全文获取类型
收费全文 | 710篇 |
免费 | 48篇 |
出版年
2023年 | 2篇 |
2021年 | 13篇 |
2020年 | 7篇 |
2019年 | 11篇 |
2018年 | 16篇 |
2017年 | 7篇 |
2016年 | 17篇 |
2015年 | 16篇 |
2014年 | 20篇 |
2013年 | 40篇 |
2012年 | 38篇 |
2011年 | 28篇 |
2010年 | 14篇 |
2009年 | 19篇 |
2008年 | 40篇 |
2007年 | 26篇 |
2006年 | 33篇 |
2005年 | 35篇 |
2004年 | 29篇 |
2003年 | 41篇 |
2002年 | 38篇 |
2001年 | 27篇 |
2000年 | 27篇 |
1999年 | 24篇 |
1998年 | 8篇 |
1997年 | 17篇 |
1996年 | 13篇 |
1995年 | 6篇 |
1994年 | 9篇 |
1993年 | 7篇 |
1992年 | 17篇 |
1991年 | 14篇 |
1990年 | 16篇 |
1989年 | 13篇 |
1988年 | 9篇 |
1987年 | 8篇 |
1986年 | 9篇 |
1985年 | 5篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1978年 | 3篇 |
1976年 | 2篇 |
1975年 | 4篇 |
1974年 | 2篇 |
1965年 | 1篇 |
1964年 | 2篇 |
1963年 | 1篇 |
1962年 | 1篇 |
排序方式: 共有758条查询结果,搜索用时 234 毫秒
31.
Plebejus argyrognomon is an endangered grassland butterfly species in Japan. In this study we focused on the parasitism rate of tachinid flies under different mowing management to obtain knowledge of this possible top-down effect that has been largely ignored. We established three mowing treatments differing in the intensity of mowing, as represented by vegetation height. The results showed that the parasitism rate of P. argyrognomon increased with vegetation height; the parasitism rate in blocks subjected to the highest mowing intensity was 8%, whereas in blocks subjected to the lowest mowing intensity, the rate was 42%. We suggest that clarifying interspecific interactions is important for understanding how habitat management affects grassland-inhabiting butterflies in general. 相似文献
32.
We examined complex geographical patterns in the morphology of a kleptoparasitic spider, Argyrodes kumadai, across its distributional range in Japan. To disentangle biotic and abiotic factors underlying morphological variation, latitudinal trends were investigated in two traits, body size and relative leg length, across separate transition zones for host use and voltinism. Statistical analyses revealed complex sawtooth clines. Adult body size dramatically changed at the transition zones for host use and voltinism, and exhibited a latitudinal decline following the converse to Bergmann’s cline under the same host use and voltinism in both sexes. A similar pattern was observed for relative leg length in females but not in males. A genetic basis for a part of observed differences in morphology was supported by a common-garden experiment. Our data suggest that local adaptation to factors other than season length such as resource availability (here associated with host use) obscures underlying responses to latitude. 相似文献
33.
Tomoyuki Miyashita Shinya Neri Hiroko Hashimoto Asami Akutsu Masato Sugano Satoshi Fujii Atsushi Ochiai Genichiro Ishii 《Journal of cellular physiology》2020,235(10):7251-7260
To clear whether podoplanin-positive cancer stem cells in squamous cell carcinoma have higher invasion activity during a fibroblasts-dependent invasion. A collagen gel invasion assay was performed using fluorescent ubiquitination-based cell cycle indicator-labeled A431 cells. The total number and number of invading cells in S/G2/M phase were counted using time-lapse imaging cocultured with fibroblasts. There was no significant difference between the number of invading podoplanin-positive and negative A431 cells when fibroblasts did not exist. On the contrary, the number of invading podoplanin-positive cells was significantly higher when fibroblasts existed. The frequency of cells in S/G2/M phase among invasion was no difference. Knockdown of podoplanin decreased the number of invaded A431 cells significantly when fibroblasts existed. Podoplanin-positive A431 cells display higher invasion activity when fibroblasts exist, suggesting that some biological functions of cancer stem cells might become evident only within the fibrous tumor microenvironment. 相似文献
34.
