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   1339篇
  免费   46篇
  国内免费   5篇
电工技术   15篇
综合类   2篇
化学工业   369篇
金属工艺   19篇
机械仪表   35篇
建筑科学   63篇
矿业工程   2篇
能源动力   39篇
轻工业   140篇
水利工程   9篇
石油天然气   1篇
无线电   116篇
一般工业技术   194篇
冶金工业   72篇
原子能技术   11篇
自动化技术   303篇
  2023年   16篇
  2022年   47篇
  2021年   60篇
  2020年   24篇
  2019年   28篇
  2018年   33篇
  2017年   33篇
  2016年   57篇
  2015年   30篇
  2014年   39篇
  2013年   97篇
  2012年   82篇
  2011年   94篇
  2010年   69篇
  2009年   75篇
  2008年   61篇
  2007年   67篇
  2006年   63篇
  2005年   48篇
  2004年   48篇
  2003年   37篇
  2002年   36篇
  2001年   19篇
  2000年   17篇
  1999年   15篇
  1998年   26篇
  1997年   29篇
  1996年   13篇
  1995年   18篇
  1994年   18篇
  1993年   13篇
  1992年   10篇
  1991年   7篇
  1990年   4篇
  1989年   5篇
  1988年   7篇
  1987年   2篇
  1986年   2篇
  1985年   3篇
  1984年   5篇
  1983年   9篇
  1982年   2篇
  1980年   2篇
  1979年   3篇
  1977年   2篇
  1976年   2篇
  1973年   2篇
  1970年   2篇
  1963年   1篇
  1903年   1篇
排序方式: 共有1390条查询结果,搜索用时 15 毫秒
71.
The advent of 2D nanostructured materials as advanced fillers for polymer matrix composites has opened the doors to a plethora of new industrial applications requiring both electric and thermal management. Unique properties, in fact, can arise from accurate selection and processing of 2D fillers and their matrix. Here, we report an innovative family of nanocomposite membranes based on polyurethane (PU) and graphene nanoplatelets (GNPs), designed to improve thermal comfort in functional textiles. GNP particles were thoroughly characterized (through Raman, atomic force microscopy, high-resolution TEM, scanning electron microscope), and showed high crystallinity (ID/IG = 0.127), low thickness (D50 < 6–8 layers), and high lateral dimensions (D50 ≈ 3 μm). When GNPs were loaded (up to 10% wt/wt) into the PU matrix, their homogeneous dispersion resulted in an increase of the in-plane thermal conductivity of composite membranes up to 471%. The thermal dissipation of membranes, alone or coupled with cotton fabric, was further evaluated by means of an ad hoc system designed to simulate a human forearm. The results obtained provide a new strategy for the preparation of membranes suitable for technical textiles, with improved thermal comfort.  相似文献   
72.
Present assembly systems are often based on rigid, line-based approaches and are hindered in their reconfiguration capability. Line-less Mobile Assembly Systems (LMAS) are a novel approach for assembly organization. They improve flexibility through mobile resources, permitting spatiotemporal freedom in scheduling and resource assignment. This paper presents a method for a priori assessment of LMAS during the early stages of the assembly system design process. The method applies a modified, extended mean value analysis to a closed queuing network representation of LMAS to estimate performance. The method is validated model analysis and comparison on two use cases indicating plausible model behavior.  相似文献   
73.
Clinical and animal studies have demonstrated that chemotherapeutic doxorubicin (DOX) increases arterial stiffness, a predictor of cardiovascular risk. Despite consensus about DOX-impaired endothelium-dependent vasodilation as a contributing mechanism, some studies have reported conflicting results on vascular smooth muscle cell (VSMC) function after DOX treatment. The present study aimed to investigate the effects of DOX on VSMC function. To this end, mice received a single injection of 4 mg DOX/kg, or mouse aortic segments were treated ex vivo with 1 μM DOX, followed by vascular reactivity evaluation 16 h later. Phenylephrine (PE)-induced VSMC contraction was decreased after DOX treatment. DOX did not affect the transient PE contraction dependent on Ca2+ release from the sarcoplasmic reticulum (0 mM Ca2+), but it reduced the subsequent tonic phase characterised by Ca2+ influx. These findings were supported by similar angiotensin II and attenuated endothelin-1 contractions. The involvement of voltage-gated Ca2+ channels in DOX-decreased contraction was excluded by using levcromakalim and diltiazem in PE-induced contraction and corroborated by similar K+ and serotonin contractions. Despite the evaluation of multiple blockers of transient receptor potential channels, the exact mechanism for DOX-decreased VSMC contraction remains elusive. Surprisingly, DOX reduced ex vivo but not in vivo arterial stiffness, highlighting the importance of appropriate timing for evaluating arterial stiffness in DOX-treated patients.  相似文献   
74.
