全文获取类型
收费全文 | 906篇 |
免费 | 9篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 2篇 |
化学工业 | 41篇 |
金属工艺 | 4篇 |
机械仪表 | 5篇 |
建筑科学 | 12篇 |
能源动力 | 7篇 |
轻工业 | 9篇 |
水利工程 | 2篇 |
石油天然气 | 1篇 |
无线电 | 26篇 |
一般工业技术 | 49篇 |
冶金工业 | 708篇 |
原子能技术 | 2篇 |
自动化技术 | 48篇 |
出版年
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 5篇 |
2018年 | 10篇 |
2017年 | 5篇 |
2016年 | 7篇 |
2015年 | 3篇 |
2014年 | 4篇 |
2013年 | 10篇 |
2012年 | 12篇 |
2011年 | 17篇 |
2010年 | 6篇 |
2009年 | 6篇 |
2008年 | 13篇 |
2007年 | 8篇 |
2006年 | 8篇 |
2005年 | 13篇 |
2004年 | 7篇 |
2003年 | 10篇 |
2002年 | 6篇 |
2001年 | 5篇 |
2000年 | 3篇 |
1999年 | 27篇 |
1998年 | 215篇 |
1997年 | 146篇 |
1996年 | 86篇 |
1995年 | 48篇 |
1994年 | 40篇 |
1993年 | 45篇 |
1992年 | 8篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1988年 | 9篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1978年 | 8篇 |
1977年 | 18篇 |
1976年 | 39篇 |
1971年 | 2篇 |
1970年 | 1篇 |
1967年 | 1篇 |
1964年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有916条查询结果,搜索用时 15 毫秒
71.
Hyun-Ah Shin Mira Park Jasvinder Paul Banga Helen Lew 《International journal of molecular sciences》2022,23(10)
Orbital fibroblasts (OFs) in thyroid-associated ophthalmopathy (TAO) are differentiated from pre-adipocytes and mature adipocytes; increased lipid and fat expansion are the major characteristics of ophthalmic manifestations. Human placental mesenchymal stem cells (hPMSCs) were reported to immunomodulate pathogenesis and suppress adipogenesis in TAO OFs. Here, we prepared transforming growth factor β (TGFβ, 20 ng/mL)-treated hPMSCs (TGFβ-hPMSCs) in order to enhance anti-adipogenic effects in vitro and in TAO mice. TAO OFs were grown in a differentiation medium and then co-cultured with hPMSCs or TGFβ-hPMSCs. TAO OFs were analyzed via quantitative real-time polymerase chain reaction, Oil red O staining, and western blotting. The results showed that TGFβ-hPMSCs reduced the expression of adipogenic, lipogenic, and fibrotic genes better than hPMSCs in TAO OFs. Moreover, the adipose area decreased more in TAO mice injected with TGFβ-hPMSCs compared to those injected with hPMSCs or a steroid. Further, TGFβ-hPMSCs inhibited inflammation as effectively as a steroid. In conclusion, TGFβ-hPMSCs suppressed adipogenesis and lipogenesis in vitro and in TAO mice, and the effects were mediated by the SMAD 2/3 pathways. Furthermore, TGFβ-hPMSCs exhibited anti-inflammatory and anti-fibrotic functions, which suggests that they could be a new and safe method to promote the anti-adipogenic function of hPMSCs to treat TAO patients. 相似文献
72.
