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961.
M. A. Campanero A. M. Zamarreño M. Simón M. C. Dios J. R. Azanza 《Chromatographia》1997,46(7-8):374-380
Summary A simple and rapid liquid chromatographic method has been developed for the determination of therapeutic levels of piperacillin
(I) and ceftazidime (II) in human plasma. Plasma and p-propionamidophenol (internal standard) were precipitated with methanol
(I) or 20% trichloroacetic acid (II). The supernatant was analysed on a 5 μm Spherisorb ODS C18 column with acetonitrile-0.05 M phosphate buffer pH 3.8 as mobile phase and ultraviolet detection at 254 nm. The calibration
graph was linear from 10 to 250 μg mL−1, for (I), and from 5 to 200 μg mL−1 for (II). Intra and inter-day CV did no exceed 2.29% for (I), and were 10.76–11.13%–2.00–5.62 for (II) at concentrations
of 10 μg mL−1 and 250 μg mL−1. 相似文献
962.
A three-rigid-links model is constructed for a gymnast performing a kip-up maneuver on a horizontal bar. Equations of motion with constrained, voluntary torques at hip and shoulder joints give a well-posed optimal control problem when boundary conditions and a performance criterion for the maneuver are specified. An approximate numerical solution for the minimum-time performance of this nonlinear process is obtained by the method of steepest descent. Results of the computations are compared with experimental results. Difficulties of solving human motion problems by existing numerical methods are pointed out.Notation element 1
arm system
- element 2
head-neck-torso system
- element 3
leg system
-
angle between element 1 and vertical
-
angle between elements 1 and 2
-
angle between elements 2 and 3
-
O
1
hinge axis between elements 1 and 2
-
O
2
hinge axis between elements 2 and 3
-
O
3
hinge axis representing fist-horizontal-bar system
-
T
1
torque between elements 1 and 2
-
T
2
torque between elements 2 and 3
-
l
1
distance betweenO
3 andO
1
-
l
2
distance betweenO
1 andO
2
-
I
i
moment of inertia of elementi about its CG about an axis perpendicular to the plane of motion,i = 1,2,3
-
I
r
moment of inertia of the horizontal bar about its longitudinal axis
-
m
i
mass of elementi, i=1,2,3
-
r
1
distance between O3 and CG of element 1
-
r
2
distance between O1 and CG of element 2
-
r
3
distance between O1 and CG of element 3
-
g
acceleration due to gravity
This research was partially supported by the National Science Foundation through Grants Nos. GK-4944 and GK-37024x.Appreciation of Dr. Tom Bullock for discussion on numerical optimization techniques and Mr. Tom Boone for his services as an experimental test subject is gratefully acknowledged. 相似文献
963.
G. Sohár E. Pallagi P. Szabó-Révész K. Tóth 《Journal of Thermal Analysis and Calorimetry》2007,89(3):853-856
Osteoarthritis, although classically conceived of as a degenerative consequence of aging, is a disease with an increasingly
well-characterized molecular pathophysiology. Pathologic changes in cartilage composition and molecular organization, as well
as elevated water content, alter the exquisite balance of biomechanical properties. Much of what is known about changes in
the extracellular matrix in osteoarthritis comes from animal models.
Previously, thermogravimetric methods have not been used for compositional thermoanalytical study of normal and degenerative
human hyaline cartilage. For this reason the research group established a sufficient new thermogravimetric protocol, which
proved water content elevation contributing to disease progression. 相似文献
964.
