全文获取类型
收费全文 | 7529篇 |
免费 | 571篇 |
国内免费 | 910篇 |
出版年
2024年 | 16篇 |
2023年 | 112篇 |
2022年 | 137篇 |
2021年 | 220篇 |
2020年 | 202篇 |
2019年 | 225篇 |
2018年 | 240篇 |
2017年 | 208篇 |
2016年 | 215篇 |
2015年 | 235篇 |
2014年 | 290篇 |
2013年 | 465篇 |
2012年 | 257篇 |
2011年 | 276篇 |
2010年 | 238篇 |
2009年 | 287篇 |
2008年 | 307篇 |
2007年 | 358篇 |
2006年 | 374篇 |
2005年 | 346篇 |
2004年 | 269篇 |
2003年 | 361篇 |
2002年 | 294篇 |
2001年 | 243篇 |
2000年 | 204篇 |
1999年 | 220篇 |
1998年 | 172篇 |
1997年 | 203篇 |
1996年 | 187篇 |
1995年 | 169篇 |
1994年 | 198篇 |
1993年 | 190篇 |
1992年 | 151篇 |
1991年 | 147篇 |
1990年 | 136篇 |
1989年 | 130篇 |
1988年 | 122篇 |
1987年 | 106篇 |
1986年 | 72篇 |
1985年 | 82篇 |
1984年 | 68篇 |
1983年 | 42篇 |
1982年 | 52篇 |
1981年 | 41篇 |
1980年 | 34篇 |
1979年 | 28篇 |
1978年 | 15篇 |
1977年 | 14篇 |
1976年 | 18篇 |
1973年 | 9篇 |
排序方式: 共有9010条查询结果,搜索用时 15 毫秒
81.
Mortimer M. Civan Stephen R. Williams David G. Gadian Enrique Rozengurt 《The Journal of membrane biology》1986,94(1):55-64
Summary Swiss mouse 3T3 cells grown on microcarrier beads were superfused with electrolyte solution during continuous NMR analysis. Conventional31P and19F probes of intracellular pH (pH
c
) were found to be impracticable. Cells were therefore superfused with 1 to 4mm 2-deoxyglucose, producing a large intracellular, pH-sensitive signal of 2-deoxyglucose phosphate (2DGP). The intracellular incorporation of 2DGP inhibited the Embden-Meyerhof pathway. However, intracellular ATP was at least in part retained and the cellular responsivity to changes in extracellular ionic composition and to the application of growth factors proved intact. Transient replacement of external Na+ with choline or K+ reversibly acidified the intracellular fluids. Quiescent cells and mitogenically stimulated cells displayed the same dependence of shifts in pH
c
on external Na+ concentration (c
Na
o
). pH
c
also depended on intracellular Na+ concentration (c
Na
o
). Increasingc
Na
c
by withdrawing external K+ (thereby inhibiting the Na,K-pump) caused reversible intracellular acidification; subsequently reducingc
Na
o
produced a larger acid shift in pH
c
than with external K+ present. Comparison of separate preparations indicated that pH
c
was higher in stimulated than in quiescent cells. Transient administration of mitogens also reversibly alkalinized quiescent cells studied continuously. This study documents the feasibility of monitoring pH
c
of Swiss mouse 3T3 cells using31P NMR analysis of 2DGP. The results support the concept of a Na/H antiport operative in these cells, both in quiescence and after mitogenic stimulation. The data document by an independent technique that cytoplasmic alkalinization is an early event in mitogenesis, and that full activity of the Embden-Meyerhof pathway is not required for the expression of this event. 相似文献
82.
Effects of several population densities ofMeloidogyne incognita on the sweet potato cultivars Centennial (susceptible) and Jasper (moderately resistant) were studied. Field plots were infested with initial levels (Pi) of 0, 10, 100, 1,000, 5,000, and 10,000 eggs and juveniles/500 cm³ soil in 1980 and 0, 100, 1,000, 2,000, 3,000, 4,000, and 5,000 in 1981. M. incognita population development trends were similar on both cultivars; however, at high Pi, more eggs and juveniles were recovered from Centennial than from Jasper. The highest Pi did not result in the highest mid-season (Pm) counts. Pi was negatively correlated with the number of marketable roots and root weight but positively correlated with total cracked roots, percentage of cracked roots, and cracking severity. Jasper tolerated higher Pi with greater yields and better root quality than Centennial. Cracking of fleshy roots occurred with both cultivars at low Pi. 相似文献
83.
84.
85.
86.
87.
88.
Three naphthoquinone pigments are described which were produced by Fusarium solani. They are 2,3-dihydro-5,8-dihydroxy-6-methoxy-2-hydroxymethyl-3-(2-hydroxypropyl)-1,4-naphthalenedione, 2,3-dihydro-5-hydroxy-4-hydroxymethyl-8-methoxy-naphtho[1,2-b]furan-6,9-dione and 5,8-dihydroxy-2-methoxy-6-hydroxymethyl-7-(2-hydroxypropyl)-1,4-naphthalenedione. One of these pigments was shown to be the precursor of the other two. 相似文献
89.
90.
Internal transport of O2 from the aerial tissues along the adventitious roots of intact maize plants was estimated by measuring the concentrations of adenine nucleotides in various zones along the root under an oxygen-free atmosphere. Young maize plants were grown in nutrient solution under conditions that either stimulated or prevented the formation of a lysigenous aerenchyma, and the roots (up to 210 mm long) were then exposed to an anaerobic (oxygen-free) nutrient solution. Aerenchymatous roots showed higher values than non-aerenchymatous ones for ATP content, adenylate energy charge and ATP/ADP ratios. We conclude that the lysigenous cortical gas spaces help maintain a high respiration rate in the tissues along the root, and in the apical zone, by improving internal transport of oxygen over distances of at least 210 mm. This contrasted sharply with the low energy status (poor O2 transport) in non-aerenchymatous roots.Abbreviation AEC
adenylate energy charge 相似文献