全文获取类型
收费全文 | 14654篇 |
免费 | 1394篇 |
国内免费 | 1784篇 |
专业分类
17832篇 |
出版年
2024年 | 39篇 |
2023年 | 150篇 |
2022年 | 413篇 |
2021年 | 643篇 |
2020年 | 493篇 |
2019年 | 611篇 |
2018年 | 581篇 |
2017年 | 484篇 |
2016年 | 605篇 |
2015年 | 913篇 |
2014年 | 1064篇 |
2013年 | 1171篇 |
2012年 | 1389篇 |
2011年 | 1265篇 |
2010年 | 904篇 |
2009年 | 889篇 |
2008年 | 933篇 |
2007年 | 842篇 |
2006年 | 679篇 |
2005年 | 666篇 |
2004年 | 552篇 |
2003年 | 529篇 |
2002年 | 467篇 |
2001年 | 302篇 |
2000年 | 210篇 |
1999年 | 189篇 |
1998年 | 175篇 |
1997年 | 118篇 |
1996年 | 76篇 |
1995年 | 68篇 |
1994年 | 69篇 |
1993年 | 48篇 |
1992年 | 67篇 |
1991年 | 45篇 |
1990年 | 29篇 |
1989年 | 31篇 |
1988年 | 26篇 |
1987年 | 17篇 |
1986年 | 19篇 |
1985年 | 23篇 |
1984年 | 9篇 |
1983年 | 9篇 |
1982年 | 9篇 |
1981年 | 2篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1967年 | 2篇 |
1965年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Ying‐Ying Wang Bao‐Hua Hou Jin‐Zhi Guo Qiu‐Li Ning Wei‐Lin Pang Jiawei Wang Chang‐Li Lü Xing‐Long Wu 《Liver Transplantation》2018,8(18)
Presently, commercialization of sodium‐ion batteries (SIBs) is still hindered by the relatively poor energy‐storage performance. In addition, low‐temperature (low‐T) Na storage is another principal concern for the wide application of SIBs. Unfortunately, the Na‐transfer kinetics is extremely sluggish at low‐T, as a result, there are few reports on low‐T SIBs. Here, an advanced low‐T sodium‐ion full battery (SIFB) assembled by an anode of 3D Se/graphene composite and a high‐voltage cathode (Na3V2(PO4)2O2F) is developed, exhibiting ultralong lifespan (over even 15 000 cycles, the capacity retention is still up to 86.3% at 1 A g?1), outstanding low‐T energy storage performance (e.g., all values of capacity retention are >75% after 1000 cycles at temperatures from 25 to ?25 °C at 0.4 A g?1), and high‐energy/power properties. Such ultralong lifespan signifies that the developed sodium‐ion full battery can be used for longer than 60 years, if batteries charge/discharge once a day and 80% capacity retention is the standard of battery life. As a result, the present study not only promotes the practicability and commercialization of SIBs but also points out the new developing directions of next‐generation energy storage for wider range applications. 相似文献
42.
谷胱甘肽参与动植物体内的各种代谢活动,起着重要的作用。谷胱甘肽的测定方法有多种,如碘量法、纸层析法、高效液相色谱法等,但目前为止还没有一种快速、简便、准确、经济的方法。本文就谷胱甘肽的测定方法进展进行了简要概述。 相似文献
43.
Huachen Gan Guibo Wang Qin Hao Q. Jane Wang Hua Tang 《The Journal of biological chemistry》2013,288(52):37343-37354
At the interface between host and external environment, the airway epithelium serves as a major protective barrier. In the present study we show that protein kinase D (PKD) plays an important role in the formation and integrity of the airway epithelial barrier. Either inhibition of PKD activity or silencing of PKD increased transepithelial electrical resistance (TEER), resulting in a tighter epithelial barrier. Among the three PKD isoforms, PKD3 knockdown was the most efficient one to increase TEER in polarized airway epithelial monolayers. In contrast, overexpression of PKD3 wild type, but not PKD3 kinase-inactive mutant, disrupted the formation of apical intercellular junctions and their reassembly, impaired the development of TEER, and increased paracellular permeability to sodium fluorescein in airway epithelial monolayers. We further found that overexpression of PKD, in particular PKD3, markedly suppressed the mRNA and protein levels of claudin-1 but had only minor effects on the expression of other tight junctional proteins (claudin-3, claudin-4, claudin-5, occludin, and ZO-1) and adherent junctional proteins (E-cadherin and β-catenin). Immunofluorescence study revealed that claudin-1 level was markedly reduced and almost disappeared from intercellular contacts in PKD3-overexpressed epithelial monolayers and that claudin-4 was also restricted from intercellular contacts and tended to accumulate in the cell cytosolic compartments. Last, we found that claudin-1 knockdown prevented TEER elevation by PKD inhibition or silencing in airway epithelial monolayers. These novel findings indicate that PKD negatively regulates human airway epithelial barrier formation and integrity through down-regulation of claudin-1, which is a key component of tight junctions. 相似文献
44.
