全文获取类型
收费全文 | 4551篇 |
免费 | 392篇 |
国内免费 | 443篇 |
出版年
2024年 | 4篇 |
2023年 | 67篇 |
2022年 | 86篇 |
2021年 | 224篇 |
2020年 | 165篇 |
2019年 | 256篇 |
2018年 | 208篇 |
2017年 | 156篇 |
2016年 | 194篇 |
2015年 | 319篇 |
2014年 | 360篇 |
2013年 | 355篇 |
2012年 | 437篇 |
2011年 | 445篇 |
2010年 | 248篇 |
2009年 | 192篇 |
2008年 | 220篇 |
2007年 | 211篇 |
2006年 | 197篇 |
2005年 | 159篇 |
2004年 | 127篇 |
2003年 | 109篇 |
2002年 | 88篇 |
2001年 | 78篇 |
2000年 | 44篇 |
1999年 | 56篇 |
1998年 | 41篇 |
1997年 | 47篇 |
1996年 | 44篇 |
1995年 | 29篇 |
1994年 | 36篇 |
1993年 | 17篇 |
1992年 | 27篇 |
1991年 | 22篇 |
1990年 | 16篇 |
1989年 | 12篇 |
1988年 | 11篇 |
1987年 | 14篇 |
1986年 | 7篇 |
1985年 | 19篇 |
1983年 | 2篇 |
1980年 | 2篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1972年 | 6篇 |
1971年 | 5篇 |
1970年 | 2篇 |
1967年 | 2篇 |
排序方式: 共有5386条查询结果,搜索用时 308 毫秒
991.
为了实现心肌营养素 - 1 ( CT- 1 )的高效与可溶性表达 ,将 CT- 1基因分别插入到 3种大肠杆菌表达载体 p BV2 2 0、p GEX- 2 T和 p Trx FUS中 ,并实现了表达 ,全菌表达水平分别为 2 .6%、1 6%和 2 5 %。其中 ,CT- 1在 p Trx FUS表达载体中以包含体和可溶性两种方式表达 ,表达水平分别为2 0 .8%和 1 0 .7%。可溶性表达部分经过强阴离子交换和凝胶过滤两步纯化 ,纯度达 80 %以上 相似文献
992.
Allozyme variation at eleven loci encoding seven enzyme systems were examined in 20 populations of diploid (genome AA, 2n = 16)Scilla scilloides in China. In comparison with the average species of seed plants studied, populations of this species display a high amount of genetic variation (A = 2.0, P = 58.6%, Ho = 0.172, and He = 0.185). Allozyme variation pattern revealed predominant outcrossing within populations and considerable differentiation (FST = 0.314) among populations as well as between the subtropic and temperate regions. The wide distribution, long existence and outcrossing are presumably the main factors responsible for the high genetic diversity within populations. But the gravity dispersal of seeds and pollination by small insects set limits to the increase of genetic variation within populations and promote differentiation between populations and regions. In addition, allozyme variation does not distinguishS. scilloides var.albo-viridis and suggests that subtropic populations may be considered as a genetic entity. 相似文献
993.
对榆梨绵蚜Eriosoma lanuginosum dilanuginosum Zhang,1980的干母,无翅干雌,有翅干雌,无翅侨蚜,有翅性母,雌,雄性蚜放卵进行了描述,除有翅干雌外,其余各型与卵均为首镒记述。所有研究用标本均保存在中国科学院动物研究所昆虫标本馆内。 相似文献
994.
995.
