首页 | 官方网站   微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2161篇
  免费   65篇
  国内免费   6篇
工业技术   2232篇
  2022年   7篇
  2021年   116篇
  2020年   29篇
  2019年   39篇
  2018年   57篇
  2017年   58篇
  2016年   80篇
  2015年   51篇
  2014年   72篇
  2013年   156篇
  2012年   109篇
  2011年   116篇
  2010年   120篇
  2009年   88篇
  2008年   101篇
  2007年   89篇
  2006年   64篇
  2005年   68篇
  2004年   58篇
  2003年   56篇
  2002年   56篇
  2001年   38篇
  2000年   22篇
  1999年   29篇
  1998年   29篇
  1997年   25篇
  1996年   33篇
  1995年   26篇
  1994年   30篇
  1993年   24篇
  1992年   13篇
  1991年   22篇
  1990年   27篇
  1989年   16篇
  1988年   27篇
  1987年   22篇
  1986年   19篇
  1985年   21篇
  1984年   31篇
  1983年   29篇
  1982年   23篇
  1981年   27篇
  1980年   16篇
  1979年   17篇
  1978年   10篇
  1977年   15篇
  1976年   11篇
  1975年   10篇
  1972年   4篇
  1971年   4篇
排序方式: 共有2232条查询结果,搜索用时 15 毫秒
1.
ABSTRACT

Nine sowing densities of linseed were compared in a two-year experiment. Self-regulation of the density of a linseed stand resulted in a differentiated branching of the plants. The number of capsules on a linseed shoot, as well as seeds in the capsule, and the number of seeds from the shoot were highly varied from year to year, and there is even a stronger differentiation in the weight of 1000 seeds. Linear relationships were noted between the mass of seeds from the linseed plant and the number of capsules. The yield of linseed was affected by both factors. An increasing sowing rate reduced the seed yield from the shoot and the plant. At lower seeding rates, the lateral shoots contributed in the seeds yield of the plant to a higher degree compared to the main ones.  相似文献   
2.
RCAS1 is a protein that participates in regulation of the tumor microenvironment and its immune responses, all in order to evade the immune system. The aim of this study was to analyze RCAS1 expression in urothelial bladder cancer cells (and in fibroblasts and macrophages of the tumor stroma) and its relationship with the histological pattern of malignancy. Eighty-three postcystectomy patients were enrolled. We analyzed the histological maturity (grade), progress (pT stage), tissue invasion type (TIT), nonclassic differentiation number (NDN), and the ability to metastasize (pN). The expression of RCAS1 protein was analyzed by immunohistochemistry. Indicators of histological malignancy were observed solely in association with the RCAS1 expression in cells in the border parts (BPs) of the tumor. Histological malignancy of the tumor, indicated by the pT and pN, and metastasis-free survival time, correlated significantly with RCAS1 expression in tumor neoplastic cells, whereas malignancy determined by grade, TIT, and NDN correlated with RCAS1 expression in fibroblasts and macrophages in the tumor microenvironment. These findings suggest that the increased RCAS1 expression depends on its cellular source and that RCAS1 expression itself is a component of various signaling pathways. The immune escape occurs within the tumor BPs, where the increase in the RCAS1 expression occurs within tumor cells and stromal cells in its microenvironment. We conclude that the histological pattern of tumor malignancy, indicated by grade, TIT, NDN, pT, and pN is a morphological indicator of immune escape.  相似文献   
3.
4.
Histone deacetylase inhibitors (HDIs) are promising anti-cancer agents that inhibit proliferation of many types of cancer cells including breast carcinoma (BC) cells. In the present study, we investigated the influence of the Notch1 activity level on the pharmacological interaction between cisplatin (CDDP) and two HDIs, valproic acid (VPA) and suberoylanilide hydroxamic acid (SAHA, vorinostat), in luminal-like BC cells. The type of drug–drug interaction between CDDP and HDIs was determined by isobolographic analysis. MCF7 cells were genetically modified to express differential levels of Notch1 activity. The cytotoxic effect of SAHA or VPA was higher on cells with decreased Notch1 activity and lower for cells with increased Notch1 activity than native BC cells. The isobolographic analysis demonstrated that combinations of CDDP with SAHA or VPA at a fixed ratio of 1:1 exerted additive or additive with tendency toward synergism interactions. Therefore, treatment of CDDP with HDIs could be used to optimize a combined therapy based on CDDP against Notch1-altered luminal BC. In conclusion, the combined therapy of HDIs and CDDP may be a promising therapeutic tool in the treatment of luminal-type BC with altered Notch1 activity.  相似文献   
5.
