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   1431篇
  免费   1篇
  国内免费   1篇
化学工业   7篇
金属工艺   1篇
轻工业   1篇
无线电   1篇
一般工业技术   2篇
冶金工业   1418篇
原子能技术   1篇
自动化技术   2篇
  2023年   1篇
  2018年   1篇
  2006年   3篇
  2004年   1篇
  2003年   4篇
  2002年   1篇
  2000年   1篇
  1999年   42篇
  1998年   472篇
  1997年   261篇
  1996年   170篇
  1995年   87篇
  1994年   73篇
  1993年   88篇
  1992年   9篇
  1991年   15篇
  1990年   12篇
  1989年   21篇
  1988年   9篇
  1987年   9篇
  1986年   10篇
  1985年   8篇
  1984年   1篇
  1983年   1篇
  1982年   4篇
  1981年   8篇
  1980年   8篇
  1979年   1篇
  1978年   4篇
  1977年   23篇
  1976年   80篇
  1975年   4篇
  1955年   1篇
排序方式: 共有1433条查询结果,搜索用时 15 毫秒
101.
102.
Prevalence and evaluative opinions about smoking among 527 adolescents and young adults were quantified in order to assess the efficacy of Thailand's mass media antismoking campaign. The reactions of subjects to the smoking of (a) father, (b) mother, (c) boys, (d) girls, and (e) myself were obtained using a semantic differential measure. Virtually all subjects had seen antismoking adds on television and the overall perception of smoking was highly disapproving with significant gender and age differences being present. Older males were more likely to smoke and had less critical attitudes about this harmful behavior than their younger peers and female participants. Reactions to female smoking (mother and girls) were more derogatory than to the same behavior among males (father and boys). Results suggest that smoking will continue as a serious problem among Thai males and demonstrate the addictive nature of cigarette smoking which persists in spite of the increasingly negative evaluative attitudes of users.  相似文献   
103.
Leukotrienes constitute a class of potent biological mediators of inflammation and anaphylaxis (for reviews see refs 1 and 2). Their biosynthesis derives from 5-lipoxygenase-catalysed oxygenation of arachidonic acid in granulocytes, macrophages and mast cells. To examine the physiological importance of leukotrienes, we have disrupted the 5-lipoxygenase gene by homologous recombination in embryonic stem cells. 5-Lipoxygenase-deficient (5LX-/-) mice develop normally and are healthy. They show a selective opposition to certain inflammatory insults. Although there is no difference in their reaction to endotoxin shock, the 5LX-/- animals resist the lethal effects of shock induced by platelet-activating factor. Reaction to ear inflammation induced by phorbol ester is normal, whereas inflammation induced by arachidonic acid is markedly reduced. Contrasts were also found in two models of leukocyte chemotaxis in vivo. The phenotype of 5LX-/- mice under injurious insult identifies the role for leukotrienes in the pathophysiology of select inflammatory states.  相似文献   
104.
The objective of this study was to investigate whether reduction in hypertriglyceridaemia is associated with a slower rate of progression of microalbuminuria in patients with non-insulin-dependent diabetes mellitus (NIDDM). Fifteen normotensive NIDDM patients with hypertriglyceridaemia (> 2.5 mmol L-1) and microalbuminuria were randomly selected to receive either placebo (eight patients) or gemfibrozil 600 mg b.i.d. (seven patients). Progression of microalbuminuria was assessed during a 12-month follow-up period with measurements, consisting of blood tests and triplicate 24-h urine collections, at 1, 3, 6, 9 and 12 months. All but one patient in the treatment group showed a favourable response (> or = 20% reduction) of hypertriglyceridaemia to gemfibrozil. One patient in the placebo group showed a spontaneous reduction in triglyceride levels. Progression of microalbuminuria was lower, although not statistically significantly so, in the treatment group (36%) than in the placebo group (65%). In the group with > or = 20% reduction in triglyceride levels, progression of MA was significantly lower than in the group with stable or increasing triglyceride levels (+1%, range -56% to +49% vs. +97%, range -35% to +202% respectively) (P = 0.03). Continued follow-up data of patients switching from placebo to gemfibrozil after the trial further support the role of serum triglyceride reduction in stabilizing albumin excretion. In conclusion, the results indicate that, in microalbuminuric NIDDM patients, effective treatment of dyslipidaemia could be associated with stabilization of urinary albumin excretion.  相似文献   
105.
