全文获取类型
收费全文 | 13486篇 |
免费 | 1037篇 |
国内免费 | 833篇 |
专业分类
15356篇 |
出版年
2024年 | 29篇 |
2023年 | 137篇 |
2022年 | 331篇 |
2021年 | 600篇 |
2020年 | 368篇 |
2019年 | 482篇 |
2018年 | 427篇 |
2017年 | 332篇 |
2016年 | 493篇 |
2015年 | 822篇 |
2014年 | 879篇 |
2013年 | 1052篇 |
2012年 | 1219篇 |
2011年 | 1043篇 |
2010年 | 641篇 |
2009年 | 569篇 |
2008年 | 774篇 |
2007年 | 608篇 |
2006年 | 612篇 |
2005年 | 488篇 |
2004年 | 415篇 |
2003年 | 348篇 |
2002年 | 289篇 |
2001年 | 269篇 |
2000年 | 224篇 |
1999年 | 223篇 |
1998年 | 158篇 |
1997年 | 126篇 |
1996年 | 138篇 |
1995年 | 130篇 |
1994年 | 115篇 |
1993年 | 94篇 |
1992年 | 134篇 |
1991年 | 117篇 |
1990年 | 81篇 |
1989年 | 103篇 |
1988年 | 62篇 |
1987年 | 48篇 |
1986年 | 58篇 |
1985年 | 65篇 |
1984年 | 19篇 |
1983年 | 24篇 |
1982年 | 28篇 |
1981年 | 12篇 |
1980年 | 25篇 |
1979年 | 21篇 |
1978年 | 17篇 |
1977年 | 20篇 |
1975年 | 11篇 |
1972年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Chen Z Davies E Miller WS Shan S Valenzano KJ Kyle DJ 《Bioorganic & medicinal chemistry letters》2004,14(21):5275-5279
Small molecule mu agonists based on the 4-phenyl piperidine scaffold were designed and synthesized to further investigate the therapeutic potential of loperamide analogs. The resulting compounds show excellent agonistic activity towards the human mu receptor with interesting SAR trends within the series. 相似文献
992.
利用木质纤维素生产燃料乙醇的过程中,前期预处理所产生的抑制剂会影响酵母的正常生长和后续的发酵过程。为减小抑制剂的影响所采取的一些脱毒策略往往造成糖的损失和生产成本的增加,这在实际生产与经济上是不可行的。因此,具有强的抑制剂耐受性的酿酒酵母菌株对于提高纤维素乙醇产率是十分重要的。近十年来,对于酿酒酵母胁迫耐受机制的研究取得了一些重要的进展,着重介绍目前酿酒酵母对抑制剂耐受机制的研究现状,包括一些关键性基因的表达及代谢通路过程分析等。同时也介绍一些应对抑制剂提高酵母发酵能力的措施。 相似文献
993.
An ATP signalling pathway in plant cells: extracellular ATP triggers programmed cell death in Populus euphratica 总被引:2,自引:0,他引:2
Sun J Zhang CL Deng SR Lu CF Shen X Zhou XY Zheng XJ Hu ZM Chen SL 《Plant, cell & environment》2012,35(5):893-916
We elucidated the extracellular ATP (eATP) signalling cascade active in programmed cell death (PCD) using cell cultures of Populus euphratica. Millimolar amounts of eATP induced a dose‐ and time‐dependent reduction in viability, and the agonist‐treated cells displayed hallmark features of PCD. eATP caused an elevation of cytosolic Ca2+ levels, resulting in Ca2+ uptake by the mitochondria and subsequent H2O2 accumulation. P. euphratica exhibited an increased mitochondrial transmembrane potential, and cytochrome c was released without opening of the permeability transition pore over the period of ATP stimulation. Moreover, the eATP‐induced increase of intracellular ATP, essential for the activation of caspase‐like proteases and subsequent PCD, was found to be related to increased mitochondrial transmembrane potential. NO is implicated as a downstream component of the cytosolic Ca2+ concentration but plays a negligible role in eATP‐stimulated cell death. We speculate that ATP binds purinoceptors in the plasma membrane, leading to the induction of downstream intermediate signals, as the proposed sequence of events in PCD signalling was terminated by the animal P2 receptor antagonist suramin. 相似文献
994.
旨在制备与鉴定鼠抗P2X7受体的蛋白单克隆抗体.以人P2X7受体的胞外段制备短肽作为抗原,皮下注射免疫Balb/c小鼠.分离小鼠脾脏B淋巴细胞与骨髓瘤细胞融合并培养,挑选阳性杂交瘤细胞,扩大培养,制备和鉴定P2X7其生物学效应.结果显示,获得1株稳定分泌抗人P2X7受体的单克隆抗体的杂交瘤细胞株,所分泌的单抗类型重链为IgG1,轻链为κ;该株杂交瘤细胞腹水效价为1∶6.4×104;传30代及液氮中保存6个月,抗体效价稳定;Western blotting检测证明该单抗与人细胞表面的P2X7受体蛋白特异地结合.所制备的抗人P2X7受体的单克隆抗体具有高度的特异性及稳定性,为针对P2X7受体为靶点的抗体药物的开发应用、疾病的辅助诊断奠定了基础. 相似文献
995.
