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   4632篇
  免费   12篇
  国内免费   1篇
电工技术   15篇
综合类   1篇
化学工业   215篇
金属工艺   31篇
机械仪表   20篇
建筑科学   45篇
矿业工程   1篇
能源动力   53篇
轻工业   105篇
水利工程   10篇
石油天然气   1篇
无线电   147篇
一般工业技术   204篇
冶金工业   3646篇
原子能技术   21篇
自动化技术   130篇
  2022年   8篇
  2021年   14篇
  2020年   7篇
  2018年   5篇
  2017年   7篇
  2016年   11篇
  2015年   6篇
  2014年   17篇
  2013年   56篇
  2012年   32篇
  2011年   31篇
  2010年   31篇
  2009年   48篇
  2008年   53篇
  2007年   51篇
  2006年   56篇
  2005年   47篇
  2004年   39篇
  2003年   42篇
  2002年   36篇
  2001年   31篇
  2000年   47篇
  1999年   148篇
  1998年   1073篇
  1997年   648篇
  1996年   410篇
  1995年   238篇
  1994年   197篇
  1993年   212篇
  1992年   39篇
  1991年   67篇
  1990年   59篇
  1989年   65篇
  1988年   78篇
  1987年   76篇
  1986年   50篇
  1985年   48篇
  1984年   24篇
  1983年   28篇
  1982年   31篇
  1981年   30篇
  1980年   43篇
  1979年   21篇
  1978年   30篇
  1977年   94篇
  1976年   195篇
  1975年   9篇
  1974年   14篇
  1972年   9篇
  1971年   8篇
排序方式: 共有4645条查询结果,搜索用时 31 毫秒
91.
92.
We found that the total watery extracts obtained from roots of various plants such as Symphytum officinale, Phytolacca americana etc, precipitate human glycoproteins, agglutinate sheep red blood cells (SRBC) and stimulate lymphocyte adherence to nylon fibers. Five out of seven extracts precipitated human gammaglobulins and one of seven obviously agglutinate SRBC. If these cells were pretreated with rabbit antibodies against SRBC, all extracts agglutinated the cells at various degrees of intensity, the most active being Phytolacca americana. The adherence of mouse but not human lymphocytes to nylon fibers was stimulated by extracts of Symphytum officinale and Phytolacca americana. This process was neither stimulated nor inhibited by Mannose (Man), Galactose (Gal), Glucose (Glc), N-acethyl Galactose (GalNAc) and N-acethyl Glucose (Glc-NAc). These biological effects of the plant extracts could be the expression of a lectin-like ability to bind various sugars other than those mentioned. The results suggest the possibility of using different extracts as means to point out the presence in serum or at the cellular level of some carbohydrates influencing the cellular adhesion, phenomenon which plays an important role in the functions of hematopoietic cells.  相似文献   
93.
94.
Multiple trials using antiarrhythmic drugs, pharmacologic therapy, and implantable cardioverter defibrillators have been performed in an attempt to improve survival in patients: (1) postmyocardial infarction; (2) with congestive heart failure, with and without nonsustained ventricular tachycardia; and (3) with sustained ventricular tachycardia and those who have survived an out-of-hospital cardiac arrest. This article reviews some of the key findings and limitations of completed and ongoing trials. We also make recommendations for the current treatment of such patients based on the results of these trials.  相似文献   
95.
Germline mutations in the presenilin 1 (PS1) gene apparently account for the majority of early-onset, familial Alzheimer's disease (AD). Using a mutation-screening strategy (denaturing gradient gel electrophoresis; DGGE), we analyzed a large family with early onset AD and seizures. The patients in this family showed a novel missense mutation in exon 5 of the PS1 gene (A to T change in codon 120, altering glutamine to aspartic acid). This novel mutation is located within the second hydrophilic domain of the molecule, a region not particularly involved in previously described germline mutations, and is of unknown biological significance. These results also demonstrate that DGGE can be used effectively to screen for mutations within this gene.  相似文献   
96.
97.
98.
