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101.
102.
J.A. Aguilar-Saavedra J. Carvalho N. Castro A. Onofre F. Veloso 《The European Physical Journal C - Particles and Fields》2007,50(3):519-533
We investigate several quantities, defined in the decays of top quark pairs, which can be used to explore non-standard Wtb interactions. Two new angular asymmetries are introduced in the leptonic decay of top (anti)quarks. Both are very sensitive
to anomalous Wtb couplings, and their measurement allows for a precise determination of the W helicity fractions. We also examine other angular
and energy asymmetries, the W helicity fractions and their ratios, as well as spin correlation asymmetries, analysing their
dependence on anomalous Wtb couplings and identifing the quantities which are most sensitive to them. It is explicitly shown that spin correlation asymmetries
are less sensitive to new interactions in the decay of the top quark; therefore, when combined with the measurement of other
observables, they can be used to determine the tt̄ spin correlation even in the presence of anomalous Wtb couplings. We finally discuss some asymmetries which can be used to test CP violation in tt̄ production and complex phases
in the effective Wtb vertex. 相似文献
103.
Carvalho Andrade Carolina M. M. Aguiar Wilson Bucker Antranikian Garo 《Applied biochemistry and biotechnology》2001,91(1-9):655-669
Xylanases (EC3.2.1.8) catalyze the hydrolysis of xylan, the major constituent of hemicellulose. The use of these enzymes could
greatly improve the overall economics of processing lignocellulosic materials for the generation of liquid fuels and chemicals.
The hyperthermophilic archaeon Pyrodictium abyssi, which was originally isolated from marine hot abyssal sites, grows optimally at 97°C and is a prospective source of highly
thermostable xylanase. Its endoxylanase was shown to be highly thermostable (over 100 m in at 105°C) and active even at 110°C.
The growth of the deep-sea archaeon P. abyssi was investigated using different culture techniques. Among the carbohydrates used, beech wood xylan, birch wood glucuronoxylan
and the arabinoxylan from oats pelt appeared to be good inducers for endoxylanase and β-xylosidase production. The highest
production of arabinofuranosidase, however, was detected in the cell extracts after growth on xylose and pyruvate, indicating
that the intermediate of the tricarboxylic acid cycle acted as a nonrepressing carbon source for the production of thi enzyme.
Electron microscopic studies did not show a significant difference in the cell surface (e.g., xylanosomes) when P. abyssi cells were grown on different carbohydrates. The main kinetic parameters of the organism have been determined. The cell yield
was shown to be very low owing to incomplete substrate utilization, but a very high maximal specific growth rate was determined
(μmax=0.0195) at 90°C and pH 6.0. We also give information on the problems that arise during the fermentation of this hyperthermophilic
archaeon at elevated temperatures. 相似文献
104.
M. I. Yoshida V. R. Silva P. C. C. Pinto S. S. Sant’Anna M. C. Silva C. F. Carvalho 《Journal of Thermal Analysis and Calorimetry》2012,109(3):1429-1433
In the aluminum industries, there are several steps involved in processing since the extraction of bauxite to obtain the final product (Al). During the development of these, various steps generated wastes. One of them, from the electrostatic filter of the calcination step of the Bayer process is a very fine black powder, rich in alumina (Al2O3) that does not meet industry specifications, and it is discarded in the industry yard. Alumina is a noble material and has high commercial value. This black powder has great prospects for recovery, recycling, and future applications. Therefore, it is important to perform characterization of tailings and to do that we have used XRD, SEM, EDS, FTIR, Raman, and thermal analysis. 相似文献
105.
S. Pessanha M.L. Carvalho M. Manso A. Guilherme A.F. Marques C.A. Perez 《Spectrochimica Acta Part B: Atomic Spectroscopy》2009,64(8):805
The pigment vermilion (HgS) was used to color the fore edge, tail and head of books. Dissemination and quantification of Hg present in the ink used to color books from XVIII and XIX centuries are reported. Mercury is a very toxic element for the human body, therefore it is extremely important to know whether Hg tends to disseminate throughout the paper or stays confined to the borders of the books with less danger for readers. Synchrotron X-ray microprobe was used to evaluate Hg dissemination from the border to the centre of the paper sheet. The diffusion pattern of Hg was compared with the results obtained by a portable X-ray fluorescence spectrometer and mean quantitative calculations were obtained by a stationary X-ray fluorescence system with triaxial geometry. The results showed high concentrations of Hg in the external regions, but no diffusion was observed for the inner parts of the paper. 相似文献
106.
To obtain full cooperation from respondents, statistical offices must guarantee that confidential data will not be disclosed when their reports are published. For tabular data, cell suppression is one of the preferred techniques to control statistical disclosure. When suppressing only confidential values does not guarantee the desired data protection, it is also necessary to suppress the values in some non-confidential cells. The problem of finding an optimal set of complementary suppressions—the cell suppression problem (CSP)—is NP-hard. We present a three-phase algorithm for the CSP based on a binary relaxation derived from row and column protection conditions. To enforce violated single cell conditions, integer cuts are added to the CSP relaxation. The numerical results obtained in 1410 instances with up to more than 250?000 cells, which were generated to reproduce two classes of real-world data, indicate that the algorithm is quite effective for both classes of instances and that it outperforms state-of-the-art algorithms for one of them. 相似文献
107.
A. Guilherme S. Pessanha M.L. Carvalho J.M.F. dos Santos J. Coroado 《Spectrochimica Acta Part B: Atomic Spectroscopy》2010
Several glazed ceramic pieces, originally produced in Coimbra (Portugal), were submitted to elemental analysis, having as premise the pigment manufacture production recognition. Although having been produced in Coimbra, their location changed as time passed due to historical reasons. A recent exhibition in Coimbra brought together a great number of these pieces and in situ micro Energy Dispersive X-ray Fluorescence (µ-EDXRF) analyses were performed in order to achieve some chemical and physical data on the manufacture of faiences in Coimbra. 相似文献
108.
do Amaral M. G. Aragão de Carvalho C. Pol M. E. Shellard R. C. 《Zeitschrift fur Physik C Particles and Fields》1986,32(4):609-614
Zeitschrift für Physik C Particles and Fields - We study the finite temperature behaviour of λφ4 theory in two and three dimensions, using Monte Carlo simulations. We renormalize the... 相似文献
109.
Two dynamical deformation theories are presented – one for surface homeomorphisms, called pruning, and another for graph endomorphisms, called kneading– both giving conditions under which all of the dynamics in an open set can be destroyed, while leaving the dynamics unchanged
elsewhere. The theories are related to each other and to Thurston’s classification of surface homeomorphisms up to isotopy.
Received February 20, 2000 / final version received February 26, 2001?Published online May 29, 2001 相似文献
110.
C Alves J M Valério de Carvalho 《The Journal of the Operational Research Society》2008,59(11):1520-1531
Apart from trim loss minimization, there are many other issues concerning cutting processes that arise in real production systems. One of these is related to the number of stacks that need to be opened near the cutting machines. Many researchers have worked in the last years on cutting stock problems with additional constraints on the number of open stacks. In this paper, we address a related problem: the Ordered Cutting Stock Problem (OCSP). In this case, a stack is opened for every new client's order, and it is closed only when all the items of that order are cut. The OSCP has been introduced recently in the literature. Our aim is to provide further insight into this problem. This paper describes three new integer programming formulations for solving it, and an exact algorithm based on column generation, branch-and-bound and cutting planes. We report on computational experiments on a set of random instances. The results show that good lower bounds can be computed quickly, and that optimal solutions can be found in a reasonable amount of time. 相似文献