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   861篇
  免费   13篇
  国内免费   4篇
电工技术   12篇
综合类   1篇
化学工业   115篇
金属工艺   9篇
机械仪表   8篇
建筑科学   41篇
能源动力   12篇
轻工业   81篇
水利工程   3篇
石油天然气   4篇
无线电   70篇
一般工业技术   103篇
冶金工业   355篇
原子能技术   5篇
自动化技术   59篇
  2022年   9篇
  2021年   6篇
  2020年   7篇
  2019年   6篇
  2017年   6篇
  2016年   6篇
  2015年   7篇
  2014年   8篇
  2013年   24篇
  2012年   13篇
  2011年   23篇
  2010年   22篇
  2009年   29篇
  2008年   30篇
  2007年   28篇
  2006年   27篇
  2005年   24篇
  2004年   21篇
  2003年   14篇
  2002年   22篇
  2001年   16篇
  2000年   14篇
  1999年   28篇
  1998年   72篇
  1997年   57篇
  1996年   37篇
  1995年   20篇
  1994年   26篇
  1993年   33篇
  1992年   10篇
  1991年   10篇
  1990年   12篇
  1989年   12篇
  1988年   11篇
  1987年   16篇
  1986年   11篇
  1985年   13篇
  1984年   9篇
  1983年   6篇
  1982年   8篇
  1981年   6篇
  1980年   9篇
  1979年   7篇
  1978年   6篇
  1977年   14篇
  1976年   19篇
  1975年   7篇
  1973年   6篇
  1971年   7篇
  1961年   6篇
排序方式: 共有878条查询结果,搜索用时 15 毫秒
91.
92.
93.
Comments on an article by Baruch on psychoanalysis and terrorism (see record 2003-09630-009). The author believes that there is an extra-analytic space for articulating that which is beyond analysts' work with patients and for informing their understanding of history, culture, politics, gender, power, and other phenomena. The rules that govern psychoanalysts' "analysis" of these extra-analytic phenomena are, however, different from those that govern their work with patients. The complexities and vicissitudes of psychoanalytic discourse within analysts' clinical frame (their standard clinical practice) are different for phenomena on the "outside." In addition, clinical psychoanalytic discourse cannot stand outside the powerful narratives of power, gender, race, class, and empire. A psychoanalytic perspective is important in addressing extra-analytic issues only after analysts understand their relationship to power, gender, race, class, and empire. Just as analysts check themselves with supervision and careful countertransference reflection, they must also check themselves when they engage in extra-analytic work. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
94.
The question whether immune pressure exerted by cytotoxic T lymphocytes (CTLs) can influence the long-term evolution of genetically stable viruses such as Epstein-Barr virus (EBV) has generated considerable scientific interest, primarily due to its important implications for the overall biology of the virus. While arguing for a role of CTLs in the evolution of viruses, it is important to differentiate between genetic variation in virus and immune recognition of these variant virus by CTLs. To assess the role of genetic selection in the long-term evolution of EBV, we have analyzed a large panel of type 1 EBV isolates from African, Southeast Asian, Papua-New Guinean (PNG), and Australian Caucasian individuals. Seven different regions of the EBV genome, which include nine CTL epitopes restricted through a range of HLA class I alleles, were sequenced and compared. Although numerous nucleotide changes were identified within these isolates, comparison of synonymous and nonsynonymous substitutions in the CTL epitope indicated that the genetic variation was generated mostly independently of immune selection pressure. Surprisingly, an inverse correlation between genetic variation within certain CTL epitopes and the frequency distribution of HLA alleles that present the CTL epitopes was seen, suggesting that the evolutionary pressures on the CTL epitopes of the virus may be toward their conservation rather than their inactivation. Furthermore, molecular evolutionary genetic analysis of nucleotide sequences revealed that viral isolates from PNG are evolving as a lineage distinct from isolates from African, Southeast Asian, and Australian Caucasian individuals.  相似文献   
95.
