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排序方式: 共有385条查询结果,搜索用时 15 毫秒
81.
Prabhakar P. Singh 《Solid State Communications》2003,125(6):323-326
We present a comparison of electron-phonon interaction in NbB2 and MgB2, calculated using full-potential, density-functional-based methods in P6/mmm crystal structure. Our results, described in terms of (i) electronic structure, (ii) phonon density of states F(ω), (iii) Eliashberg function α2F(ω), and (iv) the solutions of the isotropic Eliashberg gap equation, clearly show significant differences in the electron-phonon interaction in NbB2 and MgB2. We find that the average electron-phonon coupling constant λ is equal to 0.59 for MgB2 and 0.43 for NbB2, leading to superconducting transition temperatures Tc at around 22 K for MgB2 and 3 K for NbB2. 相似文献
82.
The first total synthesis of (−)-diospongin B has been achieved starting from benzaldehyde using chiral allylation, a base catalyzed conjugate addition of an α,β-unsaturated ester and an intramolecular oxy-Michael reaction as the key steps in 16% overall yield. 相似文献
83.
Thiophene and its substituted derivatives are very important class of heterocyclic compounds which shows interesting applications in the field of medicinal chemistry. It has made an indispensable anchor for medicinal chemists to produce combinatorial library and carry out exhaustive efforts in the search of lead molecules. It has been reported to possess a wide range of therapeutic properties with diverse applications in medicinal chemistry and material science, attracting great interest in industry as well as academia. It has been proven to be effectual drugs in present respective disease scenario. They are remarkably effective compounds both with respect to their biological and physiological functions such as anti-inflammatory, anti-psychotic, anti-arrhythmic, anti-anxiety, anti-fungal, antioxidant, estrogen receptor modulating, anti-mitotic, anti-microbial, kinases inhibiting and anti-cancer. Thus the synthesis and characterization of novel thiophene moieties with wider therapeutic activity is a topic of interest for the medicinal chemist to synthesize and investigate new structural prototypes with more effective pharmacological activity. However, several commercially available drugs such as Tipepidine, Tiquizium Bromides, Timepidium Bromide, Dorzolamide, Tioconazole, Citizolam, Sertaconazole Nitrate and Benocyclidine also contain thiophene nucleus. Therefore, it seems to be a requirement to collect recent information in order to understand the current status of the thiophene nucleus in medicinal chemistry research. 相似文献
84.
Tiwari Rakesh N. Singh Prabhakar Pandey Shivam Anand Ritika Singh Dinesh Kumar Kanaujia Binod Kumar 《Analog Integrated Circuits and Signal Processing》2021,109(1):103-113
Analog Integrated Circuits and Signal Processing - A compact dual band 2?×?2 multiple-input-multiple-output (MIMO) antenna with dimension... 相似文献
85.
Manu Gupta Venkateswaran Rajagopalan Erik P. Pioro B. V. V. S. N. Prabhakar Rao 《Signal, Image and Video Processing》2017,11(7):1337-1345
This work aims to identify non-invasive quantitative parameters from three-dimensional brain magnetic resonance images in order: (1) to classify brain tumor (glioma) as low grade (LG) or high grade (HG) and (2) to analyze effect of tumor on brain gray matter (GM) and white matter (WM). In proposed model features were extracted from segmented tumor region based on its volume and shape for distinguishing the tumor grade. Statistical analysis revealed good correlation between segmented tumor volume and tumor grade. Various morphological parameters extracted from segmented tumor region were also significantly different for LG and HG cases (\(p<0.05\)). Also, for brain tumor patients a considerable variation in normalized GM (%GM) volume was obtained compared to normalized WM (%WM) volume for LG and HG cases. We also found that, relative to controls, there was higher effect on %GM and %WM volumes for HG glioma patients as compared to LG glioma patients. The experimental results show that proposed feature set achieves LG/HG classification with high accuracy using support vector machines classifier. 相似文献
86.
