全文获取类型
收费全文 | 11894篇 |
免费 | 949篇 |
国内免费 | 338篇 |
出版年
2023年 | 90篇 |
2022年 | 104篇 |
2021年 | 336篇 |
2020年 | 289篇 |
2019年 | 350篇 |
2018年 | 402篇 |
2017年 | 317篇 |
2016年 | 423篇 |
2015年 | 679篇 |
2014年 | 792篇 |
2013年 | 861篇 |
2012年 | 1079篇 |
2011年 | 1019篇 |
2010年 | 643篇 |
2009年 | 541篇 |
2008年 | 728篇 |
2007年 | 648篇 |
2006年 | 534篇 |
2005年 | 489篇 |
2004年 | 508篇 |
2003年 | 397篇 |
2002年 | 316篇 |
2001年 | 252篇 |
2000年 | 211篇 |
1999年 | 206篇 |
1998年 | 93篇 |
1997年 | 62篇 |
1996年 | 54篇 |
1995年 | 62篇 |
1994年 | 59篇 |
1993年 | 44篇 |
1992年 | 81篇 |
1991年 | 75篇 |
1990年 | 55篇 |
1989年 | 48篇 |
1988年 | 35篇 |
1987年 | 24篇 |
1986年 | 27篇 |
1985年 | 25篇 |
1984年 | 12篇 |
1983年 | 17篇 |
1982年 | 13篇 |
1980年 | 20篇 |
1979年 | 19篇 |
1978年 | 12篇 |
1977年 | 18篇 |
1975年 | 14篇 |
1974年 | 16篇 |
1970年 | 12篇 |
1969年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Jong Il Rhee Tae-Hyoung Kang Kum-Il Lee Ok-Jae Sohn Sun-Yong Kim Sang-Wook Chung 《Biotechnology and Bioprocess Engineering》2006,11(5):432-441
2D fluorescence sensors produce a great deal of spectral data during fermentation processes, which can be analyzed using a
variety of statistical techniques. Principal component analysis (PCA) and a self-organizing map (SOM) were used to analyze
these 2D fluorescence spectra and to extract useful information from them. PCA resulted in scores and loadings that were visualized
in the score-loading plots and used to monitor various fermentation processes with recombinantEscherichia coli andSaccharomyces cerevisiae. The SOM was found to be a useful and interpretative method of classifying the entire gamut of 2D fluorescence spectra and
of selecting some significant combinations of excitation and emission wavelengths. The results, including the normalized weights
and variances, indicated that the SOM network is capable of being used to interpret the fermentation processes monitored by
a 2D fluorescence sensor. 相似文献
82.
83.
Byung-Kook Choi Sang-Hee Jeong Joon-Hyung Cho Hyo-Sook Shin Seong-Wan Son Young-Keun Yeo Hwan-Goo Kang 《Mycotoxin Research》2013,29(3):185-192
Mice were exposed to deoxynivalenol (DON) via drinking water at a concentration of 2 mg/L for 36 days. On day 8 of treatment, inactivated porcine parvovirus vaccine (PPV) was injected intraperitoneally. The relative and absolute weight of the spleen was significantly decreased in the DON-treated group (DON). Antibody titers to parvovirus in serum were 47.9?±?2.4 in the vaccination group (Vac), but 15.2?±?6.5 in the group treated with DON and vaccine (DON?+?Vac). The IgA and IgG was not different in the DON, Vac an,d DON?+?Vac groups. IgM was significantly lower only in the DON?+?Vac group. However IgE was significantly increased in the Vac and DON?+?Vac group, but no change was observed between the Vac and DON?+?Vac groups. The concentrations of IL-2, IL-4, GM-CSF, MCP-1 and Rantes in serum, and IL-1α in mesenteric lymph node and MIP-1β in spleen were significantly increased by DON treatment compared to control. The concentrations of IL-2, IL-5, IL-6, IL-9, IL-12, IL-13 and Rantes in thymus, of IL-2 in spleen, and of IL-1α, IL-1β, IL-3, IL-5, IL-10, IL-17, G-CSF, GM-CSF and MCP-1 in mesenteric lymph nodes were significantly decreased in mice compared to those in the Vac group, while concentrations of IL-1α, IL-2, IL-9, IL-13,G-CSF, GM-CSF, IFN-γ, MCP-1, MIP-1α and TNF-α were significantly increased in serum compared to the Vac group. In conclusion, the results presented here indicate that exposure to DON at 2.0 mg/L via drinking water can disrupt the immune response in vaccinated mice by modulating cytokines and chemokines involved in their immune response to infectious disease. 相似文献
84.
