全文获取类型
收费全文 | 6213篇 |
免费 | 435篇 |
国内免费 | 6篇 |
出版年
2023年 | 36篇 |
2022年 | 68篇 |
2021年 | 164篇 |
2020年 | 73篇 |
2019年 | 107篇 |
2018年 | 149篇 |
2017年 | 128篇 |
2016年 | 222篇 |
2015年 | 238篇 |
2014年 | 310篇 |
2013年 | 410篇 |
2012年 | 441篇 |
2011年 | 414篇 |
2010年 | 246篇 |
2009年 | 222篇 |
2008年 | 284篇 |
2007年 | 301篇 |
2006年 | 220篇 |
2005年 | 232篇 |
2004年 | 206篇 |
2003年 | 167篇 |
2002年 | 171篇 |
2001年 | 144篇 |
2000年 | 131篇 |
1999年 | 105篇 |
1998年 | 49篇 |
1997年 | 45篇 |
1996年 | 38篇 |
1995年 | 47篇 |
1994年 | 41篇 |
1993年 | 30篇 |
1992年 | 92篇 |
1991年 | 71篇 |
1990年 | 88篇 |
1989年 | 72篇 |
1988年 | 81篇 |
1987年 | 75篇 |
1986年 | 73篇 |
1985年 | 67篇 |
1984年 | 59篇 |
1983年 | 33篇 |
1981年 | 28篇 |
1980年 | 36篇 |
1979年 | 45篇 |
1978年 | 32篇 |
1977年 | 35篇 |
1976年 | 35篇 |
1974年 | 31篇 |
1973年 | 33篇 |
1972年 | 31篇 |
排序方式: 共有6654条查询结果,搜索用时 15 毫秒
161.
Summary A strain of Aspergillus niger was grown in still (liquid), shake and semi-solid fermentation for calcium gluconate production from glucose, starch, or molasses. The yield from glucose or starch hydrolysate was acceptably high in both shake and semi-solid fermentation indicating that the semi-solid fermentation process offers a promising practical alternative. 相似文献
162.
A hepatic membrane-associated factor stimulates nuclear DNA synthesis in cultured fibroblastic cells
Subal Bishayee Manjusri Das 《Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression》1982,696(2):134-138
Nuclear DNA replication in cultured mouse fibroblasts is stimulated by isolated hepatic plasma membranes in a time- and concentration-dependent manner. The plasmalemmal activity is susceptible to trypsin treatment, and to treatment with protein modifying agents, N-ethylmaleimide, N-bromosuccinimide, and 2-hydroxy-5-nitro-benzylbromide. 相似文献
163.
Several new peracetylated pyrimidine N-1 nucleosides containing one or two β-d-hexopyranosyl residues have been synthesized and their physical characteristics are reported. The conformation of these nucleosides has been investigated by high-resolution 13C-n.m.r. analysis after deblocking. It was possible to distinguish between the syn and anti rotamers of 3-β-d-glucopyranosyluracil, and to establish the favored anti conformation in solution of the nucleoside disaccharide, antibiotic anthelmycin. 相似文献
164.
We describe a program, CROSS, which we have written to obtain potency estimates and other parameters for bioassay data from assays of crossover design. The program permits testing of all assays for statistical validity and calculates the complete analysis of variance for assays of balanced design. The form of data input and the complete documentation of assay results make this program particularly useful for anyone carrying out crossover assays on a routine basis. The analysis of variance presented is also useful for more general biological or medical situations. 相似文献
165.
166.
A new contraceptive compound had been prepared with the common ingredients and it was applied in female rats. The efficacy and toxicity tests of this compound showed that this drug has along-acting contraceptive value not causing any side-effects. 相似文献
167.
Rabbits were immunised againstEscherichia coli ribosomes and the partially purified immunoglobulin G fraction had maximum ability to precipitate the ribosomes as well as
the extracted ribosomal proteins. By digestion of immuno-globulin G with papain, monovalent Fab fragments were produced. The
70 S ribosome and its subunits (50 S and 30 S) were separately treated with Fab and then tested in the kinetic assay of degradation
of ribosomes by ribonuclease I at various Mg2+ concentrations. Treated ribosomes and their subunits were degraded at faster rates than the nontreated ones; the rates in
both the control and the treated cases were dependent on the concentration of Mg2+. These results indicate the unfolding of the structure of the ribosome on treatment with antibody fragments, which may be
due to the weakening of the interaction between rRNAs and ribosomal proteins. 相似文献
168.
A case of spontaneous segregation of a heterozygous diploid was observed withAspergillus niger, giving rise to a somatic recombinant. Assuming an independence of markers, its genotype is suggested to bebrw+lys pab+brw lys+pab. 相似文献
169.
Synthesis of proteins rich in lysine declines progressively with endosperm development and these proteins appear to be degraded preferentially at later stages. The proteolytic enzymes in extracts of endosperms at a late stage of development release considerably more lysine radioactivity from labelled endosperm proteins as compared with the enzymes in endosperms at an early stage. 相似文献
170.
Selenium availability in berseem (Trifolium alexandrinum) as affected by selenium and phosphorus application 总被引:1,自引:0,他引:1
Summary The effect of selenium and phosphorus application on Berseem (Trifolium alexandrium) was studied in the green house. Each dose of selenium from O to 16 ppm decreased the dry matter yield of Berseem significantly at all the levels of applied phosphorus. Phosphorus stimulated the dry matter yield at all levels of selenium. Yields in the second cutting were of a higher order than in the first cut. Selenium application increased selenium and phosphorus content in Berseem, but at 8 and 16 ppm of selenium the phosphorus content decreased significantly. Sulphur concentration decreased with selenium application but application of phosphorus increased sulphur concentration showing synergetic effect.Studies on residual effect of selenium revealed that the application of 50 ppm of phosphorus increased the yield while that of 100 ppm decreased it. Selenium concentration which increased with increasing phosphorus was many fold higher in the first cutting than in the second cutting and similar was the trend with phosphorus and sulphur. 相似文献