全文获取类型
收费全文 | 9693篇 |
免费 | 791篇 |
国内免费 | 9篇 |
出版年
2023年 | 42篇 |
2022年 | 79篇 |
2021年 | 171篇 |
2020年 | 111篇 |
2019年 | 109篇 |
2018年 | 160篇 |
2017年 | 128篇 |
2016年 | 269篇 |
2015年 | 411篇 |
2014年 | 500篇 |
2013年 | 624篇 |
2012年 | 774篇 |
2011年 | 758篇 |
2010年 | 451篇 |
2009年 | 440篇 |
2008年 | 595篇 |
2007年 | 647篇 |
2006年 | 610篇 |
2005年 | 530篇 |
2004年 | 535篇 |
2003年 | 513篇 |
2002年 | 508篇 |
2001年 | 108篇 |
2000年 | 80篇 |
1999年 | 116篇 |
1998年 | 148篇 |
1997年 | 105篇 |
1996年 | 94篇 |
1995年 | 104篇 |
1994年 | 87篇 |
1993年 | 82篇 |
1992年 | 89篇 |
1991年 | 39篇 |
1990年 | 48篇 |
1989年 | 34篇 |
1988年 | 37篇 |
1987年 | 23篇 |
1986年 | 33篇 |
1985年 | 32篇 |
1984年 | 28篇 |
1983年 | 27篇 |
1982年 | 37篇 |
1981年 | 29篇 |
1980年 | 22篇 |
1979年 | 20篇 |
1978年 | 12篇 |
1977年 | 24篇 |
1976年 | 17篇 |
1974年 | 8篇 |
1973年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
PCR-mediated screening and labeling of DNA from clones 总被引:1,自引:0,他引:1
Yun Hai Lu Sylvie Nègre Philippe Leroy Michel Bernard 《Plant Molecular Biology Reporter》1993,11(4):345-349
A simplified and economical protocol for DNA library screening and nonradioactive labeling is described. Bacterial clones
are lysed in 1% of Triton X-100 and subjected to polymerase chain reaction in the presence of digoxigenin-11-dUTP to screen
and simultaneously to label the DNA inserts. Bacteriallysates are stable in storage at −20°C and can be used repeatedly for
PCR-mediated labeling. In this protocol, very low concentrations of dNTP, digoxigenin-dUTP, and primers are used in combination
with a reduced reaction volume. This will considerably reduce the expense of screening and labeling bacterial clones and facilitate
the exchange of DNA probes among laboratories. 相似文献
112.
Summary Twenty-three independent kanamycin resistant lines were obtained after cocultivation of longterm embryogenic cultures of three Asparagus officinalis L. genotypes with an Agrobacterium tumefaciens strain harboring ß-glucuronidase and neomycin phosphotransferase II genes. All the lines showed ß-glucuronidase activity by histological staining. DNA analysis by Southern blots of the kanamycin resistant embryogenic lines and of a plant regenerated from one of them confirmed the integration of the T-DNA.Abbreviations GUS
ß-glucuronidase
- X-Gluc
5-bromo-4-chloro-3indolyl ß-D-glucuronic acid
- NPT II
neomycin phosphotransferase II 相似文献
113.
Aristóteles Philippe Nunes Queiroz Maria Lúcia Góes Araújo Nigel E. Hussey Rosângela P. T. Lessa 《Journal of fish biology》2023,102(1):27-43
Understanding the ecological role of species with overlapping distributions is central to inform ecosystem management. Here we describe the diet, trophic level and habitat use of three sympatric stingrays, Hypanus guttatus, H. marianae and H. berthalutzae, through combined stomach content and stable isotope (δ13C and δ15N) analyses. Our integrated approach revealed that H. guttatus is a mesopredator that feeds on a diverse diet of benthic and epibenthic marine and estuarine organisms, principally bivalve molluscs, Alpheus shrimp and teleost fishes. Isotopic data supported movement of this species between marine and estuarine environments. H. berthalutzae is also a marine generalist feeder, but feeds primarily on teleost fishes and cephalopods, and consequently occupies a higher trophic level. In contrast, H. marianae is a mesopredator specialized on shrimps and polychaetas occurring only in the marine environment and occupying a low niche breadth. While niche overlap occurred, the three stingrays utilized the same prey resources at different rates and occupied distinct trophic niches, potentially limiting competition for resources and promoting coexistence. These combined data demonstrate that these three mesopredators perform different ecological roles in the ecosystems they occupy, limiting functional redundancy. 相似文献
114.
In situ hybridization of atrial natriuretic peptide mRNA in the endothelial cells of human umbilical vessels 总被引:1,自引:0,他引:1
Wen Qin Cai Giorgio Terenghi Philippe Bodin Geoffrey Burnstock Julia M. Polak 《Histochemistry and cell biology》1993,100(4):277-283
The localization of mRNA encoding preproatrial natriuretic peptide (ANP) was investigated in cultured human umbilical vein endothelial cells (HUVEC) and tissue preparations of umbilical vein and artery. The techniques used were in situ hybridization and in situ hybridization combined with immunocytochemistry, using 32P-radiolabelled and non-radioactive digoxigenin labelled complementary RNA probes. Human ANP mRNAs are mainly localized in the endothelial cells of the umbilical vein and, to a lesser extent, in the endothelial cells of the umbilical artery. The autoradiographic labelling and the intensity of digoxigenin staining were significantly reduced by treatment with RNase before in situ hybridization. This study provides unequivocal evidence for the expression of the ANP gene in the endothelial cells of human umbilical vessels, confirming that these endothelial cells have the ability to synthesize this peptide. The functional significance of the presence of the ANP mRNA in the endothelial cells of human umbilical vessels is discussed. 相似文献
115.
