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   17909篇
  免费   2203篇
  国内免费   4篇
电工技术   1366篇
综合类   403篇
化学工业   8940篇
金属工艺   254篇
机械仪表   397篇
建筑科学   670篇
矿业工程   167篇
能源动力   118篇
轻工业   1969篇
水利工程   125篇
石油天然气   74篇
无线电   357篇
一般工业技术   2958篇
冶金工业   164篇
原子能技术   28篇
自动化技术   2126篇
  2023年   639篇
  2022年   426篇
  2021年   780篇
  2020年   704篇
  2019年   601篇
  2018年   577篇
  2017年   424篇
  2016年   637篇
  2015年   798篇
  2014年   852篇
  2013年   1437篇
  2012年   588篇
  2011年   481篇
  2010年   805篇
  2009年   970篇
  2008年   457篇
  2007年   418篇
  2006年   304篇
  2005年   284篇
  2004年   236篇
  2003年   220篇
  2002年   127篇
  1998年   180篇
  1997年   135篇
  1996年   197篇
  1995年   184篇
  1994年   159篇
  1993年   219篇
  1992年   154篇
  1990年   151篇
  1989年   173篇
  1988年   138篇
  1987年   162篇
  1986年   182篇
  1985年   164篇
  1984年   169篇
  1983年   176篇
  1982年   155篇
  1981年   202篇
  1980年   165篇
  1979年   169篇
  1977年   147篇
  1976年   149篇
  1975年   202篇
  1974年   188篇
  1973年   365篇
  1972年   212篇
  1971年   150篇
  1970年   144篇
  1968年   153篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
Definition of the problem: In Austria the legal discussion on initiating and withdrawing artificial nutrition in incompetent patients has just begun. Arguments and conclusion: Legal regulations are lacking, but there appears to be agreement on accepting advance directives under specific criteria. This would mean that a presumed will and documented refusal of treatment and nutrition has to be respected by physicians. However, there is no consensus with regard to the “supposed will” of an incompetent patient to refuse treatment and nutrition. At present, surrogate decision making with regard to refusing life-sustaining treatment or nutrition is only accepted according to a declared and documented directive of the patient himself. When the patient’s will has to be “surmised” the protection of life has priority. In Austria this concept is based on the national constitution and its duty to protect life.  相似文献   
92.
Sleeping Beauty (SB) is the first DNA transposon employed for efficient transposition in vertebrate cells, opening new applications for genetic engineering and gene therapies. A transposon-based gene delivery system holds the favourable features of non-viral vectors and an attractive safety profile. Here, we employed SB to engineer HEK293 cells for optimizing the production of a chimpanzee Adenovector (chAd) belonging to the Human Mastadenovirus C species. To date, chAd vectors are employed in several clinical settings for infectious diseases, last but not least COVID-19. A robust, efficient and quick viral vector production could advance the clinical application of chAd vectors. To this aim, we firstly swapped the hAd5 E1 with chAd-C E1 gene by using the CRISPR/Cas9 system. We demonstrated that in the absence of human Ad5 E1, chimp Ad-C E1 gene did not support HEK293 survival. To improve chAd-C vector production, we engineered HEK293 cells to stably express the chAd-C precursor terminal protein (ch.pTP), which plays a crucial role in chimpanzee Adenoviral DNA replication. The results indicate that exogenous ch.pTP expression significantly ameliorate the packaging and amplification of recombinant chAd-C vectors thus, the engineered HEK293ch.pTP cells could represent a superior packaging cell line for the production of these vectors.  相似文献   
93.
The following paper demonstrates that programmed sequential graph grammars can be used in a systematic proceeding to specify the changes of high level intermediate data structures arising in a programming support environment, in which all tools work in an incremental and syntax-driven mode. In this paper we lay stress upon the way to get the specification rather than on the result of this process. Therefore, we give here some approach to “specification engineering” using graph grammars. This approach is influenced by the syntactical definition of the underlying language for Programming in the Small, the module concept etc. to be supported on one side but also by the idea of the user interface.  相似文献   
94.
95.
96.
