全文获取类型
收费全文 | 3666篇 |
免费 | 5篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 9篇 |
综合类 | 2篇 |
化学工业 | 42篇 |
金属工艺 | 9篇 |
机械仪表 | 12篇 |
建筑科学 | 12篇 |
能源动力 | 16篇 |
轻工业 | 19篇 |
石油天然气 | 2篇 |
无线电 | 40篇 |
一般工业技术 | 34篇 |
冶金工业 | 3469篇 |
原子能技术 | 1篇 |
自动化技术 | 10篇 |
出版年
2021年 | 3篇 |
2019年 | 2篇 |
2018年 | 5篇 |
2017年 | 3篇 |
2015年 | 2篇 |
2014年 | 2篇 |
2013年 | 9篇 |
2012年 | 5篇 |
2011年 | 19篇 |
2010年 | 9篇 |
2009年 | 8篇 |
2008年 | 7篇 |
2007年 | 7篇 |
2006年 | 5篇 |
2005年 | 13篇 |
2004年 | 8篇 |
2003年 | 19篇 |
2002年 | 11篇 |
2001年 | 7篇 |
2000年 | 5篇 |
1999年 | 110篇 |
1998年 | 1082篇 |
1997年 | 568篇 |
1996年 | 428篇 |
1995年 | 225篇 |
1994年 | 214篇 |
1993年 | 218篇 |
1992年 | 24篇 |
1991年 | 36篇 |
1990年 | 48篇 |
1989年 | 49篇 |
1988年 | 51篇 |
1987年 | 50篇 |
1986年 | 45篇 |
1985年 | 28篇 |
1984年 | 2篇 |
1983年 | 8篇 |
1982年 | 17篇 |
1981年 | 18篇 |
1980年 | 31篇 |
1978年 | 6篇 |
1977年 | 77篇 |
1976年 | 175篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1955年 | 3篇 |
排序方式: 共有3677条查询结果,搜索用时 765 毫秒
101.
M Labuda JM Austyn E Zuffova O Kozuch N Fuchsberger J Lysy PA Nuttall 《Canadian Metallurgical Quarterly》1996,219(2):357-366
Arboviruses are transmitted to vertebrates by the "bite" of infected arthropods. Events at the site of virus deposition are largely unknown despite increasing evidence that blood-sucking arthropods immunomodulate their skin site of feeding. This question is particularly relevant for ixodid ticks that feed for several days. To examine events under conditions mimicking tick-borne encephalitis (TBE) virus transmission in nature (i.e., infected and uninfected Ixodes ricinus ticks feeding on the same animal), infected adult and uninfected nymphal ticks were placed in one retaining chamber (skin site A) and uninfected nymphs were placed within a second chamber posteriorly (skin site B) on two natural host species, yellow-necked field mice (Apodemus flavicollis) and bank voles (Clethrionomys glareolus). Virus transmission from infected to uninfected cofeeding ticks was correlated with infection in the skin site of tick feeding. Furthermore, virus was recruited preferentially to the site in which ticks were feeding compared with uninfested skin sites. Viremia did not correspond with a generalized infection of the skin; virus was not detected in an uninfested skin site (C) of 12/13 natural hosts that had viremia levels > or = 2.0 log10 ic mouse LD50/0.02 ml blood. To characterize infected cells, laboratory mouse strains were infested with infected ticks and then explants were removed from selected skin sites and floated on culture medium. Numerous leukocytes were found to migrate from the skin explants of tick feeding sites. Two-color immunocytochemistry revealed viral antigen in both migratory Langerhans cells and neutrophils; in addition, the migratory monocyte/macrophages were shown to produce infectious virus. The results indicate that the local skin site of tick feeding is an important focus of viral replication early after TBE virus transmission by ticks. Cellular infiltration of tick feeding sites, and the migration of cells from such sites, may provide a vehicle for transmission between infected and uninfected cofeeding ticks that is independent of a patent viremia. The data support the hypothesis that viremia is a product, rather than a prerequisite, of tick-borne virus transmission. 相似文献
102.
Kuya Takami Tomonari Furukawa Makoto Kumon Daisuke Kimoto Gamini Dissanayake 《Autonomous Robots》2016,40(2):343-359
This paper presents a nonvisible field-of-view (NFOV) target estimation approach that incorporates optical and acoustic sensors. An optical sensor can accurately localize a target in its field-of-view whereas the acoustic sensor could estimate the target location over a much larger space, but only with limited accuracy. A recursive Bayesian estimation framework where observations of the optical and acoustic sensors are probabilistically treated and fused is proposed in this paper. A technique to construct the observation likelihood when two microphones are used as the acoustic sensor is also described. The proposed technique derives and stores the interaural level difference of observations from the two microphones for different target positions in advance and constructs the likelihood through correlation. A parametric study of the proposed acoustic sensing technique in a controlled test environment, and experiments with an NFOV target in an actual indoor environment are presented to demonstrate the capability of the proposed technique. 相似文献
103.
