全文获取类型
收费全文 | 36115篇 |
免费 | 4424篇 |
国内免费 | 2118篇 |
专业分类
电工技术 | 3073篇 |
技术理论 | 5篇 |
综合类 | 4009篇 |
化学工业 | 2970篇 |
金属工艺 | 584篇 |
机械仪表 | 1321篇 |
建筑科学 | 4804篇 |
矿业工程 | 1809篇 |
能源动力 | 1700篇 |
轻工业 | 3337篇 |
水利工程 | 2940篇 |
石油天然气 | 1905篇 |
武器工业 | 521篇 |
无线电 | 2629篇 |
一般工业技术 | 3043篇 |
冶金工业 | 1812篇 |
原子能技术 | 395篇 |
自动化技术 | 5800篇 |
出版年
2024年 | 93篇 |
2023年 | 592篇 |
2022年 | 1124篇 |
2021年 | 1378篇 |
2020年 | 1411篇 |
2019年 | 1223篇 |
2018年 | 1231篇 |
2017年 | 1345篇 |
2016年 | 1728篇 |
2015年 | 1598篇 |
2014年 | 2532篇 |
2013年 | 2884篇 |
2012年 | 2735篇 |
2011年 | 3094篇 |
2010年 | 2280篇 |
2009年 | 2165篇 |
2008年 | 2020篇 |
2007年 | 2294篇 |
2006年 | 2066篇 |
2005年 | 1681篇 |
2004年 | 1331篇 |
2003年 | 1116篇 |
2002年 | 886篇 |
2001年 | 684篇 |
2000年 | 524篇 |
1999年 | 475篇 |
1998年 | 375篇 |
1997年 | 293篇 |
1996年 | 270篇 |
1995年 | 230篇 |
1994年 | 207篇 |
1993年 | 150篇 |
1992年 | 88篇 |
1991年 | 93篇 |
1990年 | 77篇 |
1989年 | 65篇 |
1988年 | 66篇 |
1987年 | 36篇 |
1986年 | 41篇 |
1985年 | 17篇 |
1984年 | 27篇 |
1983年 | 23篇 |
1982年 | 18篇 |
1981年 | 8篇 |
1980年 | 14篇 |
1979年 | 8篇 |
1975年 | 4篇 |
1965年 | 14篇 |
1961年 | 5篇 |
1959年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
《Energy Policy》2015
With U.S. geothermal power production expected to more than triple by 2040, and the majority of this growth expected to occur in arid and water-constrained areas, it is imperative that decision-makers understand the potential long-term limitations to and tradeoffs of geothermal development due to water availability. To this end, water consumption data, including documentation triggered by the National Environmental Policy Act (NEPA) of 1969, production and injection data, and water permit data, were collected from state and federal environmental policy sources in an effort to determine water consumption across the lifecycle of geothermal power plants. Values extracted from these sources were analyzed to estimate water usage during well drilling; to identify sourcing of water for well drilling, well stimulation, and plant operations; and to estimate operational water usage at the plant level. Nevada data were also compared on a facility-by-facility basis with other publicly available water consumption data, to create a complete picture of water usage and consumption at these facilities. This analysis represents a unique method of capturing project-level water data for geothermal projects; however, a lack of statutory and legal requirements for such data and data quality result in significant data gaps, which are also explored. 相似文献
72.
Greenish yellow organic light-emitting diodes (GYOLEDs) have steadily attracted researcher's attention since they are important to our life. However, their performance significantly lags behind compared with the three primary colors based OLEDs. Herein, for the first time, an ideal host-guest system has been demonstrated to accomplish high-performance phosphorescent GYOLEDs, where the guest concentration is as low as 2%. The GYOLED exhibits a forward-viewing power efficiency of 57.0 lm/W at 1000 cd/m2, which is the highest among GYOLEDs. Besides, extremely low efficiency roll-off and voltages are achieved. The origin of the high performance is unveiled and it is found that the combined mechanisms of host-guest energy transfer and direct exciton formation on the guest are effective to furnish the greenish yellow emission. Then, by dint of this ideal host-guest system, a simplified but high-performance hybrid white OLED (WOLED) has been developed. The WOLED can exhibit an ultrahigh color rendering index (CRI) of 92, a maximum total efficiency of 27.5 lm/W and a low turn-on voltage of 2.5 V (1 cd/m2), unlocking a novel avenue to simultaneously achieve simplified structure, ultrahigh CRI (>90), high efficiency and low voltage. 相似文献
73.