Dandan Geng Lin Kang Yuhong Su Jianxin JiaJun Ma Sha LiJuan Du Huixian Cui 《Neurochemistry international》2013
Alzheimer’s disease (AD) is a neurodegenerative disorder characterized pathologically by the abnormal deposition of extracellular amyloid-β (Aβ) oligomers. However, the nature and precise mechanism of the toxicity of Aβ oligomers are not clearly understood. Aβ oligomers have been previously shown to cause a major loss of EphB2, a member of the EphB family of receptor tyrosine kinases. To determine the effect of EphB2 on Aβ oligomer-induced neurotoxicity and the underlying molecular mechanisms, we examined the EphB2 gene in cultured hippocampal neurons. Using a cellular model of AD, Aβ1–42 oligomers were confirmed to induce neurotoxicity in a time-dependent manner and result in a major decrease of EphB2. EphB2 overexpression could prevent the neurotoxicity of hippocampal neurons from exposure to Aβ1–42 oligomers for 1 h. Further analysis revealed that EphB2 overexpression increased synaptic NR1 and NR2B expression in Aβ1–42 oligomer-treated neurons. Moreover, EphB2 overexpression prevented Aβ1–42 oligomer-induced downregulation of dephosphorylated p38 MAPK and phosphorylated CREB. Together, these results suggest that EphB2 is a factor which protects hippocampal neurons against the toxicity of Aβ1–42 oligomers, and we infer that the protection of EphB2 is achieved by increasing the synaptic NMDA receptor level and downstream p38 MAPK and CREB signaling in hippocampal neurons. This study provides new molecular insights into the neuroprotective effect of EphB2 and highlights its potential therapeutic role in the management of AD. 相似文献
86.
Joon Ha Park Choong Hyun Lee In Hye Kim Ji Hyeon Ahn Jeong-Hwi Cho Bing Chun Yan Jae-Chul Lee Tae Hun Lee Jeong Yeol Seo Jun Hwi Cho Moo-Ho Won Il-Jun Kang 《Neurochemical research》2013,38(12):2640-2649
Glucose is a main energy source for normal brain functions. Glucokinase (GK) plays an important role in glucose metabolism as a glucose sensor, and GK activity is modulated by glucokinase regulatory protein (GKRP). In this study, we examined the changes of GK and GKRP immunoreactivities in the gerbil hippocampus after 5 min of transient global cerebral ischemia. In the sham-operated-group, GK and GKRP immunoreactivities were easily detected in the pyramidal neurons of the stratum pyramidale of the hippocampus. GK and GKRP immunoreactivities in the pyramidal neurons were distinctively decreased in the hippocampal CA1 region (CA), not CA2/3, 3 days after ischemia–reperfusion (I–R). Five days after I–R, GK and GKRP immunoreactivities were hardly detected in the CA1, not CA2/3, pyramidal neurons; however, at this point in time, GK and GKRP immunoreactivities were newly expressed in astrocytes, not microglia, in the ischemic CA1. In brief, GK and GKRP immunoreactivities are changed in pyramidal neurons and newly expressed in astrocytes in the ischemic CA1 after transient cerebral ischemia. These indicate that changes of GK and GKRP expression may be related to the ischemia-induced neuronal damage/death. 相似文献
87.
