全文获取类型
收费全文 | 1477篇 |
免费 | 96篇 |
国内免费 | 2篇 |
专业分类
1575篇 |
出版年
2023年 | 6篇 |
2022年 | 30篇 |
2021年 | 42篇 |
2020年 | 15篇 |
2019年 | 24篇 |
2018年 | 47篇 |
2017年 | 30篇 |
2016年 | 52篇 |
2015年 | 70篇 |
2014年 | 81篇 |
2013年 | 107篇 |
2012年 | 106篇 |
2011年 | 90篇 |
2010年 | 69篇 |
2009年 | 50篇 |
2008年 | 69篇 |
2007年 | 66篇 |
2006年 | 83篇 |
2005年 | 59篇 |
2004年 | 51篇 |
2003年 | 40篇 |
2002年 | 29篇 |
2001年 | 28篇 |
2000年 | 26篇 |
1999年 | 23篇 |
1998年 | 13篇 |
1997年 | 7篇 |
1996年 | 18篇 |
1995年 | 7篇 |
1994年 | 8篇 |
1993年 | 10篇 |
1992年 | 27篇 |
1991年 | 22篇 |
1990年 | 20篇 |
1989年 | 17篇 |
1988年 | 19篇 |
1987年 | 16篇 |
1986年 | 13篇 |
1985年 | 12篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1981年 | 4篇 |
1979年 | 10篇 |
1978年 | 3篇 |
1976年 | 6篇 |
1974年 | 5篇 |
1973年 | 4篇 |
1971年 | 4篇 |
1970年 | 6篇 |
1969年 | 5篇 |
排序方式: 共有1575条查询结果,搜索用时 15 毫秒
941.
Takeshita F Tanaka T Matsuda T Tozuka M Kobiyama K Saha S Matsui K Ishii KJ Coban C Akira S Ishii N Suzuki K Klinman DM Okuda K Sasaki S 《Journal of virology》2006,80(13):6218-6224
Toll-like receptors (TLRs) recognize microbial components and trigger the signaling cascade that activates the innate and adaptive immunity. TLR adaptor molecules play a central role in this cascade; thus, we hypothesized that overexpression of TLR adaptor molecules could mimic infection without any microbial components. Dual-promoter plasmids that carry an antigen and a TLR adaptor molecule such as the Toll-interleukin-1 receptor domain-containing adaptor-inducing beta interferon (TRIF) or myeloid differentiation factor 88 (MyD88) were constructed and administered to mice to determine if these molecules can act as an adjuvant. A DNA vaccine incorporated with the MyD88 genetic adjuvant enhanced antigen-specific humoral immune responses, whereas that with the TRIF genetic adjuvant enhanced cellular immune responses. Incorporating the TRIF genetic adjuvant in a DNA vaccine targeting the influenza HA antigen or the tumor-associated antigen E7 conferred superior protection. These results indicate that TLR adaptor molecules can bridge innate and adaptive immunity and potentiate the effects of DNA vaccines against virus infection and tumors. 相似文献
942.
Cytosolic triacylglycerol biosynthetic pathway in oilseeds. Molecular cloning and expression of peanut cytosolic diacylglycerol acyltransferase 总被引:4,自引:0,他引:4 下载免费PDF全文
Triacylglycerols (TAGs) are the most important storage form of energy for eukaryotic cells. TAG biosynthetic activity was identified in the cytosolic fraction of developing peanut (Arachis hypogaea) cotyledons. This activity was NaF insensitive and acyl-coenzyme A (CoA) dependent. Acyl-CoA:diacylglycerol acyltransferase (DGAT) catalyzes the final step in TAG biosynthesis that acylates diacylglycerol to TAG. Soluble DGAT was identified from immature peanuts and purified by conventional column chromatographic procedures. The enzyme has a molecular mass of 41 +/- 1.0 kD. Based on the partial peptide sequence, a degenerate probe was used to obtain the full-length cDNA. The isolated gene shared less than 10% identity with the previously identified DGAT1 and 2 families, but has 13% identity with the bacterial bifunctional wax ester/DGAT. To differentiate the unrelated families, we designate the peanut gene as AhDGAT. Expression of peanut cDNA in Escherichia coli resulted in the formation of labeled TAG and wax ester from [14C]acetate. The recombinant E. coli showed high levels of DGAT activity but no wax ester synthase activity. TAGs were localized in transformed cells with Nile blue A and oil red O staining. The recombinant and native DGAT was specific for 1,2-diacylglycerol and did not utilize hexadecanol, glycerol-3-phosphate, monoacylglycerol, lysophosphatidic acid, and lysophosphatidylcholine. Oleoyl-CoA was the preferred acyl donor as compared to palmitoyl- and stearoyl-CoAs. These data suggest that the cytosol is one of the sites for TAG biosynthesis in oilseeds. The identified pathway may present opportunities of bioengineering oil-yielding plants for increased oil production. 相似文献
943.
