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   1962篇
  免费   0篇
  国内免费   2篇
电工技术   1篇
综合类   1篇
化学工业   7篇
金属工艺   2篇
一般工业技术   1篇
冶金工业   1949篇
自动化技术   3篇
  2022年   1篇
  2015年   1篇
  2014年   2篇
  2011年   1篇
  2009年   1篇
  2005年   1篇
  2002年   1篇
  2001年   1篇
  2000年   2篇
  1999年   84篇
  1998年   567篇
  1997年   336篇
  1996年   201篇
  1995年   133篇
  1994年   112篇
  1993年   133篇
  1992年   11篇
  1991年   21篇
  1990年   18篇
  1989年   21篇
  1988年   34篇
  1987年   21篇
  1986年   16篇
  1985年   24篇
  1983年   3篇
  1982年   7篇
  1981年   12篇
  1980年   16篇
  1979年   2篇
  1978年   6篇
  1977年   50篇
  1976年   121篇
  1975年   2篇
  1955年   2篇
排序方式: 共有1964条查询结果,搜索用时 15 毫秒
61.
OBJECTIVE: This retrospective study was undertaken to show the efficacy and safety of one-step needle aspiration and lavage for the treatment of nonenteric, nonpancreatic abdominal and pelvic abscesses. MATERIALS AND METHODS: Eighty-two nonconsecutive patients (age range, 4-81 years old) with 97 abdominal and pelvic abscesses were treated over 16 years with a one-step percutaneous needle aspiration and lavage technique. Abscesses were drained with sonographic or CT guidance in a single session. An 18-gauge needle was used for aspiration and repeated saline lavage; no drainage catheter was left in place. For collections that appeared multiloculated, needle repositioning and repeated aspiration and lavage were performed during the single session. All patients received i.v. antibiotics. RESULTS: Eighty-seven (90%) of 97 abscesses in 72 of 82 patients were successfully treated, including 17 (85%) of 20 abscesses that were multiloculated. The only two complications were transient sepsis in one patient and hemorrhage in one patient that resolved with transfusion and conservative treatment. Needle aspiration and lavage failures were associated with diffuse peritonitis, occult malignancy, unsuspected enteric communication, and a dropped surgical clip. CONCLUSION: Percutaneous needle aspiration and lavage can be a safe, effective alternative to the more conventional treatment of prolonged catheter drainage. In selected patients, including certain patients with multiloculated abscesses, one-step needle aspiration and lavage should be considered as the initial method of treatment.  相似文献   
62.
63.
5-Hydroxy- and 5-oxo-eicosatetraenoate (5-HETE and 5-oxoETE) activate polymorphonuclear neutrophils (PMNs) through a common, receptor-like recognition system. To define this system, we examined the interaction of these eicosanoids with human PMNs. PMNs esterified 5-[3H]HETE to glycerolipids at 37 and 4 degreesC. At 37 but not 4 degreesC, the cells also hydroxylated the label to 5, 20-[3H]diHETE. The acyl:CoA synthetase blocker, triacsin C, inhibited esterification but also led to an increase in the hydroxylation of the label. PMNs processed 5-[3H]oxoETE through the same pathways but only or principally after reducing it to 5-[3H]HETE (37 or 4 degreesC). In the presence of these varying metabolic reactions, PMNs (37 or 4 degreesC; +/- triacsin C) could not be shown to receptor bind either radiolabel. Plasma membranes isolated from PMNs esterified but unlike whole cells did not reduce or hydroxylate 5-[3H]oxoETE. Triacsin C blocked esterification, thereby rendering the membranes unable to metabolize this radiolabel. Indeed, triacsin C-treated membranes bound (Kd = 3.8 nM) 5-[3H]oxoETE specifically and reversibly to 86 pmol of sites per 25 micrograms of membrane protein. 5-OxoETE, 5-HETE, and 5,15-diHETE displaced this binding at concentrations correlating with their potency in eliciting PMN Ca2+ transients. GTP and GTPgammaS, but not ATP or ATPgammaS, also reduced 5-[3H]oxoETE binding, whereas 15-HETE, leukotriene B4, platelet-activating factor, IL-8, C5a, and N-formyl-Met-Leu-Phe lacked this effect. We conclude that PMNs and their plasma membranes use an acyl:CoA synthetase-dependent route to esterify 5-HETE and 5-oxoETE into lipids. Blockade of the synthetase uncovers cryptic plasmalemma sites that bind 5-oxoETE with exquisite specificity. These sites apparently mediate responses to the 5-oxo class of eicosanoids and are likely members of the serpentine superfamily of G protein-linked receptors.  相似文献   
64.
65.
66.
To improve the detection of lactate dehydrogenase-elevating virus (LDV), we developed a PCR assay. Primers were selected from ORF7, encoding nucleocapsid protein VP1. No specific amplification was observed with any other common murine virus or with RNAs from the closely related Lelystad virus and equine arteritis virus. In experimentally infected mice, LDV could be detected in plasma in both the acute and the persistent phases. LDV was also detected by the PCR in contaminated pools of Plasmodium berghei parasites which were maintained in mice, both by a direct analysis of the samples and by testing of plasma from mice inoculated with these pools. There was a complete agreement between the results of the PCR assay and the lactate dehydrogenase (LDH) enzyme assay of plasma from the inoculated mice. In contrast to the results of the LDH enzyme assay, no false-positive reactions were obtained in the PCR assay with negative control samples showing visible hemolysis. Storage of plasma samples at room temperature and at 4, -20, and -80 degrees C for up to 8 days did not influence the results of the PCR. These results show that the PCR is a valuable technique which may replace the LDH test as a diagnostic tool.  相似文献   
67.