The IEA published “Energy Technology Perspectives” (ETP) in June 2008. That document reports on IEA scenarios for baseline and low-CO2 alternative scenarios to 2050, across the energy economy. The study included creating scenarios for transport, using the IEA Mobility Model (MoMo). This paper reports on the transport-related ETP scenarios and describes the model used in the analysis. According to the ETP Baseline scenario, world transport energy use and CO2 emissions will more than double by 2050. In the most challenging scenario, called “BLUE”, transport emissions are reduced by 70% in 2050 compared to their baseline level in that year (and about 25% below their 2005 levels). There are several versions of the BLUE scenario, but all involve: a 50% or greater improvement in LDV efficiency, 30–50% improvement in efficiency of other modes (e.g. trucks, ships and aircraft), 25% substitution of liquid fossil fuels by biofuels, and considerable penetration of electric and/or fuel-cell vehicles. In the second half of this paper, an overview of the MoMo model is provided. Details on the complete analysis are contained in the ETP 2008 document, available at www.iea.org. Details of the LDV fuel economy analysis are contained in a separate paper in this collection. 相似文献
73.
KJ Greenlund WH Giles NL Keenan JB Croft ML Casper D Matson-Koffman 《Canadian Metallurgical Quarterly》1998,7(9):1125-1133
We sought to examine the prevalence of self-reported multiple cardiovascular disease (CVD) risk factors (hypertension, high blood cholesterol, diabetes, overweight, and current smoking) among women in 1992 and 1995 in the United States using data from the Behavioral Risk Factor Surveillance System. In 1992, 37.5%, 34.4%, and 28.1% of women had zero, one, and two or more of the five risk factors, respectively. In 1995, the respective estimates were 35.5%, 34.3%, and 30%. In both years, the prevalence of two or more risk factors increased with age, decreased with educational level, was higher among black women (lowest among Hispanic women and women of other ethnic groups), and higher among women reporting cost as a barrier to healthcare. The percentage of women with two or more risk factors was higher in 1995 than in 1992 for 35 of 48 states, being statistically significant for 7 states. The percentage of women with at least two risk factors was not significantly lower in 1995 than in 1992 for any state. A higher percentage of women reported having multiple CVD risk factors in 1995 compared with 1992. A multifactorial approach to primary prevention and risk factor reduction should be encouraged to help reduce the prevalence and burden of CVD among women. 相似文献
74.
75.
Kedar G. Kale Adrian J. Lew 《International journal for numerical methods in engineering》2007,70(3):291-321
This paper presents a scalable parallel variational time integration algorithm for nonlinear elastodynamics with the distinguishing feature of allowing each element in the mesh to have a possibly different time step. Furthermore, the algorithm is obtained from a discrete variational principle, and hence it is termed parallel asynchronous variational integrator (PAVI). The underlying variational structure grants it outstanding conservation properties. Based on a domain decomposition strategy, PAVI combines a careful scheduling of computations with fully asynchronous communications to provide a very efficient methodology for finite element models with even mild distributions of time step sizes. Numerical tests are shown to illustrate PAVI's performance on both slow and fast networks, showing scalability properties similar to the best parallel explicit synchronous algorithms, with lower execution time. Finally, a numerical example in which PAVI needs ≈100 times less computing than an explicit synchronous algorithm is shown. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
76.
Although numerous reports have documented that the S-nitrosylation of cysteine residues by NO alters the activities of a wide variety of proteins, the direct visualization and the structural consequences of this reversible modification have not yet been reported for any protein. Here we describe the crystal structure of S-nitroso-nitrosylhemoglobin determined at a resolution of 1.8 A. The specific reaction of NO with Cys93beta is confirmed in this structure, and a large S-nitrosylation-induced change in the tertiary structure of the COOH-terminal dipeptides of the beta subunits provides additional insight into the stereochemical mechanism by which blood flow is regulated by the interaction of NO with hemoglobin. 相似文献
77.
78.
