全文获取类型
收费全文 | 2127篇 |
免费 | 135篇 |
专业分类
2262篇 |
出版年
2023年 | 8篇 |
2022年 | 18篇 |
2021年 | 36篇 |
2020年 | 14篇 |
2019年 | 22篇 |
2018年 | 31篇 |
2017年 | 20篇 |
2016年 | 47篇 |
2015年 | 94篇 |
2014年 | 87篇 |
2013年 | 111篇 |
2012年 | 153篇 |
2011年 | 159篇 |
2010年 | 90篇 |
2009年 | 83篇 |
2008年 | 118篇 |
2007年 | 123篇 |
2006年 | 114篇 |
2005年 | 92篇 |
2004年 | 114篇 |
2003年 | 108篇 |
2002年 | 97篇 |
2001年 | 31篇 |
2000年 | 18篇 |
1999年 | 30篇 |
1998年 | 29篇 |
1997年 | 25篇 |
1996年 | 19篇 |
1995年 | 16篇 |
1994年 | 17篇 |
1993年 | 22篇 |
1992年 | 23篇 |
1991年 | 18篇 |
1990年 | 22篇 |
1989年 | 32篇 |
1988年 | 13篇 |
1987年 | 11篇 |
1986年 | 16篇 |
1985年 | 14篇 |
1984年 | 23篇 |
1983年 | 17篇 |
1982年 | 9篇 |
1981年 | 15篇 |
1980年 | 7篇 |
1979年 | 16篇 |
1978年 | 11篇 |
1977年 | 8篇 |
1974年 | 6篇 |
1971年 | 6篇 |
1967年 | 6篇 |
排序方式: 共有2262条查询结果,搜索用时 0 毫秒
11.
The results of genome analysis of five hybrids, viz.Elymus patagonicus ×Hordeum procerum, E. patagonicus ×H. tetraploidum, E. angulatus ×H. jubatum, E. angulatus ×H. lechleri, andE. angulatus ×H. parodii, are reported. The genomic constitution ofHordeum tetraploidum andH. jubatum is best given as H1H1H2H2, ofH. lechleri andH. parodii as H1H1H2H2H4H4, ofH. procerum as H1H1H2H2H3H3, and ofElymus patagonicus andE. angulatus as SSH1H1H2H2. 相似文献
12.
Else K. Hoffmann Ian H. Lambert Lars Ole Simonsen 《The Journal of membrane biology》1986,91(3):227-244
Summary The net loss of KCl observed in Ehrlich ascites cells during regulatory volume decrease (RVD) following hypotonic exposure involves activation of separate conductive K+ and Cl– transport pathways. RVD is accelerated when a parallel K+ transport pathway is provided by addition of gramicidin, indicating that the K+ conductance is rate limiting. Addition of ionophore A23187 plus Ca2+ also activates separate K+ and Cl– transport pathways, resulting in a hyperpolarization of the cell membrane. A calculation shows that the K+ and Cl– conductance is increased 14-and 10-fold, respectively. Gramicidin fails to accelerate the A23187-induced cell shrinkage, indicating that the Cl– conductance is rate limiting. An A23187-induced activation of42K and36Cl tracer fluxes is directly demonstrated. RVD and the A23187-induced cell shrinkage both are: (i) inhibited by quinine which blocks the Ca2+-activated K+ channel. (ii) unaffected by substitution of NO
3
–
or SCN– for Cl–, and (iii) inhibited by the anti-calmodulin drug pimozide. When the K+ channel is blocked by quinine but bypassed by addition of gramicidin, the rate of cell shrinkage can be used to monitor the Cl– conductance. The Cl– conductance is increased about 60-fold during RVD. The volume-induced activation of the Cl– transport pathway is transient, with inactivation within about 10 min. The activation induced by ionophore A23187 in Ca2+-free media (probably by release of Ca2+ from internal stores) is also transient, whereas the activation is persistent in Ca2+-containing media. In the latter case, addition of excess EGTA is followed by inactivation of the Cl– transport pathway. These findings suggest that a transient increase in free cytosolic Ca2+ may account for the transient activation of the Cl– transport pathway. The activated anion transport pathway is unselective, carrying both Cl–, Br–, NO
3
–
, and SCN–. The anti-calmodulin drug pimozide blocks the volume- or A23187-induced Cl– transport pathway and also blocks the activation of the K+ transport pathway. This is demonstrated directly by42K flux experiments and indirectly in media where the dominating anion (SCN–) has a high ground permeability. A comparison of the A23187-induced K+ conductance estimated from42K flux measurements at high external K+, and from net K– flux measurements suggests single-file behavior of the Ca2+-activated K+ channel. The number of Ca2+-activated K+ channels is estimated at about 100 per cell. 相似文献
13.
