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   1944篇
  免费   0篇
化学工业   9篇
轻工业   1篇
石油天然气   1篇
无线电   2篇
一般工业技术   2篇
冶金工业   1927篇
自动化技术   2篇
  2017年   1篇
  2010年   2篇
  2007年   1篇
  2005年   1篇
  2004年   1篇
  2003年   2篇
  1999年   57篇
  1998年   570篇
  1997年   320篇
  1996年   195篇
  1995年   116篇
  1994年   113篇
  1993年   111篇
  1992年   24篇
  1991年   39篇
  1990年   27篇
  1989年   43篇
  1988年   37篇
  1987年   25篇
  1986年   26篇
  1985年   18篇
  1984年   1篇
  1983年   7篇
  1982年   13篇
  1981年   7篇
  1980年   12篇
  1979年   1篇
  1978年   2篇
  1977年   51篇
  1976年   119篇
  1975年   2篇
排序方式: 共有1944条查询结果,搜索用时 0 毫秒
161.
A dietary treatment plan that considers both quality-of-care and quality-of-life issues is most beneficial for elderly patients. Diabetes can be successfully managed in most elderly patients with a liberalized diet that is low in simple sugars and includes variety and moderation in food choices. Although dietary management in osteoporosis may be most compelling in its preventive capacity, clinicians treating elderly patients with osteoporosis are well advised to consider supplementation of the diet with calcium and vitamin D in amounts equal to the RDAs if patients are unable to consume adequate calcium and vitamin D and if exposure to sunlight is minimal. Encouraging calcium intake, moderate exercise, maintenance of desirable body weight, and avoidance of laxative and antacid abuse with patients throughout the life cycle is appropriate preventive advice. The elderly renal failure patient may benefit from dietary modification of protein, potassium, sodium, fluid, vitamins, and minerals when complications associated with these nutrients are present. Because clinicians treat significant numbers of elderly diabetic, osteoporotic, and renal failure patients, and because many skilled nursing facilities are developing specialty and rehabilitation units for such high-acuity level patients, the clinician is well advised to know how to maximize quality of care and quality of life for these patients through appropriate dietary intervention.  相似文献   
162.
Metabotropic glutamate receptors (mGluRs) are a heterogeneous family of G protein-coupled glutamate receptors that are linked to multiple second messenger systems in the CNS. In this study the selectivity of mGluR agonists for different mGluR second messenger effects was characterized in slices of the rat hippocampus. The mGluR agonists (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid and (2S,3S,4S)alpha-(carboxycyclopropyl)glycine produced multiple effects on second messengers that included enhanced phosphoinositide hydrolysis in both adult and neonatal rat hippocampus, inhibition of forskolin-stimulated cyclic AMP (cAMP) formation in adult tissue, and increases in basal cAMP formation in the neonatal hippocampus. In contrast, 3,5-dihydroxyphenylglycine was potent and effective in increasing phosphoinositide hydrolysis in both adult and neonatal hippocampus but unlike the other mGluR agonists did not inhibit forskolin-stimulated cAMP formation (in the adult) or substantially enhance basal cAMP formation (in the neonate). Thus, in the rat hippocampus mGluR agonist-mediated increases or decreases in cAMP formation are not secondary to mGluR-mediated changes in phosphoinositide hydrolysis. Furthermore, 3,5-dihydroxyphenylglycine can be used to activate subpopulations of mGluRs coupled to phosphoinositide hydrolysis with minimal effects on cAMP-mGluR second messenger systems.  相似文献   
163.
Mechanisms for the abnormal copper (Cu) accumulation in the liver of LEC rats were examined using primary cultured liver parenchymal cells prepared from mutant LEC rats and those from control LEA rats (original strain). The Cu and metallothionein (MT) mRNA levels in the liver of LEC rats were caused to decrease to the same levels as those of LEA rats by removing Cu in vivo selectively with tetrathiomolybdate. Cu was taken up by LEC rat cells to the same extent as LEA rat cells by exposure to low medium Cu and to a higher extent by exposure to high medium Cu, while the MT mRNA level in LEC rat cells increased dose-dependently at a much higher rate than that in LEA rats. MT mRNA levels in both cells were comparable by exposure to cadmium, zinc and dexamethasone. The results indicate that expression of MT mRNA is selectively enhanced by Cu in LEC cells despite the fact that uptake of Cu is comparable with normal cells.  相似文献   
164.
165.
We have studied the efficacy of two extradural infusions (10 ml h-1) in 50 patients in active labour. Patients in the diamorphine group (n = 25) received 0.0625% plain bupivacaine 6.25 mg h-1 mixed with 0.005% diamorphine 0.5 mg h-1 and those in the control group (n = 25) received 0.125% plain bupivacaine 12.5 mg h-1. Both groups received intermittent "top-ups" of 0.25% bupivacaine 10 ml when indicated. Although median pain scores during the infusion were similar in both groups, patients in the diamorphine group indicated greater satisfaction with the infusion (88% very satisfied, compared with 52% in the control group (P < 0.02)). There were no differences in the incidence of hypotension, instrumental vaginal delivery, number of "top-ups", duration of the second stage or extent of motor block. However, patients in the diamorphine group had a high incidence of pruritus (44%, compared with 0% in the control group (P < 0.01)).  相似文献   
166.
