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991.
兼具有强阴离子性与疏水缔合性的丙烯酰胺三元共聚物   总被引:3,自引:0,他引:3  
在微乳液介质中实施了丙烯酰胺 (AM)、苯乙烯 (St)、2 丙烯酰胺基 2 甲基丙磺酸钠 (NaAMPS)的共聚合 ,制备了既含有强阴离子性基团 (—SO3Na)又含有疏水基团 (St)的丙烯酰胺三元共聚物AM NaAMPS St;通过红外光谱法、紫外分光光度法及元素分析法对共聚物的结构及组成进行了表征 ;稀释外推粘度法测定了共聚物的特性粘数 ;测定了共聚物纯水溶液及盐水溶液的表观粘度 ;荧光探针法考察了三元共聚物的疏水缔合性以及离子基团对疏水缔合性的影响规律 .实验结果表明 ,在聚丙烯酰胺 (PAM )分子主链上同时引入强阴离子性基团与疏水基团后 ,阴离子的电粘效应与疏水基团的疏水缔合作用相互协同 ,会使共聚物水溶液的黏度显著提高 ;盐溶液对疏水缔合作用的增强效应与强阴离子基团对盐的较大容忍度相互结合 ,会使共聚物水溶液的抗盐性能明显得以提高 ;大分子链上的强阴离子基团磺酸根的存在 ,在一定程度上会削弱疏水基团之间的疏水缔合作用 ,即对疏水基团的疏水缔合行为会产生一定的负性影响 .  相似文献   
992.
Pt(IV)与I-形成[PtI6]2-,[PtI6]2-和盐酸西替利嗪(CTRZ)通过静电引力作用形成疏水性的(PtI6—CTRZ)缔合物分子.由于(PtI6-CTRZ)缔合物分子间存在较强的分子间作用力和疏水作用力而生成紫红色(CTRZ—PtI6)n缔合微粒,在310、400、610nm处产生3个共振散射峰;在350~740nm波长范围的吸光度值均增大.在选定条件下,CTRZ浓度在0~10μg/mL范围内与A580nm成正比,摩尔吸光系数ε580nm为1.30×104L/(mol·cm).实验结果表明,(CTRZ—PtI6)n缔合微粒的形成是导致同步散射信号增强的根本原因,而纳米纳米微粒的颜色是共振散射所致.  相似文献   
993.
As we look so different, our genomic sequences vary enormously. The differences in our genome, genetic variations, have played very significant roles in medical research and have contributed to improvement of medical managements in the last 2–3 decades. Genetic variations include germline variations, somatic mutations, and diversities in receptor genes of rearranged immune cells, T cells and B cells. Germline variants are in some cases causative of genetic diseases, are associated with the risk of various diseases, and also affect drug efficacies or adverse events. Some somatic mutations are causative of tumor development. Recent DNA sequencing technologies allow us to perform single-cell analysis or detailed repertoire analysis of B and T cells. It is critically important to investigate temporal changes in immune environment in various anatomical regions in the next one to two decades. In this review article, we would like to introduce the roles of genetic variations in medical fields in the past, at present and in the future.  相似文献   
994.
Empirical Euclidean likelihood for general estimating equations for association dependent processes is investigated. The strong consistency and asymptotic normality of the blockwise maximum empirical Euclidean likelihood estimator are presented. We show that it is more efficient than estimator without blocking. The blockwise empirical Euclidean log-likelihood ratio asymptotically follows a chi-square distribution.  相似文献   
995.
This paper focuses on the computation issue of portfolio optimization with scenario-based CVaR. According to the semismoothness of the studied models, a smoothing technology is considered, and a smoothing SQP algorithm then is presented. The global convergence of the algorithm is established. Numerical examples arising from the allocation of generation assets in power markets are done. The computation efficiency between the proposed method and the linear programming (LP) method is compared. Numerical results show that the performance of the new approach is very good. The remarkable characteristic of the new method is threefold. First, the dimension of smoothing models for portfolio optimization with scenario-based CVaR is low and is independent of the number of samples. Second, the smoothing models retain the convexity of original portfolio optimization problems. Third, the complicated smoothing model that maximizes the profit under the CVaR constraint can be reduced to an ordinary optimization model equivalently. All of these show the advantage of the new method to improve the computation efficiency for solving portfolio optimization problems with CVaR measure.  相似文献   
996.
