全文获取类型
收费全文 | 3432篇 |
免费 | 276篇 |
国内免费 | 2篇 |
出版年
2022年 | 16篇 |
2021年 | 40篇 |
2020年 | 32篇 |
2019年 | 34篇 |
2018年 | 39篇 |
2017年 | 31篇 |
2016年 | 70篇 |
2015年 | 131篇 |
2014年 | 127篇 |
2013年 | 196篇 |
2012年 | 228篇 |
2011年 | 206篇 |
2010年 | 138篇 |
2009年 | 149篇 |
2008年 | 235篇 |
2007年 | 253篇 |
2006年 | 239篇 |
2005年 | 254篇 |
2004年 | 251篇 |
2003年 | 213篇 |
2002年 | 180篇 |
2001年 | 49篇 |
2000年 | 39篇 |
1999年 | 56篇 |
1998年 | 37篇 |
1997年 | 44篇 |
1996年 | 34篇 |
1995年 | 29篇 |
1994年 | 26篇 |
1993年 | 23篇 |
1992年 | 42篇 |
1991年 | 30篇 |
1990年 | 28篇 |
1989年 | 23篇 |
1988年 | 23篇 |
1987年 | 16篇 |
1986年 | 25篇 |
1985年 | 22篇 |
1984年 | 13篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 12篇 |
1980年 | 7篇 |
1979年 | 6篇 |
1978年 | 8篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1975年 | 5篇 |
1974年 | 5篇 |
1968年 | 5篇 |
排序方式: 共有3710条查询结果,搜索用时 250 毫秒
991.
992.
Osamu Takenaka Sakie Kawamoto Toshifumi Udono Minori Arakawa Hiroyuki Takasaki Akiko Takenaka 《Primates; journal of primatology》1993,34(3):357-363
Previously designed primers for the polymerase chain reaction (PCR) amplifying microsatellite DNA segments containing GT/AC
dinucleotide repeats in the chimpanzee (Pan troglodytes) genome were used for paternity testing in a breeding colony in captivity. Combinations of three PCR primers identified the
fathers of all the tested 40 chimpanzees born in an eight-year period. The results suggested: (1) a positive (though not conclusive)
correlation between male rank and number of offspring; (2) choice of mating partners by the female rather than by the male;
and (3) absence of stable mating pairs over the years. For studies of chimpanzees in captivity and in the wild, these primers
should be useful for paternity testing, for investigating genetic variations, and for improving genetic maintenance of breeding
colonies. 相似文献
993.
Six neural elements, viz., retinular axons, a giant monopolar axon, straight descending processes (type I), lamina monopolar axons (type II), processes containing clusters of dense-core vesicles (type III), and processes coursing in various directions with varicosities (type IV), have been identified at the ultrastructural level in the lamina neuropil of the larval tiger beetle Cicindela chinensis. Retinular axons make presynaptic contact with all other types of processes. Type I and II processes possess many pre-and postsynaptic loci. Type II processes presumably constitute retinotopic afferent pathways. It remains uncertain whether type I processes are lamina monopolar axons or long retinular axons extending to the medullar neuropil. Type III processes may be efferent neurons or branches of afferent neurons contributing to local circuits. A giant monopolar axon extends many branches throughout the lamina neuropil; these branches are postsynaptic to retinular axons, and may be nonretinotopic and afferent. Type IV processes course obliquely in the neuropil, being postsynaptic to retinular axons, and presynaptic to type I processes. 相似文献
994.
The visual system of the larval tiger beetle (Cicindela chinensis) consists of six (two large, two mediumsized, and two small) stemmata on either side of the head, and an underlying neuropil mass. Each stemma exhibits a corneal lens and an underlying rhabdom layer. Retinular cells extend single proximal axons into the neuropil mass. The neuropil mass has a flattened heart-shape, and consists of two juxtaposed identical structures, each being a neuropil complex of each of the two large stemmata. The complex consists of lamina and medulla neuropils. Most retinular axons terminate in the lamina neuropil. Axons of two types of lamina monopolar neurons descend parallel to each other into the lamina neuropil. Moreover, each lamina neuropil contains a single giant monopolar neuron. Possible centrifugal processes and tangential neurons also occur. Lamina monopolar axons descend straight into the medulla neuropil. Medulla neurons spread fan-shaped dendrites distally in the medulla neuropil and send single axons toward the protocerebrum. These data are discussed with respecct to the unique visual behavior of this larva and in comparison with other insect visual systems. 相似文献
995.
