全文获取类型
收费全文 | 5269篇 |
免费 | 396篇 |
国内免费 | 7篇 |
专业分类
5672篇 |
出版年
2023年 | 21篇 |
2022年 | 34篇 |
2021年 | 83篇 |
2020年 | 50篇 |
2019年 | 73篇 |
2018年 | 82篇 |
2017年 | 94篇 |
2016年 | 154篇 |
2015年 | 231篇 |
2014年 | 264篇 |
2013年 | 342篇 |
2012年 | 385篇 |
2011年 | 371篇 |
2010年 | 232篇 |
2009年 | 253篇 |
2008年 | 332篇 |
2007年 | 303篇 |
2006年 | 336篇 |
2005年 | 299篇 |
2004年 | 308篇 |
2003年 | 287篇 |
2002年 | 270篇 |
2001年 | 69篇 |
2000年 | 49篇 |
1999年 | 64篇 |
1998年 | 62篇 |
1997年 | 35篇 |
1996年 | 31篇 |
1995年 | 36篇 |
1994年 | 40篇 |
1993年 | 38篇 |
1992年 | 45篇 |
1991年 | 28篇 |
1990年 | 29篇 |
1989年 | 27篇 |
1988年 | 28篇 |
1987年 | 14篇 |
1986年 | 18篇 |
1985年 | 24篇 |
1984年 | 28篇 |
1983年 | 18篇 |
1982年 | 17篇 |
1981年 | 16篇 |
1980年 | 23篇 |
1979年 | 15篇 |
1978年 | 12篇 |
1977年 | 16篇 |
1976年 | 12篇 |
1975年 | 12篇 |
1973年 | 8篇 |
排序方式: 共有5672条查询结果,搜索用时 15 毫秒
51.
Katsuhiko Mikoshiba Kimio Akagawa Ken Takamatsu Yasuzo Tsukada 《Journal of neurochemistry》1982,39(4):1028-1032
The cerebellar hypoplasia induced by hereditary hyperbilirubinemia in the Gunn rat was analyzed neurochemically and immunohistochemically. The antiserum against myelin basic protein was used to visualize the arborization of the fibers in the cerebellum. Arborization was very scarce in the affected lobes of the homozygous (jj) cerebellum. Na,K-ATPase activity did not show significant differences between the jj and the control (Jj) cerebellum. The concentration of norepinephrine in the jj cerebellum was about 1.5 times that of the control. However, the activation ratio of the Na,K-ATPase by norepinephrine and other catecholamines such as dopamine and isoproterenol was about twice as high as the basal activity, and no significant difference was observed between the jj and the Jj cerebella. The glutamic acid decarboxylase activity of the jj cerebellum did not differ significantly from that of the control. 相似文献
52.
Katsuhiko Mikoshiba Shinichi Kohsaka Ken Takamatsu Emiko Aoki Yasuzo Tsukada 《Journal of neurochemistry》1980,34(4):835-844
Abstract: Cerebral cortex from reeler mutant mice was examined morphologically and biochemically. The sequential process of postnatal cell migration in the cerebral cortex of reeler (rl/rl) was examined morphologically. The dense cellular cortical plate lies below the molecular layer near the cerebral surface just after birth in normal mice while in reeler most of the cells are concentrated in the center of the cortex. In the cortex of adult reeler, the broad laminar structure of the neurons could be seen to form inverted positions in the cortical layers. The total wet weight, and the concentration of DNA and RNA in the pallium cerebri from reeler did not differ significantly from those in the control. As to the protein profiles of the pallium cerebri detected by SDS- polyacrylamide gel electrophoresis, no significant differences were observed. Activities of CNPase (2',3'-cyclic nucleotide 3'-phosphohydrolase), which is a myelin enzyme of CNS, and choline acetyltransferase were at the same level in both the reeler and the control. Therefore, reeler mutation does not appear to affect the genetically determined cell numbers, number of cholinergic fibers, and myelination. By autoradiographic observation of the cerebral cortex after intraperitoneal injection of [14 C]2-deoxyglucose, it was revealed that 2-deoxyglucose was incorporated intensively into the fourth layer (granular layer) of the cerebrum from the control. In reeler it was also incorporated into the granular layer but in a more widespread distribution. We conclude that terminals to the granular layer make metabolically active synapse, perhaps even in a manner inverted from normal. 相似文献
53.
54.
Koshiro Yoshioka Mitsuo Fujimori Kiwamu Yamaoka Kazuyoshi Ueda 《International journal of biological macromolecules》1982,4(1):55-61
The electric birefringence and circular dichroism spectra of poly(l-ornithine hydrobromide) have been measured in ethanol/water, 2-propanol/water and tertiary butyl alcohol/water mixtures of various compositions. This charged polypeptide underwent a transition from the coil conformation to the helical conformation at high alcohol content in every case tested. Anomalous birefringence signals, indicative of a field-induced helix-to-coil transition. were observed at high electric fields only in the case of ethanol/water mixtures. The reversing-pulse electric birefringence of this polypeptide has been studied in ethanol/water mixtures and in neutral aqueous solution. Upon rapid reversal of the pulse field, no transient could be observed. This confirms that the electric-field orientation of poly(l-ornithine hydrobromide) results predominantly from the contribution of the counterion-induced dipole moment, regardless of its molecular conformations. It is very probable that the backbone permanent dipole moment of the helical conformation is largely suppressed by the counterion-induced dipole moment in the ionized form. 相似文献
55.
