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   4549篇
  免费   108篇
  国内免费   6篇
电工技术   124篇
综合类   8篇
化学工业   1072篇
金属工艺   90篇
机械仪表   95篇
建筑科学   283篇
矿业工程   20篇
能源动力   106篇
轻工业   468篇
水利工程   57篇
石油天然气   8篇
无线电   319篇
一般工业技术   587篇
冶金工业   847篇
原子能技术   75篇
自动化技术   504篇
  2022年   45篇
  2021年   71篇
  2020年   44篇
  2019年   57篇
  2018年   45篇
  2017年   55篇
  2016年   66篇
  2015年   71篇
  2014年   102篇
  2013年   193篇
  2012年   136篇
  2011年   208篇
  2010年   133篇
  2009年   137篇
  2008年   170篇
  2007年   144篇
  2006年   148篇
  2005年   116篇
  2004年   104篇
  2003年   99篇
  2002年   103篇
  2001年   68篇
  2000年   66篇
  1999年   81篇
  1998年   144篇
  1997年   118篇
  1996年   87篇
  1995年   86篇
  1994年   73篇
  1993年   63篇
  1992年   51篇
  1991年   50篇
  1990年   63篇
  1989年   59篇
  1988年   52篇
  1987年   59篇
  1986年   51篇
  1985年   65篇
  1984年   61篇
  1983年   63篇
  1982年   53篇
  1981年   44篇
  1979年   48篇
  1978年   60篇
  1977年   61篇
  1976年   69篇
  1975年   55篇
  1974年   52篇
  1973年   59篇
  1972年   43篇
排序方式: 共有4663条查询结果,搜索用时 15 毫秒
101.
This paper examines the dissolution behavior of the (111)A, (111)B, (110), and (100) surfaces of CdTe single crystals in aqueous H2O2-HI-C6H8O7 (citric acid) solutions. We have determined the dissolution rate of the crystals as a function of temperature and solution concentration, located the composition regions of polishing and selective etchants, and studied the microstructure and roughness of surfaces polished with optimized etchants. The etching behavior of CdTe is shown to depend on its crystallographic orientation.  相似文献   
102.
Outcome of acute renal failure (ARF) and use of continuous renal replacement therapy (CRRT) have shown a consistently high mortality. (1) Evaluate the short-term patient survival. (2) Evaluate dialysis-free survival. (3) Evaluate risk factors associated with overall survival and the continued need for intermittent dialysis. We identified adults (≥18 years) needing CRRT, treated in the critical care units of Froedtert Medical and Lutheran Hospital from January 1, 2003 till December 31, 2005. Patients were divided into two major groups needing CRRT, end stage renal disease (ESRD) (chronic dialysis) and non-ESRD with ARF. Continuous renal replacement therapy was performed with an average of 2 L replacement fluid exchanges/h. Sigma stat software was used for analysis. Comparison was done for noncontinuous variables by chi-square and t test for categorical and continuous variables, respectively. A total of 110 (ESRD 24/non-ESRD 86) patients received CRRT during study period. Over all in-hospital mortality among non-ESRD patients was 63% vs. 46% for ESRD. Among non-ESRD patients who survived, 47% needed intermittent hemodialysis on intensive care unit discharge and 28% continued to need hemodialysis at last follow-up. Among non-ESRD patients alive at discharge, those who were dialysis dependent on last follow-up were older (64.5) than those who did not require dialysis on last follow-up (58.4) P=0.347. Non-ESRD patients who died were in the hospital for an average of 17.5 days compared with 29 days for those who were discharged from the hospital. Patients with ARF needing CRRT have high in-hospital mortality. A significant percentage of patients remained dialysis dependant on last follow-up.  相似文献   
103.
Low‐noise amplifier (LNA) designers often struggle to simultaneously satisfy gain, noise, stability, and I/O matching requirements. In this article, a novel design technique, tailored for two‐stage low‐noise amplifiers, is presented. The proposed design method is completely deterministic and exploits inductive source degeneration to obtain a two‐stage LNA featuring perfect input and output match together with low noise figure (NF) and a pre‐determined gain, including stability analysis. A novel flowchart is provided together with the corresponding design chart that contains gain, matching, and stability information, therefore addressing all key figures‐of‐merit of a linear amplifier. The design chart is easily implementable in commercial Electronic Design Automation software, to aid designers in the difficult task of selecting the appropriate source degeneration inductor value. The noise performance, on the other hand, is the best possible since the matching networks are designed to provide the input of the two Field Effect Transistors with the optimum termination for noise. The design method is validated with two separate test vehicles operating respectively at Ka‐band (26.5‐31.5 GHz) and K‐band (20.0‐24.0 GHz). The realized Monolithic Microwave Integrated Circuits exhibit 18 dB gain for both versions, NF of 1.5 and 1.2 dB, respectively for the Ka‐band and K‐band version. Input and output matching are typically better than 12 and 15 dB.  相似文献   
104.
