全文获取类型
收费全文 | 2093篇 |
免费 | 102篇 |
国内免费 | 135篇 |
出版年
2024年 | 2篇 |
2023年 | 29篇 |
2022年 | 51篇 |
2021年 | 56篇 |
2020年 | 41篇 |
2019年 | 51篇 |
2018年 | 64篇 |
2017年 | 47篇 |
2016年 | 58篇 |
2015年 | 70篇 |
2014年 | 101篇 |
2013年 | 119篇 |
2012年 | 85篇 |
2011年 | 69篇 |
2010年 | 96篇 |
2009年 | 121篇 |
2008年 | 115篇 |
2007年 | 95篇 |
2006年 | 72篇 |
2005年 | 79篇 |
2004年 | 72篇 |
2003年 | 76篇 |
2002年 | 66篇 |
2001年 | 73篇 |
2000年 | 50篇 |
1999年 | 55篇 |
1998年 | 53篇 |
1997年 | 45篇 |
1996年 | 43篇 |
1995年 | 32篇 |
1994年 | 31篇 |
1993年 | 40篇 |
1992年 | 37篇 |
1991年 | 43篇 |
1990年 | 32篇 |
1989年 | 14篇 |
1988年 | 16篇 |
1987年 | 13篇 |
1986年 | 15篇 |
1985年 | 16篇 |
1984年 | 13篇 |
1983年 | 11篇 |
1982年 | 12篇 |
1981年 | 10篇 |
1980年 | 12篇 |
1979年 | 12篇 |
1977年 | 2篇 |
1976年 | 6篇 |
1975年 | 2篇 |
1972年 | 2篇 |
排序方式: 共有2330条查询结果,搜索用时 15 毫秒
1.
The lagena (the third otolith endorgan in vertebrates) 总被引:1,自引:1,他引:0
V. I. Khorevin 《Neurophysiology》2008,40(2):142-159
In this review, the structure and functions of the lagena (the third otolith organ) in an evolutionary lineage of the vertebrates
are described and discussed. The lagenar macula appears first in the posterior part of the sacculus of elasmobranchs; in these
animals, the lagena is considered to be involved in the balance support (orientation with respect to the gravitation force).
The lagena as a separate endorgan has been described in teleost fishes; in some species, the lagena is connected with the
sacculus, while in other species the interrelations of these structures can be dissimilar. The lagena supplements the functions
of the sacculus; in fishes (animals with no special organ of hearing), it is involved in discrimination of sound oscillations,
identification of the gravitation vector, and orientation in the course of movements within the vertical plane. In amphibians,
the lagena is localized in the posterior part of the sacculus, near the auditory structures; it performs mostly vestibular
and (to a much lesser extent) auditory functions. In amniotes, the lagena was first separated from the sacculus; it is localized
in the cochlear canal, distally with respect to the hearing organ. Information on the functions of the lagena in amniotes
is rather limited and contradictory. Central projections of this organ have been examined practically only in birds. Lagenar
afferents project to the vestibular nuclei and cerebellum, while some fibers come to the auditory nuclei of the medulla. The
lagena in birds can be related to their navigation abilities (birds are supposed to be capable of orienting within the magnetic
field of the Earth due to the magnetic properties of the lagenar otoconia; this structure can also provide detection of movements
along the vertical axis. The close proximity between the otolithic and auditory endorgans in the cochlear canal of amniotes
can be indicative of the functional significance of these interrelations. This aspect, however, remains at present undiscovered.
In mammals (except Monotremata), there is no lagena as an independent endorgan.
Neirofiziologiya/Neurophysiology, Vol. 40, No. 2, pp. 160–178, March–April, 2008. 相似文献
2.
A Merlin W Voos A C Maarse M Meijer N Pfanner J Rassow 《The Journal of cell biology》1999,145(5):961-972
Tim44 is a protein of the mitochondrial inner membrane and serves as an adaptor protein for mtHsp70 that drives the import of preproteins in an ATP-dependent manner. In this study we have modified the interaction of Tim44 with mtHsp70 and characterized the consequences for protein translocation. By deletion of an 18-residue segment of Tim44 with limited similarity to J-proteins, the binding of Tim44 to mtHsp70 was weakened. We found that in the yeast Saccharomyces cerevisiae the deletion of this segment is lethal. To investigate the role of the 18-residue segment, we expressed Tim44Delta18 in addition to the endogenous wild-type Tim44. Tim44Delta18 is correctly targeted to mitochondria and assembles in the inner membrane import site. The coexpression of Tim44Delta18 together with wild-type Tim44, however, does not stimulate protein import, but reduces its efficiency. In particular, the promotion of unfolding of preproteins during translocation is inhibited. mtHsp70 is still able to bind to Tim44Delta18 in an ATP-regulated manner, but the efficiency of interaction is reduced. These results suggest that the J-related segment of Tim44 is needed for productive interaction with mtHsp70. The efficient cooperation of mtHsp70 with Tim44 facilitates the translocation of loosely folded preproteins and plays a crucial role in the import of preproteins which contain a tightly folded domain. 相似文献
3.
Nile tilapia (Oreochromis niloticus) is one of the most widespread invasive fish species, and this species has successfully established populations in the major rivers of Guangdong Province, China. Field surveys and manipulative experiments were conducted to assess the impacts of Nile tilapia on fisheries. We determined that the increase of Nile tilapia in these rivers not only affects the CPUE (catch-per-unit-per-effort) of the fish community and native fish species but also reduces the income of fishermen. In the manipulative experiments, we observed that the growth of native mud carp decreased in the presence of Nile tilapia. Our results suggest that the invasion of Nile tilapia negatively affected the fishery economy and native fish species, and suitable control measurements should be taken. 相似文献
4.