KCND3 encodes the voltage-gated potassium channel KV4.3 that is highly expressed in the cerebellum, where it regulates dendritic excitability and calcium influx. Loss-of-function KV4.3 mutations have been associated with dominant spinocerebellar ataxia (SCA19/22). By targeted NGS sequencing, we identified two novel KCND3 missense variants of the KV4.3 channel: p.S347W identified in a patient with adult-onset pure cerebellar syndrome and p.W359G detected in a child with congenital nonprogressive ataxia. Neuroimaging showed mild cerebellar atrophy in both patients. We performed a two-electrode voltage-clamp recording of KV4.3 currents in Xenopus oocytes: both the p.G345V (previously reported in a SCA19/22 family) and p.S347W mutants exhibited reduced peak currents by 50%, while no K+ current was detectable for the p.W359G mutant. We assessed the effect of the mutations on channel gating by measuring steady-state voltage-dependent activation and inactivation properties: no significant alterations were detected in p.G345V and p.S347W disease-associated variants, compared to controls. KV4.3 expression studies in HEK293T cells showed 53% (p.G345V), 45% (p.S347W) and 75% (p.W359G) reductions in mutant protein levels compared with the wildtype. The present study broadens the spectrum of the known phenotypes and identifies additional variants for KCND3-related disorders, outlining the importance of SCA gene screening in early-onset and congenital ataxia.  相似文献   
75.
Chronic obstructive pulmonary disease (COPD) caused by cigarette smoke (CS) is featured by oxidative stress and chronic inflammation. Due to the poor efficacy of standard glucocorticoid therapy, new treatments are required. Here, we investigated whether the novel compound SUL-151 with mitoprotective properties can be used as a prophylactic and therapeutic treatment in a murine CS-induced inflammation model. SUL-151 (4 mg/kg), budesonide (500 μg/kg), or vehicle were administered via oropharyngeal instillation in this prophylactic and therapeutic treatment setting. The number of immune cells was determined in the bronchoalveolar lavage fluid (BALF). Oxidative stress response, mitochondrial adenosine triphosphate (ATP) production, and mitophagy-related proteins were measured in lung homogenates. SUL-151 significantly decreased more than 70% and 50% of CS-induced neutrophils in BALF after prophylactic and therapeutic administration, while budesonide showed no significant reduction in neutrophils. Moreover, SUL-151 prevented the CS-induced decrease in ATP and mitochondrial mtDNA and an increase in putative protein kinase 1 expression in the lung homogenates. The concentration of SUL-151 was significantly correlated with malondialdehyde level and radical scavenging activity in the lungs. SUL-151 inhibited the increased pulmonary inflammation and mitochondrial dysfunction in this CS-induced inflammation model, which implied that SUL-151 might be a promising candidate for COPD treatment.  相似文献   
76.
High-mobility group box 1 protein (HMGB1) is a damage-associated molecular pattern (DAMP) involved in neutrophil extracellular trap (NET) formation and thrombosis. NETs are regularly found in cerebral thromboemboli. We here analyzed associated HMGB1 expression in human thromboemboli retrieved via mechanical thrombectomy from 37 stroke patients with large vessel occlusion. HMGB1 was detected in all thromboemboli, accounting for 1.7% (IQR 0.6–6.2%) of the total thromboemboli area and was found to be colocalized with neutrophils and NETs and in spatial proximity to platelets. Correlation analysis revealed that the detection of HMGB1 was strongly related to the number of neutrophils (r = 0.58, p = 0.0002) and platelets (r = 0.51, p = 0.001). Our results demonstrate that HMGB1 is a substantial constituent of thromboemboli causing large vessel occlusion stroke.  相似文献   
77.
