全文获取类型
收费全文 | 3016篇 |
免费 | 221篇 |
国内免费 | 377篇 |
出版年
2024年 | 6篇 |
2023年 | 54篇 |
2022年 | 83篇 |
2021年 | 158篇 |
2020年 | 128篇 |
2019年 | 144篇 |
2018年 | 128篇 |
2017年 | 110篇 |
2016年 | 149篇 |
2015年 | 207篇 |
2014年 | 238篇 |
2013年 | 286篇 |
2012年 | 290篇 |
2011年 | 255篇 |
2010年 | 146篇 |
2009年 | 152篇 |
2008年 | 171篇 |
2007年 | 125篇 |
2006年 | 114篇 |
2005年 | 122篇 |
2004年 | 82篇 |
2003年 | 81篇 |
2002年 | 57篇 |
2001年 | 34篇 |
2000年 | 41篇 |
1999年 | 45篇 |
1998年 | 34篇 |
1997年 | 37篇 |
1996年 | 17篇 |
1995年 | 23篇 |
1994年 | 21篇 |
1993年 | 17篇 |
1992年 | 18篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1989年 | 8篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1979年 | 2篇 |
1976年 | 1篇 |
排序方式: 共有3614条查询结果,搜索用时 15 毫秒
81.
A model of coupled neural masses can generate seizure-like events and dynamics similar to those observed during interictal to ictal transitions and thus can be used for theoretical study of the control of epileptic seizures. In an effort to understand the mechanisms underlying epileptic seizures and how to avoid them, we added a control input to this model. Epileptic seizures are always accompanied by hypersynchronous firing of neurons, so research on synchronization among cortical areas is significant for seizure control. In this study, principal component analysis (PCA) was used to identify synchronization clusters composed of several neural masses. A method for calculating the synchronization cluster strength and participation rate is presented. The synchronization cluster strength can be used to identify synchronization clusters and the participation rate can be employed to identify neural masses that participate in the clusters. Each synchronization cluster is controlled as a whole using a proportional-integral-derivative (PID) controller. We illustrate these points using coupled neural mass models of synchronization to show their responses to increased (between node) coupling with and without control. Experiment results indicated that PID control can effectively regulate synchronization between neural masses and has the potential for seizure prevention. 相似文献
82.
Zhaojing Zheng Juan Geng Ru-en Yao Caihua Li Daming Ying Yongnian Shen Lei Ying Yongguo Yu Qihua Fu 《Gene》2013
Fanconi anemia is a rare genetic disease characterized by bone marrow failure, multiple congenital malformations, and an increased susceptibility to malignancy. At least 15 genes have been identified that are involved in the pathogenesis of Fanconi anemia. However, it is still a challenge to assign the complementation group and to characterize the molecular defects in patients with Fanconi anemia. In the current study, whole exome sequencing was used to identify the affected gene(s) in a boy with Fanconi anemia. A recurring, non-synonymous mutation was found (c.3971C>T, p.P1324L) as well as a novel frameshift mutation (c.989_995del, p.H330LfsX2) in FANCA gene. Our results indicate that whole exome sequencing may be useful in clinical settings for rapid identification of disease-causing mutations in rare genetic disorders such as Fanconi anemia. 相似文献
83.
Wang Xinhong Liu Weimin Wu Yue Liu Xiaojun Liang Xiao Wan Zhaofei Wang Nanping Yuan Zuyi 《Molecular and cellular biochemistry》2013,377(1-2):131-141
Glycodelin A (GdA) is a dimeric glycoprotein synthesized by the human endometrium under progesterone regulation. Based on the high sequence similarity with β-lactoglobulin, it is placed under the lipocalin superfamily. The protein is one of the local immunomodulators present at the feto-maternal interface which affects both the innate as well as the acquired arms of the immune system, thereby bringing about successful establishment and progression of pregnancy. Our previous studies revealed that the domain responsible for the immunosuppressive activity of glycodelin lies on its protein backbone and the glycans modulate the same. This study attempts to further delineate the apoptosis inducing region of GdA. Our results demonstrate that the stretch of amino acid sequence between Met24 to Leu105 is necessary and sufficient to inhibit proliferation of T cells and induce apoptosis in them. Further, within this region the key residues involved in harboring the activity were shown to be present between Asp52 and Ser65. 相似文献
84.
85.
86.
Molecular dynamics simulation is used to study the decomposition and stability of SII hydrogen and hydrogen/tetrahydrofuran (THF) hydrates at 150 K, 220 K and 100 bar. The modelling of the microscopic decomposition process of hydrogen hydrate indicates that the decomposition of hydrogen hydrate is led by the diffusive behaviour of H2 molecules. The hydrogen/THF hydrate presents higher stability, by comparing the distributions of the tetrahedral angle of H2O molecules, radial distribution functions of H2O molecules and mean square displacements or diffusion coefficients of H2O and H2 molecules in hydrogen hydrate with those in hydrogen/THF hydrate. It is also found that the resistance of the diffusion behaviour of H2O and H2 molecules can be enhanced by encaging THF molecules in the (51264) cavities. Additionally, the motion of THF molecules is restricted due to its high interaction energy barrier. Accordingly, THF, as a stabiliser, is helpful in increasing the stability of hydrogen hydrate. 相似文献
87.
