全文获取类型
收费全文 | 4853篇 |
免费 | 491篇 |
国内免费 | 2篇 |
出版年
2023年 | 27篇 |
2022年 | 23篇 |
2021年 | 112篇 |
2020年 | 92篇 |
2019年 | 122篇 |
2018年 | 111篇 |
2017年 | 117篇 |
2016年 | 188篇 |
2015年 | 271篇 |
2014年 | 291篇 |
2013年 | 330篇 |
2012年 | 473篇 |
2011年 | 448篇 |
2010年 | 261篇 |
2009年 | 231篇 |
2008年 | 303篇 |
2007年 | 299篇 |
2006年 | 243篇 |
2005年 | 228篇 |
2004年 | 225篇 |
2003年 | 188篇 |
2002年 | 156篇 |
2001年 | 39篇 |
2000年 | 20篇 |
1999年 | 31篇 |
1998年 | 35篇 |
1997年 | 25篇 |
1996年 | 23篇 |
1995年 | 18篇 |
1994年 | 24篇 |
1993年 | 18篇 |
1992年 | 25篇 |
1991年 | 28篇 |
1990年 | 22篇 |
1989年 | 24篇 |
1988年 | 20篇 |
1987年 | 20篇 |
1986年 | 16篇 |
1985年 | 19篇 |
1984年 | 11篇 |
1983年 | 11篇 |
1981年 | 18篇 |
1980年 | 9篇 |
1979年 | 9篇 |
1978年 | 10篇 |
1976年 | 15篇 |
1975年 | 13篇 |
1974年 | 17篇 |
1973年 | 9篇 |
1972年 | 10篇 |
排序方式: 共有5346条查询结果,搜索用时 62 毫秒
1.
2.
3.
4.
5.
6.
7.
This analysis investigates the ontogeny of body size dimorphism in apes. The processes that lead to adult body size dimorphism are illustrated and described. Potential covariation between ontogenetic processes and socioecological variables is evaluated. Mixed-longitudinal growth data from 395 captive individuals (representing Hylobates lar [gibbon], Hylobates syndactylus [siamang], Pongo pygmaeus [orangutan], Gorilla gorilla [gorilla], Pan paniscus [pygmy chimpanzee], and Pan troglodytes [“common” chimpanzee]) form the basis of this study. Results illustrate heterogeneity in the growth processes that produce ape dimorphism. Hylobatids show no sexual differentiation in body weight growth. Adult body size dimorphism in Pongo can be largely attributed to indeterminate male growth. Dimorphism in African apes is produced by two different ontogenetic processes. Both pygmy chimpanzees (Pan paniscus) and gorillas (Gorilla gorilla) become dimorphic primarily through bimaturism (sex differences in duration of growth). In contrast, sex differences in rate of growth account for the majority of dimorphism in common chimpanzees (Pan troglodytes). Diversity in the ontogenetic pathways that produce adult body size dimorphism may be related to multiple evolutionary causes of dimorphism. The lack of sex differences in hylobatid growth is consistent with a monogamous social organization. Adult dimorphism in Pongo can be attributed to sexual selection for indeterminate male growth. Interpretation of dimorphism in African apes is complicated because factors that influence female ontogeny have a substantial effect on the resultant adult dimorphism. Sexual selection for prolonged male growth in gorillas may also increase bimaturism relative to common chimpanzees. Variation in female growth is hypothesized to covary with foraging adaptations and with differences in female competition that result from these foraging adaptations. Variation in male growth probably corresponds to variation in level of sexual selection. © 1995 Wiley-Liss, Inc. 相似文献
8.
