全文获取类型
收费全文 | 2711篇 |
免费 | 114篇 |
国内免费 | 3篇 |
专业分类
2828篇 |
出版年
2022年 | 8篇 |
2021年 | 22篇 |
2019年 | 15篇 |
2018年 | 23篇 |
2017年 | 16篇 |
2016年 | 42篇 |
2015年 | 57篇 |
2014年 | 92篇 |
2013年 | 171篇 |
2012年 | 161篇 |
2011年 | 156篇 |
2010年 | 91篇 |
2009年 | 111篇 |
2008年 | 161篇 |
2007年 | 169篇 |
2006年 | 153篇 |
2005年 | 163篇 |
2004年 | 184篇 |
2003年 | 186篇 |
2002年 | 154篇 |
2001年 | 26篇 |
2000年 | 24篇 |
1999年 | 40篇 |
1998年 | 58篇 |
1997年 | 37篇 |
1996年 | 38篇 |
1995年 | 46篇 |
1994年 | 36篇 |
1993年 | 39篇 |
1992年 | 20篇 |
1991年 | 23篇 |
1990年 | 26篇 |
1989年 | 16篇 |
1988年 | 16篇 |
1987年 | 19篇 |
1986年 | 13篇 |
1985年 | 13篇 |
1984年 | 24篇 |
1983年 | 13篇 |
1982年 | 32篇 |
1981年 | 22篇 |
1980年 | 26篇 |
1979年 | 15篇 |
1978年 | 11篇 |
1977年 | 16篇 |
1976年 | 8篇 |
1975年 | 9篇 |
1973年 | 5篇 |
1971年 | 4篇 |
1969年 | 3篇 |
排序方式: 共有2828条查询结果,搜索用时 15 毫秒
1.
Hoshino Atsushi; Abe Yukihide; Saito Norio; Inagaki Yoshishige; Iida Shigeru 《Plant & cell physiology》1997,38(8):970-974
The Japanese morning glory carrying the recessive mutable speckledallele with the dominant speckled-activator bears colorlessflowers with fine and round colored spots distributed over thecorolla whereas the plant without the speckled-activator producespale yellow flowers. Previous chemical analysis has indicatedthat a mutation in the gene for flavanone 3-hydroxylase (F3H)is a likely candidate for the speckled allele. However, theF3HmRNA without sequence alteration accumulates normally inthe pale yellow flowers, indicating that the speckled alleleis neither the F3H gene nor a regulatory gene acting on theF3H gene expression. (Received April 4, 1997; Accepted June 2, 1997) 相似文献
2.
Xiuyun Ye Shigeru Yoshida T. B. Ng 《The international journal of biochemistry & cell biology》2000,32(11-12)
A mild and rapid method is described for isolating various milk proteins from bovine rennet whey. β-Lactoglobulin from bovine rennet whey was easily adsorbed on and desorbed from a weak anion exchanger, diethylaminoethyl-Toyopearl. However, α-lactalbumin could not be adsorbed onto the resin. α-Lactalbumin and β-lactoglobulin from rennet whey could also be adsorbed and separated using a strong anion exchanger, quaternary aminoethyl-Toyopearl. The rennet whey was passed through a strong cation exchanger, sulphopropyl-Toyopearl, to separate lactoperoxidase and lactoferrin. α-Lactalbumin and β-lactoglobulin were adsorbed onto quaternary aminoethyl-Toyopearl. α-Lactalbumin was eluted using a linear (0–0.15 M) concentration gradient of NaCl in 0.05 M Tris–HCl buffer (pH 8.5). Subsequently, β-lactoglobulin B and β-lactoglobulin A were eluted from the column with 0.05 M Tris–HCl (pH 6.8), using a linear (0.1–0.25 M) concentration gradient of NaCl. The yields were 1260 mg α-lactalbumin, 1290 mg β-lactoglobulin B and 2280 mg β-lactoglobulin A from 1 l rennet whey. 相似文献
3.
