全文获取类型
收费全文 | 15302篇 |
免费 | 1117篇 |
国内免费 | 551篇 |
专业分类
16970篇 |
出版年
2024年 | 27篇 |
2023年 | 127篇 |
2022年 | 326篇 |
2021年 | 504篇 |
2020年 | 372篇 |
2019年 | 469篇 |
2018年 | 559篇 |
2017年 | 432篇 |
2016年 | 630篇 |
2015年 | 904篇 |
2014年 | 1015篇 |
2013年 | 1169篇 |
2012年 | 1418篇 |
2011年 | 1319篇 |
2010年 | 789篇 |
2009年 | 701篇 |
2008年 | 842篇 |
2007年 | 770篇 |
2006年 | 622篇 |
2005年 | 550篇 |
2004年 | 508篇 |
2003年 | 423篇 |
2002年 | 367篇 |
2001年 | 278篇 |
2000年 | 254篇 |
1999年 | 213篇 |
1998年 | 126篇 |
1997年 | 129篇 |
1996年 | 108篇 |
1995年 | 97篇 |
1994年 | 87篇 |
1993年 | 86篇 |
1992年 | 104篇 |
1991年 | 99篇 |
1990年 | 80篇 |
1989年 | 74篇 |
1988年 | 61篇 |
1987年 | 57篇 |
1986年 | 43篇 |
1985年 | 43篇 |
1984年 | 29篇 |
1983年 | 23篇 |
1982年 | 12篇 |
1981年 | 14篇 |
1979年 | 16篇 |
1978年 | 17篇 |
1975年 | 9篇 |
1974年 | 8篇 |
1972年 | 14篇 |
1971年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Jiaqiang Xiong Zhiyong Lu Meng Wu Jinjin Zhang Jing Cheng Aiyue Luo Wei Shen Li Fang Su Zhou Shixuan Wang 《PloS one》2015,10(10)
Early menopause and infertility often occur in female cancer patients after chemotherapy (CTx). For these patients, oocyte/embryo cryopreservation or ovarian tissue cryopreservation is the current modality for fertility preservation. However, the above methods are limited in the long-term protection of ovarian function, especially for fertility preservation (very few females with cancer have achieved pregnancy with cryopreserved ovarian tissue or eggs until now). In addition, the above methods are subject to their scope (females with no husband or prepubertal females with no mature oocytes). Thus, many females who suffer from cancers would not adopt the above methods pre- and post-CTx due to their uncertainty, safety and cost-effectiveness. Therefore, millions of women have achieved long-term survival after thorough CTx treatment and have desired to rescue their ovarian function and fertility with economic, durable and reliable methods. Recently, some studies showed that mice with infertility caused by CTx can produce normal offspring through intraovarian injection of exogenous female germline stem cells (FGSCs). Though exogenous FGSC can be derived from mice without immune rejection in the same strain, it is difficult to obtain human female germline stem cells (hFGSCs), and immune rejection could occur between different individuals. In this study, infertility in mice was caused by CTx, and the ability of FGSCs to restore ovarian function or even produce offspring was assessed. We had successfully isolated and purified the FGSCs from adult female mice two weeks after CTx. After infection with GFP-carrying virus, the FGSCs were transplanted into ovaries of mice with infertility caused by CTx. Finally, ovarian function was restored and the recipients produced offspring long-term. These findings showed that mice with CTx possessed FGSCs, restoring ovarian function and avoiding immune rejection from exogenous germline stem cells. 相似文献
992.
