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   1231篇
  免费   24篇
  国内免费   2篇
电工技术   98篇
综合类   1篇
化学工业   262篇
金属工艺   33篇
机械仪表   51篇
建筑科学   18篇
矿业工程   1篇
能源动力   32篇
轻工业   83篇
水利工程   5篇
石油天然气   2篇
无线电   82篇
一般工业技术   225篇
冶金工业   235篇
原子能技术   36篇
自动化技术   93篇
  2023年   6篇
  2022年   17篇
  2021年   28篇
  2020年   9篇
  2019年   14篇
  2018年   12篇
  2017年   12篇
  2016年   22篇
  2015年   27篇
  2014年   37篇
  2013年   52篇
  2012年   38篇
  2011年   57篇
  2010年   37篇
  2009年   44篇
  2008年   49篇
  2007年   33篇
  2006年   37篇
  2005年   35篇
  2004年   30篇
  2003年   48篇
  2002年   41篇
  2001年   40篇
  2000年   23篇
  1999年   30篇
  1998年   87篇
  1997年   49篇
  1996年   48篇
  1995年   29篇
  1994年   28篇
  1993年   45篇
  1992年   13篇
  1991年   10篇
  1990年   15篇
  1989年   17篇
  1988年   9篇
  1987年   12篇
  1986年   6篇
  1985年   10篇
  1984年   16篇
  1983年   5篇
  1982年   10篇
  1981年   7篇
  1980年   8篇
  1979年   7篇
  1978年   8篇
  1977年   7篇
  1976年   10篇
  1974年   6篇
  1973年   4篇
排序方式: 共有1257条查询结果,搜索用时 15 毫秒
901.
This paper describes an improved stroke matching method for the recognition of handprinted Kanji characters. Using the stroke feature and two additional global features, a recognition rate of over 90% has been obtained for about 1000 Kanji characters.  相似文献   
902.
Tyrosine hydroxylase (TH)-like immunoreactive neurons, fibers, and terminals in the hypothalamic arcuate nucleus and median eminence of young (8 weeks old) and aged (24 months old) rats were investigated at light and electron microscopic levels by means of the peroxidase anti-peroxidase (PAP) method. In the arcuate nucleus, TH-like immunoreactive neuronal perikarya of young animals contained well-developed cell organelles such as rough-surfaced endoplasmic reticulum (rER), mitochondria, Golgi apparatus, polysomes, as well as dense granules. Immunoreactive neuronal elements appeared as both presynaptic and postsynaptic elements. In aged rats, TH-like immunoreactive neuronal perikarya as well as non-immunoreactive ones were found to include many lysosomes or inclusions, and many neuronal elements with degradative changes were observed. In the external layer of the median eminence of young animals, many immunoreactive nerve endings were found around the pericapillary spaces of portal vessels and often terminated adjacent to the basement membranes of the pericapillary spaces. Immunoreactive fibers having close contact with non-immunoreactive fibers were also observed. In aged animals, degradative changes such as axons with swollen and watery appearance and myelin figures were observed in the neuronal elements, although many immunoreactive nerve endings were seen around the pericapillary spaces.  相似文献   
903.
Today, computer graphics technology has advanced remarkably so that it can handle quite complicated picture information. As a result, images for broadcasting, advertising and textiles that used to be made by hand and were very timeconsuming to put out can now be completed in a very short time.  相似文献   
904.
905.
906.
Leukemic cells from patients with adult T-cell leukemia (ATL) can produce a calcium-regulating protein, parathyroid hormone-related protein (PTHrP). Moreover, it has been reported that ATL cells produce some cytokines besides PTHrP and that these cells respond to the T-cell growth factors, interleukin-2 (IL-2) and interleukin-4 (IL-4). To elucidate whether PTHrP produced by ATL cells is regulated by IL-2 or IL-4, we investigated the in vitro effects of IL-2 and IL-4 on the release of PTHrP. IL-2 increased the release of PTHrP into the conditioned medium from leukemic cells in some, but not all, ATL patients; however, IL-4 did not affect the PTHrP release. PTHrP messenger RNA (mRNA) levels were increased in ATL cells cultured in the presence of IL-2. These data suggest that IL-2 plays a role in the regulation of hypercalcemia by enhancing the production of PTHrP in ATL patients.  相似文献   
907.
We investigated the effect of orally administered trimebutine maleate on gastric and gallbladder emptying and on the release of gut peptide, pancreatic polypeptide (PP), and gastrin in humans for 120 min after ingestion of a solid meal. Gastric emptying was measured by a radionuclide technique. Gallbladder emptying was estimated by real-time ultrasonography. The oral administration of 200 mg of trimebutine maleate significantly shortened the lag time in starting gastric emptying (P < 0.05). Considering gallbladder emptying, trimebutine significantly inhibited the fasting emptying induced by neural reflex. Postprandially, there was a tendency toward an accelerated gallbladder emptying in the early phase. Neither the maximal percentage of gallbladder emptying nor the time of peak gallbladder emptying were affected. Trimebutine significantly blunted the post-prandial PP response in the cephalic and gastric phases, reflecting a vagal-cholinergic activity (P < 0.05). The PP response in the intestinal phase was also blunted. Gastrin release was significantly augmented only during the period of fasting after drug administration (P < 0.05). The major effect of trimebutine maleate appears to be a shortening of the lag time at the start of gastric emptying probably via its anticholinergic activity.  相似文献   
908.
The objective of this study was to evaluate the combined effects of mineral fibres and cigarette smoke on the production of tumour necrosis factor (TNF) by alveolar macrophages. Rats were exposed to cigarette smoke in vivo, and production of TNF by alveolar macrophages was measured in the presence of mineral fibres in vitro. For smoke exposure, rats were divided into two groups. Five were exposed to a daily concentration of 10 mg/m3 of cigarette smoke for an eight hour period, and five rats (controls) were not exposed to smoke. Bronchoalveolar lavage was performed after exposure to smoke and the recovered alveolar macrophages were incubated with either chrysotile or ceramic fibres on a microplate for 24 hours. Activity of TNF in the supernatant was determined by the L-929 fibroblast cell bioassay. When alveolar macrophages were not stimulated by mineral fibres, production of TNF by rats exposed to smoke and unexposed rats was essentially the same. When alveolar macrophages were stimulated in vitro by chrysotile or ceramic fibres, production of TNF by alveolar macrophages from rats exposed to smoke was higher than that by alveolar macrophages from unexposed rats. The findings suggest that cigarette smoke and mineral fibres have a synergistic effect on TNF production by alveolar macrophages.  相似文献   
909.
910.
An acidic polysaccharide (TAP) was isolated from a hot-water extract of the fruiting bodies of Tremella aurantia. It showed remarkable hypoglycemic activity in normal mice and two diabetic mouse models, streptozotocin-induced diabetes and genetic diabetes, following intraperitoneal administration. Continuous oral administration of TAP solution (0.5g/l) for a long period was found to be also effective in hyperglycemia in glucose-loaded mice and no harmful physical effects were found. TAP had an [alpha]D -7 degrees in water, and its molecular weight was estimated to be about 1500000. TAP is composed of mannose, xylose, glucuronic acid and glucose (molar ratio, 4:2:1:0.3), and it contains 2.2% of O-acetyl groups.  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