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   38699篇
  免费   1477篇
  国内免费   119篇
电工技术   414篇
综合类   234篇
化学工业   6120篇
金属工艺   740篇
机械仪表   811篇
建筑科学   1025篇
矿业工程   94篇
能源动力   1106篇
轻工业   4102篇
水利工程   243篇
石油天然气   157篇
武器工业   8篇
无线电   3001篇
一般工业技术   5097篇
冶金工业   12765篇
原子能技术   298篇
自动化技术   4080篇
  2024年   54篇
  2023年   191篇
  2022年   541篇
  2021年   863篇
  2020年   625篇
  2019年   718篇
  2018年   830篇
  2017年   897篇
  2016年   912篇
  2015年   704篇
  2014年   1056篇
  2013年   1677篇
  2012年   1509篇
  2011年   1912篇
  2010年   1405篇
  2009年   1467篇
  2008年   1332篇
  2007年   1117篇
  2006年   917篇
  2005年   958篇
  2004年   1015篇
  2003年   932篇
  2002年   880篇
  2001年   769篇
  2000年   611篇
  1999年   814篇
  1998年   4299篇
  1997年   2601篇
  1996年   1745篇
  1995年   1028篇
  1994年   812篇
  1993年   946篇
  1992年   268篇
  1991年   343篇
  1990年   296篇
  1989年   247篇
  1988年   265篇
  1987年   218篇
  1986年   218篇
  1985年   217篇
  1984年   132篇
  1983年   112篇
  1982年   141篇
  1981年   152篇
  1980年   176篇
  1979年   96篇
  1978年   90篇
  1977年   279篇
  1976年   505篇
  1975年   98篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
International Journal of Computer Vision - Semantic scene completion (SSC) aims to jointly estimate the complete geometry and semantics of a scene, assuming partial sparse input. In the last years...  相似文献   
102.
Biologically and environmentally resorbable electronic devices support application possibilities that cannot be addressed with conventional technologies. This paper presents highly conductive, water-soluble composites that can be printed to form contacts, interconnects, antennas, and other important features that are essential to nearly all systems of this type. An optimized material formulation involves in situ polymerization to yield a polyanhydride containing a dispersion of molybdenum microparticles at appropriate concentrations. Comparisons of essential physical and electrical properties of these materials to those of composites formed with other polymers and other metal microparticles reveal the relevant considerations. Various functional demonstrations of screen-printed test structures and devices illustrate the suitability of these conductive inks for use in water-soluble electronic devices. A key advantage of the material introduced here compared to alternatives is its ability to maintain conductance over significant periods of time while immersed in relevant aqueous solutions. Studies involving live animal models establish the biocompatibility.  相似文献   
103.
104.
There is growing evidence that face recognition is "special" but less certainty concerning the way in which it is special. The authors review and compare previous proposals and their own more recent hypothesis, that faces are recognized "holistically" (i.e., using relatively less part decomposition than other types of objects). This hypothesis, which can account for a variety of data from experiments on face memory, was tested with 4 new experiments on face perception. A selective attention paradigm and a masking paradigm were used to compare the perception of faces with the perception of inverted faces, words, and houses. Evidence was found of relatively less part-based shape representation for faces. The literatures on machine vision and single unit recording in monkey temporal cortex are also reviewed for converging evidence on face representation. The neuropsychological literature is reviewed for-evidence on the question of whether face representation differs in degree or kind from the representation of other types of objects.  相似文献   
105.
Although enthusiasm for measuring health-related quality of life (HRQL) in clinical trials exists, information is limited on the meaning of scores. We examined the relation between scores from the 34-item Medical Outcomes Study HIV Health Survey (MOS-HIV) and the more detailed HIV Overview of Problems-Evaluation System (HOPES) using the responses of 318 HIV-infected outpatients being treated in Los Angeles and Baltimore. With the HOPES problem statements as independent variables, statistically significant predictors of the variation in MOS-HIV scores for the Physical Function, Mental Health, and Energy/Fatigue scales were identified using stepwise regression. Approximately 60% to 70% of the variation in each of the scores was explained by five to seven different HOPES problem statements, with a single item explaining 47% to 59% of the variation. We created illustrative profiles for each of the three MOS-HIV scales using the HOPES items identified in the regressions. Independent of the scale, persons scoring in the top MOS-HIV quartile tended to report few if any problems, whereas a decline in score to the next quartile was characterized by functional difficulties (e.g., "HIV interferes with work"). The onset of specific problems might trigger further evaluation and potential intervention from health care providers to help maintain patient functioning.  相似文献   
106.
Ferromagnetic and perovskite-like thin films (<1m) of La1–xCaxMnO3+ have been routinely prepared by heat treatment of an amorphous La–Ca–Mn precursor. The precursor was electrodeposited cathodically in the absence of oxygen and water onto polished silver substrates from a nonaqueous solution of the components' nitrates. Analysis by X-ray diffraction and SQUID magnetometry shows these materials exhibit the appropriate structural and magnetic phases indicative of colossal magnetoresistance.  相似文献   
107.
108.
4. Conclusions Diastolic LV function and myocardial HEP metabolism are impaired only when LVH is caused by permanent pressure or volume overload, and not by a temporary increase in cardiac workload during part of the day as in elite athletes. Therefore, training-induced and pressure/volume-overload-induced LVH seem to represent different phenotypes of LVH, possibly related to genetic reprogramming which only occurs during permanent cardiac overload [17]. Moreover, there is an association between impaired LV diastolic function and altered myocardial HEP metabolism in patients with hypertension and in patients with aortic valve disease. Finally we did not find a correlation between myocardial HEP metabolism and LV mass in any of the groups studied. The latter indicates that LVH should be regarded as an epiphenomenon to cardiac overload, and not as a primary factor causing abnormal HEP metabolism.  相似文献   
109.
The Millimetre and Infrared Testa Grigia Observatory 2.6-m Cassegrain telescope has been designed to allow high-sensitivity observations in the millimeter spectral range. For this purpose, in order to reduce unwanted contributions from local foregrounds, we adopted a sky-chopping technique, by wobbling the telescope subreflector. We describe the design and performance of the wobbling system, which can endure external forced two and three fields square-wave modulation and includes features such as high frequency, high amplitude, high duty cycle, low microphonics, and high stability.  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