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   30720篇
  免费   2942篇
  国内免费   1531篇
电工技术   1964篇
综合类   2359篇
化学工业   4800篇
金属工艺   1805篇
机械仪表   1907篇
建筑科学   2478篇
矿业工程   964篇
能源动力   767篇
轻工业   2889篇
水利工程   603篇
石油天然气   1795篇
武器工业   250篇
无线电   3384篇
一般工业技术   3440篇
冶金工业   1392篇
原子能技术   371篇
自动化技术   4025篇
  2024年   85篇
  2023年   547篇
  2022年   841篇
  2021年   1264篇
  2020年   1020篇
  2019年   816篇
  2018年   873篇
  2017年   1009篇
  2016年   803篇
  2015年   1234篇
  2014年   1638篇
  2013年   1870篇
  2012年   2025篇
  2011年   2182篇
  2010年   1986篇
  2009年   1955篇
  2008年   1838篇
  2007年   1766篇
  2006年   1879篇
  2005年   1742篇
  2004年   1131篇
  2003年   891篇
  2002年   946篇
  2001年   755篇
  2000年   718篇
  1999年   633篇
  1998年   522篇
  1997年   447篇
  1996年   385篇
  1995年   330篇
  1994年   268篇
  1993年   167篇
  1992年   133篇
  1991年   113篇
  1990年   85篇
  1989年   76篇
  1988年   62篇
  1987年   34篇
  1986年   30篇
  1985年   14篇
  1984年   16篇
  1983年   12篇
  1982年   12篇
  1981年   12篇
  1980年   11篇
  1979年   4篇
  1977年   2篇
  1974年   4篇
  1959年   1篇
  1951年   2篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Food Science and Biotechnology - Various hilling materials (rice hulls, pine sawdust, and perlite) were compared to produce sprout vegetables using beach silvertop (Glehnia littoralis Fr. Schm. ex...  相似文献   
2.
挥发酸的控制是荔枝酒的生产过程中的重要技术瓶颈,发酵过程易造成荔枝果酒挥  相似文献   
3.
熊建 《建筑技术开发》2021,48(18):146-148
基坑开挖对于建筑工程项目建设非常重要,工程建设中对基坑周围建筑物基础稳定性及安全性产生影响.为提高建筑建设质量及保障人民群众生命财产安全,对实际基坑开挖作业做了调查,进行了深入研究,尤其对建筑物基础安全性产生的影响进行了分析,以期为施工人员进行施工作业提供可靠依据.  相似文献   
4.
Endoplasmic reticulum (ER) stress response is an adaptive program to cope with cellular stress that disturbs the function and homeostasis of ER, which commonly occurs during cancer progression to late stage. Late-stage cancers, mostly requiring chemotherapy, often develop treatment resistance. Chemoresistance has been linked to ER stress response; however, most of the evidence has come from studies that correlate the expression of stress markers with poor prognosis or demonstrate proapoptosis by the knockdown of stress-responsive genes. Since ER stress in cancers usually persists and is essentially not induced by genetic manipulations, we used low doses of ER stress inducers at levels that allowed cell adaptation to occur in order to investigate the effect of stress response on chemoresistance. We found that prolonged tolerable ER stress promotes mesenchymal–epithelial transition, slows cell-cycle progression, and delays the S-phase exit. Consequently, cisplatin-induced apoptosis was significantly decreased in stress-adapted cells, implying their acquisition of cisplatin resistance. Molecularly, we found that proliferating cell nuclear antigen (PCNA) ubiquitination and the expression of polymerase η, the main polymerase responsible for translesion synthesis across cisplatin-DNA damage, were up-regulated in ER stress-adaptive cells, and their enhanced cisplatin resistance was abrogated by the knockout of polymerase η. We also found that a fraction of p53 in stress-adapted cells was translocated to the nucleus, and that these cells exhibited a significant decline in the level of cisplatin-DNA damage. Consistently, we showed that the nuclear p53 coincided with strong positivity of glucose-related protein 78 (GRP78) on immunostaining of clinical biopsies, and the cisplatin-based chemotherapy was less effective for patients with high levels of ER stress. Taken together, this study uncovers that adaptation to ER stress enhances DNA repair and damage tolerance, with which stressed cells gain resistance to chemotherapeutics.  相似文献   
5.
Neural Processing Letters - Raman spectroscopy is often used for the composition determination and rapid classification of materials because it can reflect the molecular information of materials....  相似文献   
6.
