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   853篇
  免费   1篇
电工技术   1篇
化学工业   6篇
机械仪表   1篇
轻工业   2篇
无线电   2篇
一般工业技术   6篇
冶金工业   836篇
  2023年   1篇
  2022年   1篇
  2021年   2篇
  2012年   2篇
  2008年   1篇
  2006年   1篇
  2005年   1篇
  2004年   2篇
  2003年   2篇
  2000年   1篇
  1999年   18篇
  1998年   274篇
  1997年   147篇
  1996年   98篇
  1995年   51篇
  1994年   43篇
  1993年   44篇
  1992年   7篇
  1991年   10篇
  1990年   4篇
  1989年   9篇
  1988年   10篇
  1987年   10篇
  1986年   13篇
  1985年   11篇
  1983年   2篇
  1982年   3篇
  1981年   2篇
  1980年   12篇
  1978年   1篇
  1977年   19篇
  1976年   52篇
排序方式: 共有854条查询结果,搜索用时 422 毫秒
21.
We conducted a review to investigate the prevalence of human immunodeficiency virus (HIV), or acquired immunodeficiency syndrome (AIDS), in patients with herpes zoster ophthalmicus, as well as the incidence of acute retinal necrosis after herpes zoster ophthalmicus. All charts of patients seen at our institution between 1987 and 1992 with a primary diagnosis of herpes zoster ophthalmicus were reviewed. Of 112 patients with herpes zoster ophthalmicus, 29 (26%) had HIV or AIDS. All these patients were younger than 50 years at the time of diagnosis. Five of 29 (17%) immunocompromised patients had acute retinal necrosis after herpes zoster ophthalmicus. No acute retinal necrosis was identified in the nonimmunocompromised patients after herpes zoster ophthalmicus. We recommend that all patients younger than 50 years who have herpes zoster ophthalmicus at initial examination be tested for HIV. Additionally, HIV-infected patients should be monitored closely after herpes zoster ophthalmicus for development of acute retinal necrosis. Long-term oral prophylactic as well as initial high-dose intravenous acyclovir may be appropriate in HIV-infected individuals with herpes zoster.  相似文献   
22.
23.
Delta opioid peptide [D-Ala2,D-leu5]enkephalin (DADLE) can prolong organ preservation and increases myocardial tolerance to ischemia. Our study examined the protective property of DADLE against methamphetamine- (METH) induced dopaminergic terminal damage in the central nervous system. Because the neurotoxicity of METH involves reactive oxygen species, we also examined if DADLE might be an antioxidative agent in vitro. DADLE at 2 and 4 mg/kg (i.p.), given 30 min before each METH administration (5 or 10 mg/kg, i.p., four injections in a day at 2-hr intervals), dose-dependently blocked the METH-induced long-term dopamine transporter loss. The opioid antagonist naltrexone blocked this action of DADLE in both aspects of striata but tends not to affect the effects of DADLE in the nucleus accumbens. DADLE did not alter changes in body temperature induced by METH. The reduction of striatal dopaminergic content and tyrosine hydroxylase activity caused by METH, however, were not blocked by DADLE. In vitro, DADLE was approximately equipotent to glutathione in inhibiting both superoxide anion formation induced by xanthine oxidase and hydroxyl radical formation evoked by ferrous/citrate complex. DADLE was only slightly less potent than glutathione in inhibiting the iron/ascorbate-induced brain lipid peroxidation. These results suggest that DADLE can protect the terminal membranes of dopaminergic neurons against METH-induced insult but not the loss of dopaminergic content and tyrosine hydroxylase activity and that this action of DADLE might involve opioid receptors as well as the sequestration of free radical.  相似文献   
24.
Rac, a member of the rho family of GTPases, when activated transmits signals leading to actin-based membrane ruffling in fibroblasts. Compared with wild-type fibroblasts, gelsolin null (Gsn-) dermal fibroblasts have a markedly reduced ruffling response to serum or EGF stimulation, which signal through rac. Bradykinin-induced filopodial formation, attributable to activation of cdc42, is similar in both cell types. Wild-type fibroblasts exhibit typical lamellipodial extension during translational locomotion, whereas Gsn- cells move 50% slower using structures resembling filopodia. Multiple Gsn- tissues as well as Gsn- fibroblasts overexpress rac, but not cdc42 or rho, 5-fold. Re-expression of gelsolin in Gsn- fibroblasts by stable transfection or adenovirus reverts the ruffling response, translational motility and rac expression to normal. Rac migrates to the cell membrane following EGF stimulation in both cell types. Gelsolin is an essential effector of rac-mediated actin dynamics, acting downstream of rac recruitment to the membrane.  相似文献   
25.
26.
In the tissues of the herpes-infected eye of a rabbit the content of adenosine triphosphoric acid (ATP), glucose and pyroracemic acid decreases and the level of lactic acid rises, i.e. anaerobic glycolysis prevails over the aerobic decomposition of glucose. A sharp decrease in the amount of ATP in the cornea and the iris in herpetic keratitis is due to the increased consumption of ATP for the synthesis of DNA and polypeptides of herpes simplex virus, as well as to disturbances in the oxidation transformations of glucose linked with the increased proportion of anaerobic glycolysis.  相似文献   
27.
