全文获取类型
收费全文 | 65601篇 |
免费 | 6832篇 |
国内免费 | 3648篇 |
学科分类
工业技术 | 76081篇 |
出版年
2024年 | 261篇 |
2023年 | 1156篇 |
2022年 | 2086篇 |
2021年 | 3089篇 |
2020年 | 2343篇 |
2019年 | 1829篇 |
2018年 | 2152篇 |
2017年 | 2255篇 |
2016年 | 2010篇 |
2015年 | 2748篇 |
2014年 | 3504篇 |
2013年 | 4184篇 |
2012年 | 4684篇 |
2011年 | 4904篇 |
2010年 | 4516篇 |
2009年 | 4031篇 |
2008年 | 4080篇 |
2007年 | 3828篇 |
2006年 | 3565篇 |
2005年 | 2989篇 |
2004年 | 2135篇 |
2003年 | 1925篇 |
2002年 | 1989篇 |
2001年 | 1760篇 |
2000年 | 1354篇 |
1999年 | 1347篇 |
1998年 | 1001篇 |
1997年 | 807篇 |
1996年 | 740篇 |
1995年 | 608篇 |
1994年 | 493篇 |
1993年 | 331篇 |
1992年 | 310篇 |
1991年 | 221篇 |
1990年 | 161篇 |
1989年 | 141篇 |
1988年 | 97篇 |
1987年 | 69篇 |
1986年 | 54篇 |
1985年 | 44篇 |
1984年 | 38篇 |
1983年 | 38篇 |
1982年 | 28篇 |
1981年 | 25篇 |
1980年 | 26篇 |
1979年 | 17篇 |
1978年 | 14篇 |
1977年 | 14篇 |
1973年 | 15篇 |
1959年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 233 毫秒
41.
以转基因水稻中最常用的CaMV35S启动子、NOS终止子、Cry1Ab/Ac基因、HPT基因及SPS水稻内标基因为研究对象,利用5 种不同的荧光信号(FAM、HEX、Taxas Red、Cy5、Cy5.5)进行多重实时聚合酶链式反应(real-time polymerase chain reaction,real-time PCR)检测方法的研究。通过引物组合筛选、反应体系优化、特异性测试、灵敏度测试、适用性测试等一系列实验,建立了5 重real-time PCR方法,灵敏度可达0.032%。此方法具有灵敏度高、结果准确、通量大等优点,可实现水稻中转基因成分的快速、高效检测。 相似文献
42.
43.
Zhuo Wang Haonan Chen Tian Wang Yujia Xiao Wenwen Nian Jiahao Fan 《Journal of the European Ceramic Society》2018,38(11):3847-3852
The appearance of colossal permittivity materials broadened the choice of materials for energy-storage applications. In this work, colossal permittivity in ceramics of TiO2 co-doped with niobium and europium ions ((Eu0.5Nb0.5)xTi1-xO2 ceramics) was reported. A large permittivity (εr ~ 2.01?×?105) and a low dielectric loss (tanδ ~ 0.095) were observed for (Eu0.5Nb0.5)xTi1-xO2 (x?=?1%) ceramics at 1?kHz. Moreover, two significant relaxations were observed in the temperature dependence of dielectric properties for (Eu, Nb) co-doped TiO2 ceramics, which originated from defect dipoles and electron hopping, respectively. The low dielectric loss and high relative permittivity were ascribed to the electron-pinned defect-dipoles and electrons hopping. The (Eu0.5Nb0.5)xTi1-xO2 ceramic with great colossal permittivity is one of the most promising candidates for high-energy density storage applications. 相似文献
44.
45.
Qun Ren Haijun Su Jun Zhang Haifang Liu Weidan Ma Guangrao Fan Di Zhao Min Guo Lin Liu Hengzhi Fu 《Ceramics International》2019,45(6):6632-6638
Directionally solidified microstructures of Al2O3-Er3Al5O12 eutectic and off-eutectic in situ composite ceramics were explored under abrupt-change pulling rate conditions. Corresponding temperature distributions and interface locations were studied. In eutectic composition, fluctuation of eutectic spacing occurred when the pulling rate increased abruptly. A gradually increase or abrupt increase in eutectic spacing was observed when the pulling rate decreased abruptly. In hypoeutectic and hypereutectic compositions, formation of the primary phases were suppressed when the pulling rate increased abruptly from 10?µm/s to 100?µm/s, while primary phases precipitated when the pulling rate decreased abruptly from 100?µm/s to 10?µm/s. The interface altitude decreased after the pulling rate increased abruptly, but increased after the pulling rate decreased abruptly. The liquid composition restriction (around the eutectic composition) at the eutectic interface plays an important role in the suppression of the primary dendrite and coupled eutectic oxides can be obtained in off-eutectic compositions even under higher solidification rate conditions. 相似文献
46.
Journal of Computer Science and Technology - New non-volatile memory (NVM) technologies are expected to replace main memory DRAM (dynamic random access memory) in the near future. NAND flash... 相似文献
47.
In the early design stage, automotive modeling should both meet the requirements of aesthetics and engineering. Therefore, a vehicle CAD (computer aided design) model that can be easily adjusted by feedbacks is necessary. Based on CE-Bézier surface, this paper presents a set of algorithms for parametric segmentation and fairing surface generation in a car model. This model is defined by a simplified automotive template and relevant control points, shape parameters and segmentation parameters, which can be modified to alter the car form efficiently. With this model and the corresponding adjustment method, more than fifty various vehicle models are established in this research according to different parameters. And two methods for calculating similarity index between car models are constructed, which are suitable for brand design trend analysis and modelling design decisionmaking. 相似文献
48.
Tingen Zhu Wenping Li Qiqing Wang Yanbo Hu Kaifang Fan Jiafa Du 《Mine Water and the Environment》2020,39(1):57-67
A method to calculate the height of a water-conducting fractured zone (HWCFZ) was developed based on the plate and shell theory, and the development of the HWCFZ in bedrock and Q2l loess strata is discussed in detail. First, the subsidence-deflection curve equation of the overlying stratum is theoretically derived, and then the ultimate deflection and free space height of rock strata are calculated. Moreover, the strata tensile strain is calculated by using integral calculus. In addition, the failure state of the rock is analyzed by comparing the theoretically calculated tensile strain with the experimentally measured yield tensile strain, allowing one to attain the maximum value of HWCFZ. This approach was tested at the Jinjitan coal mine; the theoretically predicted, experimentally measured, and numerically computed maximum HWCFZ values were 189.5, 187.3, and 188.5 m, respectively, demonstrating the accuracy of the proposed method. These results are highly significant for safe and environment-friendly coal mining in northwest Shaanxi, China. 相似文献
50.
The application of deep learning in the field of object detection has
experienced much progress. However, due to the domain shift problem, applying an
off-the-shelf detector to another domain leads to a significant performance drop. A
large number of ground truth labels are required when using another domain to train
models, demanding a large amount of human and financial resources. In order to avoid
excessive resource requirements and performance drop caused by domain shift, this
paper proposes a new domain adaptive approach to cross-domain vehicle detection. Our
approach improves the cross-domain vehicle detection model from image space and
feature space. We employ objectives of the generative adversarial network and cycle
consistency loss for image style transfer in image space. For feature space, we align
feature distributions between the source domain and the target domain to improve the
detection accuracy. Experiments are carried out using the method with two different
datasets, proving that this technique effectively improves the accuracy of vehicle
detection in the target domain. 相似文献