In this paper, we investigate the formal expressive properties of Stratified Feature Grammar (SFG), a new logic-based linguistic framework motivated by relational grammar and metagraph grammar, as well as by Kasper-Rounds logic. The driving force behind SFG is the generalization of the conceptfeature from an unanalyzable atomic one to a sequence of so-called R-signs. The linguistic interpretation of thesestratified features is that each R-sign in such a sequence denotes a primitive grammatical relation such as subject or direct object in different syntactic “strata”. This generalization permits the specification of a rigorous feature-structure-based formalism for natural-language grammars based on the view that syntax is “multistratal” and “relational”. The introduction of stratified features leads to several other innovations, two of which might have utility in other frameworks. One is the idea of imposing a partial order on features. The other is the concept of(data) justification: essentially, this is a stipulation that for an S-graph to be well-formed with respect to some grammarG it must, in addition to satisfying the rules ofG, have each of its “core” data (each feature occurrence, each node-label occurrence and each instance of so-called structure-sharing) justified in a formally precise manner by some rule of Justification ensures that. Justification ensures that satisfying S-graphs do not have more structure than absolutely necessary and so makes it appealing to a notion of “minimal model” otiose. Justification plays a key role in a number of our proofs. The formal results presented here include the following. First, it is proved that in the unrestricted SFG framework, every type 0 (r.e.) language is generated by some SFG. Then, we restrict the framework to so-calledbounded SFG with two linguistically motivated principles: Lexical Anchoring and Boundedness. Anchoring requires, in essence, that each core datum of an S-graph be justified by aword in its yield. Boundedness insures that S-graph features are short. Although these restrictions together put the class of bounded SFG languages well within the class of recursive languages, we go on to demonstrate that the recognition problem for bounded SFG is NP-hard. Further, we establish that a bounded SFG language need not be semi-linear. On the matter of upper bounds, we show that every bounded SFL can be recognized by a nondeterministic Turing machine inn logn space and polynomial time and that the recognition problem for bounded SFL's is NP-complete.  相似文献   
96.
97.
The use of neural networks for automatic identification of variegated coloring, which is believed to be one of the most predictive features for malignant melanoma, is described. The Nestor development system (NDS) was chosen for neural network implementation. At the heart of NDS is a three-layer neural network called a restricted Coulomb energy (RCE) network. The learning scheme and the database for detection of variegated coloring are discussed. Results are reported  相似文献   
98.
In 3 cross-modal priming experiments, the authors investigated whether access to a word's meaning is affected by the semantic context in which it is heard or is exhaustive and context-independent. The access of nonassociated semantic properties and normatively associated words before and after prime offset was probed. Whereas associated targets were primed context-independently, access to semantic property targets was affected by the sentential context. Semantic property targets showed greater priming in a sentence biasing to a specific semantic property than in a neutral condition, even when this bias made the target property irrelevant rather than relevant. These results cannot be accounted for by current exhaustive access or context-dependency theories of lexical access. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
99.
Pancreatic islets of Langerhans are composed of four major endocrine cell types with a smaller number of nonendocrine cells. To study the molecular constituents and function of just one subpopulation of islet cells, it is necessary to sort them from the other cell types. While rat beta-cells can be sorted by autofluorescence-activated flow cytometry, this has not proved possible on a routine and reproducible basis for human beta-cells. In the present study, we have selectively labeled human beta-cells with green fluorescent protein (GFP), allowing for their sorting by flow cytometry. Human islet cells were infected with replication-defective (attenuated) recombinant adenovirus expressing GFP driven by the rat insulin I promoter (Ad-RIP-GFP) for targeted expression in beta-cells, or beta-galactosidase driven by the promiscuous cytomegalovirus (CMV) promoter (Ad-CMV-beta-gal) as control. Whereas the majority of islet cells can be infected by adenovirus, as shown by control infection with Ad-CMV-beta-gal, increased fluorescence after infection with Ad-RIP-GFP was limited to insulin-containing beta-cells. Infection of islet cells with Ad-RIP-GFP resulted reproducibly in the appearance of a population of intensely fluorescent cells, when analyzed by flow cytometry. These cells were sorted using a fluorescence-activated cell sorter (FACS) and shown by immunofluorescence to consist of >95% beta-cells. The targeted expression of GFP thus allows for preparation of human beta-cells purified close to homogeneity. This method should be readily applicable in any laboratory with FACS capability.  相似文献   
100.
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