全文获取类型
收费全文 | 25299篇 |
免费 | 2206篇 |
国内免费 | 831篇 |
专业分类
电工技术 | 1359篇 |
技术理论 | 1篇 |
综合类 | 1383篇 |
化学工业 | 4511篇 |
金属工艺 | 1329篇 |
机械仪表 | 1390篇 |
建筑科学 | 1869篇 |
矿业工程 | 578篇 |
能源动力 | 923篇 |
轻工业 | 1649篇 |
水利工程 | 342篇 |
石油天然气 | 1349篇 |
武器工业 | 118篇 |
无线电 | 3176篇 |
一般工业技术 | 3264篇 |
冶金工业 | 1441篇 |
原子能技术 | 347篇 |
自动化技术 | 3307篇 |
出版年
2024年 | 247篇 |
2023年 | 437篇 |
2022年 | 716篇 |
2021年 | 1041篇 |
2020年 | 737篇 |
2019年 | 678篇 |
2018年 | 723篇 |
2017年 | 828篇 |
2016年 | 777篇 |
2015年 | 941篇 |
2014年 | 1251篇 |
2013年 | 1594篇 |
2012年 | 1574篇 |
2011年 | 1723篇 |
2010年 | 1397篇 |
2009年 | 1443篇 |
2008年 | 1342篇 |
2007年 | 1238篇 |
2006年 | 1349篇 |
2005年 | 1163篇 |
2004年 | 841篇 |
2003年 | 758篇 |
2002年 | 759篇 |
2001年 | 541篇 |
2000年 | 522篇 |
1999年 | 601篇 |
1998年 | 572篇 |
1997年 | 462篇 |
1996年 | 446篇 |
1995年 | 345篇 |
1994年 | 280篇 |
1993年 | 191篇 |
1992年 | 174篇 |
1991年 | 117篇 |
1990年 | 92篇 |
1989年 | 72篇 |
1988年 | 89篇 |
1987年 | 48篇 |
1986年 | 44篇 |
1985年 | 25篇 |
1984年 | 33篇 |
1983年 | 19篇 |
1982年 | 27篇 |
1981年 | 12篇 |
1980年 | 10篇 |
1979年 | 15篇 |
1977年 | 4篇 |
1976年 | 9篇 |
1975年 | 4篇 |
1965年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
As part of the NJ Toxics Reduction Workplan for NY/NJ Harbor, ambient water samples were collected at 15 locations along the tidal portions of the Hackensack, Passaic, Raritan, Rahway and Elizabeth Rivers, and in Newark Bay, the Arthur Kill, and Kill van Kull. A Trace Organics Platform Sampler was used to collect a total of 73 dissolved phase and 73 suspended sediment phase samples between June 2000 and May 2002. These samples were analyzed for spatial and wet versus dry weather trends in the 114 polychlorinated biphenyls (PCBs; modified USEPA Method 1668A). Mean total PCB concentrations at the sampling locations ranged between 3.45 and 56 ng/L. PCB homolog groups distribution patterns at the sampling locations are presented. 相似文献
102.
103.
104.
Neural Processing Letters - Segmentation of retinal vessels in fundus images plays a very important role in diagnosing relevant diseases. In this paper, we have constructed automated segmentation... 相似文献
105.
Jia-Liang Chen Xiao Wang Yu-Hao Xiao Xun-Cheng Su 《Chembiochem : a European journal of chemical biology》2019,20(21):2738-2742
Unstable and low-abundance protein complexes represent a large family of transient protein complexes that are difficult to characterize, even by means of high-resolution NMR spectroscopy. A method to assign the NMR signals of these unstable complexes through a combination of selective isotope labeling of amino acids in a protein and site-specific labeling the protein with a paramagnetic tag is presented herein. By using this method, the resonances of unstable thioester intermediate complex (lifetime <5 h and highest concentration ≈20 μm ) generated by Staphylococcus aureus sortase A and its peptide substrate under a real-time reaction have been assigned. 相似文献
106.
107.
Dr. Ma Su Dr. Yan Shi Minghui Wang Ruixuan Gao Jianfeng Wu Hai Xu Chuanwu Xi Prof. Jianfeng Cai 《ChemMedChem》2019,14(23):1963-1967
Host Defense Peptides (HDPs) have gained considerable interest due to the omnipresent threat of bacterial infection as a serious public health concern. However, development of HDPs is impeded by several drawbacks, such as poor selectivity, susceptibility to proteolytic degradation, low-to-moderate activity and requiring complex syntheses. Herein we report a class of lipo-linear α/urea-γ-AApeptides with a hybrid backbone and low molecular weight. The heterogeneous backbone not only enhances chemodiversity, but also shows effective antimicrobial activity against Gram-positive bacteria and is capable of disrupting bacterial membranes and killing bacteria rapidly. Given their low molecular weight and ease of access via facile synthesis, they could be practical antibiotic agents. 相似文献
108.
Chung Gi Baig Young Ho Chun Eun Su Cho Chang Kyun Choi 《Korean Journal of Chemical Engineering》2000,17(2):169-173
When air is injected into silicone oil contained in a horizontal Hele-Shaw cell, a single air bubble forms and grows showing various interesting phenomena. In this study the effects of the bubble front velocity, air injection velocity at a nozzle, fluid properties and cell depth on the stability of the growing bubble were investigated experimentally. By using the modified capillary number involving the aspect ratio, we obtained the onset conditions of the unstable bubble. Also, the bubble width was analyzed both quantitatively and qualitatively. Before the bubble experiences splitting, the bubble front velocity is almost proportional to the air injection velocity. Therefore the latter velocity may be used in a practical sense. 相似文献
109.
Photo-assisted one-step electrodeposition has been applied to help in forming smooth and dense CuInSe2 films. The difference in surface morphology and crystalline quality between CuInSe2 films with various photo-assistance has been investigated. In the photo-assisted electrodeposition process, the many kinds of lamps providing maximum light intensity at about 380 to 620 nm were used as light source to be irradiated onto the surface of Mo-coated soda-lime glass substrates. The results suggested effects of photo-assistance including activating surface diffusion and growing high-crystalline quality films with reduced defects during electrodeposition. 相似文献
110.
Bi-Ru Wu Zhi-Quan Huang Wan-Sheng Su Yun-Yi Hsieh Feng-Chuan Chuang 《Diamond and Related Materials》2010,19(11):1341-1347
Structural motifs for the BC2N superlattices were identified from a systematic search based on a greedy algorithm. Using a tree data structure, we have retrieved seven structural models for c-BC2N 1 × 1 × 1 lattice which were identified previously by Sun et al. [Phys. Rev. B 64, 094108 (2001)]. Furthermore, the atomic structures with the maximum number of C–C bonds for c-BC2N 2 × 2 × 2, 3 × 3 × 3, and 4 × 4 × 4 superlattices were found by imposing the greedy algorithm in the tree data structure. This new structural motif has not been previously proposed in the literature. A total of up to 512 atoms in the c-BC2N superlattice are taken into consideration. The atoms in these superlattices are in diamond-like structural form. Furthermore, the C atoms, as well as B and N atoms, form the octahedral motif separately. The octahedral structure consisting of C is bounded with {111} facets, and each facet is interfaced to a neighboring octahedral structure consisting of B and N atoms. The electronic and mechanical properties of newly identified low energy structures were analyzed. 相似文献