全文获取类型
收费全文 | 11880篇 |
免费 | 493篇 |
国内免费 | 109篇 |
专业分类
耳鼻咽喉 | 194篇 |
儿科学 | 233篇 |
妇产科学 | 150篇 |
基础医学 | 1428篇 |
口腔科学 | 206篇 |
临床医学 | 613篇 |
内科学 | 3361篇 |
皮肤病学 | 191篇 |
神经病学 | 847篇 |
特种医学 | 537篇 |
外科学 | 1894篇 |
综合类 | 48篇 |
一般理论 | 5篇 |
预防医学 | 363篇 |
眼科学 | 276篇 |
药学 | 857篇 |
中国医学 | 33篇 |
肿瘤学 | 1246篇 |
出版年
2023年 | 72篇 |
2022年 | 117篇 |
2021年 | 206篇 |
2020年 | 100篇 |
2019年 | 148篇 |
2018年 | 192篇 |
2017年 | 184篇 |
2016年 | 239篇 |
2015年 | 226篇 |
2014年 | 298篇 |
2013年 | 401篇 |
2012年 | 649篇 |
2011年 | 692篇 |
2010年 | 376篇 |
2009年 | 350篇 |
2008年 | 663篇 |
2007年 | 730篇 |
2006年 | 746篇 |
2005年 | 733篇 |
2004年 | 729篇 |
2003年 | 708篇 |
2002年 | 749篇 |
2001年 | 242篇 |
2000年 | 258篇 |
1999年 | 263篇 |
1998年 | 204篇 |
1997年 | 135篇 |
1996年 | 126篇 |
1995年 | 101篇 |
1994年 | 101篇 |
1993年 | 119篇 |
1992年 | 170篇 |
1991年 | 164篇 |
1990年 | 153篇 |
1989年 | 135篇 |
1988年 | 114篇 |
1987年 | 105篇 |
1986年 | 104篇 |
1985年 | 73篇 |
1984年 | 69篇 |
1983年 | 59篇 |
1982年 | 42篇 |
1981年 | 35篇 |
1980年 | 29篇 |
1979年 | 48篇 |
1978年 | 29篇 |
1972年 | 23篇 |
1971年 | 23篇 |
1969年 | 28篇 |
1966年 | 29篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Keiko Wakui Toshiro Nishida Jun-ichiro Masuda Takeshi Itoh Daisuke Katsumata Tsutomu Ohno Yoshimitsu Fukushima 《Journal of human genetics》1991,36(2):149-153
We report a malformed female infant withde novo interstitial deletion of 4q[46,XX,del(4)(q27q28.2)]. The MN blood type analysis of the family members showed that the patient had an intact blood group-MN locus. The locus of the gene responsible for the MN antigen activity is confined to a 4q28.2–4q31.1 segment on the basis of the result of this patient and the previous mapping data. 相似文献
42.
One of the most common chemicals that behaves as an endocrine disruptor is the compound 4,4′-isopronylidenediphenol, called bisphenol-A. In the previous study, we reported that exposure to bisphenol-A induced the abnormality of dopamine receptor functions in the mouse limbic area, resulting in a supersensitivity of drugs of abuse-induced pharmacological actions. The present study was undertaken to investigate whether prenatal and neonatal exposures to bisphenol-A could alter other behavioral abnormalities such as anxiogenic behavior, motor learning behavior, or memory. In the present study, adult female mice were chronically treated with bisphenol-A-admixed powder food from mating to weaning. All experiments were performed using male pups. Here we found that prenatal and neonatal exposures to bisphenol-A failed to induce anxiogenic effects and motor-learning impairment using the light-dark test, elevated plus maze test, and rota-rod test. On the other hand, we found that prenatal and neonatal exposures to bisphenol-A induced the memory impairment using the step-through passive avoidance test. Immunohistochemical study showed the dramatic reduction in choline acetyltransferase-like immunoreactivity, which is a marker of acetylcholine (ACh) production, in the hippocampus of mice prenatally and neonatally exposed to bisphenol-A. These results suggest that chronic exposures to bisphenol-A could induce the memory impairment associated with the reduction in ACh production in the hippocampus. 相似文献
43.
