全文获取类型
收费全文 | 3628篇 |
免费 | 212篇 |
国内免费 | 1篇 |
专业分类
3841篇 |
出版年
2023年 | 30篇 |
2022年 | 61篇 |
2021年 | 81篇 |
2020年 | 53篇 |
2019年 | 55篇 |
2018年 | 79篇 |
2017年 | 74篇 |
2016年 | 99篇 |
2015年 | 135篇 |
2014年 | 148篇 |
2013年 | 212篇 |
2012年 | 227篇 |
2011年 | 231篇 |
2010年 | 182篇 |
2009年 | 113篇 |
2008年 | 159篇 |
2007年 | 194篇 |
2006年 | 152篇 |
2005年 | 139篇 |
2004年 | 117篇 |
2003年 | 92篇 |
2002年 | 79篇 |
2001年 | 68篇 |
2000年 | 64篇 |
1999年 | 58篇 |
1998年 | 26篇 |
1996年 | 20篇 |
1995年 | 28篇 |
1994年 | 26篇 |
1993年 | 29篇 |
1992年 | 43篇 |
1991年 | 37篇 |
1990年 | 29篇 |
1989年 | 41篇 |
1988年 | 38篇 |
1987年 | 43篇 |
1986年 | 53篇 |
1985年 | 33篇 |
1984年 | 47篇 |
1983年 | 32篇 |
1982年 | 29篇 |
1981年 | 30篇 |
1980年 | 32篇 |
1979年 | 40篇 |
1977年 | 46篇 |
1976年 | 21篇 |
1975年 | 27篇 |
1974年 | 31篇 |
1973年 | 21篇 |
1972年 | 22篇 |
排序方式: 共有3841条查询结果,搜索用时 0 毫秒
91.
Jagdish Ojha Narendra Mishra Mahadeo Prasad Saha Jyoti Swarup Datta Munshi 《Hydrobiologia》1979,63(2):153-159
Oxygen uptake of Channa marulius was studied under water with and without access to air. There was a significant increase in the oxygen uptake through the gills when access to air was prevented. However, this value (0.863 ± 0.058 mlO2/indiv./h) was quite low in comparison to the total bimodal oxygen uptake (2.04 ± 0.14 mlO2/indiv./h) in juveniles. In adult fish the oxygen uptake per unit time increased appreciably (4.673 ± 0.404 mlO2/indiv./h). In juveniles as well as in adults the air breathing dominated over aquatic breathing. This fish showed a definite circadian rhythm in the bimodal oxygen uptake during different hours of the day.This work was performed in the Ichthyology Laboratory, P. G. Dept. of Zoology, Bhagalpur University, and was supported by a research grant from Bhagalpur University 相似文献
92.
93.
The rat hepatic stearoyl-CoA desaturation decreased by 3.7-fold in streptozotocin-induced diabetes. Insulin treatment of diabetic rats increased the enzyme activity by 7-fold. In marked contrast to glucose administration, fructose feeding in diabetic rats resulted in 20-fold stimulation of stearoyl-CoA desaturation, although both carbohydrates stimulated stearoyl-CoA desaturation in normal rats. Measurement of the microsomal electron transfer components showed no significant changes in the NADH-cytochrome b5 reductase activity or in the concentration of cytochrome b5. However, the activity of the terminal desaturase changed in a parallel fashion as the amount of terminal desaturase reflect changes in the overall desaturation. Supplementation of various microsomes with the saturating amount of purified terminal desaturase resulted in the formation of similar amounts of catalytically active complex and increased the stearoyl-CoA desaturation to the same level suggesting that the changes in the amount of terminal desaturase reflect changes in the overall desaturation. The results support the suggestion that both insulin and the intermediates of carbohydrate metabolism are involved in the regulation of terminal desaturase. 相似文献
94.
The present study was carried out to determine the detailed histological and cytological features of the excurrent ducts of
the male reproductive system in the rhesus monkey. The excurrent ducts show a regional difference in their histological features.
The use of some of these features as histological markers and their possible functional significance are discussed.
The epithelial cells in the different components of the excurrent duct system possess cytological features which suggest their
involvement in absorption and the secretion of different products into the lumen. 相似文献
95.
