全文获取类型
收费全文 | 154631篇 |
免费 | 28377篇 |
国内免费 | 17039篇 |
专业分类
化学 | 123098篇 |
晶体学 | 2025篇 |
力学 | 7467篇 |
综合类 | 1094篇 |
数学 | 17333篇 |
物理学 | 49030篇 |
出版年
2024年 | 279篇 |
2023年 | 2300篇 |
2022年 | 3675篇 |
2021年 | 4414篇 |
2020年 | 5763篇 |
2019年 | 6759篇 |
2018年 | 5062篇 |
2017年 | 4592篇 |
2016年 | 8578篇 |
2015年 | 8723篇 |
2014年 | 10007篇 |
2013年 | 12699篇 |
2012年 | 13719篇 |
2011年 | 13589篇 |
2010年 | 10812篇 |
2009年 | 10518篇 |
2008年 | 10592篇 |
2007年 | 9138篇 |
2006年 | 8513篇 |
2005年 | 7471篇 |
2004年 | 5993篇 |
2003年 | 4950篇 |
2002年 | 5480篇 |
2001年 | 4191篇 |
2000年 | 3758篇 |
1999年 | 2871篇 |
1998年 | 2122篇 |
1997年 | 1817篇 |
1996年 | 1782篇 |
1995年 | 1574篇 |
1994年 | 1425篇 |
1993年 | 1167篇 |
1992年 | 1015篇 |
1991年 | 912篇 |
1990年 | 722篇 |
1989年 | 583篇 |
1988年 | 427篇 |
1987年 | 380篇 |
1986年 | 366篇 |
1985年 | 311篇 |
1984年 | 212篇 |
1983年 | 175篇 |
1982年 | 142篇 |
1981年 | 100篇 |
1980年 | 74篇 |
1979年 | 40篇 |
1978年 | 34篇 |
1977年 | 28篇 |
1976年 | 29篇 |
1957年 | 31篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
991.
控温相变免疫分析测定雌酮 总被引:4,自引:0,他引:4
通过热引发聚合与氧化还原引发聚合,合成水凝胶,作为雌酮全抗原(E1— BSA)载体;以异硫氰基灾光素标记雌酮的单克隆抗体(McAb)作为示踪剂,建立了控温相变竞争免疫分析测定雌酮(EI)的方法并应用于分析血清样品。实验表明:以热引发聚合合成的水凝胶为载体的荧光免疫分析方法具有更高的灵敏度,它的线性范围为10-700μg/L,检出限为1μg/L(n=10,3倍空白)。经水凝胶性质的比较(包括LCST、非特异性吸附、抗原与抗体反应时间及固定化抗原活性),证明了热引发聚合的水凝胶较氧化还原引发聚合的水凝胶更适合于作为免疫分析的载体。 相似文献
992.
993.
Xia Yin Weiguang Zhang Qijiao Zhang Jun Fan Chian Sing Lai Edward R. T. Tiekink 《应用有机金属化学》2004,18(3):139-140
The centrosymmetric structure of {Cd[S2CN(CH2Ph)2]2}2 features both bridging and chelating dithiocarbamate ligands so that a square pyramidal S5 coordination geometry results. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
994.
Ginette Ratovo Jean‐Pierre Souchard Pascale Urizzi Yvon Coulais Franoise Nepveu Etienne Hollande 《应用有机金属化学》2004,18(1):1-8
Pancreatic cancer has an extremely poor prognosis, due, in part, to lack of methods for early diagnosis. The present study was designed to evaluate the potential of labeling low‐density lipoprotein (LDL) with a radionuclide using a lipid chelating agent, bis(stearylamide) of diethylenetriaminepentaacetic acid (L), to detect pancreatic tumors by gamma‐scintigraphy. Previous studies indicated that the difficulty of visualization of pancreatic tumors was due to their poor vascularization. This study compares the ability of two radiotracers, 111In–L–LDL and 153Gd–L–LDL to target highly vascularized rat pancreatic tumors (AR4‐2J) implanted in nude mice. Biodistribution studies showed that the tumor uptake of 111In–L–LDL and 153Gd–L–LDL tracers was twofold and fivefold higher respectively than with the controls (111In citrate and 153Gd citrate respectively). These tracers would thus be suitable for scintigraphic imaging. We show here that LDL could be employed as a delivery system for tracers such as 111In or 153Gd when these two radionuclides are complexed by a lipid‐chelating anchor, and that 111In–L–LDL and 153Gd–L–LDL enabled better visualization of the pancreatic tumor tissues, with a better result with 153Gd–L–LDL. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
995.