The regulation by neuropeptide Y of alpha2-adrenoceptors in the nucleus tractus solitarii was evaluated in the adult normotensive Wistar Kyoto rat and the adult spontaneously hypertensive rat. The microinjection of a submaximal dose of l-noradrenaline (800 pmol in 50 nl) alone into the nucleus tractus solitarii produced a significant reduction in the mean arterial blood pressure in either strain. The threshold dose (1 pmol in 50 nl) of neuropeptide Y(1-36) for the vasodepressor response in the Wistar Kyoto rat was five times higher than that (0.2 pmol in 50 nl) in the spontaneously hypertensive rat. Furthermore, neuropeptide Y(1-36) at 0.2 pmol in 50 nl could significantly counteract the vasodepressor response to l-noradrenaline (800 pmol in 50 nl) in the spontaneously hypertensive rat, but not in the Wistar Kyoto rat, in which 1 pmol in 50 nl of neuropeptide Y(1-36) must be employed to counteract the vasodepressor response to l-noradrenaline (800 pmol in 50 nl), although the vasodepressor responses are of a similar magnitude. The in situ hybridization and quantitative receptor autoradiographical experiments showed that the alpha2A-adrenoceptor messenger RNA levels and the B(max) value of the alpha2-adrenoceptor agonist [3H]p-aminoclonidine binding sites measured in the nucleus tractus solitarii of the spontaneously hypertensive rat were substantially lower than those in the Wistar Kyoto rat. The quantitative receptor autoradiographical results were consistent with the cardiovascular results and showed that in the spontaneously hypertensive rat, neuropeptide Y(1-36) at 1 nM led to a significant increase in the K(d) value of [3H]p-aminoclonidine binding sites. In the Wistar Kyoto rat, neuropeptide Y(1-36) produced this effect only at 10 nM. The present study provides evidence for an increase of the potency of neuropeptide Y(1-36) to antagonistically modulate alpha2-adrenoceptors in the nucleus tractus solitarii of the spontaneously hypertensive rat. This enhanced antagonistic action may partly be related to a reduction in the number of alpha2A-adrenoceptors in the nucleus tractus solitarii of the spontaneously hypertensive rat, since a decrease has been observed in the alpha2A-adrenoceptor messenger RNA levels and the alpha2-adrenoceptor binding sites in the spontaneously hypertensive rat. This increased potency of neuropeptide Y(1-36) to antagonize alpha2-adrenoceptor function in the nucleus tractus solitarii of the spontaneously hypertensive rat may contribute to the development of high blood pressure in this hypertensive strain.  相似文献   
106.
Immunohistochemical analyses were used to investigate the distribution of lymphocytes and macrophages in routine human temporal bone sections obtained from a subject with acute suppurative otitis media. Primary antibodies specific for human CD3 and CD43 (T-lymphocytes), CD20 (B-lymphocytes), CD45 (leukocyte common antigen), and CD68 (macrophages) were used. As a pretreatment, the sections were soaked in antigen retrieval solution (saturated sodium hydroxide-methanol solution in methanol at a ratio of 1:3). A second antigen retrieval procedure (microwave treatment in 1% zinc sulfate) was also employed for identifying CD3-positive cells. Then the avidin-biotin-peroxidase complex technique was performed. Positive reactions to all antibodies but anti-CD68 were observed in the mucosa of the eustachian tube, tympanic cavity, and mastoid air cells. Particularly, cells positive to anti-CD3 or anti-CD43 were making a diffuse invasion upon the lamina propria. CD68-positive cells were scattered only in the effusion of mastoid air cells. These results suggest that the retrospective immunohistochemical study of archival temporal bone sections is a promising approach to investigate the pathogenesis of otitis media.  相似文献   
107.
