首页 | 本学科首页   官方微博 | 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   2124篇
  免费   0篇
  国内免费   1篇
电工技术   3篇
综合类   1篇
化学工业   9篇
金属工艺   1篇
机械仪表   38篇
建筑科学   5篇
能源动力   1篇
轻工业   40篇
水利工程   1篇
无线电   5篇
一般工业技术   4篇
冶金工业   2010篇
自动化技术   7篇
  2021年   2篇
  2019年   2篇
  2018年   1篇
  2017年   1篇
  2015年   1篇
  2013年   3篇
  2012年   1篇
  2011年   2篇
  2010年   5篇
  2009年   6篇
  2008年   5篇
  2007年   4篇
  2006年   7篇
  2005年   6篇
  2004年   3篇
  2003年   7篇
  2002年   7篇
  2001年   7篇
  2000年   15篇
  1999年   74篇
  1998年   602篇
  1997年   353篇
  1996年   222篇
  1995年   139篇
  1994年   99篇
  1993年   119篇
  1992年   12篇
  1991年   18篇
  1990年   15篇
  1989年   17篇
  1988年   23篇
  1987年   13篇
  1986年   16篇
  1985年   17篇
  1984年   1篇
  1983年   7篇
  1982年   7篇
  1981年   19篇
  1980年   27篇
  1978年   6篇
  1977年   66篇
  1976年   160篇
  1975年   3篇
  1973年   1篇
  1964年   1篇
  1955年   3篇
排序方式: 共有2125条查询结果,搜索用时 14 毫秒
31.
A unique feature of p21 that distinguishes it from the other cyclin-dependent kinase (CDK) inhibitors is its ability to associate with the proliferating cell nuclear antigen (PCNA), an auxiliary factor for DNA polymerases delta and epsilon. While it is now well established that inhibition of cyclin/CDK complexes by p21 can result in G1 cell cycle arrest, the consequences of p21/PCNA interaction on cell cycle progression have not yet been determined. Here, we show, using a tetracycline-regulated system, that expression of wild-type p21 in p53-deficient DLD1 human colon cancer cells inhibits DNA synthesis and causes G1 and G2 cell cycle arrest. Similar effects are observed in cells expressing p21CDK-, a mutant impaired in the interaction with CDKs, but not in cells expressing p21PCNA-, a mutant deficient for the interaction with PCNA. Analysis of cells treated with a p21-derived PCNA-binding peptide provides additional evidence that the growth inhibitory effects of p21 and p21CDK result from their ability to bind to PCNA. Our results suggest that p21 might inhibit cell cycle progression by two independent mechanisms, inhibition of cyclin/CDK complexes, and inhibition of PCNA function resulting in both G1 and G2 arrest.  相似文献   
32.
We investigated the role of prostaglandin E2 (PGE2) and its interactions with nitric oxide (NO) on cell death and NO-mediated cytotoxicity in the murine macrophage cell line J774. Stimulation of the J774 cells with lipopolysaccharide together with interferon-gamma resulted in a dose-dependent cytotoxicity and production of PGE2 and NO, measured as nitrite. Our results showed a linear correlation between PGE2 release and cytotoxicity. The cyclooxygenase (COX) inhibitor indomethacin completely inhibited PGE2 biosynthesis, without affecting NO production or cell death. This supports previous reports suggesting that overproduction of endogenous PGE2 is mainly the consequence of cell death and does not cause it. In contrast, the NO synthase inhibitor N(omega)-monomethyl-L-arginine (L-NMMA) gave a significant, though incomplete suppression of NO release and cell death. This points to the presence of other cytotoxic factors besides NO. To evaluate the toxic effect solely due to NO, macrophages were exposed to the NO donor S-nitroso-N-acetyl-D,L-penicillamine (SNAP). Incubation with SNAP also resulted in a concentration-dependent cell injury and PGE2 production. When exogenously added, PGE2 protected against SNAP-mediated cytotoxicity and simultaneously increased PGE2 release into the medium, without inducing COX-2. The cytoprotection and the stimulation of PGE2 release were both reversed by indomethacin. In conclusion, PGE2 biosynthesis may represent a mechanism by which inflammatory macrophages protect themselves against the cytotoxic effects of NO.  相似文献   
33.
