全文获取类型
收费全文 | 2819篇 |
免费 | 15篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 2篇 |
综合类 | 6篇 |
化学工业 | 20篇 |
机械仪表 | 6篇 |
建筑科学 | 8篇 |
能源动力 | 16篇 |
轻工业 | 29篇 |
水利工程 | 1篇 |
无线电 | 15篇 |
一般工业技术 | 38篇 |
冶金工业 | 2679篇 |
原子能技术 | 2篇 |
自动化技术 | 13篇 |
出版年
2023年 | 7篇 |
2022年 | 5篇 |
2021年 | 11篇 |
2020年 | 8篇 |
2019年 | 7篇 |
2018年 | 9篇 |
2017年 | 5篇 |
2016年 | 4篇 |
2015年 | 2篇 |
2014年 | 7篇 |
2013年 | 11篇 |
2011年 | 7篇 |
2010年 | 4篇 |
2009年 | 4篇 |
2008年 | 5篇 |
2007年 | 5篇 |
2006年 | 4篇 |
2005年 | 3篇 |
2004年 | 10篇 |
2003年 | 11篇 |
2002年 | 1篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 107篇 |
1998年 | 876篇 |
1997年 | 499篇 |
1996年 | 333篇 |
1995年 | 168篇 |
1994年 | 139篇 |
1993年 | 180篇 |
1992年 | 12篇 |
1991年 | 22篇 |
1990年 | 28篇 |
1989年 | 32篇 |
1988年 | 18篇 |
1987年 | 22篇 |
1986年 | 21篇 |
1985年 | 27篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 14篇 |
1981年 | 8篇 |
1980年 | 29篇 |
1979年 | 1篇 |
1978年 | 5篇 |
1977年 | 49篇 |
1976年 | 100篇 |
1975年 | 2篇 |
1973年 | 2篇 |
1970年 | 1篇 |
排序方式: 共有2835条查询结果,搜索用时 0 毫秒
101.
102.
Carcinoid syndrome, although rare, can create serious problems to the anesthetist, both by the nature and variability of clinical manifestations and by the complications that can occur peroperatively. Recent research has led to a better understanding of the pathophysiology of the disease process. However, modern medicine is far from unraveling the precise nature and physiological effects of all the peptide mediators produced by these tumors. The severity of symptoms does not predict the severity of perioperative complications, so that patients with minor preoperative symptoms may have significant intraoperative complications. While urinary 5-HIAA levels provide a good indicator of disease progression, they cannot predict the degree or type of physiological response to intraoperative tumor manipulation. Indeed, urinary 5-HIAA may be normal both in the presence of a clinical diagnosis of carcinoid syndrome and in the face of a peroperative carcinoid crisis. The keys to successful anesthetic management of patients with carcinoid syndrome are good communication between endocrinologist, anesthetist, and surgeon and preoperative optimization of the patient. This includes appropriate investigation and treatment of the effects of carcinoid peptides and the prevention of their release from tumors. If possible, advice should be sought from centers with experience at managing this group of patients. Octreotide has largely replaced the use of other drugs both for symptomatic control and acute treatment of the symptoms associated with carcinoid syndrome. However, other drugs, such as aprotinin, still have a significant place in the symptomatic control and treatment of peroperative complications, as serotonin is only one of a large variety of peptides responsible for the clinical effects of this disease. Anesthetic technique should be aimed at minimizing carcinoid mediator release, in response to stress it induction of anesthesia and tracheal intubation and during tumor manipulation. It is equally important to prepare for carcinoid crisis by, for example, ordering drugs, which are otherwise uncommonly used in the theater setting, ahead of time. Cardiovascular instability, particularly hypotension, is common, so that full monitoring and vigilance is vital to predict its onset. The current surgical view of management is that, while curative resection of carcinoid tumors less than 2 cm in diameter with no evidence of invasion or metastatic spread is appropriate, patients with disseminated disease should be medically managed unless symptom control is poor. The exceptions to this are those patients with early and correctable carcinoid cardiac disease and those who require palliative procedures such as defunctioning obstructed bowel. Survival rates in patients following excision of gastric and appendical carcinoid tumors approach those of the general population as a whole and the chance of metastasis is extremely low. Only two series have been published in the anesthetic literature on anesthesia for patients with carcinoid syndrome, although there are many single-case reports. Despite the rarity of this syndrome, further formal studies into the anesthetic management of this condition should be encouraged. 相似文献
103.
104.
We investigated the nature of the effects of memory associations on alcohol use and abuse. First, we determined if effects of memory associations on drinking problems are mediated entirely through the frequency of alcohol consumption or, alternatively, if such effects are more direct. Second, personality traits were assessed to evaluate whether they were confounded with memory association in their effects or whether they might moderate the effects of memory associations on alcohol use and abuse. The results showed that memory association measures directly and independently predicted alcohol consumption; these measures indirectly predicted problems from drinking, including drunk driving. None of the assessed personality variables moderated the predictive effects of memory association. The results are consistent with the view that memory associations influence behavior through cognitive processes that are not affected by personality traits or by cognitions emanating from such traits. 相似文献
105.
MD Schechter 《Canadian Metallurgical Quarterly》1998,341(2-3):131-134
Tonsils have a privileged situation in the immune system in that they are in touch with the environment. Melatonin is a hormone that is influenced by the circadian environmental variations of dark-light and is a modulator of the immune system. We have studied a group of thirty five children with recurrent acute tonsillitis that were submitted for tonsillectomy. Tonsillar lymphocyte subsets were determined before and after culture through flow cytometry in a tonsillar mononuclear suspension. After the culture, the lymphocyte subsets of type B suffered a decrease that was restored in the presence of melatonin or phytohemaglutinin, and even increased above the values of the control when the culture was accomplished in the presence of both substances. This process was specific for B cells, no occurrence for T lymphocytes or natural killer cells. Melatonin is found in the crossroads of the interaction of the microorganisms, pollens or inert substances with the tonsillar lymphocytes in the production of the immune defences. Further study is required on tonsillar pathology to explain its physiopathology and its possible therapeutic role. 相似文献
106.