Interleukin-6 (IL-6) has been reported to have pro- and anti-inflammatory effects. It has also been shown to cause mesangial cell proliferation in vitro and has been suggested as a mediator of injury in proliferative nephritis. We have assessed the effects of continuous infusion of human recombinant (hr) IL-6, by osmotic minipump, on the degree of glomerular injury, and on glomerular and interstitial cell proliferation, in the accelerated autologous phase of nephrotoxic nephritis. Two groups of rats were pre-immunized with 1 mg of normal rabbit IgG in Freund's complete adjuvant. One week later, nephritis was induced by an intravenous injection of 1 ml of rabbit nephrotoxic serum. One day before the induction of nephritis, group 1 (N = 9) was subcutaneously implanted with osmotic minipumps filled with 50 micrograms (200 microliters) of IL-6 (equivalent to a dose of 6 micrograms/day), while in group 2 (N = 11) the minipumps were filled with 200 microliters of normal saline. In group 3 (N = 6) normal rats were infused with 50 micrograms of IL-6 alone. The rats were killed seven days after implantation of minipumps. The administered hrIL-6 was detectable in the circulation within the pathophysiological range, and induced a hepatic acute phase response, as assessed by alpha 2-macroglobulin levels. Continuous treatment with IL-6 resulted in a significant reduction in albuminuria (from 195 +/- 37 mg/20 hr to 60 +/- 15 mg/20 hr on day 1, and from 494 +/- 52 mg/20 hr to 238 +/- 30 mg/20 hr on day 7, P < 0.002) and in the prevalence of glomerular capillary thrombosis (from 19 +/- 3% to 5 +/- 1%, P < 0.002). There was also a reduction in macrophage infiltration (ED1 + ve cells from 524 +/- 34 to 466 +/- 14 per 50 glomeruli, P < 0.02) and activation (ED3 + ve cells from 106 +/- 13 to 42 +/- 5 per 50 glomeruli, P < 0.002). Immunohistology showed fewer interstitial Ia + ve cells (OX3 and OX4) in the IL-6 treated group. Similar results were obtained in a second set of experiments in which the IL-6 treatment was extended until day 14. Kidney sections taken from nephritic rats infused with IL-6 showed no increase in glomerular or interstitial cell proliferation when stained with antibodies to proliferating cell nuclear antigen. There was no difference in the deposition of rabbit IgG or rat IgG along the glomerular basement membrane (GBM), and the titer of rat anti-rabbit IgG was similar in the IL-6 and control treated rats. Infusion of IL-6 alone in normal rats had no functional or pathological effects. In conclusion, these results show that IL-6 has powerful anti-inflammatory effects in a rat model of anti-GBM nephritis, and does not induce mesangial cell proliferation in vivo.  相似文献   
108.
Regional brain activity associated with intentional and incidental memory retrieval was studied with PET. Previously studied and new words were presented in either an intentional or an incidental memory task. Type of task was crossed with an encoding manipulation ('deep' vs 'shallow') which varied the probability that studied items would be remembered. In both tasks, deeply encoded items were associated with greater activation in the left hippocampus than were items that had received shallow encoding, suggesting that the involvement of the hippocampus in memory retrieval is independent of whether remembering is intentional or incidental. Right prefrontal and bilateral parietal cortex were more activated during the international task than during the incidental task, irrespective of encoding condition. Thus, these regions play a more extensive role in memory retrieval when remembering is intentional.  相似文献   
109.
110.
In 1996, national guidelines for the care and treatment of patients with diabetes mellitus were drawn up by specialists, in collaboration with representatives of the patient organisation, diabetes nurses, the professional associations of various medical specialties and central authorities. The national programme is divides into three parts: summarised information for decision-makers, clinical guidelines and complete information for patients. The guidelines are designed to provide a basis for treatment programmes at the local level. Among other things, the national guidelines stress the importance of the diabetes nurse both in primary and tertiary care, and emphasise the need of regional centers providing access to information and education and promoting the development of treatment. Another important aspect is fostering the influence of patient organisations at the local level, in order for the guidelines to have an impact on the quality of care for the individual patient.  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