全文获取类型
收费全文 | 5405篇 |
免费 | 282篇 |
国内免费 | 2篇 |
专业分类
5689篇 |
出版年
2023年 | 12篇 |
2022年 | 32篇 |
2021年 | 67篇 |
2020年 | 46篇 |
2019年 | 55篇 |
2018年 | 93篇 |
2017年 | 80篇 |
2016年 | 128篇 |
2015年 | 185篇 |
2014年 | 203篇 |
2013年 | 355篇 |
2012年 | 373篇 |
2011年 | 383篇 |
2010年 | 248篇 |
2009年 | 235篇 |
2008年 | 368篇 |
2007年 | 383篇 |
2006年 | 337篇 |
2005年 | 316篇 |
2004年 | 329篇 |
2003年 | 311篇 |
2002年 | 267篇 |
2001年 | 51篇 |
2000年 | 43篇 |
1999年 | 65篇 |
1998年 | 63篇 |
1997年 | 61篇 |
1996年 | 43篇 |
1995年 | 62篇 |
1994年 | 41篇 |
1993年 | 47篇 |
1992年 | 31篇 |
1991年 | 25篇 |
1990年 | 39篇 |
1989年 | 25篇 |
1988年 | 18篇 |
1987年 | 26篇 |
1986年 | 17篇 |
1985年 | 28篇 |
1984年 | 24篇 |
1983年 | 23篇 |
1982年 | 24篇 |
1981年 | 32篇 |
1980年 | 14篇 |
1979年 | 11篇 |
1978年 | 13篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1975年 | 9篇 |
1965年 | 6篇 |
排序方式: 共有5689条查询结果,搜索用时 12 毫秒
911.
Yohei Hashimoto Hiroyuki Ishizone Midori Moriyasu Kazuko Kawanishi Atsushi Kato Masaru Ogura 《Phytochemistry》1984,23(3):693-694
Two new triterpenes from the root of Periandra dulcis were found to be 3,25-dioxoolean-12(13)-en-30-oic acid and 3,25-dioxoolean-18(19)-en-30-oic acid. 相似文献
912.
Masayoshi Tachibana Lingmin Lu Hiroshi Hiai Atsushi Tamura Yoshibumi Matsushima Hayase Shisa 《Experimental Animals》2006,55(2):91-95
Increasing exposure to environmental endocrine disruptor, xeno-estrogen, is a serious hazard to male reproductive activity. To explore possible genetic control in susceptibility to xeno-estrogen, the weight reduction of testes induced by the continuous administration of a synthetic estrogen, diethylstilbesterol, were investigated by quantitative trait analysis in LEXF and FXLE recombinant inbred strain rats, consisting of 21 independent strains, 9 of their substrains, parental F344/Stm and LE/Stm strains, and (F344 x LE)F1. For the weight of testes, one highly significant quantitative trait locus (QTL) and one significant QTL were mapped on chromosomes 7 and 1, respectively. The QTL on chromosome 7 is closely associated with c-myc. Pituitary weight and serum prolactin were also variable among recombinant inbred strains, but no QTL was detected for them in this study. 相似文献
913.
Enhanced Gene Transfer with Fusogenic Liposomes Containing Vesicular Stomatitis Virus G Glycoprotein 总被引:1,自引:0,他引:1 下载免费PDF全文
Exposure of Lipofectin-DNA complexes to the partially purified G glycoprotein of the vesicular stomatitis virus envelope (VSV-G) results in loss of serum-mediated inhibition and in enhanced efficiency of gene transfer. Sucrose density gradient sedimentation analysis indicated that the VSV-G associates physically with the DNA-lipid complex to produce a VSV-G liposome. The ability to incorporate surrogate viral or cellular envelope components such as VSV-G into liposomes may allow more-efficient and possibly targeted gene delivery by lipofection, both in vitro and in vivo. 相似文献
914.
Mathias Robert S.; Mikoshiba Katsuhiko; Michikawa Takayuki; Miyawaki Atsushi; Ives Harlan E. 《American journal of physiology. Cell physiology》1998,274(6):C1456
The effect ofinositol 1,4,5-trisphosphate(IP3) receptor blockade onplatelet-derived growth factor (PDGF), fibroblast growth factor (FGF),endothelin-1 (ET-1), or -thrombin receptor-mediated intracellularCa2+(Ca2+i) release was examined using fura 2 microspectrofluorometry in single Chinese hamster ovary cells andmyoblasts. Blockade of the IP3receptor was achieved by microinjection of heparin or monoclonalantibody (MAb) 18A10 into the IP3type 1 receptor. Heparin completely inhibitedCa2+i release after flash photolysis withcaged IP3 and after exposure toPDGF and FGF. In contrast, heparin failed to blockCa2+i release after -thrombin andET-1. After application of ligand, IP3 levels were five- to sevenfoldhigher for -thrombin than for ET-1 or PDGF.IP3 levels after PDGF and ET-1were comparable. Similar to heparin, MAb 18A10 blockedCa2+i release after PDGF but failed toblock Ca2+i release after ET-1 or-thrombin. These data suggest that the mechanisms of Ca2+i release by tyrosine kinase andcertain 7-transmembrane receptors may differ. Although both receptortypes use the IP3-signaling system, the ET-1 and -thrombin receptors may have a second,alternative mechanism for activatingCa2+i release. 相似文献
915.
