全文获取类型
收费全文 | 324364篇 |
免费 | 34096篇 |
国内免费 | 285篇 |
出版年
2018年 | 3386篇 |
2017年 | 3107篇 |
2016年 | 4607篇 |
2015年 | 6481篇 |
2014年 | 7033篇 |
2013年 | 10098篇 |
2012年 | 11169篇 |
2011年 | 11083篇 |
2010年 | 7241篇 |
2009年 | 6738篇 |
2008年 | 9518篇 |
2007年 | 9595篇 |
2006年 | 9079篇 |
2005年 | 9094篇 |
2004年 | 9030篇 |
2003年 | 8430篇 |
2002年 | 7866篇 |
2001年 | 12952篇 |
2000年 | 12928篇 |
1999年 | 10294篇 |
1998年 | 3772篇 |
1997年 | 3971篇 |
1996年 | 3902篇 |
1995年 | 3544篇 |
1994年 | 3493篇 |
1993年 | 3502篇 |
1992年 | 8617篇 |
1991年 | 8515篇 |
1990年 | 8151篇 |
1989年 | 8079篇 |
1988年 | 7457篇 |
1987年 | 7153篇 |
1986年 | 6547篇 |
1985年 | 6709篇 |
1984年 | 5630篇 |
1983年 | 4708篇 |
1982年 | 3657篇 |
1981年 | 3422篇 |
1980年 | 3202篇 |
1979年 | 5315篇 |
1978年 | 4110篇 |
1977年 | 3978篇 |
1976年 | 3653篇 |
1975年 | 4049篇 |
1974年 | 4429篇 |
1973年 | 4350篇 |
1972年 | 3861篇 |
1971年 | 3607篇 |
1970年 | 3221篇 |
1969年 | 3158篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
D F Morrison P J O'Brien D R Pepperberg 《The Journal of biological chemistry》1991,266(30):20118-20123
Rhodopsin, the photosensitive protein found in rod photoreceptors, has two covalently attached palmitates that are thought to anchor a portion of the C terminus to the disc membrane, forming a fourth cytoplasmic loop. Using hydroxylamine (NH2OH) to cleave the thioester linkage, we have characterized the effect of depalmitylation on certain functional properties of rhodopsin. Treatment of rod outer segment membranes (prepared from rat retinas previously labeled in vivo with [3H]palmitate) with 1 M NH2OH typically removed greater than or equal to 75% of the [3H]palmitate initially bound to rhodopsin. Spectrophotometry of rod outer segment membranes that had been treated with 1 M NH2OH indicated preservation of 85% of the native rhodopsin and no effect on the shape of the absorbance spectrum of rhodopsin. In vivo labeled rhodopsin that had been treated with 1 M NH2OH did not reincorporate free endogenous [3H] palmitate over a 2-h incubation period. Both NH2OH-treated and untreated rhodopsin incorporated [14C]palmitate from exogenously added [14C]palmitoyl-CoA. This incorporation was substantially greater in the NH2OH-treated sample. The removal of palmitate by NH2OH inhibited rhodopsin regeneration by 44% and increased the ability of rhodopsin to activate transducin's light-dependent GTPase activity by 61%. However, the removal of palmitate from rhodopsin did not affect the light-dependent binding of transducin (T alpha and T beta gamma). 相似文献
22.
G Baughman M T Harrigan N F Campbell S J Nurrish S Bourgeois 《Molecular endocrinology (Baltimore, Md.)》1991,5(5):637-644
Glucocorticoids induce dramatic biochemical and morphological changes in lymphocytes through an unknown process that requires RNA and protein synthesis. In order to identify genes involved in this response, we previously isolated 11 cDNA clones from the murine WEHI-7TG thymoma cell line that correspond to mRNAs induced by glucocorticoids. We now report the isolation of two new cDNA clones whose gene expression is regulated by glucocorticoids in WEHI-7TG cells. We further characterize the two new cDNA clones, as well as those described previously, by examining the response of each of the corresponding mRNAs to glucocorticoids in murine thymocytes. With the exception of two, all cDNAs correspond to genes that are induced by glucocorticoids in murine thymocytes within 4 h of treatment. We previously identified two of the cDNAs as the mouse VL30 retrovirus-like element and the mouse homolog of chondroitin sulfate proteoglycan core protein. We have now identified four additional cDNA clones that correspond to the genes for calmodulin, mitochondrial phosphate carrier protein, immunoglobulin (Ig)-related glycoprotein (GP-70), and the 70 kilodalton autoantigen for Lupus and Graves diseases. Two other cDNA clones represent previously undescribed genes: one shares a high similarity to known sequences for the family of G-protein-coupled receptors and the other to a human placental-specific protein, PP11. Another cDNA appears to contain sequences for an unknown gene and the remnants of a mouse transposon. ETn. The remaining clones represent new, unidentified genes induced by glucocorticoids in murine thymocytes and in the WEHI-7TG cell line. 相似文献
23.
24.
25.
26.
27.
Cellular and molecular physiology of volume-sensitive anion channels 总被引:39,自引:0,他引:39
Strange K.; Emma F.; Jackson P. S. 《American journal of physiology. Cell physiology》1996,270(3):C711
28.
F N Bamford 《BMJ (Clinical research ed.)》1996,313(7058):672-673
29.
M. Pons M. García A. Borell F. Garcia J. Egozcue M. A. Gorostiaga A. Delprat M. Mudry 《American journal of primatology》1995,37(4):325-331
Cytogenetic studies have been carried out in 39 specimens of C. apella of different origins. Three different morphologies, one affecting the long arm of chromosome 4 and two affecting pair 17, have been detected. In each case, they can be related by paracentric inversions. Heterochromatin polymorphisms affecting terminal or interstitial C+ regions have also been observed. The length of the terminal heterochromatic region in the long arms of chromosome 11 is variable in C. apella sp., in C. a. paraguayanus and absent in the C. a. nigritus specimens studied. Interstitial C + bands can be observed in the long arms of the biarmed chromosomes 4 and 6, and in the long arms of the acrocentric pairs 12, 13, 17, 18, 19, 20, and 21. Interstitial C + bands in the long arms of chromosomes 4, 12, 17, and 19 are present in all animals studied, although their size is variable, especially in the case of chromosomes 17 and 19. © 1995 Wiley-Liss, Inc. 相似文献
30.
Modulation of K+ channels by hydrogen peroxide. 总被引:7,自引:0,他引:7
E Vega-Saenz de Miera B Rudy 《Biochemical and biophysical research communications》1992,186(3):1681-1687
External application of hydrogen peroxide (H2O2) was found to inhibit the time-dependent fast inactivation process of three cloned voltage-gated K+ channels expressed in Xenopus oocytes: KShIIIC, KShIIID and HukII. As expected from kinetic models where some channels are still opening while a significant fraction of channels is already inactivated there was a large increase in current magnitude concomitant to inactivation block. The channels otherwise functioned normally. The effects of H2O2 were specific (other cloned voltage-gated K+ channels were not affected), and reversible, the currents returned to normal upon removal of the H2O2. H2O2 is produced during normal metabolism; it could act as a modulator of excitability through effects on K+ channels if effective local concentrations are reached in neuronal regions close to the channel. KShIIIC and KShIIID currents are very similar to an O2-sensitive K+ current present in type I cells of the carotid body which is believed to underlie the modulation of excitability of these cells by changes in arterial O2 pressure. H2O2 has been proposed as an intermediary between O2 and cellular response in the carotid body; our results provide support for this model. 相似文献