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   6764篇
  免费   0篇
  国内免费   1篇
化学工业   22篇
金属工艺   1篇
机械仪表   1篇
能源动力   1篇
轻工业   6篇
石油天然气   2篇
无线电   5篇
一般工业技术   12篇
冶金工业   6707篇
原子能技术   1篇
自动化技术   7篇
  2014年   1篇
  2010年   1篇
  2009年   1篇
  2007年   3篇
  2006年   3篇
  2005年   2篇
  2004年   5篇
  2003年   11篇
  2002年   1篇
  2000年   4篇
  1999年   213篇
  1998年   2301篇
  1997年   1280篇
  1996年   807篇
  1995年   421篇
  1994年   336篇
  1993年   414篇
  1992年   37篇
  1991年   47篇
  1990年   53篇
  1989年   47篇
  1988年   54篇
  1987年   56篇
  1986年   53篇
  1985年   36篇
  1984年   1篇
  1983年   18篇
  1982年   24篇
  1981年   30篇
  1980年   61篇
  1979年   3篇
  1978年   13篇
  1977年   136篇
  1976年   277篇
  1975年   11篇
  1973年   1篇
  1955年   3篇
排序方式: 共有6765条查询结果,搜索用时 15 毫秒
51.
Flaujeac trait is the functional deficiency of a plasma protein of the intrinsic coagulation, kinin-forming, and plasma fibrinolytic pathways. The Flaujeac factor in man has been isolated and tentatively identified as a kininogen of high molecular weight (HMW). Highly purified bovine HMW-kininogen, but not bovine low molecular weight kininogen, repaired Flaujeac factor deficiency. The two subspecies of this molecule, HMW-kininogen a and HMW-kininogen b, also corrected Flaujeac factor deficiency. When bovine HMW-kininogen was incubated with bovine plasma kallikrein, kinin-free HMW-kininogen, bradykinin, and a glycopeptide fragment (peptide 1-2; 12,584 daltons) were rapidly released. None of these fragmentation products corrected Flaujeac factor deficiency alone or in mixtures. The function of HMW-kininogen appeared to depend upon the structural integrity of the native molecule. When injected in concentrations of 2 pmol-8 nmol/0.1 ml, peptide 1-2 caused increased vascular permeability in rabbits, rats, or guinea pigs. The enhanced permeability was maximal within 1-2 min and terminated in 5-10 min, differing from that of bradykinin or histamine. Injected together in equimolar amounts, peptide 1-2 and bradykinin produced a synergistic permeability response which was immediate in onset as well as prolonged in duration. Peptide 1-2 is a rapidly acting, highly basic glyco-peptide which mediates increased vascular permeability in a complementary and synergistic manner with bradykinin.  相似文献   
52.
53.
54.
Sufu is made by solid state fungal fermentation (using Actinomucor elegans) of tofu, followed by salting and maturation in dressing mixtures containing salt, alcohol and various other ingredients. NaCl in dressing mixtures strongly affected the changes in textural properties and the hydrolysis of protein and lipid of sufu. Higher salt contents (14% w/w) resulted in increased hardness (+100%) and elasticity (+18%) and reduced adhesiveness (?30%). Hardness and elasticity could be used to judge the extent of sufu ripening. SDS‐PAGE showed the disappearance of all protein subunits at 80 and 110 g kg?1 salt content; however, some protein subunits were still detectable at 140 g kg?1 salt content after 60 days of ripening. Higher ratios of free amino nitrogen to total nitrogen (FAN/TN = 0.4–0.45) and free amino acids to crude protein (FAA/CP = 0.24–0.26) were observed in sufu with lower (80 g kg?1) salt content. FAN/TN and FAA/CP in white sufu (obtained with dressing mixtures containing only salt and alcohol) were higher than those in red sufu (obtained with dressing mixtures containing angkak or kojic red rice) owing to different dressing mixture compositions. Increases in free fatty acids (FFA) were also observed during ripening. FFA levels in sufu with lower salt content increased rapidly during the first 30–40 days and then increased slowly, probably resulting from the formation of fatty acid esters. Lowering the salt content (80 g kg?1) can shorten the ripening time to 40 days, which is of benefit to manufacturers. However, sufu will spoil, ie undergo souring, during the ripening stage at salt contents of 50 g kg?1 or lower. Copyright © 2003 Society of Chemical Industry  相似文献   
55.
