首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   7329篇
  免费   1471篇
  国内免费   890篇
化学   5227篇
晶体学   98篇
力学   297篇
综合类   99篇
数学   769篇
物理学   3200篇
  2024年   29篇
  2023年   181篇
  2022年   281篇
  2021年   270篇
  2020年   297篇
  2019年   336篇
  2018年   318篇
  2017年   229篇
  2016年   380篇
  2015年   398篇
  2014年   419篇
  2013年   546篇
  2012年   697篇
  2011年   713篇
  2010年   472篇
  2009年   480篇
  2008年   505篇
  2007年   416篇
  2006年   367篇
  2005年   289篇
  2004年   252篇
  2003年   187篇
  2002年   218篇
  2001年   162篇
  2000年   166篇
  1999年   133篇
  1998年   110篇
  1997年   116篇
  1996年   100篇
  1995年   90篇
  1994年   70篇
  1993年   82篇
  1992年   52篇
  1991年   70篇
  1990年   49篇
  1989年   42篇
  1988年   22篇
  1987年   24篇
  1986年   27篇
  1985年   20篇
  1984年   16篇
  1983年   16篇
  1982年   10篇
  1981年   5篇
  1980年   3篇
  1979年   7篇
  1978年   3篇
  1977年   4篇
  1976年   5篇
  1936年   1篇
排序方式: 共有9690条查询结果,搜索用时 500 毫秒
1.
Journal of Thermal Analysis and Calorimetry - Based on innovative design, a liquid–vapor separation plate condenser with excellent heat transfer performance is invented. It takes less time to...  相似文献   
2.
The implementation of covalent adaptable networks (CANs) in general resin system is becoming attractive. In this work, we propose a simple post-curing strategy based on the core-shell structured acrylate latex for the achievement on both the improved general performance and the CANs characteristics in latex films. The building to the CANs was relied on the introduction of 4,4′-diaminophenyl disulfide as the curing agent, which cured the acetoacetoxy decorated shell polymer through the ketoamine reaction. The metathesis reaction of aromatic disulfides in the crosslinking segments enabled the thermally induced dynamic behavior of the network as revealed in the stress relaxation tests by comparison with other diamine crosslinking agents without the incorporation of disulfide. The synergism of the dynamic crosslinking of the shell polymer and static crosslinking in the core polymer contributed to the improved mechanical strength (15 MPa, strain% = 250%) and the suppressed water adsorption (~1% in 24 h of soaking) of the latex film, which exhibited above 90% of recovery in both strength and strain from a cut-off film damage within 1 h at 80°C. Moreover, the cured latex film could be recycled, and 75% of the mechanical performance was regained after three fragmentation-hot-pressing cycles. These, in addition with the feasible and environmental friendly characteristics, suggest a sustainable paradigm toward the smart thermosetting latex polymers.  相似文献   
3.
4.
Set-Valued and Variational Analysis - We aim to establish Karush-Kuhn-Tucker multiplier rules involving higher-order complementarity slackness under Hölder metric subregularity. These rules...  相似文献   
5.
Strategies for the formation of amide bonds, that is, one of the most basic and important transformations in organic synthesis, have so far focused predominantly on dehydration reactions. Herein, we report and demonstrate the practical utility of a novel decarboxylative amidation of α-ketoacids by using inexpensive tert-butyl hydroperoxide (TBHP), which is characterized by high yields, a broad substrate scope, mild reaction conditions, and a unique chemoselectivity. These features enable the synthesis of peptides from amino acid derived α-ketoacids under preservation of the stereochemical information.  相似文献   
6.
Eucommia ulmoides Oliv. (E. ulmoides) is a valuable and nourishing medicinal herb in China that has been used in the treatment of hypertension. Given the fact that most traditional Chinese medicine is mainly used to treat disease, investigating the pharmacokinetics of traditional Chinese medicines in the pathological state is more useful than that in the normal state. However, the differences in the absorption kinetics of active ingredients of E. ulmoides extract between pathological and physiological conditions have not been reported. Therefore, in this study, the rat intestinal in situ circulatory perfusion model was used to investigate the differences in absorption kinetics of seven active ingredients of E. ulmoides extract in normal and spontaneously hypertensive rats, namely, genipinic acid, protocatechuic acid, neochlorogenic acid, chlorogenic acid, cryptochlorogenic acid, (+)-pinoresinol di-O-β-D -glucopyranoside and (+)-pinoresinol 4′-O-β-D -glucopyranoside. Our results indicate that the pathological state of spontaneous hypertension may change the absorption of active components of E. ulmoides extracts, and these findings may provide a reference for improving the rational use of E. ulmoides in the clinic.  相似文献   
7.
8.
A 1.5-μm eye-safe, 3-D scanning, and compact Mie LIght Detection and Ranging (LIDAR) is presented. The transmitter of the LIDAR is based on a KTA optical parameter oscillator (OPO) resonator. For detecting return signals, an InGaAs APD is used. The all solid-state OPO laser transmitter has the feature of small volume and lightweight, which allows a 165-lb compact eye-safe scanning LIDAR to be constructed. A system simulation using our own model was conducted to direct the system development. A method to solve the problem with small active area APD detectors was developed and described. The preliminary field-test measurement results indicated that the LIDAR has the capability to detect aerosols and clouds in lower atmospheres up to three dimensions.  相似文献   
9.
一类非线性Schr(o)dinger方程的守恒差分法与Fourier谱方法   总被引:1,自引:0,他引:1  
龚玉飞  许传炬 《数学研究》2006,39(4):360-369
考察了一类带导数项的非线性Schrodinger方程的周期边值问题,提出了一种守恒的差分格式,在空间方向上采用Fourier谱方法,证明了格式的稳定性和收敛性.数值试验得到了与理论分析一致的结果.  相似文献   
10.
本文对一类重要的函数方程建立解稳定性定理,提出微商配置解,证明了收敛性.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号