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   2918篇
  免费   164篇
  国内免费   28篇
耳鼻咽喉   9篇
儿科学   77篇
妇产科学   66篇
基础医学   508篇
口腔科学   110篇
临床医学   244篇
内科学   574篇
皮肤病学   35篇
神经病学   301篇
特种医学   120篇
外科学   247篇
综合类   21篇
预防医学   265篇
眼科学   32篇
药学   221篇
中国医学   23篇
肿瘤学   257篇
  2024年   3篇
  2023年   38篇
  2022年   102篇
  2021年   140篇
  2020年   93篇
  2019年   96篇
  2018年   105篇
  2017年   86篇
  2016年   97篇
  2015年   82篇
  2014年   139篇
  2013年   162篇
  2012年   261篇
  2011年   249篇
  2010年   131篇
  2009年   134篇
  2008年   188篇
  2007年   185篇
  2006年   175篇
  2005年   146篇
  2004年   90篇
  2003年   124篇
  2002年   104篇
  2001年   19篇
  2000年   11篇
  1999年   14篇
  1998年   14篇
  1997年   10篇
  1995年   15篇
  1994年   5篇
  1993年   12篇
  1992年   11篇
  1991年   5篇
  1990年   10篇
  1989年   5篇
  1988年   3篇
  1986年   4篇
  1985年   5篇
  1984年   6篇
  1983年   3篇
  1982年   4篇
  1980年   3篇
  1979年   2篇
  1977年   2篇
  1976年   2篇
  1975年   2篇
  1972年   2篇
  1970年   2篇
  1964年   1篇
  1932年   1篇
排序方式: 共有3110条查询结果,搜索用时 0 毫秒
1.
2.
3.
Data from 4,300 consecutive cases following prenatal diagnosis by transcervical (TC) CVS (n = (1,570) and transabdominal (TA) CVS (n = 2,370) were evaluated. In the follow-up study only infants examined by a physician were included. Gestational age varied between 8.5 and 11.6 weeks (mean 10.3 weeks) for TC-CVS and between 9.3 and 20 weeks (mean 12.3 weeks) for TA-CVS 98% of TC-CVS was performed at 9–10 weeks, 80.7% of TA-CVS procedures were carried out at 12–15 weeks. Selective termination took place in 97 cases of TC-CVS (6.1%) and in 72 cases of TA-CVS (2.6%). Another 8 Women had a termination for psychosocial reasons, resulting in 4,123 (1,469 TC, 2,645 TA) continuing pregnancies. The overall fetal loss rare <28 weeks was 5.4% (n = 80) for TC-CVS and 2.6% (n = 70) for TA-CVS. The overall incidence of congenital abnormalities after birth was 0.9%. Two terminal transversal limb defects were detected in the TC-CVS group (0.14%) against one (0.04%) in the TA-CVS group. © 1993 Wiley-Liss, Inc.  相似文献   
4.
Serum samples were collected from 40 patients with enlarged lymph nodes. Lymph node and bone marrow biopsies were performed and processed as usual. Tumor necrosis factor-alpha (TNF alpha) was determined in the sera by factor test human TNF alpha ELISA kit. Histopathological studies of lymph node and bone marrow biopsies were evaluated. The data obtained from this study showed that bone marrow was involved in only 5 patients and their TNF showed the lowest level in this study with a mean level 50 pg/ml. The highest level of TNF occurred in cases with granulomatous lymphadenitis (124 pg/ml) followed by reactive lymphadenitis (105 pg/ml). It can be considered that TNF reflects the immune status of the patient and its study in the serum can be of help in evaluating the progress of the disease. An extended study is need to evaluate the role of TNF-alpha as a prognostic marker in malignancy.  相似文献   
5.
6.
7.