The major glycoproteins of horse and swine erythrocyte membranes were isolated and examined chemically and immunologically. The major glycoprotein of horse erythrocyte membranes had a molecular weight of 33 000 and consisted of 46.2% protein and 53.8% carbohydrate, of which 9.4% was hexose, 10.1% hexosamine and 33.7% sialic acid. This glycoprotein was associated with activity for the infectious mononucleosis heterophile antigen.There were two different major glycoproteins in swine erythrocyte membranes. One major glycoprotein had a molecular weight of 46 200 and consisted of 34.2% protein and 65.8% carbohydrate, of which 18% was hexose, 19% hexosamine and 27.2% sialic acid. This glycoprotein had phytohemagglutinin (Phaseolus vulgaris) binding activity. The other glycoprotein had a molecular weight of 29 000 and consisted of 50.4% protein and 49.6% carbohydrate, of which 6.4% was hexose, 7.0% hexosamine and 36.3% sialic acid. This glycoprotein had weak or absent phytohemagglutinin binding activity. 相似文献
4.
The degree of methylation at the c-myc proto-oncogene was found to change in human lymphoproliferative diseases, when examined using a methylation-sensitive restriction enzyme. In peripheral blood mononuclear cells (PBMC) c-myc DNA showed hypomethylation in human lymphoproliferative diseases, in comparison to normal subjects matched in age and sex. In cases of chronic lymphocytic leukemia (CLL), the change was amplified in the crisis. When the DNA was examined at the actin gene, no significant change was observed. The results suggest that the change in c-myc proto-oncogene methylation might become an important clue in understanding the relationship between levels of gene expression and methylation in human lymphoproliferative diseases. 相似文献
5.
The effects of defoliation treatments on plant growth in sunflower (Helianthus annuus) were studied in the field. Four defoliation treatments, 0 (control), 37.4, 56.1 and 93.4% of the total leaf dry weight,
were applied to plants that had small third leaves. Decreased leaf weight/whole plant weight (F/W) ratios in defoliated plants
rapidly recovered to almost the same ratio as that observed in the control within 12 to 16 days after defoliation according
to the degree of defoliation. The mechanism involved in the recovery of the F/W ratio in defoliated plants mainly consisted
of three parameters: enhancement of (1) carbon distribution ratios in the leaves, (2) photosynthetic activity in the remaining
leaves, and (3) retranslocation of carbon from the stem and/or roots to leaves.
Inhibitive effects of defoliation on relative growth rate and net assimilation rate were seen at an early stage, but subsequently
both rates became larger in defoliated plants than in controls. Defoliated plants tended to show rapid development and expansion
of new leaves, and to show increased specific leaf area and protein synthesis in individual leaves. The sugar content of leaves
in defoliated plants was higher than that in controls, while the content in both stem and roots was lower. These responses
seem to be advantageous for development of the photosynthetic system. Heights of defoliated plants were clearly depressed
according to the degree of defoliation, and this was attributed largely to differences in the elongation rates of the internodes
resulting from defoliation. 相似文献
6.
Summary In order to assess the capacity of neural crest from different sources to participate in thymic development, neural crest from selected axial levels was transplanted unilaterally from quail donors to the region in chick hosts from which neural crest cells normaly migrate to interact with the primordial thymus. The greatest representation of donor cells was observed after isotopic transplantation and when donor tissue was taken from the hyoid and mesencephalic regions of the neural crest. The capacity for transplants to contribute cells decreased both anteriorly and posteriorly, so that neural crest close to the usual origin of mesenchyme-producing cells contributed a larger number of donor cells around the developing thymus than neural crest from anterior and posterior regions. Cells from the transplant were inserted as an addition to the host chick cells. Thus, a special relationship and capacity for interaction in thymic development is expressed by neural crest at usual levels over a limited span of axial regions, but to some extent by all regions. This study has established that the capacity for neural crest cells from different axial levels to interact with developing organs is not uniform, but may vary, depending upon the nature of the interaction with a particular organ.This study was supported by Grant No. 2332, The Council for Tobacco Research, USA, Inc. 相似文献
7.
