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   9387篇
  免费   836篇
  国内免费   55篇
耳鼻咽喉   116篇
儿科学   311篇
妇产科学   217篇
基础医学   1438篇
口腔科学   251篇
临床医学   788篇
内科学   2079篇
皮肤病学   252篇
神经病学   963篇
特种医学   343篇
外国民族医学   1篇
外科学   1325篇
综合类   45篇
一般理论   1篇
预防医学   717篇
眼科学   131篇
药学   633篇
中国医学   19篇
肿瘤学   648篇
  2023年   53篇
  2022年   115篇
  2021年   235篇
  2020年   155篇
  2019年   245篇
  2018年   307篇
  2017年   211篇
  2016年   234篇
  2015年   245篇
  2014年   304篇
  2013年   424篇
  2012年   537篇
  2011年   540篇
  2010年   339篇
  2009年   266篇
  2008年   428篇
  2007年   442篇
  2006年   455篇
  2005年   412篇
  2004年   374篇
  2003年   309篇
  2002年   327篇
  2001年   318篇
  2000年   305篇
  1999年   251篇
  1998年   103篇
  1997年   108篇
  1996年   86篇
  1995年   99篇
  1994年   71篇
  1993年   55篇
  1992年   210篇
  1991年   177篇
  1990年   163篇
  1989年   167篇
  1988年   151篇
  1987年   118篇
  1986年   112篇
  1985年   104篇
  1984年   98篇
  1983年   62篇
  1982年   46篇
  1981年   31篇
  1980年   37篇
  1979年   61篇
  1978年   32篇
  1977年   31篇
  1974年   40篇
  1973年   34篇
  1971年   32篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
The aim of the study was to determine possible factors related to the risk of developing recurrent bacterial respiratory tract infections in HIV-1-infected patients, regardless of the degree of immune cellular impairment. Thirty-three HIV-1 seropositive patients with previous repetitive bacterial respiratory tract infections (case group), 33 HIV-1 seropositive controls (matched by CD4-cell counts) without these antecedents and 27 healthy controls were studied before and after administration of pneumococcal and Haemophilus influenzae type b vaccines. Clinical or toxicological variables, cutaneous tests, complement factors, beta2-microglobulin, serum IgM, IgA, IgG and subclasses, specific antibodies (IgG, IgG2, IgA) against pneumococcal vaccine and polyribosylribitol phosphate (PRP), their avidity, opsonophagocytosis and IgG(2)m and Fc(gamma)RIIa allotypes were determined. A history of drug abuse (P = 0.001), less likelihood of receiving high activity antiretroviral treatment high activity antiretroviral treatment (HAART) (P = 0.01), higher levels of HIV-1 viral load (P < 0.05), serum IgG (P < 0.01) and beta2-microglobulin (P < 0.01) were observed in the case group. Also, a lower increase in specific antibodies to pneumococcal vaccine and PRP was demonstrated in the cases in comparison with the two control groups. No differences were observed in the avidity of antibodies, opsonophagocytic capacity or IgG(2)m and Fc(gamma)RIIa allotypes between the three groups. These data indicate that vaccination strategies against encapsulated bacteria can be unsuccessful in the HIV-1-infected patients presenting repetitive bacterial respiratory tract infections if behavioural aspects or measures to improve adherence to HAART therapies are not considered.  相似文献   
62.
After the identification of the interleukin (IL)-1 type II receptor as the prototype, decoy receptors have been identified for a number of members of the IL-1/IL-18, TNF, IL-10 and IL-13 receptor families. Moreover, the silent receptor D6 is a promiscuous decoy and scavenger receptor of inflammatory chemokines. The IL-1 decoy receptor is regulated by pro- and anti-inflammatory signals and its levels may serve as a readout of the activation of anti-inflammatory pathways, for instance by glucocorticoid hormones. Decoy receptors represent a strategy to tune inflammatory and polarized adaptive responses.  相似文献   
63.
Background: The morphogenetic conversion between yeast and hyphal growth forms appears to be crucial in the pathogenesis of invasive candidiasis, and can be regulated by environmental signals such as extracellular pH.  相似文献   
64.
Ekman-Westborg and Julin [1974: Oral Surg 38:217-222], described multiple macrodontia and multituberculism affecting the teeth without other anomalies (E-WJ). We describe a Chilean case in a 12-year-old with the typical dental alterations and with histopathologic findings that include absence of predentin layer and prominent reduced enamel epithelium. E-WJ is not a syndrome and we propose "multiple macrodontic multituberculism" as a better name for this anomaly of uncertain etiology affecting only the crowns of the teeth.  相似文献   
65.
