全文获取类型
收费全文 | 487918篇 |
免费 | 55102篇 |
国内免费 | 745篇 |
出版年
2018年 | 4962篇 |
2017年 | 4852篇 |
2016年 | 6683篇 |
2015年 | 9110篇 |
2014年 | 10628篇 |
2013年 | 14704篇 |
2012年 | 18111篇 |
2011年 | 18882篇 |
2010年 | 12127篇 |
2009年 | 10607篇 |
2008年 | 16408篇 |
2007年 | 16922篇 |
2006年 | 15860篇 |
2005年 | 15046篇 |
2004年 | 14976篇 |
2003年 | 14013篇 |
2002年 | 13637篇 |
2001年 | 20194篇 |
2000年 | 20252篇 |
1999年 | 15893篇 |
1998年 | 6045篇 |
1997年 | 5982篇 |
1996年 | 5772篇 |
1995年 | 5493篇 |
1994年 | 5228篇 |
1993年 | 5195篇 |
1992年 | 12916篇 |
1991年 | 12791篇 |
1990年 | 12543篇 |
1989年 | 12008篇 |
1988年 | 11150篇 |
1987年 | 10521篇 |
1986年 | 10022篇 |
1985年 | 9836篇 |
1984年 | 8267篇 |
1983年 | 7172篇 |
1982年 | 5448篇 |
1981年 | 4911篇 |
1980年 | 4566篇 |
1979年 | 7614篇 |
1978年 | 6218篇 |
1977年 | 5549篇 |
1976年 | 5203篇 |
1975年 | 6071篇 |
1974年 | 6532篇 |
1973年 | 6328篇 |
1972年 | 5619篇 |
1971年 | 5251篇 |
1970年 | 4406篇 |
1969年 | 4335篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
871.
Charles E. Wenner John C. Cheney L. David Tomei 《Journal of cellular biochemistry》1981,15(2):161-168
The introduction of either PGF2α (10?7 M) or TPA (10?7 M) stimulated, ouabain-sensitive 86Rb+ influx at 30 min in postconfluent 3T3-4 mouse fibroblast cultures by 117% and 124%, respectively. Both TPA and PGF2α at these concentrations stimulated the incorporation of 3H-TdR into DNA. TPA had the greatest stimulatory effect, which was similar to that obtained with 10% fetal calf serum. In accord with the idea that modulation of membrane processes such as Na+/K+ pump activity in fibroblasts may reflect important events related to the initiation of DNA synthesis, it was observed that in both 3T3-4 and C3H-1 0T½ cells there were parallel increases in 3H-TdR incorporation and ouabain-sensitive 86Rb+ influxes with 10?7 M TPA, whereas PGF2α stimulated a significant increase in 3H-TdR incorporation in 3T3-4 but not C3H-10T½ cells and only marginal increases in ouabain-sensitive 86Rb+ influx in both. Therefore, although there appears to be a close correlation between Na+/K+ pump activation and subsequent S-phase entry following TPA stimulation, a similar correlation for PGF2α cannot be confirmed. 相似文献
872.
G. Ricci L. Volpi L. Pasquali L. Petrozzi G. Siciliano 《Journal of biological physics》2009,35(4):317-336
Astrocytes have long been considered as just providing trophic support for neurons in the central nervous system, but recently
several studies have highlighted their importance in many functions such as neurotransmission, metabolite and electrolyte
homeostasis, cell signaling, inflammation, and synapse modulation. Astrocytes are, in fact, part of a bidirectional crosstalk
with neurons. Moreover, increasing evidence is stressing the emerging role of astrocyte dysfunction in the pathophysiology
of neurological disorders, including neurodegenerative disease, stroke, epilepsy, migraine, and neuroinflammatory diseases. 相似文献
873.
A. V. Andriyash D. A. Vikhlyaev D. A. Dmitrov A. L. Zapysov A. G. Kakshin I. A. Kapustin E. A. Loboda V. A. Lykov A. V. Potapov V. A. Pronin V. N. Sanzhin V. N. Saprykin A. A. Ugodenko O. V. Chefonov M. N. Chizhkov 《Plasma Physics Reports》2006,32(2):135-137
Results are presented from experimental investigations of the angular distributions and energy spectra of fast ions produced in deuterium polyethylene targets under irradiation by picosecond laser pulses with intensities of up to 2 × 1018 W/cm2 in the SOKOL-P facility. The parameters of ion fluxes were measured by time-of-flight spectrometers based on semiconductor detectors. 相似文献
874.
875.
876.
877.
The Devonian cemented brachiopod Schuchertellopsis durbutensis has proved difficult to classify and its possible taxonomic relationships are unknown. Morphologically Schuchertellopsis resembles more closely members of the Orthotetidina than the Davidsoniidina. Examination of the shell structure, a key diagnostic feature of the Orthotetidina, shows that Schuchertellopsis has the cross laminar secondary shell typical of all orthotetidines. However, the presence of both pseudopunctate and incipient an extropunctate fabric within the ventral valve is unique amongst orthotetidine brachiopods and is thought to represent a phase of shell fabric experimentation. Schuchertellopsis probably fits most comfortably within the Schuchertellidae, and is the earliest representative of that family. 相似文献
878.
J. L. van Leeuwen 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》1999,354(1385):839-840
Preface to Mechanisms of neuromuscular control. A Theme organized and edited by J. L. van Leeuwen. 相似文献
879.
880.
L.E. Palma-Cano H.A. Piñon-Castillo S.H. Tarango-Rivero A. Carbon J. Salas-Leiva L.N. Muñoz-Castellanos C. Cravo-Laureau R. Duran E. Orrantia-Borunda 《Letters in applied microbiology》2021,72(5):556-569
We described the bacterial diversity of walnut grove soils under organic and conventional farming. The bacterial communities of rhizospheric and nonrhizospheric soils of pecan tree (Carya illinoensis K. Koch) were compared considering two phenological stages (sprouting and ripening). Sixteen operational taxonomic units (OTUs) were identified significantly more abundant according to the plant development, only one according to the farming condition, and none according to the soil origin. The OTUs specificaly abundant according to plant development included Actinobateria (2) and Betaproteobacteria (1) related OTUs more abundant at the sprouting stage, while at the fruit ripening (FR) stage the more abundant OTUs were related to Actinobacteria (6), Alphaproteobacteria (6), and unclassified Bacteria (1). The Gaiellaceae OTU18 (Actinobacteria) was more abundant under conventional farming. Thus, our study revealed that the plant development stage was the main factor shaping the bacterial community structure, while less influence was noticed for the farming condition. The bacterial communities exhibited specific metabolic capacities, a large range of carbon sources being used at the FR stage. The identified OTUs specifically more abundant represent indicators providing useful information on soil condition, potential tools for the management of soil bacterial communities. 相似文献