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:      
  示例: 沙坡头地区,人工植被区,变化  检索词用空格隔开表示必须包含全部检索词,用“,”隔开表示只需满足任一检索词即可!
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   3707篇
  免费   101篇
  国内免费   9篇
耳鼻咽喉   9篇
儿科学   111篇
妇产科学   116篇
基础医学   494篇
口腔科学   31篇
临床医学   334篇
内科学   929篇
皮肤病学   69篇
神经病学   322篇
特种医学   72篇
外科学   350篇
综合类   6篇
预防医学   155篇
眼科学   28篇
药学   318篇
中国医学   7篇
肿瘤学   466篇
  2025年   1篇
  2024年   18篇
  2023年   25篇
  2022年   74篇
  2021年   101篇
  2020年   78篇
  2019年   94篇
  2018年   127篇
  2017年   80篇
  2016年   94篇
  2015年   97篇
  2014年   137篇
  2013年   179篇
  2012年   265篇
  2011年   303篇
  2010年   150篇
  2009年   168篇
  2008年   285篇
  2007年   256篇
  2006年   238篇
  2005年   242篇
  2004年   213篇
  2003年   185篇
  2002年   190篇
  2001年   17篇
  2000年   13篇
  1999年   18篇
  1998年   30篇
  1997年   18篇
  1996年   26篇
  1995年   10篇
  1994年   13篇
  1993年   16篇
  1992年   11篇
  1991年   5篇
  1990年   7篇
  1989年   4篇
  1988年   2篇
  1986年   3篇
  1985年   4篇
  1984年   4篇
  1983年   4篇
  1982年   6篇
  1981年   1篇
  1980年   1篇
  1979年   1篇
  1977年   3篇
排序方式: 共有3817条查询结果,搜索用时 15 毫秒
21.
AIM: To evaluate the safety and efficacy of the permanent high interventricular septal pacing in a long term follow up, as alternative to right ventricular apical pacing.METHODS: We retrospectively evaluated: (1) 244 patients (74 ± 8 years; 169 men, 75 women) implanted with a single (132 pts) or dual chamber (112 pts) pacemaker (PM) with ventricular screw-in lead placed at the right ventricular high septal parahisian site (SEPTAL pacing); (2) 22 patients with permanent pacemaker and low percentage of pacing (< 20%) (NO pacing); (3) 33 patients with high percentage (> 80%) right ventricular apical pacing (RVA). All patients had a narrow spontaneous QRS (101 ± 14 ms). We evaluated New York Heart Association (NYHA) class, quality of life (QoL), 6 min walking test (6MWT) and left ventricular function (end-diastolic volume, LV-EDV; end-systolic volume, LV-ESV; ejection fraction, LV-EF) with 2D-echocardiography.RESULTS: Pacing parameters were stable during follow up (21 mo/patient). In SEPTAL pacing group we observed an improvement in NYHA class, QoL score and 6MWT. While LV-EDV didn’t significantly increase (104 ± 40 mL vs 100 ± 37 mL; P = 0.35), LV-ESV slightly increased (55 ± 31 mL vs 49 ± 27 mL; P = 0.05) and LV-EF slightly decreased (49% ± 11% vs 53% ± 11%; P = 0.001) but never falling < 45%. In the RVA pacing control group we observed a worsening of NYHA class and an important reduction of LV-EF (from 56% ± 6% to 43% ± 9%, P < 0.0001).CONCLUSION: Right ventricular permanent high septal pacing is safe and effective in a long term follow up evaluation; it could be a good alternative to the conventional RVA pacing in order to avoid its deleterious effects.  相似文献   
22.
23.
A new mutation (Ile 436 Lys) was found in a cluster of patients in northeastern Italy. The mutation was present in five patients at the homozygote level and in one patient as a compound heterozygote with an already known mutation namely Glu 117 stop. All these patients showed a mild bleeding tendency mainly associated with deliveries or surgery. The first two patients were two sisters, and their parents were consanguineous. The third patient was the only homozygote in the family, and parents apparently were not consanguineous. The fourth and fifth patients were a brother and a sister, and in this case too, parents were not consanguineous. The sixth patient, a compound heterozygote, negated also the existence of consanguinity between his parents. There were also seven heterozygotes among the family members of the patients homozygous for this new mutation (Ile 436 Lys). Finally, there were two heterozygotes for the Glu 117 stop mutation in the family of the sixth patient. The heterozygotes, regardless of the mutation, were asymptomatic. The Ile436Lys mutation is characterized by low factor XI activity and antigen, namely is a cross-reaction material negative form. Molecular modeling indicates that the Ile436Lys mutation causes a large conformational change within the 432-442 loop. No relation could be traced among the different families; however, all their ancestors were autochthonous of the same two small towns. Furthermore, no Jewish ancestry could be found. The close geographical area in which all these patients were found and the absence of the same mutation in the general population of the area strongly suggests a founder effect and that the mutation is responsible for the defect. The compound heterozygosis with the Glu 117 stop mutation, common among Jews, was not surprising because of the past strict ties of the Republic of Venice with the Middle East.  相似文献   
24.