116.
Machhour Ghazali Michel Philippe Alain Deguercy Pierre Gounon Jean-Marc Gallo Joseph Schrevel 《Biology of the cell / under the auspices of the European Cell Biology Organization》1989,67(2):173-184
In Gregarina blaberae a Mr = 47 000 and a Mr = 260–240 000 doublet polypeptides reacted in immunoblotting: i) with a polyclonal monospecific rabbit antibody to frog muscular actin, a monoclonal anti-actin antibody against chicken gizzard; and ii) with polyclonal and monoclonal antibodies to human erythrocyte β-spectrin, respectively. The Mr = 47 000 actin-like protein is associated with the ghost and a contractille cytoplasmic extract. The presence of an actin-like protein in Gregarina and Lecudina and its cellular distribution in the cortex indicated that the gliding movement might involve an actin-myosin system in contrast to previous studies. Immunofluorescence showed clear differences between the anterior part of Gregarina and Lecudina which illustrated the high cell polarity of these protozoa. The Mr = 260–240 000 doublet was detected in SDS-PAGE from G. blaberae trophozoite ghosts but not in the cytoplasmic extracts or in extracts from sexual stages, indicating that the presence of these spectrin-like proteins is stage-dependent. Visualization of the Mr = 260–240 000 by immunofluorescence showed clear species differences, with rings arranged perpendicular to the longitudinal narrow folds of G. blaberae, with longitudinal lines underlying the folds of L. pellucida and with lines separating the large folds of Selenidium pendula. The cellular distribution is consistent with a stabilizer function of the spectrin-like proteins in the scaffolding of the cortex of gregarines according to the high diversity of the cell-shape and the cell motility systems in gregarines. The presence of spectrin-like proteins in protozoa and particularly in parasites from primitive arthropods indicated that ancestral spectrin genes could the Mr = 260–240 000 form. 相似文献
117.
Jean Quancard Philippe Karoyan Sandrine Sagan Odile Convert Solange Lavielle Gérard Chassaing Olivier Lequin 《European journal of biochemistry》2003,270(13):2869-2878
Residue Leu10 of substance P (SP) is critical for NK-1 receptor recognition and agonist activity. In order to probe the bioactive conformation of this residue, cis- and trans-3-substituted prolinoleucines were introduced in position 10 of SP. The substituted SP analogues were tested for their affinity to human NK-1 receptor specific binding sites (NK-1M and NK-1m) and their potency to stimulate adenylate cyclase and phospholipase C in CHO cells transfected with the human NK-1 receptor. [trans-3-prolinoleucine10]SP retained affinity and potency similar to SP whereas [cis-3-prolinoleucine10]SP shows dramatic loss of affinity and potency. To analyze the structural implications of these biological results, the conformational preferences of the SP analogues were analyzed by NMR spectroscopy and minimum-energy conformers of Ac-cis-3-prolinoleucine-NHMe, Ac-trans-3-prolinoleucine-NHMe and model dipeptides were generated by molecular mechanics calculations. From NMR and modeling studies it can be proposed that residue Leu10 of SP adopts a gauche(+) conformation around the chi1 angle and a trans conformation around the chi2 angle in the bioactive conformation. Together with previously published results, our data indicate that the C-terminal SP tripeptide should preferentially adopt an extended conformation or a PPII helical structure when bound to the receptor. 相似文献
118.
In this paper the NMR secondary chemical shifts, that are estimated from a set of 3D-structures, are compared with the observed ones to appraise the behaviour of a known x-ray diffraction structure (of the bovine pancreatic trypsin inhibitor protein) when various molecular dynamics are applied. The results of a 200 ps molecular dynamics under various conditions are analysed and different ways to modify the molecular dynamics are considered. With the purpose of avoiding the time-consuming explicit representation of the solvent (water) molecules, an attempt was made to understand the role of the solvent and to develop an implicit representation, which may be refined. A simulation of hydrophobic effects in an aqueous environment is also proposed which seems to provide a better approximation of the observed solution structure of the protein. 相似文献
119.
Eukaryotic polypeptide chain release factor eRF3 is an eRF1- and ribosome-dependent guanosine triphosphatase. 总被引:11,自引:1,他引:10
下载免费PDF全文
![点击此处可从《RNA (New York, N.Y.)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
L Frolova X Le Goff G Zhouravleva E Davydova M Philippe L Kisselev 《RNA (New York, N.Y.)》1996,2(4):334-341
Termination of translation in eukaryotes is governed by two polypeptide chain release factors, eRF1 and eRF3 on the ribosome. eRF1 promotes stop-codon-dependent hydrolysis of peptidyl-tRNA, and eRF3 interacts with eRF1 and stimulates eRF1 activity in the presence of GTP. Here, we have demonstrated that eRF3 is a GTP-binding protein endowed with a negligible, if any, intrinsic GTPase activity that is profoundly stimulated by the joint action of eRF1 and the ribosome. Separately, neither eRF1 nor the ribosome display this effect. Thus, eRF3 functions as a GTPase in the quaternary complex with ribosome, eRF1, and GTP. From the in vitro uncoupling of the peptidyl-tRNA and GTP hydrolyses achieved in this work, we conclude that in ribosomes both hydrolytic reactions are mediated by the formation of the ternary eRF1-eRF3-GTP complex. eRF1 and the ribosome form a composite GTPase-activating protein (GAP) as described for other G proteins. A dual role for the revealed GTPase complex is proposed: in " GTP state," it controls the positioning of eRF1 toward stop codon and peptidyl-tRNA, whereas in "GDP state," it promotes release of eRFs from the ribosome. The initiation, elongation, and termination steps of protein synthesis seem to be similar with respect to GTPase cycles. 相似文献
120.