全文获取类型
收费全文 | 1130篇 |
免费 | 104篇 |
国内免费 | 2篇 |
出版年
2023年 | 6篇 |
2022年 | 18篇 |
2021年 | 30篇 |
2020年 | 17篇 |
2019年 | 21篇 |
2018年 | 29篇 |
2017年 | 18篇 |
2016年 | 34篇 |
2015年 | 49篇 |
2014年 | 42篇 |
2013年 | 62篇 |
2012年 | 87篇 |
2011年 | 66篇 |
2010年 | 43篇 |
2009年 | 36篇 |
2008年 | 47篇 |
2007年 | 50篇 |
2006年 | 35篇 |
2005年 | 51篇 |
2004年 | 44篇 |
2003年 | 39篇 |
2002年 | 34篇 |
2001年 | 23篇 |
2000年 | 30篇 |
1999年 | 20篇 |
1998年 | 11篇 |
1997年 | 11篇 |
1996年 | 15篇 |
1995年 | 12篇 |
1994年 | 11篇 |
1993年 | 10篇 |
1992年 | 15篇 |
1991年 | 13篇 |
1990年 | 18篇 |
1989年 | 14篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1986年 | 9篇 |
1985年 | 21篇 |
1984年 | 11篇 |
1983年 | 9篇 |
1982年 | 13篇 |
1981年 | 10篇 |
1979年 | 12篇 |
1978年 | 9篇 |
1977年 | 5篇 |
1974年 | 9篇 |
1971年 | 4篇 |
1970年 | 6篇 |
1949年 | 3篇 |
排序方式: 共有1236条查询结果,搜索用时 31 毫秒
961.
Mosquitoes, which evade contact with long-lasting insecticidal nets and indoor residual sprays, by feeding outdoors or upon animals, are primary malaria vectors in many tropical countries. They can also dominate residual transmission where high coverage of these front-line vector control measures is achieved. Complementary strategies, which extend insecticide coverage beyond houses and humans, are required to eliminate malaria transmission in most settings. The overwhelming diversity of the world's malaria transmission systems and optimal strategies for controlling them can be simply conceptualized and mapped across two-dimensional scenario space defined by the proportion of blood meals that vectors obtain from humans and the proportion of human exposure to them which occurs indoors. 相似文献
962.
963.
964.
Tatyana G. Kahn Eshagh Dorafshan Dorothea Schultheis Aman Zare Per Stenberg Ingolf Reim Vincenzo Pirrotta Yuri B. Schwartz 《Nucleic acids research》2016,44(21):10132-10149
Polycomb Group (PcG) proteins are epigenetic repressors essential for control of development and cell differentiation. They form multiple complexes of which PRC1 and PRC2 are evolutionary conserved and obligatory for repression. The targeting of PRC1 and PRC2 is poorly understood and was proposed to be hierarchical and involve tri-methylation of histone H3 (H3K27me3) and/or monoubiquitylation of histone H2A (H2AK118ub). Here, we present a strict test of this hypothesis using the Drosophila model. We discover that neither H3K27me3 nor H2AK118ub is required for targeting PRC complexes to Polycomb Response Elements (PREs). We find that PRC1 can bind PREs in the absence of PRC2 but at many PREs PRC2 requires PRC1 to be targeted. We show that one role of H3K27me3 is to allow PcG complexes anchored at PREs to interact with surrounding chromatin. In contrast, the bulk of H2AK118ub is unrelated to PcG repression. These findings radically change our view of how PcG repression is targeted and suggest that PRC1 and PRC2 can communicate independently of histone modifications. 相似文献
965.
Anastasia Felker Susan Nieuwenhuize Aymeric Dolbois Kristyna Blazkova Christopher Hess Larry W. L. Low Sibylle Burger Natasha Samson Tom J. Carney Petr Bartunek Cristina Nevado Christian Mosimann 《PloS one》2016,11(4)
Mutant Estrogen Receptor (ERT2) ligand-binding domain fusions with Cre recombinase are a key tool for spatio-temporally controlled genetic recombination with the Cre/lox system. CreERT2 is efficiently activated in a concentration-dependent manner by the Tamoxifen metabolite trans-4-OH-Tamoxifen (trans-4-OHT). Reproducible and efficient Cre/lox experimentation is hindered by the gradual loss of CreERT2 induction potency upon prolonged storage of dissolved trans-4-OHT, which potentially results from gradual trans-to-cis isomerization or degradation. Here, we combined zebrafish CreERT2 recombination experiments and cell culture assays to document the gradual activity loss of trans-4-OHT and describe the alternative Tamoxifen metabolite Endoxifen as more stable alternative compound. Endoxifen retains potent activation upon prolonged storage (3 months), yet consistently induces half the ERT2 domain fusion activity compared to fresh trans-4-OHT. Using 1H-NMR analysis, we reveal that trans-4-OHT isomerization is undetectable upon prolonged storage in either DMSO or Ethanol, ruling out isomer transformation as cause for the gradual loss of trans-4-OHT activity. We further establish that both trans-4-OHT and Endoxifen are insensitive to light exposure under regular laboratory handling conditions. We attribute the gradual loss of trans-4-OHT potency to precipitation over time, and show that heating of aged trans-4-OHT aliquots reinstates their CreERT2 induction potential. Our data establish Endoxifen as potent and reproducible complementary compound to 4-OHT to control ERT2 domain fusion proteins in vivo, and provide a framework for efficient chemically controlled recombination experiments. 相似文献
966.
