全文获取类型
收费全文 | 4838篇 |
免费 | 232篇 |
国内免费 | 1篇 |
出版年
2022年 | 22篇 |
2021年 | 29篇 |
2020年 | 15篇 |
2019年 | 25篇 |
2018年 | 39篇 |
2017年 | 42篇 |
2016年 | 69篇 |
2015年 | 109篇 |
2014年 | 129篇 |
2013年 | 494篇 |
2012年 | 245篇 |
2011年 | 259篇 |
2010年 | 175篇 |
2009年 | 160篇 |
2008年 | 249篇 |
2007年 | 292篇 |
2006年 | 261篇 |
2005年 | 282篇 |
2004年 | 330篇 |
2003年 | 261篇 |
2002年 | 271篇 |
2001年 | 47篇 |
2000年 | 48篇 |
1999年 | 54篇 |
1998年 | 61篇 |
1997年 | 56篇 |
1996年 | 38篇 |
1995年 | 49篇 |
1994年 | 48篇 |
1993年 | 54篇 |
1992年 | 73篇 |
1991年 | 52篇 |
1990年 | 39篇 |
1989年 | 40篇 |
1988年 | 44篇 |
1987年 | 40篇 |
1986年 | 48篇 |
1985年 | 44篇 |
1984年 | 44篇 |
1983年 | 44篇 |
1982年 | 45篇 |
1981年 | 52篇 |
1980年 | 41篇 |
1979年 | 29篇 |
1978年 | 28篇 |
1977年 | 28篇 |
1976年 | 30篇 |
1975年 | 19篇 |
1974年 | 26篇 |
1973年 | 20篇 |
排序方式: 共有5071条查询结果,搜索用时 15 毫秒
51.
Kazuo Ota Soji Kurita Kazumasa Yamada Tohru Masaoka Yoshiro Uzuka Nobuya Ogawa 《Cancer immunology, immunotherapy : CII》1986,23(1):5-10
Summary In a cooperative randomized control study of immunotherapy with bestatin in combination with chemotherapy in adults with acute nonlymphocytic leukemia (ANLL), 101 patients (48 in the bestatin group and 53 in the control group) out of 115 patients registered were evaluated as eligible. The bestatin group achieved a statistically significant prolongation of survival compared with the control group in overall ANLL and acute myelogenous leukemia. In the analysis of patient age, the bestatin group achieved a statistically significant prolongation of both the remission duration and survival in patients aged 50 to 65 years, while the differences were not significant in the 15 to 49 age group. The bestatin group tended to achieve a higher rate of reinduction of remission in patients who had recurrence of leukemia. Side effects developed in only 5 (9.6%) of 52 patients treated with bestatin. None of these side effects were particularly serious in nature. It is concluded that bestatin is useful for prolongation of survival of adult patients with ANLL, making for a longer remission duration especially in elderly patients and with few side effects. 相似文献
52.
J Watanabe S Kanamura K Kanai M Yoshikawa M Asada-Kubota 《The Histochemical journal》1983,15(10):999-1009
Ultrastructural localization of glucose-6-phosphatase activity was studied in the cells of the pancreas and submandibular gland of the mouse using a incubation medium modified from that of Wachstein & Meisel (1956). In pancreatic acinar cells, the reaction product for the enzyme activity was not found even after 90 min of incubation with three changes of the medium. However, the reaction product was localized in the endoplasmic reticulum and nuclear envelope of all other cell types composing the pancreas and submandibular gland. The reaction product appeared in moderate to abundant amounts in acinar cells and striated duct cells of the submandibular gland, and in the B cells, A and D cells of the pancreatic islet, but it was scarce in other cell types. 相似文献
53.
The sex-specific glycoprotein agglutination substance, responsiblefor sexual agglutination, solubilized from the surface of haploidcells of a or a mating type by the autoclave method had thefollowing effects on mating reaction in Saccharomyces cerevisiae.Sexual agglutination was inhibited by the agglutination substanceof the opposite mating type in living cells as well as in heat-killedcells. Formation of zygotes was completely inhibited, when botha and a cells were treated with the agglutination substanceof the opposite mating type. The a and a agglutination substanceswere inactivated by cells of the opposite mating type, withthe degree of inactivation being greater for the former. Theenzyme responsible for the inactivation of a agglutination substanceseems to be carboxypeptidase Y.
1 This paper is dedicated to the late Professor J. Ashida, KyotoUniversity.
2 Present address: Department of Plant Pathology, Universityof California, Davis, CA. 95616, U.S.A. (Received November 1, 1982; Accepted January 19, 1983) 相似文献
54.
