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   2166篇
  免费   59篇
  国内免费   1篇
电工技术   10篇
综合类   11篇
化学工业   496篇
金属工艺   19篇
机械仪表   40篇
建筑科学   98篇
矿业工程   34篇
能源动力   56篇
轻工业   251篇
水利工程   16篇
石油天然气   12篇
无线电   79篇
一般工业技术   281篇
冶金工业   615篇
原子能技术   4篇
自动化技术   204篇
  2022年   34篇
  2021年   61篇
  2020年   26篇
  2019年   30篇
  2018年   40篇
  2017年   32篇
  2016年   50篇
  2015年   21篇
  2014年   50篇
  2013年   157篇
  2012年   71篇
  2011年   94篇
  2010年   84篇
  2009年   62篇
  2008年   77篇
  2007年   72篇
  2006年   79篇
  2005年   59篇
  2004年   41篇
  2003年   71篇
  2002年   53篇
  2001年   35篇
  2000年   45篇
  1999年   47篇
  1998年   74篇
  1997年   70篇
  1996年   49篇
  1995年   43篇
  1994年   48篇
  1993年   43篇
  1992年   31篇
  1990年   14篇
  1989年   26篇
  1988年   28篇
  1987年   15篇
  1986年   15篇
  1985年   25篇
  1984年   31篇
  1983年   23篇
  1982年   18篇
  1981年   14篇
  1980年   14篇
  1979年   16篇
  1978年   20篇
  1977年   13篇
  1976年   33篇
  1974年   14篇
  1973年   14篇
  1970年   13篇
  1969年   13篇
排序方式: 共有2226条查询结果,搜索用时 0 毫秒
111.
Adult and adolescent Ss were asked to list possible consequences of either accepting or declining opportunities to engage in various potentially risky behaviors (e.g., drinking and driving, skipping school to go to a mall). Response patterns were quite similar for these adults and adolescents, indicating shared beliefs about the possibilities. Although taking and avoiding a risk are logically complementary actions, they did not prove to be psychologically complementary. Other comparisons showed systematic differences in the consequences produced for 1-time and regular (or repeated) versions of the same behaviors, as well as open-ended and closed-ended response modes. These results are discussed in terms of their methodological implications for studying risk perceptions, their practical implications for influencing adolescents' risk behaviors, and their theoretical implications for understanding intellectual development. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
112.
7,8-Dichloro-1,2,3,4-tetrahydroisoquinoline (DCTQ) (50 mg/kg i.p.) antagonized the inactivation of MAO by pargyline as measured by direct enzyme assays in brain homogenates and by accumulation of hypothalamic catecholamines. These findings lend credence to the earlier interpretation that changes in brain concentrations of biogenic amines and their metabolites in DCTQ-treated rats were due at least in part to MAO inhibition.  相似文献   
113.
114.
The paper evaluates the impact of adoption of push-pull technology (PPT) on household welfare in terms of productivity, incomes and poverty status measured through per-capita food consumption in eastern Uganda. Push-pull is a habitat management strategy for the integrated management of stemborers, striga weeds and poor soil fertility involving the use of a natural repellent (push) and an attractant (pull). This biological technology simultaneously reduces the impact of three major production constraints to cereal-livestock farming in Africa ? pests, weeds and poor soil. Cross sectional survey data were collected from 560 households in four districts in the region (Busia, Tororo, Bugiri and Pallisa), in November and December 2014. Generalized propensity scoring (GPS) was used to determine the intensity of adoption of the technology (i.e., land area allocated to PPT) and also to estimate the dose-response function (DRF) relating intensity of adoption and household welfare. Results revealed that with increased intensity of reported adoption of PPT, the probability of being poor declined through increased maize yield per unit area, incomes, and per capita food consumption. However, its impact varied with the intensity of adoption. With an increase in the area allocated to PPT from 0.025 to 1 acre, average maize yield per unit area increased from 27 kg to 1400 kg, average household income increased from 135 US$ (Uganda Shilling (USh) 370,000) to 273 US$ (USh 750,000) and per capita food consumption increased from 15 US$ (USh 40,000) to 27 US$ (USh 75,000). The average probability of a household being poor (below a rural poverty line of US$ 12.71) declined from 48% to 28%. These findings imply that increased investment in the dissemination and expansion of PPT is essential for poverty reduction among smallholder farmers in Uganda.  相似文献   
115.
Data on the growth of cracks tested in aqueous solutions were interpreted in terms of surface force theory. For applied stress intensity factors greater than 0.25 MPa · m½, the position and the slope of the curves and their dependence on pH and ion concentration can be explained in terms of surface force theory, provided these forces are of a magnitude and range that are representative of those involved in the cohensive bonding of solids. Weaker forces, such as structural, double-layer, or dispersion forces, have little effect on crack growth in silica glass for K I > 0.25 MPa · m½.  相似文献   
116.
