全文获取类型
收费全文 | 2115篇 |
免费 | 88篇 |
出版年
2023年 | 9篇 |
2022年 | 8篇 |
2021年 | 47篇 |
2020年 | 27篇 |
2019年 | 51篇 |
2018年 | 57篇 |
2017年 | 37篇 |
2016年 | 86篇 |
2015年 | 118篇 |
2014年 | 124篇 |
2013年 | 157篇 |
2012年 | 214篇 |
2011年 | 204篇 |
2010年 | 130篇 |
2009年 | 108篇 |
2008年 | 161篇 |
2007年 | 145篇 |
2006年 | 88篇 |
2005年 | 96篇 |
2004年 | 78篇 |
2003年 | 65篇 |
2002年 | 42篇 |
2001年 | 28篇 |
2000年 | 29篇 |
1999年 | 25篇 |
1998年 | 11篇 |
1997年 | 5篇 |
1996年 | 1篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1993年 | 5篇 |
1992年 | 9篇 |
1991年 | 5篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1970年 | 1篇 |
1969年 | 2篇 |
1968年 | 1篇 |
1967年 | 3篇 |
1965年 | 1篇 |
排序方式: 共有2203条查询结果,搜索用时 15 毫秒
11.
Callus cultures and cell suspension cultures derived from Ginkgo biloba L. leaves produced ginkgolidc B. In cell suspension cultures, the production reached a maximum by the 13th day of subculture and followed by a sharp decrease. The medium of Murashige and Skoog induced the highest ginkgolide B content in cultures while the medium of Schenk and Hildebrandt promoted cell growth. For the maximal production of ginkgolide B, cells were cultured in Murashige and Skoog medium modified to contain 1.0 mg/l of -naphthaleneacetic acid, 0.1 mg/1 of kinetin, 30 g/1 sucrose and 1.25 mM potassium phosphate with a molar ratio of ammonium to nitrate ions of 1 3.Abbreviations B5
Gamborg et al (1968) medium
- GKB
Ginkgolide B
- MS
Murashige and Skoog (1962) medium
- NAA
-naphthaleneacetic aicd
- SH
Schenk and Hildebrandt (1972) medium 相似文献
12.
Genetic variation at the Major Histocompatibility Complex locus DQ beta was
analyzed in 233 beluga whales (Delphinapterus leucas) from seven
populations: St. Lawrence Estuary, eastern Beaufort Sea, eastern Chukchi
Sea, western Hudson Bay, eastern Hudson Bay, southeastern Baffin Island,
and High Arctic and in 12 narwhals (Monodon monoceros) sympatric with the
High Arctic beluga population. Variation was assessed by amplification of
the exon coding for the peptide binding region via the polymerase chain
reaction, followed by either cloning and DNA sequencing or single-stranded
conformation polymorphism analysis. Five alleles were found across the
beluga populations and one in the narwhal. Pairwise comparisons of these
alleles showed a 5:1 ratio of nonsynonymous to synonymous substitutions per
site leading to eight amino acid differences, five of which were
nonconservative substitutions, centered around positions previously shown
to be important for peptide binding. Although the amount of allelic
variation is low when compared with terrestrial mammals, the nature of the
substitutions in the peptide binding sites indicates an important role for
the DQ beta locus in the cellular immune response of beluga whales.
Comparisons of allele frequencies among populations show the High Arctic
population to be different (P < or = .005) from the other beluga
populations surveyed. In these other populations an allele, Dele-DQ
beta*0101-2, was found in 98% of the animals, while in the High Arctic it
was found in only 52% of the animals. Two other alleles were found at high
frequencies in the High Arctic population, one being very similar to the
single allele found in narwhal.
相似文献
13.
The neotype ofRepomucenus sagitta is described. Specimens conspecific with the neotype from India, the Gulf of Thailand, the South China Sea, the Yellow Sea
and Australia are described. Sexual characters, geographic variation, habitat and geographic distribution were noted.Repomucenus macdonaldi is a junior synonym ofR. sagitta as defined by the neotype. 相似文献
14.
