全文获取类型
收费全文 | 848篇 |
免费 | 109篇 |
专业分类
957篇 |
出版年
2018年 | 8篇 |
2016年 | 13篇 |
2015年 | 19篇 |
2014年 | 21篇 |
2013年 | 42篇 |
2012年 | 37篇 |
2011年 | 28篇 |
2010年 | 23篇 |
2009年 | 11篇 |
2008年 | 33篇 |
2007年 | 32篇 |
2006年 | 29篇 |
2005年 | 40篇 |
2004年 | 34篇 |
2003年 | 38篇 |
2002年 | 33篇 |
2000年 | 9篇 |
1998年 | 16篇 |
1997年 | 7篇 |
1996年 | 8篇 |
1992年 | 13篇 |
1991年 | 9篇 |
1990年 | 13篇 |
1988年 | 9篇 |
1987年 | 12篇 |
1986年 | 10篇 |
1985年 | 21篇 |
1984年 | 9篇 |
1983年 | 16篇 |
1982年 | 8篇 |
1981年 | 11篇 |
1980年 | 14篇 |
1979年 | 15篇 |
1978年 | 15篇 |
1977年 | 10篇 |
1976年 | 11篇 |
1975年 | 7篇 |
1974年 | 7篇 |
1973年 | 16篇 |
1972年 | 9篇 |
1971年 | 7篇 |
1970年 | 7篇 |
1969年 | 8篇 |
1968年 | 7篇 |
1967年 | 8篇 |
1965年 | 7篇 |
1964年 | 9篇 |
1962年 | 9篇 |
1961年 | 7篇 |
1957年 | 7篇 |
排序方式: 共有957条查询结果,搜索用时 0 毫秒
141.
142.
Earl S. Ford David G. Moriarty Matthew M. Zack Ali H. Mokdad Daniel P. Chapman 《Obesity (Silver Spring, Md.)》2001,9(1):21-31
Objective: To examine the relationship between self‐reported body mass index (BMI) and health‐related quality of life in the general adult population in the United States. Research Methods and Procedures: Using data from 109,076 respondents in the 1996 Behavioral Risk Factor Surveillance System, we examined how self‐reported BMI is associated with five health‐related quality of life measures developed by the Centers for Disease Control and Prevention for population health surveillance. Results: After adjusting for age, gender, race or ethnicity, educational attainment, employment status, smoking status, and physical activity status, participants with a self‐reported BMI of <18.5 kg/m2 and participants with a self‐reported BMI of ≥30 kg/m2 reported impaired quality of life. Compared with persons with a self‐reported BMI of 18.5 to <25 kg/m2, odds ratios (ORs) of poor or fair self‐rated health increased among persons with self‐reported BMIs of <18.5 (1.57, 95% confidence interval [CI]: 1.31 to 1.89), 25 to <30 kg/m2 (1.12, 95% CI: 1.04 to 1.20), 30 to <35 kg/m2 (1.65, 95% CI: 1.50 to 1.81), 35 to <40 kg/m2 (2.58, 95% CI: 2.21 to 3.00), and ≥40 kg/m2 (3.23, 95% CI: 2.63 to 3.95); ORs for reporting ≥14 days of poor physical health during the previous 30 days were 1.44 (95% CI: 1.21 to 1.72), 1.04 (95% CI: 0.96 to 1.14), 1.32 (95% CI: 1.19 to 1.47), 1.80 (95% CI: 1.52 to 2.13), and 2.37 (95% CI: 1.90 to 2.94), respectively; ORs for having ≥14 days of poor mental health during the previous 30 days were 1.18 (95% CI: 0.97 to 1.42), 1.02 (95% CI: 0.95 to 1.11), 1.22 (95% CI: 1.10 to 1.36), 1.68 (95% CI: 1.42 to 1.98), and 1.66 (95% CI: 1.32 to 2.09), respectively. Discussion: In the largest study to date, low and increased self‐reported BMI significantly impaired health‐related quality of life. Particularly, deviations from normal BMI affected physical functioning more strongly than mental functioning. 相似文献
143.
