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   110271篇
  免费   13559篇
  国内免费   5434篇
电工技术   7010篇
技术理论   10篇
综合类   8571篇
化学工业   21725篇
金属工艺   4162篇
机械仪表   3844篇
建筑科学   12093篇
矿业工程   4264篇
能源动力   3260篇
轻工业   12634篇
水利工程   5037篇
石油天然气   4653篇
武器工业   1027篇
无线电   8287篇
一般工业技术   10642篇
冶金工业   5912篇
原子能技术   1248篇
自动化技术   14885篇
  2024年   537篇
  2023年   1954篇
  2022年   5437篇
  2021年   5956篇
  2020年   4003篇
  2019年   3699篇
  2018年   3791篇
  2017年   4537篇
  2016年   6153篇
  2015年   6394篇
  2014年   8038篇
  2013年   8345篇
  2012年   7246篇
  2011年   6927篇
  2010年   5434篇
  2009年   5480篇
  2008年   5115篇
  2007年   6698篇
  2006年   6702篇
  2005年   5502篇
  2004年   3947篇
  2003年   3552篇
  2002年   2738篇
  2001年   2023篇
  2000年   1717篇
  1999年   1273篇
  1998年   920篇
  1997年   779篇
  1996年   682篇
  1995年   545篇
  1994年   508篇
  1993年   357篇
  1992年   303篇
  1991年   248篇
  1990年   246篇
  1989年   214篇
  1988年   146篇
  1987年   104篇
  1986年   108篇
  1985年   85篇
  1984年   103篇
  1983年   80篇
  1982年   67篇
  1981年   51篇
  1980年   62篇
  1979年   32篇
  1966年   29篇
  1965年   36篇
  1964年   40篇
  1962年   66篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
For decades now, Douglas Crimp’s landmark 1980 essay ‘The Photographic Activity of Postmodernism’ has shaped our understanding of modernism’s aftermath, at least as it unfolded in North America and Western Europe. Less remembered, however, is the degree to which the procedures of disjunction, copying, appropriation, and outright theft that he highlighted were epitomised not just by contemporary photography, but by photomontage in particular. This article recovers the debates that led critics such as Crimp, Abigail Solomon-Godeau, Christopher Phillips, Benjamin Buchloh and others to turn to photomontage as one of their principal objects of concern in what became known as the postmodern critique of photography. Why was montage tasked to perform this critical function, particularly by people around the journal October who had not otherwise devoted the balance of their writing to photography’s history? The article suggests that these men and women, along with the contemporary artists they foregrounded, manifested what Mary Anne Doane has called a ‘desire for signification’, a reaction in the late 1970s against the mute theatricality of minimalist and conceptual art. Photomontage reintroduced representation to contemporary art and to the canon of art history. But unlike the reemerging illusionism in painting that also manifested this desire, montage guarded against an uncomplicated realism by highlighting and critiquing operations of representation in a manner that painting no longer could.  相似文献   
62.
Few jurisdictions have translated internationally agreed social impact assessment (SIA) principles into statutory provisions. Governments and regulatory bodies tend to provide developers with high-level frameworks, or require that social impacts be ‘considered’, without specifying how this is to be done. In Australia, this lack of clarity leaves all parties uncertain about requirements for SIA. The New South Wales (NSW) Government’s 2017 release of the SIA guideline for State-significant mining, petroleum and extractive industry development represents an attempt to clarify requirements and provide guidance. In this paper, we describe the process of bringing this guideline to fruition from the perspective of being directly involved in its development, and highlight the challenges involved in integrating leading-practice principles into the state’s pre-existing policy framework. While the guideline represents a significant advance in policy-based SIA guidance, some aspects leave room for improvement. The real test of the guideline’s impact will lie in its influence on SIA practice in NSW, and ultimately in social outcomes for communities affected by resources projects.  相似文献   
63.
本实验采用4D-非标记蛋白质组学技术研究秦川牛肉贮藏过程中(0~8 d)肌红蛋白含量及其衍生物的转化情况,阐释冷却秦川牛肉中肌红蛋白含量及其衍生物转化的分子机制。结果表明:贮藏过程中,肌红蛋白表达量在宰后0~4 d上升、4~8 d下降,利用非标记蛋白质组学技术鉴定出与肌红蛋白及其衍生物相关的差异蛋白14 种,具体包括代谢酶、氧化还原酶、过氧化物酶、伴侣蛋白4 类,这4 类蛋白的表达共同调控贮藏过程中肌红蛋白含量的变化及其3 种衍生物之间的转化,具体表现为贮藏过程中肌红蛋白表达量整体呈下降趋势,氧合肌红蛋白相对含量持续下降,脱氧肌红蛋白、高铁肌红蛋白相对含量逐渐增加,导致肉色发生褐变。本研究结果有利于理解秦川牛肉贮藏过程肉类变色的复杂生化变化机制。  相似文献   
64.
澳大利亚职业教育在全球享有较高的声誉,这与其坚持严格的"基于能力本位的评估"(competency based assessment, CBA)密不可分。介绍了澳大利亚CBA的内涵特征,并详细描述"准备评估、开发评估工具、开展评估、对评估结果进行评估"的CBA运作过程,关注评估工具的开发和后续常规系统性检查及完善,以期对我国的高等职业教育质量评估起到启示和借鉴作用。  相似文献   
65.
