全文获取类型
收费全文 | 12392篇 |
免费 | 740篇 |
国内免费 | 5篇 |
专业分类
13137篇 |
出版年
2022年 | 156篇 |
2021年 | 284篇 |
2020年 | 160篇 |
2019年 | 192篇 |
2018年 | 260篇 |
2017年 | 219篇 |
2016年 | 369篇 |
2015年 | 433篇 |
2014年 | 541篇 |
2013年 | 735篇 |
2012年 | 809篇 |
2011年 | 743篇 |
2010年 | 462篇 |
2009年 | 397篇 |
2008年 | 515篇 |
2007年 | 527篇 |
2006年 | 417篇 |
2005年 | 448篇 |
2004年 | 372篇 |
2003年 | 352篇 |
2002年 | 341篇 |
2001年 | 326篇 |
2000年 | 276篇 |
1999年 | 241篇 |
1998年 | 112篇 |
1997年 | 98篇 |
1996年 | 80篇 |
1995年 | 90篇 |
1994年 | 88篇 |
1992年 | 202篇 |
1991年 | 153篇 |
1990年 | 212篇 |
1989年 | 160篇 |
1988年 | 179篇 |
1987年 | 161篇 |
1986年 | 148篇 |
1985年 | 154篇 |
1984年 | 137篇 |
1983年 | 94篇 |
1982年 | 84篇 |
1981年 | 112篇 |
1980年 | 97篇 |
1979年 | 135篇 |
1978年 | 92篇 |
1977年 | 95篇 |
1976年 | 78篇 |
1975年 | 82篇 |
1974年 | 82篇 |
1973年 | 76篇 |
1972年 | 76篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
131.
Satya Prakash Srivastava Mukul Das Prahlad K. Seth 《Chemico-biological interactions》1983,45(3):373-380
Lipid peroxidation, glutathione level and activity of glutathione-S-transferase were studied in liver and brain of rats 4 and 3 h after a single i.p. administration of 0, 25, 75, 100 mg/kg acrylamide or 0, 50, 100, 200, 600 mg/kg styrene, respectively. In liver both acrylamide and styrene caused an increase in lipid peroxidation and decrease in glutathione contents and activity of glutathione-S-transferase in a dose dependent manner, while in brain only acrylamide produced a decrease in glutathione content. The decrease in glutathione content was not always associated with increase of lipid peroxidation. The enhancement of lipid peroxidation occurred only when glutathione contents were depleted to certain critical levels. No effect of acrylamide or styrene was seen on lipid peroxidation under in vitro conditions. The addition of glutathione in the incubation mixture significantly inhibited the rate of lipid peroxidation of liver homogenates of acrylamide and styrene treated animals.The results suggest that enhancement of lipid peroxidation in liver on exposure to acrylamide or styrene is a consequence of depletion of glutathione to certain critical levels. The inhibition of glutathione-S-transferase activity by acrylamide and styrene suggests that detoxication of these neurotoxic compounds could be suppressed following acute exposure. 相似文献
132.
(Ca2+ or Mg2+)-ATPase in lung lamellar bodies 总被引:1,自引:0,他引:1
133.
Use of a New Buffer System with Formalinized Sheep Erythrocytes in the Rubella Hemagglutination-Inhibition Test 总被引:4,自引:1,他引:3 下载免费PDF全文
The increased sensitivity and improved agglutination and settling patterns of formalinized sheep erythrocytes in a new buffer, HEPES (N-2-hydroxyethylpiperazine N'-2'-ethanesulfonic acid), make this system more suitable for use in the rubella hemagglutination-inhibition test. 相似文献
134.
135.
Summary Five rates of limestone and 4 rates of fertilizers were used in a split-plot design to study their effects under field conditions
on Mo, Cu, B, Mn, and Zn levels in mixed forage tissue and soil, and on the forage yield. An increase in soil pH resulted
in an increase in Mo and Cu content of plant tissue while B, Mn, and Zn decreased. The micro-nutrient content of the tissue
increased as the harvesting season progressed. Increasing rates of applied fertilizer did not affect the micro-nutrient content
of the forage tissue or soil.
