全文获取类型
收费全文 | 1999篇 |
免费 | 153篇 |
国内免费 | 3篇 |
出版年
2024年 | 2篇 |
2023年 | 25篇 |
2022年 | 26篇 |
2021年 | 60篇 |
2020年 | 30篇 |
2019年 | 47篇 |
2018年 | 67篇 |
2017年 | 51篇 |
2016年 | 81篇 |
2015年 | 87篇 |
2014年 | 112篇 |
2013年 | 163篇 |
2012年 | 175篇 |
2011年 | 155篇 |
2010年 | 102篇 |
2009年 | 91篇 |
2008年 | 125篇 |
2007年 | 122篇 |
2006年 | 105篇 |
2005年 | 72篇 |
2004年 | 69篇 |
2003年 | 70篇 |
2002年 | 64篇 |
2001年 | 30篇 |
2000年 | 31篇 |
1999年 | 29篇 |
1998年 | 14篇 |
1997年 | 10篇 |
1996年 | 8篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1992年 | 15篇 |
1991年 | 16篇 |
1990年 | 11篇 |
1989年 | 6篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 11篇 |
1984年 | 8篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1979年 | 4篇 |
1976年 | 2篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1965年 | 1篇 |
1962年 | 1篇 |
排序方式: 共有2155条查询结果,搜索用时 62 毫秒
971.
We constructed a library of sugar-dipeptide conjugate to find out the best complementary against hydrophobic pocket of α-glucosidase. The best substrate showed 150-fold improved Km value relative p-acetaminophenyl-α-d-glucopyranoside for α-glucosidase from Bacillus stearothermophillus. Using information from the complementary, we synthesized sp-WY and β-Glc-sp-WY, which selectivity inhibited the cognate enzyme. 相似文献
972.
Chau VM Phan VK Nguyen X Nguyen XC Nguyen PT Nguyen HN Hoang le TA Do CT Thuy DT Kang HK Jang HD Kim YH 《Bioorganic & medicinal chemistry letters》2011,21(7):2155-2159
Two new diterpenes, lobocompactols A (1) and B (2), and five known compounds (3-7) were isolated from the methanol extract of the soft coral Lobophytum compactum using combined chromatographic methods and identified based on NMR and MS data. Each compound was evaluated for cytotoxic activity against A549 (lung) and HL-60 (acute promyelocytic leukemia) human cancer cell lines. Among them, compound 5 exhibited strong cytotoxic activity against the A549 cell line with an IC50 of 4.97 ± 0.06 μM. Compounds 3, 4, and 7 showed moderate activity with IC50 values of 23.03 ± 0.76, 31.13 ± 0.08, and 36.45 ± 0.01 μM, respectively. The cytotoxicity of 5 on the A549 cells was comparable to that of the positive control, mitoxantrone (MX). All compounds exhibited moderate cytotoxicity against the HL-60 cell line, with IC50 values ranging from 17.80 ± 1.43 to 59.06 ± 2.31 μM. Their antioxidant activity was also measured using oxygen radical absorbance capacity method, compounds 1 and 2 exhibiting moderate peroxyl radical scavenging activity of 1.4 and 1.3 μM Trolox equivalents, respectively, at a concentration of 5 μM. 相似文献
973.
Anandan SK Webb HK Chen D Wang YX Aavula BR Cases S Cheng Y Do ZN Mehra U Tran V Vincelette J Waszczuk J White K Wong KR Zhang LN Jones PD Hammock BD Patel DV Whitcomb R MacIntyre DE Sabry J Gless R 《Bioorganic & medicinal chemistry letters》2011,21(3):983-988
1-(1-Acetyl-piperidin-4-yl)-3-adamantan-1-yl-urea 14a (AR9281), a potent and selective soluble epoxide hydrolase inhibitor, was recently tested in a phase 2a clinical setting for its effectiveness in reducing blood pressure and improving insulin resistance in pre-diabetic patients. In a mouse model of diet induced obesity, AR9281 attenuated the enhanced glucose excursion following an intraperitoneal glucose tolerance test. AR9281 also attenuated the increase in blood pressure in angiotensin-II-induced hypertension in rats. These effects were dose-dependent and well correlated with inhibition of the sEH activity in whole blood, consistent with a role of sEH in the observed pharmacology in rodents. 相似文献
974.
Neutral lipid from activated sludge (AS) as a potential source for biodiesel production has recently received considerable attentions. The utilization of useful compounds in AS may help reducing the cost of biodiesel production from AS. One of these compounds is the valuable wax esters (WEs) found in AS from a food processing company in Taiwan. About 4.13% (based on dry sludge weight) bleached wax was obtained after pretreatment and bleaching of crude sludge wax obtained from the dewaxing of crude sludge oil. The major WEs detected in the bleached wax were C46-C60 with small amounts of C37-C43 and C62 WEs. The fatty acids (FAs) and fatty alcohols (FALs) profiles of WEs were also investigated. Activated sludge WEs are mainly mixture of C14-C28 FAs and C24-C37 FALs, in which the predominant FAs are C16 and C18 while the predominant FALs are C32 and C34. 相似文献
975.