Phylogenetic association of Pneumocystis carinii with the 'Rhizopoda/Myxomycota/Zygomycota group' indicated by comparison of 5S ribosomal RNA sequences 总被引:14,自引:0,他引:14
The cytoplasmic 5S ribosomal RNA (5S rRNA) sequence from Pneumocystis carinii was determined. A sequence comparison matrix of 382 eukaryote 5S rRNA sequences and an evolutionary tree were constructed to establish the phylogenetic position of Pneumocystis. The data suggest that Pneumocystis is associated with the Rhizopoda/Myxomycota/Zygomycota group (= 'Protista fungi') but not with common fungi, such as Ascomycota or Basidiomycota, nor with other protozoa. 相似文献
44.
Kenji Kashima Shigeo Yokoyama Tsutomu Daa Iwao Nakayama Torn Iwaki 《Virchows Archiv : an international journal of pathology》1997,430(4):333-338
The influence of free radicals on apoptosis was studied in the human heart; 45 autopsy cases were examined by the nick end labelling method (NELM) that detects DNA fragmentation. Immunostaining for copper-zinc superoxide dismutase (CuZn-SOD) and tissue transglutaminase (tTG) induced frequently during apoptosis were also studied. Positive immunoreaction for tTG was detected in mucinous degeneration of myocardial cells; these same cells were also positive for CuZn-SOD but negative for NELM. Myocardial cells showing basophilic alterations after haematoxylin and eosin staining were also positive for CuZn-SOD but negative for the other markers examined. Positive nuclear reaction by NELM was only observed in myocardial cells showing contraction band necrosis or irregularly shaped nuclei surrounding recent or long-standing infarcted foci. In these the other two markers were negative. Since mucinous degeneration lacks the distinguishing morphological features of apoptosis, immunoreactive tTG in this lesion may not imply that the cells are undergoing apoptosis. tTG can be induced in non-apoptotic conditions and may not be involved in apoptosis induced by infarction. Histological disassociation between CuZn-SOD expression and apoptosis suggests the possibility of a cytoprotective role played by endogenous CuZn-SOD against free radical generation in the human heart. 相似文献
45.
Shiro Kobayashi Tsutomu Mizutani Takeo Saegusa 《Macromolecular chemistry and physics.》1984,185(3):441-451
2-(Hydroxyphenyl)-2oxazolines(p- and n-isomers 1a and 1b ) were used for the synthesis of various polymers. Cationic polymerization of 2-methyl-2-oxazoline initiated with the N-methyl 2 -oxazolinium species 3 , Derived from 1 , Gave telechelic poly(N-acetylethylenimine) ( 5 ) having a hydroxyl group of different reactivity at both ends. Anionic polymerization of ethylene oxide induced by the lithium salt of 1, 7 , produced a poly(ethylene oxide) macromer, 9 , having a ringopening polymerizable 2-oxazoline group. The copolymer from 9 and 2-phenyl-2oxazoline, 10 , has been shown to have good properties as a nonionic polymeric surfactant in which the N-benzoylethylenimine main-chain behaves as a lipophilic group whereas the oxyethylene graftchains act as a hydrophilic group. Di-salt 11 derived from 1 was polymerized to give polymide 13 (“amphi-ionic polymerization”). 相似文献
46.
47.
Technology developed to allow recovery of cells without enzyme treatment, involving a dish grafted with a thermoreactive polymer gel of poly-N-isopropylacrylamide (PIPAAm), was found to significantly enhance gap junctional intercellular communication (GJIC) in normal human dermal fibroblasts (NHDF cells). NHDF cells were cultured for 4 days on PIPAAm-grafted dishes irradiated with various doses of electron beams, and GJIC was assayed by the scrape-loading dye transfer method. The area of dye transfer was greater in the PIPAAm-grafted dishes than in the control culture dishes, indicating that the PIPAAm-grafted dishes enhanced the GJIC of NHDF cells. Connexin-43 (Cx43) expression was analyzed because Cx43 is considered to be a main component of the gap junctional channel. PIPAAm-grafted dishes irradiated with 100, 250, or 500 kGy of electron beams showed significantly enhanced expression of Cx43-NP, Cx43-P1, and especially Cx43-P2. Enhanced expression of Cx43-P2, a functional transmembrane protein, may be related to the promotion of GJIC. These results suggest that the PIPAAm-grafted dish not only enables the enzyme-free recovery of a cell monolayer for use in the construction of a three-dimensional artificial tissue, but also significantly contributes to the enhancement of GJIC, which may partly promote tissue strength on the surface of the PIPAAm-grafted dish. 相似文献
48.