Pluripotency is a unique property of stem cells that allows them to differentiate into all types of adult cells or maintain the self-renewal property. PluriPred predicts whether a protein is involved in pluripotency from primary protein sequence using manually curated pluripotent proteins as training datasets. Machine learning techniques (MLTs) such as Support Vector Machine (SVM), Naïve Base (NB), Random Forest (RF), and sequence alignment technique BLAST were used in our study. The combination of SVM and PSI-BLAST was our proposed best model, which obtained a sensitivity of 77.40%, specificity of 79.72%, accuracy of 79.2%, and area under the ROC curve was 0.82 using 5-fold cross-validation. Furthermore, PluriPred gives the confidence of the prediction from training dataset’s SVM score distribution and p-value from BLAST. We validated our proposed model with the other existing high-throughput studies using blind/independent datasets. Using PluriPred, 233 novel core and 323 novel extended core pluripotent proteins from mouse proteome, and 167 novel core and 385 extended core pluripotent proteins from human proteome, were predicted with high confidence. The Web application of PluriPred is available from bicresources.jcbose.ac.in/ssaha4/pluripred/. Many pluripotent genes/proteins take part in protein-protein networks associated with stem cell, cancer, and developmental biology, and we believe that PluriPred will help in these research. 相似文献
944.
A liquid culture protocol was developed to regenerate shoots from cotyledons of germinating seeds of jute (Corchorus capsularis L.). Reproducibility of the protocol was tested in three genotypes of jute. Highest bud differentiation rates into normal
shoots (via shoot-forming explants) were obtained on modified Murashige and Skoog's liquid medium containing 2.7 μM α-naphthaleneacetic acid and 4.4 μM benzylaminopurine. Regenerated shoots were excised, and the best root formation could be induced in medium with 2.5 μM indole-3-butyric acid and 1.5% sucrose. Bud primordia were formed directly on the cut surface of the cotyledons. Scanning
electron micrographs and histological studies confirmed the organogenic nature of the regenerated shoots. The physical condition
of the culture medium and the age of the explants played crucial roles in the induction of shoot development using shoots;
2-day-old explants being optimal. Approximately 70% of the shoots were successfully established in soil after hardening.
Received: 20 October 1997 / Revision received: 4 October 1998 / Accepted: 27 October 1998 相似文献
945.
Enhanced Histone Acetylation in the Infralimbic Prefrontal Cortex is Associated with Fear Extinction
Sarfraj Ahmad Siddiqui Sanjay Singh Vandana Ranjan Rajesh Ugale Sudipta Saha Anand Prakash 《Cellular and molecular neurobiology》2017,37(7):1287-1301
The molecular processes that establish fear memory are complex and involve a combination of genetic and epigenetic influences. Dysregulation of these processes can manifest in humans as a range of fear-related anxiety disorders like post-traumatic stress disorders (PTSD). In the present study, immunohistochemistry for acetyl H3, H4, c-fos, CBP (CREB-binding protein) in the infralimbic prefrontal cortex (IL-PFC) and prelimbic prefrontal cortex (PL-PFC) of mPFC (medial prefrontal cortex) and basal amygdala (BA), lateral amygdala (LA), centrolateral amygdala (CeL), centromedial amygdala (CeM) of the amygdala was performed to link region-specific histone acetylation to fear and extinction learning. It was found that the PL-PFC and IL-PFC along with the sub-regions of the amygdala responded differentially to the fear learning and extinction. Following fear learning, c-fos and CBP expression and acetylation of H3 and H4 increased in the BA, LA, CeM, and CeL and the PL-PFC but not in the IL-PFC as compared to the naive control. Similarly, following extinction learning, c-fos and CBP expression increased in BA, LA, CeL, and IL-PFC but not in PL-PFC and CeM as compared to the naive control and conditioned group. However, the acetylation of H3 increased in both IL and PL as opposed to H4 which increased only in the IL-PFC following extinction learning. Overall, region-specific activation in amygdala and PFC following fear and extinction learning as evident by the c-fos activation paralleled the H3/H4 acetylation in these regions. These results suggest that the differential histone acetylation in the PFC and amygdala subnuclei following fear learning and extinction may be associated with the region-specific changes in the neuronal activation pattern resulting in more fear/less fear. 相似文献
946.
