全文获取类型
收费全文 | 18022篇 |
免费 | 1682篇 |
国内免费 | 1226篇 |
专业分类
电工技术 | 407篇 |
综合类 | 1165篇 |
化学工业 | 4457篇 |
金属工艺 | 944篇 |
机械仪表 | 153篇 |
建筑科学 | 1455篇 |
矿业工程 | 1062篇 |
能源动力 | 577篇 |
轻工业 | 2848篇 |
水利工程 | 555篇 |
石油天然气 | 4581篇 |
武器工业 | 68篇 |
无线电 | 277篇 |
一般工业技术 | 1273篇 |
冶金工业 | 676篇 |
原子能技术 | 225篇 |
自动化技术 | 207篇 |
出版年
2024年 | 81篇 |
2023年 | 269篇 |
2022年 | 573篇 |
2021年 | 699篇 |
2020年 | 662篇 |
2019年 | 544篇 |
2018年 | 521篇 |
2017年 | 673篇 |
2016年 | 730篇 |
2015年 | 696篇 |
2014年 | 1064篇 |
2013年 | 1211篇 |
2012年 | 1487篇 |
2011年 | 1402篇 |
2010年 | 965篇 |
2009年 | 992篇 |
2008年 | 774篇 |
2007年 | 1071篇 |
2006年 | 1033篇 |
2005年 | 876篇 |
2004年 | 772篇 |
2003年 | 679篇 |
2002年 | 543篇 |
2001年 | 483篇 |
2000年 | 404篇 |
1999年 | 332篇 |
1998年 | 294篇 |
1997年 | 212篇 |
1996年 | 189篇 |
1995年 | 140篇 |
1994年 | 133篇 |
1993年 | 95篇 |
1992年 | 77篇 |
1991年 | 65篇 |
1990年 | 58篇 |
1989年 | 34篇 |
1988年 | 14篇 |
1987年 | 14篇 |
1986年 | 12篇 |
1985年 | 13篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1975年 | 3篇 |
1974年 | 1篇 |
1959年 | 3篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
23.
The Helimak of USA is a plasma physics experimental device designed and built by CASIPP.Its configuration of magnetic field is of very importance during the operation of this device.In this paper,the influence of magnetic permeability on configuration of magnetic field will be discussed due to the effect of weld metal in the vacuum vessel of Helimak,and some conclusion is useful for some engineering designs of the fusion experimental device. 相似文献
24.
25.
26.
27.
为探究低渗砂岩铀矿在不同因素下的产量变化情况,根据储层有效应力与渗流特性的关系,建立有效应力-渗流数值模型。通过日产水量分析流固耦合作用下储层的产量变化规律,并结合变异系数法分析注入压力、初始渗透率和井间距对产量的影响。研究表明:考虑流固耦合作用下的储层产量会更快进入稳定状态,产量更高;应力敏感性系数越大,有效应力减小对地层渗透率影响越明显。注入压力越大,地层有效应力减小区域下降幅度增大,使地层渗透率增大区域升高幅度增大,导致产量逐渐增多;流固耦合作用下产量随着初始渗透率增大而增多且增长速度较快;流固耦合作用下,随着井间距的增大,注采井间有效应力减小的影响减弱,注采井间渗透率增大趋势也在下降,导致产量逐渐降低。结合各因素变异系数变化可得,注入压力对产量效果影响更明显。本研究有助于建立完整的砂岩铀矿地浸采铀生产方案。 相似文献
28.
与传统加速器驱动次临界系统(ADS)采用金属靶作为散裂中子靶的设计不同,加速器驱动次临界熔盐堆(AD-MSRs)采用靶堆一体的设计,直接使用燃料熔盐作为散裂中子靶。由于熔盐靶的中子学性能直接影响AD MSRs的能量放大系数、核废物的嬗变和核燃料增殖的效率,所以本研究基于MCNPX程序,详细计算了高能质子轰击氟盐和氯盐两种熔盐靶产生的散裂中子产额、散裂中子能谱、能量沉积分布以及散裂产物等中子学性能,并与液态Pb和铅铋共熔体(LBE)两种液态金属靶进行了对比。计算结果表明,熔盐靶在散裂中子产额上与液态金属靶有一定的差距,但熔盐靶内能量沉积分布的梯度较小,更有利于靶区的热量导出。与液态Pb和LBE靶相比,熔盐靶的散裂产物中包含更多的气体以及高质量数的α发射体核素。 相似文献
29.
Atsushi Kanamori Fumio Tanaka Masaki Ominami Yuji Nadatani Shusei Fukunaga Koji Otani Shuhei Hosomi Noriko Kamata Yasuaki Nagami Koichi Taira Yasuhiro Fujiwara 《International journal of molecular sciences》2022,23(15)
The effects of psychological stress on eosinophilic gastrointestinal disorders have not been elucidated. This study investigated the effects of psychological stress in a mouse model of eosinophilic enteritis (EoN). BALB/c mice were treated with ovalbumin (OVA) to create an EoN model and subjected to either water avoidance stress (WAS) or sham stress (SS). Microscopic inflammation, eosinophil and mast cell counts, mRNA expression, and protein levels of type 2 helper T cell (Th2) cytokines in the ileum were compared between groups. We evaluated ex vivo intestinal permeability using an Ussing chamber. A corticotropin-releasing hormone type 1 receptor (CRH-R1) antagonist was administered before WAS, and its effects were analyzed. WAS significantly increased diarrhea occurrence and, eosinophil and mast cell counts, and decreased the villus/crypt ratio compared to those in the SS group. The mRNA expression of CRH, interleukin IL-4, IL-5, IL-13, eotaxin-1, and mast cell tryptase β2 significantly increased, and the protein levels of IL-5, IL-13, and OVA-specific immunoglobulin E (IgE) also significantly increased in the WAS group. Moreover, WAS significantly increased the intestinal permeability. The CRH-R1 antagonist significantly inhibited all changes induced by WAS. Psychological stress exacerbated ileal inflammation via the CRH-mast cell axis in an EoN mouse model. 相似文献
30.
Lu-Yu Yan Jia-Gui Guo Xin Zhang Yang Liu Xin-Xin Xiong Yu-Xuan Han Li-Li Zhang Xiao-Hong Zhang Dong-Hong Min 《International journal of molecular sciences》2022,23(13)
The peptidase M24 (Metallopeptidase 24, M24) superfamily is essential for plant growth, stress response, and pathogen defense. At present, there are few systematic reports on the identification and classification of members of the peptidase M24 proteins superfamily in wheat. In this work, we identified 53 putative candidate TaM24 genes. According to the protein sequences characteristics, these members can be roughly divided into three subfamilies: I, II, III. Most TaM24 genes are complex with multiple exons, and the motifs are relatively conserved in each sub-group. Through chromosome mapping analysis, we found that the 53 genes were unevenly distributed on 19 wheat chromosomes (except 3A and 3D), of which 68% were in triads. Analysis of gene duplication events showed that 62% of TaM24 genes in wheat came from fragment duplication events, and there were no tandem duplication events to amplify genes. Analysis of the promoter sequences of TaM24 genes revealed that cis-acting elements were rich in response elements to drought, osmotic stress, ABA, and MeJA. We also studied the expression of TaM24 in wheat tissues at developmental stages and abiotic stress. Then we selected TaM24-9 as the target for further analysis. The results showed that TaM24-9 genes strengthened the drought and salt tolerance of plants. Overall, our analysis showed that members of the peptidase M24 genes may participate in the abiotic stress response and provided potential gene resources for improving wheat resistance. 相似文献