全文获取类型
收费全文 | 12515篇 |
免费 | 1180篇 |
国内免费 | 31篇 |
专业分类
电工技术 | 171篇 |
综合类 | 15篇 |
化学工业 | 3136篇 |
金属工艺 | 499篇 |
机械仪表 | 652篇 |
建筑科学 | 209篇 |
矿业工程 | 3篇 |
能源动力 | 575篇 |
轻工业 | 1227篇 |
水利工程 | 45篇 |
石油天然气 | 10篇 |
武器工业 | 1篇 |
无线电 | 2183篇 |
一般工业技术 | 2944篇 |
冶金工业 | 716篇 |
原子能技术 | 146篇 |
自动化技术 | 1194篇 |
出版年
2024年 | 8篇 |
2023年 | 158篇 |
2022年 | 171篇 |
2021年 | 449篇 |
2020年 | 321篇 |
2019年 | 344篇 |
2018年 | 440篇 |
2017年 | 497篇 |
2016年 | 564篇 |
2015年 | 506篇 |
2014年 | 664篇 |
2013年 | 905篇 |
2012年 | 932篇 |
2011年 | 1196篇 |
2010年 | 804篇 |
2009年 | 798篇 |
2008年 | 619篇 |
2007年 | 551篇 |
2006年 | 466篇 |
2005年 | 379篇 |
2004年 | 360篇 |
2003年 | 348篇 |
2002年 | 258篇 |
2001年 | 254篇 |
2000年 | 241篇 |
1999年 | 214篇 |
1998年 | 299篇 |
1997年 | 168篇 |
1996年 | 145篇 |
1995年 | 97篇 |
1994年 | 93篇 |
1993年 | 65篇 |
1992年 | 55篇 |
1991年 | 42篇 |
1990年 | 40篇 |
1989年 | 42篇 |
1988年 | 28篇 |
1987年 | 21篇 |
1986年 | 30篇 |
1985年 | 17篇 |
1984年 | 19篇 |
1983年 | 12篇 |
1981年 | 8篇 |
1980年 | 9篇 |
1979年 | 8篇 |
1977年 | 10篇 |
1976年 | 11篇 |
1974年 | 8篇 |
1971年 | 7篇 |
1970年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Inside Cover: Tetrazolylhydrazides as Selective Fragment‐Like Inhibitors of the JumonjiC‐Domain‐Containing Histone Demethylase KDM4A (ChemMedChem 11/2015)
下载免费PDF全文
![点击此处可从《ChemMedChem》网站下载免费的PDF全文](/ch/ext_images/free.gif)
992.
Cheol Park Won Sup Lee Se-Il Go Arulkumar Nagappan Min Ho Han Su Hyun Hong Gon Sup Kim Gi Young Kim Taeg Kyu Kwon Chung Ho Ryu Sung Chul Shin Yung Hyun Choi 《International journal of molecular sciences》2015,16(1):645-659
Evidence suggests that phytochemicals can safely modulate cancer cell biology and induce apoptosis. Here, we investigated the anti-cancer activity of morin, a flavone originally isolated from members of the Moraceae family in human leukemic cells, focusing on apoptosis. An anti-cancer effect of morin was screened with several human leukemic cell lines. U937 cells were most sensitive to morin, where it induced caspase-dependent apoptosis in a dose-dependent manner. It also induced loss of MMP (ΔΨm) along with cytochrome c release, down-regulated Bcl-2 protein, and up-regulated BAX proteins. The apoptotic activity of morin was significantly attenuated by Bcl-2 augmentation. In conclusion, morin induced caspase-dependent apoptosis through an intrinsic pathway by upregulating BAD proteins. In addition, Bcl-2 protein expression is also important in morin-induced apoptosis of U937 cells. This study provides evidence that morin might have anticancer properties in human leukemic cells. 相似文献
993.