A. Sekizawa Atsushi Taguchi Akira Watanabe Takehiko Kimura Hiroshi Saito Takumi Yanaihara Takeshi Sato 《Human genetics》1998,102(4):393-396
We have extended a previously developed method that allows prenatal DNA diagnosis of female fetuses through the isolation
of single nucleated erythrocytes from maternal blood by developing a method that can distinguish between maternal and fetal
nucleated erythrocytes. Nucleated erythrocytes were separated by a density-gradient method and then collected by micromanipulation.
Sex was determined after primer extension preamplification (PEP) of the entire genome of a single cell, and human leukocyte
antigen (HLA)-DQ α type was determined after further amplification of this gene. The HLA-DQ α genotype of fetal erythrocytes
in maternal blood samples and their corresponding paternal and maternal lymphocytes were successfully determined in all cases.
The accuracy of the method was determined by using single nucleated erythrocytes from umbilical cord blood from five normal
deliveries. This is the first demonstration that the fetal HLA-DQ α gene sequences can be identified in a small aliquot of
a single nucleated erythrocyte in maternal blood. We believe that this method ushers in a new era in which the reliability
and accuracy of noninvasive prenatal DNA diagnosis from maternal blood is markedly improved.
Received: 18 April 1997 / Accepted: 1 October 1997 相似文献
916.
Clara Shionyu-Mitsuyama Atsushi Hijikata Toshiyuki Tsuji Tsuyoshi Shirai 《Journal of structural and functional genomics》2016,17(4):135-146
The fast heuristic graph match algorithm for small molecules, COMPLIG, was improved by adding a structural superposition process to verify the atom–atom matching. The modified method was used to classify the small molecule ligands in the Protein Data Bank (PDB) by their three-dimensional structures, and 16,660 types of ligands in the PDB were classified into 7561 clusters. In contrast, a classification by a previous method (without structure superposition) generated 3371 clusters from the same ligand set. The characteristic feature in the current classification system is the increased number of singleton clusters, which contained only one ligand molecule in a cluster. Inspections of the singletons in the current classification system but not in the previous one implied that the major factors for the isolation were differences in chirality, cyclic conformations, separation of substructures, and bond length. Comparisons between current and previous classification systems revealed that the superposition-based classification was effective in clustering functionally related ligands, such as drugs targeted to specific biological processes, owing to the strictness of the atom–atom matching. 相似文献
917.
918.
Heme synthase (ferrochelatase) catalyzes the removal of iron from heme and demetalation of metalloporphyrins 总被引:2,自引:0,他引:2
Taketani S Ishigaki M Mizutani A Uebayashi M Numata M Ohgari Y Kitajima S 《Biochemistry》2007,46(51):15054-15061
The red pigments in meat products, including cooked cured ham, arise from the reaction of myoglobin with nitric oxide generated from exogenous nitrite. Since carcinogenic nitrosoamines may be generated by the treatment of meats with nitrite, the production of nitrite-free meat products is an attractive alternative. Raw dry-cured (Parma) hams are produced by the treatment of meats with salts other than nitrite. Analysis of pigments in raw dry-cured hams reveals that the main pigment is zinc protoporphyrin, suggesting that the conversion of heme to zinc protoporphyrin occurs via an iron-removal reaction from myoglobin heme during the processing of raw hams. Purification of the iron-removal enzyme showed that it was identical to ferrochelatase. Recombinant ferrochelatase in combination with NADH-cytochrome b5 reductase catalyzed NADH-dependent iron-removal reaction from hemin and hemoproteins. Metal ions such as zinc and cobalt were also removed from the corresponding metalloporphyrins. The addition of zinc ions led to the formation of zinc protoporphyrin. In cultured cells, the conversion of zinc mesoporphyrin to mesoheme was observed to be dependent on ferrochelatase and could be markedly induced during erythroid differentiation. This is the first demonstration of a new enzyme reaction, the reverse reaction of ferrochelatase, which may contribute to a new route of the recycling of protoporphyrin and heme in cells. 相似文献
919.
Sugimoto K Kage H Aki N Sano A Kitagawa H Nagase T Yatomi Y Ohishi N Takai D 《Biochemical and biophysical research communications》2007,359(3):497-502
The field of epigenetics has made progress by the identification of the small RNA-mediated epigenetic modification. However, little is known about the key proteins. Here, we report that the human PIWI-like family is a candidate protein that is involved in the pathway responsible for chromatin remodeling. The PIWI-like family proteins, expressed as the Flag-fusion proteins, formed a bulky body and localized to the nuclear periphery. Transient transfection of PIWI-like 4 (PIWIL4), only member of the PIWI-like family that was ubiquitously expressed in human tissues, induced histone H3 lysine 9 methylation at the p16(Ink4a) (CDKN2A) locus. The elevated level of histone methylation resulted in the downregulation of the p16(Ink4a) gene. These results suggest PIWIL4 plays important roles in the chromatin-modifying pathway in human somatic cells. 相似文献
920.