全文获取类型
收费全文 | 2982篇 |
免费 | 234篇 |
国内免费 | 157篇 |
出版年
2023年 | 35篇 |
2022年 | 32篇 |
2021年 | 61篇 |
2020年 | 71篇 |
2019年 | 84篇 |
2018年 | 79篇 |
2017年 | 67篇 |
2016年 | 99篇 |
2015年 | 113篇 |
2014年 | 116篇 |
2013年 | 206篇 |
2012年 | 99篇 |
2011年 | 125篇 |
2010年 | 104篇 |
2009年 | 157篇 |
2008年 | 141篇 |
2007年 | 171篇 |
2006年 | 144篇 |
2005年 | 149篇 |
2004年 | 143篇 |
2003年 | 110篇 |
2002年 | 100篇 |
2001年 | 77篇 |
2000年 | 97篇 |
1999年 | 74篇 |
1998年 | 81篇 |
1997年 | 58篇 |
1996年 | 56篇 |
1995年 | 59篇 |
1994年 | 56篇 |
1993年 | 52篇 |
1992年 | 47篇 |
1991年 | 42篇 |
1990年 | 35篇 |
1989年 | 41篇 |
1988年 | 26篇 |
1987年 | 25篇 |
1986年 | 21篇 |
1985年 | 28篇 |
1984年 | 22篇 |
1983年 | 11篇 |
1982年 | 14篇 |
1981年 | 11篇 |
1980年 | 9篇 |
1979年 | 8篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1973年 | 1篇 |
1972年 | 2篇 |
排序方式: 共有3373条查询结果,搜索用时 15 毫秒
991.
Another functional frame‐shift polymorphism of DEFB126 (rs11467497) associated with male infertility 下载免费PDF全文
Shiwei Duan Changgeng Shi Guowu Chen Ju‐fen Zheng Bin Wu Hua Diao Lindan Ji Yihua Gu Aijie Xin Yancheng Wu Weijin Zhou Maohua Miao Limin Xu Zheng Li Yao Yuan Peng Wang Huijuan Shi 《Journal of cellular and molecular medicine》2015,19(5):1077-1084
DEFB126 rs140685149 mutation was shown to cause sperm dysfunction and subfertility. Indel rs11467497 is another 4‐nucleotide frame‐shift mutation (151bp upstream of rs140685149) that leads to the premature termination of translation and the expression of peptide truncated at the carboxyl terminus. In the present study, we performed a comprehensive association study to check the contribution of rs140685149 and rs11467497 to male infertility. Our results confirmed the previous findings that there was no association between rs140685149 and sperm motility. In contrast, we found a significant association of another indel rs11467497 with male infertility. Moreover, rs11467497 was shown to be associated with higher number of round cells in the infertile males with low sperm motility. Surprisingly, the two mutations commonly existed in the sperm donors (n = 672), suggesting a potential application of the two indels in the screening for eligible sperm donors. Western blotting assays showed the sperms with rs140685149 2‐nt deletion tended to have unstable DEFB126 protein in contrast of no DEFB126 protein expressed in the sperms with rs11467497 4‐nt deletion, suggesting a more severe consequence caused by rs11467497 mutation. In conclusion, our study presented a significant contribution of another functional frame‐shift polymorphism of DEFB126 (rs11467497) to male infertility. 相似文献
992.
In many species, males rely on sexual ornaments to attract females. Females, by contrast, rarely produce ornaments. The glow-worm (Lampyris noctiluca) is an exception where wingless females glow to attract males that fly in search of females. However, little is known about the factors that promote the evolution of female ornaments in a sexual selection context. Here, we investigated if the female ornament of the glow-worm is a signal of fecundity used in male mate choice. In support of this, we found brightness to correlate with female fecundity, and males to prefer brighter dummy females. Thus, the glow emitted by females is a reliable sexual signal of female fecundity. It is likely that male preference for the fecundity-indicating ornament has evolved because of large variation among females in fecundity, and because nocturnal males cannot directly assess female size and fecundity. These results indicate that female ornamentation may evolve in capital breeders (i.e. those in which stored resources are invested in reproduction) when females vary significantly in fecundity and this variation cannot be assessed directly by males. 相似文献
993.
994.
Hong-wei CHEN Masanori J. TODA Maklarin B. LAKIM Maryati Bte MOHAMED 《Entomological Science》2007,10(1):73-80
Eight species of the Amiota sinuata species group are reported from eastern Malaysia, including six new species, A. bispinula, A. cerata, A. curvibacula, A. lambirensis, A. parviserrata and A. quadrifoliolata spp. nov. A key to Asian species of the group is provided. 相似文献
995.
Changes in serum concentrations of two androgens, testosterone (T) and 11‐ketotestosterone (11KT), and oestradiol‐17β(E2) in male and female giant sturgeon Huso huso , Russian sturgeon Acipenser gueldenstaedtii and stellate sturgeon Acipenser stellatus were studied at different stages of gonadal maturity and after final maturation induced by hormonal treatment. Both male and female fish displayed a distinct increase in serum steroid concentrations during gonadal development. 11KT levels were significantly higher in males than females, with a positive correlation detected between 11KT and T concentrations. In maturing males and females, higher values of both 11KT and T were observed in stellate sturgeon compared to giant and Russian sturgeons. Vitellogenesis and high E2 levels were correlated in maturing sturgeon females. 相似文献
996.
