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   907篇
  免费   0篇
电工技术   1篇
化学工业   5篇
机械仪表   1篇
轻工业   3篇
无线电   2篇
一般工业技术   4篇
冶金工业   891篇
  2016年   1篇
  2011年   1篇
  2010年   2篇
  2009年   1篇
  2008年   1篇
  2007年   1篇
  2006年   1篇
  2005年   3篇
  2003年   4篇
  2000年   2篇
  1999年   36篇
  1998年   306篇
  1997年   186篇
  1996年   89篇
  1995年   59篇
  1994年   37篇
  1993年   62篇
  1992年   6篇
  1991年   8篇
  1990年   4篇
  1989年   4篇
  1988年   9篇
  1987年   3篇
  1986年   3篇
  1985年   5篇
  1983年   1篇
  1982年   5篇
  1981年   4篇
  1980年   3篇
  1978年   3篇
  1977年   15篇
  1976年   40篇
  1975年   1篇
  1955年   1篇
排序方式: 共有907条查询结果,搜索用时 0 毫秒
131.
Epstein-Barr virus (EBV) is associated with the development of several B cell malignancies including Burkitt's lymphoma (BL), post-transplant lymphoproliferative disease (PTLD), and AIDS-related lymphomas. The latter two diseases result from EBV-driven B cell proliferation in the absence of normal immunosurveillance and as such, represent a heterogenous family of lymphoproliferative disorders. This article reviews studies on EBV gene expression and antibody development in PTLD and introduces recent information on the levels of EBV+ peripheral blood lymphocytes to discuss possible mechanisms of pathogenesis under varying conditions of immunosuppression.  相似文献   
132.
Ion beam enhanced deposition (IBED) was adopted to synthesize biocompatible titanium oxide film. Structure characteristics of titanium oxide film were investigated by RBS, AES, and XRD. The blood compatibility of the titanium oxide film was studied by measurements of blood clotting time and platelet adhesion. The results show that the anticoagulation property of titanium oxide film is improved significantly. The mechanism of anticoagulation of the titanium oxide film was discussed.  相似文献   
133.
This article reviews the determinants of myocardial oxygen supply (MVO2) and consumption and revisits the effects of IABC on each. Measurements of MVO2, including diastolic pressure-time index (DPTI), tension-time index (TTI), and endocardial viability ratios (EVR), demonstrate the dramatic effects of balloon deflation and the resulting afterload reduction on MVO2. IABC enhances ventricular outflow, thus decreasing preload; reduces systolic and end-diastolic aortic pressures, causing a decrease in ventricular afterload; magnifies the intrinsic Windkessel effect in the aorta, leading to an increased stroke volume; decreases static work and accordingly, MVO2; and stimulates the baroreceptors, causing a reduction in peripheral vascular resistance. IABC also increase in heart rate. Bedside computers enable the clinician to take a closer look at balloon efficacy via DPTI, TTI, and EVR. New sources of information and understanding may provide opportunities for nurses to ensure optimum patient outcomes.  相似文献   
134.
Tumor cells from eight adult patients with T-cell chronic malignancies were investigated with a series of monoclonal antibodies recognizing T-cell differentiation antigens. This series allowed definition of discrete subpopulations of mature T cells with functional specialization. All six patients with Sézary syndrome and one patient with T-chronic lymphocytic leukemia had cells with the same phenotype as normal helper/inducer T cells, whereas the other patient with T-chronic lymphocytic leukemia had cell with the same phenotype as normal cytotoxic/suppressor T cells. Some clinical manifestations observed in these patients may reflect retention of functional activities by their malignant cells.  相似文献   
135.
Using a rat lung model, we sought to characterize the time course for ischemia-reperfusion injury and the role of neutrophils in the development of injury. Adult male Long-Evans rats underwent left thoracotomy with dissection and clamping of the left pulmonary artery, bronchus, and vein for 90 min, resulting in complete left lung ischemia. The lungs were then ventilated and reperfused for up to 4 hr. Time-matched sham animals underwent the identical thoracotomy and hilar dissection, but the lungs were not rendered ischemic. Using vascular permeability of 125I-labeled bovine serum albumin as a measure of reperfusion injury, a bimodal pattern of injury was observed. Compared to sham controls, animals undergoing ischemia-reperfusion demonstrated a significant early phase of lung injury at 30 min of reperfusion (P < 0.0001), followed by partial recovery. A second peak of lung injury was noted after 4 hr of reperfusion (P < 0.001). Myeloperoxidase activity in reperfused lung tissue, a measure of neutrophil sequestration, increased during the reperfusion time course. To determine the role of neutrophils in the development of lung reperfusion injury, additional animals undergoing the identical ischemia-reperfusion protocol received either rabbit anti-rat neutrophil serum or preimmune serum the day prior to operation. Profound neutropenia (< 75/mm3 blood) was confirmed by differential leukocyte counts. Neutropenia had no protective effect against microvascular permeability at 30 min of reperfusion, but there was a significant reduction in lung injury at 4 hr (P < 0.005). We conclude that, during lung ischemia-reperfusion, there is a bimodal pattern of injury, consisting of both neutrophil-independent and neutrophil-mediated events.  相似文献   
136.