Kimura M Lehmann K Gopalan-Kriczky P Lotlikar PD 《Experimental & molecular medicine》2004,36(4):351-357
Effects of diets on hepatic aflatoxin B1 (AFB1)- DNA binding and AFB1-induced glutathione S- transferase placental (GST-P) form positive hepatic foci have been examined in young male Fischer rats. Animals were fed either AIN-76A or Purina Chow (PC) diet for 1 wk before AFB1- DNA binding studies in vivo and in vitro. Animals were injected i.p. with AFB1 (1 mug/kg body wt) and 3 days later were given either AIN-76A or PC diet with or without 0.1% phenobarbital (PB) in their drinking water. All animals were sacrificed 10 wks after AFB1 dosing for analysis of AFB1-induced GST-P positive hepatic foci by immunochemistry. Two h after i.p. injection of AFB1, hepatic AFB1-DNA binding in AIN-76A fed rats was twice as much as those in PC fed animals without affecting GSH levels. There was no significant effect of diet on either cytochrome P-450 content, GSH levels or microsomal cytochrome P-450 mediated AFB1-DNA binding to exogenous DNA. There was a 40% increase in cytosolic GSH S-transferase activity with 1-chloro-2,4-dinitrobenzene as a substrate in PC fed animals compared to those given AIN- 76A diet. The number and area of AFB1-induced GST-P positive hepatic foci were twice and fivefold as much in AIN-76A fed compared to those in PC fed rats. The number of AFB1-induced GST-P positive foci was increased 5-10 fold in the presence of PB in both groups. In summary, the present data indicate that feeding of PC diet compared to AIN-76A diet inhibits the initiation phase whereas AIN-76A stimulates the promotion phase of AFB1 hepatocarcinogenesis in rats by inhibiting AFB1-DNA binding and increasing AFB1-induced hepatic foci respectively. 相似文献
87.
Pierce ME Harris GD Islam Q Radesca LA Storace L Waltermire RE Wat E Jadhav PK Emmett GC 《The Journal of organic chemistry》1996,61(2):444-450
DMP 323, a potent HIV-1 protease inhibitor, has been synthesized by an efficient stereoselective process, amenable to large scale preparations. The core C(2) symmetric diol was synthesized by a stereoselective pinacol coupling of CBZ protected D-phenylalanine. Judicious selection of protecting groups allowed cyclic urea formation under mild conditions, enhanced the ease of bis-alkylation, and led to intermediates which were easily purified without chromatography. Additionally, a one-pot, high yield process was developed to prepare the alkylating agent, 4-[(triphenylmethoxy)methyl]benzyl chloride from 1,4-benzenedimethanol. 相似文献
88.
Penicillin acylase ofE. coli NCIM 2400 has been purified to homogeneity using a combination of hydrophobic interaction chromatography and DEAE-cellulose
treatment. A variety of substituted matrices were synthesized using D- or DL-phenylglycine, norleucine, ampicillin, or amoxycillin
as ligands, all of which retained penicillin acylase at high concentrations of ammonium sulfate or sodium sulfate. The enzyme
could be eluted nonbiospecifically by buffer of lower ionic strength with over 95% recovery of the activity. Ammonium chloride,
ammonium nitrate, sodium chloride, sodium nitrate, and potassium chloride were ineffective in either adsorption or elution
of the enzyme on these columns. Further purification of this partially pure enzyme with DEAE-cellulose at pH 7.0–7.2 yielded
an enzyme preparation of very high purity according to electrophoretic and ultracentrifugal analyses, its specific activity
being as high as 37 U/mg protein. The purifiedf enzyme has a molecular weight of 67,000 a sedimentation coefficient of 4.0S,
and resolves into two forms upon isoelectric focusing. Overall recoveries ranged between 75 and 85%. Ease of operation, high
recoveries, high purity of the enzyme and prolonged reuse of the conjugates make the process economically feasible and possibly
of great commercial importance. 相似文献
89.
Y Anjaneyulu R Prabhakar Rao R Y Swamy A Eknath K Narasimha Rao 《Journal of Chemical Sciences》1982,91(2):157-163
A series of mixed ligand complexes of Hg(II) with the general formula Hg (OX) (SA) (where OX: 8-hydroxyquinoline, SA: salicylic,
5-chloro-, 3,5-dibromo, 3,5-diiodo, 3,5-dinitro, acetyl thiosalicylic acids) are isolated in pure state and characterised
by elemental analysis and infrared data. The low molar conductance of the complexes in dimethylformamide indicates non-electrolyte
nature. The antimicrobial activity of these complexes against various bacteria and fungi is studied which indicates that in
several cases, the mixed ligand complexes possess fairly highly antimicrobial activity than the binary mercury-oxinate. The
lipophilic tendency of these complexes and its influence on the antimicrobial activity is critically examined. A probable
mechanism for the toxic action of these complexes against various organisms is discussed. 相似文献
90.
A new flexible approach to hexahydropyrrolo[2,3-b]indole system via the [3,3]-sigmatropic rearrangement of 1-(2′-methoxycarbonyl-N-methylvinylamino)skatole, culminating in the synthesis of (±)-desoxyeseroline, is described. 相似文献