CONTEXT: Many groups have developed guidelines to shorten hospital length of stay in pneumonia in order to decrease costs, but the length of time until a patient hospitalized with pneumonia becomes clinically stable has not been established. OBJECTIVE: To describe the time to resolution of abnormalities in vital signs, ability to eat, and mental status in patients with community-acquired pneumonia and assess clinical outcomes after achieving stability. DESIGN: Prospective, multicenter, observational cohort study. SETTING: Three university and 1 community teaching hospital in Boston, Mass, Pittsburgh, Pa, and Halifax, Nova Scotia. PATIENTS: Six hundred eighty-six adults hospitalized with community-acquired pneumonia. MAIN OUTCOME MEASURES: Time to resolution of vital signs, ability to eat, mental status, hospital length of stay, and admission to an intensive care, coronary care, or telemetry unit. RESULTS: The median time to stability was 2 days for heart rate (< or =100 beats/min) and systolic blood pressure (> or =90 mm Hg), and 3 days for respiratory rate (< or =24 breaths/min), oxygen saturation (> or =90%), and temperature (< or =37.2 degrees C [99 degrees F]). The median time to overall clinical stability was 3 days for the most lenient definition of stability and 7 days for the most conservative definition. Patients with more severe cases of pneumonia at presentation took longer to reach stability. Once stability was achieved, clinical deterioration requiring intensive care, coronary care, or telemetry monitoring occurred in 1% of cases or fewer. Between 65% to 86% of patients stayed in the hospital more than 1 day after reaching stability, and fewer than 29% to 46% were converted to oral antibiotics within 1 day of stability, depending on the definition of stability. CONCLUSIONS: Our estimates of time to stability in pneumonia and explicit criteria for defining stability can provide an evidence-based estimate of optimal length of stay, and outline a clinically sensible approach to improving the efficiency of inpatient management.  相似文献   
56.
57.
We combined histofluorescence with in situ hybridization to identify GABAergic neurons in the arcuate nucleus (ARC) following electrophysiological recordings, using GAD65 as a marker. Intracellular recordings were made in hypothalamic slices prepared from ovariectomized guinea pigs. Over 90% of ARC neurons tested with the GABA(B) receptor agonist baclofen responded with a membrane hyperpolarization or an outward current. The hyperpolarization was dose-dependent, and the GABA(B) receptor antagonist CGP 35,348 produced a rightward shift in the agonist dose-response curve. Agonist potency was lower, and the efficacy greater, in GAD-positive neurons. The use of this novel technique for identifying GABAergic neurons thus reveals differences in the pharmacodynamics of GABA(B) receptor activation GABAergic and non-GABAergic ARC neurons.  相似文献   
58.
59.
Four samples each of clear and lightly (thin), moderately, and heavily (thick) meconium-stained amniotic fluid were divided in two portions and submitted twice for assessment to 20 midwives (a total of 320 case assessments). None of the midwives completely agreed with the standard assessment for more than 85 percent of the cases. When disregarding clear samples, for which there was good agreement, each of the midwives classified on average only 35.8 percent of the meconium-stained samples in the same category on each of the four occasions that they were presented to them. Calculation of kappa statistics, which express proportional agreement corrected for chance, indicated that none of the midwives showed very good agreement (kappa > 0.81) with the standard and that fewer than 10 percent showed very good agreement with themselves. The data indicate that grading the severity of meconium staining by visual assessment has such poor accuracy and precision that it cannot provide a valid basis for assigning different care policies to different degrees of meconium staining.  相似文献   
60.
The methylation of phosphatidylethanolamine is an auxiliary pathway for phosphatidylcholine biosynthesis in liver. Two forms of the enzyme, phosphatidylethanolamine N-methyltransferase, which catalyses this reaction, are located on the endoplasmic reticulum and mitochondria-associated membranes. Both forms are encoded by a single murine gene, Pempt, located on chromosome 11. The expression of the gene begins at birth. An inverse relationship exists between the rate of liver growth and the expression of phosphatidylethanolamine N-methyltransferase. However, disruption of the Pempt gene does not alter liver growth in mice or cause any other obvious phenotype.  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