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   1322篇
  免费   5篇
电工技术   1篇
化学工业   23篇
金属工艺   2篇
机械仪表   7篇
建筑科学   2篇
矿业工程   1篇
能源动力   3篇
轻工业   11篇
水利工程   4篇
石油天然气   3篇
无线电   57篇
一般工业技术   23篇
冶金工业   1156篇
自动化技术   34篇
  2023年   1篇
  2020年   5篇
  2019年   2篇
  2018年   2篇
  2017年   2篇
  2016年   2篇
  2015年   5篇
  2013年   10篇
  2012年   1篇
  2011年   12篇
  2010年   3篇
  2009年   9篇
  2008年   13篇
  2007年   10篇
  2006年   13篇
  2005年   8篇
  2004年   6篇
  2003年   12篇
  2002年   9篇
  2001年   2篇
  2000年   5篇
  1999年   39篇
  1998年   347篇
  1997年   224篇
  1996年   127篇
  1995年   57篇
  1994年   54篇
  1993年   55篇
  1992年   15篇
  1991年   18篇
  1990年   18篇
  1989年   23篇
  1988年   16篇
  1987年   17篇
  1986年   17篇
  1985年   18篇
  1984年   1篇
  1983年   1篇
  1982年   7篇
  1981年   11篇
  1980年   14篇
  1979年   3篇
  1978年   8篇
  1977年   25篇
  1976年   71篇
  1975年   4篇
  1974年   2篇
  1972年   1篇
  1967年   1篇
  1954年   1篇
排序方式: 共有1327条查询结果,搜索用时 0 毫秒
121.
122.
123.
This paper uses definitions of a consensus conference (ACCP/CCM) describing the epidemiology of SIRS, sepsis and septic shock in surgical ICU patients. During a period of 2 years a total of 656 patients were prospectively enrolled into the study. 335 patients (51.1% of the total population) developed SIRS (systemic inflammatory response syndrome); in 65 of these patients infection could be documented, i.e. they met the criteria of sepsis, 47 of these 65 septic patients developed septic shock, with mortality of 53.2%. SIRS is associated with a high sensitivity but a low specificity in predicting the outcome of ICU patients. Moreover, SIRS and sepsis appear to be of minor clinical relevance. On the contrary, septic shock describes a very high risk group of patients which should be characterized more closely in future studies.  相似文献   
124.
Recent animal experiments have shown that palatal repair without denudation of bone leads to a superior dento-alveolar development. The aim of this clinical study was to evaluate the peri- and postoperative course and the dento-alveolar development of the deciduous dentition in Japanese ULCP, and CP patients up to 5 years after two different types of palatal repair. One of the methods, the Kohama (1991) supraperiosteal flap technique, is performed without denudation of the bony palate, while the other, the Wardill (1937) push-back technique, results in areas of denuded bone. It was concluded that the supraperiosteal technique can be performed successfully in approximately the same amount of time as the push-back technique. Re-epithelialization of the wound areas after supraperiosteal repair takes about 1 week, which is one third of the time associated with healing after the push-back technique. Arch depth of the deciduous dentition after the supraperiosteal technique is superior compared to the push-back technique. The question of whether or not the supraperiosteal technique produces more favorable dento-alveolar development than the mucoperiosteal technique in the permanent dentition in humans has to be elucidated in future research.  相似文献   
125.
