全文获取类型
收费全文 | 47395篇 |
免费 | 3354篇 |
国内免费 | 19篇 |
专业分类
50768篇 |
出版年
2024年 | 52篇 |
2023年 | 175篇 |
2022年 | 565篇 |
2021年 | 912篇 |
2020年 | 568篇 |
2019年 | 682篇 |
2018年 | 1027篇 |
2017年 | 906篇 |
2016年 | 1477篇 |
2015年 | 2320篇 |
2014年 | 2666篇 |
2013年 | 2978篇 |
2012年 | 3940篇 |
2011年 | 3778篇 |
2010年 | 2392篇 |
2009年 | 2184篇 |
2008年 | 3028篇 |
2007年 | 2909篇 |
2006年 | 2540篇 |
2005年 | 2356篇 |
2004年 | 2161篇 |
2003年 | 1864篇 |
2002年 | 1614篇 |
2001年 | 1301篇 |
2000年 | 1228篇 |
1999年 | 990篇 |
1998年 | 393篇 |
1997年 | 338篇 |
1996年 | 245篇 |
1995年 | 209篇 |
1994年 | 207篇 |
1993年 | 172篇 |
1992年 | 326篇 |
1991年 | 295篇 |
1990年 | 266篇 |
1989年 | 226篇 |
1988年 | 173篇 |
1987年 | 163篇 |
1986年 | 131篇 |
1985年 | 105篇 |
1984年 | 78篇 |
1983年 | 84篇 |
1982年 | 63篇 |
1981年 | 53篇 |
1980年 | 54篇 |
1979年 | 69篇 |
1978年 | 51篇 |
1977年 | 50篇 |
1976年 | 43篇 |
1974年 | 63篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
941.
Ayoub Kdimy Dr. Seong Jong Kim Dr. Zulfiqar Ali Dr. Md Imdadul H. Khan Dr. Siddharth K. Tripathi Prof. Souad El Hajjaji Prof. Hoang V. Le 《化学与生物多样性》2023,20(9):e202300903
Many plants have been known to be contaminated and accumulate plasticizers from the environment, including water sources, soil, and atmosphere. Plasticizers are used to confer elasticity and flexibility to various fiber and plastic products. Consumption of plasticizers can lead to many adverse effects on human health, including reproductive and developmental toxicity, endocrine disruption, and cancer. Herein, we report for the first time that two plasticizers, bis(2-ethylhexyl) terephthalate (DEHT) and bis(2-ethylhexyl) phthalate (DEHP), have been isolated from the leaves of Capparis spinosa L. (the caper bush), a plant that is widely used in food seasonings and traditional medicine. 297 mg/kg of DEHT and 48 mg/kg of DEHP were isolated from dried and grounded C. spinosa L. leaves using column chromatography and semi-preparative high-performance liquid chromatography. Our study adds to the increase in the detection of plasticizers in our food and medicinal plants and to the alarming concern about their potential adverse effects on human health. 相似文献
942.
Jeongjoo Lee You‐Hyun Seo Sung‐Nam Kwon Do‐Hyung Kim Seokhoon Jang Hyeonwoo Jung Youngu Lee Hasitha Weerasinghe Taehyo Kim Jin Young Kim Doojin Vak Seok‐In Na 《Liver Transplantation》2019,9(36)
The record efficiency of the state‐of‐the‐art polymer solar cells (PSCs) is rapidly increasing, due to the discovery of high‐performance photoactive donor and acceptor materials. However, strong questions remain as to whether such high‐efficiency PSCs can be produced by scalable processes. This paper reports a high power conversion efficiency (PCE) of 13.5% achieved with single‐junction ternary PSCs based on PTB7‐Th, PC71BM, and COi8DFIC fabricated by slot‐die coating, which shows the highest PCE ever reported in PSCs fabricated by a scalable process. To understand the origin of the high performance of the slot‐die coated device, slot‐die coated photoactive films and devices are systematically investigated. These results indicate that the good performance of the slot‐die PSCs can be due to a favorable molecule‐structure and film‐morphology change by introducing 1,8‐diiodooctane and heat treatment, which can lead to improved charge transport with reduced carrier recombination. The optimized condition is then used for the fabrication of large‐area modules and also for roll‐to‐roll fabrication. The slot‐die coated module with 30 cm2 active‐area and roll‐to‐roll produced flexible PSC has shown 8.6% and 9.6%, respectively. These efficiencies are the highest in each category and demonstrate the strong potential of the slot‐die coated ternary system for commercial applications. 相似文献
943.
