全文获取类型
收费全文 | 26005篇 |
免费 | 3046篇 |
国内免费 | 9篇 |
出版年
2022年 | 184篇 |
2021年 | 507篇 |
2020年 | 290篇 |
2019年 | 358篇 |
2018年 | 449篇 |
2017年 | 392篇 |
2016年 | 642篇 |
2015年 | 1027篇 |
2014年 | 1151篇 |
2013年 | 1387篇 |
2012年 | 1559篇 |
2011年 | 1693篇 |
2010年 | 1044篇 |
2009年 | 904篇 |
2008年 | 1270篇 |
2007年 | 1229篇 |
2006年 | 1025篇 |
2005年 | 1033篇 |
2004年 | 1021篇 |
2003年 | 883篇 |
2002年 | 827篇 |
2001年 | 593篇 |
2000年 | 630篇 |
1999年 | 539篇 |
1998年 | 271篇 |
1997年 | 264篇 |
1996年 | 238篇 |
1995年 | 255篇 |
1994年 | 238篇 |
1993年 | 213篇 |
1992年 | 421篇 |
1991年 | 423篇 |
1990年 | 417篇 |
1989年 | 367篇 |
1988年 | 352篇 |
1987年 | 325篇 |
1986年 | 276篇 |
1985年 | 293篇 |
1984年 | 269篇 |
1983年 | 235篇 |
1982年 | 183篇 |
1981年 | 191篇 |
1979年 | 244篇 |
1978年 | 214篇 |
1977年 | 204篇 |
1976年 | 197篇 |
1975年 | 196篇 |
1974年 | 185篇 |
1973年 | 203篇 |
1972年 | 187篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Gail V. W. Johnson 《Journal of neurochemistry》1992,59(6):2056-2062
The effects of cyclic AMP-dependent protein kinase (cAMP-PK) or Ca2+/calmodulin-dependent protein kinase II (CaMKII) phosphorylation on the binding of bovine tau to tubulin and calpain-mediated degradation of tau were studied. Both cAMP-PK and CaMKII readily phosphorylated tau and slowed the migration of tau on sodium dodecyl sulfate-containing polyacrylamide gels. However, cAMP-PK phosphorylated tau to a significantly greater extent than CaMKII (1.5 and 0.9 mol of 32P/mol of tau, respectively), and phosphorylation of tau by cAMP-PK resulted in a greater shift to a more acidic, less heterogeneous pattern on two-dimensional nonequilibrium pH gradient gels compared with CaMKII phosphorylation. Two-dimensional phosphopeptide maps indicate that cAMP-PK phosphorylates a site or sites on tau that are phosphorylated by CaMKII, as well as a unique site or sites that are not phosphorylated by CaMKII. Phosphorylation of tau by cAMP-PK significantly decreased tubulin binding and, as previously reported, also inhibited the calpain-induced degradation of tau. CaMKII phosphorylation of tau did not alter either of these parameters. These results suggest that the phosphorylation of site(s) on the tau molecule uniquely accessible to cAMP-PK contributed to the decreased tau-tubulin binding and increased resistance to calpain hydrolysis. 相似文献
992.
David Sherod Geoffrey Johnson Rodney Balhorn Vaughn Jackson Roger Chalkley Daryl Granner 《Biochimica et Biophysica Acta (BBA)/General Subjects》1975,381(2):337-347
N-Bromosuccinimide cleavage of in vivo 32P-labelled lysine-rich histone isolated from rapidly dividing cells has been studied. N-Bromosuccinimide cleaves F1-histone into two fragments, a small N-terminal piece and a larger C-terminal portion. The phosphate-induced microheterogeneity and associated radioactivity which has been linked to cell replication, is found in the carboxyterminal fragment. No phosphorous is found associated with the amino-terminal fragment when histone phosphorylation is associated with cell division. The specific tryptic phosphopeptides obtained from in vivo labelled F1 are clearly different from those obtained from in vitro incubations of free F1-histone and cytoplasmic protein kinase. 相似文献
993.
