全文获取类型
收费全文 | 12326篇 |
免费 | 910篇 |
国内免费 | 383篇 |
专业分类
13619篇 |
出版年
2024年 | 26篇 |
2023年 | 103篇 |
2022年 | 295篇 |
2021年 | 400篇 |
2020年 | 294篇 |
2019年 | 357篇 |
2018年 | 409篇 |
2017年 | 322篇 |
2016年 | 428篇 |
2015年 | 685篇 |
2014年 | 798篇 |
2013年 | 872篇 |
2012年 | 1089篇 |
2011年 | 1028篇 |
2010年 | 655篇 |
2009年 | 547篇 |
2008年 | 738篇 |
2007年 | 650篇 |
2006年 | 536篇 |
2005年 | 492篇 |
2004年 | 509篇 |
2003年 | 397篇 |
2002年 | 322篇 |
2001年 | 257篇 |
2000年 | 213篇 |
1999年 | 210篇 |
1998年 | 98篇 |
1997年 | 69篇 |
1996年 | 57篇 |
1995年 | 65篇 |
1994年 | 60篇 |
1993年 | 44篇 |
1992年 | 82篇 |
1991年 | 76篇 |
1990年 | 55篇 |
1989年 | 48篇 |
1988年 | 36篇 |
1987年 | 24篇 |
1986年 | 27篇 |
1985年 | 25篇 |
1984年 | 12篇 |
1983年 | 17篇 |
1982年 | 13篇 |
1980年 | 20篇 |
1979年 | 19篇 |
1978年 | 12篇 |
1977年 | 19篇 |
1975年 | 14篇 |
1974年 | 16篇 |
1970年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Yea Eun Lee Sang Kuk Byun Sunhee Shin Ja Young Jang Byong-il Choi Dongsun Park Jeong Hee Jeon Sang-Seop Nahm Jong-Koo Kang Seock-Yeon Hwang Jong-Choon Kim Yun-Bae Kim 《Experimental Animals》2008,57(1):19-25
The present study was conducted to elucidate the susceptibility of embryos and fetuses at different gestational stages to the maternal stress in mice. Groups of pregnant ICR mice were subjected to daily 12-h restraint stress, taped in the supine position on a plastic board, on gestational days (GD) 1-4, 5-8, 9-12 and 13-16, respectively. Caesarean sections were performed on gestational day 18, and the fetuses were weighed and examined for morphological defects. During the daily restraint for 4 days, the maternal body weights markedly decreased. Although the body weights recovered gradually after termination of the stress, the recovery was not full until the final stage of pregnancy. Interestingly, restraint stress caused growth retardation of the fetuses, leading to a significant decrease in their body weights, and increased early and late resorptions of embryos and fetuses according to the stress periods. Although the preceding (GD1-4) and concurrent (GD5-8) stresses did not affect embryonic implantation, restraint stress on GD9-12 caused cleft palate. Whereas vertebral abnormalities, mainly bipartite ossification, were observed only in animals stressed on GD5-8, abnormalities of sternebrae, exhibiting asymmetric or bipartite ossification, were enhanced by the stress at all of the gestational stages. On the other hand, the incidence of other malformations including renal malposition and costal abnormalities was not increased by stress at any of the 4 stages. Taken together, the results suggest that intensive restraint stress influences the maternal body weight resulting in growth retardation and increased mortality of embryos and fetuses, in addition to gestational stage-specific ventricular dilatation, cleft palate and sternal abnormalities. 相似文献
992.
Jaeyoung Ko Hoosang Hwang Jungwook Chin Dongyup Hahn Jaehwan Lee Inho Yang Kyoungjin Shin Jungyeob Ham Heonjoong Kang 《Bioorganic & medicinal chemistry letters》2010,20(20):6017-6019
A novel class of natural PPAR agonists, 2,4-dimethyl-4-hydroxy-16-phenylhexadecanoic acid 1,4-lactone (1), were discovered in marine natural product libraries. The synthesis of 1 was accomplished starting from vinylmethyl ketone. Ring formation of the α,γ dialkyl γ-lactone was achieved via the stereo-controlled reaction of a ketyl radical anion with a chiral methacrylate. In the PPAR agonistic assay, the most potent of the four stereoisomers had EC50 values of 12 μM for mPPARα, 9 μM for mPPARδ and >100 μM for mPPARγ. 相似文献
993.
Kiyoon Kang Sangkyu Park Young Soon Kim Sungbeom Lee Kyoungwhan Back 《Applied microbiology and biotechnology》2009,83(1):27-34
Serotonin derivatives belong to a class of phenylpropanoid amides found at low levels in a wide range of plant species. Representative
serotonin derivatives include feruloylserotonin (FS) and 4-coumaroylserotonin (CS). Since the first identification of serotonin
derivatives in safflower seeds, their occurrence, biological significance, and pharmacological properties have been reported.