The objective of this study was the preliminary characterization of the factors from mitotic HeLa cells that can induce meiotic maturation in Xenopus laevis oocytes. We found that this factor is a heat-labile, Ca2+-sensitive, nondialyzable protein with a sedimentation value of 4-5S. Furthermore, no new protein synthesis was found to be required for this mitotic factor to induce maturation in the amphibian oocytes. These data suggest that the factors involved in the breakdown of nuclear membrane and the condensation of chromosomes that are associated with three different phenomena, mitosis, meiosis, and premature chromosome condensation, are very similar in different animal species. 相似文献
96.
Summary Cowpea responded well to phosphorus and P application increased green-fodder production and P uptake. With respect to green-fodder production, the rock phosphate was found to be 50–55% as effective as superphosphate. Phosphorus when applied at 50 kg P2O5/ha as superphosphate or rock phosphate almost doubled the P uptake by the summer-season crop of cowpea as compared to no phosphorus control. The residual effect did not differ significantly on succeeding rainy-season crop of cowpea. Application of starter N increased the total green-fodder yield of two crops by 38 q/ha. re]19750710 相似文献
97.
Sodium butyrate produces reversible changes in morphology, growth rate, and enzyme activities of several mammalian cell types in culture. Some of these changes are similar to those produced by agents which increase the intracellular level of adenosine 3',5'-cyclic monophosphate (cAMP) or by analogs of cAMP. Sodium butyrate increases the intracellular level of cAMP by about two fold in neuroblastoma cells; therefore, some of the effects of sodium butyrate on these cells may in part be mediated by cAMP. Sodium butyrate appears to have properties of a good chemotherapeutic agent for neuroblastoma tumors because the treatment of neuroblastoma cells in culture causes cell death and "differentiation"; however, it is either innocuous or produces reversible morphological and biochemical alterations in other cell types. 相似文献
98.
The incorporation of [35S]methionine into ovalbumin, a protein containing NH2-terminal N-acetylglycine, has been studied in chicken oviduct magnum cells. The purification of [35S]methionine-labeled ovalbumin from total oviduct proteins was accomplished by dialysis of a crude extract at pH 3.6 followed by chromatography on carboxymethyl cellulose. The radioactive ovalbumin eluted from the column in three peaks (P0, P1, and P2-containing 0, 1, and 2 moles of phosphate, respectively, per mole of ovalbumin). The kinetics of labeling of peaks P0 and P1 showed that the ratio of radioactivity in NH2-terminal methionine to total incorporation was greater at 2 min of labeling than at later times. The transient labeling of the NH2-terminus of ovalbumin with methionine indicates that methionine is the initiator amino acid for the synthesis of this protein, which in its mature form contains NH2-terminal N-acetylglycine. 相似文献
99.
Food preference as well as feeding efficiency studies of the carabid predator revealed that the grub of theChlaenius bioculatus
Chaud preferred mostPolytella gloriosae F. larvae in both 2nd and 3rd instar.Tarache tropica
Guénée was preferred least by the grub predator in both instar.T. tropica was found toxic and grubs of the predator died after consumption.
Résumé Les préférences alimentaires, de même que l'efficacité prédatrice deChlaenius bioculatus Chaud, montrent que ce carabide prédateur préfère le plus les larves dePolytella gloriosae F. du 2e et 3e stade.Tarache tropica Guénée est le moins attaqué aux deux stades.T. tropica est toxique et les larves du prédateur meurent après sa consommation.相似文献
100.
Effect of sodium butyrate on mammalian cells in culture: A review 总被引:10,自引:0,他引:10
Kedar N. Prasad Pramod K. Sinha 《In vitro cellular & developmental biology. Plant》1976,12(2):125-132
Summary Sodium butyrate produces reversible changes in morphology, growth rate, and enzyme activities of several mammalian cell types
in culture. Some of these changes are similar to those produced by agents which increase the intracellular level of adenosine
3′,5′-cyclic monophosphate (cAMP) or by analogs of cAMP. Sodium butyrate increases the intracellular level of cAMP by about
two fold in neuroblastoma cells; therefore, some of the effects of sodium butyrate on these cells may in part be mediated
by cAMP. Sodium butyrate appears to have properties of a good chemotherapeutic agent for neuroblastoma tumors because the
treatment of neuroblastoma cells in culture causes cell death and “differentiation”; however, it is either innocuous or produces
reversible morphological and biochemical alterations in other cell types. 相似文献