首页 | 官方网站   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   5812篇
  免费   168篇
  国内免费   17篇
工业技术   5997篇
  2023年   51篇
  2022年   59篇
  2021年   136篇
  2020年   122篇
  2019年   115篇
  2018年   153篇
  2017年   142篇
  2016年   126篇
  2015年   97篇
  2014年   139篇
  2013年   380篇
  2012年   208篇
  2011年   277篇
  2010年   230篇
  2009年   224篇
  2008年   251篇
  2007年   207篇
  2006年   193篇
  2005年   199篇
  2004年   155篇
  2003年   139篇
  2002年   117篇
  2001年   115篇
  2000年   89篇
  1999年   99篇
  1998年   224篇
  1997年   166篇
  1996年   124篇
  1995年   83篇
  1994年   114篇
  1993年   107篇
  1992年   89篇
  1991年   71篇
  1990年   60篇
  1989年   52篇
  1988年   62篇
  1987年   55篇
  1986年   54篇
  1985年   78篇
  1984年   60篇
  1983年   49篇
  1982年   42篇
  1981年   51篇
  1980年   41篇
  1979年   42篇
  1978年   40篇
  1977年   48篇
  1976年   46篇
  1974年   32篇
  1973年   36篇
排序方式: 共有5997条查询结果,搜索用时 15 毫秒
91.
92.
The 1,3-specific lipase-catalyzed interesterified fats were distinguished from chemically catalyzed products by the fatty acids in the 2-position. The fatty acid contents in the 2-position of the 1,3-lipase-catalyzed and the original triglycerides were similar but different from that of chemically interesterified fat. Also, the saturated-to-unsaturated fatty acid ratio in the 2-monoglycerides was lower for the 1,3-specific lipase-catalyzed interesterified fats than for the corresponding chemical products.  相似文献   
93.
Persistent polyclonal B cell lymphocytosis (PPBL) is a rare lymphoproliferative disorder of unclear natural history and its potential for B cell malignancy remains unknown. We describe the case of a 39-year-old female who presented with stage IV-B large cell lymphoma 19 years after an initial diagnosis of PPBL; her disease was rapidly fatal despite intensive chemotherapy and blood stem cell transplantation. Because we had recently identified multiple bcl-2/Ig gene rearrangements in blood mononuclear cells of patients with PPBL, we sought evidence of this oncogene in this particular patient: bcl-2/Ig gene rearrangements were found in blood mononuclear cells but not in lymphoma cells. Owing to the possible role of Epstein-Barr virus (EBV) in the pathogenesis of PPBL, we also hypothesized our patient might have an EBV-related lymphoproliferative disorder. Despite serologies consistent with past exposure to this virus, it was not found in lymphoma cells using a sensitive polymerase chain reaction technique. We conclude that non-Hodgkin's lymphoma may occur during the course of PPBL. However, longer follow-up in more patients will be needed in order to better clarity the risk of hematologic malignancy in patients with PPBL.  相似文献   
94.
BACKGROUND: Bluetongue virus (BTV), which belongs to the Reoviridae family and orbivirus genus, is a non-enveloped, icosahedral, double-stranded RNA virus. Several protein layers enclose its genome; upon cell entry the outer layer is stripped away leaving a core, the surface of which is composed of VP7. The structure of the trimeric VP7 molecule has previously been determined using X-ray crystallography. The articulated VP7 subunit consists of two domains, one which is largely alpha-helical and the other, smaller domain, is a beta barrel with jelly-roll topology. The relative orientations of these two domains vary in different crystal forms. The structure of VP7 and the organizations of 780 subunits of this molecule in the core of virus is central to the assembly and function of BTV. RESULTS: A 23 A resolution map of the core, determined using electron cryomicroscopy (cryoEM) data, reveals that the 260 trimers of VP7 are organized on a rather precise T = 13 laevo icosahedral lattice, in accordance with the theory of quasi-equivalence. The VP7 layer occupies a shell that is between 260 A and 345 A from the centre of the core. Below this radius (230-260 A) lies the T = 1 layer of 120 molecules of VP3. By fitting the X-ray structure of an individual VP7 trimer onto the cryoEM BTV core structure, we have generated an atomic model of the VP7 layer of BTV. This demonstrates that one of the molecular structures seen in crystals of the isolated VP7 corresponds to the in vivo conformation of the molecule in the core. CONCLUSIONS: The beta-barrel domains of VP7 are external to the core and interact with protein in the outer layer of the mature virion. The lower, alpha-helical domains of VP7 interact with VP3 molecules which form the inner layer of the BTV core. Adjacent VP7 trimer-trimer interactions in the T = 13 layer are mediated principally through well-defined regions in the broader lower domains, to form a structure that conforms well with that expected from the theory of quasi-equivalence with no significant conformational changes within the individual trimers. The VP3 layer determines the particle size and forms a rather smooth surface upon which the two-dimensional lattice of VP7 trimers is laid down.  相似文献   
95.