Liming to a pH of 5.6 and above reduced the availability of Mn and Zn in the soil. In general, the available B was low at
pH values greater than 6.1. Lime did not affect the quantities of Mo and Cu in the soil. Manganese is supplied in large quantities
by limestone and is not apt to be deficient in limed soil. However, addition of B and Zn may be required on the high pH soils
of Eastern Canada in future. Molybdenum was adequate where the soil was limed to a pH of 6.1 or greater.
The dry-matter yield of forage increased significantly with successive increases in lime up to pH 6.6 and with each increment
of fertilization.
Contribution No.226, Research Branch, Research Station, P.O. Box 1210, Charlottetown, P.E.I. and No.166, Experimental Farm, Nappan, N.S. 相似文献
136.
Summary In the present study attempts have been made to elucidate the composition and physiological actions of root exudates from
CB-1 Rupsail and the mixed population of these two varieties. The chemical nature of the different components of root exudates
was studied by means of paper chromatography, bioassay and other biochemical procedures. It was noted that exudates from CB-1
and Rupsail seedlings inhibited root/shoot growth of test seedlings of both varieties. But when these two varieties were grown
together root/shoot growth of both varieties were markedly promoted. Both qualitative and quantitative differences in amino
acids, carbohydrates and growth substances contents of root exudates of individual and mixed population of rice varieties
were noted. 相似文献
137.
Summary Experiments were conducted to determine the influence of N, P, and K and of the NP and NK interactions on root yields and
tissue concentrations of N, P, and K of rutabagas grown on a sandy loam soil under greenhouse conditions. Root yields were
increased by applications of N and K but not by added P. The yield response to N was dependent on K supply. The highest dry
matter content in roots was associated with the lowest rates of N and K and the lowest root yields.
The N content of tissue at the early vegetative stage increased with increasing rates of N and decreased with increasing rates
of P and K. The N content of root tissue at harvest increased at the highest rates of N but was unaffected by rates of P and
K. The P and K content of root tissue increased with increasing rates of P and K, respectively.
The levels of nutrients in early vegetative tissue associated with optimum yields were about 2.6, 0.24, and 2.0% for N, P,
and K, respectively. The corresponding values in the leaf tissue at harvest were about 1.2, 0.12, and 1.5% N, P, and K, respectively.
Contribution No.222. 相似文献
138.
139.
The 0.5M KCl wash of rabbit reticulocyte ribosomes (I fraction) catalyzes the deacylation of Met-tRNAfMet. Upon DEAE-cellulose column chromatography, the deacylase activity elutes with the 0.1M KCl wash of the column (f1) and is well-resolved from the peptide chain initiation factors (1–3). The deacylase activity is specific for Met-tRNAfMet (retic., ). Other aminoacyl tRNAs tested including fMet-tRNAfMet (retic., ), Phe-tRNA (), Val-tRNA (retic.), and Arg-tRNA (retic.) are completely resistant to the action of the deacylase. In the presence of the peptide chain initiation factor (IF1) and GTP, retic. Met-tRNAfMet forms the initiation complex Met-tRNAfMet:IF1:GTP (2), and in this ternary complex Met-tRNAfMet is not degraded by the deacylase. Met-tRNAfMet binds to IF1 independent of GTP, and in this complex, this Met-tRNAfMet is degraded by the deacylase.Prior incubation of f1 with Met-tRNAfMet (retic.) strongly inhibited protein synthesis initiation, presumably due to deacylation of the initiator tRNA. This inhibition by f1 was completely prevented when Met-tRNAfMet (retic.) was pre-incubated with peptide chain initiation factors. 相似文献
140.
I Das 《Canadian journal of biochemistry》1973,51(5):637-641