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   1149篇
  免费   17篇
  国内免费   1篇
电工技术   4篇
综合类   9篇
化学工业   20篇
金属工艺   6篇
机械仪表   6篇
建筑科学   5篇
能源动力   2篇
轻工业   17篇
水利工程   2篇
石油天然气   2篇
武器工业   1篇
无线电   23篇
一般工业技术   19篇
冶金工业   1009篇
原子能技术   3篇
自动化技术   39篇
  2023年   1篇
  2022年   1篇
  2021年   2篇
  2019年   5篇
  2017年   2篇
  2016年   1篇
  2015年   1篇
  2014年   15篇
  2013年   9篇
  2012年   8篇
  2011年   5篇
  2010年   4篇
  2009年   9篇
  2008年   12篇
  2007年   10篇
  2006年   6篇
  2005年   13篇
  2004年   8篇
  2003年   6篇
  2002年   14篇
  2001年   6篇
  2000年   6篇
  1999年   26篇
  1998年   291篇
  1997年   183篇
  1996年   109篇
  1995年   65篇
  1994年   53篇
  1993年   51篇
  1992年   6篇
  1991年   7篇
  1990年   12篇
  1989年   1篇
  1988年   7篇
  1987年   6篇
  1986年   9篇
  1985年   5篇
  1984年   2篇
  1983年   3篇
  1982年   4篇
  1981年   12篇
  1980年   9篇
  1978年   2篇
  1977年   51篇
  1976年   98篇
  1975年   4篇
  1974年   1篇
  1973年   2篇
  1955年   2篇
  1954年   1篇
排序方式: 共有1167条查询结果,搜索用时 312 毫秒
51.
In contrast to cytotoxic agents inducing rapid cell death, biological agents such as hormones, vitamins (e.g., retinoids), cytokines, and antireceptor antibodies act slowly and may alter ratios between cell growth and programmed cell death (apoptosis). We showed previously that anti-interleukin 6 (IL-6) and antitransferrin (Tf) receptor antibodies inhibited in vitro growth and induced death of myeloma cells. Retinoids also inhibit in vitro growth of human cancer cells and decrease IL-6 receptor display and autosecretion by some myeloma cells. Retinoids may also antagonize in vitro growth-promoting effects of iron and transferrin. To develop a novel strategy for treating myeloma, we examined antiproliferative and cytotoxic effects of retinoids in combination with anti-Tf or anti-IL-6 receptor antibodies. Myeloma cell lines were cultured with retinoids with or without anti-growth factor receptor monoclonal antibodies. Both all-trans retinoic acid (ATRA) and 13-cis-retinoic acid showed variable, dose-dependent inhibition of myeloma cell line growth. ATRA also induced significant down-regulation of myeloma IL-6 receptors and inhibited IL-6 autosecretion by myeloma cells. Antiproliferative effects of ATRA were increased by coculture with anti-Tf but not anti-IL-6 receptor antibodies. Colony-forming assays showed that antiproliferative effects of anti-Tf receptor antibodies were largely reversible, but 1 microM ATRA was cytotoxic to myeloma cells. To assess apoptosis, a flow cytometry assay detecting DNA damage was used. Using previously studied cell line models, flow cytometry detected programmed cell death induced by transforming growth factor beta1 in leukemia cells and by anti-growth factor receptor antibody treatment of IL-6-dependent myeloma cells, treatments which caused only modest increases in the percentage of cells undergoing morphological apoptosis and increased internucleosomal DNA degradation. Flow cytometry analysis of ATRA and anti-Tf antibody-treated myeloma cells also showed evidence for apoptosis induced by ATRA, but not with anti-Tf receptor antibodies. These changes were apparent several days before detection of internucleosomal DNA degradation on agarose gels in 8226 cells but were not detected at any time in U266 cells, which underwent cell death but showed no DNA damage using flow cytometry or degradation on agarose gels. Retinoids merit further study as possible maintenance or chemoprevention therapies for clonal plasma cell disorders and for treating paraneoplastic disorders such as Castleman's disease. Flow cytometry rapidly detects apoptosis induced by biological agents and may be useful for in vitro screening of novel biological therapies.  相似文献   
52.
