全文获取类型
收费全文 | 2914篇 |
免费 | 135篇 |
国内免费 | 3篇 |
出版年
2021年 | 19篇 |
2019年 | 16篇 |
2018年 | 23篇 |
2017年 | 17篇 |
2016年 | 27篇 |
2015年 | 48篇 |
2014年 | 68篇 |
2013年 | 251篇 |
2012年 | 156篇 |
2011年 | 146篇 |
2010年 | 91篇 |
2009年 | 87篇 |
2008年 | 159篇 |
2007年 | 162篇 |
2006年 | 171篇 |
2005年 | 180篇 |
2004年 | 186篇 |
2003年 | 205篇 |
2002年 | 192篇 |
2001年 | 33篇 |
2000年 | 20篇 |
1999年 | 32篇 |
1998年 | 50篇 |
1997年 | 51篇 |
1996年 | 35篇 |
1995年 | 32篇 |
1994年 | 35篇 |
1993年 | 24篇 |
1992年 | 39篇 |
1991年 | 30篇 |
1990年 | 19篇 |
1989年 | 23篇 |
1988年 | 31篇 |
1987年 | 22篇 |
1986年 | 10篇 |
1985年 | 22篇 |
1984年 | 29篇 |
1983年 | 31篇 |
1982年 | 42篇 |
1981年 | 34篇 |
1980年 | 26篇 |
1979年 | 17篇 |
1978年 | 17篇 |
1977年 | 18篇 |
1976年 | 15篇 |
1975年 | 19篇 |
1974年 | 14篇 |
1973年 | 9篇 |
1970年 | 7篇 |
1968年 | 7篇 |
排序方式: 共有3052条查询结果,搜索用时 31 毫秒
61.
62.
63.
The chemical synthesis of two new glycerophosphatide analogues containing steroid groups, i.e., 1,2-dipalmitoyl-rac-glyceryl-3-phosphoryl-3′β-cholesterol and 1,2-dipalmitoyl-rac-glyceryl-3-phosphoryl-20′-(3β-hydroxy norpregn-5-ene) is described. 相似文献
64.
T Hakoshima T Itoh K Gohda K Tomita S Uesugi S Nishikawa H Morioka E Ohtsuka M Ikehara 《FEBS letters》1991,290(1-2):216-220
Complex of a mutant ribonuclease T1 (Y4SW) with a non-cognizable ribonucleotide, 2′AMP, has been determined and refined by X-ray diffraction at 1.7 Å resolution. The 2′AMP molecule locates at a new base-binding site which is remote from the guanine-recognition site, where 2′GMP was found to be bound. The nucleotide adopts the anti conformation of the glycosidic bond and C3′-exo sugar pucker. There exists a single hydrogen bond between the adenine base and the enzyme, and, therefore, the site found is apparently a non-specific binding site. The results indicate that the binding of 2′AMP to the guanine-recognition site is weaker than that to the new binding site. 相似文献
65.
Shigenobu Kanba Nobuyuki Sasakawa Toshio Nakaki Kiyoko-Shimizu Kanba Gohei Yagi Ryuichi Kato Elliott Richelson 《Journal of neurochemistry》1991,57(6):2011-2015
Prostaglandin E1 (PGE1)-mediated transmembrane signal control systems were investigated in intact murine neuroblastoma cells (clone N1E-115). PGE1 increased intracellular levels of total inositol phosphates (IP), cyclic GMP, cyclic AMP, and calcium ([Ca2+]i). PGE1 transiently increased inositol 1,4,5-trisphosphate formation, peaking at 20 s. There was more than a 10-fold difference between the ED50 for PGE1 at cyclic AMP formation (70 nM) and its ED50 values at IP accumulation (1 microM), cyclic GMP formation (2 microM), and [Ca2+]i increase (5 microM). PGE1-mediated IP accumulation, cyclic GMP formation, and [Ca2+]i increase depended on both the concentration of PGE1 and extracellular calcium ions. PGE1 had more potent intrinsic activity in cyclic AMP formation, IP accumulation, and cyclic GMP formation than did PGE2, PGF2 alpha, or PGD2. A protein kinase C activator, 4 beta-phorbol 12 beta-myristate 13 alpha-acetate, had opposite effects on PGE1-mediated IP release and cyclic GMP formation (inhibitory) and cyclic AMP formation (stimulatory). These data suggest that there may be subtypes of the PGE1 receptor in this clone: a high-affinity receptor mediating cyclic AMP formation, and a low-affinity receptor mediating IP accumulation, cyclic GMP formation, and intracellular calcium mobilization. 相似文献
66.