Ken Inouye Kunio Watanabe Yoshihiro Tochino Masashi Kobayashi Yukio Shigeta 《Biopolymers》1981,20(9):1845-1858
The trypsin-catalyzed coupling of bovine (Boc)2-desoctapeptide (B23-B30)-insulin with synthetic octapeptides, H-Gly-X2-X3-X4-Thr-Pro-Lys(Boc)-Thr-OH (X2 = Phe or Ala, X3 = Phe or Ala, X4 = Tyr or Ala), followed by deprotection and purification produced the [AlaB24, ThrB30]-, [AlaB25, ThrB30]-, and [AlaB26, ThrB30]-analogs of bovine insulin in yields of 32, 35, and 32%, respectively. The biological activity of these analogs decreased in the order, normal insulin ([ThrB30]-bovine insulin) = AlaB26-insulin > AlaB25-insulin > AlaB24-insulin, as assayed for receptor binding and some other biological effects, in contrast with the corresponding Leu-analogs of human insulin, in which the activity decreased in the order, normal insulin > LeuB24-insulin > LeuB25-insulin. The affinity to insulin antibodies greatly diminished in both AlaB24-insulin and LeuB24-insulin but not in the B25-substituted analogs. The CD spectra of the Leu- and the Ala-analogs were compared with those of normal insulins to show that no apparent correlation seems to exist between the decrease in biological activity and the conformational changes observed in solution. The effects of organic solvents on the peptide-bond equilibrium and on the stability of trypsin are also discussed. 相似文献
56.
Takao Nakamura Yoshiki Sugita Ken Hashimoto Yoshimasa Yoneyama Anthony V. Pisciotta 《Biochemical and biophysical research communications》1976,70(2):567-572
The thermodynamic parameters of the CO-equilibria of isolated chains of hemoglobin A and of two α-chains in hemoglobins M Milwaukee-I and Saskatoon at 25°, pH 7.0 were determined. The parameters for the binding of the first CO molecule to the hemoglobins M were ΔH′=?17 and ?18 kcal/mole heme and ΔS′=?30 and ?29 e.u. for hemoglobins M Milwaukee-I and Saskatoon, respectively. In contrast to this the characteristics of the second step of the binding were ΔH′=+5.9· and +4.3 kcal/mole and ΔS′=+51 and +49 e.u. These values for the second step were also significantly different from those of the isolated α-chain (ΔH′=?15 kcal/mole and ΔS′=?11 e.u.). 相似文献
57.
58.
Masako Kitajima Yoshiko Ohkura Takayoshi Shotake Ken Nozawa 《Primates; journal of primatology》1975,16(4):399-404
Genetic variation at the locus controlling A1 band of erythrocyte esterase was found in the Japanese macaque,Macaca fuscata. Existence of four alleles,Es-A 1 1 ,Es-A 1 2 ,Es-A 1 3 , andEs-A 1 4 , controlling the mobility of the band and codominance relation between them were postulated. A majority of the troops examined were monomorphic inEs-A 1 1-1 phenotype, and the variant phenotypes were observed to occur only in Yugawara-Ihama, Arashiyama, and Koshima areas. 相似文献
59.
60.
Taxonomy Plantago asiatica mosaic virus belongs to the genus Potexvirus in the family Alphaflexiviridae of the order Tymovirales.Virion and genome propertiesPlantago asiatica mosaic virus (PlAMV) has flexuous virions of approximately 490–530 nm in length and 10–15 nm in width. The genome of PlAMV consists of a single‐stranded, positive‐sense RNA of approximately 6.13 kb. It contains five open reading frames (ORFs 1–5), encoding a putative viral polymerase (RdRp), movement proteins (triple gene block proteins, TGBp1‐3), and coat protein (CP), respectively.Host rangePlAMV has an exceptionally wide host range and has been isolated from various wild plants, including Plantago asiatica, Nandina domestica, Rehmannia glutinosa, and other weed plants. Experimentally PlAMV can infect many plant species including Nicotiana benthamiana and Arabidopsis thaliana. It also infects ornamental lilies and frequently causes severe necrotic symptoms. However, host range varies depending on isolates, which show significant biological diversity within the species.Genome diversityPlAMV can be separated into five clades based on phylogenetic analyses; nucleotide identities are significantly low between isolates in the different clades.TransmissionPlAMV is not reported to be transmitted by biological vectors. Virions of PlAMV are quite stable and it can be transmitted efficiently by mechanical contact.Disease symptomsPlAMV causes red‐rusted systemic necrosis in ornamental lilies, but it shows much weaker, if any, symptoms in wild plants such as P. asiatica.ControlControl of the disease caused by PlAMV is based mainly on rapid diagnosis and elimination of the infected bulbs or plants. 相似文献