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   141914篇
  免费   12615篇
  国内免费   7273篇
电工技术   6688篇
技术理论   6篇
综合类   11822篇
化学工业   24545篇
金属工艺   7513篇
机械仪表   5419篇
建筑科学   8318篇
矿业工程   2893篇
能源动力   3716篇
轻工业   12349篇
水利工程   3058篇
石油天然气   5721篇
武器工业   1000篇
无线电   13238篇
一般工业技术   19654篇
冶金工业   5021篇
原子能技术   2752篇
自动化技术   28089篇
  2024年   214篇
  2023年   1557篇
  2022年   2847篇
  2021年   4443篇
  2020年   3025篇
  2019年   2818篇
  2018年   3141篇
  2017年   3663篇
  2016年   5298篇
  2015年   6420篇
  2014年   8329篇
  2013年   9064篇
  2012年   7393篇
  2011年   7366篇
  2010年   6138篇
  2009年   7522篇
  2008年   7488篇
  2007年   8889篇
  2006年   8568篇
  2005年   7155篇
  2004年   5465篇
  2003年   5322篇
  2002年   4714篇
  2001年   3451篇
  2000年   3610篇
  1999年   3378篇
  1998年   2741篇
  1997年   2620篇
  1996年   2780篇
  1995年   2889篇
  1994年   2637篇
  1993年   1618篇
  1992年   1625篇
  1991年   1148篇
  1990年   897篇
  1989年   783篇
  1988年   717篇
  1987年   422篇
  1986年   281篇
  1985年   432篇
  1984年   478篇
  1983年   467篇
  1982年   367篇
  1981年   440篇
  1980年   310篇
  1979年   132篇
  1978年   126篇
  1977年   83篇
  1975年   61篇
  1962年   64篇
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
101.
A self-nanoemulsifying drug delivery system (SNEDDS) was developed to enhance the absorption of heparin after oral administration, in which heparin was compounded with phospholipids to achieve better fat solubility in the form of heparin-phospholipid (HEP-Pc) complex. HEP-Pc complex was prepared using the solvent evaporation method, which increased the solubility of heparin in n-octanol. The successful preparation of HEP-Pc complex was confirmed by differential scanning calorimetry (DSC), Fourier-transform infrared (FT-IR) spectroscopy, NMR, and SEM. A heparin lipid microemulsion (HEP-LM) was prepared by high-pressure homogenization and characterized. HEP-LM can enhance the absorption of heparin after oral administration, significantly prolong activated partial thromboplastin time (APTT) and thrombin time (TT) in mice, and reduce fibrinogen (FIB) content. All these outcomes indicate that HEP-LM has great potential as an oral heparin formulation.  相似文献   
102.
游惠明 《中国油脂》2021,46(6):98-101
为探明不同种源地香叶树作为油料树种的开发价值,采集了全国6省20县市的香叶树果实,对香叶树全果、果肉及籽的油脂含量及脂肪酸组成进行了分析,并采用ward法对不同种源地香叶树籽油脂肪酸进行了聚类分析。结果表明:香叶树全果、果肉以及籽的平均油脂含量分别为43.31%、42.38%及46.12%;全果油脂肪酸组成以月桂酸、油酸和癸酸为主;果肉油以油酸和棕榈酸为主;而籽油则以月桂酸和癸酸为主,月桂酸含量为53.20%~70.30%,月桂酸和癸酸总含量达76.40%~90.10%;聚类分析将不同种源地香叶树分为3大类,云南省、贵州省及广西省的香叶树属低月桂酸类型,福建省、江西省及湖南省的香叶树属中高月桂酸型。香叶树可作为生产中碳链脂肪酸的新晋树种,福建省的香叶树籽油脂含量高,且籽油中月桂酸含量高,作为中碳链脂肪酸的原料地具有明显的开发优势。  相似文献   
103.
104.
105.
引入句法依存信息到原方面术语,提出一种新的方面术语表示方法,利用Glove词向量表示单词以及单词与单词之间的依存关系,构造出包含句法依存信息的依存关系邻接矩阵和依存关系表示矩阵,利用图卷积神经网络和多头注意力机制将句法依存信息融入到方面术语中,使得方面术语表达与上下文结构高度相关。将改进后的方面词术语表示替换到现有模型后,模型泛化能力得到有效提升。对比试验和分析结果表明:该方法具有有效性和泛化性。  相似文献   
106.
