全文获取类型
收费全文 | 3171篇 |
免费 | 274篇 |
国内免费 | 1篇 |
专业分类
3446篇 |
出版年
2022年 | 19篇 |
2021年 | 40篇 |
2020年 | 17篇 |
2019年 | 22篇 |
2018年 | 33篇 |
2017年 | 32篇 |
2016年 | 55篇 |
2015年 | 75篇 |
2014年 | 104篇 |
2013年 | 156篇 |
2012年 | 187篇 |
2011年 | 176篇 |
2010年 | 116篇 |
2009年 | 105篇 |
2008年 | 165篇 |
2007年 | 195篇 |
2006年 | 168篇 |
2005年 | 156篇 |
2004年 | 151篇 |
2003年 | 159篇 |
2002年 | 148篇 |
2001年 | 84篇 |
2000年 | 74篇 |
1999年 | 73篇 |
1998年 | 51篇 |
1997年 | 43篇 |
1996年 | 53篇 |
1995年 | 39篇 |
1994年 | 37篇 |
1993年 | 30篇 |
1992年 | 70篇 |
1991年 | 52篇 |
1990年 | 59篇 |
1989年 | 53篇 |
1988年 | 41篇 |
1987年 | 32篇 |
1986年 | 51篇 |
1985年 | 45篇 |
1984年 | 35篇 |
1983年 | 32篇 |
1982年 | 38篇 |
1981年 | 22篇 |
1980年 | 21篇 |
1979年 | 21篇 |
1978年 | 11篇 |
1977年 | 23篇 |
1974年 | 11篇 |
1973年 | 10篇 |
1972年 | 9篇 |
1968年 | 8篇 |
排序方式: 共有3446条查询结果,搜索用时 15 毫秒
991.
Usefulness of multiple chalk‐based food colorings for inducing better gene silencing by feeding RNA interference in planarians 下载免费PDF全文
Miki Hattori Mai Miyamoto Kazutaka Hosoda Yoshihiko Umesono 《Development, growth & differentiation》2018,60(1):76-81
Planarians have become widely recognized as one of the major animal models for regeneration studies in invertebrates. To induce RNA interference (RNAi) by feeding in planarians, the widely accepted protocol is one in which animals undergo two or three feedings of food containing double‐stranded RNA (dsRNA) plus visible food coloring (e.g., blood) for confirmation of feeding by individual animals. However, one possible problem is that incorporated food coloring is often retained within the gut for several days, which makes it difficult to confirm the success of each round of dsRNA feeding based on the difference of the color density within the gut before and after feeding. As a consequence, the difference of appetite levels among individuals undergoing dsRNA feeding leads to phenotypic variability among them due to insufficient knockdown. In our attempts to overcome this problem, we have developed a novel method for achieving robust confirmation of the success of dsRNA feeding in individuals fed multiple times by means of including a combination of three different colored chalks (pink, yellow and blue) as food coloring. Notably, we found that this method is superior to the conventional method for positively marking individuals that actively consumed the dsRNA‐containing food during four times of once‐daily feeding. Using these selected animals, we obtained stable and sufficiently strong RNAi‐induced phenotypes. We termed this improved multi‐colored chalk‐spiked method of feeding RNAi “Candi” and propose its benefits for gene function analysis in planarians. 相似文献
992.
Akira Isogai Naoyuki Fukuchi Miki Hayashi Hiroshi Kamada Hiroshi harada Akinori Suzuki 《Bioscience, biotechnology, and biochemistry》2013,77(12):3235-3237
A enzyme that catalyzed the specific formation of ascorbic acid-2-phosphate (AsA2P) from ascorbic acid (AsA) and adenosine-5′-triphosphate (ATP), was purified 3,200-fold to homogeneity from a cell extract of Pseudomonas azotocolligans. The purified enzyme appeared as a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and consisted of a single polypeptide with a molecular weight of about 30,000. Of phosphoryl donors tested, p-nitrophenylphosphate (p-NPP) and pyrophosphate (PPi) were as effective as ATP. Optimal pHs for the phosphorylating activity were around 4.0 and 5.5 when PPi and ATP were used as phosphoryl donors, respectively. The Km for AsA was 147 mm. The enzyme activity was inhibited by Cu2+, but not by sulfhydryl reagents.The enzyme simultaneously had phosphatase activity at weakly acidic or neutral pH and the Km for p-NPP in the phosphatase activity was 0.38 mm. The enzyme was tentatively named “ascorbic acid phosphorylating enzyme.” 相似文献
993.