Summary The effect of cholecystokinin (CCK) and internal Ca2+ on outward K+ current in isolated pig pancreatic acinar cells has been investigated using the patch-clamp method for whole-cell current recording under voltage-clamp conditions. CCK (2 × 10–10
M) applied to the bath evoked a marked increase in the outward K+ current associated with depolarizing voltage steps, and this effect was fully reversible and acutely dependent on the presence of external Ca2+. When strongly buffered Ca2+-EGTA solutions were used inside the cells CCK failed to evoke an effect. Increasing the internal Ca2+ concentration ([Ca2+]
i
) from 5 × 10–10
M to 10–7 and 5 × 10–7
M mimicked the effect of CCK. It would appear therefore that CCK controls K+ conductance in the acinar cells via changes in the internal free ionized Ca2+ concentration. 相似文献
14.
The regional distribution of L-homocysteine (Hcy) was determined in brains from mouse, rat, guinea pig, and rabbit, using a sensitive radioenzymatic assay. Large interspecies variations in the Hcy content in various parts of the brain were observed, but cerebellum contained the highest amount in all species investigated. In the rat the amount of Hcy in cerebellum (6.4 nmol/g) was about sixfold higher than in most other parts of the brain, whereas in the mouse and guinea pig the amount in cerebellum (about 1 nmol/g) was only twofold higher than in the other brain regions. There was a remarkably high level of Hcy in all regions of the rabbit brain (4-10 nmol/g); the highest concentration was found in the cerebellar white matter. In this species the amount of Hcy in all brain regions examined exceeded that in the liver. 相似文献
15.
16.
Ole G. Mouritsen 《生物化学与生物物理学报:生物膜》1983,731(2):217-221
The gel-to-fluid first-order melting transition of lipid bilayers is simulated by the use of a microscopic interaction model which includes a variable number of lipid-chain conformational states. The results suggest that the experimental observation of ‘continuous melting’ in pure wet lipid bilayers, rather than being ascribed to the presence of impurities, may be explained as a result of kinetically caused metastability of intermediate lipid-chain conformations. 相似文献
17.
Na+, Cl− cotransport in Ehrlich ascites tumor cells activated during volume regulation (regulatory volume increase) 总被引:2,自引:0,他引:2
Else K. Hoffmann Carsten Sjøholm Lars Ole Simonsen 《The Journal of membrane biology》1983,76(3):269-280
Ehrlich ascites cells were preincubated in hypotonic medium with subsequent restoration of tonicity. After the initial osmotic shrinkage the cells recovered their volume within 5 min with an associated KCl uptake. The volume recovery was inhibited when NO-3 was substituted for Cl-, and when Na+ was replaced by K+, or by choline (at 5 mM external K+). The volume recovery was strongly inhibited by furosemide and bumetanide, but essentially unaffected by DIDS. The net uptake of Cl- was much larger than the value predicted from the conductive Cl- permeability. The undirectional 36Cl flux, which was insensitive to bumetanide under steady-state conditions, was substantially increased during regulatory volume increase, and showed a large bumetanide-sensitive component. During volume recovery the Cl- flux ratio (influx/efflux) for the bumetanide-sensitive component was estimated at 1.85, compatible with a coupled uptake of Na+ and Cl-, or with an uptake via a K+,Na+,2Cl- cotransport system. The latter possibility is unlikely, however, because a net uptake of KCl was found even at low external K+, and because no K+ uptake was found in ouabain-poisoned cells. In the presence of ouabain a bumetanide-sensitive uptake during volume recovery of Na+ and Cl- in nearly equimolar amounts was demonstrated. It is proposed that the primary process during the regulatory volume increase is an activation of an otherwise quiescent, bumetanide-sensitive Na+,Cl- cotransport system with subsequent replacement of Na+ by K+ via the Na+/K+ pump, stimulated by the Na+ influx through the Na+,Cl- cotransport system. 相似文献
18.
Delayed type hypersensitivity against antigens of Fasciola hepatica has been repeatedly documented in infected hosts. Evidence has been presented to suggest that the delayed reactivity may develop earlier in the regional lymph nodes of the parasitized organ than in other lymph nodes of the body (Soulsby 1971). 相似文献
19.
Effects of Red and Far-Red Light on the Hypocotyl of Picea Abies 总被引:1,自引:0,他引:1
20.