全文获取类型
收费全文 | 2058篇 |
免费 | 105篇 |
国内免费 | 3篇 |
出版年
2021年 | 14篇 |
2020年 | 12篇 |
2019年 | 14篇 |
2018年 | 18篇 |
2017年 | 14篇 |
2016年 | 27篇 |
2015年 | 34篇 |
2014年 | 52篇 |
2013年 | 137篇 |
2012年 | 98篇 |
2011年 | 104篇 |
2010年 | 50篇 |
2009年 | 69篇 |
2008年 | 112篇 |
2007年 | 108篇 |
2006年 | 120篇 |
2005年 | 96篇 |
2004年 | 117篇 |
2003年 | 115篇 |
2002年 | 125篇 |
2001年 | 61篇 |
2000年 | 52篇 |
1999年 | 45篇 |
1998年 | 40篇 |
1997年 | 24篇 |
1996年 | 25篇 |
1995年 | 31篇 |
1994年 | 20篇 |
1993年 | 20篇 |
1992年 | 27篇 |
1991年 | 35篇 |
1990年 | 19篇 |
1989年 | 26篇 |
1988年 | 24篇 |
1987年 | 21篇 |
1986年 | 23篇 |
1985年 | 26篇 |
1984年 | 13篇 |
1983年 | 12篇 |
1982年 | 17篇 |
1981年 | 23篇 |
1980年 | 21篇 |
1979年 | 12篇 |
1978年 | 22篇 |
1977年 | 11篇 |
1976年 | 8篇 |
1975年 | 8篇 |
1974年 | 10篇 |
1973年 | 12篇 |
1971年 | 7篇 |
排序方式: 共有2166条查询结果,搜索用时 15 毫秒
71.
NAD recycling in the collagen membrane was investigated as follows: (1) Alcohol dehydrogenase and lactate dehydrogenase were co-immobilized in the collagen membrane and the rate of lactate production by immobilized enzymes was compared with that of free enzymes by using free NAD. An increased rate was observed in the case of immobilized enzyme. (2) The soluble high molecular weight derivatives of NAD (dextran-NAD) were immobilized in the collagen membrane with the two dehydrogenases and recycling of dextran-NAD in the membrane was examined. Lactate was produced by the membrane without adding free NAD. The interaction between the high molecular weight NAD derivatives and enzymes are also discussed. 相似文献
72.
Katsumi Isono 《Molecular & general genetics : MGG》1978,165(3):265-268
Summary A mutant of Escherichia coli which was isolated for temperature-sensitive growth was found to harbour a structural alteration in protein S16 (Isono et al., 1978). The mutation was localized by matings with various Hfr strains and by Plkc-mediated transduction. The results showed that it mapped very close to the gene coding for L19 protein which has been placed at 56.4 min (Kitakawa and Isono, 1977), indicating that it most likely forms a new ribosomal protein-gene cluster. 相似文献
73.
74.
Jun Kojima Jun Araya Hiromichi Hara Saburo Ito Naoki Takasaka Kenji Kobayashi Satoko Fujii Chikako Tsurushige Takanori Numata Takeo Ishikawa Kenichiro Shimizu Makoto Kawaishi Keisuke Saito Noriki Kamiya Jun Hirano Makoto Odaka Toshiaki Morikawa Hiroshi Hano Satoko Arai Toru Miyazaki Yumi Kaneko Katsutoshi Nakayama Kazuyoshi Kuwano 《Respiratory research》2013,14(1):30
Background
Marked accumulation of alveolar macrophages (AM) conferred by apoptosis resistance has been implicated in pathogenesis of chronic obstructive pulmonary disease (COPD). Apoptosis inhibitor of macrophage (AIM), has been shown to be produced by mature tissue macrophages and AIM demonstrates anti-apoptotic property against multiple apoptosis-inducing stimuli. Accordingly, we attempt to determine if AIM is expressed in AM and whether AIM is involved in the regulation of apoptosis in the setting of cigarette smoke extract (CSE) exposure.Methods
Immunohistochemical evaluations of AIM were performed. Immunostaining was assessed by counting total and positively staining AM numbers in each case (n = 5 in control, n = 5 in non-COPD smoker, n = 5 in COPD). AM were isolated from bronchoalveolar lavage fluid (BALF). The changes of AIM expression levels in response to CSE exposure in AM were evaluated. Knock-down of anti-apoptotic Bcl-xL was mediated by siRNA transfection. U937 monocyte-macrophage cell line was used to explore the anti-apoptotic properties of AIM.Results
The numbers of AM and AIM-positive AM were significantly increased in COPD lungs. AIM expression was demonstrated at both mRNA and protein levels in isolated AM, which was enhanced in response to CSE exposure. AIM significantly increased Bcl-xL expression levels in AM and Bcl-xL was involved in a part of anti-apoptotic mechanisms of AIM in U937 cells in the setting of CSE exposure.Conclusions
These results suggest that AIM expression in association with cigarette smoking may be involved in accumulation of AM in COPD. 相似文献75.
