全文获取类型
收费全文 | 8037篇 |
免费 | 794篇 |
国内免费 | 537篇 |
专业分类
化学 | 5638篇 |
晶体学 | 96篇 |
力学 | 420篇 |
综合类 | 46篇 |
数学 | 697篇 |
物理学 | 2471篇 |
出版年
2024年 | 20篇 |
2023年 | 123篇 |
2022年 | 227篇 |
2021年 | 313篇 |
2020年 | 284篇 |
2019年 | 273篇 |
2018年 | 208篇 |
2017年 | 215篇 |
2016年 | 318篇 |
2015年 | 289篇 |
2014年 | 373篇 |
2013年 | 566篇 |
2012年 | 704篇 |
2011年 | 703篇 |
2010年 | 491篇 |
2009年 | 437篇 |
2008年 | 546篇 |
2007年 | 466篇 |
2006年 | 435篇 |
2005年 | 372篇 |
2004年 | 319篇 |
2003年 | 263篇 |
2002年 | 260篇 |
2001年 | 166篇 |
2000年 | 126篇 |
1999年 | 121篇 |
1998年 | 104篇 |
1997年 | 83篇 |
1996年 | 85篇 |
1995年 | 74篇 |
1994年 | 48篇 |
1993年 | 54篇 |
1992年 | 50篇 |
1991年 | 53篇 |
1990年 | 27篇 |
1989年 | 24篇 |
1988年 | 23篇 |
1987年 | 20篇 |
1986年 | 15篇 |
1985年 | 16篇 |
1984年 | 13篇 |
1983年 | 10篇 |
1982年 | 11篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1977年 | 3篇 |
1973年 | 4篇 |
1971年 | 6篇 |
1970年 | 6篇 |
排序方式: 共有9368条查询结果,搜索用时 15 毫秒
91.
92.
We are concerned with the non-stationary Stokes system with non-homogeneous external force and non-zero initial data in \({\mathbb {R}}^n_+ \times (0,T)\). We obtain new estimates of solutions including pressure in terms of mixed anisotropic Sobolev spaces. As an application, some anisotropic Sobolev estimates are presented for weak solutions of the Navier–Stokes equations in a half-space in dimension three. 相似文献
93.
Ming-Hsuan Kang Wen-Ching Winnie Li Chian-Jen Wang 《Israel Journal of Mathematics》2018,228(1):79-117
In this paper, we study relations between Langlands L-functions and zeta functions of geodesic walks and galleries for finite quotients of the apartments of G =PGL3 and PGSp4 over a nonarchimedean local field with q elements in its residue field. They give rise to an identity (Theorem 5.3) which can be regarded as a generalization of Ihara’s theorem for finite quotients of the Bruhat–Tits trees. This identity is shown to agree with the q = 1 version of the analogous identities for finite quotients of the building of G established in [KL14, KLW10, FLW13], verifying the philosophy of the field with one element by Tits. A new identity for finite quotients of the building of PGSp4 involving the standard L-function (Theorem 6.3), complementing the one in [FLW13] which involves the spin L-function, is also obtained. 相似文献
94.
We consider stationary motion of degenerate power-law fluids in three dimension. We obtain a local regularity estimates of weak solutions, restricting ourselves to the shear-thickening case. 相似文献
95.
Target tracking is one of the most important issues in computer vision and has been applied in many fields of science, engineering and industry. Because of the occlusion during tracking, typical approaches with single classifier learn much of occluding background information which results in the decrease of tracking performance, and eventually lead to the failure of the tracking algorithm. This paper presents a new correlative classifiers approach to address the above problem. Our idea is to derive a group of correlative classifiers based on sample set method. Then we propose strategy to establish the classifiers and to query the suitable classifiers for the next frame tracking. In order to deal with nonlinear problem, particle filter is adopted and integrated with sample set method. For choosing the target from candidate particles, we define a similarity measurement between particles and sample set. The proposed sample set method includes the following steps. First, we cropped positive samples set around the target and negative samples set far away from the target. Second, we extracted average Haar-like feature from these samples and calculate their statistical characteristic which represents the target model. Third, we define the similarity measurement based on the statistical characteristic of these two sets to judge the similarity between candidate particles and target model. Finally, we choose the largest similarity score particle as the target in the new frame. A number of experiments show the robustness and efficiency of the proposed approach when compared with other state-of-the-art trackers. 相似文献
96.
