全文获取类型
收费全文 | 3462篇 |
免费 | 196篇 |
出版年
2022年 | 26篇 |
2021年 | 63篇 |
2020年 | 34篇 |
2019年 | 54篇 |
2018年 | 56篇 |
2017年 | 62篇 |
2016年 | 83篇 |
2015年 | 117篇 |
2014年 | 133篇 |
2013年 | 163篇 |
2012年 | 237篇 |
2011年 | 206篇 |
2010年 | 131篇 |
2009年 | 108篇 |
2008年 | 153篇 |
2007年 | 130篇 |
2006年 | 126篇 |
2005年 | 118篇 |
2004年 | 101篇 |
2003年 | 78篇 |
2002年 | 85篇 |
2001年 | 89篇 |
2000年 | 63篇 |
1999年 | 70篇 |
1998年 | 29篇 |
1997年 | 30篇 |
1996年 | 25篇 |
1995年 | 24篇 |
1992年 | 50篇 |
1991年 | 61篇 |
1990年 | 45篇 |
1989年 | 55篇 |
1988年 | 39篇 |
1987年 | 48篇 |
1986年 | 31篇 |
1985年 | 73篇 |
1984年 | 46篇 |
1983年 | 51篇 |
1982年 | 24篇 |
1981年 | 29篇 |
1980年 | 41篇 |
1979年 | 53篇 |
1978年 | 33篇 |
1976年 | 25篇 |
1975年 | 27篇 |
1974年 | 32篇 |
1973年 | 28篇 |
1971年 | 34篇 |
1970年 | 29篇 |
1969年 | 33篇 |
排序方式: 共有3658条查询结果,搜索用时 750 毫秒
121.
M Srivastava O W McBride P J Fleming H B Pollard A L Burns 《The Journal of biological chemistry》1990,265(25):14922-14931
122.
Glutathione S-transferases of the bovine retina. Evidence that glutathione peroxidase activity is the result of glutathione S-transferase. 下载免费PDF全文
We have purified two isoenzymes of glutathione S-transferase from bovine retina to apparent homogeneity through a combination of gel-filtration chromatography, affinity chromatography and isoelectric focusing. The more anionic (pI = 6.34) and less anionic (pI = 6.87) isoenzymes were comparable with respect to kinetic and structural parameters. The Km for both substrates, reduced glutathione and 1-chloro-2,4-dinitrobenzene, bilirubin inhibition of glutathione conjugation to 1-chloro-2,4-dinitrobenzene, 1-chloro-2,4-dinitrobenzene inactivation of enzyme activity and molecular weight were similar. However, pH optimum and energy of activation were found to differ considerably. Retina was found to have no selenium-dependent glutathione peroxidase activity. The total glutathione peroxidase activity fractionated with the transferases in the gel-filtration range of mol.wt. 49000 and expressed activity with only organic hydroperoxides as substrate. Only the more anionic isoenzyme expressed both transferase and peroxidase activity. 相似文献
123.
H.S. Srivastava 《Phytochemistry》1980,19(5):725-733
Nitrate reductase is one of the most important enzymes in the assimilation of exogenous nitrate—the predominant form of nitrogen available to green plants growing in soil. Activity of this enzyme in plants gives a good estimate of the nitrogen status of the plant and is very often correlated with growth and yield. Although it is difficult to explain the physiological significance and the mechanism of effects of several factors on the enzyme activity, in some cases suitable postulates have been advanced. In general, the enzyme activity in a plant tissue is a balance between its relative rates of synthesis/degradation and activation/inactivation. Factors may affect the overall activity by interfering with either of these processes. 相似文献
124.
The uptake of leucine through the tegument of Cotugnia digonopora, a cestode found in the fowl intestine, occurs by a process of active transport. The Kt of transport is 0.87 mM and the Vmax is 0.223 μmol/min/g. Uptake of the amino acid is competitively inhibited by valine (Kt = 1.30 mM). Potassium cyanide and 2,4-dinitrophenol do not completely block the entry of leucine into the parasite. 相似文献
125.
An investigation into the role of SH1 and SH2 groups of myosin in calcium binding and tension generation 总被引:2,自引:0,他引:2
S Srivastava J Wikman-Coffelt 《Biochemical and biophysical research communications》1980,92(4):1383-1388
Myosin heavy chains influence the Ca2+ binding properties of the light chains. When the SH1 + SH2 moieties of myosin, located on heavy meromyosin S-1, are blocked, myosin loses its Ca2+ binding capabilities. Furthermore, (SH1 + SH2)-blocked myosin no longer expresses tension when analyzed as modified actomyosin threads. When the SH1 moiety of myosin is blocked, myosin continues to express normal Ca2+ binding properties as well as normal tension. 相似文献
126.
Transmission electron microscopy of thin sections of two mesophilic and a psychrophilic Rhodotorula rubra revealed structures normally associated with yeast. The capsule of all three strains was thicker in the cells grown in glucose than those grown in glucose-free media. The cell wall of all three strains showed more lamellae in the cells grown in a medium containing glycerol. Budding was of the Rhodoturula type. Endoplasmic reticula running parallel to the nucleus were commonly observed in the psychrophiles but not in the mesophiles. In the psychrophile, in association with the plasmalemma, lomasomes and plasmalemmasomes were observed. Giant mitochondria were commonly seen in the cells grown in a fermentable carbohydrate-free medium. Vacuoles were mostly empty. 相似文献
127.
128.
129.
A strain of Fusarium solani (Mart.) Sacc. (IMI-216517), isolated from a patient of mycotic keratitis, produced experimental keratomycosis in albino rabbit cornea and survived in internal tissues of albino mice for varying periods. Alantolactone, isolated from the plant — Inula racemosa Hook. f. exhibited marked in vitro fungistatic activity against this strain of F. solani at 100–200 g/ml concentrations. The strain was less sensitive to amphotericin B and showed more acid than alkaline proteinase and phosphatase activities.Communication No. 2526. 相似文献
130.
S. R. Akruk A. A. Farooqui William L. Williams P. N. Srivastava 《Molecular reproduction and development》1979,2(1):1-13
Significant release of the acrosomal enzymes arylsulfatase, β-N-acetylhexosaminidase and hyaluronidase was observed following the treatment of ejaculated rabbit spermatozoa for 12 hours in 20% rabbit serum for inducing in vitro capacitation, and these sperm were capable of in vivo fertilization; however, the treatment of sperm for 15 minutes in high ionic strength (380 mOsm/kg) or low ionic strength medium (305 mOsm/kg) for in vitro capacitation did not result in any significant release of the above enzymes nor were the sperm capable of in vivo fertilization. Serum-treated spermatozoa remained significantly motile following the 12 hour treatment, 51% underwent the acrosome reaction and were capable of fertilizing 66% of the ova in vivo. Identical serum treatment of lysosomes from rabbit liver resulted in a comparable release of the lysosomal enzymes. Serum treatment for in vitro capacitation resulted in vesiculation of the anterior margin of half the spermatozoa, but left their inner acrosomal membranes and equatorial segments intact. A biochemical relationship between the release of acrosomal enzymes and capacitation is suggested. 相似文献