Yoshimasa Sagane Keita Miyata Sayuri Kurihara Tohru Yoneyama Ken Inui Shin-Ichiro Miyashita Shintaro Hayashi Tomonori Suzuki Koichi Niwa Toshihiro Watanabe 《Current microbiology》2013,67(2):188-192
Botulinum neurotoxin (BoNT) binds to nontoxic nonhemagglutinin (NTNHA) protein in a pH-dependent manner, and yields the protease-resistant BoNT/NTNHA complex. Here, we screened short peptides that bind to the serotype D NTNHA (NTNHA-D) using random phage display technique. NTNHA was fixed onto electrode of quartz crystal microbalance (QCM) apparatus, and then the phages displaying random heptapeptides were exposed to the NTNHA-D under the acidic condition. After rinsing with acidic buffer, the released phages under the alkaline condition were collected. The binding and release of the phage were monitored by the frequency shift on the QCM. As a result of the screening, 16 were selected as peptides that bind to NTNHA-D. The selected peptides do not share any conserved sequence, but tend to be rich in basic and/or hydrophobic amino acid. This would explain the binding manner of the BoNT to the NTNHA protein. 相似文献
35.
36.
Keiji Saito Akira Nakao Tsuyoshi Shinozuka Kousei Shimada Satoshi Matsui Kiyoshi Oizumi Kazuki Yano Keiko Ohata Daisuke Nakai Yoko Nagai Satoru Naito 《Bioorganic & medicinal chemistry》2013,21(7):1628-1642
A cell-based assay was performed for the discovery of novel bone anabolic agents. Alkaline phosphatase (ALPase) activity of ST2 cells was utilized as an indicator of osteoblastic differentiation, and thienopyridine derivative 1 was identified as a hit compound. 3-Aminothieno[2,3-b]pyridine-2-carboxamide was confirmed to be a necessary core structure for the enhancement of ALPase activity, and then optimization of the C4-substituent on the thienopyridine ring was carried out. Introduction of cyclic amino groups to the C4-position of the thienopyridine ring improved the activity. Especially, N-phenyl-homopiperazine derivatives were found to be strong enhancers of ALPase among this new series. Furthermore, 3-amino-4-(4-phenyl-1,4-diazepan-1-yl)thieno[2,3-b]pyridine-2-carboxamide (15k) was orally administered to ovariectomized (OVX) rats over 6 weeks for evaluating the effects on areal bone mineral density (aBMD), and statistically significant improvements in aBMD were observed from the dosage of 10 mg/kg/day. 相似文献
37.
Yuya Watari Shota Nishijima Marina Fukasawa Fumio Yamada Shintaro Abe Tadashi Miyashita 《Ecology and evolution》2013,3(14):4711-4721
For maintaining social and financial support for eradication programs of invasive species, quantitative assessment of recovery of native species or ecosystems is important because it provides a measurable parameter of success. However, setting a concrete goal for recovery is often difficult owing to lack of information prior to the introduction of invaders. Here, we present a novel approach to evaluate the achievement level of invasive predator management based on the carrying capacity of endangered species estimated using long‐term monitoring data. In Amami‐Oshima Island, Japan, where the eradication project of introduced small Indian mongoose is ongoing since 2000, we surveyed the population densities of four endangered species threatened by the mongoose (Amami rabbit, the Otton frog, Amami tip‐nosed frog, and Amami Ishikawa's frog) at four time points ranging from 2003 to 2011. We estimated the carrying capacities of these species using the logistic growth model combined with the effects of mongoose predation and environmental heterogeneity. All species showed clear tendencies toward increasing their density in line with decreased mongoose density, and they exhibited density‐dependent population growth. The estimated carrying capacities of three endangered species had small confidence intervals enough to measure recovery levels by the mongoose management. The population density of each endangered species has recovered to the level of the carrying capacity at about 20–40% of all sites, whereas no individuals were observed at more than 25% of all sites. We propose that the present approach involving appropriate monitoring data of native organism populations will be widely applicable to various eradication projects and provide unambiguous goals for management of invasive species. 相似文献
38.