Do juvenile felons suffer nightmares? Can dreamwork be useful with this population? After a review of the generally older and limited literature on these issues, 2 new surveys and several case examples give positive answers to these questions. In Study 1, 50 of 100 adolescent male felons reported dreams and 12 reported nightmares. In Study 2, with the addition of a follow-up prompt, 73 of 100 adolescent male felons reported dreams within the prior month and 13 reported nightmares. Seven case examples illustrate verbal interventions for nightmares, and 5 case examples illustrate benefits youths could derive from dreamwork. Suggestions for further research are given. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
997.
Hatchery-reared mature male Atlantic salmon parr were shorter than immature parr of the same age through the winter period and this difference increased prior to smolting in spring. Stripping had no effect on growth. In autumn mature male parr had a higher condition factor (CF) than immature parr, but from early January no difference was observed between unstripped mature males and immature parr. Stripping reduced the CF of male parr but the difference had disappeared by the time of smolting when the CFs of both mature groups were lower than that of immature fish. The quantity of expressible milt in stripped males decreased from c . 3% body weight in November and December to <0.05% by 2 March, after which no further milt expression was recorded. Milt expression in previously unstripped males was about 1% of body weight on 2 March, similar to that of stripped males 1 month earlier. 相似文献
998.
In male sand smelt Atherina boyeri , from three coastal brackish lagoons of southern France, the duration of the reproductive season differed according to fish size: larger fish exhibited an extended reproductive season from February to August while smaller males reproduced only from April to June-July. Smaller and larger fish showed differences in their seasonal pattern of reserves. Through the cold season, energy content was exhausted for over-winter maintenance and reproductive needs, and was restored just after fish ceased reproducing. In smaller fish, however, reserves were more rapidly restored than in larger fish, and exhibited a decrease in autumn. This result suggested that small fish invested their energy into growth and winter survival rather than reproduction while older fish invested in reproduction. These results are discussed in terms of life history Strategies. 相似文献
999.
雌雄同居是配偶关系形成的重要阶段,涉及到一系列生理和情绪的变化,对长期稳定的配偶关系形成具有重要意义。然而由于单配制动物模型较少,雌雄同居过程中的神经调控,尤其是两性差异仍不清楚。本研究以室内繁殖的子午沙鼠(Meriones meridianus)为研究对象,采用高架十字迷宫、强迫游泳和免疫组化法,探究雌雄同居对雌雄子午沙鼠的情绪变化及其相关脑区催产素表达的影响。结果表明:雌雄同居10 d后,在高架十字迷宫中,雌性沙鼠进入开放臂的频次显著减少(P <0.05),焦虑指数显著升高(P <0.05);在强迫游泳实验中,同居组雌性沙鼠停止游泳的频次和时间显著增加(P <0.05);同居组雌性沙鼠在下丘脑室旁核和视上核中的催产素表达水平显著升高(P <0.05)。然而同居组雄性的行为和催产素水平均没有出现显著变化,这可能与雌雄配偶关系形成过程中的两性不同步有关。综上,雌雄同居仅使得雌性子午沙鼠表现出焦虑样行为,且下丘脑催产素系统可能参与了该过程。 相似文献
1000.
CRISPR/Cas9-targeted mutagenesis of TaDCL4, TaDCL5 and TaRDR6 induces male sterility in common wheat
Rongzhi Zhang Shujuan Zhang Jihu Li Jie Gao Guoqi Song Wei Li Shuaifeng Geng Cheng Liu Yanxiang Lin Yulian Li Genying Li 《Plant biotechnology journal》2023,21(4):839-853
Phased, small interfering RNAs (phasiRNAs) are important for plant anther development, especially for male sterility. PhasiRNA biogenesis is dependent on genes like RNA polymerase 6 (RDR6), DICER-LIKE 4 (DCL4), or DCL5 to produce 21- or 24 nucleotide (nt) double-strand small RNAs. Here, we generated mutants of DCL4, DCL5 and RDR6 using CRISPR/Cas9 system and studied their effects on plant reproductive development and phasiRNA production in wheat. We found that RDR6 mutation caused sever consequence throughout plant development starting from seed germination and the dcl4 mutants grew weaker with thorough male sterility, while dcl5 plants developed normally but exhibited male sterility. Correspondingly, DCL4 and DCL5, respectively, specified 21- and 24-nt phasiRNA biogenesis, while RDR6 contributed to both. Also, the three key genes evolved differently in wheat, with TaDCL5-A/B becoming non-functioning and TaRDR6-A being lost after polyploidization. Furthermore, we found that PHAS genes (phasiRNA precursors) identified via phasiRNAs diverged rapidly among sub-genomes of polyploid wheat. Despite no similarity being found among phasiRNAs of grasses, their targets were enriched for similar biological functions. In light of the important roles of phasiRNA pathways in gametophyte development, genetic dissection of the function of key genes may help generate male sterile lines suitable for hybrid wheat breeding. 相似文献