Nukuzuma S Nakamichi K Kameoka M Sugiura S Nukuzuma C Miyoshi I Takegami T 《Microbiology and immunology》2010,54(12):758-762
The high incidence of progressive multifocal leukoencephalopathy (PML) in AIDS patients compared with many other immunosuppressive diseases suggests that HIV-1 infection is strictly related to the activation of JC virus (JCV) propagation. In this report, propagation of PML-type JCV in COS-7-derived cell lines stably expressing HIV-1 Tat (COS-tat cells) has been examined. In COS-tat cells, production of viral particles and replication of genomic DNA were markedly increased compared to COS-7 cells, as judged by HA and real-time PCR analyses. These results demonstrate that COS-tat cells provide a useful model system for studying HIV-1 Tat-mediated propagation of PML-type JCV. 相似文献
994.
Promoter polymorphism in fibroblast growth factor 1 gene increases risk of definite Alzheimer's disease 总被引:3,自引:0,他引:3
Yamagata H Chen Y Akatsu H Kamino K Ito J Yokoyama S Yamamoto T Kosaka K Miki T Kondo I 《Biochemical and biophysical research communications》2004,321(2):320-323
Fibroblast growth factor 1 (FGF1, also known as acidic FGF) protects selective neuronal populations against neurotoxic effects such as those in Alzheimer's disease (AD) and HIV encephalitis. The FGF1 gene is therefore a strong candidate gene for AD. Using the promoter polymorphism of the FGF1 gene, we examined the relationship between AD and the FGF1 and apolipoprotein E (APOE) genes in 100 Japanese autopsy-confirmed late-onset AD patients and 106 age-matched non-demented controls. The promoter polymorphism (-1385 A/G) was significantly associated with AD risk. The odds ratio for AD associated with the GG vs non-GG genotype was 2.02 (95% CI = 1.16-3.52), while that of s4 vs non-?4 in APOE4 gene was 5.19 (95% CI = 2.68-10.1). The odds ratio for APOEP4 and FGF1 GG carriers was 20.5 (95% CI = 6.88-60.9). The results showed that the FGF1 gene is associated with autopsy-confirmed AD. 相似文献
995.
Mutations in the consensus helicase domains of the Werner syndrome gene. Werner's Syndrome Collaborative Group. 总被引:7,自引:0,他引:7
C E Yu J Oshima E M Wijsman J Nakura T Miki C Piussan S Matthews Y H Fu J Mulligan G M Martin G D Schellenberg 《American journal of human genetics》1997,60(2):330-341
Werner syndrome (WS) is an autosomal recessive disease with a complex phenotype that is suggestive of accelerated aging. WS is caused by mutations in a gene, WRN, that encodes a predicted 1,432-amino-acid protein with homology to DNA and RNA helicases. Previous work identified four WS mutations in the 3' end of the gene, which resulted in predicted truncated protein products of 1,060-1,247 amino acids but did not disrupt the helicase domain region (amino acids 569-859). Here, additional WS subjects were screened for mutations, and the intron-exon structure of the gene was determined. A total of 35 exons were defined, with the coding sequences beginning in the second exon. Five new WS mutations were identified: two nonsense mutations at codons 369 and 889; a mutation at a splice-junction site, resulting in a predicted truncated protein of 760 amino acids; a 1-bp deletion causing a frameshift; and a predicted truncated protein of 391 amino acids. Another deletion is >15 kb of genomic DNA, including exons 19-23; the predicted protein is 1,186 amino acids long. Four of these new mutations either partially disrupt the helicase domain region or result in predicted protein products completely missing the helicase region. These results confirm that mutations in the WRN gene are responsible for WS. Also, the location of the mutations indicates that the presence or absence of the helicase domain does not influence the WS phenotype and suggests that WS is the result of complete loss of function of the WRN gene product. 相似文献
996.