Mitochondria were isolated from mesophyll protoplasts and bundlesheath protoplasts or strands which were obtained by enzymaticdigestion of six C4 species: Zea mays, Sorghum bicolor, Panicummiliaceum, Panicum capillare, Panicum maximum and Chloris gayana,representative of three C4 types. Photorespiratory glycine oxidationand related enzyme activities of mesophyll and bundle sheathmitochondria were compared. Mesophyll mitochondria showed good P/O ratios with malate andsuccinate as substrate but lacked the ability to oxidize glycine.On the other hand, mitochondria isolated from bundle sheathprotoplasts of P. miliaceum and bundle sheath strands of Z.mays possessed glycine oxidation activity similar to that ofmitochondria from C3 plant leaves. The two enzymes involvedin glycine metabolism in mitochondria, serine hydroxymethyltransferaseand glycine decarboxylase, were also assayed in the mitochondriaof the two cell types. The activities of the two enzymes inbundle sheath mitochondria were in the range found in C3 mitochondria.In contrast, the activities in mesophyll mitochondria were eithernot detectable or far lower than those in bundle sheath mitochondriaand ascribed to contaminating bundle sheath mitochondria. The present results indicate the deficiency of a complete glycineoxidation system in mesophyll mitochondria and also a differentiationbetween mesophyll and bundle sheath cells of C4 plants withrespect to the photorespiratory activities of the mitochondria. (Received June 8, 1983; Accepted August 29, 1983) 相似文献
55.
Estrous cycle, duration of estrus and time of ovulation of eight cyclic buffaloes were examined during a period of one year. Animals were kept under loose-housing conditions and fed according to the Japanese Feeding Standards for dairy cattle. All the animals were observed for the occurrence of estrus twice daily by using a vasectomized bull, and ovarian cycles of each animal were monitored by weekly rectal palpation. Duration of estrus and time of ovulation were determined in 32 estrous periods from eight animals. Animals came in estrus throughout the year. The estrous cycles corresponding to single ovarian cycles ranged from 11 to 38 days with a mode interval of 20 days, averaged 21.5 +/- 4.7 days. Percentage of the cycles within a range of a mean +/- 1 SD (17-26 days) was 79.2 %, whereas that of cycles shorter or longer than the expected range was 9.4 % and 11.4 %, respectively. Estrus took place regardless of the time of day and lasted 9 to 27 hr (19.9 +/- 4.4 hr). Ovulation occurred 6 to 21 hr (13.9 +/- 3.4 hr) after the end of estrus, with a mode interval of 12 hr. There were no significant seasonal variations in the estrus characteristics studied. 相似文献
56.
Chromosomes and sex determination of 9 species of Haemaphysalis assigned to 4 subgenera are described. H. (tAlloceraea) kitaokai possesses an XX∶XO sex chromosome system with 18 autosomes plus XX in females; 18 plus X in males. H. (Kaiseriana) hystricis has 18 +XX and 18 + XY in females and males, respectively, in most specimens, but a supernumerary chromosome is present in some individuals. A supernumerary chromosome was also observed in 1 male H. (Aborphysalis) formosensis. These two species are the second and third species of ticks reported to have supernumerary chromosomes. H. formosensis, H. (Kaiseriana) bispinosa, H. (Haemaphysalis) campanulata, H. (H.) flava, H. (H.) megaspinosa, H. (H.) japonica, and H. (H.) pentalagi possess 20 autosomes plus 2 sex chromosomes in females and 20+1 sex chromosomes in males. Phylogenetic relationships within the genus Haemaphysalis are briefly discussed. 相似文献
57.
Simple approximate expressions have been derived from the theory of Zimm and Bragg for use in the analysis of experimental data on the helix-coil transition in polypeptide. On the basis of the resulting expressions practical procedures are proposed to determine two basic parameters characterizing a thermally induced transition, i.e., helix initiation parameter σ and enthalpy change for helix formation, ΔH. They have been applied to the data for poly(β-benzyl L -aspartate) (PBLA) with the result: σ = 1.6 × 10?4 and ΔH = ?450 cal/mole for PBLA in m-cresol; σ = 0.6 × 10?4 and ΔH = 260 cal/mole for PBLA in chloroform containing 5.7 vol-% of dichloroacetic acid. This result gives evidence that σ may change not only from one polypeptide to another but also for a given polypeptide in different solvents. The change in limiting viscosity number [η] accompanying the transition was measured in the same solvents. The curve of [η] versus helical content had a relatively monotonic shape for the chloroformdichloroacetic acid solutions as compared with that for the m-cresol solutions, indicating that [η] depended largely on σ. Provided that [η] is a direct measure of the mean-square radius of gyration, 〈S2〉, the results are consistent with the theoretical predictions of Nagai and of Miller and Flory for 〈S2〉. 相似文献
58.