在模拟生理条件下,应用荧光光谱和表面增强拉曼光谱法对对-香豆酸(p-CA)与人血清白蛋白(HSA)的结合机理进行研究。结果表明,p-CA对HSA的荧光猝灭机制为静态猝灭,并伴有非辐射能量转移。荧光光谱显示,在298,304,310 K下,p-CA与HSA的结合常数(KA)分别为3.41×10~4,2.09×10~4,1.38×10~4L/mol,结合位点数(n)近似为1。表面增强拉曼光谱研究揭示,p-CA的酚基与HSA有效结合。标记竞争实验指出,p-CA在HSA上的结合位点主要在SiteⅠ。反应过程热力学参数表明,二者间的作用主要为静电引力,且根据Frster能量转移理论求得p-CA与HSA间的距离为5.11 nm。同步荧光光谱显示,p-CA的结合没有导致HSA构象发生明显变化。 相似文献
965.
Radiometric surveys using airborne, vehicular mounted or backpack detector systems are increasingly used to identify and evaluate complex distributions of radioactivity in the environment. The signals detected depend on the energy and spatial distribution of radioactive sources, the material properties of the environment and the specific properties of the detector systems employed. Materials in close vicinity to the detector such as housings, and intermediate materials may have a critical impact on detection efficiency, and must therefore be taken into account in calibration. This study evaluates the effect of shielding by the body of the operator in backpack surveys. Controlled experiments using point sources and absorbers, chosen to represent the form and composition of human tissue, were conducted, and coupled to an analytical radiation transport model to estimate attenuation factors for mapping of 137Cs. In this way generic factors to correct for this effect using portable spectrometers have been determined. The results compare well with observations at sampled calibration sites in Fukushima and the Solway area in Scotland. Reductions of the 137Cs full-energy peak intensity between 20% and 30% may be expected depending on operator stature and the offset position of backpack systems. Similar effects may be present for other radiometric systems carried by a human operator. 相似文献
966.
The present paper deals with the issue of bank capital adequacy and risk management within a stochastic dynamic setting. In particular, an explicit risk aggregation and capital expression is provided regarding the portfolio choice and capital requirements special context. Such a framework leads to a nonlinear stochastic optimal control problem whose solution may be determined by means of dynamic programming algorithm. The pertaining analysis relies heavily on the stochastic dynamic modeling of such balance sheet items as securities, loans, and regulatory capital with stochastic interest rates. In this respect, the special Kalman filter approach is used for the purpose of estimating the model parameters. The reached findings reveal well that the Tunisian bank, subject of study, generally exceeds the minimum requirements and is adequately capitalized to maintain the appropriate capital amount level commensurate with the aggregate risk. Besides, empirical evidence on the regulations' impact on driving bank capitalization and risk‐taking behavior has also been highlighted. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
967.
Dr. Petra Galer Dr. Baifan Wang Dr. Primož Šket Prof. Dr. Janez Plavec 《Angewandte Chemie (International ed. in English)》2016,55(6):1993-1997
A four‐repeat human telomere DNA sequence without the 3′‐end guanine, d[TAGGG(TTAGGG)2TTAGG] (htel1‐ΔG23) has been found to adopt two distinct two G‐quartet antiparallel basket‐type G‐quadruplexes, TD and KDH+ in presence of KCl. NMR, CD, and UV spectroscopy have demonstrated that topology of KDH+ form is distinctive with unique protonated T18?A20+?G5 base triple and other capping structural elements that provide novel insight into structural polymorphism and heterogeneity of G‐quadruplexes in general. Specific stacking interactions amongst two G‐quartets flanking base triples and base pairs in TD and KDH+ forms are reflected in 10 K higher thermal stability of KDH+. Populations of TD and KDH+ forms are controlled by pH. The (de)protonation of A20 is the key for pH driven structural transformation of htel1‐ΔG23. Reversibility offers possibilities for its utilization as a conformational switch within different compartments of living cell enabling specific ligand and protein interactions. 相似文献
968.
