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   1797篇
  免费   127篇
  国内免费   1篇
电工技术   24篇
化学工业   409篇
金属工艺   38篇
机械仪表   57篇
建筑科学   75篇
矿业工程   6篇
能源动力   56篇
轻工业   296篇
水利工程   26篇
石油天然气   16篇
无线电   176篇
一般工业技术   287篇
冶金工业   217篇
原子能技术   13篇
自动化技术   229篇
  2024年   3篇
  2023年   24篇
  2022年   50篇
  2021年   91篇
  2020年   45篇
  2019年   76篇
  2018年   79篇
  2017年   75篇
  2016年   76篇
  2015年   56篇
  2014年   83篇
  2013年   157篇
  2012年   109篇
  2011年   134篇
  2010年   99篇
  2009年   102篇
  2008年   79篇
  2007年   80篇
  2006年   64篇
  2005年   39篇
  2004年   34篇
  2003年   25篇
  2002年   27篇
  2001年   17篇
  2000年   18篇
  1999年   30篇
  1998年   66篇
  1997年   42篇
  1996年   31篇
  1995年   24篇
  1994年   12篇
  1993年   23篇
  1992年   4篇
  1991年   6篇
  1990年   5篇
  1989年   6篇
  1988年   10篇
  1987年   4篇
  1986年   2篇
  1985年   2篇
  1983年   2篇
  1982年   2篇
  1980年   1篇
  1979年   1篇
  1978年   2篇
  1977年   2篇
  1976年   6篇
排序方式: 共有1925条查询结果,搜索用时 31 毫秒
21.
Thin layers of silver and titanium were deposited onto commercial Ti–48Al particles by magnetron sputtering prior to their consolidation by hot isostatic pressing and subsequent heat treatment. Based on picnometry and electron probe microanalysis results, average values of 1.5 and 2.5 at.%, respectively, were obtained for the silver and titanium contents in the coated particles. The surface modified Ti–48Al particles exhibited improved sintering ability than the unmodified ones. The consolidated samples have duplex microstructures formed by γ-TiAl and γ-TiAl + α2-Ti3Al grains. Ag-rich nanoprecipitates were detected in the microstructure of the compacted Ti-48Al + Ag sample. The coatings are no longer visible at the grains boundaries after a subsequent homogenization heat treatment at 1200°C. The highest values of hardness and Young’s modulus were obtained for the Ti–48Al + Ag sample, associated with a higher density and a lower percentage of pores.  相似文献   
22.
23.
Aluminum has been reported to inhibit long-term potentiation (LTP) following in vivo administration and decrease glutamate release following in vitro exposure. Because glutamate release is critical for synaptic transmission and the development and maintenance of LTP in the hippocampus, we examined the effects of aluminum chloride (AlCl3) on depolarization-induced glutamate release and LTP in rat hippocampal slices. The effects of AlCl3 on [14C]glutamate release were examined by incubation of slices in depolarizing (56 mM)K+ buffer solution in the absence or presence of 2 mM CaCl2. After 15 min depolarization, AlCl3 (100-1000 microM) did not significantly affect Ca(2+)-dependent [14C]glutamate release from slices, whereas a known Ca2+ channel blocker (100 microM CdCl2) decreased Ca(2+)-dependent [14C]glutamate release by approximately 50%. In contrast to a previous report, acute exposure to AlCl3 was without effect on depolarization-dependent glutamate release. LTP of the population spike (PS) in CA1 of hippocampus was induced by the delivery of stimulus trains to the stratum radiatum. LTP of the PS was observed in both control slices and slices bathed in solution containing 100 microM AlCl3. Neither the magnitude nor longevity (measured up to 1 h posttrain) of LTP distinguished control from aluminum-exposed slices. The lack of sensitivity in rat to the encephalopathic changes induced by aluminum, or methodological differences in exposure conditions may account for the lack of effect of aluminum on in vitro LTP in rat hippocampus.  相似文献   
24.
This paper describes an automated medical record designed to allow providers to enter patient data at the point of care. The system runs on PCs and Macintoshes and uses a graphical user interface and object-oriented programming to take advantage of current mouse and pen technologies. The provider acquires all relevant patient data by pointing and clicking at selections on input screens, many of which contain anatomical drawings to help the provider quickly and accurately describe patient findings. The system also generates a grammatically correct progress note using the problem-oriented structure. Furthermore, items identified in the assessment and plans portion of the program can be ported to expert systems for medical decisions assistance or to billing systems. The system allows the provider to obtain the necessary information on a focused patient visit in less than 5 min or to enter a complete history and physical.  相似文献   
25.
We report the case of a 27-year-old patient with the human immunodeficiency virus (HIV) infection who presented with a 2-week history of crops of painful, red papules over the trunk and extremities, together with a sterile, symmetric polyarthritis involving the small and large joints. Histologic study of a skin biopsy specimen demonstrated features of papulonecrotic tuberculid. Analytical and microbiologic studies ruled out tuberculous infection. Both the synovial and the skin processes were considered to be an immune response secondary to Mycobacterium tuberculosis infection. Specific treatment was established, and there was marked improvement in both the skin and joint symptoms. This case illustrates the complex relationship between the host and the HIV, suggesting an immune dysregulation cause for both the synovial and the skin lesions.  相似文献   
26.
Microsystem Technologies - Tuberculosis is a contagious disease caused by the bacteria, Mycobacterium Tuberculosis. Early detection of TB is vital to increase the chances of cure. In this paper, a...  相似文献   
27.
28.
The recent popularity of digital cameras has posed a new problem: how to efficiently store and retrieve the very large number of digital photos captured and chaotically stored in multiple locations without any annotation. This paper proposes an infrastructure, called PhotoGeo, which aims at helping users with the people photo annotation, event photo annotation, storage and retrieval of personal digital photos. To achieve the desired objective, PhotoGeo uses new algorithms that make it possible to annotate photos with the key metadata to facilitate their retrieval, such as: the people who were shown in the photo (who); where it was captured (where); the date and time of capture (when); and the event that was captured. The paper concludes with a detailed evaluation of these algorithms.  相似文献   
29.
This paper presents feasible experimental schemes to realize controlled teleportation protocols via photonic Faraday rotations in low-Q cavities. The schemes deal with controlled teleportation of superposition states and two-particle entanglement of atomic states. The information is encoded in lambda configured three-level atoms trapped inside coupled cavities by optical fibers. Also, we estimate the success probability and the current feasibility of the schemes.  相似文献   
30.
Peptide-based drugs are an attractive class of therapeutic agents, recently recognized by the pharmaceutical industry. These molecules are currently being used in the development of innovative therapies for diverse health conditions, including tropical diseases such as leishmaniasis. Despite its socioeconomic influence on public health, leishmaniasis remains long-neglected and categorized as a poverty-related disease, with limited treatment options. Peptides with antileishmanial effects encountered to date are a structurally heterogeneous group, which can be found in different natural sources—amphibians, reptiles, insects, bacteria, marine organisms, mammals, plants, and others—or inspired by natural toxins or proteins. This review details the biochemical and structural characteristics of over one hundred peptides and their potential use as molecular frameworks for the design of antileishmanial drug leads. Additionally, we detail the main chemical modifications or substitutions of amino acid residues carried out in the peptide sequence, and their implications in the development of antileishmanial candidates for clinical trials. Our bibliographic research highlights that the action of leishmanicidal peptides has been evaluated mainly using in vitro assays, with a special emphasis on the promastigote stage. In light of these findings, and considering the advances in the successful application of peptides in leishmaniasis chemotherapy, possible approaches and future directions are discussed here.  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