Teiji Tsuruta Tsutomu Makimoto Yuzaburo Nakayama 《Macromolecular chemistry and physics.》1966,90(1):12-25
Stereoregulating behaviour of organoalkali and organoalkaline earth metal compounds in methyl methacrylate (MMA) polymerization has been studied. Low temperature and polar solvents such as tetrahydrofuran (THF) favour formation of syndiotactic polymer when lithium and magnesium ketyls are used as catalysts. Whereas isotactic polymer is obtained with sodium ketyl even in THF at ?70°C. Lithium aluminum hydride (LiAlH4) gave almost complete isotactic polymer in high conversion in diethyl ether or toluene even at low temperature, and lithium aluminum tetraethyl (LiAlEt4), on the other hand, gave very highly syndiotactic polymer under the same conditions. The solvent, besides, showed very important role in stereoregulation, that is, LiAlH4 could give syndiotactic polymer in a polar solvent at low temperature. Polymer structure was analyzed by NMR- and IR-spectroscopy. The electrical conductivities of these catalyst systems were measured and there was found a parallelism between those values and stereoregularities of polymers obtained by the respective catalyst systems. 相似文献
49.
Identity of hemolysins produced by Vibrio cholerae non-O1 and V. cholerae O1, biotype El Tor. 总被引:8,自引:11,他引:8
K Yamamoto Y Ichinose N Nakasone M Tanabe M Nagahama J Sakurai M Iwanaga 《Infection and immunity》1986,51(3):927-931
Hemolysins purified from non-O1 Vibrio cholerae (non-O1 hemolysin) and a Vibrio cholerae O1, biotype El Tor (El Tor hemolysin) were investigated for their homology. The hemolysins were isolated from the culture supernatant fluids by ammonium sulfate precipitation and gel filtration on Sephadex G-100 columns. The purified hemolysins gave single bands with an identical mobility on conventional polyacrylamide gel disc electrophoresis. The molecular weights of the non-O1 and El Tor hemolysins were estimated to be about 60,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and the amino acid compositions of the hemolysins were very similar. The specific activities of the hemolysins were identical, and both hemolysins were neutralized to the same extent with antisera against the homologous and heterologous hemolysins. Ouchterlony double immunodiffusion tests with both hemolysins and antihemolysin serum gave a common (fused) precipitin line. These data indicate that the non-O1 hemolysin is biologically, physicochemically, and immunologically indistinguishable from the El Tor hemolysin. 相似文献
50.
Tsutomu Okamoto Keishi Ueda Takeshi Kambara Tatsuo Kutsuna 《Pathology international》1986,36(8):1109-1122
In order to why polymorphonuclear leukocytes (PMNs) are predominant and mononuclear leukocytes (MNLs) are few in rheumatoid synovial fluids, chemotactic factor(s) for PMNs and MNLs were studied in the synovial fluids of rheumatoid arthritis (RA-SF) and osteoarthritis (OA-SF) using both Boyden's and agarose methods. The RA-SF showed strong chemotactic activity for human peripheral blood PMNs compared with non-rheumatoid OA-SF. The chemotactic activity for PMNs was well correlated with the number of PMNs in RA-SF, suggesting that it was a natural mediator for PMN emigration into rheumatoid joint cavity. The major chemotactic factor for PMN in RA-SF was of apparent molecular weight of 14,000 and its activity was suppressed to less than 10 percent by anti-C5a antibody, but it failed to show any anaphylatoxin activity which was an attribute of C5a. It was, therefore, suggested to be C5a-like molecule but not C5a itself. The possibility that the factor may be a C5a des-Arg was discussed. On the contrary, the chemotactic activity for MNLs was not found neither in RA-SF nor OA-SF. These findings may explain the fact that PMNs are predominant in rheumatoid synovial fluids. 相似文献