全文获取类型
收费全文 | 16754篇 |
免费 | 1529篇 |
国内免费 | 1688篇 |
出版年
2024年 | 31篇 |
2023年 | 196篇 |
2022年 | 449篇 |
2021年 | 775篇 |
2020年 | 630篇 |
2019年 | 724篇 |
2018年 | 674篇 |
2017年 | 523篇 |
2016年 | 721篇 |
2015年 | 1100篇 |
2014年 | 1278篇 |
2013年 | 1307篇 |
2012年 | 1710篇 |
2011年 | 1441篇 |
2010年 | 901篇 |
2009年 | 806篇 |
2008年 | 930篇 |
2007年 | 831篇 |
2006年 | 777篇 |
2005年 | 627篇 |
2004年 | 521篇 |
2003年 | 478篇 |
2002年 | 406篇 |
2001年 | 293篇 |
2000年 | 265篇 |
1999年 | 239篇 |
1998年 | 163篇 |
1997年 | 138篇 |
1996年 | 114篇 |
1995年 | 109篇 |
1994年 | 121篇 |
1993年 | 76篇 |
1992年 | 96篇 |
1991年 | 94篇 |
1990年 | 56篇 |
1989年 | 54篇 |
1988年 | 39篇 |
1987年 | 37篇 |
1986年 | 31篇 |
1985年 | 38篇 |
1984年 | 18篇 |
1983年 | 13篇 |
1982年 | 14篇 |
1981年 | 14篇 |
1980年 | 9篇 |
1978年 | 10篇 |
1976年 | 13篇 |
1975年 | 12篇 |
1973年 | 10篇 |
1970年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 334 毫秒
1.
2.
Ming Pei You Brandon Lancaster Krishnapillai Sivasithamparam Martin John Barbetti 《Plant and Soil》2008,302(1-2):203-211
In Australia, in the past, pasture legumes were rotated mainly with cereals, but increasingly these rotations now involve
pasture legumes with a wider range of crops, including legumes. This increasing frequency of the leguminous host in the rotation
system may be associated with increased root rots in legumes in the current pasture-crop rotations. The primary aim of this
study was to see whether the pathogenicity on pasture legumes of strains of Rhizoctonia solani sourced from lupins and cereals (common crops in rotation with pastures) is associated with increased incidence of root rots
in pasture legumes in the disease conducive sandy soils of the Mediterranean regions of southern Australia. The second aim
was to determine sources of resistance among newly introduced pasture legumes to R. solani strains originating from rotational crops as this would reduce the impact of disease in the pasture phase. Fifteen pasture
legume genotypes were assessed for their resistance/susceptibility to five different zymogram groups (ZG) of the root rot
pathogen R. solani under glasshouse conditions. Of the R. solani groups tested, ZG1–5 and ZG1–4 (both known to be pathogenic on cereals and legumes) overall, caused the most severe root
disease across the genotypes tested, significantly more than ZG6 (known to be pathogenic on legumes), in turn significantly
>ZG4 (known to be pathogenic on legumes) which in turn was >ZG11 (known to be pathogenic on legumes including tropical species).
Overall, Ornithopus sativus Brot. cvs Cadiz and Margurita, Trifolium michelianum Savi. cvs Paradana and Frontier and T. purpureum Loisel. cv. Electro showed a significant level of resistance to root rot caused by R. solani ZG11 (root disease scores ≤1.2 on a 1–3 scale where 3 = maximum disease severity) while O. sativus cvs Cadiz and Erica showed a significant level of resistance to root rot caused by R. solani ZG4 (scores ≤1.2). O. compressus L. cvs Charano and Frontier, O. sativus cv. Erica, and T. purpureum cv. Electro showed some useful resistance to root rot caused by R. solani ZG6 (scores ≤1.8). This is the first time that cvs Cadiz, Electro, Frontier, Margurita and Paradana have been recognised
for their levels of resistance to root rot caused by R. solani ZG11; and similarly for cvs Cadiz and Erica against ZG4; and for cvs Charano, Erica, and Electro against ZG6. These genotypes
with resistance may also serve as useful sources of resistance in pasture legume breeding programs and also could potentially
be exploited directly into areas where other rotation crops are affected by these R. solani strains. None of the tested genotypes showed useful resistance to R. solani ZG1–4 (scores ≥2.0) or ZG1–5 (scores ≥2.5). This study demonstrates the relative potential of the various R. solani ZG strains, and particularly ZG1–4, ZG1–5, ZG4 and ZG6 to attack legume pastures and pose a significant threat to non-pasture
crop species susceptible to these strains grown in rotation with these pasture legumes. Significantly, the cross-pathogenicity
of these strains could result in the continuous build-up of inoculum of these strains that may seriously affect the productivity
eventually of legumes in all rotations. In particular, when choosing pasture legumes as rotation crops, caution needs to be
exercised so that the cultivars deployed are those with the best resistance to the R. solani ZGs most likely to be prevalent at the location. 相似文献
3.