The effect of long-term (77 day) exposure of carp Cyprinus carpio to low concentrations of waterborne iron (1 mg Fe-dextran l−1 ) on accumulation and cellular distribution of iron in the liver was assessed using Perl's staining and histological observations and morphometric measurements. Accumulation of iron in the liver occurred after 14 days of exposure, when the majority of the iron was found in the sinusoidal endothelium with lower amounts in the cytoplasm and nuclei of hepatocytes. Upon further treatment the iron was predominantly distributed in the cytoplasm of the hepatocytes either as granules or diffusive iron and in macrophages. 相似文献
5.
Influence of Hydrocortisone on Chick Embryo Retina Development 总被引:1,自引:1,他引:0
Renza Vento Giuseppina D'Ancona Michela Giuliano Gennaro Taibi Giovanni Tesoriere 《Journal of neurochemistry》1987,48(6):1693-1698
Treatment of chick embryos in ovo with hydrocortisone-21-phosphate (a single dose of 150 micrograms) caused a marked reduction of retinal thymidine kinase activity 24 h later. The inhibitory effect was highest (65-70%) in 8-10-day-old embryos and declined with age, disappearing after day 15. It was accompanied by a reduction in thickness of the retinal layers. Adrenocorticotropic hormone (ACTH) treatment (10 micrograms daily for 2 days) also produced an age-dependent inhibitory effect on retinal thymidine kinase, whereas treatment with a single dose of 200 micrograms of metopirone, a compound that prevents the 11 beta-hydroxylation of steroid molecules in the adrenal glands, impeded the decrease in thymidine kinase activity that normally occurs in chick embryo retina after day 9 of development. In addition, metopirone prevented the inhibition exerted by ACTH on thymidine kinase activity but had no effect on the action of hydrocortisone. 相似文献
6.
J. P. Infante 《Molecular and cellular biochemistry》1987,74(2):111-116
A critical review of the experimental literature concerning the metabolism of all-cis-4, 7, 10, 13, 16, 19-docosahexaenoate-containing phospholipids in muscle and retina suggests that it plays an essential role in maximizing the Ca2+/ATP stoichiometry of the Ca2+-ATPase of sarcoplasmic reticulum and retinal photoreceptor disks. Docosahexaenoate-phosphatidylcholine is proposed to participate in oligomerization of Ca2+-ATPase necessary for the establishment of a high Ca2+/ATP coupling ratio of the Ca2+ pump in these tissues. Possible tests of this hypothesis are presented. 相似文献
7.
Paul G. Layer Regina Alber Patrick Mansky Günter Vollmer Elmar Willbold 《Cell and tissue research》1990,259(2):187-198
Summary We report here that similar to E6-chicken retinal cells, dissociated cells from 5.5-day-old (E5.5) quail retinae reaggregate in rotary culture, multiply about tenfold and reestablish histotypical areas. These cellular aggregates include all nuclear layers either with inversed or correct laminar polarity, depending on the local origin of the cells (called rosetted and laminar in-vitro-retinae (IVR), respectively; Layer and Willbold 1989). In combined cultures, chick and quail cells are evenly mixed only during the first two days of culture. Along with the assembly of single cells into rosettes and then into discrete laminae, sectors of chick and quail cells begin to segregate. They are delineated by borders running radially through all three nuclear layers. Thus, interspecies migration of cells at this advanced stage of differentiation is strongly inhibited. Concomitant with this segregation, coherent radial columns spanning all three layers but containing cells from either species only, can be traced histologically. We conclude that a weak segregation of chick and quail retinal cells takes place already at the single cell level, but that the permanent segregation of entire tissue parts must be due to clonal cellular proliferation within the IVR in conjunction with some developmental-structural mechanism retaining clonal progenies within a columnar order.Abbreviations
ECM
extracellular matrix
-
E5.5
days of embryonic age
-
GCL
ganglion cell layer
-
GC's
ganglion cells
-
i.c.
in culture
-
INL
inner nuclear layer
- rosetted in-vitro-retina
retinal cell organoid aggregated from single cells of the central retina
-
IPL
inner plexiform layer
-
MRE
marginal retinal epithelium
-
ONL
outer nuclear layer
-
OPL
outer plexiform layer
-
OS
ora serrate
-
PR
photoreceptor cell
- laminated in-vitro-retina
fully laminated retinal cellorganoid resembling an E15-retina aggregated from cells of the eye periphery including RPE
-
RPE
retinal pigment epithelium 相似文献
8.
异育淇鲫及其双亲同工酶的比较研究 总被引:14,自引:0,他引:14
用4.5%聚丙烯酰胺凝胶平板电泳研究了异育淇鲫及其母本淇鲫和父本兴国红鲤的肌可溶性蛋白以及肾、肝、眼、背白肌和心等五种组织的乳酸脱氢酶(LDH)、苹果酸脱氢酶(MDH)和酯酶(EST)。结果发现:异育淇鲫的肌可溶性蛋白以及同工酶的电泳图谱与母本淇鲫相同而与父本兴国红鲤显著不同,因而认为异育淇鲫是淇鲫雌核发育的产物,父本基因对子代基本无影响。在此基础上,本文对异源精子在雌核发育中所起的生物学作用进行了初步探讨。 相似文献
9.
10.