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111.
Qian Yanlong Li Guisheng Chen Weichun Li Bihua Jin Xianglin 《Transition Metal Chemistry》1990,15(6):478-482
Summary A new class of differentially ring-substituted titanocene dichlorides of the type CpCpTiCl2 has been prepared by reacting CpM (M=Li, K; Cp=RC5H4) with CpTiCl3 (Cp=MeOCH2CH2C5H4). The crystal structure of Cp(PhCEt2C5H4)TiCl2, the first example, has been determined by x-ray diffraction and refined to a final R factor of 0.0532 for 2304 reflections. The crystal belongs to the monoclinic space group C
2h
5
–P21/c with unit cell parameters:a 10.205(6),b 13.003(5),c 17.591(9) Å, 101.91(4)°, V=2284 Å3, Z=4 and Dc=1.32 g/cm–3. Replacement of one neomenthyl in bis(neomenthyl-cyclopentadienyl)titanium dichloride by one MeOCH2CH2 — raises the e.e. value from 5.8% to 11.2% in the catalytic asymmetric hydrogenation of 2-phenyl-1-butene. 相似文献
112.
113.
毛细管电泳法快速测定保健食品中免疫球蛋白G 总被引:10,自引:0,他引:10
建立了毛细管电泳法快速测定保健食品中免疫球蛋白G(IgG)含量的方法,成功测定了不同剂型(片剂、粉剂及胶囊)牛初乳保健品中IgG的含量。以37 cm×50μm(i.d.)未涂敷熔融石英毛细管为色谱分离柱,50 mmol/L四硼酸钾 65 g/L聚乙二醇20 000(1 mol/L氢氧化铯调pH 10.0)为运行缓冲液,于214 nm波长处检测。详细研究了影响实际样品中IgG分离及准确定量的关键因素,如添加剂的种类、浓度;运行及样品缓冲液的浓度及pH等。采用峰面积外标法定量。方法的精密度为2.1%(n=7);检出限为6.25 mg/L(S/N=3);线性范围为50~2000 mg/L;400 mg/L IgG迁移时间的相对标准偏差(RSD)为0.14%;峰面积的RSD为2.9%(n=7)。6 m in内即可实现保健食品中IgG的分离与测定,结果与产品标示值基本吻合。 相似文献
114.
We derive exact properties of the inhomogeneous electron gas in the asymptotic classically forbidden region at a metal–vacuum interface within the framework of local effective potential energy theory. We derive a new expression for the asymptotic structure of the Kohn–Sham density functional theory (KS‐DFT) exchange‐correlation potential energy vxc(r) in terms of the irreducible electron self‐energy. We also derive the exact asymptotic structure of the orbitals, density, the Dirac density matrix, the kinetic energy density, and KS exchange energy density. We further obtain the exact expression for the Fermi hole and demonstrate its structure in this asymptotic limit. The exchange‐correlation potential energy is derived to be vxc(z → ∞) = ?αKS,xc/z, and its exchange and correlation components to be vx(z → ∞) = ?αKS,x/z and vc(z → ∞) = ?αKS,c/z, respectively. The analytical expressions for the coefficients αKS,xc and αKS,x show them to be dependent on the bulk‐metal Wigner–Seitz radius and the barrier height at the surface. The coefficient αKS,c = 1/4 is determined in the plasmon‐pole approximation and is independent of these metal parameters. Thus, the asymptotic structure of vxc(z) in the vacuum region is image‐potential‐like but not the commonly accepted one of ?1/4z. Furthermore, this structure depends on the properties of the metal. Additionally, an analysis of these results via quantal density functional theory (Q‐DFT) shows that both the Pauli Wx(z → ∞) and lowest‐order correlation‐kinetic W(z → ∞) components of the exchange potential energy vx(z → ∞), and the Coulomb Wc(z → ∞) and higher‐order correlation‐kinetic components of the correlation potential energy vc(z → ∞), all contribute terms of O(1/z) to the structure. Hence correlations attributable to the Pauli exclusion principle, Coulomb repulsion, and correlation‐kinetic effects all contribute to the asymptotic structure of the effective potential energy at a metal surface. The relevance of the results derived to the theory of image states and to KS‐DFT is also discussed. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 相似文献
115.