ST Lo YT Wang G Bohra E Comfort TY Lin MG Kang G Strasser JP Bird CF Huang LH Lin JC Chen CT Liang 《J Phys Condens Matter》2012,24(40):405601
Magneto-transport measurements are performed on two-dimensional GaAs electron systems to probe the quantum Hall (QH) effect at low magnetic fields. Oscillations following the Shubnikov-de Haas (SdH) formula are observed in the transition from the insulator to QH liquid when the observed almost temperature-independent Hall slope indicates insignificant interaction correction. Our study shows that the existence of SdH oscillations in such a transition can be understood based on the non-interacting model. 相似文献
97.
将二维人工脑模型推广到三维,并给出了一个实际应用算例,还将二、三维模型的计算结果进行了对比,发现三维模型的计算效果明显优于二维模型。 相似文献
98.
The preparation of Ni–SiC coatings using magnetic field-assisted jet electrodeposition under various plating settings is described in this study. A RBF-BP composite neural network with 4 × 4 × 4 × 7 × 10 × 1 was used to predict the corrosion resistance of Ni–SiC coatings prepared by employing different plating parameters. The results show that the fitting degree between the expected value and the actual value of the RBF-BP composite neural network is 0.97497. Moreover, the hybrid neural network can accurately predict the corrosion resistance of Ni–SiC coatings prepared under different process parameters. The corrosion weight loss of the coating is the lowest at the current density of 4 A/dm2, a jet rate of 3 m/s, a SiC particle concentration of 8 g/L, and at a magnetic field intensity of 0.8 T, demonstrating its corrosion resistance under these conditions. According to the coating characterization analysis, the coating's grain size was significantly refined, and the surface was smoother with a high amount of uniformly sized SiC nanoparticles. 相似文献
99.
Jin-San Yoon Min-Chul Chang Mal-Nam Kim Eun-Jung Kang Chulhee Kim In-Joo Chin 《Journal of Polymer Science.Polymer Physics》1996,34(15):2543-2551
Poly[(R)-3-hydroxybutyrate] (PHB) was blended with an aliphatic copolyester, which was synthesized by the esterification of adipic acid, ethylene glycol, and lactic acid. The blend showed a single Tg, which varied systematically but convexly upwards with the composition. The growth rate of PHB spherulites, the crystallization temperature, and the equilibrium melting temperature of the blend were decreased as the amount of the copolyester was increased. Therefore, the blend system was determined to be compatible. However, the degree of crystallinity, and the enthalpies of crystallization and fusion of PHB in the blend remained almost constant, regardless of the compositional change, although the crystallization rate was decreased upon blending. No chemical change such as transesterification was observed as a result of the blending, yet there was a slight change in the crystalline morphology of PHB. The rate of fungal degradation was lowered with an increase in the copolyester content of the blend. © 1996 John Wiley & Sons, Inc. 相似文献
100.
This study examined the pharmacokinetic disposition, oral absorption and hepatic extraction of itraconazole and its active metabolite, hydroxyitraconazole, in rats. After i.v. injection, serum itraconazole concentrations decreased biexponentially, with an average terminal elimination half-life, volume of distribution and systemic clearance of 4.9 h, 6.0 l/kg and 14.2 ml/min/kg, respectively. When given orally, its absorption was low, with a mean absolute bioavailability of 16.6%. The metabolite to parent drug area under the curve (AUC) ratio was higher after oral administration compared with i.v. injection (mean ratio, 2.7 vs. 0.9). The hepatic drug extraction ratio determined after femoral and portal vein administration averaged 18.5%. When hydroxyitraconazole was injected i.v., the elimination half-life, volume of distribution and systemic clearance of itraconazole averaged 10.0 h, 2.4 l/kg and 3.4 ml/min/kg, respectively. The fraction of the systemically available itraconazole that was metabolized to hydroxyitraconazole was 21.0% and 76.0% after i.v. and oral administration, respectively. In summary, this study is the first reporting the hepatic extraction of itraconazole and the i.v. disposition characteristics of hydroxyitraconazole in rats. Itraconazole is a drug with a low hepatic extraction ratio and its systemic clearance appears to be largely accounted for by hepatic metabolism. 相似文献