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   12937篇
  免费   918篇
  国内免费   9篇
电工技术   81篇
综合类   8篇
化学工业   5133篇
金属工艺   133篇
机械仪表   305篇
建筑科学   454篇
矿业工程   18篇
能源动力   320篇
轻工业   3159篇
水利工程   110篇
石油天然气   69篇
无线电   478篇
一般工业技术   1715篇
冶金工业   620篇
原子能技术   35篇
自动化技术   1226篇
  2024年   41篇
  2023年   180篇
  2022年   919篇
  2021年   1031篇
  2020年   418篇
  2019年   428篇
  2018年   478篇
  2017年   497篇
  2016年   543篇
  2015年   441篇
  2014年   577篇
  2013年   877篇
  2012年   836篇
  2011年   949篇
  2010年   721篇
  2009年   673篇
  2008年   615篇
  2007年   581篇
  2006年   446篇
  2005年   336篇
  2004年   290篇
  2003年   252篇
  2002年   240篇
  2001年   149篇
  2000年   94篇
  1999年   136篇
  1998年   127篇
  1997年   119篇
  1996年   113篇
  1995年   78篇
  1994年   63篇
  1993年   63篇
  1992年   67篇
  1991年   49篇
  1990年   40篇
  1989年   36篇
  1988年   37篇
  1987年   34篇
  1986年   42篇
  1985年   37篇
  1984年   27篇
  1983年   24篇
  1982年   17篇
  1981年   18篇
  1980年   20篇
  1979年   19篇
  1978年   20篇
  1977年   14篇
  1976年   7篇
  1975年   11篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Immune checkpoint inhibitors (ICIs) have demonstrated remarkable efficacy in a growing number of malignancies. However, overcoming primary or secondary resistances is difficult due to pharmacokinetics issues and side effects associated with high systemic exposure. Local or regional expression of monoclonal antibodies (mAbs) using gene therapy vectors can alleviate this problem. In this work, we describe a high-capacity adenoviral vector (HCA-EFZP-aPDL1) equipped with a mifepristone-inducible system for the controlled expression of an anti-programmed death ligand 1 (PD-L1) blocking antibody. The vector was tested in an immune-competent mouse model of colorectal cancer based on implantation of MC38 cells. A single local administration of HCA-EFZP-aPDL1 in subcutaneous lesions led to a significant reduction in tumor growth with minimal release of the antibody in the circulation. When the vector was tested in a more stringent setting (rapidly progressing peritoneal carcinomatosis), the antitumor effect was marginal even in combination with other immune-stimulatory agents such as polyinosinic-polycytidylic acid (pI:C), blocking mAbs for T cell immunoglobulin, mucin-domain containing-3 (TIM-3) or agonistic mAbs for 4-1BB (CD137). In contrast, macrophage depletion by clodronate liposomes enhanced the efficacy of HCA-EFZP-aPDL1. These results highlight the importance of addressing macrophage-associated immunoregulatory mechanisms to overcome resistance to ICIs in the context of colorectal cancer.  相似文献   
12.
Two samples of poly(diethoxyphosphazene) (PDEP) having very different molecular weights have been studied by viscometry and size exclusion chromatography in THF solution. The results obtained, together with light scattering data of these samples, allow the calculation of the Mark-Houwink constants a=0.65 and K=2.5 10-4 in THF at 25°C. The method of calculation employed takes into account the great polydispersity of the samples. The characteristic ratio of the unperturbed dimensions was also calculated giving Cn = r2o/n2 18, a value slightly higher than those previously reported for poly(dihexoxyphosphazene), Cn13 and poly (dichlorophosphazene), Cn13.5.  相似文献   
13.
Worldwide, cervical cancer is the second most common cancer in women, after breast cancer. The prevalence of this malignant disease is estimated at 1.4 million cases worldwide, causing about 290,000 deaths and 500,000 new cases per year, of which 80% correspond to women living in developing countries. In this work we propose a family of ordered models for basal cells of the cervix corresponding to different stages ranging from normal cells to the formation of precancerous lesions. We analyse the first member of the family analytically and for the second member we developed a non-standard numerical method in order to extract some biological information.  相似文献   
14.