N V Gorbunov R A Nasyrov A N Erin V P Ivanova L Iu Taros 《Biulleten' eksperimental'no? biologii i meditsiny》1992,113(6):604-606
The effect of various concentrations of both methyl ether of 5-doxyl-stearic acid (M5DS) and 4-maleimido-TEMPO (4MT) on the pathogenicity of herpes simplex virus (HSV-1) was studied. It is known that the reagents modify the lipid matrix and the proteins of virion envelope. The decrease of the HSV-1 pathogenicity was shown when using the concentration of reagents more 5 x 10(-5) M. HSV-1 having high pathogenicity and cytotoxicity was obtained when the concentrations of the reagents were less 5 x 10(-5) M. 相似文献
9.
Julie A. Eclov Qingwen Qian Rebecca Redetzke Quanhai Chen Steven C. Wu Chastity L. Healy Steven B. Ortmeier Erin Harmon Gregory C. Shearer Timothy D. O’Connell 《Journal of lipid research》2015,56(12):2297-2308
Heart failure with preserved ejection fraction (HFpEF) is half of all HF, but standard HF therapies are ineffective. Diastolic dysfunction, often secondary to interstitial fibrosis, is common in HFpEF. Previously, we found that supra-physiologic levels of ω3-PUFAs produced by 12 weeks of ω3-dietary supplementation prevented fibrosis and contractile dysfunction following pressure overload [transverse aortic constriction (TAC)], a model that resembles aspects of remodeling in HFpEF. This raised several questions regarding ω3-concentration-dependent cardioprotection, the specific role of EPA and DHA, and the relationship between prevention of fibrosis and contractile dysfunction. To achieve more clinically relevant ω3-levels and test individual ω3-PUFAs, we shortened the ω3-diet regimen and used EPA- and DHA-specific diets to examine remodeling following TAC. The shorter diet regimen produced ω3-PUFA levels closer to Western clinics. Further, EPA, but not DHA, prevented fibrosis following TAC. However, neither ω3-PUFA prevented contractile dysfunction, perhaps due to reduced uptake of ω3-PUFA. Interestingly, EPA did not accumulate in cardiac fibroblasts. However, FFA receptor 4, a G protein-coupled receptor for ω3-PUFAs, was sufficient and required to block transforming growth factor β1-fibrotic signaling in cultured cardiac fibroblasts, suggesting a novel mechanism for EPA. In summary, EPA-mediated prevention of fibrosis could represent a novel therapy for HFpEF. 相似文献
10.
Harold D. Love S. Erin Booton Braden E. Boone Joan P. Breyer Tatsuki Koyama Monica P. Revelo Scott B. Shappell Jeffrey R. Smith Simon W. Hayward 《PloS one》2009,4(12)
Benign prostatic hyperplasia (BPH) and prostate carcinoma (CaP) are linked to aging and the presence of androgens, suggesting that androgen regulated genes play a major role in these common diseases. Androgen regulation of prostate growth and development depends on the presence of intact epithelial-stromal interactions. Further, the prostatic stroma is implicated in BPH. This suggests that epithelial cell lines are inadequate to identify androgen regulated genes that could contribute to BPH and CaP and which could serve as potential clinical biomarkers. In this study, we used a human prostate xenograft model to define a profile of genes regulated in vivo by androgens, with an emphasis on identifying candidate biomarkers. Benign transition zone (TZ) human prostate tissue from radical prostatectomies was grafted to the sub-renal capsule site of intact or castrated male immunodeficient mice, followed by the removal or addition of androgens, respectively. Microarray analysis of RNA from these tissues was used to identify genes that were; 1) highly expressed in prostate, 2) had significant expression changes in response to androgens, and, 3) encode extracellular proteins. A total of 95 genes meeting these criteria were selected for analysis and validation of expression in patient prostate tissues using quantitative real-time PCR. Expression levels of these genes were measured in pooled RNAs from human prostate tissues with varying severity of BPH pathologic changes and CaP of varying Gleason score. A number of androgen regulated genes were identified. Additionally, a subset of these genes were over-expressed in RNA from clinical BPH tissues, and the levels of many were found to correlate with disease status. Our results demonstrate the feasibility, and some of the problems, of using a mouse xenograft model to characterize the androgen regulated expression profiles of intact human prostate tissues. 相似文献