Ji Luan Tianran Liu Weiqi Luo Wen Liu Minqi Peng Wenjia Li Xiaojun Dai Manzhong Liang Liangbi Chen 《Plant cell reports》2013,32(4):545-554
Key message
Thirteen rice CMS lines derived from different cytoplasms were classified into eight groups by PCR amplification on mtDNA. The orf79 gene, which causes Boro II CMS, possibly results in Dian1-CMS.Abstract
Thirteen rice cytoplasmic male sterile (CMS) lines derived from different cytoplasms are widely used for hybrid rice breeding. Based on 27 loci on mitochondrial DNA, including single nucleotide polymorphisms and segmental sequence variations between typical indica and japonica as well as high-polymorphism segmental sequence variations and single nucleotide polymorphisms among rice CMS lines, the 13 rice CMS lines were classified into eight groups: (I) wild-abortive CMS, Indonesian Shuitiangu CMS, K-CMS, Gang CMS, D-CMS and dwarf abortive CMS; (II) Maxie-CMS; (III) Honglian CMS; (IV) Boro II CMS; (V) Dian1-CMS; (VI) Liao-CMS; (VII) Lead CMS; and (VIII) Chinese wild rice CMS. According to their pollen abortion phenotypes, groups I and II (including 7 CMS lines) were classified as sporophytic CMS lines, the cytoplasmic genetic relationships among which were very close. They could have originated from similar, or even the same, cytoplasm donors. Groups III–VIII (including 6 CMS lines) were categorized as gametophytic CMS lines, the cytoplasms of which differed from one another, with some having relatively far genetic relationships. Dian1-CMS was found to harbor the orf79 gene, which causes Boro II CMS, whereas Liao-CMS had an orf79 structure that does not result in Lead CMS. Therefore, we speculated that orf79 is associated with Dian1-CMS but not with Liao-CMS. The atp6–orf79 structure related to sterility was also found to experience multiple evolutionary turnovers. All sporophytic CMS lines were indica-like. Except the Honglian CMS line, which was indica-like, all gametophytic CMS lines were japonica-like. 相似文献88.
The critical soil P levels for crop yield, soil fertility and environmental safety in different soil types 总被引:34,自引:0,他引:34
Zhaohai Bai Haigang Li Xueyun Yang Baoku Zhou Xiaojun Shi Boren Wang Dongchu Li Jianbo Shen Qing Chen Wei Qin Oene Oenema Fusuo Zhang 《Plant and Soil》2013,372(1-2):27-37
Background and aims
Sufficient soil phosphorus (P) is important for achieving optimal crop production, but excessive soil P levels may create a risk of P losses and associated eutrophication of surface waters. The aim of this study was to determine critical soil P levels for achieving optimal crop yields and minimal P losses in common soil types and dominant cropping systems in China.Methods
Four long-term experiment sites were selected in China. The critical level of soil Olsen-P for crop yield was determined using the linear-plateau model. The relationships between the soil total P, Olsen-P and CaCl2-P were evaluated using two-segment linear model to determine the soil P fertility rate and leaching change-point.Results
The critical levels of soil Olsen-P for optimal crop yield ranged from 10.9 mg kg?1 to 21.4 mg kg?1, above which crop yield response less to the increasing of soil Olsen-P. The P leaching change-points of Olsen-P ranged from 39.9 mg kg?1 to 90.2 mg kg?1, above which soil CaCl2-P greatly increasing with increasing soil Olsen-P. Similar change-point was found between soil total P and Olsen-P. Overall, the change-point ranged from 4.6 mg kg?1 to 71.8 mg kg?1 among all the four sites. These change-points were highly affected by crop specie, soil type, pH and soil organic matter content.Conclusions
The three response curves could be used to access the soil Olsen-P status for crop yield, soil P fertility rate and soil P leaching risk for a sustainable soil P management in field. 相似文献89.
Xun Huang Qiuming Pan Danni Sun Wei Chen Aijun Shen Min Huang Jian Ding Meiyu Geng 《The Journal of biological chemistry》2013,288(51):36418-36425
O-GlcNAcylation is a post-translational modification that regulates a broad range of nuclear and cytoplasmic proteins and is emerging as a key regulator of various biological processes. Previous studies have shown that increased levels of global O-GlcNAcylation and O-GlcNAc transferase (OGT) are linked to the incidence of metastasis in breast cancer patients, but the molecular basis behind this is not fully known. In this study, we have determined that the actin-binding protein cofilin is O-GlcNAcylated by OGT and mainly, if not completely, mediates OGT modulation of cell mobility. O-GlcNAcylation at Ser-108 of cofilin is required for its proper localization in invadopodia at the leading edge of breast cancer cells during three-dimensional cell invasion. Loss of O-GlcNAcylation of cofilin leads to destabilization of invadopodia and impairs cell invasion, although the actin-severing activity or lamellipodial localization is not affected. Our study provides insights into the mechanism of post-translational modification in fine-tuning the regulation of cofilin activity and suggests its important implications in cancer metastasis. 相似文献
90.
Jing Yang Chao Wang Chang Shu Li Liu Jianing Geng Songnian Hu Jie Feng 《Microbial ecology》2013,65(4):975-981
The ocean is a natural habitat for antibiotic-producing bacteria, and marine aquaculture introduces antibiotics into the ocean to treat infections and improve aquaculture production. Studies have shown that the ocean is an important reservoir of antibiotic resistance genes. However, there is a lack of understanding and knowledge about the clinical importance of the ocean resistome. We investigated the relationship between the ocean bacterial resistome and pathogenic resistome. We applied high-throughput sequencing and metagenomic analyses to explore the resistance genes in bacterial plasmids from marine sediments. Numerous putative resistance determinants were detected among the resistance genes in the sediment bacteria. We also found that several contigs shared high identity with transposons or plasmids from human pathogens, indicating that the sediment bacteria recently contributed or acquired resistance genes from pathogens. Marine sediment bacteria could play an important role in the global exchange of antibiotic resistance. 相似文献