Myoung Nam Bae Su Hyun Kim Young Ok Kim Dong Chan Jin Ho Chul Song Euy Jin Choi Yong-Lim Kim Yon-Su Kim Shin-Wook Kang Nam-Ho Kim Chul Woo Yang Yong Kyun Kim 《PloS one》2015,10(11)
Erythropoiesis-stimulating agent (ESA) responsiveness has been reported to be associated with increased mortality in hemodialysis (HD) patients. ESA requirement to obtain the same hemoglobin (Hb) level is different between HD and peritoneal dialysis (PD) patients. In this study, we investigated the impact of ESA responsiveness on mortality between both HD and PD patients. Prevalent HD and PD patients were selected from the Clinical Research Center registry for end-stage renal disease, a prospective cohort study in Korea. ESA responsiveness was estimated using an erythropoietin resistant index (ERI) (U/kg/week/g/dL). Patients were divided into three groups by tertiles of ERI. ESA responsiveness was also assessed based on a combination of ESA dosage and hemoglobin (Hb) levels. The primary outcome was all-cause mortality. A total of 1,594 HD and 876 PD patients were included. The median ESA dose and ERI were lower in PD patients compared with HD patients (ESA dose: 4000 U/week vs 6000 U/week, respectively. P<0.001, ERI: 7.0 vs 10.4 U/kg/week/g/dl, respectively. P<0.001). The median follow-up period was 40 months. In HD patients, the highest ERI tertile was significantly associated with higher risk for all-cause mortality (HR 1.96, 95% CI, 1.07 to 3.59, P = 0.029). HD patients with high-dose ESA and low Hb levels (ESA hypo-responsiveness) had a significantly higher risk of all-cause mortality (HR 2.24, 95% CI, 1.16 to 4.31, P = 0.016). In PD patients, there was no significant difference in all-cause mortality among the ERI groups (P = 0.247, log-rank test). ESA hypo-responsiveness was not associated with all-cause mortality (HR = 1.75, 95% CI, 0.58 to 5.28, P = 0.319). Our data showed that ESA hypo-responsiveness was associated with an increased risk of all-cause mortality in HD patients. However, in PD patients, ESA hypo-responsiveness was not related to all-cause mortality. These finding suggest the different prognostic value of ESA responsiveness between HD and PD patients. 相似文献
993.
Suppression of root-knot nematodes is crucially important for maintaining the worldwide development of the banana industry. Growing concerns about human and environmental safety have led to the withdrawal of commonly used nematicides and soil fumigants, thus motivating the development of alternative nematode management strategies. In this study, Meloidogyne javanica was isolated, and the nematicidal effect of Camellia seed cake on this pest was investigated. The results showed that in dish experiments, Camellia seed cake extracts under low concentration (2 g/L) showed a strong nematicidal effect. After treatment for 72 h, the eggs of M. javanica were gradually dissolved, and the intestine of the juveniles gradually became indistinct. Nematicidal compounds, including saponins identified by HPLC-ESI-MS and 8 types of volatile compounds identified by GC-MS, exhibited effective nematicidal activities, especially 4-methylphenol. The pot experiments demonstrated that the application of Camellia seed cake suppressed M. javanica, and promoted the banana plant growth. This study explored an effective nematicidal agent for application in soil and revealed its potential mechanism of nematode suppression. 相似文献
994.
Susan E. Steck Lenore Arab Hongmei Zhang Jeannette T. Bensen Elizabeth T. H. Fontham Candace S. Johnson James L. Mohler Gary J. Smith Joseph L. Su Donald L. Trump Anna Woloszynska-Read 《PloS one》2015,10(4)
Background
African Americans (AAs) have lower circulating 25-hydroxyvitamin D3 [25(OH)D3] concentrations and higher prostate cancer (CaP) aggressiveness than other racial/ethnic groups. The purpose of the current study was to examine the relationship between plasma 25(OH)D3, African ancestry and CaP aggressiveness among AAs and European Americans (EAs).Methods
Plasma 25(OH)D3 was measured using LC-MS/MS (Liquid Chromatography Tandem Mass Spectrometry) in 537 AA and 663 EA newly-diagnosed CaP patients from the North Carolina-Louisiana Prostate Cancer Project (PCaP) classified as having either ‘high’ or ‘low’ aggressive disease based on clinical stage, Gleason grade and prostate specific antigen at diagnosis. Mean plasma 25(OH)D3 concentrations were compared by proportion of African ancestry. Logistic regression was used to calculate multivariable adjusted odds ratios (OR) and 95% confidence intervals (95%CI) for high aggressive CaP by tertile of plasma 25(OH)D3.Results
AAs with highest percent African ancestry (>95%) had the lowest mean plasma 25(OH)D3 concentrations. Overall, plasma 25(OH)D3 was associated positively with aggressiveness among AA men, an association that was modified by calcium intake (ORT3vs.T1: 2.23, 95%CI: 1.26–3.95 among men with low calcium intake, and ORT3vs.T1: 0.19, 95%CI: 0.05–0.70 among men with high calcium intake). Among EAs, the point estimates of the ORs were <1.0 for the upper tertiles with CIs that included the null.Conclusions
Among AAs, plasma 25(OH)D3 was associated positively with CaP aggressiveness among men with low calcium intake and inversely among men with high calcium intake. The clinical significance of circulating concentrations of 25(OH)D3 and interactions with calcium intake in the AA population warrants further study. 相似文献995.