Kraegen EW Saha AK Preston E Wilks D Hoy AJ Cooney GJ Ruderman NB 《American journal of physiology. Endocrinology and metabolism》2006,290(3):E471-E479
Glucose infusion in rats for 1-4 days results in insulin resistance and increased triglyceride, whole tissue long-chain fatty acyl-CoA (LCA-CoA), and malonyl-CoA content in red skeletal muscle. Despite this, the relation between these alterations and the onset of insulin resistance has not been defined. We aimed to 1) identify whether the changes in these lipids and of diacylglycerol (DAG) precede or accompany the onset of insulin resistance in glucose-infused rats, 2) determine whether the insulin resistance is associated with alterations in AMP-activated protein kinase (AMPK), and 3) assess whether similar changes occur in liver and in muscle. Hyperglycemia (17-18 mM) was maintained by intravenous glucose infusion in rats for 3 or 5 h; then euglycemia was restored and a 2-h hyperinsulinemic clamp was performed. Significant (P < 0.01) muscle and liver insulin resistance first appeared in red quadriceps and liver of the glucose-infused group at 5 h and was associated with a twofold increase in DAG and malonyl-CoA content and a 50% decrease in AMPK and acetyl-CoA carboxylase (ACC) phosphorylation and AMPK activity. White quadriceps showed qualitatively similar changes but without decreases in AMPK or ACC phosphorylation. Triglyceride mass was increased at 5 h only in liver, and whole tissue LCA-CoA content was not increased in liver or either muscle type. We conclude that the onset of insulin resistance induced by glucose oversupply correlates temporally with increases in malonyl-CoA and DAG content in all three tissues and with reduced AMPK phosphorylation and activity in red muscle and liver. In contrast, it was not associated with increased whole tissue LCA-CoA content in any tissue or triglyceride in muscle, although both are observed at later times. 相似文献
947.
The present study has been carried out to describe the cell morphology of the developing male gametes in a fish ectoparasite, Argulus bengalensis Ramakrishna, 1951. With respect to cell volume and nucleoplasmic index, spermatogonia are the smallest and primary spermatocytes are the largest in this lineage. The spermatogonia and the differentiating spermatogenic cells are in separate niches and confined to different enclaves within each testicular lobe. Spermiogenesis occurs within the inner enclave of each testicular lobe. During this process the nucleus becomes streamlined; an acrosome is formed, axoneme is originated, and residual cytoplasm is discarded through the flagellum. The sperm cell morphology displays a general pattern comprising head, mid-piece, and a full length flagellum. In the axoneme 9 + 2 arrangement of the microtubule is conserved. In addition to the axoneme, some more singlet microtubules are found surrounding a fiber sheath and around one of the mitochondria adjacent to the axoneme. This arrangement indicates a close phylogenetic relationship with pentastomida. In the present study, structure and formation of spermatophore are described in this branchiuran parasite. 相似文献
948.
