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   1948篇
  免费   10篇
  国内免费   2篇
电工技术   4篇
综合类   9篇
化学工业   96篇
金属工艺   22篇
机械仪表   17篇
建筑科学   3篇
矿业工程   1篇
能源动力   15篇
轻工业   16篇
石油天然气   3篇
无线电   36篇
一般工业技术   113篇
冶金工业   1567篇
原子能技术   2篇
自动化技术   56篇
  2024年   12篇
  2023年   8篇
  2022年   15篇
  2021年   18篇
  2020年   10篇
  2019年   11篇
  2018年   14篇
  2017年   12篇
  2016年   13篇
  2015年   12篇
  2014年   10篇
  2013年   26篇
  2012年   18篇
  2011年   33篇
  2010年   17篇
  2009年   13篇
  2008年   21篇
  2007年   15篇
  2006年   9篇
  2005年   9篇
  2004年   7篇
  2003年   9篇
  2002年   5篇
  2001年   2篇
  2000年   5篇
  1999年   51篇
  1998年   490篇
  1997年   270篇
  1996年   196篇
  1995年   109篇
  1994年   81篇
  1993年   126篇
  1992年   12篇
  1991年   16篇
  1990年   12篇
  1989年   21篇
  1988年   17篇
  1987年   21篇
  1986年   14篇
  1985年   9篇
  1984年   4篇
  1983年   4篇
  1982年   8篇
  1981年   13篇
  1980年   23篇
  1978年   4篇
  1977年   33篇
  1976年   92篇
  1975年   5篇
  1955年   2篇
排序方式: 共有1960条查询结果,搜索用时 15 毫秒
31.
    
The dramatic experience with SARS-CoV-2 has alerted the scientific community to be ready to face new epidemics/pandemics caused by new variants. Among the therapies against the pandemic SARS-CoV-2 virus, monoclonal Antibodies (mAbs) targeting the Spike glycoprotein have represented good drugs to interfere in the Spike/ Angiotensin Converting Enzyme-2 (ACE-2) interaction, preventing virus cell entry and subsequent infection, especially in patients with a defective immune system. We obtained, by an innovative phage display selection strategy, specific binders recognizing different epitopes of Spike. The novel human antibodies specifically bind to Spike-Receptor Binding Domain (RBD) in a nanomolar range and interfere in the interaction of Spike with the ACE-2 receptor. We report here that one of these mAbs, named D3, shows neutralizing activity for virus infection in cell cultures by different SARS-CoV-2 variants and retains the ability to recognize the Omicron-derived recombinant RBD differently from the antibodies Casirivimab or Imdevimab. Since anti-Spike mAbs, used individually, might be unable to block the virus cell entry especially in the case of resistant variants, we investigated the possibility to combine D3 with the antibody in clinical use Sotrovimab, and we found that they recognize distinct epitopes and show additive inhibitory effects on the interaction of Omicron-RBD with ACE-2 receptor. Thus, we propose to exploit these mAbs in combinatorial treatments to enhance their potential for both diagnostic and therapeutic applications in the current and future pandemic waves of coronavirus.  相似文献   
32.
33.
The application of output value analysis, a type of benefit/cost analysis, to a psychiatric patient population is reported. A method for discounting the value of the program if a patient was readmitted within a year after discharge was introduced. The application of this discount factor reduces the value produced by the program and thereby reduces both productivity and effectiveness indices. When applied to groups known to differ in readmission rates, such as first admissions and readmissions or voluntary and involuntary admissions, the discount factor can accentuate group differences markedly. When selected diagnostic groups were compared, the discount factor could even reverse the relative standing of the groups.  相似文献   
34.
The Australian rodent, Uromys caudimaculatus, consists of two chromosome races. a) The Southern Race is characterized by the possession of two to twelve B-chromosomes. These vary considerably in size, morphology, and C- and G-banding characteristics, they behave as univalent at meiosis and are inherited in a random manner. b) The Northern Race lacks B-chromosomes, but possesses large blocks of distal C-positive heterochromatin on between 18 and 28 of the 46 chromosomes. The C-blocks may be entirely G-positive entirely G-negative, or G-banded, suggesting heterogeneity with the C-blocks. There is extensive variation both between and within populations of the northern race in the number and size of the distal heterochromatic blocks. There is no apparent difference between the races in chiasma frequency. The northern race does have much higher proportion of interstitial versus distal chiasmata, although it is probable that this is merely a reflection of lack of crossing over in the heterochromatic blocks rather than an actual shift of chiasma localisation within the euchromatin. Despite the extensive differences between the races in the amount and organization of constitutive heterochromatin, hybrids show no abnormalities at meiosis and they are fully fertile.  相似文献   
35.
36.