Zahra Rahmani Chang‐Jun Kim Mostafa Ghafouri Moghaddam Ehsan Rakhshani 《Entomological Research》2019,49(9):409-415
Occurrence of the family Ismaridae Thomson is recorded for the first time from Iran, represented by a single species, Ismarus rugulosus Förster, 1850. A series of diagnostic characters and morphometric ratios for this species is presented, as well as a distribution map throughout the Holarctic region. 相似文献
944.
Sung Won Lee Hyun Jung Park Seo Hyun Kim Sooyong Shin Kyung Hee Kim Sang Jae Park 《Animal cells and systems.》2019,23(3):184-191
We recently demonstrated that the polysaccharide component of the Korean medicinal herb Angelica gigas (immuno-stimulatory fraction of A. gigas; ISAg) induces anticancer effects in mice by activating natural killer (NK) and natural killer T (NKT) cells. However, it is unclear whether the use of ISAg in vivo can affect the differentiation of conventional T cells. Here, we investigated the effects of ISAg on the activation of conventional CD4+ and CD8+ T cells. We found that the administration of ISAg induced the polarization of CD4+ T cells toward the acquisition of the Th1 phenotype in vivo. Additionally, in mice treated with ISAg, CD8+ T cells produced more IFNγ than in control mice treated with PBS. Moreover, treatment with ISAg activated CD4+ and CD8+ T cells as well as NK and NKT cells, resulting in the secretion of Th1-type cytokines in a toll-like receptor 4 (TLR4)-dependent manner, implying that TLR4 is critical for an optimal Th1 response. Interestingly, ISAg treatment increased the number of Foxp3+ Treg cells, but not of Th2 cells, compared to control mice treated with PBS, indicating that ISAg possesses an immunomodulatory capacity that can control adaptive immune responses. Taken together, our results indicate that ISAg possesses a Th1-enhancing activity that could be used to treat Th2-mediated allergic immune diseases such as atopic dermatitis. 相似文献
945.
We studied the mechanism of sphingosylphosphorylcholine (SPC)-induced contraction in feline ileal smooth muscle cells. Western blotting revealed that G protein subtypes of Gαi1, Gαi3 and Gαo existed in feline ileum. Gαi3 antibody penetration into permeabilized cells decreased SPC-induced contraction. In addition, incubation of [35S]guanosine 5′-O-(3-thiotriphosphate) ([35S]GTPγS) with membrane fraction increased its binding to Gαi3 subtype after SPC treatment, suggesting that the signalling pathways invoked by SPC were mediated by Gαi3 protein. MAPK kinase (MEK) inhibitor PD98059 blocked the contraction significantly, but p38 mitogen-activated protein kinase (MAPK) inhibitor SB202190 did not. Chelerythrine and neomycin also inhibited the contraction. However, cotreatment of PD98059 and chelerythrine showed no significant difference. Phosphorylation of p44/42 MAPK was increased by SPC treatment, which was reversed by pretreatment of inhibitors of signalling molecules that decreased SPC-induced contraction previously. The same result was obtained in the assay of MAPK activity. 相似文献
946.
Nordihydroguaiaretic acid (NDGA), an inhibitor of lipoxygenase, inhibits the secretion of proteins and causes the redistribution of resident Golgi proteins into the endoplasmic reticulum (ER). In this study, the effect of NDGA on lipoprotein lipase (LPL) secretion was investigated in 3T3-L1 adipocytes, and compared with those of brefeldin A (BFA), a well-known fungal metabolite that exhibits similar ER-Golgi redistribution. Both BFA and NDGA blocked secretions of LPL. In the presence of BFA, the active and dimeric LPL was accumulated in adipocytes. After endoglycosidase H (endo H) digestion, the proportion of LPL subunits with partially endo H-sensitive oligosaccharide was significantly increased with BFA. However, in the presence of NDGA, the cellular LPL became inactive, and only the endo H-sensitive fraction of the LPL subunit was observed. An increase of the aggregated forms was observed in the fractions of the sucrose-density gradient ultracentrifugation. These properties of LPL in the NDGA-treated cells were similar to those of LPL that is retained in ER, and the effects of NDGA could not be reversed by BFA. These results indicate that the inhibitory mechanism of NDGA on the LPL secretion is functionally different from the ER-Golgi redistribution that is induced by BFA. 相似文献
947.
