全文获取类型
收费全文 | 113996篇 |
免费 | 13617篇 |
国内免费 | 626篇 |
出版年
2021年 | 812篇 |
2018年 | 1182篇 |
2017年 | 1076篇 |
2016年 | 1428篇 |
2015年 | 1827篇 |
2014年 | 2284篇 |
2013年 | 2774篇 |
2012年 | 3250篇 |
2011年 | 3147篇 |
2010年 | 2080篇 |
2009年 | 2060篇 |
2008年 | 2598篇 |
2007年 | 2535篇 |
2006年 | 2485篇 |
2005年 | 2257篇 |
2004年 | 2170篇 |
2003年 | 2218篇 |
2002年 | 2172篇 |
2001年 | 9695篇 |
2000年 | 9569篇 |
1999年 | 7219篇 |
1998年 | 1600篇 |
1997年 | 1777篇 |
1996年 | 1570篇 |
1995年 | 1447篇 |
1994年 | 1334篇 |
1993年 | 1269篇 |
1992年 | 4814篇 |
1991年 | 4541篇 |
1990年 | 4005篇 |
1989年 | 4023篇 |
1988年 | 3615篇 |
1987年 | 3091篇 |
1986年 | 2778篇 |
1985年 | 2677篇 |
1984年 | 1977篇 |
1983年 | 1730篇 |
1982年 | 1230篇 |
1981年 | 983篇 |
1980年 | 911篇 |
1979年 | 1760篇 |
1978年 | 1360篇 |
1977年 | 1198篇 |
1976年 | 1027篇 |
1975年 | 1150篇 |
1974年 | 1163篇 |
1973年 | 1160篇 |
1972年 | 1031篇 |
1971年 | 956篇 |
1970年 | 823篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
The septins FaCdc3 and FaCdc12 are required for cytokinesis and affect asexual and sexual development,lipid metabolism and virulence in Fusarium asiaticum 下载免费PDF全文
Yu Zhang Tao Gao Wenyong Shao Zhitian Zheng Mingguo Zhou Changjun Chen 《Molecular Plant Pathology》2017,18(9):1282-1294
Septins are a highly conserved family of GTP‐binding proteins that contribute to many cellular and metabolic functions, including cell polarity, cytokinesis, cell morphogenesis and pathogenesis. In this study, we characterized the septins FaCdc3 and FaCdc12 in the filamentous fungus Fusarium asiaticum. The functions of FaCdc3 and FaCdc12 were evaluated by constructing deletion mutants of FaCdc3 and FaCdc12, designated ΔFaCdc3‐5 and ΔFaCdc12‐71, respectively. The deletion mutants exhibited a reduced rate of mycelial growth, increased aerial hyphae formation, irregularly shaped hyphae, reduced conidiation and a lack of sexual reproduction in wheat kernels. Histochemical analysis revealed that the conidia and hyphae of ΔFaCdc3‐5 and ΔFaCdc12‐71 formed large lipid droplets (LDs). ΔFaCdc3‐5 and ΔFaCdc12‐71 also exhibited increased resistance to agents that induce osmotic stress and damage the cell membrane and cell wall. In addition, the hyphae and conidia of the two mutants formed fewer septa than those of the wild‐type and exhibited aberrant nuclear distribution. Pathogenicity assays showed that ΔFaCdc3‐5 and ΔFaCdc12‐71 exhibited reduced virulence on wheat spikelets, which was indirectly correlated with a reduced level of deoxynivalenol accumulation. All of these defects were restored by genetic complementation of the two mutants with the parental FaCdc3 and FaCdc12. These results indicate that FaCdc3 and FaCdc12 play a critical role in various cellular processes in F. asiaticum. 相似文献
2.
In order to identify the lower limb movements accurately and quickly, a recognition method based on extreme learning machine (ELM) is proposed. The recognizing target set is constructed by decomposing the daily actions into different segments. To get the recognition accuracy of seven movements based on the surface electromyography, the recognition feature vector space is established by integrating short-time statistical characteristics under time domain, and locally linear embedding algorithm is used to reduce the computational complexity and improve robustness of algorithm. Compared with BP, the overall recognition accuracy for each subject in the best dimension with ELM is above 95%. 相似文献
3.
