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   3974篇
  免费   134篇
  国内免费   12篇
耳鼻咽喉   10篇
儿科学   48篇
妇产科学   51篇
基础医学   399篇
口腔科学   74篇
临床医学   473篇
内科学   1202篇
皮肤病学   47篇
神经病学   489篇
特种医学   59篇
外科学   341篇
综合类   12篇
预防医学   371篇
眼科学   25篇
药学   285篇
中国医学   2篇
肿瘤学   232篇
  2024年   17篇
  2023年   24篇
  2022年   71篇
  2021年   148篇
  2020年   77篇
  2019年   142篇
  2018年   155篇
  2017年   96篇
  2016年   100篇
  2015年   94篇
  2014年   175篇
  2013年   205篇
  2012年   330篇
  2011年   353篇
  2010年   218篇
  2009年   168篇
  2008年   259篇
  2007年   248篇
  2006年   250篇
  2005年   225篇
  2004年   205篇
  2003年   186篇
  2002年   164篇
  2001年   19篇
  2000年   11篇
  1999年   21篇
  1998年   33篇
  1997年   25篇
  1996年   17篇
  1995年   20篇
  1994年   12篇
  1993年   6篇
  1992年   2篇
  1991年   7篇
  1990年   7篇
  1989年   3篇
  1988年   3篇
  1987年   2篇
  1986年   3篇
  1985年   4篇
  1981年   3篇
  1980年   1篇
  1979年   1篇
  1976年   1篇
  1971年   1篇
  1962年   1篇
  1961年   1篇
  1960年   2篇
  1933年   1篇
  1929年   1篇
排序方式: 共有4120条查询结果,搜索用时 15 毫秒
81.
High plasma levels of von Willebrand factor (vWF) have been associated with the risk of thromboembolic disease. As a complex trait, this phenotype must be influenced by genetic and environmental factors. Among the genetic factors, only the ABO gene located on chromosome 9q34 has been clearly linked to the plasma levels of vWF. This locus explains about 30-40% of the genetic variability. Therefore, the source of the majority of the genetic component remains to be identified. To search for these unknown loci, we conducted a genomewide linkage screen for genes affecting normal variation in vWF levels in 21 Spanish families as part of the GAIT (Genetic Analysis of Idiopathic Thrombophilia) Project. The results showed that the strongest linkage signal (LOD =3.46, p = 0.00003) for vWF was found on chromosome 9q34 at the DNA marker D9S290, where the ABO gene is located. Additional suggestive linkage signals were found on chromosomes 2q23.2 (LOD = 1.65, p = 0.003) and 1p36.13 (LOD =1.32, p = 0.007). After refining the linkage analysis, conditional to the ABO genotype, three additional loci on chromosomes 5, 6 and 22 showed LOD scores higher than 1, suggesting the presence of other genes linked to vWF levels. Curiously, no linkage signals were detected in other chromosome regions previously associated with vWF levels (like the structural VWF gene on 12p13.2 or Lewis blood group gene on 19q13).These results indicate that these loci are not important genetic determinants of the normal variation of vWF levels. Our results indicate that the ABO locus is the major genetic determinant of the plasma levels of the vWF in Spanish population. It is possible that there are other potential regions on chromosomes 1, 2, 5, 6 and 22 that influence this thrombosis risk factor. However, the structural vWF gene itself has a very low influence (if any) on the plasma levels of vWF.  相似文献   
82.
6-aminonicotinamide (6-AN) is a niacin antagonist, which leads to degeneration of gray matter astrocytes mainly in the brainstem. We have examined the role of interleukin-6 (IL-6) in this degenerative process by using transgenic mice with astrocyte-targeted IL-6 expression (GFAP-IL6 mice). This study demonstrates that transgenic IL-6 expression significantly increases the 6-AN-induced inflammatory response of reactive astrocytes, microglia/macrophages, and lymphocytes in the brainstem. Also, IL-6 induced significant increases in proinflammatory cytokines IL-1, IL-12, and tumor necrosis factor-alpha as well as growth factors basic fibroblast growth factor (bFGF), transforming growth factor-beta, neurotrophin-3, angiopoietin, vascular endothelial growth factor, and the receptor for bFGF. In accordance, angiogenesis was increased in GFAP-IL6 mice relative to controls after 6-AN. Moreover, oxidative stress and apoptotic cell death were significantly reduced by transgenic IL-6 expression. IL-6 is also a major inducer in the CNS of metallothionein I and II (MT-I+II), which were significantly increased in the GFAP-IL6 mice. MT-I+II are antioxidants and neuroregenerative factors in the CNS, so increased MT-I+II levels in GFAP-IL6 mice could contribute to the reduction of oxidative stress and cell death in these mice.  相似文献   
83.