Molecular Simulations of Human and Mouse Aβ1–16 at Different pH Values: Structural Characteristics toward Understanding Cu2+‐Coordinated Amyloid Beta Spheres 下载免费PDF全文
As the main sequence responsible for metal ion coordination in the amyloid beta (Aβ) peptide, Aβ1–16 plays a key role in the understanding of the aggregation of Aβ induced by Cu2+ ions. There is no consensus on the nature of the coordination sphere of the Cu2+–Aβ complex so far due to the amorphous conformation of the Aβ1–16 peptide itself and the pH dependence of Cu2+–Aβ coordination. The simulation reported here reveals that human Aβ1–16 monomer has a U‐shape morphology, which is preserved at any pH. This morphology accommodates Cu2+ ions with several binding sites and is also the basis for establishing a center‐distance statistical method (CDSM). Based on this CDSM, specific histidine residues for a Cu2+‐coordinated sphere are identified and the corresponding accurate pH range is established, indicating that the CDSM can be used as a reference to predict the potential coordination sites of metal ions in other amorphous peptides. By contrast, mouse Aβ1–16 monomer has a more open and random morphology than human Aβ1–16 due to the differences of three sequence positions. These mutations not only reduce the number of binding sites required by a stable Cu2+‐binding sphere but also diminish the capacity to generate salt bridges compared to the human peptide. These observations offer insights into the roles of three residues that differ in the mouse Aβ1–16 and perhaps into the reasons mice seldom develop Alzheimer's disease. 相似文献
969.
Flávio Lopes Alves Roberto C. Sallai Bruno R. Salu Antonio Miranda Maria Luiza V. Oliva 《Natural product research》2016,30(23):2712-2715
Araucaria angustifolia seeds are characterised by a relatively high content of starch and protein. This study aimed to verify the presence of α-amylase inhibitors in the seeds and to characterise a trypsin inhibitor found in the embryo tissues. Inhibitor purification was carried out by the saline extraction of proteins, acetone precipitation and affinity chromatography. Two protein bands of molecular weight estimated by SDS-PAGE at about 35 kDa were further examined by high-performance liquid chromatography coupled to a mass spectrometer and were shown to be 36.955 Da (AaTI-1) and 35.450 Da (AaTI-2). The sequence of the N-terminal region shows that AaTI-1 and AaTI-2 are structurally similar to plant inhibitors of the serpin family. A mixture of AaTI-1 and AaTI-2, identified as AaTI, shows selectivity for the inhibition of trypsin (Kiapp 85 nM) and plasmin (Kiapp 7.0 μM), but it does not interfere with the chymotrypsin, human plasma kallikrein, porcine kallikrein or other coagulation enzymes activity. 相似文献
970.
Urbano França Hiroki Sayama Colin Mcswiggen Roozbeh Daneshvar Yaneer Bar‐Yam 《Complexity》2016,21(6):280-287
Describing the dynamics of a city is a crucial step to both understanding the human activity in urban environments and to planning and designing cities accordingly. Here, we describe the collective dynamics of New York City (NYC) and surrounding areas as seen through the lens of Twitter usage. In particular, we observe and quantify the patterns that emerge naturally from the hourly activities in different areas of NYC, and discuss how they can be used to understand the urban areas. Using a dataset that includes more than 6 million geolocated Twitter messages we construct a movie of the geographic density of tweets. We observe the diurnal “heartbeat” of the NYC area. The largest scale dynamics are the waking and sleeping cycle and commuting from residential communities to office areas in Manhattan. Hourly dynamics reflect the interplay of commuting, work and leisure, including whether people are preoccupied with other activities or actively using Twitter. Differences between weekday and weekend dynamics point to changes in when people wake and sleep, and engage in social activities. We show that by measuring the average distances to a central location one can quantify the weekly differences and the shift in behavior during weekends. We also identify locations and times of high Twitter activity that occur because of specific activities. These include early morning high levels of traffic as people arrive and wait at air transportation hubs, and on Sunday at the Meadowlands Sports Complex and Statue of Liberty. We analyze the role of particular individuals where they have large impacts on overall Twitter activity. Our analysis points to the opportunity to develop insight into both geographic social dynamics and attention through social media analysis. © 2015 Wiley Periodicals, Inc. Complexity 21: 280–287, 2016 相似文献