Zusammenfassung Wird einzelligen Algen (Ankistrodesmus braunii) nach Vorbelichtung in anschließender Dunkelheit 32P-markiertes Phosphat geboten, so tritt gegenüber Dauerdunkel eine erhebliche Förderung der 32P-Einlagerung auf. Die nach Vorbelichtung bestimmte Markierung der aufgetrennten Phosphatfraktionen ähnelt sehr derjenigen im Dauerlicht. Die erhöhte Dunkelphosphorylierung nach Vorbelichtung hängt von der CO2-Konzentration, von der Lichtintensität und der Zeit der Vorbelichtung ab. Unter den vorliegenden Bedingungen waren 7 min Vorbelichtung zur maximalen Förderung nötig. Die Halbwertzeit des Abklingens betrug etwa 4 min.Aus den Experimenten geht hervor, daß durch die Belichtung der Algen auch in vivo ein Zustand gebildet wird, der noch nach Belichtung eine Zeitlang im Dumkeln eine Erhöhung der 32P-Einlagerung erlaubt.Es wird diskutiert, ob es sich einerseits um die Bildung einer im Licht reduzierten Substanz R handeln könnte, die für eine begrenzte Zeit in Dunkelheit noch einen cyclischen, mit Phosphorylierung gekoppelten Elektronentransport aufrechterhalten kann. Andererseits könnte durch die Vorbelichtung ein energiereiches Zwischenprodukt X
E — oder auch ein Protonenpool — gebildet werden, das bei dem Energietransfer vom Elektronentransportsystem zur ATP aufgebaut wird. Schließlich muß berücksichtigt werden, daß durch die Vorbelichtung an den Chloroplastenmembranen ein verstärkter ATP-Pi-Austausch zustande kommen könnte, der nach Belichtung nur langsam abklingt.
Abkürzungen ATP Adenosintriphosphat - ADP Adenosindiphosphat - Pi Orthophosphat - Poly-P anorganisches Polyphosphat - RNS Ribonucleinsäure - TCE Trichloressigsäure - 2,4-DNP 2,4-Dinitrophenol Stipendiat der Nishina-Gedächtnis-Stiftung (Japan) für 1963. 相似文献
Influence of preillumination on subsequent phosphorylation in the darkness of unicellular green algae (Ankistrodesmus braunii)
Summary Preilluminated unicellular green algae (Ankistrodesmus braunii) were treated in the subsequent darkness with 32PO4. The post-illumination dark incorporation was considerably increased compared with the control in continuous dark. The labeling of the separated phosphate-fractions was similar to that of continuous light. The light-induced dark incorporation depended from the light intensity as well as from the time of preillumination. A preillumination of 7 min was required for a maximal enhancement of this preillumination effect. On the other hand the effect diminished in darkness with a half life of approximately 4 min. Finally the enhancement was found to be greater in the absence of CO2 than in the presence of CO2.The experiments demonstrate the light-induced formation of a state in the algae, which permits the enhancement of 32P-incorporation into several phosphate-fractions for a limited time during subsequent darkness.It is discussed, that this may be performed through the formation of a light-reduced substance R maintaining for a limited time a cyclic electron transport in darkness, coupled with phosphorylation. On the other hand it seems possible, that preillumination induces a high energy intermediate X E—this could also be a pool of protons—formed in the course of energy-transfer from electron transport to ATP-formation. But we must consider also the possibility that light accellerates the ATP-Pi exchange on chloroplast-membranes for a time after preillumination.
Abkürzungen ATP Adenosintriphosphat - ADP Adenosindiphosphat - Pi Orthophosphat - Poly-P anorganisches Polyphosphat - RNS Ribonucleinsäure - TCE Trichloressigsäure - 2,4-DNP 2,4-Dinitrophenol Stipendiat der Nishina-Gedächtnis-Stiftung (Japan) für 1963. 相似文献
59.
Three types of tobacco (Nicotiana tabacum cv. Havana 38) callus: 1) healthy stem callus, 2) TMV-infected stem callus, 3) TMV-infected leaf callus; and leaves differentiated from healthy stem callus, and from TMV-infected leaf callus were compared for fine structure. In addition, the fine structure was observed of plastids in cells of leaves differentiated from callus isolated from stem sections of TMV-infected hybrid tobacco plants (N. tabacum cv. Havana 38 ×N. glutinosa) grown under high temperature. The cytoplasmic organelles in tissue cultured cells were similar to those in cells of greenhouse-grown tobacco plants. Except for plastids, TMV infection did not noticeably affect morphologically other cellular organelles in tissue culture cells. In TMV-infected leaf callus, numerous small bodies were seen in plastid-like bodies, while vesicle-like structures were observed in the stroma of plastids in leaves differentiated from callus of hybrid tobacco inoculated with TMV. Morphological variations of mitochondria, such as swelling and vacuolization of the inner matrix, occurred frequently in TMV-infected leaf callus. Needle-like crystalline inclusions or looped inclusions composed of many fine, long filaments were considered TMV particles orientated parallel to each other. The TMV particles were detected in the cytoplasm of tissue culture cells. 相似文献
60.