Yoon-Jung Moon Joseph Kwon Sung-Ho Yun Hye Li Lim Jonghyun Kim Soo Jung Kim Sung Gyun Kang Jung-Hyun Lee Seung Il Kim Young-Ho Chung 《International journal of molecular sciences》2015,16(5):9167-9195
The hyperthermophilic archaeon Thermococcus onnurineus NA1 has been shown to produce H2 when using CO, formate, or starch as a growth substrate. This strain can also utilize elemental sulfur as a terminal electron acceptor for heterotrophic growth. To gain insight into sulfur metabolism, the proteome of T. onnurineus NA1 cells grown under sulfur culture conditions was quantified and compared with those grown under H2-evolving substrate culture conditions. Using label-free nano-UPLC-MSE-based comparative proteomic analysis, approximately 38.4% of the total identified proteome (589 proteins) was found to be significantly up-regulated (≥1.5-fold) under sulfur culture conditions. Many of these proteins were functionally associated with carbon fixation, Fe–S cluster biogenesis, ATP synthesis, sulfur reduction, protein glycosylation, protein translocation, and formate oxidation. Based on the abundances of the identified proteins in this and other genomic studies, the pathways associated with reductive sulfur metabolism, H2-metabolism, and oxidative stress defense were proposed. The results also revealed markedly lower expression levels of enzymes involved in the sulfur assimilation pathway, as well as cysteine desulfurase, under sulfur culture condition. The present results provide the first global atlas of proteome changes triggered by sulfur, and may facilitate an understanding of how hyperthermophilic archaea adapt to sulfur-rich, extreme environments. 相似文献
994.
Heerim Kang Chang Hyung Lee Jong Rhan Kim Jung Yeon Kwon Sang Gwon Seo Jae Gab Han Byung Gon Kim Jong-Eun Kim Ki Won Lee 《International journal of molecular sciences》2015,16(9):21021-21034
Atopic dermatitis (AD) is a chronic and inflammatory skin disease that can place a significant burden on quality of life for patients. AD most frequently appears under the age of six and although its prevalence is increasing worldwide, therapeutic treatment options are limited. Chlorella vulgaris (CV) is a species of the freshwater green algae genus chlorella, and has been reported to modulate allergy-inducible factors when ingested. Here, we examined the effect of CV supplementation on AD-like symptoms in NC/Nga mice. CV was orally administrated for six weeks while AD-like symptoms were induced via topical application of Dermatophagoides farinae extract (DFE). CV treatment reduced dermatitis scores, epidermal thickness, and skin hydration. Histological analysis also revealed that CV treatment reduced DFE-induced eosinophil and mast cell infiltration into the skin, while analysis of serum chemokine levels indicated that CV treatment downregulated thymus- and activation-regulated chemokine (TARC) and macrophage-derived chemokine (MDC) levels. In addition, CV treatment downregulated mRNA expression levels of IL-4 and IFN-γ. Taken together, these results suggest that CV extract may have potential as a nutraceutical ingredient for the prevention of AD. 相似文献
995.
Hydrogen‐Bonding‐Driven Enantioselective Resolution against the Kazlauskas Rule To Afford γ‐Amino Alcohols by Candida rugosa Lipase
下载免费PDF全文
![点击此处可从《Chembiochem : a European journal of chemical biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Bora Min Jeemin Park Yong‐Kyun Sim Dr. Suhyun Jung Seong‐Ho Kim Dr. Jae Kwang Song Dr. Bum Tae Kim Prof. Sang Youn Park Prof. Jaesook Yun Prof. Seongsoon Park Dr. Hyuk Lee 《Chembiochem : a European journal of chemical biology》2015,16(1):77-82
Most lipases resolve secondary alcohols in accordance with the “Kazlauskas rule” to give the R enantiomers. In a similar manner to other lipases, Candida rugosa lipase (CRL) exhibits R enantioselectivity towards heptan‐2‐ol, although the enantiomeric ratio (E) is low (E=1.6). However, unexpected enantioselectivity (i.e., S enantioselectivity, E=58) of CRL towards 4‐(tert‐butoxycarbonylamino)butan‐2‐ol, which has a similar chain length to heptan‐2‐ol, has been observed. To develop a deeper understanding of the molecular basis for this unusual enantioselectivity, we have conducted a series of molecular modeling and substrate engineering experiments. The results of these computational and experimental analyses indicated that a hydrogen bond between the Ser450 residue and the nitrogen atom of the carbamate group is critical to stabilize the transition state of the S enantiomer. 相似文献
996.
