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   3054篇
  免费   17篇
  国内免费   1篇
电工技术   20篇
化学工业   210篇
金属工艺   13篇
机械仪表   27篇
建筑科学   135篇
矿业工程   1篇
能源动力   50篇
轻工业   130篇
水利工程   14篇
石油天然气   4篇
无线电   138篇
一般工业技术   146篇
冶金工业   2083篇
原子能技术   12篇
自动化技术   89篇
  2022年   9篇
  2021年   9篇
  2019年   13篇
  2018年   11篇
  2017年   10篇
  2016年   9篇
  2015年   12篇
  2014年   20篇
  2013年   50篇
  2012年   26篇
  2011年   41篇
  2010年   27篇
  2009年   26篇
  2008年   30篇
  2007年   29篇
  2006年   35篇
  2005年   25篇
  2004年   32篇
  2003年   25篇
  2002年   25篇
  2001年   28篇
  2000年   26篇
  1999年   74篇
  1998年   629篇
  1997年   364篇
  1996年   286篇
  1995年   132篇
  1994年   131篇
  1993年   145篇
  1992年   42篇
  1991年   53篇
  1990年   39篇
  1989年   46篇
  1988年   42篇
  1987年   36篇
  1986年   32篇
  1985年   33篇
  1984年   18篇
  1983年   32篇
  1982年   22篇
  1981年   29篇
  1980年   45篇
  1979年   19篇
  1978年   16篇
  1977年   65篇
  1976年   126篇
  1975年   12篇
  1973年   16篇
  1969年   6篇
  1968年   6篇
排序方式: 共有3072条查询结果,搜索用时 15 毫秒
31.
32.
The author discusses Christopher Simpson's (1996) article, 'Elisabeth Noelle-Neumann's 'Spiral of Silence' and the Historical Context of Communication Theory.' He questions the relevance of biographical data for the evaluation of scientific theories and methods, and analyzes the rhetorical structure of Simpson's arguments. He concludes that Simpson's claims about the influence of Noelle's biography on her scholarly work are not grounded in evidence.  相似文献   
33.
Based on successful results in animal models, it has been proposed that high-dose myeloablative therapy followed by autologous bone marrow or stem cell transplantation (ABMT/ASCT) may cure autoimmune disease. The coexistence of autoimmune disease and hematologic malignancy provides an opportunity to examine the response of autoimmune disease to ABMT or ASCT. We describe 4 patients with autoimmune disease (3 with psoriasis and 1 with rheumatoid arthritis) and hematologic malignancy. In each patient, the autoimmune disease remitted posttransplantation, but, in 4 patients with long-term followup, it recurred at 8-24 months. The earliest relapse occurred in a patient treated with interferon-alpha. Our experience suggests that a single autograft with unpurged stem cells is unlikely to cure autoimmune disease, but that other strategies building on this approach are worthy of investigation.  相似文献   
34.
35.
36.
We tested the hypothesis that increasing durations of focal ischemia that have been shown to result in enlargement of cortical infarct will be associated with progression of behavioral dysfunction that can be measured by a battery of tests sufficiently sensitive and reproducible to detect a positive effect of pharmacotherapy. Untreated or N-methyl-D-aspartate receptor antagonist (CNS-1102)-treated spontaneously hypertensive rats underwent 45, 60, 90, or 120 min of tandem middle cerebral and common carotid artery occlusion followed by reperfusion. We then evaluated the extent of damage and its recovery for up to 21 days using nine behavioral tests aimed at analyzing strength, coordination, and bilateral asymmetry. Also using a graded bioassay that employs a curve-fitting computer program (ALLFIT) to correlate duration of ischemia with degree of behavioral dysfunction, we calculated the average of maximal behavioral dysfunction and duration of ischemia required to produce half-maximal behavioral dysfunction and compared these values in untreated controls with analogous values obtained from animals treated with CNS-1102. Three behavioral tests, forearm flex, tape (somatosensory neutralization), and foot-fault placing, were each separately and combined able to distinguish between the degrees of damage produced by increasing durations of ischemia. The behavioral abnormalities assessed using the tape test were reversible within a week, whereas those using forearm flex or foot-fault tests persisted for at least 21 days. CNS-1102 significantly reduced behavioral dysfunction measured by all three tests. This analysis of behavioral dysfunction represents a useful experimental model to grade efficacy of therapies aimed at protecting the brain from damage produced by acute stroke and might also be used to assess recovery from preexisting ischemic damage.  相似文献   
37.
38.
In the present study, we examined the effect of the thromboxane/prostaglandin endoperoxide analogue U46619 on proliferation and hypertrophy in cultured rat vascular smooth muscle cells and the roles of protein kinase C and transforming growth factor-beta (TGF-beta) in the mediation of the hypertrophic response to U46619. Since an increase in basic fibroblast growth factor (bFGF) was previously shown to mediate the hypertrophic response to U46619, we also assessed the relationship between bFGF and TGF-beta in the expression of U46619 actions. U46619 increased [35S]methionine incorporation into protein and protein content of vascular smooth muscle cells but had no effect on cell number. A role for TGF-beta was supported by the following observations: (1) exogenous human TGF-beta 1 increased protein synthesis; (2) antibody to TGF-beta blocked both TGF-beta- and U46619-induced increases in protein content; (3) U46619 increased active and total TGF-beta bioactivities; and (4) the actions of U46619 on protein content and TGF-beta bioactivity were blocked by the thromboxane/prostaglandin endoperoxide receptor antagonist SQ 29,548. Previous observations had demonstrated a role for bFGF in the expression of U46619 actions on protein synthesis. Results of the present study suggest that TGF-beta and bFGF interact in mediating the protein synthetic response to U46619. First, the concentration of exogenous TGF-beta (10 pmol/L) alone required to produce a protein synthetic response equivalent to that induced by U46619 was much higher than the concentration of endogenous active TGF-beta that accumulated in the media in response to U46619 (0.7 pmol/L). Second, bFGF (20 ng/mL) increased total TGF-beta bioactivity and stimulated protein synthesis. The hyper-trophic response to bFGF was blocked by anti-TGF-beta. The ability of U46619 and bFGF to increase protein synthesis and protein content in vascular smooth muscle cells was associated with TGF-beta-induced suppression of proliferation, as evidenced by the ability of antibody to TGF-beta to enhance U46619- and bFGF-induced increases in [3H]thymidine incorporation into DNA. Results of the present study also supported a role for protein kinase C in the expression of U46619 and bFGF actions. U46619 increased protein kinase C activity in the particulate fraction of vascular smooth muscle cells. Moreover, the protein kinase C inhibitors GF109203X and staurosporine blocked U46619- and bFGF-induced increases in protein synthesis as well as active and total TGF-beta bioactivities. By contrast, the protein kinase C inhibitors did not prevent the increases in protein synthesis induced by exogenous TGF-beta. The results demonstrate that thromboxane/prostaglandin endoperoxide signals increased TGF-beta bioactivity via protein kinase C. Increases in both bFGF and TGF-beta are required for an optimal hypertrophic response to U46619. The hypertrophic response to TGF-beta occurs through a protein kinase C-independent pathway.  相似文献   
39.
40.
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