We investigated the effect of background scene on the human visual perception of depth orientation (i.e., azimuth angle) of three-dimensional common objects. Participants evaluated the depth orientation of objects. The objects were surrounded by scenes with an apparent axis of the global reference frame, such as a sidewalk scene. When a scene axis was slightly misaligned with the gaze line, object orientation perception was biased, as if the gaze line had been assimilated into the scene axis (Experiment 1). When the scene axis was slightly misaligned with the object, evaluated object orientation was biased, as if it had been assimilated into the scene axis (Experiment 2). This assimilation may be due to confusion between the orientation of the scene and object axes (Experiment 3). Thus, the global reference frame may influence object orientation perception when its orientation is similar to that of the gaze-line or object. 相似文献
76.
Ryoshiro Wakiya Kenzo Kaifu Kazuhisa Azechi Katsumi Tsukamoto Noritaka Mochioka 《Journal of fish biology》2020,96(2):516-526
This study evaluated the size and age distributions and otolith microchemistry of the Japanese eel Anguilla japonica in freshwater and brackish water areas in the Aki and Tsuchikawa rivers for 1 year, and in brackish water areas in the Asahi River for 3 years to understand the movements of Japanese eels between continental habitats of different salinity after recruitment (n = 759). For all three rivers, the total length (LT) and age distributions were consistent; yellow eels captured in the upper brackish water (Aki River: 353.5 ± 77.4 mm and 3.0 ± 0.8 years; Tsuchikawa River: 287.7 ± 87.3 mm and 3.7 ± 1.3 years; Asahi River: 418.2 ± 112.1 mm and 4.2 ± 1.7 years) were smaller and younger than not only those in the fresh water of the two rivers but also those in the lowest brackish water sampling areas (Aki River: 436.0 ± 71.6 mm and 3.8 ± 1.1 years; Tsuchikawa River: 370.9 ± 121.7 mm and 4.9 ± 2.3 years; Asahi River: 558.5 ± 85.9 mm and 5.7 ± 1.7 years). In the Asahi River, these tendencies were found throughout the 3 years. Otolith analysis indicated that the majority of the eels captured in the lowest brackish water areas had moved down from upstream. These results suggest that Japanese eels inhabiting saline water generally move from the upper estuary as they grow. The upper estuary can be an important area for the management of this species because these eels spend their early continental growth life there. 相似文献
77.
Relationship between body size and ovariole number in three cerambycids inhabiting mulberry orchards
Applied Entomology and Zoology - Natural selection operates on a suite of life-history traits. Those traits are under constraints and trade-offs which often differ among species. Thus, there are an... 相似文献
78.
79.
Kenzo Kaifu Sachie Miyazaki Jun Aoyama Shingo Kimura Katsumi Tsukamoto 《Environmental Biology of Fishes》2013,96(4):439-446
The diet of Japanese eels, Anguilla japonica, was investigated using stomach content and stable isotope analyses. Stable isotope enrichment of carbon and nitrogen (Δδ13C and Δδ15N) was first estimated for A. japonica by comparing the isotopic signatures (δ13C and δ15N) of reared eels to that of their food. The estimated isotope enrichment was then applied to the diet estimation of A. japonica in the Kojima Bay-Asahi River system, Japan, combined with conventional stomach content analysis. Stable isotope enrichment varied among tissues, from 0.2‰ to 0.8‰ for carbon and from 1.3‰ to 2.1‰ for nitrogen. Nitrogen isotope enrichment of A. japonica muscle estimated in this study was 2.1‰, which was different from the previously reported mean δ15N enrichment of several animals of 3.4‰. These results indicate that isotope-based diet estimations for A. japonica need to use species- and tissue-specific values of isotope enrichment. In the diet analysis, stomach contents and stable isotopes revealed that (1) A. japonica appear to usually feed on a single type of prey species in each feeding session, (2) principal prey species were mud shrimp, Upogebia major, in brackish Kojima Bay and crayfish, Procambarus clarkia, in the Asahi River, (3) A. japonica in Kojima Bay primarily depend on the pelagic food web as a carbon source due to mud shrimp being filter feeders and eels in the Asahi River primarily depend on the littoral food web. Based on these results and the recently reported eel movements between Kojima Bay and the Asahi River, it appears that A. japonica can adapt to various feeding environments as opportunists, but also utilize the food resources by targeting a single type of prey species during a single feeding session. 相似文献
80.
Tomoko Mizuguchi Katsumi Hagita Susumu Fujiwara Takeshi Yamada 《Molecular simulation》2013,39(17):1437-1446
ABSTRACTThe structural and dynamical properties of water confined in nanoporous silica with a pore diameter of 2.7?nm were investigated by performing large-scale molecular dynamics simulations using the reactive force field. The radial distribution function and diffusion coefficient of water were calculated, and the values at the centre of the pore agreed well with experimental values for real water. In addition, the pore was divided into thin coaxial layers, and the average number of hydrogen bonds, hydrogen bond lifetime and hydrogen bond strength were calculated as a function of the radial distance from the pore central axis. The analysis showed that hydrogen bonds involving silanol (Si–OH) have a longer lifetime, although the average number of hydrogen bonds per atom does not change from that at the pore centre. The longer lifetime, as well as smaller diffusion coefficient, of these hydrogen bonds is attributed to their greater strength. 相似文献