全文获取类型
收费全文 | 7541篇 |
免费 | 450篇 |
国内免费 | 14篇 |
专业分类
电工技术 | 84篇 |
综合类 | 2篇 |
化学工业 | 1870篇 |
金属工艺 | 174篇 |
机械仪表 | 145篇 |
建筑科学 | 279篇 |
矿业工程 | 13篇 |
能源动力 | 245篇 |
轻工业 | 705篇 |
水利工程 | 75篇 |
石油天然气 | 28篇 |
武器工业 | 6篇 |
无线电 | 558篇 |
一般工业技术 | 1572篇 |
冶金工业 | 833篇 |
原子能技术 | 43篇 |
自动化技术 | 1373篇 |
出版年
2023年 | 56篇 |
2022年 | 119篇 |
2021年 | 166篇 |
2020年 | 160篇 |
2019年 | 134篇 |
2018年 | 179篇 |
2017年 | 196篇 |
2016年 | 252篇 |
2015年 | 167篇 |
2014年 | 271篇 |
2013年 | 603篇 |
2012年 | 449篇 |
2011年 | 545篇 |
2010年 | 367篇 |
2009年 | 370篇 |
2008年 | 500篇 |
2007年 | 425篇 |
2006年 | 369篇 |
2005年 | 305篇 |
2004年 | 281篇 |
2003年 | 241篇 |
2002年 | 201篇 |
2001年 | 123篇 |
2000年 | 101篇 |
1999年 | 113篇 |
1998年 | 115篇 |
1997年 | 102篇 |
1996年 | 101篇 |
1995年 | 92篇 |
1994年 | 108篇 |
1993年 | 78篇 |
1992年 | 63篇 |
1991年 | 51篇 |
1990年 | 46篇 |
1989年 | 63篇 |
1988年 | 47篇 |
1987年 | 24篇 |
1986年 | 31篇 |
1985年 | 40篇 |
1984年 | 40篇 |
1983年 | 26篇 |
1982年 | 26篇 |
1981年 | 41篇 |
1980年 | 24篇 |
1979年 | 22篇 |
1978年 | 24篇 |
1977年 | 14篇 |
1975年 | 11篇 |
1974年 | 21篇 |
1973年 | 14篇 |
排序方式: 共有8005条查询结果,搜索用时 15 毫秒
71.
Alexander Gatch Dimitry Gorsky Zy Biesinger Eric Bruestle Kelley Lee Curt Karboski Meredith L. Bartron Tyler Wagner 《Journal of Great Lakes research》2021,47(2):486-493
Restoration of a wild-produced lake trout Salvelinus namaycush population in Lake Ontario has not been successful despite the adult population often meeting or exceeding restoration targets. Lack of high-quality spawning habitat in Lake Ontario is suggested as one impediment to recruitment of wild lake trout, although the quantity and location of spawning habitat is poorly understood. If high-quality spawning habitat is limited in Lake Ontario, lake trout may be using uncommon spawning locations such as rivers. Anecdotal angler accounts point to the Niagara River as a lake trout spawning location. To better understand the potential of the Niagara River as a spawning location, egg and juvenile fish collections were conducted 12–14 river kilometers from the mouth of the Niagara River from 2010 to 2012; and mature female lake trout with surgically implanted acoustic tags were monitored from 2015 to 2019. Genetic analyses confirmed 60% of collected eggs and 93% of collected post-hatch juvenile fish in the Niagara River were lake trout. Tagged female lake trout returned to the Niagara River over consecutive years during the spawning season. The short duration of lake trout presence in the river (mean = 56 days/year) suggests female lake trout use the Niagara River primarily for spawning. Diversity in spawning locations may provide lake trout population’s resilience against environmental variability through a portfolio effect. Improved identification of riverine spawning locations, including their overall contribution to wild recruitment, may be a useful tool for managers to restore a wild-produced population of lake trout in Lake Ontario. 相似文献
72.
Wang Eric Ke Wang Fan Kumari Saru Yeh Jyh-Haw Chen Chien-Ming 《The Journal of supercomputing》2021,77(3):3024-3043
The Journal of Supercomputing - Accidents often occur in the earth—typhoons, floods, earthquakes, traffic accidents and so on. Whether these accidents can be timely and effectively responded... 相似文献
73.
Journal of Mathematical Imaging and Vision - A correction to this paper has been published: https://doi.org/10.1007/s10851-021-01028-0 相似文献
74.
75.
This paper presents a model of labor participation calibrated on a weekly basis; part-time and full-time employments are also
considered. By applying the theory of random utility maximization we model households’ choices. In order to have a good temporal
and spatial coverage the model is calibrated on three datasets, extracted from both national and regional travel surveys.
The results are applied to synthetic households that reproduce the Belgian population. The proposed innovative methodology
simulates synthetic agents by accounting both for households’ and individuals’ characteristics, while not suffering from the
problem of the “zero cell value”. The results indicate that there is major day-to-day variability in working activity participation;
in particular, on Wednesdays and Fridays the number of households working part-time or not working is particularly high. This
is consistent with what was expected by the analysts. Working participation is a fundamental component in activity based models
where work is considered a skeletal activity. The tools developed here can be useful to study how changes in population characteristics
(i.e. increases of flexible working arrangements and of the number of women in the work force) affect activity participation
and travel patterns. 相似文献
76.