PURPOSE: Patients with primary cutaneous melanoma with a Breslow thickness > or = 1.5 mm have only a 30% to 70% probability of survival after surgery, and no adjuvant therapy has so far improved this outcome. Since interferon alfa-2a (IFNalpha2a) exhibits antitumor activity in metastatic melanoma, we investigated whether adjuvant IFNalpha2a diminishes the occurrence of metastases and thus prolongs disease-free survival in melanoma patients after excision of the primary tumor. PATIENTS AND METHODS: In a prospective randomized study, 311 melanoma patients with a Breslow thickness > or = 1.5 mm were assigned to either adjuvant IFNalpha2a treatment (n = 154) or observation (n = 157) after excision of the primary tumor. IFNalpha2a was given daily at a dose of 3 mIU subcutaneously (s.c.) for 3 weeks (induction phase), after which a dose of 3 mIU s.c. three times per week was given over 1 year (maintenance phase). RESULTS: Prolonged disease-free survival was observed in patients treated with IFNalpha2a versus those who underwent surgery alone. This difference was significant (P = .02) for all patients enrolled onto the study (intention-to-treat analysis) at a mean observation time of 41 months. Subgroup analysis showed that Breslow tumor thickness had no influence on treatment results in the groups of patients investigated. CONCLUSION: Adjuvant IFNalpha2a treatment diminishes the occurrence of metastases and thus prolongs disease-free survival in resected primary stage II cutaneous melanoma patients.  相似文献   
126.
The gfi-1 gene encodes a zinc finger containing protein that is specifically expressed in T-lymphocytes and is a frequent target of proviral insertion in T-cell lymphoma provoked by infection with MoMuLV--a non acute transforming retrovirus. Expression of a gfi-1 transgene targeted to T-cells by the lck proximal promoter provokes a reduction of peripheral CD4 and CD8 positive T-cells but nevertheless weakly predisposes transgenic animals for the development of T-cell lymphoma. Forced coexpression of the serine/threonine kinase Pim-1 can partially restore normal T-cell numbers in double pim-1/gfi-1 transgenic mice. Moreover, the combinatorial expression of Pim-1 and Gfi-1 leads to accelerated development of T-cell lymphoma with a mean latency period of 114 days. A similar accelerated rate of lymphoma development was observed when lck-gfi-1 mice were crossed with mice that carry a L-myc gene targeted to be expressed at high levels in T-cells. The results show that gfi-1 can act with low activity as a dominant oncogene when overexpressed but also demonstrate that it is most efficient only in the presence of a cooperative partner protein as for example Pim-1 or L-Myc. In addition, the results suggest that Pim-1 and Gfi-1 are acting synergistically in both T-cell lymphomagenesis and T-cell development.  相似文献   
127.
Serum concentrations of thyroxine (T4), triiodothyronine (T3), and thyrotropine were measured in 34 patients with nonseasonal affective disorders before and after 1 week of light treatment. Nineteen of these patients received bright white light (2500 lx) and 15 dim red light (50 lx) for 2 hours daily in the mornings over a 1-week period. Slight but significant reductions in the rating scores for the depressive symptomatology were found for both the bright-and dim-light groups, but there were no significant differences between the two groups. The improvement is thus most likely a placebo effect. Surprisingly, the small changes in the severity of the depressive symptoms in the group as a whole were significantly correlated to the changes in the serum levels of T4 during the weeks of bright- and dim-light treatment, respectively. The more a patient improved, the further his or her T4 level fell and vice versa. The fluctuations in the concentrations of T4 during light treatment were significantly greater in the depressed patients than in a group of 12 healthy controls who also received bright or dim light, whereas the changes in T3 were significantly smaller than those of the healthy controls. The pronounced fluctuations in T4 levels were probably not secondary to changes in mood. Rather, they are likely to reflect changes in tissue (intracellular) metabolism of T4, which may be involved in the mechanisms underlying the fluctuations in mood in these patients.  相似文献   
128.
The endothelium, lining the inner surface of blood vessels, can be considered as the main local regulator of vascular wall homeostasis. It secretes various factors in response to mechanical and hormonal stimuli, which, in turn, influence smooth muscle cell contractility, vascular structure, blood fluidity, and other cell-to-cell interactions. Within the same species, there are, however, variations in endothelial cell function, depending not only on the vascular bed of origin, but also on the size of the vessel within the same vascular territory. Differences have been observed in phenotype, antigen expression, cell size and growth, secretory function, and G-protein expression. Furthermore, some pathological processes affect endothelial function selectively; that is, some vascular beds are sensitive to atherosclerosis while others are not. Understanding these distinctions is particularly important for a rational approach to the treatment of vascular disorders.  相似文献   
129.