Immunocytochemistry and retrograde labeling were used to define the thalamic projections of calbindin- and parvalbumin-containing cells in superficial layers of the rat's superior colliculus (SC). Quantitative analysis revealed that 90.8 +/- 2.2% (mean +/- standard deviation) of the calbindin-immunoreactive neurons in the stratum griseum superficiale (SGS) projected to the dorsal lateral geniculate nucleus (LGNd) and that 91.3 +/- 4.3% of calbindin-immunoreactive neurons in the stratum opticum (SO) projected to the lateral posterior nucleus (LP). In contrast, only 17.3 +/- 2.5% of parvalbumin-immunoreactive neurons in the SGS were found to project to the LGNd and 16.5 +/- 3.1% of the parvalbumin-immunoreactive SO cells were retrogradely labeled after LP injections. Few of the parvalbumin-immunoreactive neurons in either the SGS (7.2 +/- 2.5%) or the SO (9.2 +/- 2.5%) were GABA positive. The retrograde-labeling results suggest that parvalbumin-immunoreactive neurons in the rat's SO and SGS may either be primarily interneurons or have descending projections, while calbindin-containing cells are primarily thalamic projection neurons. These results are consistent with data from other rodents, but almost exactly the opposite of data that have been reported for the cat for these same populations of SC projection neurons. Such interspecies differences raise questions regarding the functional importance of expressing one calcium-binding protein versus another in a specific neuronal population.  相似文献   
99.
We studied the postnatal development of the release of acetylcholine (ACh) and of presynaptic, release-inhibiting muscarinic autoreceptors in the rat hippocampus. To this end, hippocampal slices (350 microns thick) from rats of various postnatal ages (postnatal day 3 [P3] to P16) were preincubated with [3H]choline and stimulated twice (S1, S2: 360 pulses, 2 ms, 3 Hz, 60 mA) during superfusion with physiological buffer containing hemicholinium-3 (10 microM). In parallel, the activities of hemicholinium-sensitive high-affinity choline uptake (HACU, in synaptosomes) and of choline acetyltransferase (ChAT, in crude homogenates) were determined as markers for the cholinergic ingrowth. In hippocampal slices preincubated with [3H]choline, the electrically evoked overflow of 3H at S1 increased from 0.11 (P3) to 0.81% of tissue 3H (P16), the latter value being still much lower than that of hippocampal slices from adult rats (2.89% of tissue 3H). Already at P3 the evoked overflow of 3H was Ca(2+)-dependent and sensitive to tetrodotoxin, indicating an action potential-evoked exocytotic mechanism of ACh release. The muscarinic agonist oxotremorine (1 microM) significantly inhibited the evoked ACh release in hippocampal slices with increasing effectivity from P4 to P16; no significant effect was detectable at P3. The ACh esterase inhibitor physostigmine and the muscarinic antagonist atropine (1 microM, each) exhibited significant inhibitory and facilitatory effects, respectively, only at P15-16. The specific activities of both hippocampal HACU (pmoles/mg protein/min) and ChAT (nmoles/mg protein/min) continuously increased from P3 to P16. It is concluded (1) that cholinergic nerve terminals arriving at the hippocampal formation during postnatal ingrowth are already endowed with the apparatus for action potential-induced, Ca(2+)-sensitive (exocytotic) ACh release; (2) that, in contrast, the expression of presynaptic muscarinic autoreceptors on these cholinergic axon terminals is delayed; and (3) that autoinhibition due to endogenous ACh develops even later, probably when the density of presynaptic terminals in the hippocampus and hence, the concentration of released ACh has reached a suprathreshold value.  相似文献   
100.
A 66-year-old woman was admitted because of postmenopausal vaginal bleeding. Diagnostic workup revealed a poorly differentiated endometrial adenocarcinoma. A total abdominal hysterectomy and bilateral salpingo-oophorectomy was carried out (FIGO stage Ia, G3). One and a half years later she developed a solitary humeral metastasis which was treated by local radiotherapy and progesterone acetate. Because osseous metastases in endometrial adenocarcinoma are rare, the literature is reviewed. In analogy to the treatment of pulmonary metastases the option of disarticulation of the patient's arm is discussed.  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