全文获取类型
收费全文 | 1311篇 |
免费 | 112篇 |
专业分类
1423篇 |
出版年
2022年 | 6篇 |
2021年 | 13篇 |
2019年 | 9篇 |
2018年 | 10篇 |
2017年 | 16篇 |
2016年 | 23篇 |
2015年 | 25篇 |
2014年 | 33篇 |
2013年 | 50篇 |
2012年 | 80篇 |
2011年 | 62篇 |
2010年 | 35篇 |
2009年 | 38篇 |
2008年 | 44篇 |
2007年 | 44篇 |
2006年 | 42篇 |
2005年 | 51篇 |
2004年 | 60篇 |
2003年 | 50篇 |
2002年 | 64篇 |
2001年 | 43篇 |
2000年 | 71篇 |
1999年 | 50篇 |
1998年 | 19篇 |
1997年 | 20篇 |
1996年 | 18篇 |
1995年 | 26篇 |
1994年 | 21篇 |
1993年 | 14篇 |
1992年 | 42篇 |
1991年 | 28篇 |
1990年 | 27篇 |
1989年 | 44篇 |
1988年 | 33篇 |
1987年 | 29篇 |
1986年 | 27篇 |
1985年 | 19篇 |
1984年 | 10篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1981年 | 8篇 |
1979年 | 19篇 |
1978年 | 13篇 |
1977年 | 9篇 |
1974年 | 8篇 |
1972年 | 6篇 |
1971年 | 5篇 |
1970年 | 7篇 |
1969年 | 5篇 |
1968年 | 5篇 |
排序方式: 共有1423条查询结果,搜索用时 15 毫秒
11.
Fujimoto T Kunitomo J Tomata Y Nishiyama K Nakashima M Hirozane M Yoshikubo S Hirai K Marui S 《Bioorganic & medicinal chemistry letters》2011,21(21):6414-6416
During our efforts to identify a series of potent, selective, orally active human Orexin-2 Receptor (OX2R) antagonists, we elucidated structure-activity relationship (SAR) on the 7-position of a benzoxazepine scaffold by utilizing Hammett σ(p) and Hansch-Fujita π value as aromatic substituent constants. The attempts led to the discovery of compound 1m, possessing good in vitro potency with over 100-fold selectivity against OX1R, good metabolic stability in human and rat liver microsome, good oral bioavailability in rats, and in vivo antagonistic activity in rats by oral administration. 相似文献
12.
Ken-ichi Uchida Takamasa Hirai Fuyuki Ando Hossein Sepehri-Amin 《Liver Transplantation》2024,14(3):2302375
In artificially tilted multilayers comprising two different conductors that are alternately and obliquely stacked, transverse thermoelectric conversion occurs, in which charge and heat currents are interconverted in the orthogonal direction. Although transverse thermoelectric conversion also occurs in homogeneous materials as an intrinsic transport phenomenon owing to the effects of magnetic fields, magnetization, and spins on conduction carriers, such magneto-thermoelectric effects are investigated independently of thermoelectrics for artificially tilted multilayers. Here, this study shows that the synergy of these different principles improves the performance of transverse thermoelectric conversion. Using lock-in thermography techniques, transverse thermoelectric conversion processes are visualized in artificially tilted multilayers and the experiments clarify how nonuniform charge currents are converted into orthogonal heat currents. Through the measurements of temperature change under magnetic fields, the contributions of the magneto-thermoelectric effects are quantified in the artificially tilted multilayers and magnetically enhanced hybrid transverse thermoelectric cooling is demonstrated. By replacing one of the conductors in the multilayer with permanent magnets, the same functionality is obtained even in the absence of magnetic fields, paving the way for the creation of “thermoelectric permanent magnets” that exhibit efficient transverse thermoelectric conversion together with spontaneous magnetization. This study provides a new material design guideline for transverse thermoelectrics. 相似文献
13.
Background
Dorsal root ganglia (DRG) somata from rodents have provided an excellent model system to study ion channel properties and modulation using electrophysiological investigation. As in other vertebrates, zebrafish (Danio rerio) DRG are organized segmentally and possess peripheral axons that bifurcate into each body segment. However, the electrical properties of zebrafish DRG sensory neurons, as compared with their mammalian counterparts, are relatively unexplored because a preparation suitable for electrophysiological studies has not been available.Methodology/Principal Findings
We show enzymatically dissociated DRG neurons from juvenile zebrafish expressing Isl2b-promoter driven EGFP were easily identified with fluorescence microscopy and amenable to conventional whole-cell patch-clamp studies. Two kinetically distinct TTX-sensitive Na+ currents (rapidly- and slowly-inactivating) were discovered. Rapidly-inactivating INa were preferentially expressed in relatively large neurons, while slowly-inactivating INa was more prevalent in smaller DRG neurons. RT-PCR analysis suggests zscn1aa/ab, zscn8aa/ab, zscn4ab and zscn5Laa are possible candidates for these INa components. Voltage-gated Ca2+ currents (ICa) were primarily (87%) comprised of a high-voltage activated component arising from ω-conotoxin GVIA-sensitive CaV2.2 (N-type) Ca2+ channels. A few DRG neurons (8%) displayed a miniscule low-voltage-activated component. ICa in zebrafish DRG neurons were modulated by neurotransmitters via either voltage-dependent or -independent G-protein signaling pathway with large cell-to-cell response variability.Conclusions/Significance
Our present results indicate that, as in higher vertebrates, zebrafish DRG neurons are heterogeneous being composed of functionally distinct subpopulations that may correlate with different sensory modalities. These findings provide the first comparison of zebrafish and rodent DRG neuron electrical properties and thus provide a basis for future studies. 相似文献14.