OBJECTIVE: The purpose of this study was to review the radiologic manifestations of the hepatopulmonary syndrome. MATERIALS AND METHODS: We retrospectively reviewed clinical records, chest radiographs, 99m Tc-macroaggregated albumin (MAA) perfusion lung scans, chest CT scans, and pulmonary angiograms of 10 patients with proven hepatopulmonary syndrome. RESULTS: Chest radiographs showed basilar, medium-sized (1.5-3.0 mm) nodular or reticulonodular opacities in all cases. CT was done in eight cases and showed basilar dilatation of lung vessels with a larger than normal number of visible branches. The vascular basis for these opacities was best appreciated on conventional CT scans of 10-mm sections. No individual arteriovenous malformations were seen on CT scans. High-resolution CT scans showed no evidence of interstitial fibrosis. 99mTc-MAA perfusion lung imaging, done in seven patients, showed pulmonary arteriovenous shunting in five. Contrast echocardiography confirmed intrapulmonary shunting in these five patients. Pulmonary angiography, done in four cases, showed subtle distal vascular dilatation in two and moderate dilatation with early venous filling in two but did not reveal any individual arteriovenous malformations. CONCLUSION: Chest radiographs in hepatopulmonary syndrome usually show bibasilar nodular or reticulonodular opacities. Conventional CT shows that these opacities represent dilated lung vessels. High-resolution CT is useful in excluding pulmonary fibrosis or emphysema as the cause of these opacities. 99mTc-MMA perfusion imaging or contrast echocardiography can be used to confirm intrapulmonary arteriovenous shunting.  相似文献   
130.
TF Lüscher  G Noll 《Canadian Metallurgical Quarterly》1996,14(2):S111-9; discussion S119-21
SURROGATE END-POINTS: Pharmacotherapy of cardiovascular disease has been increasingly validated in large interventional trials to assess its efficacy, safety and costs. As endpoints, morbidity and mortality are evaluated. More recently, surrogate end-points have been included in interventional trials, both to increase our understanding of pathogenic mechanisms and for their potential use as markers of risk in patients. ENDOTHELIAL FUNCTION: The endothelium lies in a strategic anatomical position between the circulating blood and vascular smooth muscle and hence is a major local mediator of cardiovascular function. Also, endothelial cells are a target for mechanical forces and cardiovascular risk factors in the circulation. Thus, it is not surprising that their function becomes impaired at an early stage in the disease process. The cells are able to produce numerous proteins and mediators. This review focuses on nitric oxide and endothelin-1, which are endothelium-derived relaxing and constrictor factors, respectively. Nitric oxide also prevents platelet adhesion and aggregation and the adhesion of monocytes. Both substances also affect vascular structure in that nitric oxide inhibits while endothelin stimulates vascular smooth muscle proliferation and migration. MEASUREMENTS OF ENDOTHELIAL FUNCTION: Endothelial function and the effects of nitric oxide and endothelin in particular can be evaluated in the coronary circulation by quantitative coronary angiography and Doppler flow wire, and in the peripheral circulation with plethysmography and new ultrasound/Doppler devices. In these experimental set-ups, lipid-lowering drugs and angiotensin converting enzyme (ACE) inhibitors have been evaluated. Lipid-lowering drugs improve endothelium-dependent vasodilation in the coronary and forearm circulation of patients with hyperlipidemia and atherosclerosis. Similarly, ACE inhibitors improve coronary vasomotion in patients with coronary artery disease and normal lipid levels. In hypertension, ACE inhibitors have failed to improve endothelium-dependent vasodilation, while studies with other drugs are planned. CONCLUSIONS: Endothelial function can now be assessed precisely in patients in vivo, in both the coronary and the peripheral circulation. Tests can detect early dysfunction in patients with a risk of cardiovascular disease and the possible effects of drugs on endothelial function. Large interventional trials are needed to establish how far endothelial dysfunction can or cannot predict clinical outcome.  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