全文获取类型
收费全文 | 5134篇 |
免费 | 320篇 |
国内免费 | 3篇 |
专业分类
5457篇 |
出版年
2022年 | 26篇 |
2021年 | 56篇 |
2020年 | 24篇 |
2019年 | 62篇 |
2018年 | 50篇 |
2017年 | 70篇 |
2016年 | 93篇 |
2015年 | 145篇 |
2014年 | 175篇 |
2013年 | 306篇 |
2012年 | 296篇 |
2011年 | 315篇 |
2010年 | 169篇 |
2009年 | 188篇 |
2008年 | 296篇 |
2007年 | 269篇 |
2006年 | 248篇 |
2005年 | 266篇 |
2004年 | 270篇 |
2003年 | 240篇 |
2002年 | 231篇 |
2001年 | 154篇 |
2000年 | 142篇 |
1999年 | 111篇 |
1998年 | 66篇 |
1997年 | 49篇 |
1996年 | 61篇 |
1995年 | 53篇 |
1994年 | 48篇 |
1993年 | 40篇 |
1992年 | 87篇 |
1991年 | 89篇 |
1990年 | 81篇 |
1989年 | 59篇 |
1988年 | 59篇 |
1987年 | 54篇 |
1986年 | 44篇 |
1985年 | 30篇 |
1984年 | 49篇 |
1983年 | 32篇 |
1982年 | 35篇 |
1981年 | 27篇 |
1980年 | 21篇 |
1979年 | 30篇 |
1978年 | 26篇 |
1977年 | 24篇 |
1976年 | 28篇 |
1974年 | 25篇 |
1973年 | 24篇 |
1972年 | 22篇 |
排序方式: 共有5457条查询结果,搜索用时 15 毫秒
91.
92.
93.
Shiro Higashi Akinori Nakashima Hideki Ozaki Mikiko Abe Toshiki Uchiumi 《Journal of plant research》1993,106(1):47-54
The process of digestion of captured feeds in a pitcher, an insect-trapping organ, ofNepenthes was studied. Changes in bacterial population, pH and NH4
+ concentrations in pitcher juice were examined. Strong activities of both acid- and alkaline phosphatase, phosphoamidase,
esterase C4 and esterase C8 were found in the pitcher juice. Optimum pH of proteases in the juice and those secreted from
bacteria showed pH 3.0 and pH 8.0–9.0, respectively. Twenty six strains of bacteria were isolated from 4 pitchers: 10 strains
were gram positive, 16 strains were gram negative (10 strains had casein hydrolase activity). A proton excretion was induced
by NH4
+ released from the added solutions, and accordingly, the pH of the solutions fell. As a simulation model of the digestion
process of feeds in pitcher juice and polypeptone solution was added into the washed pitcher. A good correlation was found
among the NH4
+ concentration, pH and bacterial cell titer. 相似文献
94.
95.
Excretory and secretory (ES) products collected from adult worms of Strongyloides ratti stimulated interleukin-3 (IL-3) production with mesenteric lymph node cells from infected C57BL/6 mice, but not with normal mesenteric lymph node cells. The IL-3 stimulating components were not major IgG binding antigens. Activity of the IL-3 stimulating components was stable by treatment with protease, although reduced by heating in boiling water. 相似文献
96.
Gesche Heiss Natalie Trachtmann Yoshikatsu Abe Masahiro Takeo Hans-Joachim Knackmuss 《Applied microbiology》2003,69(5):2748-2754
Rhodococcus (opacus) erythropolis HL PM-1 grows on 2,4,6-trinitrophenol or 2,4-dinitrophenol (2,4-DNP) as a sole nitrogen source. The NADPH-dependent F420 reductase (NDFR; encoded by npdG) and the hydride transferase II (HTII; encoded by npdI) of the strain were previously shown to convert both nitrophenols to their respective hydride Meisenheimer complexes. In the present study, npdG and npdI were amplified from six 2,4-DNP degrading Rhodococcus spp. The genes showed sequence similarities of 86 to 99% to the respective npd genes of strain HL PM-1. Heterologous expression of the npdG and npdI genes showed that they were involved in 2,4-DNP degradation. Sequence analyses of both the NDFRs and the HTIIs revealed conserved domains which may be involved in binding of NADPH or F420. Phylogenetic analyses of the NDFRs showed that they represent a new group in the family of F420-dependent NADPH reductases. Phylogenetic analyses of the HTIIs revealed that they form an additional group in the family of F420-dependent glucose-6-phosphate dehydrogenases and F420-dependent N5,N10-methylenetetrahydromethanopterin reductases. Thus, the NDFRs and the HTIIs may each represent a novel group of F420-dependent enzymes involved in catabolism. 相似文献
97.
98.
99.
Summary Effect of intraperitoneal administration (5 mmol/kg of body weight) of glucose- cysteine adduct (glc-cys) as a cysteine prodrug in rat tissues was studied. Cysteine levels in liver and kidney increased to 1.08 and 1.98mol per g or ml, respectively, at 2h after the administration. GSH levels did not change substantially. However, when glc-cys was injected to rats treated with diethyl maleate, a GSH-depleting agent, the decreased GSH levels were restored rapidly. The recoveries in liver and kidney were 72% at 1h and 66% at 2h, respectively, after glc-cys administration. Metabolism of glc-cys was assessed by urinary excretion of glc-cys, sulfate and taurine. Average excretion of glc-cys was 2.86mmol/kg/24h after glc-cys administration. Increased excretions of sulfate and taurine were 0.77 and 0.14mmol/kg/24h, respectively. Data show that, although glc-cys excretion was relatively rapid, glc-cys was effectively utilized for GSH synthesis in GSH-depleted tissues. 相似文献
100.
Polymerase chain reaction-directed mitochondria (mt) and microsatellite DNA analyses were performed to examine the kin structure in a spring population of grey-sided voles Clethrionomys rufocanus in Hokkaido, Japan. The spatial distribution of 81 voles in a trapping grid (about 1 ha) was estimated by using the catch-mark-release method. DNA samples were extracted from the toes clipped for individual identification. Maternal lineages of voles were unequivocally determined by the mtDNA haplotypes, as identified by nucleotide sequencing of the control region. Relatedness between individuals was estimated based on the genotype and allele frequencies at several microsatellite loci. Although the distribution of voles was uniform within the grid, neighbouring females were frequently from the same maternal lineage. Relatedness values between females correlated negatively with geographical distances. Combination of the two molecular markers revealed four clusters of closely related, matrilineal females in the population, whereas no such cluster was apparent in males. The present study first demonstrated a sex-related spatial kin structure in a natural population of the grey-sided vole. 相似文献