Sensory integration (SI) therapy is a controversial--though popular--treatment for the remediation of motor and academic problems. It has been applied primarily to children with learning disabilities, under the assumption that such children (or at least a subgroup of them) have problems in sensory integration to which some or all of their learning difficulties can be ascribed. The present article critically examines the related issues of whether children with learning disabilities differentially exhibit concomitant problems in sensory integration, and whether such children are helped in any way by means specific to SI therapy. An overview of theoretical contentions and empirical findings pertaining to the first issue is presented, followed by a detailed review of recent studies in the SI therapy research literature, in an effort to resolve the second issue. Results of this critique raise serious doubts as to the validity or utility of SI therapy as an appropriate, indicated treatment for the clinical population in question--and, by extension, for any other groups diagnosed as having "sensory integrative dysfunction." It is concluded that the current fund of research findings may well be sufficient to declare SI therapy not merely an unproven, but a demonstrably ineffective, primary or adjunctive remedial treatment for learning disabilities and other disorders.  相似文献   
28.
Peptide toxins have proved to be useful agents, both in discriminating between different components of native calcium channel currents and in the molecular isolation and designation of their cloned channel counterparts. Here, we describe the isolation and characterization of the biochemical and physiological properties of a novel 74-amino acid peptide toxin (DW13.3) extracted from the venom of the spider Filistata hibernalis. The subtype specificity of DW13.3 was investigated using calcium channel currents recorded from two separate expression systems and several different cultured mammalian cell preparations. Overall, DW13.3 potently blocked all native calcium channel currents studied, with the exception of T-type currents recorded from GH3 cells. Examination of transiently expressed calcium channels in oocytes showed that DW13.3 had the highest affinity for alpha1A, followed by alpha1B > alpha1C > alpha1E. The affinity of DW13.3 for alpha1B N-type currents varied by 10-fold between expressed channels and native currents. Although block occurred in a similar 1:1 manner for all subtypes, DW13.3 produced a partial block of both alpha1A currents and P-type currents in cerebellar Purkinje cells. Selective occlusion of the P/Q-type channel ligand omega-conotoxin MVIIC (but not omega-agatoxin IVA) from its binding site in Purkinje neurons suggests that DW13.3 binds to a site close to the pore of the channel. The inhibition of different subtypes of calcium channels by DW13.3 reflects a common "macro" binding site present on all calcium channels except T-type.  相似文献   
29.
Deriving a preference-based single index from the UK SF-36 Health Survey   总被引:1,自引:0,他引:1  
This article presents the results of a study to derive a preference-based single index from the SF-36. The study was an attempt to reconcile a profile health status measure, the SF-36, with the "quality adjusted life years" approach. The study undertook a parsimonious restructuring of the SF-36 using explicit criteria to form the SF-6D health state classification. A sample of multidimensional health states defined by this classification were valued by a convenience sample of health professionals, managers, and patients, who responded to a set of visual analogue scale ratings and standard gamble questions, with highly complete and consistent answers. Statistical models were estimated to predict single index scores for all 9000 health states defined by the new classification. The resultant algorithms can be applied to existing SF-36 data sets and used in the assessment of the cost-effectiveness of health technologies. This preliminary work forms the basis of a larger study currently being undertaken in the UK.  相似文献   
30.
Mesangial cells (MC) of renal glomeruli respond to immune-inflammatory injury by accelerated proliferation and generation of reactive oxygen metabolites (ROM). We studied in vivo and in vitro roles of cAMP-protein kinase A (PKA) signaling in modulation of these pathobiologic processes with focus on PDE isozymes. Mitogenic synthesis of DNA in mesangial cells grown in primary culture was blocked by forskolin and dibutyryl cyAMP. Incubation of MC with PDE-3 inhibitors, cilostamide and lixazinone, inhibited (> 50%) mitogenesis, whereas inhibitors of PDE-4, rolipram and denbufylline, caused little or no inhibition. Conversely, inhibitors of PDE-4 suppressed generation of ROM in MC, whereas inhibitors of PDE-3 had no effect. Incubation of mesangial cells with cilostamide or with rolipram increased in situ activity of PKA, and effects of the two inhibitors were additive. PDE inhibitors also decreased activity of mitogen-activated protein kinase. The efficacy of PDE isozyme inhibitors (IC50) to suppress mitogenesis or ROM generation paralleled IC50 for inhibition of cAMP hydrolysis by extracts from mesangial cells. Administration of lixazinone or lixazinone in combination with rolipram to rats with mesangial proliferative glomerulonephritis induced by antithymic serum suppressed proliferation of mesangial cells and also reduced other histopathologic manifestations of the disease. Based on these observations, we propose that in MC, a cAMP pool that is hydrolyzed by PDE-3 inhibits by negative crosstalk via activation of PKA, mitogen-activated protein kinase (MAPK) pathway, and mitogenesis; whereas cAMP pool linked to PDE-4 inhibits, also via activation of PKA, ROM generation in mesangial cells. Results also suggest that PDE isozyme inhibitors, in particular inhibitors of PDE-3, should be investigated for potential use for "signal transduction pharmacotherapy" of glomerulonephritis.  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