84.
85.
BACKGROUND: The use of unconventional therapies is growing in western countries. Few studies on their frequency and rationale among multiple sclerosis (MS) patients have been carried out in Europe. OBJECTIVE: To assess the frequency of use of unconventional therapies among MS patients and to explore associated clinical variables. METHODS: Structured questionnaires were given to 380 consecutive patients seen at two hospital-based MS clinics in Barcelona. Clinical and demographical data were recorded at the same time. The questionnaire inquired about demographical features, education, income, use of unconventional therapies for MS and satisfaction with conventional medicine both in general and specifically in MS. RESULTS: The response rate was 50.78%. Forty-one per cent of patients admitted using unconventional therapies during the previous year. Low levels of satisfaction with conventional medicine in general and for MS, and higher Expanded Disability Status Scale (EDSS) scores (EDSS mean: 4.43 in users versus 3.48 in nonusers) were significantly associated with use of unconventional therapies. CONCLUSION: Use of unconventional therapies is not rare among MS patients, and it is associated with high disability levels and dissatisfaction with conventional medicine.  相似文献   
86.
Bcl-2/IgH rearrangement is the molecular hallmark of follicular lymphoma (FL) which is present in 70-90% of the cases at diagnosis. The clinical significance of this feature is controversial. The aim of this study was to analyze the bcl-2/IgH rearrangement by means of a PCR technique, and to correlate molecular findings with clinical characteristics and outcome. Sixty-nine patients (median age, 53 years; male/female ratio: 35/34) diagnosed with FL in a single institution were included in the study. A total of 77 DNA samples were analyzed, 54 were obtained from lymph node biopsy and 23 from peripheral blood or bone marrow. Bcl-2/IgH rearrangement was assessed for both the major breakpoint region (MBR) and the minor cluster region (mcr) breakpoints by a PCR technique. Thirty-nine out of sixty patients (65%) with assessable samples were found to have a bcl-2/IgH rearrangement in the MBR breakpoint, whereas bcl-2/IgH rearrangement in mcr was observed in one patient (2%) and no rearrangement at MBR or mcr in the remaining 20 patients (33%). Regarding the initial characteristics, patients with bcl-2/IgH rearrangements at MBR or mcr were younger (<65 years) than those with no rearrangement at these sites (p = 0.0001). No differences were found according to bcl-2/IgH rearrangement in terms of complete response rate, time to treatment failure and overall survival. In our series bcl-2/IgH rearrangement at MBR or mcr, which was found in 67% of the patients, was not correlated with response to treatment, survival nor time-to-treatment-failure.  相似文献   
87.
Access to information on cancer prevention and treatment is often difficult for ethnic or low socio-economic groups. This study aimed to ascertain level of knowledge about cancer, and breast cancer in particular, in Spanish women from low socio-economic groups participating in literacy schemes. A study specific questionnaire was administered to 541 women All participants were married with a median of 2 children, and a total family income of less than 10,000 euros per year. The main themes covered: understanding of and access to screening, knowledge about cancer risk, diagnosis and prognosis.The majority of these women (66%) feel they have no control over getting cancer and 26% report that it can be caught from others. Most believe that a mammogram is the best method of diagnosis (87%) but a minority (14%) agree with the statement that breast cancer can be caused by breast feeding. In general, younger women are better informed and more optimistic about prognosis.In Spain there are problems in disseminating information about cancer to lower social-economic groups. These results confirm that more cancer education needs to be directed to low income and socially deprived groups.  相似文献   
88.
Hydroxyaminolactams have been used as constrained surrogates of the Ser-Leu dipeptide in the synthesis of analogues of the cycloheptapeptide stylostatin 1 (2). The rate of cyclization through formation of the Ile-Pro amide bond allowed us to prove that the valerolactams used induced a turn in the linear precursor. Ring closure at the Pro-Phe amide bond was much quicker and provided access to larger amounts of the target structures, with high purity. The conformation of psi-stylostatin 4 was compared to that of native stylostatin 1 using NMR analysis. The ability of three psi-stylostatins and the native stylostatin 1 to inhibit growth of cancer cell lines was tested. None of the compounds showed activity below 1 microM. A possible relationship between the decrease in activity and the presence of the piperidone Ser-Leu surrogate is considered.  相似文献   
89.
90.
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