Rohit Kumar Aman Kumar Nand Kishor Sharma Navneet Kaur Venkatesh Chunduri Meenakshi Chawla Saloni Sharma Kashmir Singh Monika Garg 《PloS one》2016,11(1)
Starch and proteins are major components in the wheat endosperm that affect its end product quality. Between the two textural classes of wheat i.e. hard and soft, starch granules are loosely bound with the lipids and proteins in soft wheat due to higher expression of interfering grain softness proteins. It might have impact on starch granules properties. In this work for the first time the physiochemical and structural properties of different sized starch granules (A-, B- and C-granules) were studied to understand the differences in starches with respect to soft and hard wheat. A-, B- and C-type granules were separated with >95% purity. Average number and proportion of A-, B-, and C-type granules was 18%, 56%, 26% and 76%, 19%, 5% respectively. All had symmetrical birefringence pattern with varied intensity. All displayed typical A-type crystallites. A-type granules also showed V-type crystallinity that is indicative of starch complexes with lipids and proteins. Granules differing in gelatinization temperature (ΔH) and transition temperature (ΔT), showed different enthalpy changes during heating. Substitution analysis indicated differences in relative substitution pattern of different starch granules. Birefringence, percentage crystallinity, transmittance, gelatinization enthalpy and substitution decreased in order of A>B>C being higher in hard wheat than soft wheat. Amylose content decreased in order of A>B>C being higher in soft wheat than hard wheat. Reconstitution experiment showed that starch properties could be manipulated by changing the composition of starch granules. Addition of A-granules to total starch significantly affected its thermal properties. Effect of A-granule addition was higher than B- and C-granules. Transmittance of the starch granules paste showed that starch granules of hard wheat formed clear paste. These results suggested that in addition to differences in protein concentration, hard and soft wheat lines have differences in starch composition also. 相似文献
967.
968.
Szewczyk MM Davis KA Samson SE Simpson F Rangachari PK Grover AK 《Journal of cellular and molecular medicine》2007,11(1):129-138
Vascular endothelial cells (EC) and smooth muscle cells (SMC) require a decrease in cytoplasmic Ca2+ concentration after activation. This can be achieved by Ca2+ sequestration by the sarco-/endoplasmic reticulum Ca2+ pumps (SERCA) and Ca2+ extrusion by plasma membrane Ca2+ pumps (PMCA) and Na+-Ca2+-exchangers (NCX). Since the two cell types differ in their structure and function, we compared the activities of PMCA, NCX and SERCA in pig coronary artery EC and SMC, the types of isoforms expressed using RT-PCR, and their protein abundance using Western blots. The activity of NCX is higher in EC than in SMC but those of PMCA and SERCA is lower. Consistently, the protein abundance for NCX protein is higher in EC than in SMC and those of PMCA and SERCA is lower. Based on RT-PCR experiments, the types of RNA present are as follows: EC for PMCA1 while SMC for PMCA4 and PMCA1; EC for SERCA2 and SERCA3 and SMC for SERCA2. Both EC and SMC express NCX1 (mainly NCX1.3). PMCA, SERCA and NCX differ in their affinities for Ca2+ and regulation. Based on these observations and the literature, we conclude that the tightly regulated Ca2+ removal systems in SMC are consistent with the cyclical control of contractility of the filaments and those in EC are consistent with Ca2+ regulation of the endothelial nitric oxide synthase near the cell surface. The differences between EC and SMC should be considered in therapeutic interventions of cardiovascular diseases. 相似文献
969.
Dekebo A Kashiwagi T Tebayashi SI Kim CS 《Bioscience, biotechnology, and biochemistry》2007,71(2):421-426
Mature leaves of the sweet pepper, Capsicum annuum, exhibited resistance against the American serpentine leafminer, Liriomyza trifolii (Burgess), Agromyzidae. Based on bioassay-guided fractionation, three compounds, namely 4-aminobutanoic acid, (2S,4R)-4-hydroxy-1-methyl-2-pyrrolidine carboxylic acid and 4-amino-1-beta-D-ribofuranosyl-2(1H)-pyrimidinone, were isolated from the leaves of sweet pepper. These compounds had significant oviposition deterrence towards adult flies of L. trifolii from laying their eggs on host plant leaves treated at 3.70, 16.60 and 6.45 microg/cm(2), respectively. 相似文献
970.
Pascal Lesage Tomas Ekvall Louise Deschênes Réjean Samson 《The International Journal of Life Cycle Assessment》2007,12(7):497-513