全文获取类型
收费全文 | 7493篇 |
免费 | 727篇 |
国内免费 | 4篇 |
专业分类
8224篇 |
出版年
2022年 | 59篇 |
2021年 | 135篇 |
2020年 | 70篇 |
2019年 | 81篇 |
2018年 | 91篇 |
2017年 | 72篇 |
2016年 | 177篇 |
2015年 | 307篇 |
2014年 | 301篇 |
2013年 | 426篇 |
2012年 | 545篇 |
2011年 | 488篇 |
2010年 | 300篇 |
2009年 | 242篇 |
2008年 | 424篇 |
2007年 | 435篇 |
2006年 | 363篇 |
2005年 | 316篇 |
2004年 | 322篇 |
2003年 | 314篇 |
2002年 | 326篇 |
2001年 | 123篇 |
2000年 | 89篇 |
1999年 | 88篇 |
1998年 | 107篇 |
1997年 | 77篇 |
1996年 | 65篇 |
1995年 | 46篇 |
1994年 | 69篇 |
1993年 | 51篇 |
1992年 | 55篇 |
1991年 | 60篇 |
1990年 | 72篇 |
1989年 | 58篇 |
1988年 | 58篇 |
1987年 | 49篇 |
1986年 | 59篇 |
1985年 | 66篇 |
1984年 | 74篇 |
1983年 | 72篇 |
1982年 | 71篇 |
1981年 | 68篇 |
1980年 | 48篇 |
1978年 | 54篇 |
1977年 | 51篇 |
1976年 | 55篇 |
1975年 | 58篇 |
1974年 | 58篇 |
1973年 | 48篇 |
1972年 | 52篇 |
排序方式: 共有8224条查询结果,搜索用时 7 毫秒
31.
Ruth C. Steinkamp Clarence L. Young Dolores Nyhus Arnold E. Greenberg 《The Western journal of medicine》1968,109(2):126-133
The amount of sodium ion in water used for ingestion may be critical in effective use of a low sodium dietary regimen. Waters containing not over 20 mg of sodium per liter are provided for in the sodium restricted diets set forth by the American Heart Association. For diets containing more than 500 mg of sodium a day, waters of greater sodium content may be used if proper dietary adjustments are made.While assessment of the long-term average sodium content of a community water supply is difficult, the determined values for sodium lend to classification within range categories. The larger community water supplies in California are presented within several range categories of sodium content.The more commonly used water softeners add sodium to water. The sodium-restricted patient should be cautioned against their use. Similar consideration should probably be given to water supplies of retirement communities where the potential for disorders requiring sodium restriction is greater than in the general population. 相似文献
32.
33.
Phase distribution of sterols: studies by gel filtration 总被引:1,自引:0,他引:1
34.
A study of 10 infants in severe metabolic acidemia (pH below 7) led to the conclusion that the clinical signs—hyperventilation, coma or lethargy, peripheral vascular collapse, a significantly palpable liver, and abdominal distension—may all be directly related to the metabolic acidemia. In five of 10 infants, an initial erroneous diagnosis of congestive heart failure or pneumonia was made. Dramatic clinical improvement followed correction of the acidemia with rapid intravenous administration of sodium bicarbonate. This rapid administration of sodium bicarbonate was safe, provided hypocalcemia was recognized and treated in its early stages. In severe metabolic acidemia the measurement of blood bicarbonate alone does not reflect adequately the magnitude of the acid-base derangement and repeated measurements of hydrogen ion concentration, Pco2 and bicarbonates are needed to evaluate and treat such infants correctly. 相似文献
35.
36.
37.
Influence of oestradiol on protein expression and methionine utilization during morphogenesis of Paracoccidioides brasiliensis 总被引:3,自引:0,他引:3
The temporal sequence of cytosolic protein expression during phase transition of Paracoccidioides brasiliensis was examined. Electrophoretic analysis of cytosol proteins by one-dimensional SDS-PAGE revealed numerous differences between the mycelial and yeast forms as well as alterations induced by 17 beta-oestradiol. Using either protein staining or fluorography of [35S]methionine-labelled proteins 30 phase-specific bands were detected, 12 mycelial-associated bands (range 30 to 140 kDa) and 18 yeast-associated bands (range 22 to 127 kDa). In cells undergoing mycelial to yeast transition after a shift from 25 degrees C to 37 degrees C, the protein patterns showed a temporal progression toward the yeast profile with the accumulation of yeast bands prior to observable morphogenesis. Five novel protein bands (range 23 to 50 kDa) were detected by silver staining during transition. Treatment of temperature-shifted mycelial cultures with 2.6 x 10(-7) M-oestradiol altered observed profiles; 4 of 12 mycelial-associated bands were maintained whereas the appearance of the 5 novel transition bands and 9 of 18 yeast-associated bands was blocked or delayed. Analysis of [35S]methionine-labelled proteins revealed that oestradiol induced label uptake by mycelial cells, blocked the synthesis of a 92 kDa yeast-specific band 72 h into transition, and diminished label incorporation 120 h into transition. In conjunction with these steroid-induced alterations of protein expression, little or no morphological transformation occurred. These results support our hypothesis that, analogous to mammalian steroid receptor action, the functional responses of P. brasiliensis to oestradiol are related to regulation of protein expression, presumably mediated via a specific binding protein-ligand complex. 相似文献
38.
39.
Jan O. Gordeladze Trine Haugen Eivind J. Paulssen Ruth H. Paulssen 《Bioscience reports》1996,16(1):65-74
The presence of the pertussis toxin (PTX) insensitive GTP-binding proteins (G-proteins) Gq and/or G11 has been demonstrated in three different prolactin (PRL) and growth hormone (GH) producing pituitary adenoma cell lines. Immunoblocking of their coupling to hormone receptors indicates that Gq and/or G11 confer throliberin (TRH) responsive phospholipase C (PL-C) activity in these cells. The contention was substantiated by immunoprecipitation analyses snowing that anti Gq/11-sera coprecipitated PL-C activity. In essence, only Gq/11 (but neither Gi2, Gi3 nor Go) seems to mediate the TRH-sensitive PL-C activity, while Go may be coupled to a basal or constitutive PL-C activity. Immunoblocking studies imply that the B-complex also, to some extent, may stimulate GH3 pituitary cell line PL-C activity. Finally, the steady state levels of Gq/11 mRNA and protein were downregulated upon long term exposure of the GH3 cells to TRH (but not to vasoactive intestinal peptide = VIP). 相似文献
40.
Gene-culture coevolutionary theory is a branch of theoretical population genetics that models the transmission of genes and cultural traits from one generation to the next, exploring how they interact. These models have been employed to examine the adaptive advantages of learning and culture, to investigate the forces of cultural change, to partition the variance in complex human behavioral and personality traits, and to address specific cases in human evolution in which there is an interaction between genes and culture. 相似文献