Ashish Narayan Masurekar Catriona A. Parker Milensu Shanyinde Anthony V. Moorman Jeremy P. Hancock Rosemary Sutton Philip J. Ancliff Mary Morgan Nicholas J. Goulden Chris Fraser Peter M. Hoogerbrugge Tamas Revesz Philip J. Darbyshire Shekhar Krishnan Sharon B. Love Vaskar Saha 《PloS one》2014,9(10)
The outcomes of Central Nervous System (CNS) relapses in children with acute lymphoblastic leukaemia (ALL) treated in the ALL R3 trial, between January 2003 and March 2011 were analysed. Patients were risk stratified, to receive a matched donor allogeneic transplant or fractionated cranial irradiation with continued treatment for two years. A randomisation of Idarubicin with Mitoxantrone closed in December 2007 in favour of Mitoxantrone. The estimated 3-year progression free survival for combined and isolated CNS disease were 40.6% (25·1, 55·6) and 38.0% (26.2, 49.7) respectively. Univariate analysis showed a significantly better survival for age <10 years, progenitor-B cell disease, good-risk cytogenetics and those receiving Mitoxantrone. Adjusting for these variables (age, time to relapse, cytogenetics, treatment drug and gender) a multivariate analysis, showed a poorer outcome for those with combined CNS relapse (HR 2·64, 95% CI 1·32, 5·31, p = 0·006 for OS). ALL R3 showed an improvement in outcome for CNS relapses treated with Mitoxantrone compared to Idarubicin; a potential benefit for matched donor transplant for those with very early and early isolated-CNS relapses.
Trial Registration
Controlled-Trials.com ISRCTN45724312 相似文献949.
Required to supply nutrients and oxygen to the growing embryo, the vascular system is the first functional organ system to develop during vertebrate embryogenesis. Although there has been substantial progress in identifying the genetic cascade regulating vascular development, the initial stages of vasculogenesis, namely, the origin of vascular endothelial cells within the early embryo, remain unclear. To address this issue we constructed a fate map for specific vascular structures, including the aortic arches, endocardium, dorsal aorta, cardinal veins, and lateral abdominal veins, as well as for the red blood cells at the 16-cell stage and the 32-cell stage of Xenopus laevis. Using genetic markers to identify these cell types, our results suggest that vascular endothelial cells can arise from virtually every blastomere of the 16-cell-stage and the 32-cell-stage embryo, with different blastomeres preferentially, though not exclusively, giving rise to specific vascular structures. Similarly, but more surprisingly, every blastomere in the 16-cell-stage embryo and all but those in the most animal tier of the 32-cell-stage embryo serve as progenitors for red blood cells. Taken together, our results suggest that during normal development, both dorsal and ventral blastomeres contribute significantly to the vascular endothelial and red blood cell lineages. 相似文献
950.
An additive-dominance model to determine chromosomal effects in chromosome substitution lines and other gemplasms 总被引:1,自引:0,他引:1
Wu J Jenkins JN McCarty JC Saha S Stelly DM 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2006,112(3):391-399
When using chromosome substitution (CS) lines in a crop breeding improvement program, one needs to separate the effects of
the substituted chromosome from the remaining chromosomes. This cannot be done with the traditional additive-dominance (AD)
model where CS lines, recurrent parent, and their hybrids are used. In this study, we develop a new genetic model and software,
called a modified AD model with genotype × environment interactions, which can predict additive and dominance genetic effects
attributed to a substituted alien chromosome in a CS line as well as the overall genetic effects of the non-substituted chromosomes.
In addition, this model will predict the additive and dominance effects of the same chromosome of interest (i.e. chromosome
25 of cotton in this study) in an inbred line, as well as the effects of the remaining chromosomes in the inbred line. The
model requires a CS line, its recurrent parent and their F1 and/or F2 hybrids between the substitution lines and several inbred lines. Monte Carlo simulation results showed that genetic variance
components were estimated with no or slight bias when we considered this modified AD model as random. The correlation coefficient
between predicted effects and true effects due to the chromosomes of interest varied from zero to greater than 0.90 and it
was positively relative to the difference between the CS line and the recurrent line. To illustrate the use of this new genetic
model, an upland cotton, Gossypium hirsusum L, CS line (CS-B25), TM-1 (the recurrent parent), five elite cultivars, and the F2 hybrids from test-crossing these two lines with the five elite cultivars were grown in two environments in Mississippi. Agronomic
and fiber data were collected and analyzed. The results showed that the CS line, CS-B25, which has chromosome 25 from line
3 to 79, Gossypium barbadense substituted into TM-1, had positive genetic associations with several fiber traits. We also determined that Chromosome 25
from FiberMax 966 had significantly positive associations with fiber length and strength; whereas, chromosome 25 from TM-1
and SureGrow 747 had detectable negative genetic effects on fiber strength. The new model will be useful to determine effects
of the chromosomes of interest in various inbred lines in any diploid or amphidiploid crop for which CS lines are available. 相似文献