The paper presents 30-year experience in treating 158 patients with congenital cystic diseases of the liver and bile ducts. Depending on the pattern of hepatobiliary lesions, the diagnostic value of techniques, such as ultrasound, computerized tomography, scintigraphy of the liver duodenoscopy with THCG was defined. Analyzing the late outcomes provided recommendations for the most optimal surgical management: cystic fenestration and tunneling in hepatic polycystosis, pericystectomy in solitary cysts of the liver, different varieties of bile draining operations in choledochal cysts and Caroli's disease.  相似文献   
34.
上罗拉皮圈是复杂的纺线生产流程中一个很小的细节。然而,由于它们对成纱质量有较大影响,必须对它们进行优先考虑。质量不是一个简单的问题,它包括多个方面(橡胶质量、正确的加工、定期的保养)。因此,皮圈的选择就像保养操作的自动化程度一样影响成本产生。本文将就这个问题进行讨论。  相似文献   
35.
Even simple and relatively safe provocation procedures like nasal allergen challenges, should aim to allow detection of positivity with the less possible discomfort to the patient. The objective of this work was to evaluate if the use of rhinomanometric measurements during nasal provocation procedures could allow a decrease in the total administered allergen dose, causing less symptoms to the patients but without increasing the number of false-negatives, comparatively to clinical scores or nasal peak-flow measurements. Our results showed that performing rhinomanometric measurements during nasal HDM challenge procedures can lead in many patients to a reduction in the total dose of allergen administered during the challenge, without loss of sensitivity or specificity. This allergen dose reduction translates in less time consumed during the provocation and less patients' discomfort.  相似文献   
36.
We studied whether ambulatory utilization review (UR) alters how many patients internal medicine residents refer to sub-specialists, and whether the effect persists without reinforcement. We compared referral rates of residents from a firm that held UR meetings (intervention firm residents, n = 20) with those of residents from a firm that did not (control firm residents, n = 21). We then compared referral rates of 17 intervention firm residents while they were participating in UR with their rates after not participating for at least 4 weeks. Intervention firm residents submitted 30% fewer referrals than control firm residents (9% vs 13%, p = .05). However, the effect was short-lived; after 4 weeks without UR, intervention firm resident referral rates were similar to control firm referral rates.  相似文献   
37.
38.
39.
Regulators of G protein signaling (RGS) proteins act as GTPase-activating proteins (GAPs) toward the alpha subunits of heterotrimeric, signal-transducing G proteins. RGS11 contains a G protein gamma subunit-like (GGL) domain between its Dishevelled/Egl-10/Pleckstrin and RGS domains. GGL domains are also found in RGS6, RGS7, RGS9, and the Caenorhabditis elegans protein EGL-10. Coexpression of RGS11 with different Gbeta subunits reveals specific interaction between RGS11 and Gbeta5. The expression of mRNA for RGS11 and Gbeta5 in human tissues overlaps. The Gbeta5/RGS11 heterodimer acts as a GAP on Galphao, apparently selectively. RGS proteins that contain GGL domains appear to act as GAPs for Galpha proteins and form complexes with specific Gbeta subunits, adding to the combinatorial complexity of G protein-mediated signaling pathways.  相似文献   
40.
Endoscopic treatment of chronic pancreatitis has drawn benefits from endoscopic procedures previously described for the main bile duct. Endotherapy is developing throughout the world. Cyst drainage procedures certainly represent the largest step forward in that non-surgical approach, whatever it is either direct (through the stomach or the duodenum) or indirect through the papilla in the duodenum. This procedure gives similar results to surgery with a lower morbidity. Pancreatic duct drainage associated with stone clearance is feasible and provides good results which have not yet been compared with those obtained thanks to surgery. Nonetheless, when the duct is not widely dilated it has been proven to be a satisfactory alternative to surgery. By contrast, chronic cholestasis does not appear to be a good indication of endotherapy.  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