Recently, serotonin N-hydroxycinnamoyl transferase (SHT), which is responsible for the synthesis of serotonin derivatives, was cloned from pepper
(Capsicum annuum) and characterized in terms of its enzyme kinetics. Using the SHT gene, many attempts have been made to either increase the
level of serotonin derivatives in transgenic plants or produce serotonin derivatives de novo in microbes by dual expression of key genes such as SHT and 4-coumarate-CoA ligase (4CL). Due to the strong antioxidant activity
and other therapeutic properties of serotonin derivatives, these compounds may have high potential in treatment and prophylaxis,
as cosmetic ingredients, and as major components of functional foods or feeds that have health-improving effects. This review
examines the biosynthesis of serotonin derivatives, corresponding enzymes, heterologous production in plants or microbes,
and their applications. 相似文献
994.
The interactions of chlorogenic acid and ferulic acid with human serum albumin (HSA) have been investigated by fluorescence and Fourier transformed infrared (FT-IR) spectrometry. Fluorescence results showed that one molecule of protein combined with one molecule of drugs at the molar ratio of drug to HSA ranging from 1 to 10, and their binding affinities (KA) are 4.37 x 10(4) M(-1) and 2.23 x 10(4) M(-1) for chlorogenic acid and ferulic acid, respectively. The primary binding site for chlorogenic acid is most likely located on IIA and that for ferulic acid in IIIA. The main mechanism of protein fluorescence quenching was static quenching process. Combining the curve-fitting results of infrared amide I and amide III bands, the alterations of protein secondary structure after drug complexation were estimated. With increasing the drug concentration, the protein alpha-helix structure decreased gradually and the reduction of protein alpha-helix structure reached about 7% and 5% for protein binding with chlorogenic acid and ferulic acid individually at the drug to protein molar ratio of 30. This indicated a partial unfolding of HSA in the presence of the two acids. From the fluorescence and FT-IR results, the binding mode was discussed. 相似文献
995.
Kim H Lee SJ Park JY Park YW Kim HS Kang HY Hur BK Ryu YW Han SI Kim JS 《Journal of microbiology (Seoul, Korea)》2004,42(1):25-31
Sf9 cells have obvious advantages for the conventional production technology of vaccine. They are useful tools for high concentration and large-scale cultures. Sf9 cells were grown to maximal concentration, 8 x 10(6) cells/ml in a 500ml spinner flask, with a doubling time at the exponentially growing phase of 24.5 hours, using serum-free media. To explore the ability of Sf9 cells to be infected by the Japanese encephalitis (JE) virus Beijing-1 strain, Sf9 cells were infected with the virus. By 4-5 days post-infection, 10-15% of the Sf9 cells showed cytopathic effect (CPE), from granularity to the formation of syncytia and multinucleated giant cells continuously observed over a period of 35 days. Positive fluorescent reactions were detected in 30-40% of cells infected with the JE virus Beijing-1 strain, and the uninfected Sf9 cells were completely negative. Virus particles, propagated in Sf9 and Vero cells, were concentrated by sedimentation on 40% trehalose cushions by ultracentrifugation, and showed identical patterns of viral morphogenesis. Complete virus particles, 40 to 50 nm in diameter, were observed, and JE virus envelope (E) proteins, at 53 kDa, were found in the western blot analysis to the anti-JE virus E protein monoclonal antibody and reacted as a magenta band in the same position to the glycoprotein staining. To evaluate whether the infectious virus was produced in Sf9 cells inoculated with the JE virus Beijing-1 stain, Sf9 cells were inoculated with the virus, and sample harvested every 5 days. The titers of the JE virus Beijing-1 strain rose from 1.0 x 10(5) to 1.5 x 10(6) pfu/ml. The infected Sf9 cells could be sub-cultured in serum-free medium, with no change in the plaque sizes formed by the JE virus Beijing-1 strain in the plaque assay. It is suggested that the ability of the JE virus Beijing-1 strain to infect Sf9 cells in serum-free media will provide a useful insect cell system, where the JE virus replication, cytopathogenicity and vaccine immunogen can be studied. 相似文献
996.
997.
Qingxin Li Angela Shuyi Chen Shovanlal Gayen CongBao Kang 《Biomolecular NMR assignments》2013,7(2):129-132
Intracellular proteinases (ISPs) are the main component of the bacilli degradome and a distinctive class in different bacilli. An intracellular proteinase inhibitor of the bacteria Bacillus subtillis was shown to regulate the activity of ISP-1. To study the structure of this inhibitor, we report the resonance assignment for this protein with 119 amino acid. The data will allow us to perform structural study on this inhibitor to understand its mechanism for ISP-1 inhibition. 相似文献
998.