Neuropathy development is a major dose-limiting side effect of anticancer treatments that significantly reduces patient’s quality of life. The inadequate pharmacological approaches for neuropathic pain management warrant the identification of novel therapeutic targets. Mitochondrial dysfunctions that lead to reactive oxygen species (ROS) increase, cytosolic Ca2+ imbalance, and lactate acidosis are implicated in neuropathic pain pathogenesis. It has been observed that in these deregulations, a pivotal role is played by the mitochondrial carbonic anhydrases (CA) VA and VB isoforms. Hence, preclinical studies should be conducted to assess the efficacy of two novel selenides bearing benzenesulfonamide moieties, named 5b and 5d, and able to inhibit CA VA and VB against paclitaxel-induced neurotoxicity in mice. Acute treatment with 5b and 5d (30–100 mg/kg, per os – p.o.) determined a dose-dependent and long-lasting anti-hyperalgesic effect in the Cold plate test. Further, repeated daily treatment for 15 days with 100 mg/kg of both compounds (starting the first day of paclitaxel injection) significantly prevented neuropathic pain development without the onset of tolerance to the anti-hyperalgesic effect. In both experiments, acetazolamide (AAZ, 100 mg/kg, p.o.) used as the reference drug was partially active. Moreover, ex vivo analysis demonstrated the efficacy of 5b and 5d repeated treatments in reducing the maladaptive plasticity that occurs to glia cells in the lumbar portion of the spinal cord and in improving mitochondrial functions in the brain and spinal cord that were strongly impaired by paclitaxel-repeated treatment. In this regard, 5b and 5d ameliorated the metabolic activity, as observed by the increase in citrate synthase activity, and preserved an optimal mitochondrial membrane potential (ΔΨ) value, which appeared depolarized in brains from paclitaxel-treated animals. In conclusion, 5b and 5d have therapeutic and protective effects against paclitaxel-induced neuropathy without tolerance development. Moreover, 5b and 5d reduced glial cell activation and mitochondrial dysfunction in the central nervous system, being a promising candidate for the management of neuropathic pain and neurotoxicity evoked by chemotherapeutic drugs.  相似文献   
97.
Amine oxidases are enzymes belonging to the class of oxidoreductases that are widespread, from bacteria to humans. The amine oxidase from Lathyrus cicera has recently appeared in the landscape of biocatalysis, showing good potential in the green synthesis of aldehydes. This enzyme catalyzes the oxidative deamination of a wide range of primary amines into the corresponding aldehydes but its use as a biocatalyst is challenging due to the possible inactivation that might occur at high product concentrations. Here, we show that the enzyme’s performance can be greatly improved by immobilization on solid supports. The best results are achieved using amino-functionalized magnetic microparticles: the immobilized enzyme retains its activity, greatly improves its thermostability (4 h at 75 °C), and can be recycled up to 8 times with a set of aromatic ethylamines. After the last reaction cycle, the overall conversion is about 90% for all tested substrates, with an aldehyde production ranging between 100 and 270 mg depending on the substrate used. As a proof concept, one of the aldehydes thus produced was successfully used for the biomimetic synthesis of a non-natural benzylisoquinoline alkaloid.  相似文献   
98.
Standard treatment for advanced non-small cell lung cancer (NSCLC) historically consisted of systemic cytotoxic chemotherapy until the early 2000s, when precision medicine led to a revolutionary change in the therapeutic scenario. The identification of oncogenic driver mutations in EGFR, ALK and ROS1 rearrangements identified a subset of patients who largely benefit from targeted agents. However, since the proportion of patients with druggable alterations represents a minority, the discovery of new potential driver mutations is still an urgent clinical need. We provide a comprehensive review of the emerging molecular targets in NSCLC and their applications in the advanced setting.  相似文献   
99.
Piezo1 channels are highly mechanically-activated cation channels that can sense and transduce the mechanical stimuli into physiological signals in different tissues including skeletal muscle. In this focused review, we summarize the emerging evidence of Piezo1 channel-mediated effects in the physiology of skeletal muscle, with a particular focus on the role of Piezo1 in controlling myogenic precursor activity and skeletal muscle regeneration and vascularization. The disclosed effects reported by pharmacological activation of Piezo1 channels with the selective agonist Yoda1 indicate a potential impact of Piezo1 channel activity in skeletal muscle regeneration, which is disrupted in various muscular pathological states. All findings reported so far agree with the idea that Piezo1 channels represent a novel, powerful molecular target to develop new therapeutic strategies for preventing or ameliorating skeletal muscle disorders characterized by an impairment of tissue regenerative potential.  相似文献   
100.
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