In productivity analysis an important issue is to detect how external (environmental) factors, exogenous to the production process and not under the control of the producer, might influence the production process and the resulting efficiency of the firms. Most of the traditional approaches proposed in the literature have serious drawbacks. An alternative approach is to describe the production process as being conditioned by a given value of the environmental variables (Cazals, C., Florens, J.P., Simar, L., 2002. Nonparametric Frontier estimation: A robust approach. Journal of Econometrics 106, 1–25; Daraio, C., Simar, L., 2005. Introducing environmental variables in nonparametric Frontier models: A probabilistic approach. Journal of Productivity Analysis 24(1), 93–121). This defines conditional efficiency measures where the production set in the input ×× output space may depend on the value of the external variables. The statistical properties of nonparametric estimators of these conditional measures are now established (Jeong, S.O., Park, B.U., Simar, L., 2008. Nonparametric conditional efficiency measures: Asymptotic properties. Annals of Operations Research doi: 10.1007/s10479-008-0359-5). These involve the estimation of a nonstandard conditional distribution function which requires the specification of a smoothing parameter (a bandwidth). So far, only the asymptotic optimal order of this bandwidth has been established. This is of little interest for the practitioner. In this paper we fill this gap and we propose a data-driven technique for selecting this parameter in practice. The approach, based on a Least Squares Cross Validation procedure (LSCV), provides an optimal bandwidth that minimizes an appropriate (weighted) integrated Squared Error (ISE). The method is carefully described and exemplified with some simulated data with univariate and multivariate environmental factors. An application on real data (performances of Mutual Funds) illustrates how this new optimal method of bandwidth selection works in practice.  相似文献   
997.
设S(n,q)是偶特征有限域F_q上n×n对称矩阵所成的集合.令R_i={(X,Y)|X,Y∈S(n,q),rank(Y-X)=2i-1,2i},0≤i≤[(n+1)/2]采用矩阵方法,证明了Sym(n,q)={s(n,q),{R_i}_(0≤i≤)[(n+1)/2]}是[(n+1)/2]个结合类的P—多项式对称结合方案,而Sym(n,q)的结合关系的图Γ~((1))是正则的,并且它同构于交错矩阵结合方案.此外,又给出Sym(n,q)的自同构形式.  相似文献   
998.
We consider optimization problems for minimizing conditional value-at-risk (CVaR) from a computational point of view, with an emphasis on financial applications. As a general solution approach, we suggest to reformulate these CVaR optimization problems as two-stage recourse problems of stochastic programming. Specializing the L-shaped method leads to a new algorithm for minimizing conditional value-at-risk. We implemented the algorithm as the solver CVaRMin. For illustrating the performance of this algorithm, we present some comparative computational results with two kinds of test problems. Firstly, we consider portfolio optimization problems with 5 random variables. Such problems involving conditional value at risk play an important role in financial risk management. Therefore, besides testing the performance of the proposed algorithm, we also present computational results of interest in finance. Secondly, with the explicit aim of testing algorithm performance, we also present comparative computational results with randomly generated test problems involving 50 random variables. In all our tests, the experimental solver, based on the new approach, outperformed by at least one order of magnitude all general-purpose solvers, with an accuracy of solution being in the same range as that with the LP solvers. János Mayer: Financial support by the national center of competence in research "Financial Valuation and Risk Management" is gratefully acknowledged. The national centers in research are managed by the Swiss National Science Foundation on behalf of the federal authorities.  相似文献   
999.
訾言勤  丁言斌  张东辉  王晴 《分析化学》2005,33(12):1757-1760
在弱酸性介质中,小分子天青A与生物大分子核糖核酸(RNA)强烈相互作用,导致分子构象的变化,引起分子光谱最大吸收波长和吸收值的变化。应用光谱法研究了反应体系酸度、天青A用量、反应时间等影响反应速度的因素,确定了最佳实验条件,建立了测定核糖核酸的新方法。线性范围为0.2~7.2mg/L。相关系数为0.9986。直接测定样品中核糖核酸获得满意结果;对作用机理进行了初步探讨,静电缔合作用使天青A分子与凝聚在RNA分子链上的反离子交换,然后,以协同方式与RNA分子发生键合,使天青A的π-电子叠合程度降低,颜色变浅,吸收值降低,最大吸收波长紫移。  相似文献   
1000.
磷酸氯喹与过氧化氢缔合催化作用的极谱研究   总被引:1,自引:1,他引:0  
在2.0×10-2mol/LNH3·H2O NH4Cl(pH9.5)-1.0×10-2mol/LH2O2支持电解质中,磷酸氯喹于-1.87V(vs.SCE)产生一缔合平行催化波。该波的二阶导数峰峰电流与磷酸氯喹浓度在2.0×10-9~1.0×10-5mol/L范围内呈线性关系(r=0.9986,n=10)。可用于片剂中磷酸氯喹的测定。H2O2有双重作用:(1)H2O2作为配位体与磷酸氯喹形成缔合物,使峰电位Ep负移;(2)H2O2作为氧化剂氧化磷酸氯喹经单电子单质子还原生成的中间体自由基,产生极谱催化波。  相似文献   
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