This study analyzes the pathologic and molecular features of 5 cases of primary cutaneous large B-cell lymphoma of the leg (PCLBCL-leg), recently included in the European Organization for Research and Treatment of Cancer (EORTC) classification of primary cutaneous lymphoma. PCLBCL-leg accounts for 5% to 10% of all primary cutaneous B-cell lymphoma (PCBCL), usually affects elderly patients and carries a worse prognosis than other forms of PCBCL. It has been proposed that the malignant cells of PCLBCL-leg originate from germinal center (GC)-related cells, but their effective normal counterpart is unclear, and the rationale behind the inclusion of this lymphoma as a separate entity is based on its prognosis rather than on its proved histogenesis. All of our cases of PCLBCL-leg morphologically resembled diffuse large B-cell lymphoma (DLBCL), but to better define their histogenesis, we also analyzed various phenotypic and genotypic markers, including mutations of the Ig and of BCL-6 genes, as well as expression of the bcl-6, MUM1, and CD138/syndecan-1 proteins. Immunohistochemically, all of our cases stained for the L-26/CD20cy and CD79a antigens and expressed the bcl-2, bcl-6, and MUM-1 proteins but were negative for both the CD10/CALLA and CD138 antigens. With respect to molecular analysis, the lymphoma population of all PCLBCL-leg carried hypermutation of Ig genes, and all but 1 case also harbored mutations of the BCL-6 gene. Our results indicate that PCLBCL-leg are similar both under the morphofunctional and molecular profiles to most DLBCL of other sites. Thus, caution seems justified before definitely considering PCLBCL of the leg as a distinct entity.  相似文献   
25.
AIM: To compare the site, age and gender of cases of colorectal cancer (CRC) and polyps in a single referral center in Rome, Italy, during two periods.METHODS: CRC data were collected from surgery/pathology registers, and polyp data from colonoscopy reports. Patients who met the criteria for familial adenomatous polyposis, hereditary non-polyposis colorectal cancer syndrome or inflammatory bowel disease were excluded from the study. Overlap of patients between the two groups (cancers and polyps) was carefully avoided. The χ2 statistical test and a regression analysis were performed.RESULTS: Data from a total of 768 patients (352 and 416 patients, respectively, in periods A and B) who underwent surgery for cancer were collected. During the same time periods, a total of 1693 polyps were analyzed from 978 patients with complete colonoscopies (428 polyps from 273 patients during period A and 1265 polyps from 705 patients during period B). A proximal shift in cancer occurred during the latter years for both sexes, but particularly in males. Proximal cancer increased > 3-fold in period B compared to period A in males [odds ratio (OR) 3.31, 95%CI: 2.00-5.47; P < 0.0001). A similar proximal shift was observed for polyps, particularly in males (OR 1.87, 95%CI: 1.23-2.87; P < 0.0038), but also in females (OR 1.62, 95%CI: 0.96-2.73; P < 0.07).CONCLUSION: The prevalence of proximal proliferative colonic lesions seems to have increased over the last decade, particularly in males.  相似文献   
26.
Hypoxia-inducible factor-1α (HIF-1α) is frequently overexpressed and activated in many cancer types. However, its regulation and function in thyroid carcinomas are only partially known. Aim of our study was to demonstrate that adaptation to the hypoxic micro-environment by human papillary thyroid carcinoma (PTC) cells, in the absence of leukocyte infiltrate, induces a “molecular inflammation” process characterized by the expression of a large set of genes normally involved in inflammation. To address this, tumor, peritumor or normal host tissue from eleven human PTC surgical samples, were separated by laser capture microdissection (LCMD) and studied by real-time quantitative PCR and Western blot. In such condition, we observed an increased expression and activation of HIF-1α, NF-kB and pro-inflammatory genes only in tumor tissues. Importantly, an anti-inflammatory gene such as SOCS-1 was markedly down-regulated in tumor tissue compared to surrounding normal host tissue. Similar results were found in fine-needle aspiration biopsy (FNAB)-derived specimens from PTC and in hypoxic human papillary thyroid tumor cell line, BCPAP. Moreover, we also detected an elevated expression of metalloproteinase-9 (MMP9) both in solid tumor and in hypoxic-treated BCPAP cells. Our findings reveal that, in human PTC tumor, hypoxic conditions are accompanied by up-regulation of pro-inflammatory genes, down-regulation of anti-inflammatory genes and increased expression of MMP9. We propose that a better understanding of the pro- and anti-inflammatory pathways involved in the “molecular inflammation” process even in the absence of leukocyte, may help to clarify progression toward malignancy and may prove useful for new anti-tumor strategy.  相似文献   
27.