Software is changed frequently during its life cycle. New requirements come, and bugs must be fixed. To update an application, it usually must be stopped, patched, and restarted. This causes time periods of unavailability, which is always a problem for highly available applications. Even for the development of complex applications, restarts to test new program parts can be time consuming and annoying. Thus, we aim at dynamic software updates to update programs at runtime. There is a large body of research on dynamic software updates, but so far, existing approaches have shortcomings either in terms of flexibility or performance. In addition, some of them depend on specific runtime environments and dictate the program's architecture. We present JavAdaptor , the first runtime update approach based on Java that (a) offers flexible dynamic software updates, (b) is platform independent, (c) introduces only minimal performance overhead, and (d) does not dictate the program architecture. JavAdaptor combines schema changing class replacements by class renaming and caller updates with Java HotSwap using containers and proxies. It runs on top of all major standard Java virtual machines. We evaluate our approach's applicability and performance in non‐trivial case studies and compare it with existing dynamic software update approaches. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   
105.
Type 2 diabetes mellitus (T2DM) can result in microvascular complications such as neuropathy, retinopathy, nephropathy, and cerebral small vessel disease, and contribute to macrovascular complications, such as heart failure, peripheral arterial disease, and large vessel stroke. T2DM also increases the risks of depression and dementia for reasons that remain largely unclear. Perturbations in the cytochrome P450-soluble epoxide hydrolase (CYP-sEH) pathway have been implicated in each of these diabetes complications. Here we review evidence from the clinical and animal literature suggesting the involvement of the CYP-sEH pathway in T2DM complications across organ systems, and highlight possible mechanisms (e.g., inflammation, fibrosis, mitochondrial function, endoplasmic reticulum stress, the unfolded protein response and autophagy) that may be relevant to the therapeutic potential of the pathway. These mechanisms may be broadly relevant to understanding, preventing and treating microvascular complications affecting the brain and other organ systems in T2DM.  相似文献   
106.
Mitochondria play a crucial role in cell physiology and pathophysiology. In this context, mitochondrial dynamics and, subsequently, mitochondrial ultrastructure have increasingly become hot topics in modern research, with a focus on mitochondrial fission and fusion. Thus, the dynamics of mitochondria in several diseases have been intensively investigated, especially with a view to developing new promising treatment options. However, the majority of recent studies are performed in highly energy-dependent tissues, such as cardiac, hepatic, and neuronal tissues. In contrast, publications on mitochondrial dynamics from the orthopedic or trauma fields are quite rare, even if there are common cellular mechanisms in cardiovascular and bone tissue, especially regarding bone infection. The present report summarizes the spectrum of mitochondrial alterations in the cardiovascular system and compares it to the state of knowledge in the musculoskeletal system. The present paper summarizes recent knowledge regarding mitochondrial dynamics and gives a short, but not exhaustive, overview of its regulation via fission and fusion. Furthermore, the article highlights hypoxia and its accompanying increased mitochondrial fission as a possible link between cardiac ischemia and inflammatory diseases of the bone, such as osteomyelitis. This opens new innovative perspectives not only for the understanding of cellular pathomechanisms in osteomyelitis but also for potential new treatment options.  相似文献   
107.
In this paper, we investigate single-state, semi-quantum key distribution protocols. These are protocols whereby one party is limited to measuring only in the computational basis, while the other, though capable of measuring in both computational and Hadamard bases, is limited to preparing and sending only a single, publicly known qubit state. Such protocols rely necessarily on a two-way quantum communication channel making their security analysis difficult. However, we will show that, for single-state protocols, we need only consider a restricted attack operation by Eve. We will also describe a new single-state protocol that permits “reflections” to carry information and use our results concerning restricted attacks to show its robustness.  相似文献   
108.
109.
Zebrafish is a useful animal model for studying human diseases such as muscle disorders. However, manual monitoring of fish motion is time-consuming and prone to subjective variations. In this paper, an automatic fish motion analytics framework is proposed. The proposed framework could be exploited to help validate zebrafish models of transgenic zebrafish that express human genes carrying mutations which lead to muscle disorders, thus affecting their ability to swim normally. To differentiate between wild-type (normal) and transgenic zebrafish, the proposed framework consists of two approaches to exploit discriminative spatial–temporal kinematic features which are extracted to represent zebrafish movements. First, the proposed approach studies precise quantitative measurements of motor movement abnormalities using a camera with the capability to record videos with high frames rates (up to 1,000 frames per second). This differs from previous works, which only tracked each fish as a single point over time. Second, the proposed approach studies multi-view spatial–temporal swimming trajectories. This differs from previous works which typically only considered single-view analysis of fish swimming trajectories. The proposed motion features are then incorporated into a supervised classification approach to identify abnormal fish movements. Experimental results have shown that the proposed approach is capable of differentiating between wild-type and transgenic zebrafish, thus helping to validate the zebrafish models.  相似文献   
110.
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