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   4140篇
  免费   0篇
化学工业   12篇
金属工艺   1篇
机械仪表   1篇
建筑科学   1篇
矿业工程   1篇
能源动力   1篇
轻工业   3篇
无线电   1篇
一般工业技术   4篇
冶金工业   4110篇
自动化技术   5篇
  2022年   1篇
  2021年   1篇
  2016年   1篇
  2013年   2篇
  2011年   4篇
  2010年   2篇
  2009年   1篇
  2007年   1篇
  2006年   1篇
  2005年   2篇
  2004年   2篇
  2003年   12篇
  1999年   122篇
  1998年   1223篇
  1997年   760篇
  1996年   452篇
  1995年   253篇
  1994年   206篇
  1993年   249篇
  1992年   32篇
  1991年   37篇
  1990年   53篇
  1989年   47篇
  1988年   69篇
  1987年   46篇
  1986年   44篇
  1985年   43篇
  1983年   5篇
  1982年   19篇
  1981年   29篇
  1980年   40篇
  1978年   4篇
  1977年   121篇
  1976年   242篇
  1975年   5篇
  1974年   1篇
  1973年   1篇
  1961年   1篇
  1955年   5篇
  1954年   1篇
排序方式: 共有4140条查询结果,搜索用时 46 毫秒
101.
The circadian pattern of hemocoagulation was studied in patients with decompensated rheumatic heart disease (DRHD) concurrent with stages I-II circulatory failure (CF) during complex treatment or medical treatment with disaggregants. Biorhythmological studies demonstrated that in patients with DRHD and CF chronotherapy with curantyl had some advantages over the traditional therapy during complex drug therapy. In these patients, the chronopatterns of circadian rhythms of hemocoagulative parameters tended to normalize under the influence of curantyl chronotherapy, by diminishing the signs of external desynchronization. Advantages of chronotherapy over the traditional treatment found in patients with DRHD and stages I-II CF, as manifested by its clinical effect in shorter periods (on days 4-5) when small daily and course doses of the drug were used. Based on the biorhythmological studies of hemostatic parameters, a method of curantyl chronotherapy was developed for patients with DRHD and stages I-II CF, which may optimize the therapeutical process in patients with this abnormality.  相似文献   
102.
103.
The glucooligosaccharides (GOS), produced by Leuconostoc mesenteroides NRRL B-1299 dextransucrase through an acceptor reaction with maltose and sucrose, were purified by reverse phase chromatography. Logarithmic plots of retention time vs. dp of the GOS gave three parallel lines suggesting the existence of at least three families of homologous molecules. The structure (13C and 1H NMR spectroscopy) and reactivity of the purified molecules of the three families were investigated. All the products bear a maltose residue at the reducing end. The GOS in the first family (named OD) contained additional glucosyl residues all alpha-(1-->6) linked. The smallest molecule in this first series was panose or alpha-D-glucopyranosyl-(1-->6)-D-maltose (dp 3). All the OD molecules were shown to be good acceptors for dextransucrase in the presence of sucrose. The second family, named R, was composed of linear GOS containing alpha-(1-->6)-linked glucosyl residues and a terminal alpha-(1-->2)-linked residue at the non-reducing end of the molecule; the smallest molecule in this family was alpha-D-glucopyranosyl-(1-->2)-D-panose (dp 4). The third family, R', was formed of GOS containing additional residues linked through alpha-(1-->6) linkages that constitute the linear chain, and an alpha-(1-->2)-branched residue located on the penultimate element of the chain, near the non-reducing end. The smallest molecule in this series is alpha-D-glucopyranosyl-(1-->6)-[alpha-D-glucopyranosyl-(1-->2)]-alpha-D- glucopyranosyl-(1-->6)-D-panose, dp 6. R and R' GOS are very poor acceptors for L. mesenteroides NRRL B-1299 dextransucrase. This study makes it possible to suggest a rather simple reaction scheme, where molecules Ri, R'i and ODi of the same dp all result from the glucosylation of the same GOS: ODi-l.  相似文献   
104.
