全文获取类型
收费全文 | 2134篇 |
免费 | 121篇 |
专业分类
2255篇 |
出版年
2022年 | 16篇 |
2021年 | 22篇 |
2019年 | 16篇 |
2018年 | 22篇 |
2017年 | 22篇 |
2016年 | 36篇 |
2015年 | 65篇 |
2014年 | 74篇 |
2013年 | 136篇 |
2012年 | 100篇 |
2011年 | 94篇 |
2010年 | 62篇 |
2009年 | 57篇 |
2008年 | 120篇 |
2007年 | 89篇 |
2006年 | 103篇 |
2005年 | 94篇 |
2004年 | 112篇 |
2003年 | 88篇 |
2002年 | 98篇 |
2001年 | 67篇 |
2000年 | 55篇 |
1999年 | 54篇 |
1998年 | 18篇 |
1997年 | 24篇 |
1996年 | 12篇 |
1995年 | 22篇 |
1994年 | 17篇 |
1993年 | 19篇 |
1992年 | 51篇 |
1991年 | 46篇 |
1990年 | 46篇 |
1989年 | 40篇 |
1988年 | 27篇 |
1987年 | 28篇 |
1986年 | 24篇 |
1985年 | 27篇 |
1984年 | 27篇 |
1983年 | 24篇 |
1982年 | 13篇 |
1981年 | 11篇 |
1980年 | 19篇 |
1979年 | 21篇 |
1978年 | 11篇 |
1977年 | 13篇 |
1976年 | 10篇 |
1975年 | 14篇 |
1974年 | 12篇 |
1973年 | 14篇 |
1972年 | 10篇 |
排序方式: 共有2255条查询结果,搜索用时 15 毫秒
991.
M. Toida Y. Okumura K. K. Swe Win N. Oka T. Takami R. ádány 《The Histochemical journal》1995,27(6):449-456
Summary In the present study, the distribution pattern and characteristics of cells containing Factor XIII subunita (FXIII A) have been studied in benign and malignant lesions of human buccal mucosa. Tissues from four irritation fibromas
and three squamous cell carcinomas were studied by means of double immunofluorescent staining techniques in which the detection
of FXIII A was combined with a reaction with CD14 (recognizing a monocyte/macrophage differentiation marker antigen), Mac
387 (reacting with a special subset of macrophages), anti-HLA-DR, Ki-M7 (labelling phagocytosing macrophages) or Ki-67 (visualizing
a nuclear antigen associated with cell proliferation) monoclonal antibodies. FXIII A was detected in cells of the connective
tissue stroma in both benign and malignant buccal lesions. The number of these FXIII A-reactive cells (FXIII A+ cells) increased considerably in the tumour tissues, in particular in those surrounding tumour cell clusters. FXIII A+ cells scattered in the fibromatous tissues were spindle-shaped, whereas in the tumour stroma, large stellate cells predominated,
and round cells were likewise labelled around blood vessels. FXIII A+ cells were labelled with CD14 and Ki-M7 in both fibromatous and tumoural buccal mucosa; however, they failed to show any
reaction with Ki-67. FXIII A+ cells accumulated in the tumour stroma reacted for HLA-DR as well. These results indicate that in both the benign and malignant
buccal lesions FXIII A is contained in a subpopulation of tissue macrophages, which represents a monocyte-derived (CD14+) and phagocytosing (KiM7+) cell population. The accumulation of the FXIII A+ cells in the tumour stroma is believed to be a result of direct migration from the circulating blood. The FXIII A+ cells of the tumour stroma may be actively involved in both antigen presentation and matrix remodelling during tumour progression. 相似文献
992.
S Oka 《Biorheology》1985,22(4):315-321
A new physical theory of erythrocyte sedimentation is proposed. Various assumptions underlying Stokes' formula are first criticized. An explicit formula is proposed, taking into account some of the results of recent experimental investigations including the effect of upward flow of plasma and the time course of growth of aggregates. It is generally shown that the sedimentation curve without aggregation never becomes a sigmoid. Our formula is applicable to the increased ESR due to the aggregation of erythrocytes. The sedimentation velocity depends not only on the hematocrit and the ultimate size of the aggregates, but also on the retardation time of the growth of aggregates in conformity with the experimental result of Kernick et al. 相似文献
993.
Ken Tokizawa Shinichi Sawada Tatsuo Oka Akinori Yasuda Tetsuo Tai Hirofumi Ida Kazumi Nakayama 《International journal of biometeorology》2014,58(9):1919-1925
This study compared heat strain during walking while wearing impermeable protective suits between fan-precooling and nonprecooling conditions. Six males engaged in 60 min of walking at a moderate speed (~2.5 km/h) in a hot environment (37 °C, 40 % relative humidity). Fanning using a fan (4.5 m/s) and spraying water over the body before wearing the suits produced significantly lower rectal temperature before the walking (37.3?±?0.1 °C vs. 37.0?±?0.1 °C, P?0.05). In addition, whilst walking, rectal temperature was significantly lower in the precooling condition (maximum difference: 0.4 °C at 15 min of walking; 38.0?±?0.1 °C vs. 37.8?±?0.1 °C at the end of walking, P?0.05). Although skin temperature decreased during fanning, no difference was observed during walking. Heart rate was lower in the precooling condition during the early stages of walking. Thermal and fatigue perceptions whilst walking did not differ between the conditions. Body weight loss was significantly lower in the precooling condition. These results may indicate that fan precooling attenuates exertional heat strain while wearing impermeable protective clothing. The fan-cooling method is practical, convenient, and yields lower heat strain during prolonged moderate exertion. 相似文献
994.