Jin-Ha Yoon Sung-Kyung Kim Ho-June Choi Soo-In Choi So-Youn Cha Sang-Baek Koh Hee-Taik Kang Song Vogue Ahn 《PloS one》2013,8(10)
Background
This study evaluated the relation between adiponectin and atherosclerosis in both genders, and investigated whether adiponectin provides useful additional information for assessing the risk of atherosclerosis.Methods
We measured serum adiponectin levels and other cardiovascular risk factors in 1033 subjects (454 men, 579 women) from the Korean Genomic Rural Cohort study. Carotid intima–media-thickness (CIMT) was used as measure of atherosclerosis. Odds ratios (ORs) with 95% confidence intervals (95% CI) were calculated using multiple logistic regression, and receiver operating characteristic curves (ROC), the category-free net reclassification improvement (NRI) and integrated discrimination improvement (IDI) were calculated.Results
After adjustment for conventional cardiovascular risk factors, such as age, waist circumference, smoking history, low-density and high-density lipoprotein cholesterol, triglycerides, systolic blood pressure and insulin resistance, the ORs (95%CI) of the third tertile adiponectin group were 0.42 (0.25–0.72) in men and 0.47 (0.29–0.75) in women. The area under the curve (AUC) on the ROC analysis increased significantly by 0.025 in men and 0.022 in women when adiponectin was added to the logistic model of conventional cardiovascular risk factors (AUC in men: 0.655 to 0.680, p = 0.038; AUC in women: 0.654 to 0.676, p = 0.041). The NRI was 0.32 (95%CI: 0.13–0.50, p<0.001), and the IDI was 0.03 (95%CI: 0.01–0.04, p<0.001) for men. For women, the category-free NRI was 0.18 (95%CI: 0.02–0.34, p = 0.031) and the IDI was 0.003 (95%CI: −0.002–0.008, p = 0.189).Conclusion
Adiponectin and atherosclerosis were significantly related in both genders, and these relationships were independent of conventional cardiovascular risk factors. Furthermore, adiponectin provided additional information to conventional cardiovascular risk factors regarding the risk of atherosclerosis. 相似文献948.
The precise mechanism of TGFβ1 signaling in the progression of non-alcoholic steatohepatitis (NASH) has remained unclear. In particular, a potential regulatory mechanism by which PKCδ affects profibrogenic gene expression had never been explored. In this study, therefore, the role of PKCδ in TGFβ1 mediated α-SMA expression was investigated using NASH model mice. In preparation of the NASH model, male C57BL6/J mice were fed a methionine-choline-deficient (MCD) diet for 3 weeks, after which time they were intraperitoneally injected with lipopolysaccharide (LPS). In addition, Tlr4Lps-d (CH3/HeJ) mice were used to demonstrate the TGFβ1 signaling’s dependency on TLR4 induction. Liver histology and hepatic hepatitis markers were investigated, and hepatic gene expression levels were determined by real-time PCR. Acute liver injury by LPS injection specifically elevated not only α-SMA expression but also phospho-PKCδ in this model. In contrast, Tlr4Lps-d (CH3/HeJ) and blockade of TGFβ1 receptor by SB431542 resulted in a significant reduction of PKCδ activation and α-SMA expression. Moreover, the TGFβ1-induced α-SMA production was significantly reduced by a specific PKCδ inhibitor. These findings suggested that PKCδ plays a critical role in TGFβ1-induced α-SMA production in a NASH model. Thus, this was the first demonstration of the involvement of PKCδ in the regulation of α-SMA expression in NASH liver tissues, and the impaired induction of PKCδ phosphorylation by LPS in a steatohepatitis condition. Interestingly, treatment by PKCδ inhibitor caused dramatic reduction of myofibroblast activation, indicating that PKCδ represents a promising target for treating NASH. 相似文献
949.
950.