全文获取类型
收费全文 | 24941篇 |
免费 | 2211篇 |
国内免费 | 2279篇 |
出版年
2024年 | 26篇 |
2023年 | 210篇 |
2022年 | 349篇 |
2021年 | 804篇 |
2020年 | 642篇 |
2019年 | 752篇 |
2018年 | 768篇 |
2017年 | 632篇 |
2016年 | 859篇 |
2015年 | 1402篇 |
2014年 | 1622篇 |
2013年 | 1777篇 |
2012年 | 2293篇 |
2011年 | 2018篇 |
2010年 | 1396篇 |
2009年 | 1278篇 |
2008年 | 1583篇 |
2007年 | 1456篇 |
2006年 | 1345篇 |
2005年 | 1251篇 |
2004年 | 1154篇 |
2003年 | 1038篇 |
2002年 | 875篇 |
2001年 | 623篇 |
2000年 | 520篇 |
1999年 | 484篇 |
1998年 | 304篇 |
1997年 | 231篇 |
1996年 | 203篇 |
1995年 | 183篇 |
1994年 | 160篇 |
1993年 | 124篇 |
1992年 | 158篇 |
1991年 | 123篇 |
1990年 | 106篇 |
1989年 | 112篇 |
1988年 | 73篇 |
1987年 | 81篇 |
1986年 | 67篇 |
1985年 | 38篇 |
1984年 | 24篇 |
1983年 | 46篇 |
1982年 | 20篇 |
1981年 | 23篇 |
1980年 | 16篇 |
1979年 | 22篇 |
1978年 | 18篇 |
1977年 | 16篇 |
1976年 | 15篇 |
1970年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Zhao Jianlin Peng Wei Ran Yuxin Ge Huisheng Zhang Chen Zou Hong Ding Yubin Qi Hongbo 《Journal of physiology and biochemistry》2019,75(4):475-487
Journal of Physiology and Biochemistry - Preeclampsia (PE) is a hypertensive disease associated with increased endothelial cell dysfunction caused by systemic oxidative stress. Alpha-actinin-4... 相似文献
992.
Yaoming Li Wangwang Lv Lili Jiang Lirong Zhang Shiping Wang Qi Wang Kai Xue Bowen Li Peipei Liu Huan Hong Wangmu Renzen A Wang Caiyun Luo Zhenhua Zhang Tsechoe Dorji Neslihan Ta Zhezhen Wang Huakun Zhou Yanfen Wang 《Global Change Biology》2019,25(10):3438-3449
Changes in labile carbon (LC) pools and microbial communities are the primary factors controlling soil heterotrophic respiration (Rh) in warming experiments. Warming is expected to initially increase Rh but studies show this increase may not be continuous or sustained. Specifically, LC and soil microbiome have been shown to contribute to the effect of extended warming on Rh. However, their relative contribution is unclear and this gap in knowledge causes considerable uncertainty in the prediction of carbon cycle feedbacks to climate change. In this study, we used a two‐step incubation approach to reveal the relative contribution of LC limitation and soil microbial community responses in attenuating the effect that extended warming has on Rh. Soil samples from three Tibetan ecosystems—an alpine meadow (AM), alpine steppe (AS), and desert steppe (DS)—were exposed to a temperature gradient of 5–25°C. After an initial incubation period, soils were processed in one of two methods: (a) soils were sterilized then inoculated with parent soil microbes to assess the LC limitation effects, while controlling for microbial community responses; or (b) soil microbes from the incubations were used to inoculate sterilized parent soils to assess the microbial community effects, while controlling for LC limitation. We found both LC limitation and microbial community responses led to significant declines in Rh by 37% and 30%, respectively, but their relative contributions were ecosystem specific. LC limitation alone caused a greater Rh decrease for DS soils than AMs or ASs. Our study demonstrates that soil carbon loss due to Rh in Tibetan alpine soils—especially in copiotrophic soils—will be weakened by microbial community responses under short‐term warming. 相似文献
993.
Jin Zhou Xiao‐Hui Dong Feng‐Zhi Zhang Hui‐Min Zhu Tong Hao Xiao‐Xia Jiang Wei‐Bo Zheng Tao Zhang Pei‐Zhe Wang Hong Li Jie Na Chang‐Yong Wang 《Cell proliferation》2019,52(3)
Induced pluripotent stem cells (iPSCs) are reprogrammed somatic cells that gained self‐renewal and differentiation capacity similar to embryonic stem cells. Taking the precious opportunity of the TianZhou‐1 spacecraft mission, we studied the effect of space microgravity (µg) on the self‐renewal capacity of iPSCs. Murine iPSCs carrying pluripotency reporter Oct4‐GFP were used. The Oct4‐EGFP‐iPSCs clones were loaded into the bioreactor and exposed to μg in outer space for 14 days. The control experiment was performed in identical device but on the ground in earth gravity (1 g). iPSCs clones were compact and highly expressed Oct4 before launch. In μg condition, cells in iPSC clones spread out more rapidly than those in ground 1 g condition during the first 3 days after launch. However, in 1 g condition, as the cell density increases, the Oct4‐GFP signal dropped significantly during the following 3 days. Interestingly, in μg condition, iPSCs originated from the spread‐out clones during the first 3 days appeared to cluster together and reform colonies that activated strong Oct4 expression. On the other hand, iPSC clones in 1 g condition were not able to recover Oct4 expression after overgrown. Our study for the first time performed real‐time imaging on the proliferation process of iPSCs in space and found that in μg condition, cell behaviour appeared to be more dynamic than on the ground. 相似文献
994.