Large lectures are the predominant way of teaching first-year students at universities in Norway. However, this forum for education is seldom discussed as a context for a formative feedback practice. The purpose of this sequential mixed methods study was to address whether and how a student-response system can open for a formative feedback practice in lectures and thereby support students' ability to monitor their own learning, as well as supply insight into how students engage with the feedback in their course work. The context for the study was large lectures (150–200 students) in a qualitative method course for first-year psychology students. Findings from the survey (n = 149) showed a positive correlation between the extent to which students report that they use clickers to monitor their own learning, and the extent to which they report that they used the feedback in their own course work. However, findings indicate that students valued the process of monitoring their own learning during the lectures to a greater extent than they actually used the feedback in their course work. Findings from interviews (n = 6) illustrated various ways students applied feedback in their course work. 相似文献
75.
《Calphad》2021
The Ag–Cu phase diagram at nanoscale was reassessed by CALculation of PHAse Diagrams (CALPHAD) method, considering the surface effect on the chemical potential of pure substance and excess Gibbs free energy of mixtures. According to the reported thermodynamic properties of pure Ag and Cu nanoparticles (NPs), and the measured melting eutectic temperatures of Ag8Cu2, Ag7Cu3, Ag6Cu5 to Ag5Cu5 NPs, respectively, obtained in the previous works, self-consistent thermodynamic parameters including the size effect were obtained by thermodynamic optimization. Using the obtained thermodynamic parameters, four Ag–Cu nano phase diagrams were constructed, and thermodynamic properties were calculated. It was indicated that the calculated Ag–Cu nano phase diagrams agreed well with experimental data. 相似文献
76.
Jaruneth Petchoo Sitima Jittinandana Siriporn Tuntipopipat Chitraporn Ngampeerapong Nattapol Tangsuphoom 《International Journal of Food Science & Technology》2021,56(4):1750-1758
This study determined the physicochemical, sensorial and nutritional properties of breadsticks to which a resistant starch (RS)-rich ingredient was incorporated by partial substitution, that is, 40%–70%, of hard wheat flour in the control recipe. Wheat flour substitution at the levels exceeding 50% lightened the colour while decreasing the moisture content and hardness of breadsticks, which was explainable by the microstructure. Changes in properties of breadsticks also affected the suitability of its sensory attributes, particularly colour and texture. Breadsticks, of which half of wheat flour was substituted, contained less protein and calories but higher carbohydrate than the control formula. Such flour substitution increased RS content closed to its effective dose of 15 g in a 45-g serving, which led to approximately 15% reduction in in vitro glycaemic index. Therefore, incorporating effective dose of RS in breadsticks could be performed, without causing substantial changes in product quality, by partial substitution of wheat flour. 相似文献
77.
专利规避设计需从现有专利中遴选具有核心竞争力的目标专利,以提升技术起点。针对设计领域的海量专利信息,提出了专利质量多指标主客观综合评价模型。分析专利书目信息与专利质量存在的正相关关系,甄选存活期、权利项数、同族专利数、引证数和被引证数等书目信息指标,构建了专利质量多指标综合评价指标体系,提升了评价方法的科学性和可操作性;提出将德尔菲法、层次分析法和均方差决策法相结合的主客观赋权法,确定专利质量评价指标权重,既保证了评价的权威性,又减小了个人偏见与从众妥协等因素的影响;建立了基于质量评价模型遴选目标专利的过程模型,并通过应用实例验证了该模型对遴选具有核心竞争力专利的有效性。 相似文献
78.
79.
Robert Bertuzzi 《岩石力学与岩土工程学报(英文版)》2019,11(3):494-510
This paper presents the results of ongoing research carried out by the author exploring methods to provide a more robust estimate of rock mass properties specifically for use in tunnel design. Data from various large-scale rock mass failures are introduced, including coal pillars. The damage-initiation,spalling-limit approach is compared to the coal pillar database. New comparisons of estimating the geological strength index(GSI) and relationships to estimate the Hoeke Brown failure criterion parameters, mb, s and a, are presented. 相似文献
80.
为准确评价尾矿库的安全等级,以黄金洞尾矿库为例,分析影响尾矿库安全的各因素之间的关系,综合运用模糊多元联系度理论与层次分析法(AHP),建立了包含5个影响因素和26个影响因子的尾矿库综合安全评价模型。由AHP得出各项主、客观指标的权重系数,引入模糊多元联系度理论,综合考虑确定性与不确定性因素,处理综合集成问题,构造隶属函数量化指标的实测值。结果表明:黄金洞尾矿库安全等级为Ⅱ级,尾矿库处于较稳定状态。经比较不确定性因素大小,得出尾矿排放(B3)>尾矿坝(B2)>安全管理(B1)>尾矿输送与回水(B5)>排洪系统(B4),说明尾矿排放指标的不确定性因素最大,需对尾矿排放加强管理。该模型得到的评价结果与实际结果相吻合,为尾矿库安全性评价提供了一种可行的方法。 相似文献