Nafati M Cheniclet C Hernould M Do PT Fernie AR Chevalier C Gévaudant F 《The Plant journal : for cell and molecular biology》2011,65(4):543-556
The size of tomato fruit results from the combination of cell number and cell size, which are respectively determined by the cell division and cell expansion processes. As fruit growth is mainly sustained by cell expansion, the development of fleshy pericarp tissue is characterized by numerous rounds of endoreduplication inducing a spectacular increase in DNA ploidy and mean cell size. Although a clear relationship exists between endoreduplication and cell growth in plants, the exact role of endoreduplication has not been clearly elucidated. To decipher the molecular basis of endoreduplication-associated cell growth in fruit, we investigated the putative involvement of the tomato cyclin-dependent kinase inhibitor SlKRP1. We studied the kinetics of pericarp development in tomato fruit at the morphological and cytological levels, and demonstrated that endoreduplication is directly proportional to cell and fruit diameter. We established a mathematical model for tissue growth according to the number of divisions and endocycles. This model was tested in fruits where we managed to decrease the extent of endoreduplication by over-expressing SlKRP1 under the control of a fruit-specific promoter expressed during early development. Despite the fact that endoreduplication was affected, we could not observe any morphological, cytological or metabolic phenotypes, indicating that determination of cell and fruit size can be, at least conditionally, uncoupled from endoreduplication. 相似文献
976.
Staben ST Siu M Goldsmith R Olivero AG Do S Burdick DJ Heffron TP Dotson J Sutherlin DP Zhu BY Tsui V Le H Lee L Lesnick J Lewis C Murray JM Nonomiya J Pang J Prior WW Salphati L Rouge L Sampath D Sideris S Wiesmann C Wu P 《Bioorganic & medicinal chemistry letters》2011,21(13):4054-4058
Starting from thienobenzopyran HTS hit 1, co-crystallization, molecular modeling and metabolic analysis were used to design potent and metabolically stable inhibitors of PI3-kinase. Compound 15 demonstrated PI3K pathway suppression in a mouse MCF7 xenograft model. 相似文献
977.
Zhang J Khvorostov I Hong JS Oktay Y Vergnes L Nuebel E Wahjudi PN Setoguchi K Wang G Do A Jung HJ McCaffery JM Kurland IJ Reue K Lee WN Koehler CM Teitell MA 《The EMBO journal》2011,30(24):4860-4873
It has been assumed, based largely on morphologic evidence, that human pluripotent stem cells (hPSCs) contain underdeveloped, bioenergetically inactive mitochondria. In contrast, differentiated cells harbour a branched mitochondrial network with oxidative phosphorylation as the main energy source. A role for mitochondria in hPSC bioenergetics and in cell differentiation therefore remains uncertain. Here, we show that hPSCs have functional respiratory complexes that are able to consume O(2) at maximal capacity. Despite this, ATP generation in hPSCs is mainly by glycolysis and ATP is consumed by the F(1)F(0) ATP synthase to partially maintain hPSC mitochondrial membrane potential and cell viability. Uncoupling protein 2 (UCP2) plays a regulating role in hPSC energy metabolism by preventing mitochondrial glucose oxidation and facilitating glycolysis via a substrate shunting mechanism. With early differentiation, hPSC proliferation slows, energy metabolism decreases, and UCP2 is repressed, resulting in decreased glycolysis and maintained or increased mitochondrial glucose oxidation. Ectopic UCP2 expression perturbs this metabolic transition and impairs hPSC differentiation. Overall, hPSCs contain active mitochondria and require UCP2 repression for full differentiation potential. 相似文献
978.
Madikiza Zimkitha Josephine Kimberly Bertolino Sandro Do Linh San Emmanuel 《Journal of Ethology》2011,29(2):375-380
We studied the socio-spatial organization of the woodland dormouse, Graphiurus murinus, by means of a monthly live-trapping and nest-box monitoring programme. Adult male (N = 5) home ranges were almost twice as large as those of females (N = 8), and both intra and intersexual home-range overlap was significantly larger in males than in females. However, the dispersion
pattern of females was rather clumped, even during the breeding period, suggesting that females are not territorial. Sexual
receptivity in females was asynchronous. In such circumstances, the Female in Space and Time hypothesis predicts that males
will be non-territorial, a scenario which is matched by our data. Therefore, it is likely that the woodland dormouse has a
promiscuous mating system. 相似文献
979.
980.
An efficient algorithm that can properly identify the targets to immunize or quarantine for preventing an epidemic in a population without knowing the global structural information is of obvious importance. Typically, a population is characterized by its community structure and the heterogeneity in the weak ties among nodes bridging over communities. We propose and study an effective algorithm that searches for bridge hubs, which are bridge nodes with a larger number of weak ties, as immunizing targets based on the idea of referencing to an expanding friendship circle as a self-avoiding walk proceeds. Applying the algorithm to simulated networks and empirical networks constructed from social network data of five US universities, we show that the algorithm is more effective than other existing local algorithms for a given immunization coverage, with a reduced final epidemic ratio, lower peak prevalence and fewer nodes that need to be visited before identifying the target nodes. The effectiveness stems from the breaking up of community networks by successful searches on target nodes with more weak ties. The effectiveness remains robust even when errors exist in the structure of the networks. 相似文献