Satoshi Yamamoto Kenji Minami Keiichi Fukaya Kohji Takahashi Hideki Sawada Hiroaki Murakami Satsuki Tsuji Hiroki Hashizume Shou Kubonaga Tomoya Horiuchi Masamichi Hongo Jo Nishida Yuta Okugawa Ayaka Fujiwara Miho Fukuda Shunsuke Hidaka Keita W. Suzuki Masaki Miya Hitoshi Araki Hiroki Yamanaka Atsushi Maruyama Kazushi Miyashita Reiji Masuda Toshifumi Minamoto Michio Kondoh 《PloS one》2016,11(3)
Recent studies in streams and ponds have demonstrated that the distribution and biomass of aquatic organisms can be estimated by detection and quantification of environmental DNA (eDNA). In more open systems such as seas, it is not evident whether eDNA can represent the distribution and biomass of aquatic organisms because various environmental factors (e.g., water flow) are expected to affect eDNA distribution and concentration. To test the relationships between the distribution of fish and eDNA, we conducted a grid survey in Maizuru Bay, Sea of Japan, and sampled surface and bottom waters while monitoring biomass of the Japanese jack mackerel (Trachurus japonicus) using echo sounder technology. A linear model showed a high R2 value (0.665) without outlier data points, and the association between estimated eDNA concentrations from the surface water samples and echo intensity was significantly positive, suggesting that the estimated spatial variation in eDNA concentration can reflect the local biomass of the jack mackerel. We also found that a best-fit model included echo intensity obtained within 10–150 m from water sampling sites, indicating that the estimated eDNA concentration most likely reflects fish biomass within 150 m in the bay. Although eDNA from a wholesale fish market partially affected eDNA concentration, we conclude that eDNA generally provides a ‘snapshot’ of fish distribution and biomass in a large area. Further studies in which dynamics of eDNA under field conditions (e.g., patterns of release, degradation, and diffusion of eDNA) are taken into account will provide a better estimate of fish distribution and biomass based on eDNA. 相似文献
39.
Fishing for jaws in early vertebrate evolution: a new hypothesis of mandibular confinement
下载免费PDF全文
![点击此处可从《Biological reviews of the Cambridge Philosophical Society》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Tetsuto Miyashita 《Biological reviews of the Cambridge Philosophical Society》2016,91(3):611-657
The evolutionary origin of the vertebrate jaw persists as a deeply puzzling mystery. More than 99% of living vertebrates have jaws, but the evolutionary sequence that ultimately gave rise to this highly successful innovation remains controversial. A synthesis of recent fossil and embryological findings offers a novel solution to this enduring puzzle. The Mandibular Confinement Hypothesis proposes that the jaw evolved via spatial confinement of the mandibular arch (the most anterior pharyngeal arch within which the jaw arose). Fossil and anatomical evidence reveals: (i) the mandibular region was initially extensive and distinct among the pharyngeal arches; and (ii) with spatial confinement, the mandibular arch acquired a common pharyngeal pattern only at the origin of the jaw. The confinement occurred via a shift of a domain boundary that restricted the space the mesenchymal cells of the mandibular arch could occupy. As the surrounding domains replaced mandibular structures at the periphery, this shift allowed neural crest cells and mesodermal mesenchyme of the mandibular arch to acquire patterning programs that operate in the more posterior arches. The mesenchymal population within the mandibular arch was therefore no longer required to differentiate into specialized feeding and ventilation structures, and was remodelled into a jaw. Embryological evidence corroborates that the mandibular arch must be spatially confined for a jaw to develop. This new interpretation suggests neural crest as a key facilitator in correlating elements of the classically recognized vertebrate head ‘segmentation’. 相似文献
40.
Lida Xing Martin G. Lockley Jianping Zhang Hendrik Klein Daqing Li Tetsuto Miyashita 《Historical Biology》2016,28(7):881-895
A dinosaur tracksite in the Lower Jurassic Ziliujing Formation of Sichuan Province, China consists of a spectacular sub-vertical exposure, with multiple track-bearing levels and trackways showing parallel and bimodal orientations. Based on well-preserved material, the new ichnogenus and ichnospecies, Liujianpus shunan ichnogen. nov. ichnosp. nov. is erected to accommodate distinctive sauropodomorph trackways occurring in this assemblage. Liujianpus has a unique combination of features, some relating to the early Jurassic basal sauropodomorph (prosauropod in traditional usage) ichnogenus Otozoum, others to the sauropod ichnogenus Brontopodus. Despite such a mix of basal sauropodomorph- and sauropod-like features, the trackmaker of Liujianpus is likely a basal sauropodomorph. This identification is consistent with the occurrence of basal sauropodomorph skeletons from geographically and chronologically close localities. The other distinct morphotype from the tracksite is linked to a sauropod trackmaker. As such, the ichnofauna consisting of two distinct foot morphotypes reflects the diversity of sauropodomorph dinosaurs in the Early Jurassic of Asia. 相似文献