We examined Cortisol (F) dynamics in female baboons treated with diethylstilbestrol (DES) or estradiol (E2) and compared values with those previously measured in nonpregnant and pregnant animals. Five regularly menstruating baboons (12–18 kg, BW) were administered 5 mg DES daily via fruit or 0.5 mg E2/0.1ml oil sc for 30 days. Blood samples, obtained before and after treatment, were assayed for serum F concentrations and serum Cortisol binding capacity (CBC). The metabolic clearance (MCR) and production rate (PR) of F and the catabolism of i.v. administered [3H] F were examined 25 and 30 days after initiation of estrogen treatment. Compared with values in nonpregnant baboons, F metabolism in estrogen treated animals is significantly altered and is characterized by increased formation of unconjugated metabolites, decreased glucuronylation, increased excretion of unconjugated F, cortisone, and highly polar metabolites, and increased CBC. These changes induced by estrogen are similar to those observed in intact pregnant baboons and permit the suggestion that the pattern of F metabolism and the level of CBC in baboon pregnancy are the result of elevated estrogen production.However, estrogen also caused a significant decrease in the MCR and PR of F, parameters which, by contrast, are similar in intact pregnant and nonpregnant baboons. These findings indicate that while estrogen also influences the rate of F clearance and F production, these effects of estrogen are not apparent during pregnancy. Collectively, these findings allow the suggestion that estrogen is a major factor which alters F metabolism and increases serum CBC in baboon gestation. However, additional factors are operative in primate pregnancy which maintain PR and MCR of F at levels similar to those of nonpregnant baboons. 相似文献
994.
995.
Naohide Yamamoto John W. Philbeck Adam J. Woods Daniel A. Gajewski Joeanna C. Arthur Samuel J. Potolicchio Jr Lucien Levy Anthony J. Caputy 《PloS one》2014,9(5)
Path integration is a process in which observers derive their location by integrating self-motion signals along their locomotion trajectory. Although the medial temporal lobe (MTL) is thought to take part in path integration, the scope of its role for path integration remains unclear. To address this issue, we administered a variety of tasks involving path integration and other related processes to a group of neurosurgical patients whose MTL was unilaterally resected as therapy for epilepsy. These patients were unimpaired relative to neurologically intact controls in many tasks that required integration of various kinds of sensory self-motion information. However, the same patients (especially those who had lesions in the right hemisphere) walked farther than the controls when attempting to walk without vision to a previewed target. Importantly, this task was unique in our test battery in that it allowed participants to form a mental representation of the target location and anticipate their upcoming walking trajectory before they began moving. Thus, these results put forth a new idea that the role of MTL structures for human path integration may stem from their participation in predicting the consequences of one''s locomotor actions. The strengths of this new theoretical viewpoint are discussed. 相似文献
996.
Herpes simplex virus (HSV) and other alphaherpesviruses must move from sites of latency in ganglia to peripheral epithelial cells. How HSV navigates in neuronal axons is not well understood. Two HSV membrane proteins, gE/gI and US9, are key to understanding the processes by which viral glycoproteins, unenveloped capsids, and enveloped virions are transported toward axon tips. Whether gE/gI and US9 function to promote the loading of viral proteins onto microtubule motors in neuron cell bodies or to tether viral proteins onto microtubule motors within axons is not clear. One impediment to understanding how HSV gE/gI and US9 function in axonal transport relates to observations that gE−, gI−, or US9− mutants are not absolutely blocked in axonal transport. Mutants are significantly reduced in numbers of capsids and glycoproteins in distal axons, but there are less extensive effects in proximal axons. We constructed HSV recombinants lacking both gE and US9 that transported no detectable capsids and glycoproteins to distal axons and failed to spread from axon tips to adjacent cells. Live-cell imaging of a gE−/US9− double mutant that expressed fluorescent capsids and gB demonstrated >90% diminished capsids and gB in medial axons and no evidence for decreased rates of transport, stalling, or increased retrograde transport. Instead, capsids, gB, and enveloped virions failed to enter proximal axons. We concluded that gE/gI and US9 function in neuron cell bodies, in a cooperative fashion, to promote the loading of HSV capsids and vesicles containing glycoproteins and enveloped virions onto microtubule motors or their transport into proximal axons. 相似文献
997.
998.
999.
Photoaffinity labels for estrogen binding proteins of rat uterus 总被引:5,自引:0,他引:5
1000.