The induction of human immunodeficiency virus (HIV)-specific T-cell responses is widely seen as critical to the development of effective immunity to HIV type 1 (HIV-1). Plasmid DNA and recombinant fowlpox virus (rFPV) vaccines are among the most promising safe HIV-1 vaccine candidates. However, the immunity induced by either vaccine alone may be insufficient to provide durable protection against HIV-1 infection. We evaluated a consecutive immunization strategy involving priming with DNA and boosting with rFPV vaccines encoding common HIV-1 antigens. In mice, this approach induced greater HIV-1-specific immunity than either vector alone and protected mice from challenge with a recombinant vaccinia virus expressing HIV-1 antigens. In macaques, a dramatic boosting effect on DNA vaccine-primed HIV-1-specific helper and cytotoxic T-lymphocyte responses, but a decline in HIV-1 antibody titers, was observed following rFPV immunization. The vaccine regimen protected macaques from an intravenous HIV-1 challenge, with the resistance most likely mediated by T-cell responses. These studies suggest a safe strategy for the enhanced generation of T-cell-mediated protective immunity to HIV-1.  相似文献   
53.
Phospholipase C-gamma1 (PLC-gamma1) mediates signals from various extracellular origins to evoke cellular events such as mitogenesis. Previously, we reported that PLC-gamma1 was highly expressed in colorectal cancer and familial adenomatous polyposis, suggesting that PLC-gamma1 might be oncogenic. In this study, we have established rat 3Y1 fibroblasts that overexpress whole PLC-gamma1 and src homology 2 (SH2)-SH2-SH3 domain of PLC-gamma1. These cells showed a transformed phenotype and were tumorigenic when transplanted into nude mice. These results indicate that overexpression of PLC-gamma1 could transform rat fibroblasts, and the transformation is mediated by SH2-SH2-SH3 domain of PLC-gamma1.  相似文献   
54.
Considering communication and leadership, authors examine the role of the leader as a focus of reception and transmission of information, based on the classification of Mintzberg related to their informative roles, such as the leader acting as monitor, disseminator and spokesman. Contextualizing this approach in the scenery of nursing management, authors study the dimension of nurses-leaders role as an essential element of communication in the systems of organization of nursing care.  相似文献   
55.
56.
57.
58.
59.
We have reported our experience with splenectomy in fifty patients less than fourteen years old. The indications, results, and complications were enumerated. These data were then correlated with the recent literature regarding pediatric splenctomy. Of special note is the problem of immunologic incompetency associated with splenectomy in the patients less than five years old.  相似文献   
60.
A group of 72 gilts, aged between eight and nine months, were treated 20 days each by administration of 5 g Suisynchronpr?mix (Zinc Metallibur/Sui), followed by 24-hour treatment with 750 IU PMS (Prolosanserum). Fifty per cent of the group received 500 IU per animal of HCG (Gonabion) at 11 a.m., on the fourth day after Sui. All animals were artificially inseminated at 3.30 p.m. on the fifth day after Sui. and at 7.30 a.m. on the sixth day after Sui. Laparotomy was performed on 50 per cent of the HCG-treated and untreated animals in the afternoon of the sixth day after Sui. Animals with no recordable ovulation had to undergo another laparotomy in the morning of the seventh day. The above approach resulted in regrouping by four therapeutic categories: 1. HCG with laparotomy, 2. No HCG, 3. HCG with no laparotomy, 4. No HCG and no laparotomy. In the afternoon of the sixth day after Sui (51-56 hours after HCG) ovulation had begun in all 17 measurable animals of the first group, but only in one of 18 animals of the second. The animals were slaughtered between the seventh and twelfth days after Sui, and the following ovulation percentages were established: 100 per cent in the first group, 83.3 per cent in the second, 55.6 per cent in the third, and 72.2 per cent in the fourth. The animals that had been given HCG treatment (Groups 1 and 3) were found to be superior in terms of percentual ovulation to the untreated animals (Groups 2 and 4). However, Group 2 was the only group that had been exposed to the extraordinary stress of two laparotomies, and this should be borne in mind for evaluation. Ovarian cysts (more than 10 mm) began to develop on the eighth day on the laparotomised groups (1 and 2) and on the tenth day on the non-laparotomized groups (3 and 4). Cysts developed in 41.1 per cent of all animals in Group 1, 38.9 per cent in Group 2, 27.8 per cent in Group 3, and 22.2 per cent in Group 4. Therefore, cyst formation is thought to have been stimulated by laparotomy. Ovocyte tests suggested fertilisation of all animals in the first group. The embryonation rates of the second, third, and fourth groups are discussed with reference to the dates of insemination.  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