全文获取类型
收费全文 | 596篇 |
免费 | 80篇 |
专业分类
676篇 |
出版年
2022年 | 7篇 |
2021年 | 20篇 |
2020年 | 11篇 |
2019年 | 6篇 |
2018年 | 14篇 |
2017年 | 11篇 |
2016年 | 13篇 |
2015年 | 27篇 |
2014年 | 24篇 |
2013年 | 31篇 |
2012年 | 59篇 |
2011年 | 39篇 |
2010年 | 32篇 |
2009年 | 29篇 |
2008年 | 39篇 |
2007年 | 32篇 |
2006年 | 30篇 |
2005年 | 30篇 |
2004年 | 29篇 |
2003年 | 33篇 |
2002年 | 32篇 |
2001年 | 9篇 |
2000年 | 10篇 |
1999年 | 16篇 |
1998年 | 9篇 |
1997年 | 9篇 |
1995年 | 7篇 |
1994年 | 3篇 |
1993年 | 6篇 |
1992年 | 9篇 |
1991年 | 3篇 |
1990年 | 5篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1970年 | 2篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1966年 | 2篇 |
1964年 | 1篇 |
1961年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有676条查询结果,搜索用时 0 毫秒
1.
2.
Barbara Tillmann Pierre Jolic?ur Masami Ishihara Nathalie Gosselin Olivier Bertrand Yves Rossetti Isabelle Peretz 《PloS one》2010,5(4)
Congenital amusia is a neurogenetic disorder of music processing that is currently ascribed to a deficit in pitch processing. A recent study challenges this view and claims the disorder might arise as a consequence of a general spatial-processing deficit. Here, we assessed spatial processing abilities in two independent samples of individuals with congenital amusia by using line bisection tasks (Experiment 1) and a mental rotation task (Experiment 2). Both amusics and controls showed the classical spatial effects on bisection performance and on mental rotation performance, and amusics and controls did not differ from each other. These results indicate that the neurocognitive impairment of congenital amusia does not affect the processing of space. 相似文献
3.
Recombinant plasmid pCED3 was structurally unstable inBacillus subtilis cultures grown in the presence of kanamycin to eliminate the effects of segregational instability. Analysis of 96 modified plasmids indicated that deletions in the plasmid occur at many different sites. The presence of plasmid pCED3 slowed the growth rate of theB. subtilis host. Cells that contained modified plasmids grew faster than the parental cells and took over the population. Two different methodologies were developed to reduce the cultural instability of the plasmid-directed LacZ+ phenotype. By growing the cells in a medium that supports a low growth rate, the growth rate ratio between modified and parental cells was reduced, resulting in a partial stabilization (40 generations) of the LacZ+ phenotype in the population [35]. Removal of a 4.77 kbEcoRI fragment (which consists primarily of the pBR322 replicon) from plasmid pCED3 produced a more stable plasmid derivative, designated pYS1. Cells harboring plasmid pYS1 grew faster than pCED3-bearing cells, although the level of activity of -galactosidase was similar in both strains. By combining the two approaches (i.e., growth of pYS1-bearing cells in a medium that supports low growth rate), the LacZ+ phenotype was stably maintained in the cell population for over 170 generations. Under these conditions, there was no detectable difference between the growth rates of cells bearing the pYS1 plasmid and further modified plasmids. 相似文献
4.
To analyze the sexual behavior of male black-legged deer ticks Ixodes dammini,we collected ticks infesting 202 white-tailed deer. On average, 17.7 males and 8.8 females infested each deer. Field-collected males copulated with a mean of 2.25 females, and virgin males mated with 2.4 females. On experimental hosts, males established sexual contact with feeding females and repelled other males, and about half remained paired after their mate detached. Engorged females continue to be receptive, and males mate more readily with them than with nonfed females. We conclude that male I. damminiare endowed with a repertoire of behaviors which favor an opportunistic mating before seeking a host and a preference for mating with feeding females on the host accompanied by tenacious mate guarding. 相似文献
5.
The wake and sleep-onset times of a patient with a sleep-wake cycle longer than 24 hr were recorded by the patient for 4 years. During this time, the patient found himself unable to maintain a 24-hr sleep-wake schedule. When treated with 1-2 mg clonazepam, taken nightly, he was able to become entrained to a 24-hr day. Despite entrainment of his sleep-wake cycle, the patient reported depression, lack of motivation and fatigue and chose not to continue taking the drug. 相似文献
6.
7.
N. B. Cherfas Y. Peretz N. Ben-Dom B. Gomelsky G. Hulata 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1994,89(2-3):281-286
The results of a series of experiments conducted in our laboratory on the ornamental common carp (koi), aimed at optimizing heat-shock chromosome-set manipulation procedures, are described. The timing of heat-shock initiation was expressed in the relative unit of embryological age (0) in order to standardize this parameter, the absolute time for heat-shock initiation being calculated from duration of one 0 at two different pre-treatment water temperatures. Heat shocks were applied within the periods of 0.05–0.60 0 and 1.20–2.20 0 which, respectively, cover the successive phases of the 2nd meiotic division and the 1st cleavage. The highest production of diploid gynogenetic offspring was observed when heat shocks were initiated at 0.15–0.25 0 and at 1.5 0, after insemination, corresponding to anaphase of meiosis-II, and metaphase of the 1st cleavage, respectively. Similar results were obtained irrespective of the different pre-treatment water temperatures, thus confirming the possibility of standardizing heat-shock timing by 0. 相似文献
8.
Yuval Cohen Vaishali P. Chitnis Rachel Nechushtai Parag R. Chitnis 《Plant molecular biology》1993,23(4):895-900
We studied assembly of the PsaE subunit of photosystem I into photosynthetic membranes of cyanobacterial mutant strains that lack specific photosystem I subunits. Radiolabeled PsaE was incubated with photosynthetic membranes, and their binding and assembly were assayed by resistance to removal by chaotropic agents and proteolytic digestion. PsaE incorporated into the wild-type membranes was resistant to these treatments. In the absence of PsaD, it was resistant to proteolytic digestion, but was removed by NaBr. When the membranes were isolated from a mutant strain in which the psaF and psaJ genes have been inactivated, PsaE assembled in vitro could not be removed. PsaE could associate with the membranes of the strain DF in which the psaD, psaJ and psaF genes have been mutated. However, the radiolabeled PsaE associated with these membranes was removed both by the proteolytic as well as by the chaotropic agents. Characterization of PsaE present in vivo revealed similar results. These observations suggest that PsaD and PsaF/J may interact with PsaE and stabilize it in the photosystem I complex. 相似文献
9.
10.
In a search for genes that are induced in citrus cell suspension in response to salt stress, a cDNA clone with high homology to cotton Lea5 gene was isolated. Data base analysis of the protein deduced from the nucleotide sequence indicates that, like in cotton, the protein from citrus contains regions with significant hydropathic character. The gene, designated C-Lea5, is expressed in citrus leaves as well as cell suspension. The steady-state level of C-Lea5 is increased in cell suspension that is grown in the presence of 0.2 M NaCl. This phenomenon is also observed in leaves of citrus plants irrigated with NaCl and in citrus seedlings which are exposed to drought and heat stress. We suggest that the osmotic stress resulted from elevated level of salt is responsible for the increase in the level of C-Lea5. 相似文献