Uterine sarcomas are rare tumors that account for 3% to 7% of uterine cancers. Their histopathologic classification was revised by the World Health Organization (WHO) in 2003. The objectives of this study were to determine the frequency of different subtypes of uterine sarcoma applying the WHO criteria to a series of cases, compare the outcome of patients with different subtypes, and compare their immunoprofiles using a panel of immunomarkers. Thirty-four uterine sarcomas were identified for a 20-year period (1988-2008). Eighteen benign tumors of smooth muscle or endometrial stromal origin served as a comparison group. A tissue microarray was prepared and immunostaining performed for 10 selected oncoproteins involved in cell proliferation (Ki-67, P53, p16, and phosphatase and tensin homolog [PTEN]), cell differentiation (CD10, h-caldesmon, estrogen receptor, and progesterone receptor), and apoptosis (bcl-2 and Twist). Hierarchical clustering analysis of the immunohistochemical results was performed. The uterine sarcomas were classified as follows: 20 leiomyosarcomas, 9 endometrial stromal sarcomas, and 5 undifferentiated endometrial sarcomas. The outcome for patients with uterine sarcoma was poor, irrespective of histologic type, even for those with stage I tumors. Of the patients with follow-up available, 12 (67%) of 18 with leiomyosarcoma, 4 of 5 with undifferentiated sarcoma, and 4 of 7 with endometrial stromal sarcoma experienced recurrence and 8 patients with high-grade sarcomas died of tumor. In our series, most uterine sarcomas were leiomyosarcomas. Comparison was made between leiomyosarcomas that recurred and those with a favorable outcome and 3 patients with leiomyosarcoma without evidence of recurrence on long-term follow-up had tumors that were negative/low expressors of Ki-67, p53, p16, and Twist, with strong expression of bcl-2. A subset of undifferentiated endometrial sarcomas composed of cells with uniform nuclei may be a separate entity from those with nuclear anaplasia and may be related to low-grade endometrial stromal sarcomas. It may be possible to identify a subset of leiomyosarcomas with a favorable prognosis based on staining with a panel of immunomarkers for cell proliferation and apoptosis.  相似文献   
28.
TACI and BAFF-R mediate isotype switching in B cells   总被引:17,自引:0,他引:17       下载免费PDF全文
The tumor necrosis factor family members BAFF and APRIL induce Ig isotype switching in human B cells. We analyzed the ability of BAFF and APRIL to induce isotype switching in murine B cells to IgG1, IgA, and IgE. APRIL and BAFF each engage two receptors, transmembrane activator and calcium-modulator and cytophilin ligand interactor (TACI) and B cell maturation antigen (BCMA), on B cells. In addition, BAFF engages a third receptor on B cells, BAFF-R. To determine the role of these receptors in isotype switching, we examined B cells from mice deficient in TACI, BCMA, and BAFF-R. The results obtained indicate that both TACI and BAFF-R are able to transduce signals that result in isotype switching.  相似文献   
29.
Interleukin-1β (IL-1β) is a pro-inflammatory cytokine that contributes to neuronal injury in various degenerative diseases, and is therefore a potential therapeutic target. It exerts its biological effect by activating the interleukin-1 receptor type I (IL-1RI) and recruiting a signalling core complex consisting of the myeloid differentiation primary response protein 88 (MyD88) and the IL-1R accessory protein (IL-1RAcP). This pathway has been clearly described in the peripheral immune system, but only scattered information is available concerning the molecular composition and distribution of its members in neuronal cells. The findings of this study show that IL-1RI and its accessory proteins MyD88 and IL-1RAcP are differently distributed in the hippocampus and in the subcellular compartments of primary hippocampal neurons. In particular, only IL-1RI is enriched at synaptic sites, where it co-localises with, and binds to the GluN2B subunit of NMDA receptors. Furthermore, treatment with NMDA increases IL-1RI interaction with NMDA receptors, as well as the surface expression and localization of IL-1RI at synaptic membranes. IL-1β also increases IL-1RI levels at synaptic sites, without affecting the total amount of the receptor in the plasma membrane. Our results reveal for the first time the existence of a dynamic and functional interaction between NMDA receptor and IL-1RI systems that could provide a molecular basis for IL-1β as a neuromodulator in physiological and pathological events relying on NMDA receptor activation.  相似文献   
30.
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