Shigeru Yoshida 《Molecular reproduction and development》1986,13(4):309-316
Effects of the organic Ca antagonist diltiazem on Ca channels were studied in ovulated and unfertilized oocytes of the mouse by using intracellular recording techniques. The resting potential was not affected by diltiazem. The threshold level of the Ca action potential shifted slightly toward positive voltages with diltiazem concentration, but the shift was not statistically significant. The overshoot and maximum rate of rise of the Ca action potential were inhibited by the drug in a dose-dependent manner, but higher amounts of diltiazem were necessary to cause similar blocking effects on Ca channels in mouse oocytes than in other differentiated cells. Increases of external concentration of Ca2+ antagonized the degree of diltiazem inhibition. However, the sequence of block of Ca2+, Sr2+, and Ba2+ currents was different for diltiazem vs Cd2+. It is suggested that diltiazem inhibition can not be explained by simple competitive scheme, ie, antagonism between diltiazem and permeant cations does not occur at the same binding site associated with the Ca channel in mouse oocytes. 相似文献
8.
Shigeru Kimura 《Biochemical genetics》1983,21(7-8):713-724
The genetics of hemolymph alpha-mannosidase was investigated in the silkworm, Bombyx mori. By selecting individuals showing either high or low enzyme activities, homozygotes were separated, with activities varying about five-fold. No differences in the activities of beta-galactosidase and beta-N-acetylglucosaminidase were observed. Thus, it seems that high- and low-enzyme silkworms (High and Low Lines) share the same genetic background except for the gene concerning the activity of alpha-mannosidase. The synthesis of the enzyme is controlled by an autosomal allele. Furthermore, expression of the gene varies from tissue to tissue, and there is no correlation between enzyme activity and growth rate. The difference in activity between High and Low lines is due to the amount of active enzyme, not to an endogeneous activator or inhibitor. There was no isozymic difference in alpha-mannosidase. 相似文献
9.
Masao Kawai Kenji Yoshiba Shigeru Ando Shigeru Azuma 《Primates; journal of primatology》1968,9(1-2):1-12
The social behavior pattern of a solitary male at Koshima was studied by means of radio-telemetry. The relationship between the solitary males and the troop was estimated from radio-tracking data of the former's location and movement, and by direct observation of the latter at each corresponding hour.For most of day, the solitary male stayed within a distance of about 20 to 150 m from the central part of the troop, occasionally approaching it. His movement also was synchronized with that of the troop. For two nights, the solitary male slept at places which were about 200 m from the sleeping sites of the troop and faced them across the beach. The relationship between the solitary male and the troop did not seem to be strongly antagonistic.It can be assumed that the solitary male was moving according to certain pre-determined relationships or social contacts with the troop. The example of this solitary male shows the existence of the solitary male that follows and maintains contact with the troop, even outside the copulatory season.This study was sponsored by Scientific Research Grant No. 91620 of the Ministry of Education to the Japan Monkey Centre. 相似文献
10.
Interconversion of polyamines in wild-type strains and mutants of yeasts and the effects of polyamines on their growth 总被引:1,自引:0,他引:1
Koei Hamana Shigeru Matsuzaki Kohei Hosaka Satoshi Yamashita 《FEMS microbiology letters》1989,61(1-2):231-236
Yeasts of wild-type strains, such as Saccharomyces cerevisiae, Schizosaccharomyces pombe and Candida albicans were shown to have the ability to form aminopropylcadaverine and aminopropylhomospermidine from cadaverine and homospermidine, respectively. A polyamine autotroph S. cerevisiae 179-5, which lacks ornithine decarboxylase, produced both aminopropylcadaverine and aminopropylhomospermidine, while another mutant S. cerevisiae Y 260 A, which lacks spermine synthase, formed only aminopropylcadaverine. Naturally-occurring triamines and tetraamines except norspermidine and norspermine stimulated the growth of S. cerevisiae 179-5. All the six aliphatic diamines with carbon chain length ranging from one to six were effective in activating the growth of S. cerevisiae 179-5, though all of them were not converted to either triamines or tetraamines. 相似文献