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   8363篇
  免费   341篇
  国内免费   23篇
电工技术   77篇
综合类   13篇
化学工业   1196篇
金属工艺   240篇
机械仪表   322篇
建筑科学   127篇
矿业工程   2篇
能源动力   272篇
轻工业   516篇
水利工程   37篇
石油天然气   18篇
无线电   1354篇
一般工业技术   1284篇
冶金工业   2379篇
原子能技术   87篇
自动化技术   803篇
  2024年   6篇
  2023年   70篇
  2022年   104篇
  2021年   162篇
  2020年   96篇
  2019年   130篇
  2018年   174篇
  2017年   154篇
  2016年   206篇
  2015年   168篇
  2014年   247篇
  2013年   462篇
  2012年   386篇
  2011年   487篇
  2010年   333篇
  2009年   383篇
  2008年   331篇
  2007年   281篇
  2006年   232篇
  2005年   244篇
  2004年   174篇
  2003年   187篇
  2002年   171篇
  2001年   132篇
  2000年   131篇
  1999年   170篇
  1998年   896篇
  1997年   431篇
  1996年   354篇
  1995年   229篇
  1994年   177篇
  1993年   204篇
  1992年   68篇
  1991年   76篇
  1990年   74篇
  1989年   75篇
  1988年   64篇
  1987年   58篇
  1986年   38篇
  1985年   35篇
  1984年   24篇
  1983年   22篇
  1982年   26篇
  1981年   25篇
  1980年   30篇
  1979年   6篇
  1978年   7篇
  1977年   32篇
  1976年   116篇
  1975年   9篇
排序方式: 共有8727条查询结果,搜索用时 15 毫秒
31.
The dynamic deformation behavior of ultrafine-grained low-carbon steels fabricated by equal-channel angular pressing (ECAP) was investigated in this study. Dynamic torsional tests, using a torsional Kolsky bar, were conducted on four steel specimens, two of which were annealed at 480 °C after ECAP, and then the test data were compared in terms of microstructures, tensile properties, and adiabatic shear-band formation. The equal-channel angular pressed specimen consisted of very fine, equiaxed grains of 0.2 to 0.3 μm in size, which were slightly coarsened after annealing. The dynamic torsional test results indicated that maximum shear stress decreased with increasing annealing time, whereas fracture shear strain increased. Some adiabatic shear bands were observed at the gage center of the dynamically deformed torsional specimen. Their width was smaller in the equal-channel angular pressed specimen than in the 1-hour-annealed specimen, but they were not found in the 24-hour-annealed specimen. Ultrafine, equiaxed grains of 0.05 to 0.2 μm in size were formed inside the adiabatic shear band, and their boundaries had characteristics of high-angle grain boundaries. These phenomena were explained by dynamic recrystallization due to a highly localized plastic strain and temperature rise during dynamic deformation.  相似文献   
32.
33.
34.
Despite advances in medicine, mortality due to sepsis has not decreased. Pulsed electromagnetic field (PEMF) therapy is emerging as an alternative treatment in many inflammation-related diseases. However, there are few studies on the application of PEMF therapy to sepsis. In the current study, we examined the effect of PEMF therapy on a mouse model of lipopolysaccharide (LPS)-induced septic shock. Mice injected with LPS and treated with PEMF showed higher survival rates compared with the LPS group. The increased survival was correlated with decreased levels of pro-inflammatory cytokine mRNA expression and lower serum nitric oxide levels and nitric oxide synthase 2 mRNA expression in the liver compared with the LPS group. In the PEMF + LPS group, there was less organ damage in the liver, lungs, spleen, and kidneys compared to the LPS group. To identify potential gene targets of PEMF treatment, microarray analysis was performed, and the results showed that 136 genes were up-regulated, and 267 genes were down-regulated in the PEMF + LPS group compared to the LPS group. These results suggest that PEMF treatment can dramatically decrease septic shock through the reduction of pro-inflammatory cytokine gene expression. In a clinical setting, PEMF may provide a beneficial effect for patients with bacteria-induced sepsis and reduce septic shock-induced mortality.  相似文献   
35.