Kalthoum Tizaoui Jae Won Yang Keum Hwa Lee Ji Hong Kim Minseok Kim Sojung Yoon Yeonwoo Jung Joon Beom Park Kitae An Hyeok Choi Donggyu Song HyunTaek Jung Seongmin Ahn Taeho Yuh Hee Min Choi Jae Ha Ahn Younjuong Kim Sanghyun Jee Hyeongsun Lee Soohwa Jin Jun-Gu Kang Bohyun Koo Joo Yeop Lee Kyoung Min Min Wonseok Yoo Hyeong Jun Rhyu Yeonjung Yoon Min Ho Lee Sung Eun Kim Jimin Hwang Ai Koyanagi Louis Jacob Seoyeon Park Jae Il Shin Lee Smith 《International journal of biological sciences》2022,18(9):3731
YKL-40, a chitinase-3-like protein 1 (CHI3L1) or human cartilage glycoprotein 39 (HC gp-39), is expressed and secreted by various cell-types including macrophages, chondrocytes, fibroblast-like synovial cells and vascular smooth muscle cells. Its biological function is not well elucidated, but it is speculated to have some connection with inflammatory reactions and autoimmune diseases. Although having important biological roles in autoimmunity, there were only attempts to elucidate relationships of YKL-40 with a single or couple of diseases in the literature. Therefore, in order to analyze the relationship between YKL-40 and the overall diseases, we reviewed 51 articles that discussed the association of YKL-40 with rheumatoid arthritis, psoriasis, systemic lupus erythematosus, Behçet disease and inflammatory bowel disease. Several studies showed that YKL-40 could be assumed as a marker for disease diagnosis, prognosis, disease activity and severity. It is also shown to be involved in response to disease treatment. However, other studies showed controversial results particularly in the case of Behçet disease activity. Therefore, further studies are needed to elucidate the exact role of YKL-40 in autoimmunity and to investigate its potential in therapeutics. 相似文献
999.
See-Hyoung Park Sang Jae Noh Kyoung Min Kim Jun Sang Bae Keun Sang Kwon Sung Hoo Jung Jung Ryul Kim Ho Lee Myoung Ja Chung Woo Sung Moon Myoung Jae Kang Kyu Yun Jang 《Translational oncology》2015,8(4):239-249
BACKGROUND: Poly(ADP-ribose) polymerase 1 (PARP1), γH2AX, BRCA1, and BRCA2 are conventional molecular indicators of DNA damage in cells and are often overexpressed in various cancers. In this study, we aimed, using immunohistochemical detection, whether the co-expression of PARP1, γH2AX, BRCA1, and BRCA2 in breast carcinoma (BCA) tissue can provide more reliable prediction of survival of BCA patients. MATERIALS AND METHODS: We investigated immunohistochemical expression and prognostic significance of the expression of PARP1, γH2AX, BRCA1, and BRCA2 in 192 cases of BCAs. RESULTS: The expression of these four molecules predicted earlier distant metastatic relapse, shorter overall survival (OS), and relapse-free survival (RFS) by univariate analysis. Multivariate analysis revealed the expression of PARP1, γH2AX, and BRCA2 as independent poor prognostic indicators of OS and RFS. In addition, the combined expressional pattern of BRCA1, BRCA2, PARP1, and γH2AX (CSbbph) was an additional independent prognostic predictor for OS (P < .001) and RFS (P < .001). The 10-year OS rate was 95% in the CSbbph-low (CSbbph scores 0 and 1) subgroup, but that was only 35% in the CSbbph-high (CSbbph score 4) subgroup. CONCLUSION: This study has demonstrated that the individual and combined expression patterns of PARP1, γH2AX, BRCA1, and BRCA2 could be helpful in determining an accurate prognosis for BCA patients and for the selection of BCA patients who could potentially benefit from anti-PARP1 therapy with a combination of genotoxic chemotherapeutic agents. 相似文献
1000.
Leuschner F Dutta P Gorbatov R Novobrantseva TI Donahoe JS Courties G Lee KM Kim JI Markmann JF Marinelli B Panizzi P Lee WW Iwamoto Y Milstein S Epstein-Barash H Cantley W Wong J Cortez-Retamozo V Newton A Love K Libby P Pittet MJ Swirski FK Koteliansky V Langer R Weissleder R Anderson DG Nahrendorf M 《Nature biotechnology》2011,29(11):1005-1010
Excessive and prolonged activity of inflammatory monocytes is a hallmark of many diseases with an inflammatory component. In such conditions, precise targeting of these cells could be therapeutically beneficial while sparing many essential functions of the innate immune system, thus limiting unwanted effects. Inflammatory monocytes-but not the noninflammatory subset-depend on the chemokine receptor CCR2 for localization to injured tissue. Here we present an optimized lipid nanoparticle and a CCR2-silencing short interfering RNA that, when administered systemically in mice, show rapid blood clearance, accumulate in spleen and bone marrow, and localize to monocytes. Efficient degradation of CCR2 mRNA in monocytes prevents their accumulation in sites of inflammation. Specifically, the treatment attenuates their number in atherosclerotic plaques, reduces infarct size after coronary artery occlusion, prolongs normoglycemia in diabetic mice after pancreatic islet transplantation, and results in reduced tumor volumes and lower numbers of tumor-associated macrophages. 相似文献