全文获取类型
收费全文 | 1747篇 |
免费 | 120篇 |
出版年
2021年 | 12篇 |
2020年 | 9篇 |
2019年 | 13篇 |
2018年 | 23篇 |
2017年 | 11篇 |
2016年 | 17篇 |
2015年 | 28篇 |
2014年 | 41篇 |
2013年 | 106篇 |
2012年 | 79篇 |
2011年 | 67篇 |
2010年 | 44篇 |
2009年 | 55篇 |
2008年 | 70篇 |
2007年 | 64篇 |
2006年 | 91篇 |
2005年 | 97篇 |
2004年 | 111篇 |
2003年 | 133篇 |
2002年 | 105篇 |
2001年 | 23篇 |
2000年 | 30篇 |
1999年 | 30篇 |
1998年 | 33篇 |
1997年 | 28篇 |
1996年 | 29篇 |
1995年 | 27篇 |
1994年 | 18篇 |
1993年 | 15篇 |
1992年 | 31篇 |
1991年 | 22篇 |
1990年 | 27篇 |
1989年 | 25篇 |
1988年 | 21篇 |
1987年 | 19篇 |
1986年 | 24篇 |
1985年 | 25篇 |
1984年 | 21篇 |
1983年 | 20篇 |
1982年 | 29篇 |
1981年 | 23篇 |
1980年 | 21篇 |
1979年 | 16篇 |
1978年 | 13篇 |
1977年 | 18篇 |
1976年 | 24篇 |
1975年 | 17篇 |
1974年 | 15篇 |
1973年 | 14篇 |
1972年 | 7篇 |
排序方式: 共有1867条查询结果,搜索用时 15 毫秒
1.
To examine the differences of the growth and reproduction of different-aged plants, 0-, 1-, and 2-year plants ofAmorphophalus konjac were investigated. RGR and daily net production per unit productive part, relative net-production rate (α′), of the 0-year
plant were largest, although NAR was highest in the 2-year plant. This was due to the large LAR of the 0-year plant, owing
to its large SLA. With increase in age, LAR decreased and NAR increased. Thus, it appeared that the age of plant exerts two
opposite effects on dry-matter production. Since these effects cancel each other out, differences in RGR and α′ between the
two older plants were not significant. We estimated that plant size appears to be primarily responsible for these effects.
The 0-year plant showed the least distribution ratio of net production into reproductive (storage) organs, and the highest
productivity of the reproductive part. The ratio of the production of corm to total reproductive-part production, the D-reproduction
index, was independent of age, and critical size in vegetative propagation could not be detected. 相似文献
2.
Actin-rich spherical extrusion induced in okadaic acid-treated K562 cells by crosslinking of membrane microdomains. 总被引:1,自引:0,他引:1
Takeshi Baba Keiko Udaka Nobuo Terada Hideho Ueda Yasuhisa Fujii Shinichi Ohno Satoshi B Sato 《The journal of histochemistry and cytochemistry》2003,51(2):245-252
Interconnection between surface microdomains and the actin cytoskeleton is vital to various cellular activities. We studied the responses of okadaic acid (OKA)-treated K562 leukemia cells to crosslinking of membrane microdomains. Although OKA alone induced clustering of surface-bound F-actin, addition of a biotinylated poly(ethylene glycol) derivative of cholesterol (bPEG-Chol) and subsequent binding of streptavidin (SA) further induced accumulation of the clusters, resulting in the formation of a spherical cell extrusion. This extrusion was also induced by direct crosslinking of a raft marker, CD59, and ganglioside GM1. In addition, we found that knockout of the gene encoding Fyn kinase inhibited formation of the spherical extrusion in murine T-cells. In bPEG-Chol/SA-treated cells, CD59, ganglioside GM1, and clathrin/AP-2 were all accumulated on the surface of the actin-rich extrusion, whereas dynamin and transferrin receptors were unaffected. Intermediate filaments, mitochondria, and other vesicles also accumulated. These results suggest that crosslinking of membrane domains exaggerates the linkage between actin and a defined set of membrane proteins in OKA-treated cells. 相似文献
3.