吴钟昊  彭仁 《食品科学》2021,42(22):98-104
对赤红球菌的组氨酸激酶基因进行密码子优化,将优化后的组氨酸激酶基因(rhks)构建重组表达质粒pGEX-4T-2-rhks。将此质粒导入到大肠杆菌BL21(DE3)中进行异源表达。在25 ℃和1 mmol/L异丙基-β-D-硫代吡喃半乳糖苷诱导条件下,组氨酸激酶融合蛋白(GST-RHK)获得成功表达,并具有催化活性。经谷胱甘肽琼脂糖亲和层析纯化,获得电泳纯的GST-RHK,其中纯化倍数为3.1,得率为19.5%。该蛋白大小约为72.75 kDa,Km、Vmax和Kcat值分别为20.92 μmol/L、0.17 μmol/(L·min)和1.4 min-1。野生型赤红球菌、组氨酸激酶基因增强株sdrhkE和组氨酸激酶基因敲减株sdrhkD在分别含有苯酚、甲苯、氯苯、异辛烷4 种有机溶剂的培养基中培养,菌株sdrhkD的生长情况都优于野生型赤红球菌,菌株sdrhkE的生长情况都低于野生型赤红球菌。本研究为进一步揭示赤红球菌SD3中组氨酸激酶涉及的信号转导途径与赤红球菌有机溶剂耐受性的关联机制提供一定参考依据。  相似文献   
66.
The autonomic nervous system (ANS) plays a crucial role both in acute and chronic psychological stress eliciting changes in many local and systemic physiological and biochemical processes. Salivary secretion is also regulated by ANS. In this study, we explored salivary proteome changes produced in thirty-eight University students by a test stress, which simulated an oral exam. Students underwent a relaxation phase followed by the stress test during which an electrocardiogram was recorded. To evaluate the effect of an olfactory stimulus, half of the students were exposed to a pleasant odor diffused in the room throughout the whole session. Saliva samples were collected after the relaxation phase (T0) and the stress test (T1). State anxiety was also evaluated at T0 and T1. Salivary proteins were separated by two-dimensional electrophoresis, and patterns at different times were compared. Spots differentially expressed were trypsin digested and identified by mass spectrometry. Western blot analysis was used to validate proteomic results. Anxiety scores and heart rate changes indicated that the fake exam induced anxiety. Significant changes of α-amylase, polymeric immunoglobulin receptor (PIGR), and immunoglobulin α chain (IGHA) secretion were observed after the stress test was performed in the two conditions. Moreover, the presence of pleasant odor reduced the acute social stress affecting salivary proteome changes. Therefore, saliva proteomic analysis was a useful approach to evaluate the rapid responses associated to an acute stress test also highlighting known biomarkers.  相似文献   
67.
以转基因水稻中最常用的CaMV35S启动子、NOS终止子、Cry1Ab/Ac基因、HPT基因及SPS水稻内标基因为研究对象,利用5 种不同的荧光信号(FAM、HEX、Taxas Red、Cy5、Cy5.5)进行多重实时聚合酶链式反应(real-time polymerase chain reaction,real-time PCR)检测方法的研究。通过引物组合筛选、反应体系优化、特异性测试、灵敏度测试、适用性测试等一系列实验,建立了5 重real-time PCR方法,灵敏度可达0.032%。此方法具有灵敏度高、结果准确、通量大等优点,可实现水稻中转基因成分的快速、高效检测。  相似文献   
68.
69.
Sarcopenia is the loss of skeletal muscle mass and function with advancing age. It involves both complex genetic and modifiable risk factors, such as lack of exercise, malnutrition and reduced neurological drive. Cognitive decline refers to diminished or impaired mental and/or intellectual functioning. Contracting skeletal muscle is a major source of neurotrophic factors, including brain-derived neurotrophic factor, which regulate synapses in the brain. Furthermore, skeletal muscle activity has important immune and redox effects that modify brain function and reduce muscle catabolism. The identification of common risk factors and underlying mechanisms for sarcopenia and cognition may allow the development of targeted interventions that slow or reverse sarcopenia and also certain forms of cognitive decline. However, the links between cognition and skeletal muscle have not been elucidated fully. This review provides a critical appraisal of the literature on the relationship between skeletal muscle health and cognition. The literature suggests that sarcopenia and cognitive decline share pathophysiological pathways. Ageing plays a role in both skeletal muscle deterioration and cognitive decline. Furthermore, lifestyle risk factors, such as physical inactivity, poor diet and smoking, are common to both disorders, so their potential role in the muscle–brain relationship warrants investigation.  相似文献   
70.
Raney-type Ni precursor alloys containing 75 at.% Al and doped with 0, 0.75, 1.5 and 3.0 at.% Ti have been produced by a gas atomization process. The resulting powders have been classified by size fraction with subsequent investigation by powder XRD, SEM and EDX analysis. The undoped powders contain, as expected, the phases Ni2Al3, NiAl3 and an Al-eutectic. The Ti-doped powders contain an additional phase with the TiAl3 DO22 crystal structure. However, quantitative analysis of the XRD results indicate a far greater fraction of the TiAl3 phase is present than could be accounted for by a simple mass balance on Ti. This appears to be a (TixNi1−x)Al3 phase in which higher cooling rates favour small x (low Ti-site occupancy by Ti atoms). SEM and EDX analysis reveal that virtually all the available Ti is contained within the TiAl3 phase, with negligible Ti dissolved in either the Ni2Al3 or NiAl3 phases.  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