Jeong-Whun Kim Hong Joong Kim Woo Hyun Lee Dong-Kyu Kim Sung Wan Kim Young Hyo Kim Jung Gwon Nam Seok-Won Park Chan-Soon Park Woo Yong Bae Nam-Kyung Yeo Tae-Bin Won Seung Hoon Lee Tae-Hoon Lee Hyoung Joo Lee Sang-Wook Kim Sung-Wook Jeong Jeong-Seok Choi Doo Hee Han Ji Ho Choi 《PloS one》2015,10(8)
Background/Objective
There have been several operative techniques for adenoidectomy and their efficacy and morbidity are different according to the technique. This prospective multicenter study was aimed to compare the efficacy and morbidity of coblation adenoidectomy (CA) with those of power-assisted adenoidectomy.Study Design
Prospective multi-institutional study.Methods
Children who underwent CA, power-assisted adenoidectomy with cauterization (PAA+C) or without cauterization (PAA-C) due to adenoid hypertrophy were enrolled from 13 hospitals between July 2013 and June 2014. Mean operation time, degree of intraoperative bleeding and postoperative bleeding rate were evaluated.Results
A total of 388 children (mean age ± standard deviation = 6.6 ± 2.5 years; 245 males and 143 females) were included. According to the adenoidectomy technique, the children were classified into 3 groups: (1) CA (n = 116); (2) PAA+C (n = 153); and (3) PAA-C (n = 119). Significant differences were not found in age and sex among three groups. In the CA group, mean operation time was significantly shorter (P < 0.001) and degree of intraoperative bleeding was significantly less (P < 0.001) compared to PAA+C or PAA-C group. Delayed postoperative bleeding rate of PAA-C group was significantly higher than that of CA or PAA+C group (P = 0.016).Conclusions
This prospective multicenter study showed that CA was superior to PAA in terms of mean operation time and degree of intraoperative bleeding. 相似文献996.
997.
Hae Mi Joo Su Jin Kang Seon Young Nam Kwang Hee Yang Cha Soon Kim In Kyung Lee Ji Young Kim 《PloS one》2015,10(8)
Ionizing radiation has different biological effects according to dose and dose rate. In particular, the biological effect of low-dose radiation is unclear. Low-dose whole-body gamma irradiation activates immune responses in several ways. However, the effects and mechanism of low-dose radiation on allergic responses remain poorly understood. Previously, we reported that low-dose ionizing radiation inhibits mediator release in IgE-mediated RBL-2H3 mast cell activation. In this study, to have any physiological relevance, we investigated whether low-dose radiation inhibits allergic responses in activated human mast cells (HMC-1(5C6) and LAD2 cells), mouse models of passive cutaneous anaphylaxis and the late-phase cutaneous response. High-dose radiation induced cell death, but low-dose ionizing radiation of <0.5 Gy did not induce mast cell death. Low-dose ionizing radiation that did not induce cell death significantly suppressed mediator release from human mast cells (HMC-1(5C6) and LAD2 cells) that were activated by antigen-antibody reaction. To determine the inhibitory mechanism of mediator released by low-dose ionizing radiation, we examined the phosphorylation of intracellular signaling molecules such as Lyn, Syk, phospholipase Cγ, and protein kinase C, as well as the intracellular free Ca2+ concentration ([Ca2+]i). The phosphorylation of signaling molecules and [Ca2+]i following stimulation of FcεRI receptors was inhibited by low dose ionizing radiation. In agreement with its in vitro effect, ionizing radiation also significantly inhibited inflammatory cells infiltration, cytokine mRNA expression (TNF-α, IL-4, IL-13), and symptoms of passive cutaneous anaphylaxis reaction and the late-phase cutaneous response in anti-dinitrophenyl IgE-sensitized mice. These results indicate that ionizing radiation inhibits both mast cell-mediated immediate- and delayed-type allergic reactions in vivo and in vitro. 相似文献
998.
