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   2504篇
  免费   0篇
电工技术   1篇
化学工业   12篇
金属工艺   1篇
机械仪表   1篇
建筑科学   2篇
能源动力   2篇
轻工业   1篇
无线电   1篇
一般工业技术   4篇
冶金工业   2476篇
自动化技术   3篇
  2023年   2篇
  2019年   1篇
  2016年   2篇
  2013年   1篇
  2011年   1篇
  2010年   1篇
  2009年   2篇
  2008年   2篇
  2007年   1篇
  2006年   1篇
  2004年   1篇
  2003年   1篇
  2001年   1篇
  2000年   1篇
  1999年   58篇
  1998年   773篇
  1997年   456篇
  1996年   275篇
  1995年   186篇
  1994年   106篇
  1993年   150篇
  1992年   19篇
  1991年   26篇
  1990年   21篇
  1989年   17篇
  1988年   23篇
  1987年   29篇
  1986年   15篇
  1985年   14篇
  1983年   5篇
  1982年   11篇
  1981年   28篇
  1980年   18篇
  1978年   4篇
  1977年   85篇
  1976年   156篇
  1975年   5篇
  1973年   2篇
  1966年   1篇
  1955年   3篇
排序方式: 共有2504条查询结果,搜索用时 15 毫秒
941.
The results of treatment of 319 patients with acute pancreatitis are analyzed, 48 from them (15.1%)--with pancreanecrosis. Etiologic factors in destructive pancreatitis were alcohol addiction (41.67%), cholelithiasis (37.5%), hyperlipidemia (10.41%), hypercalcemia (4.17%), postoperative (4.17%). Location of the necrosis in parapancreatic fat cellular tissue was detected in 6 patients, in pancreatic head--in 8 and both in pancreatic head and corpus--in 11, in corpus and in tail--in 10; total pancreo-necrosis was observed in 5 patients. Therapeutic measures were conservative and only in cholelithiasis cholecystectomy was performed as well as drainage of the choledochus and abdominal cavity. Intensive care was aimed at blocking pancreatic and gastric secretion, inhibition of pancreatic enzymes ferments and suppressing mediators of inflammation, immunocorrection, prophylaxis of infection in the necrotic tissues. Desintoxication was carried out by combination of infusion therapy with forced diuresis, usage of extracorporeal methods and laparoscopic sanation of the abdominal cavity with subsequent lavage. Surgical interventions were carried out in far-off period only for complications of pancreanecrosis. Mortality rate in pancreanecrosis made up 20.85% and in total number of patients with acute pancreatitis--3.13%.  相似文献   
942.
CC chemokine receptors 1 and 3 (CCR1 and CCR3) are expressed by eosinophils; however, factors regulating their expression and function have not previously been defined. Here we analyze chemokine receptor expression and function during eosinophil differentiation, using the eosinophilic cell line HL-60 clone 15 as a model system. RNA for CCR1, -3, -4, and -5 was not detectable in the parental cells, and the cells did not specifically bind CC chemokines. Cells treated with butyric acid acquired eosinophil characteristics; expressed mRNA for CCR1 and CCR3, but not for CCR4 or CCR5; acquired specific binding sites for macrophage-inflammatory protein-1alpha and eotaxin (the selective ligands for CCR1 and CCR3, respectively); and exhibited specific calcium flux and chemotaxis responses to macrophage-inflammatory protein-1alpha, eotaxin, and other known CCR1 and CCR3 agonists. CCR3 was expressed later and at lower levels than CCR1 and could be further induced by IL-5, whereas IL-5 had little or no effect on CCR1 expression. Consistent with the HIV-1 coreceptor activity of CCR3, HL-60 clone 15 cells induced with butyric acid and IL-5 fused with HeLa cells expressing CCR3-tropic HIV-1 envelope glycoproteins, and fusion was blocked specifically by eotaxin or an anti-CCR3 mAb. These data suggest that CCR1 and CCR3 are markers of late eosinophil differentiation that are differentially regulated by IL-5 in this model.  相似文献   
943.
944.