BACKGROUND: Urticaria is a common disease that is always a challenge to the dermatologist due to its evasive etiology. PATIENTS AND METHODS: One hundred and seven chronic urticaria patients were studied. Routine laboratory investigations were performed and Helicobacter pylori (H. pylori) immunoglobulin G (IgG) antibody determinations, autoimmune reactivity, infections, allergies, and hyperreactivities were investigated. RESULTS: Pathologic findings were seen in 92 patients. Concomitant diseases suggesting autoimmune reactivity were detected in nine patients and, in 16 patients, infections including maxillary sinusitis, streptococcal tonsillitis, and tooth infection were found. Elevated total IgE level was detected in 37 out of 75 patients and positive skin prick test results in 47 out of 91 patients. Fifty-five patients had a history of recent dyspeptic symptoms. A diagnosis of adult celiac disease was made in two patients and, additionally, IgA antigliadin antibodies were seen in four patients. H. pylori IgG antibodies were found in 40 out of 107 patients. Active gastritis was verified by esophagogastroduodenoscopy in 30 out of 32 patients with positive Helicobacter staining in 24 samples. An elevated IgE level was detected in 64% of H. pylori-positive and in 39% of H. pylori-negative patients. CONCLUSIONS: In this study, several findings suggesting aberrant immunologic activation were detected in chronic urticaria patients. Inflammation in the gastrointestinal tract, e.g. caused by H. pylori infection, may have an important role in the etiology of chronic urticaria. 相似文献
79.
Viral infection and vaccination with DNA both induce similar immune responses to encoded antigens that are produced by the host. The availability of antigens in lymphoid organs is important in generating an immune response to viral challenge. Antigen availability may also be important in the response to DNA vaccines, because immune responses are stronger when antigen is secreted from DNA-transfected cells. We directed antigen to lymphoid organs by vaccination with DNA encoding antigen-ligand fusion proteins. The two ligands examined bind to receptors that are present on high endothelial venule cells of lymph nodes or on antigen-presenting cells. Here we show that both the humoral and the cellular immune responses to a model DNA vaccine were enhanced using either antigen-targeting strategy. Moreover, directing antigen to antigen-presenting cells speeded up, and altered the form of, the immune response. Directing antigen to sites of immune-response induction may represent a generic means of tailoring a potent and effective immune response to a DNA vaccine. 相似文献
80.
NL Gotteiner MJ Vonesh SE Crawford WR Burns CE Duffy VR Zales DD McPherson 《Canadian Metallurgical Quarterly》1996,15(6):596-604
BACKGROUND: Ultrasonographic tissue characterization is the assessment of physical properties of biologic tissue on the basis of quantitative analysis of its acoustic characteristics. Abnormalities in microscopic structure that occur with cardiac allograft rejection may result in characteristic alterations in myocardial acoustics. Ultrasonographic tissue characterization may allow noninvasive detection of rejection. METHODS: Findings in 22 pediatric heart transplant patients undergoing routine surveillance for rejection by endomyocardial biopsy were prospectively evaluated. Off-line ultrasonographic tissue characterization analysis was done on transthoracic echocardiograms obtained at each biopsy. Within patients, tissue characterization texture measures derived from the ultrasonographic image data were compared with histologic findings. Univariate multiple regression analysis was used to identify texture measures associated with acute allograft rejection in a subgroup (n = 8) with at least one biopsy-proven episode of moderate rejection. RESULTS: Measures of homogeneity (co-occurrence matrix correlation and heterogeneity (run-length nonuniformity) decreased with moderate rejection (p < 0.03). Homogeneity measures decreased if the patient had a previous episode of rejection. Several measures of heterogeneity (gray level difference and run-length statistics) were affected by the presence of edema. Run-length nonuniformity was the only measure that differentiated moderate rejection from edema. Discriminant analysis on all 22 patients correctly identified 96% of first rejection episodes (sensitivity 80%, specificity 64%), 93% of moderate and severe rejection episodes (sensitivity 71%; specificity 62%), and 69% of all rejection episodes (sensitivity 51%, specificity 91%). CONCLUSIONS: Histologic changes associated with moderate and severe pediatric allograft rejection as reflected by characteristic alterations in myocardial acoustics can be assessed with ultrasonographic tissue characterization. Histologic changes associated with transplantation itself (resolution of rejection and edema) also affect myocardial acoustics and must be taken into account in rejection surveillance. 相似文献