Sparse approximate inverse (SAI) techniques have recently emerged as a new class of parallel preconditioning techniques for
solving large sparse linear systems on high performance computers. The choice of the sparsity pattern of the SAI matrix is
probably the most important step in constructing an SAI preconditioner. Both dynamic and static sparsity pattern selection
approaches have been proposed by researchers. Through a few numerical experiments, we conduct a comparable study on the properties
and performance of the SAI preconditioners using the different sparsity patterns for solving some sparse linear systems.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
996.
直线运动是自然界中运动形式最简单的一种运动.一般物理教材都要讲解几种常见的直线运动:匀速直线运动、变速直线运动、匀变速直线运动、自由落体运动等.学生从中学习了它们的定义及所遵守的规律,简单了解了位移、速度、加速度几个物理量在这几种运动中所起的作用.笔者在长期一线教学过程中发现如果仅仅罗列式讲解而不作深入细致的引导,学生容易陷入机械记忆,孤立学习的误区,不利于发现几种运动之间稍深层次的关系以及对知识的系统化的掌握.在章节复习时若对速度、加速度在几种直线运动中的作用稍加点拨,情况会大不一样. 相似文献
997.
998.
利用Fenton试剂(Fe2+/H2O2)处理含有除草剂2,4-二氯苯氧乙酸(2,4-D)的模拟废水.结果显示,Fenton试剂对2,4-D有很好的去除效果.Fe2+和H2O2的摩尔比为1:20,在H2O2为1/2Qth理论投加量的条件下处理30mtn,2,4-D去除率达到80.0%.考察了Fe2+投加量、Fe2+和H2O2投加比、2,4-D初始浓度和pH等因素对2,4-D降解的影响.通过GC-MS和HPLC检测到反应中间产物有2,4-二氯苯酚、邻氯苯酚和对氯苯酚,氯离子在这些中间产物上释放.通过离子色谱检测到进一步氧化的产物还有小分子酸,如乙醇酸、乙醛酸、顺丁烯二酸,提出了Fenton降解2,4 -D的可能途径. 相似文献
999.
Influence of Turbid Medium Parameters on Back Scattered Intensity and Pulsewidth of Picosecond Pulse
In this paper, we simulate a practical in vivo technique in which is produced influence of turbid medium parameters on backscattered intensity and pulsewidth of picosecond for turbid tissue surface of a semiinfinite medium by a small narrow linewidth laser beams. It is shown that the interaction of the ultra short pulse and the turbid tissue is very used as researching the optical parameters of the turbid medium. 相似文献
1000.
P. Budrugeac J. M. Criado F. J. Gotor J. Malek L. A. Prez‐Maqueda E. Segal 《国际化学动力学杂志》2004,36(6):309-315
The isoconversional method suggested by Friedman and the invariant kinetic parameters method (IKP) were used in order to examine the kinetics of the nonisothermal crystallization of (GeS2)0.3(Sb2S3)0.7. The objective of the paper is to show the usefulness of the IKP method both for determining the activation parameters as well as the model of the investigated process. It was shown that the kinetic triplet [(E, A, f(α), where E is the activation energy, A is the preexponential factor, and f(α) is the differential function of conversion], which results through the application of the IKP method, depends on the set of kinetic models considered. For different sets of kinetic models, proportional values of f(α) are obtained. A criterion for the selection of this set, the use of which lead to the true kinetic triplet corresponding to the analyzed process (E = 163.2 kJ mol?1; A = 2.47 × 1012 min?1 and the Avrami‐Erofeev model, Am, for m = 2.5–2.6 was suggested. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 309–315, 2004 相似文献