Hydrogen gas (H2) was recently proposed as a therapeutic antioxidant and signaling molecule in clinical trials. However, the underlying physiological roles of H2 in plants remain unclear. In the present study, hydrogen-rich water (HRW) was used to characterize the physiological roles of H2 in enhancing the tolerance of Brassica campestris against cadmium (Cd). The results showed that both 50 μM CdCl2 and 50%-saturated HRW induced an increase of endogenous H2 in Brassica campestris seedlings, and HRW alleviated Cd toxicity related to growth inhibition and oxidative damage. Seedlings supplied with HRW exhibited increased root length and reduced lipid peroxidation, similar to plants receiving GSH post-treatment. Additionally, seedlings post-treated with HRW accumulated higher levels of reduced glutathione (GSH) and ascorbic acid (AsA) and showed increased GST and GPX activities in roots. Molecular evidence illustrated that the expression of genes such as GS, GR1 and GR2, which were down-regulated following the addition of Cd, GSH or BSO, could be reversed to varying degrees by the addition of HRW. Based on these results, it could be proposed that H2 might be an important regulator for enhancing the tolerance of Brassica campestris seedlings against Cd, mainly by governing reduced glutathione homeostasis. 相似文献
999.
Su-Hyeon Kim Gyoengjun Cho Su In Lee Da-Ran Kim Youn-Sig Kwak 《The Plant Pathology Journal》2021,37(4):396
Fire blight disease, caused by Erwinia amylovora, could damage rosaceous plants such as apples, pears, and raspberries. In this study, we designed to understand how E. amylovora affected other bacterial communities on apple rhizosphere; twig and fruit endosphere; and leaf, and fruit episphere. Limited studies on the understanding of the microbial community of apples and changes the community structure by occurrence of the fire blight disease were conducted. As result of these experiments, the infected trees had low species richness and operational taxonomic unit diversity when compared to healthy trees. Rhizospheric bacterial communities were stable regardless of infection. But the communities in endosphere and episphere were significanlty affected by E. amylovora infection. We also found that several metabolic pathways differ significantly between infected and healthy trees. In particular, we observed differences in sugar metabolites. The finding provides that sucrose metabolites are important for colonization of E. amylovora in host tissue. Our results provide fundamental information on the microbial community structures between E. amylovora infected and uninfected trees, which will contribute to developing novel control strategies for the fire blight disease. 相似文献
1000.
Jiu-Xiang Xie Gong-Hua Lin Cui-Xia Liu Chuan-Hua Yang Xiao-Gong Deng Xue-Feng Cui Bang Li Tong-Zuo Zhang Jian-Ping Su 《Acta theriologica》2014,59(2):337-345
Subterranean herbivores affect the plant community by plant consumption and burrowing activities. However, diet selection of subterranean herbivores has not been studied in detail in complex natural fields, mainly for lack of an accurate method to determine diet species, frequency, and biomass. Plateau zokors' (Eospalax baileyi) caching habit for the long inclement winter makes it possible to solve this problem. We studied the diet composition and biomass in caches and vicinity of plateau zokors' burrow systems. We found that plateau zokors are dietary generalist but show a significant selection among the available food items, plant parts, functional groups, organ types, and habitats. These results suggested that plateau zokors strictly selected their diet and were able to adjust their foraging strategy according to the different conditions of food abundance and quality. Plateau zokors' selective foraging can directly reduce the proportion of toxicity forbs; plateau zokors can be recognized as an important element to influence the alpine meadow plant community and cattle husbandry. 相似文献