1,25-Dihydroxycholecalciferol, the hormonally active vitamin D3 metabolite, is known to exhibit therapeutic effects against breast cancer, mainly by lowering the expression of estrogen receptors and aromatase activity. Previously, the safety of the vitamin D active metabolite (24R)-1,24-dihydroxycholecalciferol (PRI-2191) and 1,25(OH)2D3 analog PRI-2205 was tested, and the in vitro activity of these analogs against different cancer cell lines was studied. We determined the effect of the two vitamin D compounds on anastrozole (An) activity against breast cancer based on antiproliferative activity, ELISA, flow cytometry, enzyme inhibition potency, PCR, and xenograft study. Both the vitamin D active metabolite and synthetic analog regulated the growth of not only estrogen receptor-positive cells (T47D and MCF-7, in vitro and in vivo), but also hormone-independent cancer cells such as SKBR-3 (HER-2-positive) and MDA-MB-231 (triple-negative), despite their relatively low VDR expression. Combined with An, PRI-2191 and PRI-2205 significantly inhibited the tumor growth of MCF-7 cells. Potentiation of the antitumor activity in combined treatment of MCF-7 tumor-bearing mice is related to the reduced activity of aromatase by both An (enzyme inhibition) and vitamin D compounds (switched off/decreased aromatase gene expression, decreased expression of other genes related to estrogen signaling) and by regulation of the expression of the estrogen receptor ERα and VDR.  相似文献   
6.
Deregulated melanogenesis is involved in melanomagenesis and melanoma progression and resistance to therapy. Vitamin D analogs have anti-melanoma activity. While the hypercalcaemic effect of the active form of Vitamin D (1,25(OH)2D3) limits its therapeutic use, novel Vitamin D analogs with a modified side chain demonstrate low calcaemic activity. We therefore examined the effect of secosteroidal analogs, both classic (1,25(OH)2D3 and 25(OH)D3), and novel relatively non-calcemic ones (20(OH)D3, calcipotriol, 21(OH)pD, pD and 20(OH)pL), on proliferation, colony formation in monolayer and soft-agar, and mRNA and protein expression by melanoma cells. Murine B16-F10 and hamster Bomirski Ab cell lines were shown to be effective models to study how melanogenesis affects anti-melanoma treatment. Novel Vitamin D analogs with a short side-chain and lumisterol-like 20(OH)pL efficiently inhibited rodent melanoma growth. Moderate pigmentation sensitized rodent melanoma cells towards Vitamin D analogs, and altered expression of key genes involved in Vitamin D signaling, which was opposite to the effect on heavily pigmented cells. Interestingly, melanogenesis inhibited ligand-induced Vitamin D receptor translocation and ligand-induced expression of VDR and CYP24A1 genes. These findings indicate that melanogenesis can affect the anti-melanoma activity of Vitamin D analogs in a complex manner.  相似文献   
7.
8.
9.
The paper presents a method of settling time minimization in switched capacitor (SC) circuits. This problem has been discussed in recent papers because of high-frequency applications of SC networks. In comparison with the methods elaborated up to now and limited to biquads, the method presented in this paper can be used for an SC circuit containing an arbitrary number of operational amplifiers coupled together in each switching state and modelled as ideal transconductances. the fifth-order ladder bilinear SC filter is considered for illustration of the method and SPICE simulations.  相似文献   
10.
The authors presented the cases of two children with inflammatory myofibroblastic (IMF) tumor and reviewed the literature to facilitate the preoperative recognition, delineate the clinical features, and describe the natural history of this entity. The first child had IMF tumor arising from the mesentery of the small intestine. He presented with an abdominal mass associated with severe inflammatory response manifested by fever, impaired growth, thrombocytosis, and microcytic, hypochromic anemia. After surgical resection, his fever resolved and his growth rate and the laboratory abnormalities normalized. Five months after initial diagnosis, the fever, anemia, and thrombocytosis recurred along with two tumors arising from the omentum and the abdominal soft tissue. After the second surgery, he remains free of recurrent disease for 30 months. The second child presented with a lung mass that was radiologically indistinguishable from pulmonary sequestration. After surgical resection, she remains free of recurrent disease for 18 months. IMF tumor should be considered in any solid tumor that occurs in association with a chronic inflammatory response. IMF tumor should also be considered in the differential diagnosis of pulmonary sequestration.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司    京ICP备09084417号-23

京公网安备 11010802026262号