Effect of GABA Receptor Agonists or Antagonists Injected Spinally on the Blood Glucose Level in Mice
Yun-Beom Sim Soo-Hyun Park Yu-Jung Kang Sung-Su Kim Chea-Ha Kim Su-Jin Kim Jun-Sub Jung Ohk-Hyun Ryu Moon-Gi Choi Hong-Won Suh 《Neurochemical research》2013,38(5):1055-1062
The possible roles of gamma-amino butyric acid (GABA) receptors located in the spinal cord for the regulation of the blood glucose level were studied in ICR mice. We found in the present study that intrathecal (i.t.) injection with baclofen (a GABAB receptor agonist; 1–10 μg/5 μl) or bicuculline (a GABAA receptor antagonist; 1–10 μg/5 μl) caused an elevation of the blood glucose level in a dose-dependent manner. The hyperglycemic effect induced by baclofen was more pronounced than that induced by bicuculline. However, muscimol (a GABAA receptor agonist; 1–5 μg/5 μl) or phaclofen (a GABAB receptor antagonist; 5–10 μg/5 μl) administered i.t. did not affect the blood glucose level. Baclofen–induced elevation of the blood glucose was dose-dependently attenuated by phaclofen. Furthermore, i.t. pretreatment with pertussis toxin (PTX; 0.05 or 0.1 μg/5 μl) for 6 days dose-dependently reduced the hyperglycemic effect induced by baclofen. Our results suggest that GABAB receptors located in the spinal cord play important roles for the elevation of the blood glucose level. Spinally located PTX-sensitive G-proteins appear to be involved in hyperglycemic effect induced by baclofen. Furthermore, inactivation of GABAA receptors located in the spinal cord appears to be responsible for tonic up-regulation of the blood glucose level. 相似文献
88.
Lihua Kang Guowei Zhang Yaohua Yan Kaifu Ke Xinmin Wu Yilu Gao Jing Li Lin Zhu Qiyun Wu Zhengming Zhou 《Neurochemical research》2013,38(2):311-320
Heat shock protein A12B (HSPA12B) is the newest member of a recently defined subfamily of proteins distantly related to the 70-kDa family of heat shock proteins (HSP70) family. HSP70s play a crucial role in protecting cells, tissues, organs and animals from various noxious conditions. Here we studied the dynamic expression changes and localization of HSPA12B after middle cerebral artery occlusion (MCAO) with reperfusion induced ischemic insult processes in adult rats. Apoptosis, as indicated by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining, was also increased in the peri-ischemic cortex compared to non-ischemic hemisphere. The expression of HSPA12B was strongly induced in the ischemic hemisphere of MCAO reperfusion rats in vivo. In vitro studies indicated that the up-regulation of HSPA12B may be involved in oxygen-glucose deprivation-induced PC12 cell death. And knockdown of HSPA12B in cultured differentiated PC12 cells by siRNA showed that HSPA12B inhibited the expression of active caspase-3. Collectively, these results suggested that HSPA12B may be required for protecting neurons from ischemic insults. 相似文献
89.
Aerobic plate counts (APC), coliforms, Bacillus cereus, Escherichia coli and eight foodborne pathogens were tested in 1008 cheap and junk foods, including candies, dried cakes, chewing gum, chocolate, dried and seasoned seafood, ice cream, and sugary foods. APCs were positive for 342 samples (33·9%), and the majority of the counts were 2–3 log CFU g?1 or ml?1 (average: 1·10 log CFU g?1 or ml?1). Most samples (97·3%) contained no coliforms (average: 0·07 log CFU g?1 or ml?1). Bacillus cereus was detected in 68 samples (average: 0·14 log CFU g?1 or ml?1). Escherichia coli and Listeria monocytogenes were detected in 6 and 1 samples, respectively, whereas other foodborne pathogens were not isolated. The highest bacterial counts were associated with dried and seasoned seafood products and dried cakes, suggesting that appropriate regulations of these food types should be considered. Cheap and junk foods were produced mainly in developing countries, but there were no significant differences in the bacterial counts among different countries of origin. The presence of foodborne pathogens may pose a risk for children. These results suggest that there is cause for deeper concern about the safety of these foods and that effective countermeasures should be established to improve their microbiological safety.
Significance and Impact of the Study
Food safety is especially important for children, but only limited information is available about the microbiological quality of cheap and junk foods that are consumed frequently by primary schoolchildren (e.g. dried cakes, candies and chocolates). The present study investigated the microbial quality of cheap and junk foods, and our results indicate that these foods are a potential health risk for children, therefore, deeper concern about the safety of these foods and effective countermeasures should be established to improve their microbiological safety. The present study may contribute to the development of an appropriate child food safety management system. 相似文献90.