Nobuo Takagi 《Genetica》1993,88(2-3):107-117
For the cytogenetic study of X chromosome inactivation as an X chromosome dosage compensation mechanism, we isolated a number
of XXXX, XXX, and XXY near-tetraploid mouse hybrid cell clones by fusing XX or XO embryonal carcinoma cells with lymphocytes
carrying a structurally altered X chromosome(s). The inactive X chromosome from the female lymphocyte was reactivated in these
hybrid clones which retained embryonal carcinoma morphology so far as they were cultured on the collagen-coated plastic surface
in the medium supplemented with leukemia inhibitory factor (LIF) and betamercaptoethanol (BME). Some of these clones developed
balloon-like cystic embryoid bodies when they were allowed to form cell aggregates in medium without LIF and BME in bacteriological
petri dishes to which they do not adhere. X chromosome inactivation occurring during this process detected by the incorporation
of 5-bromodeoxyuridine did not conform to the expected pattern leaving two X chromosomes active in every tetraploid cells.
This may suggest either that the X-inactivation mechanism evolved primarily, for the diploid cell is unable to deal with tetraploid
conditions efficiently, or that the present system ofin vitro differentiation represents an anomalous situation never encounteredin vivo. 相似文献
4.
Chiaki Sato Atushi Katumata Ikuo Takashima Nobuo Hashimoto 《FEMS microbiology letters》1991,80(2-3):201-206
Abstract: Genes from Chlamydia psittaci P-1041 were cloned into the Bam HI site of pUC19 and were transformed to host Escherichia coli JM109. Two recombinant plasmids that expressed protein antigens of Chlamydia were isolated. The sizes of the DNA fragments were 1350 and 1710 bp, and encoded for polypeptides of M r 25 and 42 kilodaltons (kDa), respectively. The 25-kDa protein had cross-reactivity with antisera to ten C. psittaci strains and two C. trachomatis strains, whereas the 42-kDa protein reacted only with homologous antiserum to the C. psittaci P-1041 strain. Furthermore, in Southern hybridization analysis these two fragments as probes hybridized with DNA of ten C. psittaci strains and four C. trachomatis strains. These results indicated that the two fragments shared a DNA sequence common to the chlamydial genus. 相似文献
5.
Eiji Hara Tomoko Ohshima Takako Ishii Wataru Sugino Ko Tsutsui Susumu Nakada Nobuo Tsuchida Kinichiro Oda 《Experimental cell research》1992,198(2):250-258
The mechanism of induction of DNA synthesis in quiescent rat 3Y1 cells by the adenovirus E1A gene was investigated using the 3Y1 derivative cell lines g12-21, gn12RB1, and gn12RB2. The g12-21 cells express the E1A 12S cDNA and the latter two cells express both the E1A 12S cDNA and the human retinoblastoma susceptibility (Rb) gene at different levels in response to dexamethasone (dex). The cDNA sequences of E1A-inducible cell cycle-dependent genes, clone 3 and clone 16, were isolated by differential screening of a cDNA library constructed from dex-treated g12-21 cells. The quiescent 3Y1 cells induced c-fos and c-myc expression within 2 h after serum stimulation and expressed clone 16 and clone 3 transiently at around 8 h before the onset of DNA synthesis (10 h). In contrast, the quiescent g12-21 cells treated with dex expressed a high level of E1A at 6 to 8 h after treatment and expressed clone 16 and clone 3 at around 8 h without stimulation of c-fos and c-myc expression, suggesting that E1A bypasses the cell cycle early in G1. The half-maximal rate of DNA synthesis was reached in a much shorter time in dex-treated g12-21 cells (12 h) than in serum-treated 3Y1 cells (18 h), suggesting that E1A also bypasses the cell cycle at the G1/S boundary. The gn12RB1 and gn12RB2 cells were unable to induce DNA synthesis in response to dex presumably due to lower levels of E1A expression, although gn12RB2 but not gn12RB1 cells could express clone 16 and clone 3. These results suggest that the level of E1A required for bypass at the G1/S boundary is higher than that required early in G1. 相似文献
6.