Jun-Li Yang Trong Tuan Dao Tran Thi Hien Ya-Min Zhao Yan-Ping Shi 《Bioorganic & medicinal chemistry letters》2019,29(10):1162-1167
The rhizomes of Homalomena occulta are called Qian-nian-jian in Traditional Chinese Medicine (TCM), which is widely consumed in China owing to its health benefits for the treatment of rheumatoid arthritis and for strengthening tendons and bones. A phytochemical investigation on this famous TCM yielded 19 sesquiterpenoids (1–19) with various carbocyclic skeletons including isodaucane (2, 8, and 9), guaiane (3), eudesmane (4 and 10–15), oppositane (5, 16, and 17), and aromadendrane (18 and 19) types. The structures of new compounds, Homalomenins A-E (1–5), were determined by diverse spectroscopic data. Compound 1 possessed a rare sesquiterpenoid skeleton and compound 5 represented the first example of 1,4-oxa-oppositane sesquiterpenoid. These isolates were evaluated for their inhibitory effects on COX-2 mRNA, COX-2 protein expression, and prostaglandin E2 (PGE2) production in Raw264.7 cells, which demonstrated that compounds 5, 18, 19 showed potent anti-inflammatory activity by suppressing LPS-induced COX-2 expression and PGE2 production in a dose-dependent manner. 相似文献
995.
996.
Suyoung Yoon Sung-Eun Kim Jong Hyun Kim Ina Yoon Phuong-Thao Tran Jihyae Ann Changhoon Kim Woong Sub Byun Sangkook Lee Sunghoon Kim Jiyoun Lee Jeewoo Lee 《Bioorganic & medicinal chemistry》2019,27(6):1099-1109
Leucyl-tRNA synthetase (LRS) plays an important role in amino acid-dependent mTORC1 signaling, which is known to be associated with cellular metabolism and proliferation. Therefore, LRS-targeting small molecules that can suppress mTORC1 activation may provide an alternative strategy to current anticancer therapy. In this work, we developed a library of leucyladenylate sulfate analogues by extensively modifying three different pharmacophoric regions comprising adenine, ribose and leucine. Several effective compounds were identified by cell-based mTORC1 activation assays and further tested for anticancer activity. The selected compounds mostly exhibited selective cytotoxicity toward five different cancer cell lines, supporting the hypothesis that the LRS-mediated mTORC1 pathway is a promising alternative target to current therapeutic approaches. 相似文献
997.
Shan Xiao Lin Wei Zongqin Hong Li Rao Yanliang Ren Jian Wan Lingling Feng 《Bioorganic & medicinal chemistry》2019,27(5):805-812
By using a new Fragment-Based Virtual Screen strategy, two series of novel FBA-II inhibitors (thiourea derivatives) were de novo discovered based on the active site of fructose-1, 6-bisphosphate aldolase from Cyanobacterial (CyFBA). In comparison, most of the N-(2-benzoylhydrazine-1-carbonothioyl) benzamide derivatives (L14~L22) exhibit higher CyFBA-II inhibitory activities compared to N-(phenylcarbamothioyl) benzamide derivatives (L1~L13). Especially, compound L14 not only shows higher CyFBA-II activity (Ki?=?0.65?μM), but also exhibits most potent in vivo activity against Synechocystis sp. PCC 6803 (EC50?=?0.09?ppm), higher (7-fold) than that of our previous inhibitor (EC50?=?0.6?ppm). The binding modes of compound L14 and CyFBA-II were further elucidated by jointly using DOX computational protocol, MM-PBSA and site-directed mutagenesis assays. The positive results suggest that strategy adopted in this study was promising to rapidly discovery the potent inhibitors with novel scaffolds. The satisfactory algicide activities suggest that the thiourea derivatives is very likely to be a promising lead for the development of novel specific algicides to solve Cyanobacterial harmful algal blooms (CHABs). 相似文献
998.
Ho Shin Kim Van-Hai Hoang Mannkyu Hong Kyung Chul Kim Jihyae Ann Cong-Truong Nguyen Ji Hae Seo Hoon Choi Jun Yong Kim Kyu-Won Kim Woong Sub Byun Sangkook Lee Seungbeom Lee Young-Ger Suh Jie Chen Hyun-Ju Park Tae-Min Cho Ji Young Kim Jeewoo Lee 《Bioorganic & medicinal chemistry》2019,27(7):1370-1381
On the basis of deguelin, a series of the B,C-ring truncated surrogates with N-substituted amide linkers were investigated as HSP90 inhibitors. The structure activity relationship of the template was studied by incorporating various substitutions on the nitrogen of the amide linker and examining their HIF-1α inhibition. Among them, compound 57 showed potent HIF-1α inhibition and cytotoxicity in triple-negative breast cancer lines in a dose-dependent manner. Compound 57 downregulated expression and phosphorylation of major client proteins of HSP90 including AKT, ERK and STAT3, indicating that its antitumor activity was derived from the inhibition of HSP90 function. The molecular modeling of 57 demonstrated that 57 bound well to the C-terminal ATP-binding pocket in the open conformation of the hHSP90 homodimer with hydrogen bonding and pi-cation interactions. Overall, compound 57 is a potential antitumor agent for triple-negative breast cancer as a HSP90 C-terminal inhibitor. 相似文献
999.
1000.