BR Blazar PA Taylor DC Snover JA Bluestone DA Vallera 《Canadian Metallurgical Quarterly》1993,150(1):265-277
We have investigated the in vivo administration of nonmitogenic anti-CD3F(ab')2 fragments for the prevention of lethal graft-vs-host disease (GVHD) in irradiated recipients of fully allogeneic bone marrow cells plus splenocyte (BMS) inocula. Recipients of anti-CD3F(ab')2 fragments administered for 1 mo post-bone marrow transplantation (BMT) had 100% survival without clinical or histopathological evidence of GVHD. Controls given saline injections succumbed by 39 days post-BMT. Similar results were obtained in groups of recipient mice given BMS in which T cells were depleted by in vitro anti-Thy-1.2 plus C' treatment. Further studies were undertaken to define mechanistic differences in the two approaches. Using Ly-5 congenic sources of donor bone marrow and spleen, we determined that anti-CD3F(ab')2 fragments induced TCR modulation and T cell depletion. Mature splenic-derived CD4+ cells were depleted to a greater extent than CD8+ cells. Early post-BMT, recipients receiving injections with control saline had the highest number of CD4+ and CD8+ cells (which may cause GVHD) followed by recipients of anti-CD3F(ab')2 fragments, with the fewest CD8+ cells observed in the anti-Thy-1.2 + C' treated group. CD3+CD4-CD8- cells (which may suppress GVHD generation) were present in higher numbers early post-BMT in recipients given anti-CD3F(ab')2 fragments as compared to recipients given anti-Thy-1.2 + C'-treated BMS. In long term survivors, a mononuclear T cell containing infiltrate without evidence of destruction was observed in sites of GVHD (lung and liver), consistent with a "Quilty" effect, which was not observed in either of the other two groups. Although survivors were tolerant of donor skin grafts and rejected third party grafts, recipients given anti-CD3F(ab')2 fragments but not anti-Thy-1.2 + C'-treated BMS had vigorous anti-host proliferative responses. These results demonstrate that although in vitro anti-Thy-1.2 + C' treatment of BMS (which is highly depletionary) and in vivo administration of anti-CD3F(ab')2 fragments (which is modulatory and less depletionary) are both effective strategies for GVHD, the cellular events involved in achieving GVHD prevention are indeed different. 相似文献
104.
105.
In a study of plasma somatomedin activity in childhood scoliosis a group of five patients with congenital scoliosis was found to have significantly lower plasma somatomedin levels compared with a group of 20 normal children. A group of 52 patients with "idiopathic" scoliosis had normal plasma somatomedin levels. There is no apparent difference in the plasma somatomedin activity between the sexes, and no change in plasma somatomedin activity with chronologic age in these children, suggesting that normal adult somatomedin levels have been reached. 相似文献
106.
Side effects of orally administered bismuthic salts have been known for many years. Many systems are involved, including the digestive and urinary. The authors discuss a recently discovered effect on the central nervous system, termed "bismuth encephalopathy". In the light of the medical literature reviewed, two original aspects are stressed: the clinical symptoms are stereotyped and completely reversible, and the distribution of the disease is almost epidemic, being limited in time and space. The prodromes include confusion, asthenia, slowing of mental functions and disturbance of gait. The clinical picture is dominated by four major symptoms: confusion (again), ataxia, dysarthria and, above all, myoclonic jerks. In conclusion, various pathogenetic hypotheses are considered. The purpose of this study is to enable the general practitioner to detect the development of this condition early in treatment with oral bismuthic salts. Withdrawal of the medication always results in normalization of the patient's condition. 相似文献
107.
A comparison of self-report vs. observer rating of depressed mood in a heterogenous inpatient population revealed wide variations in concordance among diagnostic groups. Patients diagnosed as having Affective Psychosis and "Other' illnesses showed the highest correlation between four self-report scales and an observer rating scale. Patients with a diagnosis of depressive Neurosis showed only modest correlation, while Schizophrenics revealed no significant correlation, on these instruments, suggesting inconsistent communication of affect from Schizophrenic patients to observers. In contrast, when self-report scales were intercorrelated, patients in all four diagnostic categories showed highly significant correlations, indicating that they were consistently reporting their affective state on these instruments. The implications of these findings for future research as well as for practical clinical management are discussed. 相似文献
108.
109.
刘淳 《腐蚀科学与防护技术》1994,6(2):115-122
局部腐蚀,包括点腐蚀、应力腐蚀开裂和腐蚀疲劳是导致电厂发电装置损伤的重要原因,它们诱发50%以上的意外停机事故。迄今,腐蚀破坏的预测一直沿用经验和统计的方法,但是,由于已证实该方法的适用性和其结果的准确性欠佳,故不宜作为例行检修规程的基础。本文提出了预测局部腐蚀损伤的决定论方法,并使用这个方法说明点腐蚀如何引发低压蒸汽轮机涡轮盘Wilson线下游部位的应力腐蚀开裂(SCC),我们的计算表明SCC的萌发与扩展对蒸汽小氧含量、冷凝液膜的环境和涡轮盘所承受的应力这三个因素敏感。 相似文献
110.
Pai-shan PA Digital Content Design Graduate School of Toy Game Design National Taipei University of Education Taipei City China 《中国有色金属学会会刊》2011,(Z1)
Color filters are produced using semiconductor production techniques although problems with low yield remain to be addressed. This study presents a new means of selective removal using excimer irradiation, chemical etching, or electrochemical machining on the fifth generation TFT LCDs. The selective removal of microstructure layers from the color filter surface of an optoelectronic flat panel display, as well as complete removal of the ITO thin-films, RGB layer, or resin black matrix (BM) layer from the sub... 相似文献