The use of purified specific antibodies against HMG1 and HMG17 (high mobility group nonhistone chromosomal proteins), together with a very sensitive solid phase enzyme immunoassay, allows the detection of nanograms of these proteins free in solution or in chromatin native structure, and the measurement of their accessibility. The sensitivity of the assay is comparable to that of the radioimmunoassay, with the advantage of avoiding the handling of radioactive materials.  相似文献   
66.
Serial cytogenetic studies have been performed in four patients with myelodysplastic syndromes. In all four a 5q- alteration was present, but with a different pattern of presentation. One patient presented 5q- as the only alteration since diagnosis; two patients acquired this alteration during the course of the disease; and the fourth showed a 5q- plus other alterations since the first cytogenetic study. Likewise, three of the four patients showed a clone with trisomy 8 and without 5q-. According to these observations and others from the literature with similar cytogenetic behavior, we have analyzed the following points: 5q- as a primary event and as the only alteration, 5q- as a secondary event, 5q- plus other alterations, and presence of cytogenetically different clones. Analysis of these points suggests that the 5q- alteration can represent an early mutation conferring a slow capacity of expansion to the affected clones, with the possibility of cytogenetic evolution during the progression of the disease (about 30% of the patients). Likewise, the association of trisomy 8 clones with 5q- clones can be a nonrandom event.  相似文献   
67.
The products resulting from the reaction of PVC with sodium benzenethiolate were degraded to 0,3% at 180°C in the solid state and at 160°C in solution in trichlorobenzene. The polyene distribution of the polymers after degradation was studied by both UV-visible and resonance Raman spectroscopies, as a function of the degree of substitution. The results show that there are two types of behaviour: that of the PVC sample prior to the substitution reaction together with the samples modified up to a definite degree of substitution which depends on the starting isotactic content, and that of samples with higher degrees of substitution. The former group exhibits not only a steady improvement in thermal stability but also a preferential formation of polyenes of 7 – 9 double bonds whose concentration decreases with increasing degree of substitution. Conversely, for the second group of samples the thermal stability decreases with the degree of substitution and no specific absorption bands are observed. On the basis of earlier work on the selective substitution of the isotactic GTTG and heterotactic TTTG triads during the first stage of the reaction, the present results show that the bands at 393, 416, and 437 nm are related to specific polyenes which result from initiation by the above quoted conformations in PVC, a conclusion for which confirmatory evidence was obtained by resonance Raman spectroscopic examination of the samples. There is, therefore, clear evidence for the occurrence of two distinct degradation mechanisms, one involving initiation by the unstable triad conformations and the other via random initiation at stable and normal structures. To this may be added the initiation by defect structures, which have been extensively documented in the literature.  相似文献   
68.
69.
70.

Health agencies call for the immediate mobilization of existing interventions in response to numerous child and family mental health concerns that have arisen as result of the COVID-19 pandemic. Answering this call, this pilot study describes the rapid, full-scale change from a primarily clinic-based Parent–Child Interaction Therapy (PCIT) model to a virtual service model (i.e., I-PCIT) in an academic and community-based program in Miami, Florida. First, we describe the virtual service training model our program developed and its implementation with 17 therapists (MAge?=?32.35, 88.2% female, 47.1% Hispanic) to enable our clinic to shift from providing virtual services to a small portion of the families served (29.1%) to all of the families served. Second, we examine the effect of I-PCIT on child and caregiver outcomes during the 2-month stay-at-home period between March 16, 2020, and May 16, 2020, in 86 families (MChildAge?=?4.75, 71% Hispanic). Due to the rapid nature of the current study, all active participants were transferred to virtual services, and therefore there was no comparison or control group, and outcomes represent the most recently available scores and not treatment completion. Results reveal that I-PCIT reduced child externalizing and internalizing problems and caregiver stress, and increased parenting skills and child compliance with medium to large effects even in the midst of the COVID-19 pandemic. Finally, the study examined components of our virtual service training model associated with the greatest improvements in child and caregiver outcomes. Preliminary findings revealed that locally and collaboratively developed strategies (e.g., online communities of practice, training videos and guides) had the strongest association with child and caregiver outcomes. Implications for virtual service delivery, implementation, and practice in the midst of the COVID-19 pandemic are discussed.

  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