Tao Fang Wang Heng Wang Ai Fen Peng Qing Feng Luo Zhi Li Liu Rong Ping Zhou Song Gao Yang Zhou Wen Zhao Chen 《Biochemical and biophysical research communications》2013
FASN plays an important role in the malignant phenotype of various tumors. Our previous studies show that inhibition FASN could induce apoptosis and inhibit proliferation in human osteosarcoma (OS) cell in vivo and vitro. The aim in this study was to investigate the effect of inhibition FASN on the activity of HER2/PI3K/AKT axis and invasion and migration of OS cell. The expression of FASN, HER2 and p-HER2(Y1248) proteins was detected by immunohistochemistry in OS tissues from 24 patients with pulmonary metastatic disease, and the relationship between FASN and p-HER2 as well as HER2 was investigated. The results showed that there was a positive correlation between FASN and HER2 as well as p-HER2 protein expression. The U-2 OS cells were transfected with either the FASN specific RNAi plasmid or the negative control RNAi plasmid. FASN mRNA was measured by RT-PCR. Western blot assays was performed to examine the protein expression of FASN, HER2, p-HER2(Y1248), PI3K, Akt and p-Akt (Ser473). Migration and invasion of cells were investigated by wound healing and transwell invasion assays. The results showed that the activity of HER2/PI3K/AKT signaling pathway was suppressed by inhibiting FASN. Meanwhile, the U-2OS cells migration and invasion were also impaired by inhibiting the activity of FASN/HER2/PI3K/AKT. Our results indicated that inhibition of FASN suppresses OS cell invasion and migration via down-regulation of the “HER2/PI3K/AKT” axis in vitro. FASN blocker may be a new therapeutic strategy in OS management. 相似文献
45.
Bacillus thuringiensis is a Gram‐positive aerobic bacterium that produces insecticidal crystalline inclusions during sporulation phases of the mother cell. The virulence factor, known as parasporal crystals, is composed of Cry and Cyt toxins. Most Cry toxins display a common 3‐domain topology. Cry toxins exert intoxication through toxin activation, receptor binding and pore formation in a suitable larval gut environment. The mosquitocidal toxins of Bt subsp. israelensis (Bti) were found to be highly active against mosquito larvae and are widely used for vector control. Bt subsp. jegathesan is another strain which possesses high potency against broad range of mosquito larvae. The present review summarizes characterized receptors for Cry toxins in mosquito larvae, and will also discuss the diversity and effects of 3‐D mosquitocidal Cry toxin and the ongoing research for Cry toxin mechanisms generated from investigations of lepidopteran and dipteran larvae. 相似文献
46.
Yang ZH Zeng R Yang G Wang Y Li LZ Lv ZS Yao M Lai B 《Journal of industrial microbiology & biotechnology》2008,35(9):1047-1051
As an important organic compound, chiral alcohols are the key chiral building blocks to many single enantiomer pharmaceuticals. Asymmetric reduction of the corresponding prochiral ketones to produce the chiral alcohols by biocatalysis is one of the most promising routes. Asymmetric reduction of different kinds of non-natural prochiral ketones catalyzed by various plants tissue was studied in this work. Acetophenone, 4'-chloroacetophenone and ethyl 4-chloroacetoacetate were chosen as the model substrates for simple ketone, halogen-containing aromatic ketone and beta-ketoesters, respectively. Apple (Malus pumila), carrot (Daucus carota), cucumber (Cucumis sativus), onion (Allium cepa), potato (Soanum tuberosum), radish (Raphanus sativus) and sweet potato (Ipomoea batatas) were chosen as the biocatalysts. It was found that these kinds of prochiral ketoness could be reduced by these plants tissue with high enantioselectivity. Both R- and S-form configuration chiral alcohols could be obtained. The e.e. and chemical yield could reach about 98 and 80% respectively for acetophenone and 4'-chloroacetophenone reduction reaction with favorable plant tissue. And the e.e. and yield for ethyl 4-chloroacetoacetate reduction reaction was about 91 and 45% respectively. 相似文献
47.
48.
Wen-Xue Zhang Zheng-Yun Wu Qi-Sheng Zhang Rong Wang Heng Li 《World journal of microbiology & biotechnology》2009,25(10):1721-1726
Application of a compound starter composed of traditional Daqu, high quality Fuqu developed previously in our lab, and alcohol-producing and aroma-producing yeasts in the brewing of Luzhou-flavor liquor was investigated. Compared with traditional Daqu, the compound starter demonstrated apparently higher starch utilization and alcohol productivity both in flasks and in pits.
Flavor ingredient analyses showed that the flavor ingredient compositions of liquors produced with the compound starter were
similar to those obtained with the traditional process. With appropriate after treatments, the compound starter may be applied
in distilleries for elevating the productivity of traditional liquor or producing high quality new-style distilled liquor.
As starch utilization can be increased significantly, using this compound starter in liquor brewing is especially meaningful
for lessening environmental pollution. These findings may also be helpful for further understanding the mechanisms of Chinese
liquor brewing. 相似文献
49.
Hong Jun Jeon Young Rong Bang Hye Youn Park Seul A. Kim 《Chronobiology international》2017,34(6):677-686
Various physiological and psychological functions are influenced by circadian typology (CT), which was reported to be related to resilience. However, few studies have assessed the effects of CT in relation to resilience. The aim of the present study was to assess the influence of CT on sleep-related symptoms, physical fatigue and psychological well-being in relation to resilience. The present study included a total of 1794 healthy hospital employees, and they completed the Morningness–Eveningness Questionnaire, Connor–Davidson Resilience Scale, Pittsburgh Sleep Quality Index, Epworth Sleepiness Scale, Fatigue Severity Scale, Hospital Anxiety and Depression Scale and World Health Organization Quality of Life Scale Abbreviated Version. Subjects with evening type showed lower sleep quality, more daytime sleepiness and physical fatigue than neither types and morning types. Additionally, evening types were more depressed and anxious and reported a poorer quality of life. CT was found to be a significant predictor of sleep quality, but CT was minimally associated with physical fatigue and psychological well-being in the regression analysis. Instead, resilience was substantially related to all of the variables measured. In conclusion, CT independently predicts sleep quality, but the effects of CT on physical fatigue and psychological well-being are negligible compared to those of resilience. 相似文献
50.