Prostate cancer (PCa) is globally the second most diagnosed cancer type and the most common cause of cancer-related deaths in men. Family history of PCa, hereditary breast and ovarian cancer (HBOC) and Lynch syndromes (LS), are among the most important risk factors compared to age, race, ethnicity and environmental factors for PCa development. Hereditary prostate cancer (HPCa) has the highest heritability of any major cancer in men. The proportion of PCa attributable to hereditary factors has been estimated in the range of 5–15%. To date, the genes more consistently associated to HPCa susceptibility include mismatch repair (MMR) genes (MLH1, MSH2, MSH6, and PMS2) and homologous recombination genes (BRCA1/2, ATM, PALB2, CHEK2). Additional genes are also recommended to be integrated into specific research, including HOXB13, BRP1 and NSB1. Importantly, BRCA1/BRCA2 and ATM mutated patients potentially benefit from Poly (ADP-ribose) polymerase PARP inhibitors, through a mechanism of synthetic lethality, causing selective tumor cell cytotoxicity in cell lines. Moreover, the detection of germline alterations in MMR genes has therapeutic implications, as it may help to predict immunotherapy benefits. Here, we discuss the current knowledge of the genetic basis for inherited predisposition to PCa, the potential target therapy, and the role of active surveillance as a management strategy for patients with low-risk PCa. Finally, the current PCa guideline recommendations are reviewed.  相似文献   
107.
The evolution of new SARS-CoV-2 variants around the globe has made the COVID-19 pandemic more worrisome, further pressuring the health care system and immunity. Novel variations that are unique to the receptor-binding motif (RBM) of the receptor-binding domain (RBD) spike glycoprotein, i. e. L452R-E484Q, may play a different role in the B.1.617 (also known as G/452R.V3) variant's pathogenicity and better survival compared to the wild type. Therefore, a thorough analysis is needed to understand the impact of these mutations on binding with host receptor (RBD) and to guide new therapeutics development. In this study, we used structural and biomolecular simulation techniques to explore the impact of specific mutations (L452R-E484Q) in the B.1.617 variant on the binding of RBD to the host receptor ACE2. Our analysis revealed that the B.1.617 variant possesses different dynamic behaviours by altering dynamic-stability, residual flexibility and structural compactness. Moreover, the new variant had altered the bonding network and structural-dynamics properties significantly. MM/GBSA technique was used, which further established the binding differences between the wild type and B.1.617 variant. In conclusion, this study provides a strong impetus to develop novel drugs against the new SARS-CoV-2 variants.  相似文献   
108.
Forty samples of optically active falcarindiol analogues are synthesized by using the easily available C2 symmetric (R)- and (S)-1,1’-binaphth-2-ol (BINOL) in combination with Ti(OiPr)4, Zn powder and EtI. Their anticancer activities on Hccc-9810, HepG2, MDA-MB-231, Hela, MG-63 and H460 cells are assayed to elucidate their structure-activity relationships. These results showed that the falcarindiol analogue (3R,8S)- 2 i with the terminal double bond has the most potent anti-proliferation effect on Hccc-9810 cells with IC50 value of 0.46 μM. The falcarindiol analogue (3R,8S)- 2 i can induce obvious Hccc-9810 cell apoptosis in a concentration-dependent manner by Hoechst staining and flow cytometry analysis. The proposed mechanism suggests that the falcarindiol analogue (3R,8S)- 2 i increases LDH release and MDA content, and reduces the levels of SOD activity, which lead to the accumulation of oxidative stress and induce apoptosis in Hccc-9810 cells.  相似文献   
109.
Considering the advent of antibiotic resistance, the study of bacterial metabolic behavior stimulated by novel antimicrobial agents becomes a relevant tool to elucidate involved adaptive pathways. Profiling of volatile metabolites was performed to monitor alterations of bacterial metabolism induced by biosynthesized silver nanoparticles (bio-AgNPs). Escherichia coli, Enterococcus faecalis, Klebsiella pneumoniae and Proteus mirabilis were isolated from pressure ulcers, and their cultures were prepared in the presence/absence of bio-AgNPs at 12.5, 25 and 50 µg mL−1. Headspace solid phase microextraction associated to gas chromatography–mass spectrometry was the employed analytical platform. At the lower concentration level, the agent promoted positive modulation of products of fermentation routes and bioactive volatiles, indicating an attempt of bacteria to adapt to an ongoing suppression of cellular respiration. Augmented response of aldehydes and other possible products of lipid oxidative cleavage was noticed for increasing levels of bio-AgNPs. The greatest concentration of agent caused a reduction of 44 to 80% in the variety of compounds found in the control samples. Pathway analysis indicated overall inhibition of amino acids and fatty acids routes. The present assessment may provide a deeper understanding of molecular mechanisms of bio-AgNPs and how the metabolic response of bacteria is untangled.  相似文献   
110.
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