The L-selectin leukocyte adhesion molecule plays an important role in controlling leukocyte extravasation in peripheral lymph nodes and at sites of tissue injury or infection. Although febrile responses during infection and inflammation are associated with enhanced immune activity, the contribution of fever-range temperatures to controlling lymphocyte recruitment to tissues has not been previously examined. In this report we provide evidence that direct exposure of lymphocytes to fever-range temperatures (38-41 degrees C) in vitro for 9 to 24 h resulted in a >100% increase in L-selectin-dependent adhesion of these cells to lymph node high endothelial venules (HEV). Moreover, culture of lymphocytes under hyperthermia conditions markedly enhanced the ability of these cells to traffic in an L-selectin-dependent manner to peripheral lymph nodes, mesenteric lymph nodes, and Peyer's patches. In contrast, febrile temperatures did not increase LFA-1 function as assessed by measuring lymphocyte adhesion to ICAM-1-3T3 transfectants. Fever-range hyperthermia further did not increase L-selectin surface density on lymphocytes or L-selectin-dependent recognition of soluble carbohydrate substrates; however, a marked increase in ultrastructural immunogold-labeling of L-selectin was observed in response to thermal stimuli. These results suggest that elevated temperatures enhance L-selectin adhesion and/or avidity through the regulation of L-selectin conformation or organization in the plasma membrane. Finally, the observed thermal effects on L-selectin adhesion were attributed to soluble factors in the conditioned medium of heat-treated cells. Taken together, these data provide new insight into the potential physiologic role of the febrile response in enhancing lymphocyte recruitment to tissues through the regulation of L-selectin adhesion.  相似文献   
945.
EA Bakalakos  JA Kim  DC Young  EW Martin 《Canadian Metallurgical Quarterly》1998,22(4):399-404; discussion 404-5
Hepatic resection remains the only potentially curative treatment for metastatic colorectal cancer. This retrospective review study was undertaken in an attempt to identify factors that influence patient survival following hepatic resection for metastatic colorectal cancer. From January 1978 to December 1993, a total of 301 patients underwent a total of 345 planned hepatic resections for metastatic colorectal cancer. Of those, 245 patients had one resection, 44 had two resections, and 12 had three resections. For all patients the overall median survival was 20.6 months, operative mortality was 1.1%, and overall morbidity was 17.2%. Average hospital stay was 9 days. Statistical analysis included univariate analysis using log rank comparisons, Kaplan-Meier survival curves, and multivariate analysis using Cox proportional hazards regression. The statistically significant factors that influenced survival were distribution of liver metastases, unilobar versus bilobar (p = 0.0001), resected versus nonresected (p < 0.0001), and tumor-free surgical margins versus positive margins (p = 0.001). Surprisingly, the disease-free interval and the original stage of the primary tumor did not predict survival (p = not significant). Other factors that had no influence on survival were type of resection, size and number of liver metastases, ABO blood group, and the number of perioperative blood transfusions. For those patients who underwent resection of unilobar metastases with tumor-free margins, the 5-year survival rate was 29% with a median survival of 35 months and eight survivors > 7 years. In addition, one patient with bilobar disease had survival > 7 years and five patients who had resection of hepatic metastases and extrahepatic cancer simultaneously had survival > 3 years. Our data support the concept that patients with unilobar metastatic disease who undergo surgical resection with tumor-free surgical margins can be afforded a significant opportunity at long-term survival with acceptable morbidity, mortality, and hospital stay. Also, certain patients with bilobar or extrahepatic disease (or both) who undergo complete resection can enjoy a long-term survival. In these subgroups of patients resection should be considered on an individual basis.  相似文献   
946.
947.
To decrease incisional pain, morbidity, and length of hospital stay (LOS) and, hopefully, to reduce costs, most surgical specialties have turned to minimally invasive procedures to access the body cavities during commonly performed operations. Video-assisted thoracic surgery (VATS) has emerged as the standard approach for a number of diagnostic and therapeutic procedures in thoracic surgery. Major lung resections (lobectomy, bilobectomy, and pneumonectomy), however, can be performed through an incision similar in size to the utility or access thoracotomy used in VATS to remove the specimen. The purpose of this study was to compare an oblique muscle-sparing minithoracotomy with intercostal nerve cryoanalgesia with the standard posterolateral thoracotomy incision and VATS to perform major lung resections. Forty consecutive patients with bronchogenic carcinoma, operated on by a single surgeon, were chronologically divided into two groups, each with equivalent age, sex distribution, physiologic parameters, tumor size, and clinical stage. In addition, data were collected from a MEDLINE search of all published studies in which major lung resections were performed via VATS. The first group (group A, n = 20) underwent posterolateral thoracotomy to access the chest cavity, whereas the patients in the second group (group B, n = 20) underwent oblique minithoracotomy with intercostal nerve cryoanalgesia. Group B compared favorably with group A in LOS (P = 0.002), narcotic requirements (P = 0.001), morbidity (P = 0.042), and cost (P = 0.058). Group B also compared favorably with VATS major lung resection published data regarding LOS and morbidity.  相似文献   
948.