Dong‐Won Kang Yuki Takiguchi Porponth Sichanugrist Makoto Konagai 《Progress in Photovoltaics: Research and Applications》2016,24(7):1016-1023
In this work, we practically demonstrated spectrum‐splitting approach for advances in efficiency of photovoltaic cells. Firstly, a‐Si:H//c‐Si 2‐junction configuration was designed, which exhibited 24.4% efficiency with the spectrum splitting at 620 nm. Then, we improved the top cell property by employing InGaP cells instead of the a‐Si:H, resulting in an achievement of efficiency about 28.8%. In addition, we constructed 3‐junction spectrum‐splitting system with two optical splitters, and GaAs solar cells as middle cell. This InGaP//GaAs//c‐Si architecture was found to deliver 30.9% conversion efficiency. Our splitting system includes convex lenses for light concentration about 10 suns, which provided concentrated efficiency exceeding 33.0%. These results suggest that our demonstration of 3‐junction spectrum‐splitting approach can be a promising candidate for highly efficient photovoltaic technologies. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
997.
In this study, poly(allylamine hydrochloride) (PAA/HCl) was cross-linked with fermentation bacterial waste (Escherichia coli) in order to introduce a large amount of amine groups as binding sites for potassium hexachloroplatinate(IV), as a model anionic pollutant. The sorption performance of PAA/HCl-modified E. coli was greatly affected by the dosages of PAA/HCl and crosslinker (epichlorohydrin, ECH), and by the pH of the modification reaction medium. These factors were optimized through the response surface methodology (RSM). A three-level factorial Box-Behnken design was performed, and a second-order polynomial model was successfully used to describe the effects of PAA/HCl, ECH and the pH on the Pt(IV) uptake (R2 = 0.988). The optimal conditions that were obtained from the RSM were 0.49 g of PAA/HCl, 0.05 mL of ECH and pH 10.02, with 1.0 g of dried E. coli biomass. The biosorption isotherm and kinetics studies were carried out in order to evaluate the sorption potential of the PAA/HCl-modified E. coli that was prepared under the optimized conditions. The sorption performance of the developed bacterial biosorbent was 4.36 times greater than that of the raw E. coli. Desorption was carried out using 0.05 M acidified thiourea and the biosorbent was successfully regenerated and reused up to four cycles. Therefore, this simple and cost-effective method suggested here is a useful modification tool for the development of high performance biosorbents for the recovery of anionic precious metals. 相似文献
998.
Hwang S. H. Lim J. W. Lee W.-J. Kim G. W. Cho C. H. An J. B. Jung K. Y. Cha K. S. Rho B. S. 《Photonics Technology Letters, IEEE》2010,22(3):167-169
999.
Inundation of roads by heavy rainfall has attracted more attention than traffic accidents, traffic congestion, and construction because it simultaneously causes travel delays and threatens driver safety. For these reasons, in this paper, we propose an inundation hazard index (IHI) of road links, which shows the possibility of inundation of road links caused by rainfall. To generate the index, we have used two key data sources, namely the digital elevation model (DEM) and past rainfall records of when inundation has occurred. IHI is derived by statistically analyzing the relationships between the normalized relative height of the road links calculated from DEM within the watershed and past rainfall records. After analyzing the practical applicability of the proposed index with a commercial car navigation system through a set of tests, we confirmed that the proposed IHI could be implemented to choose safer routes, with reduced chances of encountering roads having inundation risks.s 相似文献
1000.
The fundamental transverse mode lasing of a hybrid laser diode is a prerequisite for efficient coupling to a single‐mode silicon waveguide, which is necessary for a wavelength‐division multiplexing silicon interconnection. We investigate the lasing mode profile for a hybrid laser diode consisting of silicon slab and InP/InGaAsP deep ridge waveguides. When the thickness of the top silicon is 220 nm, the fundamental transverse mode is lasing in spite of the wide waveguide width of 3.7µm. The threshold current is 40 mA, and the maximum output power is 5 mW under CW current operation. In the case of a thick top silicon layer (1 µm), the higher modes are lasing. There is no significant difference in the thermal resistance of the two devices. 相似文献