Jun Ishizaki Mikio Tamaki Masaru Shin Hiroshige Tsuzuki Kazumasa Yoshikawa Hiroshi Teraoka Nobuo Yoshida 《Applied microbiology and biotechnology》1992,36(4):483-486
Summary Recombinant human glucagon was succesfully produced with a high level of expression in Escherichia coli as a fusion protein with human interferon . The synthetic gene was designed to release glucagon, which does not contain glutamic acid residues, from fusion protein with the Staphylococcus aureus strain V8 protease that specifically cleaves the peptide bond on the carboxyl side of the glutamic acid residue. The resulting glucagon was purified to homogeneity by a combination of C18 reverse-phase HPLC and ion-exchange HPLC. The yield of intact glucagon obtained from 11 of culture was approximately 12 mg. The structure of recombinant human glucagon was confirmed by HPLC and amino acid composition/sequence analyses.
Offprint requests to: J. Ishizaki 相似文献
7.
Summary (±)-Tricarbonyl 6-3-methylbenzyl alcohol)chromium was resolved to of 100%e.e. and of 92%e.e. by lipase-catalyzed transesterifications arranged in homotopic and heterotopic double resolutions. 相似文献
8.
9.
Etsuko Kobayashi Yasushi Suwazono Mirei Dochi Ryumon Honda Teruhiko Kido Hideaki Nakagawa 《Biological trace element research》2009,129(1-3):46-57
This study was undertaken to estimate the amount of cadmium (Cd) exposure needed for the development of Itai-itai disease and the influence of using Jinzu River water for drinking and/or cooking on its development. The subjects comprised 38 Itai-itai disease patients admitted both for questionnaire survey and medical testing. The period when the patients started to perceive leg/back pain was defined as ‘mild disease onset’ and that when they experienced the most severe manifestations such as ambulatory disturbance as ‘severe disease onset’. In a comparison of non-users/users of river water, mean age and lifetime Cd intake (LCd) estimated from the daily consumption of rice and other foods at the onset of mild or severe disease showed smaller values in the users than non-users. LCd in non-users/users of river water for drinking and/or cooking were estimated as 3.46–3.60 g/2.58–2.63 g at mild disease onset and 4.24–4.44 g/3.50–3.54 g at severe disease onset. A portion of the differences in LCd in non-users/users is attributable to the influence of Cd consumption from the use of river water, although it was suggested that LCd estimated from eating Cd-polluted rice exerted a greater influence on the development of Itai-itai disease than drinking and/or cooking with Cd-polluted river water. 相似文献
10.
Theoretical models on the movement of colonial animals predict that neighbouring colonies may segregate their foraging areas, and many seabird studies have reported the presence of such segregations. However, these studies have often lacked the appropriate null model to test the effect of neighbouring colonies on foraging areas, especially in small colonies or in short‐ranging species. Here, we examined the foraging areas of Adélie Penguins Pygoscelis adeliae from two neighbouring (2 km apart) colonies by using bird‐borne GPS loggers. The field study was conducted at Hukuro Cove colony (104 pairs) and Mizukuguri Cove colony (338 pairs) in Lützow‐Holm Bay, East Antarctica. We obtained GPS tracks for 504 foraging trips from 48 chick‐rearing Adélie Penguins and quantified the degree of overlap in the foraging areas between two colonies. We also produced simulated movement tracks by using correlated random‐walks assuming no inter‐colony competition and quantified the degree of overlap in the simulated foraging areas. Finally, we compared the results from real GPS tracks with those from simulated tracks to examine the effect of neighbouring colonies on Adélie Penguin movement. The results indicate that the degree of overlap was significantly smaller in real tracks than in simulated tracks. In real tracks, the foraging area of the smaller Hukuro Cove colony extended to the other side of the larger Mizukuguri Cove colony, unlike in simulated tracks. Consequently, we suggest that Adélie Penguins from two neighbouring colonies segregated their foraging areas and that the larger colony appeared to affect the foraging area of the smaller colony. 相似文献