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   1569篇
  免费   54篇
电工技术   25篇
综合类   2篇
化学工业   389篇
金属工艺   21篇
机械仪表   30篇
建筑科学   66篇
矿业工程   2篇
能源动力   32篇
轻工业   210篇
水利工程   7篇
石油天然气   4篇
无线电   122篇
一般工业技术   255篇
冶金工业   282篇
原子能技术   7篇
自动化技术   169篇
  2023年   7篇
  2022年   21篇
  2021年   23篇
  2020年   14篇
  2019年   14篇
  2018年   20篇
  2017年   36篇
  2016年   26篇
  2015年   23篇
  2014年   24篇
  2013年   45篇
  2012年   60篇
  2011年   78篇
  2010年   73篇
  2009年   57篇
  2008年   75篇
  2007年   85篇
  2006年   49篇
  2005年   58篇
  2004年   39篇
  2003年   45篇
  2002年   35篇
  2001年   35篇
  2000年   48篇
  1999年   40篇
  1998年   90篇
  1997年   63篇
  1996年   38篇
  1995年   47篇
  1994年   37篇
  1993年   22篇
  1992年   22篇
  1991年   24篇
  1990年   22篇
  1989年   20篇
  1988年   16篇
  1987年   17篇
  1986年   10篇
  1985年   12篇
  1984年   9篇
  1983年   16篇
  1982年   12篇
  1981年   6篇
  1980年   13篇
  1979年   9篇
  1978年   7篇
  1977年   10篇
  1976年   17篇
  1973年   4篇
  1925年   4篇
排序方式: 共有1623条查询结果,搜索用时 15 毫秒
1.
Processing lithium-ion battery (LIB) electrode dispersions with water as the solvent during primary drying offers many advantages over N-methylpyrrolidone (NMP). An in-depth analysis of the comparative drying costs of LIB electrodes is discussed for both NMP- and water-based dispersion processing in terms of battery pack $/kWh. Electrode coating manufacturing and capital equipment cost savings are compared for water vs. conventional NMP organic solvent processing. A major finding of this work is that the total electrode manufacturing costs, whether water- or NMP-based, contribute about 8–9% of the total pack cost. However, it was found that up to a 2?×?reduction in electrode processing (drying and solvent recovery) cost can be expected along with a $3–6?M savings in associated plant capital equipment (for a plant producing 100,000 10-kWh Plug-in Hybrid Electric Vehicle (PHEV) batteries) using water as the electrode solvent. This paper shows a different perspective in that the most important benefits of aqueous electrode processing actually revolve around capital equipment savings and environmental stewardship and not processing cost savings.  相似文献   
2.
3.
A paralytic peptide, psi-conotoxin Piiie has been purified and characterized from Conus purpurascens venom. Electrophysiological studies indicate that the peptide inhibits the nicotinic acetylcholine receptor (nAChR). However, the peptide does not block the binding of alpha-bungarotoxin, a competitive nAChR antagonist. Thus, psi-conotoxin Piiie appears to inhibit the receptor at a site other than the acetylcholine-binding site. As ascertained by sequence analysis, mass spectrometry, and chemical synthesis, the peptide has the following covalent structure: HOOCCLYGKCRRYOGCSSASCCQR* (O = 4-trans hydroxyproline; * indicates an amidated C-terminus). The disulfide connectivity of the toxin is unrelated to the alpha- or the alphaA-conotoxins, the Conus peptide families that are competitive inhibitors of the nAChR, but shows homology to the mu-conotoxins (which are Na+ channel blockers).  相似文献   
4.
