全文获取类型
收费全文 | 23078篇 |
免费 | 1994篇 |
国内免费 | 1799篇 |
出版年
2024年 | 32篇 |
2023年 | 235篇 |
2022年 | 639篇 |
2021年 | 1214篇 |
2020年 | 765篇 |
2019年 | 944篇 |
2018年 | 954篇 |
2017年 | 764篇 |
2016年 | 957篇 |
2015年 | 1397篇 |
2014年 | 1644篇 |
2013年 | 1830篇 |
2012年 | 2104篇 |
2011年 | 1985篇 |
2010年 | 1237篇 |
2009年 | 1080篇 |
2008年 | 1266篇 |
2007年 | 1040篇 |
2006年 | 985篇 |
2005年 | 840篇 |
2004年 | 735篇 |
2003年 | 628篇 |
2002年 | 606篇 |
2001年 | 370篇 |
2000年 | 308篇 |
1999年 | 297篇 |
1998年 | 232篇 |
1997年 | 170篇 |
1996年 | 175篇 |
1995年 | 155篇 |
1994年 | 185篇 |
1993年 | 115篇 |
1992年 | 132篇 |
1991年 | 101篇 |
1990年 | 93篇 |
1989年 | 87篇 |
1988年 | 76篇 |
1987年 | 49篇 |
1986年 | 54篇 |
1985年 | 49篇 |
1984年 | 41篇 |
1983年 | 30篇 |
1982年 | 32篇 |
1981年 | 25篇 |
1980年 | 24篇 |
1979年 | 15篇 |
1978年 | 17篇 |
1976年 | 21篇 |
1975年 | 15篇 |
1974年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
31.
Shi Fenghua Tan Muxiu Mo Qiaocheng Chen Xiaoying Zhao Yimin Guo Xiaoyun Jiang Ni 《Journal of plant biochemistry and biotechnology.》2020,29(3):528-538
Journal of Plant Biochemistry and Biotechnology - The dried buds of Lonicera hypoglauca Miq. have antipyretic, antidotal and anti-inflammatory properties and as Flos lonicerae are widely used in... 相似文献
32.
Adaptation to hypoxia, defined as a condition of inadequate oxygen supply, has enabled humans to successfully colonize high altitude regions. The mechanisms attempted by organisms to cope with short-term hypoxia include increased ATP production via anaerobic respiration and stabilization of Hypoxia Inducible Factor 1α (HIF-1α). However, less is known about the means through which populations adapt to chronic hypoxia during the process of development within a life time or over generations. Here we show that signaling via the highly conserved Wnt pathway impacts the ability of Drosophila melanogaster to complete its life cycle under hypoxia. We identify this pathway through analyses of genome sequencing and gene expression of a Drosophila melanogaster population adapted over >180 generations to tolerate a concentration of 3.5–4% O2 in air. We then show that genetic activation of the Wnt canonical pathway leads to increased rates of adult eclosion in low O2. Our results indicate that a previously unsuspected major developmental pathway, Wnt, plays a significant role in hypoxia tolerance. 相似文献
33.
34.
35.
36.
Studies on the regeneration-restore and karyotype of protoplast in Metarhizium anisopliae var. majus
Abstract: The characteristics and regeneration-restore of protoplasts and its karyotype of an insect pathological fungus, Metarhizium anisopliae var. majus were studied. Among the protoplasts, 25.3% were without a nucleus, and 74.7% contained a nucleus. Among the nucleus protoplasts, 53.6% contained a single nucleus. The regeneration-restore of protoplasts was of three distinct shapes. Considering the frequency of regeneration and the growing speed of the colony, 0.7 mol/l glucose was the optimum as osmotic stabilizer of culture medium in the regeneration-restore of the protoplasts. The chromosomal DNA molecules of M. anisopliae var. majus have been separated into seven bands by pulsed-field gel electrophoreses. Using the Schizosaccharomyces pombe chromosomes as size standard, the size of chromosomal DNA was estimated to be 1.1–6.5 Mb and its karyotype exhibited polytypism among strains. 相似文献
37.
Pedigree analysis is a central component of many current efforts to locate genes that contribute to diseases or to valuable traits. The analysis usually involves solving one of two very computation-intense problems. We analyze the complexity of these two problems. Surprisingly, we show that both problems are NP-hard even for pedigrees that contain no inbreeding loops. 相似文献
38.
39.
V
H gene segments represent the products of the repeated duplication and subsequent diversification of a primordial V gene element. It is widely assumed that natural selection, operating via pathogens, has played the dominant role in this process. Here, we screen some 3.7 × 104 C
+
colonies of mitogen-activated B cells for the production of antibodies specific for phosphorylcholine or hen egg lysozyme and expression of the V
H X-24, S107, Q52, or J558 gene families. These gene families were expressed at frequencies proportional to their genomic complexity among both unselected and antigen-specific C
+
colonies. Thus, the capacity to encode equivalent antibody-combining sites is dispersed uniformly among V
Hfamilies. This result suggests that individual V
H genes have not evolved to address specific antigens. 相似文献
40.
Shi Liu Ron Jacob David Piwnica-Worms Melvyn Lieberman 《Molecular and cellular biochemistry》1989,89(2):147-150
We have recently reported the presence of an electroneutral (Na + K + 2 Cl) cotransport mechanism that is bumetanide-sensitive and maintains Cli above its electrochemical equilibrium in cultured chick heart cells. In steady state, (Na + K + 2 Cl) cotransport is inwardly directed and so contributes to the Na influx that must be counterbalanced by the activity of the Na/K pump to maintain Nai homeostasis. We now show that manipulating (Na + K + 2 Cl) cotransport by restoring Clo to a Cl-free solution indirectly influences Na/K pump activity because the bumetanide-sensitive recovery of a
infNa
supi
to its control level and the accompanying hyperpolarization could be blocked by 10–4M ouabain. In another protocol, when the Na/K pump was reactivated by restoring Ko (from 0.5 mM to 5.4 mM) and removing ouabain, the recovery of aNa was attenuated by 10–4M bumetanide. The relatively slow rate of ouabain dissociation coupled with the activation of Na influx by (Na + K + 2 Cl) cotransport clearly establishes the interaction of these transport mechanisms in regulating Nai. Although (Na + K + 2 Cl) cotransport is electroneutral, secondary consequences of its activity can indirectly affect the electrophysiological properties of cardiac cells. 相似文献