Water Resources Management - Reference evapotranspiration (ET0) is a crucial element for deriving irrigation scheduling of major crops. Thus, precise projection of ET0 is essential for better...  相似文献   
96.
Motivated by both distributed computation and decentralized control applications, we studied the distributed linear iterative algorithms with memory. Specifically, we showed that the system of linear equations G x = b can be solved through a distributed linear iteration for arbitrary invertible G using only a single memory element at each processor. Further, we demonstrated that the memoried distributed algorithm can be designed to achieve much faster convergence than a memoryless distributed algorithm. Two small simulation examples were included to illustrate the results. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   
97.
This paper presents OS-Guard(On-Site Guard), a novel on-site signature based framework for multimedia surveillance data management. One of the major concerns in widespread deployment of multimedia surveillance systems is the enormous amount of data collected from multiple media streams that need to be communicated, observed and stored for crime alerts and forensic analysis. This necessitates investigating efficient data management techniques to solve this problem. This work aims to tackle this problem, motivated by the following observation, more data does not mean more information. OS-Guard is a novel framework that attempts to collect informative data and filter out non-informative data on-site, thus taking a step towards solving the data management problem. In the framework, both audio and video cues are utilized by extracting features from the incoming data stream and the resultant real valued feature data is binarized for efficient storage and processing. A feature selection process based on association rule mining selects discriminant features. A short representative sample of the whole database is generated using a novel reservoir sampling algorithm that is stored onsite and used with an support vector machine to classify an important event. Initial experiments for a Bank ATM monitoring scenario demonstrates promising results.  相似文献   
98.
Summary The synthesis of telechelic monodispersed diols produced from the radical telomerization of an excess of undecylenol with commercialy available , -dithiols HSC2H4XC2H4SH (X=0, S or CH2) initiated by peroxides is presented. In each case, the diols were obtained selectively and quantitatively and they were characterized by both 1H and 13C NMR. Their physical characteristics (Tg, Tm and decomposition temperatures) were determined. Such compounds are thermally more stable than polydispersed telechelic commercially available diols.  相似文献   
99.
lpcvd polycrystalline silicon films were deposited on thermally oxidized silicon as well as onlpcvd silicon nitride deposited on silicon. Acw argon ion laser was used to recrystallize the polysilicon film into large grains (grain size from 5μm to 40μm). Boron was then implanted and standard N-channel silicon gate process and N-channel metal gate process were carried out to realisemosfets on this material. Channel mobilities upto 450 cm2/V-sec for electrons have been measured. This thin filmmosfet has a four-terminal structure with a top and a bottom gate and the influence of one gate on the drain current due to the other gate has been investigated. Comparison of theI D v-V D curves of the devices with physical models was found in good agreement.  相似文献   
100.
Sen  Dipanjan  Sengupta  Savio Jay  Roy  Swarnil  Chanda  Manash 《SILICON》2021,13(4):1165-1175
Silicon - In this article, the electrical behavior of short channel SiGe Heterostructure Junction-Less DG-MOSFET have been studied by incorporating the quantum mechanical effect and short channel...  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-23

京公网安备 11010802026262号