We studied the effect of the nitric oxide synthase (NOS) inhibitor asymmetric dimethyl arginine (ADMA) and the inactive enantiomer N G-methyl-D-arginine (D-NMMA) on Pseudomonas aeruginosa infection of the respiratory mucosa in nasal turbinate organ cultures. We also investigated the effect of P. aeruginosa culture filtrate on the expression of inducible NOS (iNOS) messenger RNA (mRNA) by an epithelial cell line (A549). Organ cultures were preincubated with ADMA (0.1 to 4 x 10(-4) M) or D-NMMA (2 x 10(-4) M) for 30 min prior to bacterial infection. Infected organ cultures (8 h) had significantly (P <= 0.05) greater epithelial damage and fewer ciliated and unciliated cells than did control cultures. There was an increased level of nitrite in the medium feeding infected organ cultures as compared with control cultures. ADMA significantly (P <= 0.05) reduced both bacterially induced epithelial damage and loss of ciliated cells in a concentration-dependent manner. D-NMMA did not influence the effect of P. aeruginosa infection of the mucosa. ADMA, but not D-NMMA, significantly (P <= 0.04) reduced total bacterial numbers adherent to the respiratory mucosa. P. aeruginosa culture filtrates (24 h and 36 h) significantly (P = 0.02) increased iNOS with respect to glyceraldehyde-3-phosphate dehydrogenase mRNA expression. These results show that P. aeruginosa stimulates iNOS expression by a cell line and NO production by an organ culture. ADMA reduces mucosal damage and loss of ciliated cells, which suggests that NO may be a mediator of epithelial damage caused by P. aeruginosa. 相似文献
107.
OBJECTIVES: This ecologic study assessed whether there was a change in health status in Alaska in the winter of 1992-93 after the introduction of MTBE in gasoline. Methyl tertiary butyl ether(MTBE) is used as a fuel oxygenate in the United States and in Europe. In the winter of 1992-93 MTBE was added to gasoline in the cities of Fairbanks and Anchorage, Alaska. The program was discontinued in Fairbanks in December, 1992, but continued in Anchorage until February 28, 1993. METHODS: Outpatient visits for state employees and dependents (n = approximately 28,000) living in Alaska were compared over three winters by analyzing health insurance claims. RESULTS: Odds ratios were calculated. The odds ratios indicated that the winter of 92-93 was not statistically different from previous winters in numbers of claims for upper respiratory illness, bronchitis, headache, or asthma in either Anchorage or Fairbanks. CONCLUSION: There was no increase in claims for respiratory illness in either city after introduction of MTBE. 相似文献
108.
MD Murray 《Canadian Metallurgical Quarterly》1995,46(1-3):91-99
The use of a model to appraise arboviral epizootics is described, and examples are given which demonstrated long-distance wind-dispersal of the biting-midge vector Culicoides brevitarsis from the same endemic source. Vector abundance is characterised by peaks and troughs of abundance, the patterns of which vary between localities and annually. Short term climatic effects can change rapidly the age structure of a population, thus increasing the number of midges that can transmit a virus and profoundly influencing the probabilities of viral transmission. The population dynamics of vector and viral foci are complex, if not chaotic. 相似文献
109.
The age-related induction of inducible nitric synthase (iNOS) and apoptotic cell death in spiral ganglion cells (SGCs) of ddy strain mice were studied with immunohistochemical method and TdT-mediated dUTP-biotin nick end labeling (TUNEL), respectively. A large amount of iNOS was expressed in SGCs of 18- to 24-month-old mice, but not in those of the mice less than 12 months of age. Moreover, these mice were accompanied by a great rise in auditory brainstem response threshold as well as a great decrease in the number of SGCs that seemed to be due to preceding cell death of the cells. However, we were unable to find apoptotic TUNEL-positive cells in the spiral ganglions. This was assumed to be due to a very short clearance time of the dead cell bodies of less than one hour. As has been known, NO produced by iNOS can implicate in causes for either protection of cells from peroxidation and cell death. In the present study, therefore, the steep augmentation of iNOS in the SGCs of senescent mice implies that the iNOS initially induced to protect SGCs from the cytotoxicity of cellular peroxidation eventually contribute to the cell death of SGCs themselves. 相似文献
110.
I Chacartegui Martínez C Delgado Jiménez MD Ruiz Fernández 《Canadian Metallurgical Quarterly》1997,20(226):65-70
INTRODUCTION: This study looks at the degree of satisfaction colostomy patients feel in regards to their perception of the health care that they receive, whether they think that their physicians care could improve and the level of the medical staffs professional experience. METHOD AND MATERIAL: The study was performed in the Area Hospitalaria de Valme (Sevilla). With a population of 350,000 possible patients of which 215 have an ostomy, 55 of these took part in the study. 215 questionnaires were mailed to the ostomy patients with paid return mail enclosed. The survey was based on Lickerts attitude scale and had six items to respond to, using an evaluation of zero to five. This method is sufficiently valid and has been used in other studies such as project CORCH. RESULTS: First, averages were obtained for all items and variables. Second, a patient profile was obtained regarding sex and age. Third, a correlation of the three study variables was compared against variables of a global index of satisfaction. DISCUSSION: In contrast with the global index, the satisfaction of the patients in the study is very high (3.93 out of a possible 5). 45% of these patients perceive that the medical treatment that they receive could improve but that the professional experience of the medical staff is acceptable (62%). 相似文献