Genetic Evidence that the uvsE Gene Product of Deinococcus radiodurans R1 Is a UV Damage Endonuclease 总被引:7,自引:0,他引:7 下载免费PDF全文
Ashlee M. Earl Sara K. Rankin Kwang-Pyo Kim Oleana N. Lamendola John R. Battista 《Journal of bacteriology》2002,184(4):1003-1009
An in vitro transposition system, developed to facilitate gene disruption in Deinococcus radiodurans R1, has been used to inactivate the gene designated dr1819 in uvrA-1(+) and uvrA-1 backgrounds. dr1819 encodes a protein with homology to a UV DNA damage endonuclease expressed by Schizosaccharomyces pombe. Interruption of dr1819 greatly sensitizes the uvrA-1 strain but not the uvrA-1(+) strain to UV light, indicating that the dr1819 gene product is a component in a DNA repair pathway that can compensate for the loss of nucleotide excision repair in this species. Clones of dr1819 will restore UV resistance to UVS78, a uvrA-1 uvsE strain, indicating that dr1819 and uvsE are the same locus. 相似文献
144.
Susann Richert Nancy B Wehr Earl R Stadtman Rodney L Levine 《Archives of biochemistry and biophysics》2002,397(2):430-432
The oxidative modification of proteins by reactive species, especially reactive oxygen species, is implicated in the etiology or progression of a panoply of disorders and diseases. For the most part, oxidatively modified proteins are not repaired and must be removed by proteolytic degradation. The level of these modified molecules can be quantitated by measurement of the protein carbonyl content, which has been shown to increase in a variety of diseases and processes, most notably during aging. However, these studies have required invasive techniques to obtain cells for analysis. We examined the possibility that desquamating skin cells (corneocytes) would also show an age-related increase in protein carbonyl content, thus providing a noninvasive method for assessing biological age. This was not the case, as we found no age-dependent relationship in the protein carbonyl content of skin cells from volunteers aged 20 to 79 years. 相似文献
145.
Abstract. The parasitic ciliate Orchitophrya stellarum was found in the testes of brooding, winter-spawning Leptasterias spp. from San Juan Island, Washington, but not in the testes of Leptasterias spp. from the Lynn Canal, Alaska. Dense populations of the ciliate were localized within the fuller areas of testes, where sperm counts were significantly reduced. The ciliates were loaded with phagosomes, some of which contained sperms in various stages of digestion. Leptasterias spp. are not as severely impacted by this ciliated protozoan parasite as Pisaster ochraceus. Leptasterias spp. may serve as seasonal hosts for O. stellarum ; this ciliate lives in seawater and in ripe males of winter-brooding and spring-summer broadcasting sea stars. The wet weight of parasitized and non-parasitized males did not differ. The sex ratio did not deviate from the expected (1:1) in any population except at Point Louisa, Alaska, where males outnumbered females. Testis indexes of parasitized males from 2 of the 4 locations on San Juan Island, Washington were significantly reduced relative to non-parasitized males, indicating a loss of sperm output during spawning. 相似文献
146.
147.
148.
149.
150.
Glugea hertwigi spores were activated to discharge sporoplasms in Medium 199 with 3% gelatin at pH 9.0; the liberated sporoplasms were transferred to a maintenance medium with 6% gelatin (pH 7.0) supplemented with 2 mM ATP and 10% (v/v) fetal calf scrum. The spherical sporoplasms (measuring 3.5-4 m?m in diameter) had single nuclei and had a cytoplasm rich in free ribosomes. Each G. hertwigi sporoplasm was initially bounded by an external (0.1-0.2 m?m) satellite body adjoining the plasma membrane. The satellites displayed ordered membrane and appeared to merge with the sporoplasm 15-30 min after spore discharge. The external location of the satellite (in reference to the discharged sporoplasm) seems to be part of the normal sequence of events under the in vitro conditions provided. The surface of G. hertwigi sporoplasms does not bear an obvious surface coat; however, our cytochemical observations indicate the plasma membrane of the sporoplasm was somewhat responsive to concanavalin A-peroxidase, colloidal iron, and native ferritin. During the short term incubations of sporoplasms with ferritin, the particles permeated membrane channels extending into the sporoplasm cytoplasm. 相似文献