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   774541篇
  免费   54929篇
  国内免费   1461篇
耳鼻咽喉   9849篇
儿科学   25352篇
妇产科学   19322篇
基础医学   120247篇
口腔科学   21812篇
临床医学   71442篇
内科学   147175篇
皮肤病学   17071篇
神经病学   55845篇
特种医学   28127篇
外国民族医学   83篇
外科学   114105篇
综合类   15962篇
现状与发展   2篇
一般理论   238篇
预防医学   57903篇
眼科学   17960篇
药学   59226篇
  3篇
中国医学   2455篇
肿瘤学   46752篇
  2021年   6370篇
  2019年   6476篇
  2018年   9079篇
  2017年   7024篇
  2016年   7895篇
  2015年   8663篇
  2014年   11845篇
  2013年   17900篇
  2012年   24117篇
  2011年   25345篇
  2010年   14833篇
  2009年   13878篇
  2008年   23512篇
  2007年   25313篇
  2006年   25595篇
  2005年   24153篇
  2004年   23524篇
  2003年   22416篇
  2002年   21863篇
  2001年   37835篇
  2000年   38408篇
  1999年   31759篇
  1998年   8828篇
  1997年   7474篇
  1996年   7626篇
  1995年   7334篇
  1994年   6773篇
  1993年   6247篇
  1992年   24125篇
  1991年   24013篇
  1990年   23370篇
  1989年   23023篇
  1988年   20899篇
  1987年   20302篇
  1986年   19388篇
  1985年   18245篇
  1984年   13559篇
  1983年   11519篇
  1982年   6607篇
  1979年   12185篇
  1978年   8710篇
  1977年   7347篇
  1976年   7041篇
  1975年   7644篇
  1974年   8960篇
  1973年   8528篇
  1972年   8030篇
  1971年   7460篇
  1970年   7146篇
  1969年   6581篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
A novel approach for modelling the biological activity of organic molecules, which requires simultaneous consideration of the influence of all factors (topological, steric, hydrophobic, and electronic) that determine the bioactivity, is used to study the interaction of a series of benzoates with anti-p-(p'-azophenylazo)benzoate antibody. The results obtained suggest that this biological interaction proceeds by a two-step stereospecific mechanism. The first step requires a geometrical correspondence between the benzoates and the cavity in the biomacromolecule, which enables the pharmacophore to come into close contact with the receptor. The second step is the orbitally controlled electronic interaction between the active parts of the benzoates and the antibody. The electronic interaction results from pi-charge transfer from the pharmacophore to the biomacromolecule and from the formation of pi-complexes. A proposed mathematical model for this biological interaction exhibits some statistical advantages over existing models.  相似文献   
92.
93.
94.
Bromocriptine (0.5 mg/kg) and apomorphine (0.03 mg/kg) exert moderate aphrodisiac effect in sexually sluggish rats. This effect appears rapidly and reaches its peak within 24 h. Amphetamine (2 mg/kg) acts similarly but with a more rapid onset and offset of the effect. A single dose of (-)deprenyl, a selective inhibitor of MAO-B, exerts a much more potent effect in this test.  相似文献   
95.
96.
We review evidence suggesting that deaf speakers do not move their articulators toward the following open posture throughout closure and report results from a preliminary cinefluorographic study. Two prelingually deaf and two hearing speakers produced two different strings of alternating heterogeneous monosyllables as though speaking in time with a metronome (the so-called P-center task). Events traditionally associated with vowel production appeared evenly timed throughout the productions, and, in general, the deaf speakers performed similarly to the hearing speakers. We relate the results to Fowler's (1983) interpretation of the P-center phenomenon as an indicant of continuous vowel production.  相似文献   
97.
Biopsies from the diseased bones of patients with familial expansile osteolysis (FEO) were examined by light and electron microscopy. Focal concentrations of multinuclear osteoclasts were present, and these contained viral-like microcylindrical inclusions which appeared exclusive to their nuclei. No consistent relationship was found between osteoclast size and the number of osteoclast nuclei containing microcylindrical inclusions. Quantitative histomorphometry showed evidence of increased bone remodelling with high bone cell densities and a decrease of the reversal period in bone remodelling. The lesions contained prominent woven bone and fibrovascular tissue, together with mononuclear cells and adipocytes. Little bone was found in the most radiolucent lesions, which were almost totally occupied by adipocytes and fibrovascular tissue. Serology did not reveal any significant differences between the viral antibody titres of patients and their age- and sex-matched controls. The present study suggests that intranuclear viral-like microcylindrical inclusions of osteoclasts are not a specific feature of Paget's disease, and are found in other disorders of osteoclast function, including pycnodysostosis, osteopetrosis, giant cell tumours, and familial expansile osteolysis.  相似文献   
98.
A tracer kinetic procedure was developed for the measurement of monoamine oxidase type B (MAO-B) activity using L-[11C]deprenyl and positron emission tomography (PET). The kinetic model consisted of two tissue compartments with irreversible binding to the second compartment (three rate constants). In addition, a blood volume component was included. Special attention was given to the accurate measurement of the plasma and whole blood input functions. The method was applied to the measurement of the dose-response curve of a reversible MAO-B inhibitor (Ro 19-6327). From the results, it followed that the rate constant for irreversible binding (k3) appeared to be a better index of MAO-B activity than the net influx constant Ki. Furthermore, regional analysis demonstrated that Ki, but not k3, was flow dependent. This implies that full kinetic analysis is required for an accurate assessment of MAO-B activity.  相似文献   
99.
The expression of two heat shock proteins, HSP72 and p57, in addition to ubiquitin, has been studied immunocytochemically in nine amyotrophic lateral sclerosis (ALS) cases and 10 age-matched controls. HSP72 and p57 antibodies did not identify the characteristic ubiquitin-immunoreactive inclusions present in anterior horn cells in ALS spinal cord. Antibodies to HSP72, but not to p57 or ubiquitin, strongly labelled structures corresponding to polyglucosan bodies in spinal grey matter. Such immunoreactive profiles were more abundant in ALS cases, although they were also present in control material. They were sometimes identified by haematoxylin and eosin and periodic acid Schiff reaction, but were not labeled by phosphotungstic acid haematoxylin or by antibodies to glial fibrillary acidic protein. Although ubiquitin, HSP72 and p57 are stress-induced proteins, they are expressed differently and might therefore have different significance in neuronal degeneration.  相似文献   
100.
Bronchoalveolar lavage fluid neutrophils were studied by the cytologic methods in 58 patients with chronic bronchitis, 63 ones with bronchiectasis, and 8 normal controls. The study included cytospectrophotometry of myeloperoxidase and alkaline phosphatase activity and estimation of active oxygen-producing cells in the NBT test. Neutrophilic functional activity was different in the patients with chronic bronchitis and bronchiectasis. Neutrophilic myeloperoxidase and alkaline phosphatase activities were lower in the patients with chronic bronchitis than in those with bronchiectasis, whereas the counts of cells active in the NBT test were low in both patient populations.  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