Incidence and recognition of malnutrition in hospital   总被引:2,自引:0,他引:2  
OBJECTIVES: To determine incidence of malnutrition among patients on admission to hospital, to monitor their changes in nutritional status during stay, and to determine awareness of nutrition in different clinical units. DESIGN: Prospective study of consecutive admissions. SETTING: Acute teaching hospital. SUBJECTS: 500 patients admitted to hospital: 100 each from general surgery, general medicine, respiratory medicine, orthopaedic surgery, and medicine for the elderly. MAIN OUTCOME MEASURES: Nutritional status of patients on admission and reassessment on discharge, review of case notes for information about nutritional status. RESULTS: On admission, 200 of the 500 patients were undernourished (body mass index less than 20) and 34% were overweight (body mass index > 25). The 112 patients reassessed on discharge had mean weight loss of 5.4%, with greatest weight loss in those initially most undernourished. But the 10 patients referred for nutritional support showed mean weight gain of 7.9%. Review of case notes revealed that, of the 200 undernourished patients, only 96 had any nutritional information documented. CONCLUSION: Malnutrition remains a largely unrecognised problem in hospital and highlights the need for education on clinical nutrition.  相似文献   
167.
OBJECTIVE: The aim of this study was to determine the reliability and validity of a proposed measure of peritraumatic dissociation and, as part of that effort, to determine the relationship between dissociative experiences during disturbing combat trauma and the subsequent development of posttraumatic stress disorder (PTSD). METHOD: A total of 251 male Vietnam theater veterans from the Clinical Examination Component of the National Vietnam Veterans Readjustment Study were examined to determine the relationship of war zone stress exposure, retrospective reports of dissociation during the most disturbing combat trauma events, and general dissociative tendencies with PTSD case determination. RESULTS: The total score on the Peritraumatic Dissociation Experiences Questionnaire--Rater Version was strongly associated with level of posttraumatic stress symptoms, level of stress exposure, and general dissociative tendencies and weakly associated with general psychopathology scales from the MMPI-2. Logistic regression analyses supported the incremental value of dissociation during trauma, over and above the contributions of level of war zone stress exposure and general dissociative tendencies, in accounting for PTSD case determination. CONCLUSIONS: These results provide support for the reliability and validity of the Peritraumatic Dissociation Experiences Questionnaire--Rater Version and for a trauma-dissociation linkage hypothesis: the greater the dissociation during traumatic stress exposure, the greater the likelihood of meeting criteria for current PTSD.  相似文献   
168.
The effect of Evans blue (EB) on large-conductance Ca2+-activated K+ (BKCa) channels was investigated in cultured endothelial cells of human umbilical veins. In whole-cell configuration, EB (50 microM) reversibly increased the amplitude of K+ outward currents (IK). When the patch pipettes were filled with 10 mM EGTA, its stimulatory effect on IK was unaltered. Further application of EB in the presence of suramin, a blocker of P2-purinergic receptor, or AOPCP, an inhibitor of 5'-nucleotidase, still increased IK. However, charybdotoxin (100 nM) suppressed EB-induced increase in IK. In inside-out configuration, bath application of EB (50 microM) did not change single channel conductance but significantly increased the activity of BKCa channels. The EB-induced increase in the activity of BKCa channels was independent on internal Ca2+. EB (50 microM) shifted the activation curve of BKCa channels to less positive membrane potentials by approximately 20 mV. The change in the kinetic behavior of BKCa channels caused by EB in these cells is due to an increase in mean open time and a decrease in mean closed time. These results indicate that EB can stimulate the activity of BKCa channel in endothelial cells. This effect is unrelated to its blockade of P2-purinergic receptors or inhibition of 5'-nucleotidase. The direct stimulation of these ionic channels by EB may contribute to its effect on capillary permeability.  相似文献   
169.
We performed genetic linkage analysis in nine German proximal myotonic myopathy (PROMM) families using DNA-markers D3S1541 and D3S1589 from the region of the recently discovered gene locus of myotonic dystrophy type 2 (DM2) on chromosome 3q. Two-point analysis supplied an lod score of 5.9. We conclude that a gene causing PROMM is located on chromosome 3q. PROMM and DM2 may be allelic disorders or may be caused by closely linked genes.  相似文献   
170.
T cells show a bias in their migration pathways: some T cells preferentially migrate to peripheral lymph nodes (LN), some to mucosal tissues, and some to peripheral tissues such as skin. These recirculation pathways were examined in sheep by collecting lymph draining into and out of peripheral and intestinal LN, and using fluorescent dyes to trace the recirculation of the lymph cells. Monoclonal antibodies (mAb) to alpha 4, beta 1, and beta 7 integrins, and L-selectin, were used to define three major populations of recirculating T cells. Naive-type T cells (L-selectin+, alpha 4 beta 1lo beta 7lo) migrated preferentially through peripheral LN. Two memory populations could be defined: alpha 4 beta 1hi beta 7- and alpha 4 beta 7hi beta 1lo. alpha 4 beta 1hi beta 7- T cells were present in lymph draining from the skin. T cells migrating preferentially through intestinal LN were alpha 4 beta 7hi beta 1lo. Consistent with this migration pattern, the endothelial receptor for alpha 4 beta 7, mucosal addressin cell adhesion molecule-1 (MAdCAM-1) was detected on high endothelial venules within intestinal LN and Peyer's patches, but only weakly on high endothelial venules within peripheral LN. Thus, there are at least three easily definable subsets of T cells, based on integrin expression, which show distinct migration preferences.  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