The flexibility and self-healing properties of animal cell surface membranes are well known. These properties have been best exploited in various micrurgical studies on living cells (2, 3), especially in amoebae (7, 20). During nuclear transplantation in amoebae, the hole in the membrane through which a nucleus passes can have a diameter of 20-30 μm, and yet such holes are quickly sealed, although some cytoplasm usually escapes during the transfer. While enucleating amoebae in previous studies, we found that if a very small portion of a nucleus was pushed through the membrane and exposed to the external medium, the amoeba expelled such a nucleus on its own accord. When this happened, a new membrane appeared to form around the embedded portion of the nucleus and no visible loss of cytoplasm occurred during nuclear extrusion. In the present study, we examined amoebae that were at different stages of expelling partially exposed nuclei, to follow the sequence of events during the apparent new membrane formation. Unexpectedly, we found that a new membrane is not formed around the nucleus from inside but a hole is sealed primarily by a constriction of the existing membrane, and that cytoplasmic filaments are responsible for the prevention of the loss of cytoplasm. 相似文献
15.
Jin Goo Lee Jae‐Ha Myung Aaron B. Naden Ok Sung Jeon Yong Gun Shul John T. S. Irvine 《Liver Transplantation》2020,10(10)
For efficient catalysis and electrocatalysis well‐designed, high‐surface‐area support architectures covered with highly dispersed metal nanoparticles with good catalyst‐support interactions are required. In situ grown Ni nanoparticles on perovskites have been recently reported to enhance catalytic activities in high‐temperature systems such as solid oxide cells (SOCs). However, the micrometer‐scale primary particles prepared by conventional solid‐state reactions have limited surface area and tend to retain much of the active catalytic element within the bulk, limiting efficacy of such exsolution processes in low‐temperature systems. Here, a new, highly efficient, solvothermal route is demonstrated to exsolution from smaller scale primary particles. Furthermore, unlike previous reports of B‐site exsolution, it seems that the metal nanoparticles are exsolved from the A‐site of these perovskites. The catalysts show large active site areas and strong metal‐support interaction (SMSI), leading to ≈26% higher geometric activity (25 times higher mass activity with 1.4 V of Eon‐set) and stability for oxygen‐evolution reaction (OER) with only 0.72 µg base metal contents compared to typical 20 wt% Ni/C and even commercial 20 wt% Ir/C. The findings obtained here demonstrate the potential design and development of heterogeneous catalysts in various low‐temperature electrochemical systems including alkaline fuel cells and metal–air batteries. 相似文献
16.
17.
Nagasundarapandian Soundrarajan Cho Hye-sun Prathap Somasundaram Kang Mingue Choi Munjeong Lee Yunjung Jeon Hyoim Song Hyuk Kim Jin-Hoi Park Chankyu 《Amino acids》2021,53(2):313-317
The effects of ΔPb-CATH4, a cathelicidin derived from Python bivittatus, were evaluated against Staphylococcus aureus-infected wounds in mice. These effects were comparable to those of classical antibiotics. ΔPb-CATH4 was resistant to bacterial protease but not to porcine trypsin. A reduction in the level of inflammatory cytokines and an increase in the migration of immune cells was observed in vitro. Thus, ΔPb-CATH4 can promote wound healing by controlling infections including those caused by multidrug-resistant bacteria via its immunomodulatory effects.
相似文献18.
19.
20.
Min-Young Song Chi-Yeol Kim Muho Han Hak-Seung Ryu Sang-Kyu Lee Li Sun Zuhua He Young-Su Seo Patrick Canal Pamela C. Ronald Jong-Seong Jeon 《Molecules and cells》2013,35(4):327-334
The required for Mla12 resistance (RAR1) protein is essential for the plant immune response. In rice, a model monocot species, the function of Oryza sativa RAR1 (OsRAR1) has been little explored. In our current study, we characterized the response of a rice osrar1 T-DNA insertion mutant to infection by Magnaporthe oryzae, the causal agent of rice blast disease. osrar1 mutants displayed reduced resistance compared with wild type rice when inoculated with the normally virulent M. oryzae isolate PO6-6, indicating that OsRAR1 is required for an immune response to this pathogen. We also investigated the function of OsRAR1 in the resistance mechanism mediated by the immune receptor genes Pib and Pi5 that encode nucleotide binding-leucine rich repeat (NB-LRR) proteins. We inoculated progeny from Pib/osrar1 and Pi5/osrar1 heterozygous plants with the avirulent M. oryzae isolates, race 007 and PO6-6, respectively. We found that only Pib-mediated resistance was compromised by the osrar1 mutation and that the introduction of the OsRAR1 cDNA into Pib/osrar1 rescued Pib-mediated resistance. These results indicate that OsRAR1 is required for Pib-mediated resistance but not Pi5-mediated resistance to M. oryzae. 相似文献