In this paper the DNA damage and repair induced by the radiomimetic agent bleomycin are compared in murine Friend erythroleukaemia wild-type 707 cells and a thymidine kinase-deficient sub-clone BUF. Comparisons are made using results obtained from the alkaline comet assay and unscheduled DNA synthesis experiments. Further analysis to determine the fidelity of bleomycin-induced repair as indicated by mutagenesis to hypoxanthine-phosphoribosyltransferase deficiency was also conducted. Similar sensitivities to bleomycin treatments were observed in the two cell types with the comet assay, while similar levels of dose-dependent excision repair following bleomycin treatments were also detected in unscheduled DNA synthesis experiments. Comet assay and unscheduled DNA synthesis experimental results are in agreement. Survival and induced hypoxanthine-phosphoribosyltransferase mutant frequencies were observed to be unaffected by a thymidine kinase-deficiency in Friend erythroleukaemia cells. The results of this investigation suggest no overall difference in the repair capacities or the repair fidelity of Friend 707 relative to BUF cells following bleomycin treatments.  相似文献   
137.
Maze performance and morphology of frontal cortex were assessed in young adult, middle-aged, and aged rats with and without lesions of the nucleus basalis magnocellularis. Although maze performance did not vary with age, neuron number and the thickness of superficial laminae were reduced in aged rats. Lamina II-III neurons were hypertrophied in middle-aged rats relative to both younger and older groups. At all ages, lesions significantly impaired maze performance. In young adult rats, lesions moderately reduced the size of lamina II-III neurons. This effect was more pronounced in middle-aged rats. Lesions in aged rats did not affect neuron size. The neuronal changes seen in middle-aged rats may reflect a compensatory response to the expression of other age-related neuronal changes, which may affect the ability of cortical neurons to respond to lesion-induced loss of cholinergic input.  相似文献   
138.
Growing public awareness of environmental hazards has led to an increased demand for public health authorities to investigate geographical clustering of diseases. Although such cluster analysis is nearly always ineffective in identifying causes of disease, it often has to be used to address public concern about environmental hazards. Interpreting the resulting data is not straightforward, however, and this paper presents a guide for the non-specialist. The pitfalls include the fact that cluster analyses are usually done post hoc, and not as a result of a prior hypothesis. This is particularly true for investigations prompted by reported clusters, which have the inherent danger of overestimating the disease rate through "boundary shrinkage" of the population from which the cases are assumed to have arisen. In disease surveillance the problem of making multiple comparisons can be overcome by testing for clustering and autocorrelation. When rates of disease are illustrated in disease maps undue focus on areas where random fluctuation is greatest can be minimised by smoothing techniques. Despite the fact that cluster analyses rarely prove fruitful in identifying causation, they may-like single case reports-have the potential to generate new knowledge.  相似文献   
139.
Clinically apparent thyroid nodules occur in about 5 percent of the population. Because most patients with thyroid nodules present initially to their primary care physician, family physicians should have a thorough understanding of the diagnosis and treatment of thyroid nodules. The history and physical examination may be helpful in detecting thyroid nodules but are not useful in predicting malignancy. Furthermore, laboratory studies, ultrasonography and nuclear medicine scans do not reliably differentiate between benign and malignant thyroid nodules. In most cases, fine-needle aspiration biopsy can accurately identify malignant thyroid nodules. Fine-needle aspiration biopsy is safe and can be performed in an office setting.  相似文献   
140.
Serine 167 has been identified by radiolabel and amino acid sequencing as the major estrogen-induced phosphorylation site on the human estrogen receptor (hER) from human MCF-7 mammary carcinoma cells. The phosphorylation of the hER on serine 167 was estrogen-dependent, increasing 4-fold upon estradiol treatment of MCF-7 cells and accounted for almost half of the total [32P]phosphate incorporated into the recombinant hER from Sf9 insect cells and the native hER from MCF-7 cells. Casein kinase II was found to phosphorylate the purified recombinant hER on serine 167 in vitro. In addition, estradiol binding enhanced by 2-fold the phosphorylation of the purified recombinant hER by casein kinase II in vitro. Western blot analysis and [32P]phosphate incorporation confirmed the presence of casein kinase II in Sf9 cells. These results demonstrate that the hER is phosphorylated on serine 167 by casein kinase II in a hormone-dependent manner.  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