The concept of vasculogenic mimicry has been introduced to define periodic acid-Schiff (PAS)-positive channels and loops lined by tumor cells, instead of endothelium, able to contribute to microcirculation in uveal melanomas. Previous studies have shown that the PAS-positive patterns are associated with a poor prognosis in uveal melanoma. The aim of the current study was to investigate whether vasculogenic mimicry has a prognostic impact in pT3 and pT4 cutaneous melanoma. Fifteen patients with pT3 and pT4 cutaneous melanoma who did not experience progression after 10 years of follow-up and 30 matched controls who underwent progression were selected. Tumor sections were stained with PAS reaction, omitting the nuclear counterstaining. For immunohistochemistry, sections were stained with CD31, CD105 (endoglin), and laminin. Differences in the distribution of the PAS-positive patterns and a series of clinicopathological variables were evaluated by the Pearson chi(2) and Mann-Whitney U tests. We observed PAS-positive linear sheets, arcs, elliptical loops, and networks encircling roundish to oval aggregates of melanoma cells. The overall distribution of the PAS-positive patterns did not match with the blood microvessels' architecture as detected by immunohistochemical analysis. No statistically significant differences in the distribution of PAS-positive patterns were found between cases and controls. The presence of a parallel pattern correlated significantly with thickness (P = 0.04), whereas an inverse correlation was found with vessel area (P = 0.05). In conclusion, our results suggest that there is a mismatch between vasculogenic mimicry and tumor angiogenesis and do not support any prognostic role of vasculogenic mimicry in thick cutaneous melanoma.  相似文献   
8.
The bcl-2 protein is a membrane protein involved in prolonging cell survival by inhibiting apoptosis. The HER-2 oncogene, which is located on chromosome 17 and encodes for a tyrosine-kinase growth factor receptor, is amplified and HER-2/neu is overexpressed in 25% to 30% of breast carcinomas. The authors analyzed the bcl-2 expression and the bcl-2 gene and HER-2/neu overexpression and amplification in FIGO stage IIIC, serous, G3, ovarian carcinomas obtained from living patients who had no evident disease 5 years after primary treatment compared with ovarian carcinomas obtained from patients, matched for stage, grade of differentiation, and treatment, who had died of progression of disease no later than 2 years after primary treatment. bcl-2 overexpression was statistically correlated with progression of disease during first-line chemotherapy (P=0.021). The HER-2/neu status was found not to correlate with progression of disease during first-line chemotherapy. Both bcl-2 and HER-2/neu expression were not statistically associated with the clinical outcome of ovarian cancer patients. Gene amplification of the HER-2/neu chromosome 17 was found in all the HER-2/neu, 3+ score, positive-staining ovarian carcinomas. None of the analyzed samples revealed a translocation t(14;18)(q32;q21) in the bcl-2 gene. The knowledge of additional prognostic or even predictive factors, such as bcl-2 expression, in patients with advanced ovarian carcinoma before the primary chemotherapeutic treatment may help in the management of patients who require a more tailored treatment. In addition, the gene amplification of the HER-2/neu suggests that HER-2 is a potential target for treatment in ovarian cancer.  相似文献   
9.
Apoptotic defects and impaired clearance of cellular debris are considered key events in the development of autoimmunity, as they can contribute to autoantigen overload, and may initiate an autoimmune response. The pentraxins are a group of highly conserved proteins including the short pentraxins, C-reactive protein (CRP) and serum amyloid-P (SAP), and the long pentraxin-3 (PTX3), which are all involved in innate immunity and in acute-phase responses. Mannan-binding lectin (MBL) is an activator of the complement system, and Apolipoprotein A-1 (Apo A-1) is pivotal in the cholesterol homeostasis and has anti-inflammatory properties. In addition to their role in innate immunity and inflammation, each of these five proteins participates in the removal of damaged and apoptotic cells. In this review, we discuss the clinical significance of different levels of these proteins, their role in the induction or protection from autoimmunity, and the presence of specific autoantibodies against them in the different autoimmune diseases.  相似文献   
10.
Rat thymic epithelial cells (TEC) in long-term culture were characterized by anticytokeratin monoclonal antibodies (mAbs) and electron microscopy. Phenotypic analysis performed by a large panel of mAbs showed that the highest percentage of these cells was of the subcapsular/medullary type. Recombinant rat interferon (IFN)-gamma up-regulated class-I and class-II MHC expression by TEC in culture as confirmed by immunohistochemistry and flow cytometry, but did not significantly alter other cell markers. TEC supernatants of IFN-gamma- treated cultures showed higher interleukin-6 (IL-6) activity, compared to the control, as determined by proliferation of the IL-6-sensitive B9-cell line. Increased IL-6 activity was probably not a consequence of increased TEC number in IFN-gammatreated cultures because IFN did not significantly stimulate TEC proliferation in vitro. In contrast, IL-6 significantly stimulated TEC proliferation, indicating that this cytokine is not only a regulatory molecule for T-cell proliferation, but could also be an autocrine growth factor for thymic epithelium.  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