Site-specific regeneration of the liver after 70% partial hepatectomy was investigated noninvasively in terms of protein synthesis using PET with L-[methyl-11C]methionine in a living animal. Protein synthesis in rat liver at 24 hr after partial hepatectomy did not occur uniformly in the whole liver but intensely in the middle part of the regenerating organ in comparison with the other parts. The activity was significantly low at the posterior aspect of the liver. On the other hand, site-specific protein synthesis was not observed in normal liver. These results were confirmed by bioimaging analyzer system (BAS) analysis, an invasive method that indicates radioactivities of precise intrahepatic sites. DNA synthesis in regenerating liver was also monitored with [2-14C]thymidine and analyzed by BAS 24 hr after 70% hepatectomy. Site-specific DNA synthesis in regenerating liver corresponding to the protein synthesis was also observed by BAS analysis. These results indicate that liver regeneration occurs intensely in the middle part of the liver and that PET enables noninvasive in vivo biochemical analysis.  相似文献   
105.
Structural analogues of ZAPA, Z-3-[(aminoiminomethyl)thio]prop-2-enoic acid, an isothiouronium analogue of GABA, are potent GABAA agonists as seen in the isolated guinea-pig ileum and in the facilitation of [3H]diazepam binding to rat brain membranes. Compounds with guanidino or amidine groups replacing the amino functionality of GABA were also found to be active. The highest activity was displayed by the isothiouronium salts in which the conformational flexibility of the molecule is restricted by a Z-substituted carbon-carbon double bond. A series of bis-isothiouronium compounds was prepared from aliphatic alpha, omega-bis-thioureas as mixtures of E and Z adducts. Maximum GABAA agonist activity for this series was found with a C6-C8 carbon chain, and the results were consistent with an interaction at the GABAA receptor with only one end of the molecule, rather than the more potent effect expected of a molecule bridging two active sites. GABAA antagonist/partial agonist activity was observed on the guinea pig isolated ileum for a number of different analogue types, with the most potent being bis-isothiouronium derivatives. None of the substituted derivatives of ZAPA was as active as ZAPA itself, and maximum GABAA activity was found in the n-pentyl and n-hexyl analogues.  相似文献   
106.
The analysis of health state of drivers sent for an extra health examination for the estimation of driving capability for the driving of motor vehicle in alcoholic state was presented. The study included 380 drivers who were found driving drunk by traffic police (studied group) and 180 drivers of control group sent for an extra health examination for some other reason. The disorders in psychomotor sphere were noticed in the drivers of studied group and it was determined that they had caused significantly larger number of traffic accidents in last five-year period compared to the drivers of control group. The alcohol consumption in driving population represents significant medical, social, economic and traffic problem. The control of driver's alcoholism, the sending of alcoholic drivers to an extra health examination for the repeated estimation of driving capability and including in therapeutic and health-educational program can present significant measure of the primary prevention of road traffic traumatism which is on the constant increase.  相似文献   
107.
108.
109.
110.
The mechanisms responsible for long-lasting, activity-dependent decreases in synaptic efficacy are not well understood. We have examined the initial steps required for the induction of long-term depression (LTD) in CA1 pyramidal cells by repetitive low frequency (1 Hz) synaptic stimulation. This form of LTD was synapse specific, was saturable, and required activation of post-synaptic NMDA receptors. Loading CA1 cells with the Ca2+ chelator BAPTA prevented LTD, whereas lowering extracellular Ca2+ resulted in the induction of LTD by stimulation that previously elicited long-term potentiation. Following LTD, synaptic strength could be increased to its original maximal level, indicating that LTD is reversible and not due to deterioration of individual synapses. Induction of homosynaptic LTD therefore requires an NMDA receptor-dependent change in postsynaptic Ca2+ which may be distinct from that required for long-term potentiation.  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