全文获取类型
收费全文 | 133612篇 |
免费 | 4533篇 |
国内免费 | 821篇 |
出版年
2022年 | 325篇 |
2021年 | 695篇 |
2020年 | 502篇 |
2019年 | 591篇 |
2018年 | 12386篇 |
2017年 | 11178篇 |
2016年 | 8436篇 |
2015年 | 2370篇 |
2014年 | 2232篇 |
2013年 | 2701篇 |
2012年 | 7111篇 |
2011年 | 15543篇 |
2010年 | 13714篇 |
2009年 | 9783篇 |
2008年 | 11932篇 |
2007年 | 13495篇 |
2006年 | 2467篇 |
2005年 | 2493篇 |
2004年 | 2915篇 |
2003年 | 2769篇 |
2002年 | 2498篇 |
2001年 | 958篇 |
2000年 | 807篇 |
1999年 | 683篇 |
1998年 | 478篇 |
1997年 | 405篇 |
1996年 | 374篇 |
1995年 | 380篇 |
1994年 | 336篇 |
1993年 | 359篇 |
1992年 | 476篇 |
1991年 | 417篇 |
1990年 | 377篇 |
1989年 | 389篇 |
1988年 | 404篇 |
1987年 | 362篇 |
1986年 | 283篇 |
1985年 | 321篇 |
1984年 | 334篇 |
1983年 | 301篇 |
1982年 | 271篇 |
1981年 | 244篇 |
1980年 | 227篇 |
1979年 | 239篇 |
1978年 | 195篇 |
1977年 | 197篇 |
1976年 | 193篇 |
1975年 | 216篇 |
1972年 | 400篇 |
1971年 | 400篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
991.
Kurt W. Schmid Birgit Kunk Rudolf Kirchmair Martin T?tsch Werner B?cker Reiner Fischer-Colbrie 《The Histochemical journal》1995,27(6):473-481
Summary An antiserum raised against a synthetic peptide derived from the primary amino sequence of rat secretogranin II (chromogranin
C) was used for immunological (quantitative radioimmunoassay analysis) and immunohistochemical studies of normal human endocrine
and nervous tissues. This antibody recognized a novel and biologically active neuropeptide which was coined as secretoneurin.
In endocrine tissues, secretoneurin was mainly co-localized with chromogranin A and B with some exceptions (e.g., parathyroid
gland). Secretoneurin was demonstrated immunohistochemically in the adrenal medulla, thyroid C cells, TSH- and FSH/LH-produting
cells of the anterior pituitary, A and B cells of pancreatic islets, in endocrine cells of the gastrointestinal tract and
the bronchial mucosa, and the prostate. Immunoreactivity determined by radioimmunoassay analysis revealed high secretoneurin
levels in the anterior and posterior pituitary and lower levels in pancreatic and thyroid tissue. A strong secretoneurin immunoreactivity
was also found in ganglion cells of the submucdsal and myenteric plexus of the gastrointestinal tract, and in ganglionic cells
of dorsal root ganglia, peripheral nerves, and ganglion cells of the adrenal medulla. Thus, secretoneurin may serve as a useful
marker of gangliocytic/neuronal differentiation. 相似文献
992.
Martin Witt 《The Histochemical journal》1995,27(2):161-165
Summary Using immunohistochemistry, vasoactive intestinal peptide (VIP) was visualized in taste bud cells of the carp, Cyprinus carpio, and the European catfish, Silurus glanis, by means of light and electron microscopy. Intracellular membrane systems, presumably smooth endoplasmic reticulum, of light (sensory) cells, but not of dark (supporting) cells and basal cells, were densely labelled with antibody. In the frog (four species: Rana temporaria, R. ridibunda, R. arvalis, R. pipiens), taste bud cells did not label. However, the dense basal nerve fibre plexus, some subepithelial ganglionic cells, but no ascending intragemmal fibres, were immunoreactive. In fish, the results support evidence that VIP is involved in the modulation of taste transduction at the level of receptor cells. In the frog, an indirect, possibly vasodilatatory effect on taste perception may be considered. 相似文献
993.
The Penicillium frequentans strain Bi 7/2, using phenol as a sole source of carbon and energy,transformed the fluorinated
phenols 2,3-, 2,4-, 2,5-and 3,4-difluorophenol rapidly. After growth on phenol, resting mycelia of the fungus converted the
difluorophenols completely at an initial concentration of 0.5 mM within 6 hours. The corresponding difluorinated catechols
were found to be intermediates of all difluorophenols investigated. A relatively unspecific phenol hydroxylase catalyzed this
hydroxylation step and showed activities towards all difluorophenols tested. One difluorocatechol was formed from each difluorophenol
substituted with fluorine in the ortho-position, whereas two catechols were formed from 3,4-difluorophenol, due to its two
vacant ortho-positions. A partial defluorination (50-77%) was observed in all cases.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
994.
Fabrice Cornille Loïc Martin Christine Lenoir Didier Cussac Bernard P. Roques Marie-Claude Fournié-Zaluski 《Letters in Peptide Science》1997,4(4-6):207-212
The light chain of tetanus neurotoxin (TeNT L chain)has been shown to be endowed with zinc endopeptidaseactivity, selectively directed towards theGln76–Phe77 bond of synaptobrevin, avesicle-associated membrane protein criticallyinvolved in neuroexocytosis. In previous reports,truncations at the NH2- and COOH-terminus ofsynaptobrevin have shown that the sequence 39–88 ofsynaptobrevin is the minimum substrate of TeNT,suggesting either the requirement of a well-definedthree-dimensional structure of synaptobrevin or a rolein the mechanism of substrate hydrolysis for residuesdistal from the cleavage site. In this study, theaddition of NH2- and COOH-terminal peptides ofsynaptobrevin, S 27–55 (S1) and S 82–93(S2), to the synaptobrevin fragment S 56–81allowed the cleavage of this latter peptide by TeNT tooccur. This appears to result from an activationprocess mediated by the simultaneous binding ofS1 and S2 with complementary sites presenton TeNT as shown by surface plasmon resonanceexperiments. All these results favor anexosite-controlled hydrolysis of synaptobrevin by TeNTprobably involving a conformational change of thetoxin. This could account for the high degree ofsubstrate specificity of TeNT and, probably, botulinumneurotoxins. 相似文献
995.
Edouard Nice Bruno Catimel Martin Lackmann Steven Stacker Andrew Runting Andrew Wilks Nicos Nicola Antony Burgess 《Letters in Peptide Science》1997,4(2):107-120
The isolation of related genes with evolutionary conserved motifs by the application ofpolymerase chain reaction-based molecular biology techniques, or from database searchingstrategies, has facilitated the identification of new members of protein families. Many of theseprotein molecules will be involved in protein–protein interactions (e.g. growth factors,receptors, adhesion molecules), since such interactions are intrinsic to virtually every cellularprocess. However, the precise biological function and specific binding partners of these novelproteins are frequently unknown, hence they are known as orphan molecules.Complementary technologies are required for the identification of the specific ligands orreceptors for these and other orphan proteins (e.g., antibodies raised against crude biologicalextracts or whole cells). We describe herein several alternative strategies for the identification,purification and characterisation of orphan peptide and protein molecules, specifically thesynergistic use of micropreparative HPLC and biosensor techniques. 相似文献
996.
997.
998.
999.
1000.