117.
557 Asian-American students (263 Chinese Americans, 185 Japanese Americans, and 109 Korean Americans) completed a survey consisting of a demographic questionnaire, a modified version of the Suinn-Lew Asia Self-Identity Acculturation Scale, and the Attitudes Toward Seeking Professional Psychological Help Scale (ATSPHS). A 3?×?2?×?2 multivariate analysis with main effects of ethnicity, gender, and level of acculturation and the 4 subscales of the ATSPHS as the dependent variables resulted in a significant F value for acculturation effect and nonsignificant F values for all other main and interaction effects. Regardless of ethnicity and gender, the most acculturated students were: (a) most likely to recognize personal need for professional psychological help, (b) most tolerant of the stigma associated with psychological help, and (c) most open to discussing their problems with a psychologist. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
118.
This work addresses the challenge of creating virtual agents that are able to portray culturally appropriate behavior when interacting with other agents or humans. Because culture influences how people perceive their social reality it is important to have agent models that explicitly consider social elements, such as existing relational factors. We addressed this necessity by integrating culture into a novel model for simulating human social behavior. With this model, we operationalized a particular dimension of culture—individualism versus collectivism—within the context of an interactive narrative scenario that is part of an agent-based tool for intercultural training. Using this scenario we conducted a cross-cultural study in which participants from a collectivistic country (Portugal) were compared with participants from an individualistic country (the Netherlands) in the way they perceived and interacted with agents whose behavior was either individualistic or collectivistic, according to the configuration of the proposed model. In the obtained results, Portuguese subjects rated the collectivistic agents more positively than the Dutch but both countries had a similarly positive opinion about the individualistic agents. This experiment sheds new light on how people from different countries differ when assessing the social appropriateness of virtual agents, while also raising new research questions on this matter.  相似文献   
119.
An important aspect in the specification of conceptual schemas is the definition of general constraints that cannot be expressed by the predefined constructs provided by conceptual modeling languages. This is generally achieved by using general-purpose languages like OCL. In this paper we propose a new approach that facilitates the definition of such general constraints in UML. More precisely, we define a profile that extends the set of predefined UML constraints by adding certain types of constraints that are commonly used in conceptual schemas. We also show how our proposal facilitates reasoning about the constraints and their automatic code generation, study the application of our ideas to the specification of two real-life applications, and present a prototype tool implementation.
Ernest TenienteEmail:
  相似文献   
120.
BACKGROUND: Numerous treatment strategies have been tried with the aim of improving results for patients with intermediate-grade lymphomas (IGL) over those achieved with cyclophosphamide, doxorubicin, vincristine, prednisone, and bleomycin (CHOP-Bleo), and numerous prognostic models have been developed to identify and separate risk groups. This study reports on a new protocol for Ann Arbor Stages II-IV IGL that consists of CHOP-Bleo alternated with a new regimen of cyclophosphamide, methotrexate, etoposide, and dexamethasone (CMED) and radiation therapy and demonstrates the usefulness of prognostic models for identifying risk groups and comparing treatment programs. METHODS: One hundred seventy patients with Ann Arbor Stages II-IV IGL were treated with alternating cycles of CHOP-Bleo and CMED for a total of 12 cycles. Involved field radiation therapy was interspersed with courses of chemotherapy for patients with Stage II and Stage III disease. Results were analyzed and compared with those of the authors' previous study of CHOP-Bleo and radiation therapy using the Ann Arbor staging system, their earlier prognostic model, and the recently published International Index. RESULTS: A complete remission occurred in 78% of the patients. The overall 5-year survival rate was 67%. Survival was better for patients with Ann Arbor Stage II disease (80%) than for those with Stage III or Stage IV (67% and 58%, respectively). High tumor burden, above-normal levels of serum lactic dehydrogenase, serum beta 2-microglobulin, and Ann Arbor Stage IV disease were adverse factors. The International Index and the authors' earlier prognostic model separated four prognostic groups. CHOP-Bleo/CMED was generally well tolerated. Neutropenic fever was the major complication that occurred in 25 patients during treatment. Six of these patients died of sepsis. CONCLUSIONS: This study demonstrated that CHOP-Bleo/CMED is a well-tolerated regimen that produced better results than those reported for a former study that used CHOP-Bleo alone. Further, results for CHOP-Bleo/CMED compared favorably with those of other second- and third-generation regimens. The study also validated the usefulness of prognostic models and, in particular, the new International Index for identifying risk groups.  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