The purpose of this study was to determine the long-term results of allogeneic bone marrow transplantation for chronic myeloid leukemia. A retrospective analysis was carried out of the outcome of 373 consecutive transplants performed at 38 European institutions between 1980 and 1988 and reported to the registry of the European Group for Blood and Marrow Transplantation. All transplants were carried out for first chronic phase of chronic myelogenous leukemia using unmanipulated marow cells from HLA-identical sibling donors. The probability of survival and leukemia-free survival at 8 years were 54% (95% CI: 49-59) and 47% (95% CI: 41-52) respectively. The probabilities of developing acute GVHD (II-IV) at 100 days and chronic GVHD at 4 years after transplant were 47% (95% CI: 41-53) and 52% (95% CI: 46-58) respectively. The probabilities of transplant-related mortality and leukemic relapse 8 years after BMT were 41% (95% CI: 36-48) and 19% (95% CI: 14-25), respectively. Transplant within 12 months of diagnosis was associated with reduced transplant-related mortality (34 vs 45%, P = 0.013) and resulted in improved leukemia-free survival (52 vs 44%, P = 0.03). The probability of relapse was significantly reduced in patients who developed chronic GVHD (RR = 0.33, P = 0.004). The probability of relapse occurring more than 2 years after transplant was increased more than five-fold in patients transplanted from a male donor (RR = 5.5, P = 0.006). Sixty-seven patients in hematologic remission were studied for residual disease by two-step RT/PCR for BCR-ABL mRNA and 61 (91%) tested negative. We conclude that bone marrow transplantation can induce long-term survival in approximately one-half of CML patients; the majority of survivors have no evidence of residual leukemia cells when studied by molecular techniques. The probability of late relapse is increased with use of a male donor.  相似文献   
5.
The selection of valuable features is crucial in pattern recognition. In this paper we deal with the issue that part of features originate from directional instead of common linear data. Both for directional and linear data a theory for a statistical modeling exists. However, none of these theories gives an integrated solution to problems, where linear and directional variables are to be combined in a single, multivariate probability density function. We describe a general approach for a unified statistical modeling, given the constraint that variances of the circular variables are small. The method is practically evaluated in the context of our online handwriting recognition system frog on hand and the so-called tangent slope angle feature. Recognition results are compared with two alternative modeling approaches. The proposed solution gives significant improvements in recognition accuracy, computational speed and memory requirements.  相似文献   
6.
7.
A system based on ROOT for handling the micro-DST of the BaBar experiment is described. The purpose of the Kanga system is to have micro-DST data available in a format well suited for data distribution within a world-wide collaboration with many small sites. The design requirements, implementation and experience in practice after three years of data taking by the BaBar experiment are presented.  相似文献   
8.
Wang  Z. Bodtker  E. Jacobsen  G. 《Electronics letters》1995,31(18):1591-1592
Channel crosstalk effects in wavelength-multiplexed subcarrier-multiplexing video transmission systems due to cross-phase modulation are investigated. The crosstalk level depends on the spacing of optical channels. For analogue CATV transmissions in the 1.5 μm window using normal singlemode fibre, it is shown that the number of achievable optical channels is severely limited by cross-phase modulation for typical system parameters  相似文献   
9.
10.
BACKGROUND: Modular polyketide synthases (PKSs) are large multifunctional proteins that catalyze the biosynthesis of structurally complex bioactive products. The modular organization of PKSs has allowed the application of a combinatorial approach to the synthesis of novel polyketides via the manipulation of these biocatalysts at the genetic level. The inherent specificity of PKSs for their natural substrates, however, may place limits on the spectrum of molecular diversity that can be achieved in polyketide products. With the aim of further understanding PKS specificity, as a route to exploiting PKSs in combinatorial synthesis, we chose to examine the substrate specificity of a single intact domain within a bimodular PKS to investigate its capacity to utilize unnatural substrates. RESULTS: We used a blocked mutant of a bimodular PKS in which formation of the triketide product could occur only via uptake and processing of a synthetic diketide intermediate. By introducing systematic changes in the native diketide structure, by means of the synthesis of unnatural diketide analogs, we have shown that the ketosynthase domain of module 2 (KS2 domain) in 6-deoxyerythronolide B synthase (DEBS) tolerates a broad range of variations in substrate structure, but it strongly discriminates against some others. CONCLUSIONS: Defining the boundaries of substrate recognition within PKS domains is crucial to the rationally engineered biosynthesis of novel polyketide products, many of which could be prepared only with great difficulty, if at all, by direct chemical synthesis or semi-synthesis. Our results suggest that the KS2 domain of DEBS1 has a relatively relaxed specificity that can be exploited for the design and synthesis of medicinally important polyketide products.  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