected intrapulmonary airways. Also, neurogenic inflammation and NK1 receptor upregulation in infected lungs were inhibited by prophylaxis with a monoclonal antibody against RSV. These data suggest that RSV lower respiratory tract infection makes the intrapulmonary airways of young rats abnormally susceptible to the proinflammatory effects of SP by selectively upregulating the expression of NK1 receptors.  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