The complexation of piroxicam and 2-hydroxypropyl-β-cyclodextrin by means of supercritical CO2 has been investigated. The experiments were carried out by varying the temperature, pressure and contact time and introducing two different auxiliary agents: polyvinyl pyrrolidone or l-lysine.Cyclodextrins, which are widely used to solubilize a large variety of poorly soluble drugs, are often used in combination with some auxiliary agents to enhance the complexation efficiency of the conventional techniques. While many recent literature works report that supercritical carbon dioxide is a clean, non-toxic alternative to organic solvents, the use of auxiliary agents in the supercritical complexation process has been scarcely examined and still needs to be investigated.The inclusion complexes obtained in this work were analysed by means of the ‘differential solubility method’, differential scanning calorimetry and Fourier transform infrared spectroscopy. The results showed that the supercritical treatment could be successfully employed below 140-150 °C without incurring thermal degradation of the samples. While 66% inclusion efficiency could be obtained at 140 °C and 30 MPa for a mixture of piroxicam/2-hydroxypropyl-β-cyclodextrin (1:2 molar ratio), higher percentages of complexation (95% in the ternary samples with polyvinyl pyrrolidone and 89-91% in those with l-lysine) could be obtained at a lower temperature (130 °C) when auxiliary agents were employed.  相似文献   
37.
Alternating systems are models of computer programs whose behavior is governed by the actions of multiple agents with, potentially, different goals. Examples include control systems, resource schedulers, security protocols, auctions and election mechanisms. Proving properties about such systems has emerged as an important new area of study in formal verification, with the development of logical frameworks such as the alternating temporal logic ATL*. Techniques for model checking ATL* over finite-state systems have been well studied, but many important systems are infinite-state and thus their verification requires, either explicitly or implicitly, some form of deductive reasoning. This paper presents a theoretical framework for the analysis of alternating infinite-state systems. It describes models of computation, of various degrees of generality, and alternating-time logics such as ATL* and its variations. It then develops a proof system that allows to prove arbitrary ATL* properties over these infinite-state models. The proof system is shown to be complete relative to validities in the weakest possible assertion language. The paper then derives auxiliary proof rules and verification diagrams techniques and applies them to security protocols, deriving a new formal proof of fairness of a multi-party contract signing protocol where the model of the protocol and of the properties contains both game-theoretic and infinite-state (parameterized) aspects.  相似文献   
38.
One of the economic production quantity problems that have been of interest to researchers is the production with reworking of the imperfect items including waste most disposal form and vending the units. The available models in the literature assumed that the decay rate of the items is satisfied from three different points of view: (i) minimum demands of the customer’s requirement, (ii) demands to be enhanced for lower selling price and (iii) demands of the customers who are motivated by the advertisement. The model is developed over a finite random planning horizon, which is assumed to follow the exponential distribution with known parameters. The model has been illustrated with a numerical example, whose parametric inputs are estimated from market survey. Here the model is optimized by using a population varying genetic algorithm.  相似文献   
39.
Lanepitant is a high-affinity, selective neurokinin-1 receptor (NK-1) and is effective in the dural inflammation model of acute migraine. Lanepitant 30, 80, and 240 mg given orally was evaluated in a double-blind, placebo-controlled crossover study to determine its effect in reducing migraine pain and severity of associated symptoms. Outpatients treated four migraine headaches of moderate or severe pain intensity with study drug according to a randomization schedule. They recorded their pain intensity and severity of migraine-associated symptoms at 30, 60, 90, and 120 min. Although 53 patients were randomly allocated to a treatment sequence, only 40 patients completed all treatments. There was no statistically significant difference in improvement in migraine pain at any time for any of the treatments. Additionally, there was no change in severity of migraine-associated symptoms associated with lanepitant therapy. No adverse events could be attributed to lanepitant. Lanepitant was ineffective orally in treating acute migraine in this trial. This may be due to poor bioavailability during a migraine attack. Alternatively, the neurogenic inflammation hypothesis may not apply to migraine.  相似文献   
40.
The present investigation provide evidences from a non-human primate model that naturally occurring menopause predicts a prominent signature of age-related cognitive decline. Young and aged rhesus monkeys were tested on a delayed response (DR) task known to the sensitive to aging, and reproductive status was evaluated according to menstrual cyclicity and urinary hormone profiles. Peri-/postmenopausal monkeys exhibited significant DR impairments relative to either age-matched premenopausal females, or young control subjects. In addition, markers of endocrine decline in the aged animals were selectively correlated with behavioral performance measures that distinguished premenopausal and peri-/postmenopausal monkeys. These results document that menopause is coupled to cognitive decline in the monkey, and they establish a valuable primate model for defining the effects of endocrine aging on brain and behavioral function.  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