PURPOSE: To examine families ascertained for late-onset primary open-angle glaucoma (POAG) to determine mutations in the gene coding for myocilin. METHODS: The diagnosis of late-onset POAG was defined as age at diagnosis more than 35 years, intraocular pressure (IOP) 22 mm Hg or more in both eyes or 19 mm Hg or more while the patient was taking two glaucoma medications, glaucomatous optic neuropathy in both eyes, and visual field loss consistent with optic nerve damage in at least one eye of the proband. Two of three criteria were required in other family members. DNA from all families was screened for polymorphisms in myocilin using single-strand conformation polymorphism analysis. All polymorphisms were sequenced for mutations. RESULTS: Eighty-three affected people in 29 families with late-onset POAG were screened for mutations. Three mutations, two novel missense (Thr377Met and Glu352Lys) and one nonsense (Gln368STOP), were identified. The missense mutations did not segregate with the disease phenotype in these families. The nonsense mutation was found in 3 of 29 unrelated families with POAG. All affected family members and 8 of 12 in whom glaucoma was suspected had the Gln368STOP mutation. All people with this mutation had elevated IOP, and 78% had POAG by age 70. CONCLUSIONS: Three mutations were identified in the gene coding for myocilin in families with late-onset POAG. Of these, the Gln368STOP mutation was highly associated with the development of glaucoma. All people with this mutation had glaucoma or elevated IOP by age 70. In the United States, the Gln368STOP mutation in myocilin is strongly associated with the development of late-onset POAG. However, factors in addition to the presence of this mutation seem to play a role in the development of ocular hypertension and glaucoma in these families.  相似文献   
949.
The mechanisms by which inulin may elicit its lipid-lowering effect are not well elucidated. To examine the lipid-lowering potential of inulin and especially its effect on bile acid metabolism, male golden Syrian hamsters were fed semipurified diets containing 20 g/100 g fat, 0.12 g/100 g cholesterol and 0 (control), 8, 12 or 16% inulin for 5 wk. Plasma total cholesterol concentrations were significantly lowered by 18, 15 and 29% in hamsters fed 8, 12 and 16% inulin, respectively. Dietary inulin specifically decreased VLDL cholesterol, which was significantly lower in hamsters fed 16% inulin compared with controls (1.1 +/- 0.3 vs. 2.9 +/- 0.6 mmol/L). LDL and HDL cholesterol were not significantly affected by dietary inulin. Plasma triacylglycerol was significantly reduced by 40 and 63% in hamsters fed 12 and 16% inulin, respectively. Hepatic total cholesterol and particularly esterified cholesterol accumulation were significantly lower in hamsters fed 8% inulin compared with controls. All three levels of dietary inulin caused distinct alterations in the bile acid profile of gallbladder bile. Taurochenodeoxycholic acid was significantly lower, whereas glycocholic and glycodeoxycholic acid were greater in hamsters fed inulin. Daily fecal bile acid excretion (micromol/d) tended to be greater (P = 0.056) in inulin-fed hamsters compared with controls, whereas daily neutral sterol excretion was not affected. These data demonstrate that the lipid-lowering action of inulin is possibly due to several mechanisms, including altered hepatic triacylglycerol synthesis and VLDL secretion and impaired reabsorption of circulating bile acids.  相似文献   
950.
The basal ganglia are an interconnected set of subcortical regions whose established role in cognition and motor control remains poorly understood. An important nucleus within the basal ganglia, the striatum, receives cortical afferents that convey sensorimotor, limbic and cognitive information. The activity of medium-sized spiny neurons in the striatum seems to depend on convergent input within these information channels. To determine the degree of correlated input, both below and at threshold for the generation of action potentials, we recorded intracellularly from pairs of spiny neurons in vivo. Here we report that the transitions between depolarized and hyperpolarized states were highly correlated among neurons. Within individual depolarized states, some significant synchronous fluctuations in membrane potential occurred, but action potentials were not synchronized. Therefore, although the mean afferent signal across fibres is highly correlated among striatal neurons, the moment-to-moment variations around the mean, which determine the timing of action potentials, are not. We propose that the precisely timed, synchronous component of the membrane potential signals activation of cell assemblies and enables firing to occur. The asynchronous component, with low redundancy, determines the fine temporal pattern of spikes.  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