In the present work we studied the effect of antioxidants of the SkQ1 family (10-(6′-plastoquinonyl)decyltriphenylphosphonium) on the oxidative hemolysis of erythrocytes induced by a lipophilic free radical initiator 2,2′-azobis(2,4-dimethylvaleronitrile) (AMVN) and a water-soluble free radical initiator 2,2′-azobis(2-methylpropionamidine) dihydrochloride (AAPH). SkQ1 was found to protect erythrocytes from hemolysis, 2 μM being the optimal concentration. Both the oxidized and reduced SkQ1 forms exhibited protective properties. Both forms of SkQ1 also inhibited lipid peroxidation in erythrocytes induced by the lipophilic free radical initiator AMVN as detected by accumulation of malondialdehyde. However, in the case of induction of erythrocyte oxidation by AAPH, the accumulation of malondialdehyde was not inhibited by SkQ1. In the case of AAPH-induced hemolysis, the rhodamine-containing analog SkQR1 exerted a comparable protective effect at the concentration of 0.2 μM. At higher SkQ1 and SkQR1 concentrations, the protective effect was smaller, which was attributed to the ability of these compounds to facilitate hemolysis in the absence of oxidative stress. We found that plastoquinone in the oxidized form of SkQ1 could be reduced by erythrocytes, which apparently accounted for its protective action. Thus, the protective effect of SkQ in erythrocytes, which lack mitochondria, proceeded at concentrations that are two to three orders of magnitude higher than those that were active in isolated mitochondria. 相似文献
4.
5.
6.
Enzymatically active human testis angiotensin-converting enzyme (ACE) was expressed in Chinese hamster ovary (CHO) cells stably transfected with each of three vectors: p omega-ACE contains a full-length testis ACE cDNA under the control of a retroviral promoter; and pLEN-ACEVII and pLEN-ACE6/5, in which full-length and membrane anchor-minus testis ACE cDNAs, respectively, are under the control of the human metallothionein IIA promoter and SV40 enhancer. In every case, active recombinant human testis ACE (hTACE) was secreted in a soluble form into the culture media, up to 2.4 mg/liter in the media of metal-induced, high-producing clones transfected with one of the pLEN vectors. In addition, membrane-bound recombinant enzyme was recovered from detergent extracts of cell pellets of CHO cells transfected with either p omega-ACE or pLEN-ACE-VII. Recombinant converting enzyme was purified to homogeneity by single-step affinity chromatography of conditioned media and detergent-extracted cell pellets in 85 and 70% overall yield, respectively. Purified hTACE from all sources comigrated with the native testis isozyme on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with M(r) approximately 100 kDa. The native and recombinant proteins cross-reacted equally with anti-human kidney ACE antiserum on Western blotting. The catalytic activity of recombinant angiotensin-converting enzyme, in terms of angiotensin I and 2-furanacryloyl-Phe-Gly-Gly hydrolysis, chloride activation, and lisinopril inhibition, was essentially identical to that of the native enzyme. The facile recovery in high yield of fully active hTACE from the media of stably transfected CHO cells provides a suitable system for investigating structure-function relationships in this enzyme. 相似文献
7.
D R Hickey K Jayaraman C T Goodhue J Shah S A Fingar J M Clements Y Hosokawa S Tsunasawa F Sherman 《Gene》1991,105(1):73-81
Genes encoding tuna, pigeon, and horse cytochromes c were constructed with synthetic oligodeoxyribonucleotides having preferred codons and portions of the iso-1-cytochrome c-encoding gene from the yeast Saccharomyces cerevisiae. The genes were ligated into an expression vector, which contains the normal 5'- and 3'-untranslated regions of the yeast iso-1-cytochrome c gene, and were integrated in single copy into the chromosome. Yeast strains were also constructed with multiple integrated copies of the pigeon gene. The heterologous and normal mRNA levels of the single-copy strains were equivalent. Although the N-terminal methionines were completely cleaved in the heterospecific proteins, the levels of trimethylation of Lys72 and acetylation of N-terminal glycines ranged from 39-78% and 10-70%, respectively. Horse cytochrome c was produced at a nearly normal level, whereas the pigeon and tuna cytochromes c were produced at approx. 40% of the normal levels. The levels of the cytochromes c and growth of the mutant yeast strains indicated that the heterospecific cytochromes c had approx. 50% specific activity in vivo. 相似文献
8.
9.
A two-stage fermentation process was established for the production of pigment-free pullulan by the yeast-like fungus Aureobasidium pullulans (ATCC 42023). In the first stage, starting at pH 4.5 with soy bean oil as the carbon source and glutamate as the nitrogen source, a cell mass of about 15 g l–1 dry cell weight was obtained, the population being restricted mainly to the yeast form of the microorganism (yeast form more than 90% of total cells) and the formation of pigment in the culture being prevented. Small amounts of pullulan (less than 2 g l–1) are produced at this phase, and the viscosity remained low throughout the entire growth stage. When the oil and glutamate source were nearly exhausted (below 5% of initial amounts), the cells were shifted to a production stage with sucrose as the carbon source with continued nitrogen depletion. Production of pullulan started immediately with no lag period. During 50 h of the production phase more than 35 g l–1 of pullulan was produced (productivity approx. 0.7 g l–1), resulting in a large increase in the viscosity of the broth. The production yield of pollulan on the sugar was about 0.6 g g–1. Morphogenesis from the yeast form of the microorganism to chlamydospores was still restrained and no pigment was formed in the culture during the production stage. A pigment-free polysaccharide, with a molecular mass in the range of 600–750 kDa, was recovered from the supernatant of the broth after solvent precipitation. 相似文献
10.