15.
Hirai Nobuhiro; Kojima Yasuhiro; Koshimizu Koichi; Shinozaki Masateru; Takimoto Atsushi 《Plant & cell physiology》1993,34(7):1039-1044
Flowering of Pharbitis nil strain Violet is induced in continuouslight under poor nutritional conditions. High-performance liquidchromatography of extracts of the cotyledons revealed that twocompounds in addition to chlorogenic acid accumulate under suchconditions. The compounds were identified as pinoresinol glucosideand p-coumaroylquinic acid. The endogenous levels of these phenylpropanoidswere correlated with the flowering response when nutrition waspoor. However, activation of phenylpropanoid biosynthesis seemednot to be essential for the induction of flowering. (Received May 17, 1993; Accepted July 26, 1993) 相似文献
16.
To evaluate the effect of the chromosome arm number on the yield of dicentric chromosomes, frequencies of gamma-ray-induced chromosome aberrations were examined with peripheral lymphocytes from three different primate species, Saimiri sciureus (arm number, 77), Macaca fascicularis (arm number, 83) and Nycticebus coucang (arm number, 99). Irradiated blood samples were cultured by the same standard technique as that commonly used for human lymphocytes. The yields of dicentrics and dicentrics plus rings at doses of 100, 200 and 300 rad of gamma-irradiation were not significantly different among the three species, in spite of the difference in the chromosome arm number. Furthermore, dose-response relationships for these species were consistent with that for man. Statistical analysis indicated that the expected dicentric yields calculated from the arm number model were significantly different from the observed yields at 200 and 300 rad doses (P less than 0.01). From these results it can be pointed out that there is no correlation between the yield of dicentrics and the effective chromosome arm number, and that the chromosomal radiosensitivity of these primates is essentially the same as that of man, at least in the lymphocyte system. 相似文献
17.
Integration of Simian Virus 40 Deoxyribonucleic Acid into the Deoxyribonucleic Acid of Permissive Monkey Kidney Cells 总被引:5,自引:9,他引:5 下载免费PDF全文
Integration of simian virus 40 (SV40) deoxyribonucleic acid (DNA) into cellular DNA occurred when permissive African green monkey kidney (CV-1) cells were infected at a low multiplicity of SV40 in the presence of cytosine arabinoside. 相似文献
18.
TLRs detect several classes of virus-associated molecules, such as ssRNA, CpG-DNA and dsRNA, and transduce signals leading to the production of IFN. Recently discovered cytoplasmic RNA helicases, RIG-I and MDA5, selectively sense viral RNA species. Gene disruption studies revealed the critical but non-redundant function of RIG-I and MDA5 in host antiviral responses. 相似文献
19.
This study investigated the seasonal change in xylem growth of Japanese red pine (Pinus densiflora). Wood cores were sampled at 2-week intervals from April to November in 2012 using the microcoring method. Daily increment rates of tracheid number and tree-ring width were compared with seasonal changes in daily mean temperature and photoperiod. Xylem growth started in early to late May and stopped in late October to early November. The maximum daily increment rates of tracheid number and tree-ring width were in early July. The 95 % confidence intervals of the timing of the maximum daily increment rates included the summer solstice (23 June) with the longest photoperiod, but not the warmest day (30 July). The maximum daily increment rate of xylem growth is thought to be controlled by the photoperiod rather than by temperature. The daily mean temperature exceeded 20 °C after the summer solstice, indicating that temperature is not a limiting factor for xylem growth. This study suggests that the timing of maximum daily increment rates of xylem growth of P. densiflora is controlled by the photoperiod. 相似文献
20.
Molecular taxonomy of dermatophytes and related fungi by chitin synthase 1 (CHS1) gene sequences 总被引:2,自引:0,他引:2
In the present study, the nucleotide sequences of the CHS1 gene from dermatophytes and related fungi in the genera Chrysosporium, Epidermophyton, Microsporum and Trichophyton were investigated using molecular methods. About 440-bp genomic DNA fragments of the CHS1 gene from 21 species were amplified by polymerase chain reaction (PCR) and sequenced. The CHS1 nucleotide sequences of these fungi showed more than 83% similarity. The molecular taxonomy of the CHS1 gene sequences revealed that Microsporum was genetically distinct from Chrysosporium and Trichophyton, as classified by morphological characteristics.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献