The transient receptor potential vanilloid 1 (TRPV1) ion channel plays an important role in the peripheral nociceptive pathway. TRPV1 is a polymodal receptor that can be activated by multiple types of ligands and painful stimuli, such as noxious heat and protons, and contributes to various acute and chronic pain conditions. Therefore, TRPV1 is emerging as a novel therapeutic target for the treatment of various pain conditions. Notably, various peptides isolated from venomous animals potently and selectively control the activation and inhibition of TRPV1 by binding to its outer pore region. This review will focus on the mechanisms by which venom-derived peptides interact with this portion of TRPV1 to control receptor functions and how these mechanisms can drive the development of new types of analgesics.  相似文献   
36.
Rapid, chip-scale, and cost-effective single particle detection of biological agents is of great importance to human health and national security. We report real-time, high-throughput detection and sizing of individual, low-index polystyrene nanoparticles and H1N1 virus. Our widefield, common path interferometer detects nanoparticles and viruses over a very large sensing area, orders of magnitude larger than competing techniques. We demonstrate nanoparticle detection and sizing down to 70 nm in diameter. We clearly size discriminate nanoparticles with diameters of 70, 100, 150, and 200 nm. We also demonstrate detection and size characterization of hundreds of individual H1N1 viruses in a single experiment.  相似文献   
37.
38.
We present a hierarchical test methodology for testing a SOC with heterogeneous cores, including the 1149.1-wrapped, P1500-wrapped, and BIST memory cores. We propose an 1149.1-based hierarchical test manager that also provides P1500 test control signals. This scheme includes a memory BIST interface, providing both serial and parallel access ports for BIST circuits. Our approach offers low area and pin overhead, and high flexibility  相似文献   
39.
Small-cell lung cancer (SCLC) is the most aggressive form of lung cancer and the leading cause of global cancer-related mortality. Despite the earlier identification of membrane-proximal cleavage of cell adhesion molecule 1 (CADM1) in cancers, the role of the membrane-bound fragment of CAMD1 (MF-CADM1) is yet to be clearly identified. In this study, we first isolated MF-CADM1-specific fully human single-chain variable fragments (scFvs) from the human synthetic scFv antibody library using the phage display technology. Following the selected scFv conversion to human immunoglobulin G1 (IgG1) scFv-Fc antibodies (K103.1–4), multiple characterization studies, including antibody cross-species reactivity, purity, production yield, and binding affinity, were verified. Finally, via intensive in vitro efficacy and toxicity evaluation studies, we identified K103.3 as a lead antibody that potently promotes the death of human SCLC cell lines, including NCI-H69, NCI-H146, and NCI-H187, by activated Jurkat T cells without severe endothelial toxicity. Taken together, these findings suggest that antibody-based targeting of MF-CADM1 may be an effective strategy to potentiate T cell-mediated SCLC death, and MF-CADM1 may be a novel potential therapeutic target in SCLC for antibody therapy.  相似文献   
40.
A novel scheme investigating a radial-basis-function neural network (RBFNN) with variable structure control (VSC) for electrohydraulic servosystems subject to huge uncertainties is presented. Although the VSC possesses some advantages (e.g., fast response, less sensitive to uncertainties, and easy implementation), the chattering control input often occurs. The reason for a chattering control input is that the switching control in the VSC is used to cope with the uncertainties. The larger the uncertainties which arise, the larger switching control occurs. In this paper, an RBFNN is employed to model the uncertainties caused by parameter variations, friction, external load, and controller. A new weight updating law using a revision of e-modification by a time varying dead zone can achieve an exponential stability without the assumption of persistent excitation for the uncertainties or radial basis function. Then, an RBFNN-based VSC is constructed such that some part of uncertainties are tackled, that the tracking performance is improved, and that the level of chattering control input is attenuated. Finally, the stability of the overall system is verified by the Lyapunov stability criterion  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