The Dominican Republic is a tobacco-growing country, and tobacco control efforts there have been virtually nonexistent. This study provides a first systematic surveillance of tobacco use in six economically disadvantaged Dominican Republic communities (two small urban, two peri-urban, two rural; half were tobacco growing). Approximately 175 households were randomly selected in each community (total N = 1,048), and an adult household member reported on household demographics and resources (e.g., electricity), tobacco use and health conditions of household members, and household policies on tobacco use. Poverty and unemployment were high in all communities, and significant gaps in access to basic resources such as electricity, running water, telephones/cell phones, and secondary education were present. Exposure to tobacco smoke was high, with 38.4% of households reporting at least one tobacco user, and 75.5% allowing smoking in the home. Overall, 22.5% reported using tobacco, with commercial cigarettes (58.0%) or self-rolled cigarettes (20.1%) the most commonly used types. Considerable variability in prevalence and type of use was found across communities. Overall, tobacco use was higher in males, illiterate groups, those aged 45 or older, rural dwellers, and tobacco-growing communities. Based on reported health conditions, tobacco attributable risks, and World Health Organization mortality data, it is estimated that at least 2,254 lives could potentially be saved each year in the Dominican Republic with tobacco cessation. Although it is expected that the reported prevalence of tobacco use and health conditions represent underestimates, these figures provide a starting point for understanding tobacco use and its prevalence in the Dominican Republic.  相似文献   
78.
Artemisia vulgaris L. (Mugwort) is a threatened and valuable medicinal plant. Attempts have been made in this research to mass propagate its plantlets through in vitro liquid culture technology using Murashige and Skoog (MS) basal medium supplemented with 6-benzyl adenine (BA) (0.44-8.88 microM). Initially, 22.6 shoots (99.9% shooting frequency) developed from shoot tip explants cultured in MS with 4.44 microM BA at 100 ml flask capacity. This was further subcultured at increasing flask capacity (150, 250, and 500 ml) for shoot proliferation. Of the different concentrations of BA and flask capacities tested, 4.44 microM BA and 500 ml flask capacity were found to produce a maximum of 85.5 shoots after 30 d of culture. Shoot proliferation was found to increase with increasing flask capacity whereas shoot number decreased with increasing BA concentration (>4.44 microM). Individual shoots were isolated and rooted on MS medium containing 8.56 microM indole-3-acetic acid (IAA). Then the plantlets were acclimatized under standard laboratory conditions and later under greenhouse conditions. Fresh leaves were collected from greenhouse-grown plants and subjected to essential oil analysis by the simultaneous distillation and extraction method. GC-MS results revealed the presence of 88 components and the extracted oil was rich in camphor (16.8%), alpha-thujone (11.3%), germacrene D (7.2%), camphene (6.5%), 1,8-cineole (5.8%) and beta-caryophyllene (5.4%). This in vitro strategy can be a reliable method for the steady production of a large number of plants for essential oil production, which is reported for the first time for A. vulgaris.  相似文献   
79.
80.
拥有非常丰富的太阳能辐射资源的阳光地带,人口占全球人口总数的75%,电力需求占全球总需求的40%,该地区经济发展受到能源和环境的制约,充分利用丰富的太阳能辐射资源开发光伏发电产业,是可持续发展的重要手段。预测结果表明,范式转型情景中,这些国家的光伏装机容量甚至可达1 100 GW,也就是该地域发电总量的12%;2020年阳光地带国家光伏系统的发电成本将比建设天然气和燃油电站更具竞争力;至2030年光伏发电可以与所有以煤和天然气为燃料的中负荷电厂竞争。阳光地带国家发展股份发电目前还面临着许多障碍,这些障碍涉及到政府对燃油价格的补贴、服务于市场的能力以及能源公司的知识有限等,这些障碍有待于在发展过程中不断克服。中国和印度是阳光地带中的大国,两国的光伏制造业对阳光地带的影响很大。新能源被锁定为中国十二五规划的七大战略性新兴产业之一,中国的十二.五规划的重心是重新平衡经济增长模式,包括逐步扩大内需;国内光伏市场一旦打开,光伏在中国的发展将会非常迅速。释放阳光地带光伏潜力要求众多利益相关者共同参与协作,包括政府、银行和金融机构以及各行各业的支持,才能充分释放阳光地带的光伏发电潜力,带动光伏发电产业链的发展,成为社会经济...  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