磺酰脲类除草剂的三维药效团模型 总被引:3,自引:0,他引:3
磺酰脲类除草剂是七十年代末期[1,2]开发的一类超高效除草剂,杀草谱广,用量极低.它通过抑制植物体内乙酰乳酸合成酶(ALS,acetolactatesynthase)的活性[3],破坏支链氨基酸缬氨酸、亮氨酸和异亮氨酸的合成,造成杂草的死亡.本文从三维角度出发,利用先进的三维分子设计软件APEX(ActivityPredictionExpertSystem)-3D[4],建立破酸豚类除草剂药效团模型(biophoremodel),辅助设计、筛选活性化合物;再由药效团构造出模拟ALS酶活性位点(activesites)的空间结构,以该模拟结构为基点,以期设计出全新结构的ALS酶抑制剂的… 相似文献
116.
A three-dimensional pharmacophore model was developed from a series of inhibitors of Aurora A kinase to discover new potent anti-cancer agents using the HypoGen module in the Catalyst software. The pharmacophore model was developed based on the structure of 20 currently available inhibitors, which were carefully selected from the literature. The best hypothesis (Hypo 1) was defined by four features: one hydrogen-bond donor and three hy- drophobic points, with the best correlation coefficient of 0.909, the lowest rms deviation of 1.563, and the highest cost difference of 99.075. The Hypo 1 was then validated by a test set consisting of 24 compounds and by a cross-validation of 95% confidence level through randomizing the data using the CatScramble program, which suggested that a predictive pharmacophore model had been successfully obtained. 相似文献
117.
研究了波长、温度及表面处理对n-InP光脉冲暂态行为的影响。结果表明,波长对时间常数无影响;随着温度升高,峰值下降,衰减变快。讨论了表面处理的影响,并对实验结果作了必要的解释。 相似文献
118.
The hydrothermal reaction of YbCl(3) small middle dot6H(2)O with 1,2,4,5-benzenetetracarboxylic dianhydride resulted in [[Yb((b)btec)(1/4)((d)btec)(3/6)(H(2)O)(2)](4).6H(2)O](n)() (1) (H(4)btec = 1,2,4,5-benzenetetracarboxylic acid), and the solvothermal reaction of Er(NO(3))(3) small middle dot6H(2)O or TbCl(3).6H(2)O with 1,2,4,5-benzenetetracarboxylic dianhydride in H(2)O/acetic acid gave rise to [[Er(2)((c)btec)(2/4)((e)btec)(2/4)((f)btec)(2/4)(H(2)O)(4)].4H(2)O](n)() (2) and [[Tb(H(2)btec)(2/4)((f)btec)(3/6)(H(2)O)].2H(2)O](n)() (3), respectively. Complex 1 crystallizes in monoclinic space group C2/m with a = 20.8119(5) A, b = 17.6174(1) A, c = 5.7252(2) A, beta = 92.324(1) degrees, and Z = 1. 1 possesses a three-dimensional framework consisting of eight-coordinate ytterbium centers and two kinds of channels along the c axis. Complex 2 crystallizes in triclinic space group P with a = 9.6739(5) A, b = 11.0039(5) A, c = 11.5523 A, alpha = 104.8330(10) degrees, beta = 91.0000(10) degrees, gamma = 114.2570(10) degrees, and Z = 2. 2 has a three-dimensional framework comprising both eight- and nine-coordinate erbium centers and channels along the a axis. Complex 3 crystallizes in monoclinic space group P2(1)/n with a = 10.7246(12) A, b = 7.1693(9) A, c = 17.158(2) A, beta = 97.109(2) degrees, and Z = 4. 3 shows a three-dimensional framework containing nine-coordinate terbium centers and channels along the b axis. Uncoordinated water molecules occupy the channels in the three complexes. TGA and XRPD were determined for the three complexes, and the results illustrate that the framework of 1 is retained upon removal of uncoordinated and coordinated water molecules. 相似文献
119.
本文测定了不同电位及不同光强下, n-InP在Fe~(3+)/Fe~(2+)溶液中的复阻抗图, 从一个等放电路用计算机对结果进行了拟合, 并对拟合结果进行了讨论。 相似文献
120.
阳、阴、非离子表面活性剂胶束对酯碱性水解的影响 总被引:13,自引:0,他引:13
应用紫外分光光度法和热动力学方法研究了芳香酸酯和正脂肪酸酯在表面活性剂DTAB、TTAB、CTAB、SDS、Brij35、TritonX-100胶束中的碱性水解反应。阳、阴、非离子表面活性剂胶束对酯的碱性水解均有禁阻作用。讨论了胶束对酯碱性水解禁阻作用的原因。 相似文献