Ling Yin Eric Y. J. Vancoille Kuppuswamy Ramesh Han Huang 《International Journal of Machine Tools and Manufacture》2004,44(6):607-615
Surface characterization of 6H-SiC (0001) substrates in indentation and abrasive machining was carried out to investigate microfracture, residual damage, and surface roughness associated with material removal and surface generation. Brittle versus plastic deformation was studied using Vickers indention and nano-indentation. To characterize the abrasive machining response, the 6H-SiC (0001) substrates were ground using diamond wheels with grit sizes of 25, 15 and 7 μm, and then polished with diamond suspensions of 3 and 0.05 μm. It is found that in indentation, there was a scale effect for brittle versus plastic deformation in 6H-SiC substrates. Also, in grinding, the scales of fracture and surface roughness of the substrates decreased with a decrease in diamond grit size. However, in polishing, a reduction in grit size of diamond suspensions gave no significant improvement in surface roughness. Furthermore, the results showed that fracture-free 6H-SiC (0001) surfaces were generated in polishing with the existence of the residual crystal defects, which were associated with the origin of defects in single crystal growth. 相似文献
77.
Inhibition of the major human drug-metabolizing cytochrome P450 3A4 (CYP3A4) by pharmaceuticals and other xenobiotics could lead to toxicity, drug–drug interactions and other adverse effects, as well as pharmacoenhancement. Despite serious clinical implications, the structural basis and attributes required for the potent inhibition of CYP3A4 remain to be established. We utilized a rational inhibitor design to investigate the structure–activity relationships in the analogues of ritonavir, the most potent CYP3A4 inhibitor in clinical use. This study elucidated the optimal length of the head-group spacer using eleven (series V) analogues with the R1/R2 side-groups as phenyls or R1–phenyl/R2–indole/naphthalene in various stereo configurations. Spectral, functional and structural characterization of the inhibitory complexes showed that a one-atom head-group linker elongation, from pyridyl–ethyl to pyridyl–propyl, was beneficial and markedly improved Ks, IC50 and thermostability of CYP3A4. In contrast, a two-atom linker extension led to a multi-fold decrease in the binding and inhibitory strength, possibly due to spatial and/or conformational constraints. The lead compound, 3h, was among the best inhibitors designed so far and overall, the strongest binder (Ks and IC50 of 0.007 and 0.090 µM, respectively). 3h was the fourth structurally simpler inhibitor superior to ritonavir, which further demonstrates the power of our approach. 相似文献
78.
79.
Clarisse Roblin Steve Chiumento Cdric Jacqueline Eric Pinloche Cendrine Nicoletti Hamza Olleik Elise Courvoisier-Dezord Agns Amouric Christian Basset Louis Dru Marie Ollivier Aurlie Bogey-Lambert Nicolas Vidal Mohamed Atta Marc Maresca Estelle Devillard Victor Duarte Josette Perrier Mickael Lafond 《International journal of molecular sciences》2021,22(6)
The world is on the verge of a major antibiotic crisis as the emergence of resistant bacteria is increasing, and very few novel molecules have been discovered since the 1960s. In this context, scientists have been exploring alternatives to conventional antibiotics, such as ribosomally synthesized and post-translationally modified peptides (RiPPs). Interestingly, the highly potent in vitro antibacterial activity and safety of ruminococcin C1, a recently discovered RiPP belonging to the sactipeptide subclass, has been demonstrated. The present results show that ruminococcin C1 is efficient at curing infection and at protecting challenged mice from Clostridium perfringens with a lower dose than the conventional antibiotic vancomycin. Moreover, antimicrobial peptide (AMP) is also effective against this pathogen in the complex microbial community of the gut environment, with a selective impact on a few bacterial genera, while maintaining a global homeostasis of the microbiome. In addition, ruminococcin C1 exhibits other biological activities that could be beneficial for human health, as well as other fields of applications. Overall, this study, by using an in vivo infection approach, confirms the antimicrobial clinical potential and highlights the multiple functional properties of ruminococcin C1, thus extending its therapeutic interest. 相似文献
80.
Dr. Eric J. Strobel 《Chembiochem : a European journal of chemical biology》2021,22(22):3214-3224
Site-specific strategies for exchanging segments of dsDNA are important for DNA library construction and molecular tagging. Deoxyuridine (dU) excision is an approach for generating 3’ ssDNA overhangs in gene assembly and molecular cloning procedures. Unlike approaches that use a multi-base pair motif to specify a DNA cut site, dU excision requires only a dT→dU substitution. Consequently, excision sites can be embedded in biologically active DNA sequences by placing dU substitutions at non-perturbative positions. In this work, I describe a molecular tagging method that uses dU excision to exchange a segment of a dsDNA strand with a long synthetic oligonucleotide. The core workflow of this method, called deoxyUridine eXcision-tagging (dUX-tagging), is an efficient one-pot reaction: strategically positioned dU nucleotides are excised from dsDNA to generate a 3’ overhang so that additional sequence can be appended by annealing and ligating a tagging oligonucleotide. The tagged DNA is then processed by one of two procedures to fill the 5’ overhang and remove excess tagging oligo. To facilitate its widespread use, all dUX-tagging procedures exclusively use commercially available reagents. As a result, dUX-tagging is a concise and easily implemented approach for high-efficiency linear dsDNA tagging. 相似文献