Earlier studies with ruminants point to a depressant effect of dietary iron on the copper status. To verify this we determined hepatic copper concentrations in dry, non-pregnant goats subjected to a 56 x 56-days cross-over trial with adequate copper rations containing either 269 or 2380 mg iron/kg dry matter. High iron intake reduced the group mean plasma copper (by 18%) and caeruloplasmin activity (by 13%) and produced a significant decrease (27%) in hepatic copper concentrations. Hepatic iron concentrations were raised (by 56%) after feeding the high iron ration. It is concluded that high dietary levels of iron, within the range of their fluctuation in silage and forage, can impair the copper status of ruminants, especially when concurrent intakes of copper are low.  相似文献   
68.
An elevation in the concentration of total plasma homocysteine is known to be an independent risk factor for the development of vascular disease. Alterations in homocysteine metabolism have also been observed clinically in diabetic patients. Patients with either type 1 or type 2 diabetes who have signs of renal dysfunction tend to exhibit elevated total plasma homocysteine levels, whereas type 1 diabetic patients who have no clinical signs of renal dysfunction have lower than normal plasma homocysteine levels. The purpose of this study was to investigate homocysteine metabolism in a type 1 diabetic animal model and to examine whether insulin plays a role in its regulation. Diabetes was induced by intravenous administration of 100 mg/kg streptozotocin to Sprague-Dawley rats. We observed a 30% reduction in plasma homocysteine in the untreated diabetic rat. This decrease in homocysteine was prevented when diabetic rats received insulin. Transsulfuration and remethylation enzymes were measured in both the liver and the kidney. We observed an increase in the activities of the hepatic transsulfuration enzymes (cystathionine beta-synthase and cystathionine gamma-lyase) in the untreated diabetic rat. Insulin treatment normalized the activities of these enzymes. The renal activities of these enzymes were unchanged. These results suggest that insulin is involved in the regulation of plasma homocysteine concentrations by affecting the hepatic transsulfuration pathway, which is involved in the catabolism of homocysteine.  相似文献   
69.
OBJECTIVE: To determine whether slow nocturnal hemodialysis (SNHD) can be safely performed in patients with end-stage renal disease to improve the biochemical and clinical outcome. MATERIAL AND METHODS: We conducted an 8-week pilot study in nondiabetic adult patients, who underwent dialysis 6 nights per week for 8 hours each night. A dialysate flow rate of 300 mL/min and a blood flow rate of 250 mL/min, through an internal jugular dual-lumen venous catheter, were used. The equipment used was a COBE Centry System 3 dialysis machine and Fresenius F-80 (1.8 m2) or Baxter CT 190 (1.9 m2) dialyzers. Five patients were enrolled in the study. RESULTS: Two patients did not complete the study because of catheter-related infections--one at day 7 and one after 4 weeks of SNHD. All patients had improved blood pressure control, and no intradialytic adverse events occurred. Dietary intake improved, urea and creatinine levels significantly decreased, and weekly delivery of dialysate increased on SNHD. Potassium, chloride, beta 2-microglobulin, phosphorus, calcium, and high-density lipoprotein cholesterol all improved on SNHD. Serum testosterone increased in the three men on SNHD, but parathyroid hormone, luteinizing hormone, and follicle-stimulating hormone remained unchanged. Erythropoietin levels increased on SNHD, despite no change in exogenous erythropoietin doses in three patients and discontinuation of administration of erythropoietin in one. The following biochemical factors did not change significantly: serum sodium, bicarbonate, vitamin B12, folate, alkaline phosphatase, total cholesterol, triglycerides, and albumin. CONCLUSION: Higher doses of hemodialysis benefit nutrition, improve biochemical variables, and may improve many hormonal systems.  相似文献   
70.
BACKGROUND: The pathogenesis of cirrhotic ascites and hepatorenal syndrome remains unresolved. The involvement of both endothelin-1 and atrial natriuretic peptide have recently been suggested. This study investigated the concentrations of serum endothelin and atrial natriuretic peptide in cirrhotic patients. METHODS: Seven healthy subjects and 31 cirrhotic patients were studied. Cirrhotic patients were divided into three groups: Group I, 16 cirrhotic patients without ascites; Group II, 10 cirrhotic patients with ascites, but without hepatorenal syndrome; and Group III, five cirrhotic patients with hepatorenal syndrome and ascites. Their sera were analyzed for endothelin-1 and atrial natriuretic peptide concentrations. RESULTS: Cirrhotic patients with ascites, Group II and Group III, had higher plasma endothelin-1 concentrations (15.9 +/- 2.3 pg/ml and 24 +/- 2.1 pg/ml, respectively) than normal subjects and compensated cirrhotics (3.8 +/- 0.7 pg/ml and 6.4 +/- 1.1 pg/ml, respectively); p < 0.001). Atrial natriuretic peptide concentrations were also significantly higher in cirrhotic patients than in normal subjects (p < 0.025). Plasma endothelin-1 concentration had a negative correlation with creatinine clearance (r = -0.65, p < 0.001), as did atrial natriuretic peptide concentrations (r = -0.44, p = 0.012). Plasma endothelin-1 correlated significantly with atrial natriuretic peptide concentrations (r = 0.38, p = 0.035). CONCLUSIONS: Both endothelin-1 and atrial natriuretic peptide concentrations were elevated in cirrhotic patients with ascites and hepatorenal syndrome. Endothelin-1 may have a negative impact on renal function. Our data also suggested that impaired responsiveness rather than impaired secretion of atrial natriuretic peptide is responsible for sodium retention in cirrhotic patients with ascites.  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