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   37395篇
  免费   1471篇
  国内免费   71篇
化学   25662篇
晶体学   270篇
力学   716篇
数学   5429篇
物理学   6860篇
  2023年   285篇
  2022年   215篇
  2021年   532篇
  2020年   655篇
  2019年   618篇
  2018年   783篇
  2017年   717篇
  2016年   1443篇
  2015年   1152篇
  2014年   1246篇
  2013年   2392篇
  2012年   2677篇
  2011年   2899篇
  2010年   1686篇
  2009年   1435篇
  2008年   2396篇
  2007年   2342篇
  2006年   2045篇
  2005年   1872篇
  2004年   1537篇
  2003年   1187篇
  2002年   1077篇
  2001年   766篇
  2000年   663篇
  1999年   504篇
  1998年   367篇
  1997年   294篇
  1996年   414篇
  1995年   290篇
  1994年   277篇
  1993年   317篇
  1992年   277篇
  1991年   209篇
  1990年   180篇
  1989年   168篇
  1988年   163篇
  1987年   156篇
  1986年   159篇
  1985年   220篇
  1984年   201篇
  1983年   154篇
  1982年   157篇
  1981年   124篇
  1980年   99篇
  1979年   109篇
  1978年   109篇
  1977年   102篇
  1976年   95篇
  1975年   85篇
  1973年   93篇
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
1.
Reactivity studies of the GeII→B complex L(Cl)Ge⋅BH3 ( 1 ; L=2-Et2NCH2-4,6-tBu2-C6H2) were performed to determine the effect on the GeII→B donation. N-coordinated compounds L(OtBu)Ge⋅BH3 ( 2 ) and [LGe⋅BH3]2 ( 3 ) were prepared. The possible tuning of the GeII→B interaction was proved experimentally, yielding compounds 1-PPh2-8-(LGe)-C10H6 ( 4 ) and L(Cl)Ge⋅GaCl3 ( 5 ) without a GeII→B interaction. In 5 , an unprecedented GeII→Ga coordination was revealed. The experimental results were complemented by a theoretical study focusing on the bonding in 1 − 5 . The different strength of the GeII→E (E=B, Ga) donation was evaluated by using energy decomposition analysis. The basicity of different L(X)Ge groups through proton affinity is also assessed.  相似文献   
2.
Meccanica - In this work we study, from the numerical point of view, a one-dimensional thermoelastic problem where the thermal law is of type III. Quasi-static microvoids are also assumed within...  相似文献   
3.
Numerical Algorithms - In this work, we propose a fractional extension of the one-dimensional nonlinear vibration problem on an elastic string. The fractional problem is governed by a hyperbolic...  相似文献   
4.
Central European Journal of Operations Research - Sustainability practice within supply chains remains in an early development phase. Enterprises still need tools that support the integration of...  相似文献   
5.
Kumar  Sanjay  Jiwari  Ram  Mittal  R. C.  Awrejcewicz  Jan 《Nonlinear dynamics》2021,104(1):661-682
Nonlinear Dynamics - In this article, the authors simulate and study dark and bright soliton solutions of 1D and 2D regularized long wave (RLW) models. The RLW model occurred in various fields such...  相似文献   
6.
7.
CRANAD-2 is a fluorogenic curcumin derivative used for near-infrared detection and imaging in vivo of amyloid aggregates, which are involved in neurodegenerative diseases. We explore the performance of CRANAD-2 in two super-resolution imaging techniques, namely stimulated emission depletion (STED) and single-molecule localization microscopy (SMLM), with markedly different fluorophore requirements. By conveniently adapting the concentration of CRANAD-2, which transiently binds to amyloid fibrils, we show that it performs well in both techniques, achieving a resolution in the range of 45–55 nm. Correlation of SMLM with atomic force microscopy (AFM) validates the resolution of fine features in the reconstructed super-resolved image. The good performance and versatility of CRANAD-2 provides a powerful tool for near-infrared nanoscopic imaging of amyloids in vitro and in vivo.  相似文献   
8.
9.
Riociguat is novel antihypertensive drug for treatment of pulmonary hypertension. As such, it is still being tested in many clinical and pharmacokinetic trials. Existing methods that determine serum riociguat and desmethylriociguat (DMR) are based solely on liquid chromatography with mass spectrometry. Therefore, we present a novel capillary electrophoresis with mass spectrometry method (CE-MS) for their determination in human serum as alternative method for ongoing trials. Complete resolution of both analytes was achieved by means of pH optimization of ammonium formate background electrolytes that are fully compatible with ESI/MS detection. Simple liquid-liquid extraction was used as sample pretreatment. The calibration dependence of the method was linear (in the range of 10–1000 ng/mL), with adequate accuracy (90.1–114.9%) and precision (13.4%). LOD and LOQ were arbitrarily set at 10 ng/mL for both analytes. Clinical applicability was validated using serum samples from patients treated with riociguat in pharmacokinetic study and the results corresponded with reference HPLC-MS/MS values. Capillary electrophoresis proved to be sensitive and selective tool for the analysis of riociguat and DMR.  相似文献   
10.
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