The effect of Mg-doping and Li overstoichiometry on the structural stability of LiCoO2 powders has been investigated with emphasis to voltammetric properties. Microparticle cyclic voltammetry (CV) conducted in caustic NaOH to best simulate a non-aqueous electrolyte shows a marked improvement of the structure stability of doped LiCoO2. In contrast to the unsubstituted LiCoO2 sample which shows voltammetric peaks associated to the well-known two-phase domain and monoclinic distortion reactions, in Li1.08Mg0.06CoO2, LiMg0.06CoO2 and Li1.08CoO2 samples these peaks are strongly suppressed providing direct evidence for the existence of a stable solid solution with negligible phase transitions in the reversible intercalation region (3.8-4.2 V vs. Li) as well as in the overcharged region. The effect is higher with Mg-doping, irrespective of the Li overstoichiometry. However, the concomitant presence of Mg and Li excess in the structure is important for obtaining small particle sizes. Since Mg-doping induces a quasi metallic behavior in the samples, whereas the Li excess may provide an higher initial capacity, it is suggested that the Li1.08Mg0.06CoO2 composition may be of interest as positive cathode for advanced Li-ion batteries.  相似文献   
15.
16.
A case situation arising in a normal interaction among people is the baseline for discussing properties of the theory of viewpoints. In particular we consider how to ensure agreement on the meaning of certain utterances by agents who have different perspectives on the situation, while maintaning other knowledge as private. We argue that communication should be modeled as adding facts to the common knowledge of agents. We introduce the principle of 'referent sharing' in communications and argue that common knowledge resulting from communication should only use constants whose referent is manifest to the parties involved.  相似文献   
17.
We present empirical results of an auction-based algorithm for dynamic allocation of tasks to robots. The results have been obtained both in simulation and using real robots. A distinctive feature of our algorithm is its robustness to uncertainties and to robot malfunctions that happen during task execution, when unexpected obstacles, loss of communication, and other delays may prevent a robot from completing its allocated tasks. Therefore tasks not yet achieved are resubmitted for bids every time a task has been completed. This provides an opportunity to improve the allocation of the remaining tasks, enabling the robots to recover from failures and reducing the overall time for task completion.  相似文献   
18.
Missing data are omnipresent in forestry research, and this poses problems in the analysis of primary data. Many statistical problems have been viewed as missing data problems. To cope with incomplete data, several methods are currently being used. They are all based on assumptions some of which might not be valid in a particular case. The choice mostly depends on the objective of the study. Considerable mensuration research is motivated by the need for yield projections that can support forest management decisions. This paper is focused on a new approach for filling gaps in diameter measurements on standing tree boles. Dealing with this problem, an attempt was made to examine the applicability of artificial neural network models for missing data estimation and to use the estimated values in the subsequent analysis. The procedure that should be followed in the development of such models is outlined. The results show good performance of the examined ANN models compared to regression treatments for missing data and ANN models demonstrate their adequacy and potential for filling gaps in diameter measurements on standing tree boles. The ANN models applied in this study are sufficiently general and have great potential to be applicable for estimating the missing values of many variables in environmental applications.  相似文献   
19.
An innovative application focused on the segmentation of decay zones from images of stone materials is presented. The adopted numerical approach to extract decay regions from the color images of monuments provides a tool that helps experts analyze degraded regions by contouring them. In this way even if the results of the proposed procedure depend on the evaluation of experts, the approach can be a contribution to improving the efficiency of the boundary detection process. The segmentation is a process that allows an image to be divided into disjoint zones so that partitioned zones contain homogeneous characteristics. The numerical method, used to segment color images, is based on the theory of interface evolution, which is described by the eikonal equation. We adopted the fast marching technique to solve the upwind finite difference approximation of the eikonal equation. The fast marching starts from a seed point in the region of interest and generates a front which evolves according to a specific speed function until the boundary of the region is identified. We describe the segmentation results obtained with two speed functions, attained by the image gradient computation and color information about the object of interest. Moreover, we present the extension of the working modality of the method by introducing the possibility to extract the regions not only in a local way but also in a global way on the entire image. In this case, in order to improve the segmentation efficiency the application of the fast marching technique starts with more seed points defined as seed regions. The study case concerns the impressive remains of the Roman Theatre in the city of Aosta (Italy). In the image segmentation process the color space LabLab is utilized.  相似文献   
20.
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