S R Li D P Wang X L Yu B S Ge C E Wang Y F Lu J Q Li N Wu R F Li S E Zhu Z C Zhang Y F Chen 《Genetical research》1999,73(3):233-238
A pair of mutant mice with a first sparse coat appeared spontaneously in the production stock of BALB/c mice with a normal coat. After being sib-mated, they produced three phenotypes in their progeny: mice with normal hair, mice with a first sparse coat and then a fuzzy coat, and uncovered mice. Genetic studies revealed the mutants had inherited an autosomal monogene that was semi-dominant. By using 11 biochemical loci--Idh, Car2, Mup1, Pgm1, Hbb, Es1, Es10, Gdc, Ce2, Mod1 and Es3--as genetic markers, two-point linkage tests were made. The results showed the gene was assigned to chromosome 11. The result of a three-point test with Es3 and D11Mit8 (microsatellite DNA) as markers showed that the mutation was linked to Es3 with the recombination fraction 7.89 +/- 2.19%, and linked to D11Mit8 with the recombination fraction 26.30 +/- 3.57%. The recombination fraction between Es3 and D11Mit8 was 32.90 +/- 3.81%. It is suggested that the mutation is a new genetic locus that affected the skin and hair structure of the mouse. The mutation was named uncovered, with the symbol Uncv. Further studies showed the mutation affected not only the histology of skin and hair but also the growth and reproductive performance of the mice. The molecular characterization of the Uncv locus needs to be further studied. 相似文献
996.
997.
Phenotypic plasticity is the environmental modification of genotypic expression
and an important means by which individual plants respond to environmental heterogeneity.
The study of phenotypic plasticity in the genus Adenophora, which is very complicated taxo nomically because of great morphological variation, proves to be helpful in both investigating
the phenotypic variation so as to evaluate potential taxonomic value of their characters and
providing important sources of information on the variation, adaptation and evolution of the
genus. Twenty-three populations representing all the six species in Adenophora potaninii
complex were transplanted into the garden. Of them six populations were selected for study ing their performance in the field and in the garden, in addition to cultivation experiment
under different treatments. The results show that there exists considerable developmental
plasticity in some leaf, floral and capsule characters. In particular, the leaf shape and length
of calyx lobe display significant developmental variation with the maximum being three times
as great as the minimum, which is noteworthy because they were previously considered as
diagnostic. The characters of root, caudex, stem and inflorescence are found to be very
plastic, especially the root diameter, the number of stems, stem height and inflorescence
length with great environmental plasticity. In addition, the populations from different habi tats show distinct amounts of plasticity. On the contrary, the characters of leaf, floral, cap sule and seed are less influenced by environments. It seems that the considerable variation in
the characters of leaf is attributed mainly to genetic differences. Finally, the phenotypic
plasticity of morphological characters of A. potaninii complex and its taxonomic significanceis discussed. 相似文献
998.
我国有罂粟属植物12种,新疆有10种,其中6种属于高山罂粟组。对新疆高山罂粟组植物的花葶进行了解剖研究,并用扫描电镜观察了花粉形态,结果表明,花葶中维管束的数量及排列方式在各种间存在着差异,可以作为一个鉴定特征。花粉上的小刺密度在放大12000倍时,在有种间存在着明显差异,可分类提供微观佐证。 相似文献
1000.
Yong Ge Tao Ling Yao Wang Xin Jia Xiongmei Xie Rong Chen Shangwu Chen Shaochun Yuan Anlong Xu 《EMBO reports》2021,22(11)
N 6‐methyladenosine (m6A) is a chemical modification present in multiple RNA species and is most abundant in mRNAs. Studies on m6A reveal its comprehensive roles in almost every aspect of mRNA metabolism, as well as in a variety of physiological processes. Although some recent discoveries indicate that m6A can affect the life cycles of numerous viruses as well as the cellular antiviral immune response, the roles of m6A modification in type I interferon (IFN‐I) signaling are still largely unknown. Here, we reveal that WT1‐associated protein (WTAP), one of the m6A “writers”, is degraded via the ubiquitination‐proteasome pathway upon activation of IFN‐I signaling. With the degradation of WTAP, the m6A levels of IFN‐regulatory factor 3 (IRF3) and interferon alpha/beta receptor subunit 1 (IFNAR1) mRNAs are reduced, leading to translational suppression of IRF3 and instability of IFNAR1 mRNA. Thus, the WTAP‐IRF3/IFNAR1 axis may serve as negative feedback pathway to fine‐tune the activation of IFN‐I signaling, which highlights the roles of m6A in the antiviral response by dictating the fate of mRNAs associated with IFN‐I signaling. 相似文献