全文获取类型
收费全文 | 4012篇 |
免费 | 272篇 |
国内免费 | 6篇 |
出版年
2021年 | 19篇 |
2020年 | 17篇 |
2019年 | 29篇 |
2018年 | 53篇 |
2017年 | 54篇 |
2016年 | 78篇 |
2015年 | 108篇 |
2014年 | 125篇 |
2013年 | 271篇 |
2012年 | 192篇 |
2011年 | 192篇 |
2010年 | 121篇 |
2009年 | 122篇 |
2008年 | 202篇 |
2007年 | 216篇 |
2006年 | 200篇 |
2005年 | 209篇 |
2004年 | 200篇 |
2003年 | 205篇 |
2002年 | 194篇 |
2001年 | 112篇 |
2000年 | 114篇 |
1999年 | 112篇 |
1998年 | 55篇 |
1997年 | 49篇 |
1996年 | 59篇 |
1995年 | 53篇 |
1994年 | 53篇 |
1993年 | 52篇 |
1992年 | 104篇 |
1991年 | 64篇 |
1990年 | 63篇 |
1989年 | 54篇 |
1988年 | 44篇 |
1987年 | 40篇 |
1986年 | 33篇 |
1985年 | 55篇 |
1984年 | 48篇 |
1983年 | 29篇 |
1982年 | 38篇 |
1981年 | 26篇 |
1980年 | 27篇 |
1979年 | 19篇 |
1978年 | 17篇 |
1977年 | 18篇 |
1976年 | 20篇 |
1975年 | 18篇 |
1974年 | 15篇 |
1973年 | 22篇 |
1970年 | 10篇 |
排序方式: 共有4290条查询结果,搜索用时 31 毫秒
21.
Consciousness is an emergent property of the complex brain network. In order to understand how consciousness is constructed, neural interactions within this network must be elucidated. Previous studies have shown that specific neural interactions between the thalamus and frontoparietal cortices; frontal and parietal cortices; and parietal and temporal cortices are correlated with levels of consciousness. However, due to technical limitations, the network underlying consciousness has not been investigated in terms of large-scale interactions with high temporal and spectral resolution. In this study, we recorded neural activity with dense electrocorticogram (ECoG) arrays and used the spectral Granger causality to generate a more comprehensive network that relates to consciousness in monkeys. We found that neural interactions were significantly different between conscious and unconscious states in all combinations of cortical region pairs. Furthermore, the difference in neural interactions between conscious and unconscious states could be represented in 4 frequency-specific large-scale networks with unique interaction patterns: 2 networks were related to consciousness and showed peaks in alpha and beta bands, while the other 2 networks were related to unconsciousness and showed peaks in theta and gamma bands. Moreover, networks in the unconscious state were shared amongst 3 different unconscious conditions, which were induced either by ketamine and medetomidine, propofol, or sleep. Our results provide a novel picture that the difference between conscious and unconscious states is characterized by a switch in frequency-specific modes of large-scale communications across the entire cortex, rather than the cessation of interactions between specific cortical regions. 相似文献
22.
23.
24.
25.
26.
The aim of this study was to investigate the effects of the relaxation of the gluten network on pasta rehydration kinetics. The moisture content of pasta, under conditions where the effects of the diffusion of water on the moisture content were negligible, was estimated by extrapolating the average moisture content of pasta of various diameters to 0?mm. The moisture content of imaginary, infinitely thin pasta did not reach equilibrium even after 1?h of rehydration. The rehydration of pasta made of only gluten was also measured. The rate constants estimated by the Long and Richman equation for both the pasta indicated that the rehydration kinetics of infinitely thin pasta were similar to those of gluten pasta. These results suggest that the swelling of starch by fast gelatinization was restricted by the honeycomb structural network of gluten and the relaxation of the gluten network controlled pasta rehydration kinetics. 相似文献
27.
S Hasegawa 《Seikagaku. The Journal of Japanese Biochemical Society》1966,38(5):234-241
28.
Nobukazu Suganuma Satoru Ito Hiromichi Aso Masashi Kondo Mitsuo Sato Masahiro Sokabe Yoshinori Hasegawa 《PloS one》2012,7(9)
It is suggested that migration of airway smooth muscle (ASM) cells plays an important role in the pathogenesis of airway remodeling in asthma. Increases in intracellular Ca2+ concentrations ([Ca2+]i) regulate most ASM cell functions related to asthma, such as contraction and proliferation. Recently, STIM1 was identified as a sarcoplasmic reticulum (SR) Ca2+ sensor that activates Orai1, the Ca2+ channel responsible for store-operated Ca2+ entry (SOCE). We investigated the role of STIM1 in [Ca2+]i and cell migration induced by platelet-derived growth factor (PDGF)-BB in human ASM cells. Cell migration was assessed by a chemotaxis chamber assay. Human ASM cells express STIM1, STIM2, and Orai1 mRNAs. SOCE activated by thapsigargin, an inhibitor of SR Ca2+-ATPase, was significantly blocked by STIM1 siRNA and Orai1 siRNA but not by STIM2 siRNA. PDGF-BB induced a transient increase in [Ca2+]i followed by sustained [Ca2+]i elevation. Sustained increases in [Ca2+]i due to PDGF-BB were significantly inhibited by a Ca2+ chelating agent EGTA or by siRNA for STIM1 or Orai1. The numbers of migrating cells were significantly increased by PDGF-BB treatment for 6 h. Knockdown of STIM1 and Orai1 by siRNA transfection inhibited PDGF-induced cell migration. Similarly, EGTA significantly inhibited PDGF-induced cell migration. In contrast, transfection with siRNA for STIM2 did not inhibit the sustained elevation of [Ca2+]i or cell migration induced by PDGF-BB. These results demonstrate that STIM1 and Orai1 are essential for PDGF-induced cell migration and Ca2+ influx in human ASM cells. STIM1 could be an important molecule responsible for airway remodeling. 相似文献
29.
We isolated five polymorphic microsatellite loci from the drepanosiphid aphid Tuberculatus quercicola (Matsumura) that is associated with the Daimyo oak, Quercus dentata Thunberg, using the magnetic particles method. The isolated loci were polymorphic, with four to 16 alleles in 40 aphids. Expected heterozygosities ranged from 0.4 to 0.82. These loci can be used to quantify seasonal changes in clonal diversity in the metapopulation and the extent of clonal mixing in the colonies. 相似文献
30.