以颗粒活性炭(GAC)为吸附剂,采用多柱串联流化床进行味精中和液脱色,对柱过程进行了模拟研究。测定了平衡数据、传质动力学及流体流动参数,建立了具有广泛适应性的,包括颗粒分级、粒度分布、内外扩散及两相返混的宽粒度液固流化床吸附过程模型。对所研究体系的模拟计算与实验结果符合较好。 相似文献
996.
味觉的生理学研究进展 总被引:4,自引:0,他引:4
味觉的生理学研究进展陈建国(江苏省启东肝癌研究所,启东226200)沈福民(上海医科大学遗传医学研究中心,上海200032)目录一、味觉的生理学基础(一)味蕾的刺激活动(二)味觉阈值分类二、尝味及味感觉机理(一)尝味试验的味扰作用(二)味感觉及舌图三... 相似文献
997.
Plant regeneration through somatic embryogenesis was achieved using immature zygotic embryos (ZE) of Sorbus pohuashanensis as explants. Over 50% of immature ZEs from immature seed collected at 30 days after pollination produced direct somatic embryos
(SEs) on Murashige and Skoog (MS) medium supplemented with 0–0.44 μM 6-benzyladenine (BA) in combination with 5.73 μM naphthaleneacetic
acid (NAA) or with 0.91–2.26 μM 2,4-dichlorophenoxyacetic acid (2,4-D) alone. Fourteen to 23 SEs per explant were regenerated
on MS medium supplemented with BA 0.44 μM in combination with NAA 5.73 μM. SE formation decreased when sucrose concentrations
were higher than 40 g L−1. Repetitive embryogenesis occurred following culture on solid MS medium containing 12 μM abscisic acid, 75 g L−1 polyethylene glycol, and 20 g L−1 sucrose at 25 ± 1°C under a 16-h photoperiod with a light intensity of 40 μmol m−2 s−1. Over 40% of the mature SEs germinated on solid MS medium under light condition described previously. Up to 40% of the regenerated
plantlets were successfully acclimatized under greenhouse conditions. Plantlets derived from SEs grew vigorously with similar
morphology as those germinated from ZEs. Histological studies of explants at various developmental stages of somatic embryogenesis
revealed that SEs passed through globular, heart, torpedo, and mature stages. Similar to ZE suspensors, similar structures
of SE degenerated in later stages of embryo development. ZE and SE are a effective means of regenerating tissue culture plantlets
for S. pohuashanesis. 相似文献
998.
一个恢复力受单基因控制的水稻CMS育性回复突变体 总被引:3,自引:0,他引:3
利用 ̄(60)Co-γ射线对具有印尼水田谷细胞质的籼稻细胞质雄性不育系Ⅱ-32A干种子进行诱变处理,获得了一育性回复突变体T24。育性基因未纯合的突变体分离出可育株和完全不育株,比例为3∶1;其与Ⅱ-32A和珍汕97A测交,F1代分离出1∶1的可育株和不育株。育性稳定株系与Ⅱ-32A和珍汕97A杂交,F2分离成3∶1的可育株和不育株。表明其育性回复是由一对基因显性突变所致。这一突变体对不育系的育性恢复机制不同于明恢63、20964等恢复系,后者表现为两对显性恢复基因作用。未观察到T24与亲本Ⅱ-32A除育性以外的其他性状的差异,因而两者构成育性恢复基因的近等基因系。本文还对不育系育性回复类型和T24的理论意义与育种价值进行了讨论。 相似文献
999.
Effects of wildfire on soil respiration and its heterotrophic and autotrophic components in a montane coniferous forest 总被引:1,自引:0,他引:1
Jian Song Zhen Liu Yuan Zhang Tao Yan Zehao Shen Shilong Piao 《Journal of Plant Ecology》2019,12(2):336
Aims
Episodic wildfires are expected to occur more frequently under future climate change scenarios, with substantial effects on CO2exchange between terrestrial ecosystems and the atmosphere. This study examined the effects of wildfire on soil respiration (RS) and its heterotrophic (RH) and autotrophic (RA) components, as well as their temperature responses (temperature sensitivity,Q10). 相似文献
1000.
Comparative mapping of QTLs for agronomic traits of rice across environments by using a doubled-haploid population 总被引:11,自引:0,他引:11
Chaofu Lu Lishuuang Shen Ping He Ying Chen Lihuang Zhu Zhenbo Tan Yunbi Xu 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,94(1):145-150
We report here the RFLP mapping of quantitative trait loci (QTLs) which affect some important agronomic traits in cultivated
rice. An anther culture-derived doubled-haploid (DH) population was established from a cross between indica and japonica rice
varieties. A molecular linkage map comprising 137 markers was constructed based on this population which covered the rice
genome at intervals of 14.8 cM on average. The linkage map was used to locate QTLs for such important agronomic traits as
heading date, plant height, number of spikelets per panicle, number of grains per panicle, 1 000-grain weight and the percentage
of seed set, by interval mapping. Evidence of genotype-by-environment interaction was found by comparing QTL maps of the same
population grown in three diverse environments. A total of 22 QTLs for six agronomic traits was detected which were significant
in at least one environment, but only seven were significant in all three environments; seven were significant in two environments
and eight could only be detected in a single environment. However, QTLs-by-environment interaction was trait dependent. QTLs
for spikelets and grains per panicle were common across environments while traits like heading date and plant height were
more sensitive to environment.
Received: 22 February 1996 / Accepted: 10 May 1996 相似文献