Genki Kato Yasuhiro Shimizu Yuki Arai Natsuki Suzuki Yasutaka Sugamori Miki Maeda Mariko Takahashi Yukihiko Tamura Noriyuki Wakabayashi Ramachandran Murali Takashi Ono Keiichi Ohya Setsuko Mise-Omata Kazuhiro Aoki 《Arthritis research & therapy》2015,17(1)
IntroductionWe designed OP3-4 (YCEIEFCYLIR), a cyclic peptide, to mimic the soluble osteoprotegerin (OPG), and was proven to bind to RANKL (receptor activator of NF-κB ligand), thereby inhibiting osteoclastogenesis. We recently found that another RANKL binding peptide, W9, could accelerate bone formation by affecting RANKL signaling in osteoblasts. We herein demonstrate the effects of OP3-4 on bone formation and bone loss in a murine model of rheumatoid arthritis.MethodsTwenty-four seven-week-old male DBA/1J mice were used to generate a murine model of collagen-induced arthritis (CIA). Then, vehicle or OP3-4 (9 mg/kg/day or 18 mg/kg/day) was subcutaneously infused using infusion pumps for three weeks beginning seven days after the second immunization. The arthritis score was assessed, and the mice were sacrificed on day 49. Thereafter, radiographic, histological and biochemical analyses were performed.ResultsThe OP3-4 treatment did not significantly inhibit the CIA-induced arthritis, but limited bone loss. Micro-CT images and quantitative measurements of the bone mineral density revealed that 18 mg/kg/day OP3-4 prevented the CIA-induced bone loss at both articular and periarticular sites of tibiae. As expected, OP3-4 significantly reduced the CIA-induced serum CTX levels, a marker of bone resorption. Interestingly, the bone histomorphometric analyses using undecalcified sections showed that OP3-4 prevented the CIA-induced reduction of bone formation-related parameters at the periarticular sites.ConclusionThe peptide that mimicked OPG prevented inflammatory bone loss by inhibiting bone resorption and stimulating bone formation. It could therefore be a useful template for the development of small molecule drugs for inflammatory bone loss.
Electronic supplementary material
The online version of this article (doi:10.1186/s13075-015-0753-8) contains supplementary material, which is available to authorized users. 相似文献997.
Ayana Murakami Jun-ichi Hayashi Kazunobu Igawa Miki Tsutsumi Katsuhiko Tomooka Hiroshi Nagai Tatsuo Nehira 《Chirality》2020,32(9):1152-1159
During the course of our chemical analysis of the hydrophilic fractions from marine cyanobacterium Moorena producens, we have isolated natural dolapyrrolidone (Dpy, 1 ), a natural pyrrolidone derived from phenylalanine, for the first time as a single compound. Compound 1 , with an (S)-l absolute stereochemistry, was previously identified as a substructure that is common among several bioactive natural peptides. Surprisingly, the absolute stereochemistry of the isolated natural 1 , determined through total synthesis, was (R)-d . This result was unambiguously determined by HPLC analysis using a chiral stationary column by comparing the retention times of the natural 1 and authentic samples of synthetic enantiomers. To verify the unexpected result, the absolute stereochemistry of the natural 1 was confirmed by X-ray crystallographic analysis of Pt-complex derivative using the synthetic enantiomer. 相似文献
998.
Sequence of a putative promoter region for the rRNA genes of tobacco chloroplast DNA. 总被引:8,自引:14,他引:8 下载免费PDF全文
The nucleotide sequence of the segment of tobacco chloroplast DNA adjacent to and including the start of the 16S rRNA gene has been determined. The region just preceding this gene was found to contain a tRNAVal gene and promoter-type sequences similar to those which occur in E. coli were found before this tRNA gene. E. coli RNA polymerase can recognize these sequences and in vitro co-transcribes the tRNA and rRNA genes. 相似文献
999.
Establishment of Salt Stress Tolerant Rice Plants Through Step Up NaCl Treatment In Vitro 总被引:2,自引:0,他引:2
Establishment of salt tolerant rice plants was examined by single step or step up NaCl treatments of shoot bud clumps in vitro, and variation among in vitro salt tolerant plants were examined by rapid amplified polymorphic DNA (RAPD). Shoot bud clumps were necrotic, stubbed or dead when subjected to single step treatment with 1.5 or 2.0 % NaCl. Conversely all the clumps could grow vigorously when subjected to step up salt treatment with 0.5, 1.0, 1.5 and 2.0 % NaCl at 3 week intervals and 2 % NaCl tolerant plants were established. RAPD revealed shoot bud clumps with and without different NaCl treatments, seedlings from field and grown in vitro, and regenerants from callus were genetically close to one another. Conversely, callus cultures were genetically isolated. Growth under different salt stress conditions was not correlated with the genetic variation, suggesting that 2.0 % NaCl tolerant plants might not result from genetic mutation but were due to adaptation of plants by step up NaCl treatment in vitro. 相似文献
1000.
This is the first report on an observation of food transfer by a mother to her offspring in wild Japanese macaques (Macaca fuscata yakui). On November 6, 1996, an adult female wild Japanese macaque stopped grooming her 1.5–1.6 yr old daughter in order to be
groomed by a young male. Her daughter protested loudly for about 1 min. In response to her daughter's protest, the mother
picked up a mature nut ofQuercus phillyraeoides that was lying near her right hand, and placed it in the daughter's mouth. The daughter's cries were immediately muffled
and she silently ate the acorn's contents, and spat out the pericarp. We inferred that the daughter wanted to be groomed by
her mother, not to receive food. This reported example of treatment resembling tool using behavior in response to an emotional
outcry was precipitated by mother-offspring conflict in the natural habitat. 相似文献