995.
Daisuke Kosumi Ritsuko Fujii Mitsuru Sugisaki Naohiro Oka Masahiko Iha Hideki Hashimoto 《Photosynthesis research》2014,121(1):61-68
Fucoxanthin, containing a carbonyl group in conjugation with its polyene backbone, is a naturally occurring pigment in marine organisms and is essential to the photosynthetic light-harvesting function in brown alga and diatom. Fucoxanthin exhibits optical characteristics attributed to an intramolecular charge transfer (ICT) state that arises in polar environments due to the presence of the carbonyl group. In this study, we report the spectroscopic properties of fucoxanthin in methanol (polar and protic solvent) observed by femtosecond pump–probe measurements in the near-infrared region, where transient absorption associated with the optically allowed S2 (11B u + ) state and stimulated emission from the strongly coupled S1/ICT state were observed following one-photon excitation to the S2 state. The results showed that the amplitude of the stimulated emission of the S1/ICT state increased with decreasing excitation energy, demonstrating that the fucoxanthin form associated with the lower energy of the steady-state absorption exhibits stronger ICT character. 相似文献
996.
Ayumi Nakagawa Kazuki Moriya Mayuno Arita Yohei Yamamoto Kyotaro Kitamura Naoki Ishiguro Taro Kanzaki Toshihiko Oka Koki Makabe Kunihiro Kuwajima Masafumi Yohda 《Journal of molecular biology》2014
Group II chaperonin captures an unfolded protein while in its open conformation and then mediates the folding of the protein during ATP-driven conformational change cycle. In this study, we performed kinetic analyses of the group II chaperonin from a hyperthermophilic archaeon, Thermococcus sp. KS-1 (TKS1-Cpn), by stopped-flow fluorometry and stopped-flow small-angle X-ray scattering to reveal the reaction cycle. Two TKS1-Cpn variants containing a Trp residue at position 265 or position 56 exhibit nearly the same fluorescence kinetics induced by rapid mixing with ATP. Fluorescence started to increase immediately after the start of mixing and reached a maximum at 1–2 s after mixing. Only in the presence of K+ that a gradual decrease in fluorescence was observed after the initial peak. Similar results were obtained by stopped-flow small-angle X-ray scattering. A rapid fluorescence increase, which reflects nucleotide binding, was observed for the mutant containing a Trp residue near the ATP binding site (K485W), irrespective of the presence or absence of K+. Without K+, a small, rapid fluorescence decrease followed the initial increase, and then a gradual decrease was observed. In contrast, with K+, a large, rapid fluorescence decrease occurred just after the initial increase, and then the fluorescence gradually increased. Finally, we observed ATP binding signal and also subtle conformational change in an ATPase-deficient mutant with K485W mutation. Based on these results, we propose a reaction cycle model for group II chaperonins. 相似文献
997.
Shiro Itoi Junya Uchida Shihori Takanashi Tomoyo Narita Koko Abe Satomi Naya Haruo Sugita 《Annals of microbiology》2014,64(3):1267-1274
Lactic acid bacteria (LAB) were isolated from the intestinal tract of the wild clam Meretrix lamarckii caught from the coastal waters of Kashima, Ibaraki, Japan. As many as 415 isolates were obtained using the culture method, of which 70 were considered presumptive LAB strains based on phenotypic tests. Phylogenetic analysis of these presumptive isolates of LAB based on the sequence of the 16S rRNA gene demonstrated that the species belonged to several genera of Lactobacillus, Lactococcus and Pediococcus. Interestingly, however, the species composition was different between the samples in July and October 2010. Further analyses based on the fermentation profiles revealed that the LAB from the clam caught in July 2010 were identified to be Lactobacillus curvatus, Lactobacillus plantarum, Lactococcus lactis subsp. cremoris and Pediococcus pentosaceus, whereas those in October 2010 were identified to be Lactobacillus plantarum, Lactococcus lactis subsp. lactis and P. pentosaceus. The diversity of LAB in the intestinal tract of the clam suggests that the filter feeder bivalves such as M. lamarckii are a rich repository of marine isolates of LAB. 相似文献
998.
Peridinin‐containing dinoflagellates have small circular DNA molecules called minicircle DNAs, each of which encodes one, or occasionally a few, plastid proteins or ribosomal RNA. Dinoflagellate minicircle DNA is composed of two parts: a gene‐coding sequence and a non‐coding sequence that consists of several variable and core regions. The core regions are identical among the minicircle DNAs with different genes within a species or strain. Because such structure is very different from those of well known plastid DNAs, many functional and evolutionary questions have been raised for the minicircle DNAs, and several studies that focus on answering those questions are underway. However, the localization of minicircle DNA is still controversial: several lines of indirect evidence have implied plastid localization, whereas the nuclear localization of minicircle DNA has also been suggested in a species. In order to understand the evolution and function of minicircle DNA, it is important to know its precise localization. In this study, we sequenced two typical minicircle DNAs, one encodes psbA and the other encodes 23S rRNA genes, from an Amphidinium massartii strain (TM16). To determine the subcellular localization of these minicircle DNAs, we performed DNA‐targeted whole cell fluorescence in situ hybridization with A. massartii minicircle DNA‐specific probes and demonstrated that minicircle DNAs were present in plastids. This study provides the first direct evidence for the plastid localization of dinoflagellate minicircle DNAs. 相似文献
999.