67.
Toshio Okazaki Masakazu Watanabe Kenya Mizuguchi Kazumi Hosoya 《Ichthyological Research》1991,38(2):133-140
Two types of the dark chub,Zacco temmincki, collected from 10 river systems in Japan were genetically characterized at 27 protein coding loci using starch-gel electrophoresis. They were fixed for different alleles at 13 loci. No hybrid individuals were observed, even in specimens collected in stations where both types appear sympatrically, indicating that each type of the dark chub represents a distinct species. 相似文献
68.
Hiide Yoshino Nobuyuki Miyatani Megumi Saito Toshio Ariga Alessandra Lugaresi Norman Latov Yasunori Kushi Takeshi Kasama Robert K. Yu 《Journal of neurochemistry》1992,59(5):1684-1691
The gangliosides GM1 and GD1b have recently been reported to be potential target antigens in human motor neuron disease (MND) or motor neuropathy. The mechanism for selective motoneuron and motor nerve impairment by the antibodies directed against these gangliosides, however, is not fully understood. We recently investigated the ganglioside composition of isolated bovine spinal motoneurons and found that the ganglioside pattern of the isolated motoneurons was extremely complex. GM1, GD1a, GD1b, and GT1b, which are major ganglioside components of CNS tissues, were only minor species in motoneurons. Among the various ganglioside species in motoneurons, several were immunoreactive to sera from patients with MND and motor neuropathy. One of these gangliosides was purified from bovine spinal cord and characterized as N-glycolylneuraminic acid-containing GM1 [GM1(NeuGc)] by compositional analysis, fast atom bombardment mass spectra, and the use of specific antibodies. Among seven sera with anti-GM1 antibody activities, five sera reacted with GM1(NeuGc) and two did not. Two other gangliosides, which were recognized by another patient's serum, appeared to be specific for motoneurons. We conclude that motoneurons contained, in addition to the known ganglioside antigens GM1 and GD1b, other specific ganglioside antigens that could be recognized by sera from patients with MND and motor neuropathy. 相似文献
69.
Genetic Manipulation of the Extent of Desaturation of Fatty Acids in Membrane Lipids in the Cyanobacterium Synechocystis PCC6803 总被引:1,自引:0,他引:1
Wada Hajime; Gombos Zoltan; Sakamoto Toshio; Murata Norio 《Plant & cell physiology》1992,33(5):535-540
The desA gene of the cyanobacterium, Synechocystis PCC6803,is responsible for the desaturation of fatty acids at the 相似文献
70.
Toshio Sugimoto Tsutomu Kawasaki Tomohiko Kato Robert F. Whittier Daisuke Shibata Yukio Kawamura 《Plant molecular biology》1992,20(4):743-747
A full-length cDNA encoding a subunit of phosphoenolpyruvate carboxylase (PEPC) was isolated from a developing seed expression library of the C3 plant Glycine max. The corresponding mRNA is present at similar levels in leaf, stem, root and developing seed. Two potential start codons exist, and the activity of protein initiated from the first such codon could be subject to regulation by protein kinase. Sequence comparison shows a similar upstream start codon in the case of the Ppc2 gene from Mesembryanthemum crystallinum, previously assumed to lack the sequences necessary for phosphorylation. The soybean encoded protein tends to resemble other C3-type PEPC proteins more closely than those implicated in C4 or crassulacean acid metabolism. 相似文献