Masato Shibuya 《Ecological Research》1994,9(3):325-332
The competition-density effect for natural Japanese white bitch (Betula platyphylla var.japonica) stands, located in the northern part of Hokkaido Island, was examined for various growth stages to establish mean tree weight-density
relationships over a considerable extent of stand growth of white birch. Aboveground yields of investigated stands ranged
from 16.0 to 161.7 t·ha−1, and it was recognized that maximum aboveground yield of this species was about 160 t·ha−1. ConstantsA andB of the reciprocal equation of the C-D effect, 1/w=AN+B (w, mean tree weight; N, tree density), were related to mean height classes of birch stands. ConstantB was related to the entire mean height classes as the allometric relationship. On the other hand, constantA had an allometric relationship to mean height classes under 16 m, but became fixed over the 16 m class. White birch stands
can come up to the maximum yield approximately at the stage of the 16 m class. The asymptotic tendency seemed to be appropriate
for constantA-mean height class relationship. The maximum yield of white birch stands was predicted by the asymptotic value ofA. The trend of mean tree weight-density relationships with stand growth also changed with constantA. It was considered that maximum yield was an important characteristic for practical applications of the C-D effect to agriculture
and forestry. 相似文献
996.
997.
Monellin, a sweet protein, consists of two noncovalently associated polypeptide chains: an A chain of 44 amino acid residues and a B chain of 50 residues. Microbial transglutaminase (MTGase) was used for ligation of the monellin subunits without any protecting groups, and without activation of the Cα‐carboxyl group at the C‐terminus. Since a peptide fragment LLQG is a good substrate for MTGase to form an amide bond between the γ‐amide group of the Gln residue and the ε‐amino group of Lys, a monellin B chain analogue in which LLQG was elongated at the C‐terminus (B‐LLQG) was synthesized by solid‐phase synthesis. The monellin A chain analogue in which KGK was elongated at the N‐terminus (KGK‐A) was synthesized by the same method as that of the B chain analogue. The KGK‐A chain and the B‐LLQG chain were coupled by MTGase to give single‐chain analogue of monellin. The single‐chain analogue of monellin was characterized by analytical reverse phase high performance liquid chromatography, electrospray ionization, and amino acid analyses. All analyses gave satisfactory results. The single‐chain analogue of monellin was more heat stable than natural monellin. © 1999 John Wiley & Sons, Inc. Biopoly 50: 193–200, 1999 相似文献
998.
The herbaceous perennial Cirsium purpuratum is a pioneer on the southeast side of Mount Fuji in Japan. For genetic analysis of reproduction in this species, we developed polymorphic compound microsatellite markers using an adaptor-ligated library method and a simpler method called the intercompound microsatellite method. The latter method was an effective method for developing compound simple sequence repeat markers. In total, 11 polymorphic, codominant microsatellite markers were developed and characterized for this species. These polymorphic markers had three to 20 alleles per locus, a range of observed heterozygosity from 0.25 to 0.90, and were considered effective for genetic analysis. 相似文献
999.
1000.
Asami Kawasaki Akiko Sakai Hiroki Nakanishi Junya Hasegawa Tomohiko Taguchi Junko Sasaki Hiroyuki Arai Takehiko Sasaki Michihiro Igarashi Fubito Nakatsu 《The Journal of cell biology》2022,221(1)
Membrane contact sites (MCSs) serve as a zone for nonvesicular lipid transport by oxysterol-binding protein (OSBP)-related proteins (ORPs). ORPs mediate lipid countertransport, in which two distinct lipids are transported counterdirectionally. How such lipid countertransport controls specific biological functions, however, remains elusive. We report that lipid countertransport by ORP10 at ER–endosome MCSs regulates retrograde membrane trafficking. ORP10, together with ORP9 and VAP, formed ER–endosome MCSs in a phosphatidylinositol 4-phosphate (PI4P)-dependent manner. ORP10 exhibited a lipid exchange activity toward its ligands, PI4P and phosphatidylserine (PS), between liposomes in vitro, and between the ER and endosomes in situ. Cell biological analysis demonstrated that ORP10 supplies a pool of PS from the ER, in exchange for PI4P, to endosomes where the PS-binding protein EHD1 is recruited to facilitate endosome fission. Our study highlights a novel lipid exchange at ER–endosome MCSs as a nonenzymatic PI4P-to-PS conversion mechanism that organizes membrane remodeling during retrograde membrane trafficking. 相似文献