Fang Chang An Yan Li-Na Zhao Wei-Hua Wu Zhenbiao Yang 《植物学报(英文版)》2007,49(8):1261-1270
A tip-focused Ca^2+ gradient is tightly coupled to polarized pollen tube growth, and tip-localized influxes of extracellular Ca^2+ are required for this process. However the molecular identity and regulation of the potential Ca^2+ channels remains elusive. The present study has implicated CNGC18 (cyclic nucleotide-gated channel 18) in polarized pollen tube growth, because its overexpression induced wider and shorter pollen tubes. Moreover, CNGC18 overexpression induced depolarization of pollen tube growth was suppressed by lower extracellular calcium ([Ca^2+]ex). CNGC18-yellow fluorescence protein (YFP) was preferentially localized to the apparent post-Golgi vesicles and the plasma membrane (PM) in the apex of pollen tubes. The PM localization was affected by tip-localized ROP1 signaling. Expression of wild type ROP1 or an active form of ROP1 enhanced CNGC18-YFP localization to the apical region of the PM, whereas expression of RopGAP1 (a ROP1 deactivator) blocked the PM localization. These results support a role for PM-Iocalized CNGC18 in the regulation of polarized pollen tube growth through its potential function in the modulation of calcium influxes. 相似文献
4.
5.
6.
7.
Ying Jin Dan Long Juan Li Ruichao Yu Yueming Song Jie Fang Xi Yang Shu Zhou Shishu Huang Zhihe Zhao 《Journal of cellular physiology》2019,234(9):14838-14851
Bone and tooth, fundamental parts of the craniofacial skeleton, are anatomically and developmentally interconnected structures. Notably, pathological processes in these tissues underwent together and progressed in multilevels. Extracellular vesicles (EVs) are cell-released small organelles and transfer proteins and genetic information into cells and tissues. Although EVs have been identified in bone and tooth, particularly EVs have been identified in the bone formation and resorption, the concrete roles of EVs in bone and tooth development and diseases remain elusive. As such, we review the recent progress of EVs in bone and tooth to highlight the novel findings of EVs in cellular communication, tissue homeostasis, and interventions. This will enhance our comprehension on the skeletal biology and shed new light on the modulation of skeletal disorders and the potential of genetic treatment. 相似文献
8.
9.
W. D. Roof H. Q. Fang K. D. Young Jianling Sun & Ry Young 《Molecular microbiology》1997,25(6):1031-1046
slyD encodes a 196 amino acid polypeptide that is a member of the FKBP family of cis–trans peptidyl–prolyl isomerases (PPIases). slyD mutations affect plaque formation by the phage φX174 by blocking the action of the phage lysis protein E. Here we describe the selection of a set of spontaneous slyD mutations conferring resistance to the expression of gene E from a plasmid. These mutations occur disproportionately in residues of SlyD that, based on the structure of the prototype mammalian FKBP12, make ligand contacts with immunosuppressing drug molecules or are conserved in other FKBP proteins. A wide variation in the plating efficiency of φX174 on these E R strains is observed, relative to the parental, indicating that these alleles differ widely in residual SlyD activity. Moreover, it is found that slyD mutations cause significant growth rate defects in Escherichia coli B and C backgrounds. Finally, overexpression of slyD causes filamentation of the host. Thus, among the FKBP genes found in organisms across the evolutionary spectrum, slyD is unique in having three distinct drug-independent phenotypes. 相似文献
10.
Abstract Morphological features of mature larvae of Petelia rivulosa (Butler), Exangerona prattiaria (Leech) and Culcula panterinaria (Bremer & Grey) of Ennominae are described and illustrated. All specimens examined are deposited in the Insect Collection of Department of Forest Resources Protection, Kangwon National University, Korea. 相似文献