Science China Technological Sciences - Accurate modelling of lithium ion batteries is crucial for battery management in electric vehicles. Recent studies have revealed the fractional order nature...  相似文献   
7.
Despite recent rapid advances in metal halide perovskites for use in optoelectronics, the fundamental understanding of the electrical-poling-induced ion migration, accounting for many unusual attributes and thus performance in perovskite-based devices, remain comparatively elusive. Herein, the electrical-poling-promoted polarization potential is reported for rendering hybrid organic–inorganic perovskite photodetectors with high photocurrent and fast response time, displaying a tenfold enhancement in the photocurrent and a twofold decrease in the response time after an external electric field poling. First, a robust meniscus-assisted solution-printing strategy is employed to facilitate the oriented perovskite crystals over a large area. Subsequently, the electrical poling invokes the ion migration within perovskite crystals, thus inducing a polarization potential, as substantiated by the surface potential change assessed by Kelvin probe force microscopy. Such electrical-poling-induced polarization potential is responsible for the markedly enhanced photocurrent and largely shortened response time. This work presents new insights into the electrical-poling-triggered ion migration and, in turn, polarization potential as well as into the implication of the latter for optoelectronic devices with greater performance. As such, the utilization of ion-migration-produced polarization potential may represent an important endeavor toward a wide range of high-performance perovskite-based photodetectors, solar cells, transistors, scintillators, etc.  相似文献   
8.
A first‐principles‐based effective Hamiltonian is developed and employed to investigate finite‐temperature structural properties of a prototype of perovskite halides, that is CsPbI3. Such simulations, when using first‐principles‐extracted coefficients, successfully reproduce the existence of an orthorhombic Pnma state and its iodine octahedral tilting angles around room temperature. However, they also yield a direct transformation from Pnma to cubic P m 3 ¯ m upon heating, unlike measurements that reported the occurrence of an intermediate long‐range‐tilted tetragonal P4/mbm phase in‐between the orthorhombic and cubic phases. Such disagreement, which may cast some doubts about the extent to which first‐principle methods can be trusted to mimic hybrid perovskites, can be resolved by “only” changing one short‐range tilting parameter in the whole set of effective Hamiltonian coefficients. In such a case, some reasonable values of this specific parameter result in the predictions that i) the intermediate P4/mbm state originates from fluctuations over many different tilted states; and ii) the cubic P m 3 ¯ m phase is highly locally distorted and develops strong transverse antiphase correlation between first‐nearest neighbor iodine octahedral tiltings, before undergoing a phase transition to P4/mbm under cooling.  相似文献   
9.
济阳坳陷下古生界潜山油气藏特征及成藏模式   总被引:1,自引:1,他引:0  
济阳坳陷下古生界潜山具有多样性、复杂性的特点,潜山差异性的形成演化、油气成藏主控因素和控藏模式不明确,严重制约了该区潜山油气勘探。在潜山分类的基础上,综合利用系统恢复、分类对比和典型解剖等方法,揭示了济阳坳陷下古生界不同类型潜山的形成演化过程和油气成藏主控因素差异性,分类建立了油气成藏模式。研究表明,济阳坳陷下古生界主要发育高位新盖侵蚀残丘潜山、中位古盖拉张断块潜山、中位新古盖拉张剪切断块潜山、中位中古盖挤压拉张断块潜山和低位古盖拉张滑脱断块潜山5种潜山类型。不同类型潜山的形成演化和油气成藏各具特色,其中,高位新盖侵蚀残丘潜山的发育受隆升、侵蚀作用控制,油气成藏主要受控于油源和盖层条件,表现为"单向供烃、砂体-不整合岩溶体联合输导、残丘控藏"的成藏模式;中位古盖拉张断块潜山的发育受掀斜、断裂作用控制,油气成藏主要受控于储集条件,表现为"单向供烃、顺向断层输导、反向断层控藏"的成藏模式;中位新古盖拉张剪切断块潜山的发育受反转、翘倾和走滑切割作用控制,油气成藏主要受控于输导条件,表现为"多源供烃、断溶体立体输导、断裂控藏"的成藏模式;中位中古盖挤压拉张断块潜山的形成受强烈挤压、拉张滑脱作用控制,油气成藏主要受控于储集条件,表现为"多源供烃、断缝体输导、断褶控藏"的成藏模式;低位古盖拉张滑脱断块潜山的形成受强烈拉张滑脱作用控制,油气成藏主要受控于输导条件,表现为"顶部供烃、断缝体输导、断裂控藏"的成藏模式。  相似文献   
10.
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