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   27522篇
  免费   1293篇
  国内免费   156篇
耳鼻咽喉   224篇
儿科学   483篇
妇产科学   265篇
基础医学   3102篇
口腔科学   782篇
临床医学   1797篇
内科学   6797篇
皮肤病学   532篇
神经病学   1928篇
特种医学   1280篇
外科学   4870篇
综合类   126篇
一般理论   1篇
预防医学   927篇
眼科学   739篇
药学   2116篇
中国医学   32篇
肿瘤学   2970篇
  2023年   131篇
  2022年   307篇
  2021年   523篇
  2020年   322篇
  2019年   413篇
  2018年   522篇
  2017年   395篇
  2016年   503篇
  2015年   515篇
  2014年   621篇
  2013年   838篇
  2012年   1341篇
  2011年   1481篇
  2010年   876篇
  2009年   714篇
  2008年   1341篇
  2007年   1454篇
  2006年   1483篇
  2005年   1393篇
  2004年   1340篇
  2003年   1186篇
  2002年   1228篇
  2001年   943篇
  2000年   961篇
  1999年   841篇
  1998年   350篇
  1997年   267篇
  1996年   288篇
  1995年   194篇
  1994年   181篇
  1993年   159篇
  1992年   554篇
  1991年   509篇
  1990年   497篇
  1989年   491篇
  1988年   428篇
  1987年   421篇
  1986年   415篇
  1985年   412篇
  1984年   252篇
  1983年   192篇
  1982年   102篇
  1981年   95篇
  1979年   188篇
  1978年   113篇
  1977年   105篇
  1975年   93篇
  1973年   97篇
  1970年   111篇
  1969年   93篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Excretion of 1,2,4-benzenetriol in the urine of workers exposed to benzene   总被引:5,自引:0,他引:5  
Urine samples were collected from 152 workers (64 men, 88 women) who had been exposed to benzene, 53 workers (men only) exposed to a mixture of benzene and toluene, and 213 non-exposed controls (113 men, 100 women). The samples were analysed for 1,2,4-benzentriol (a minor metabolite of benzene) by high performance liquid chromatography. The time weighted average solvent exposure of each worker was monitored by diffusive sampling technique. The urinary concentration of 1,2,4-benzentriol related linearly to the intensity of exposure to benzene both in men and women among workers exposed to benzene, and was suppressed by toluene co-exposure among male workers exposed to a mixture of benzene and toluene. A cross sectional balance study in men at the end of the shift of a workday showed that only 0.47% of benzene absorbed will be excreted into urine as 1,2,4-benzenetriol, in close agreement with previous results in rabbits fed benzene. The concentration of 1,2,4-benzenetriol in urine was more closely related to the concentration of quinol than that of catechol. The fact that phenol and quinol, but not catechol, are precursors of 1,2,4-benzentriol in urine was further confirmed by the intraperitoneal injection of the three phenolic compounds to rats followed by urine analysis for 1,2,4-benzenetriol.  相似文献   
82.
83.
A Usui  K Fujita  M Imaizumi  T Abe  K Inoue  S Matsumoto  K Kato 《Gan no rinsho》1987,33(14):1763-1770
The serum concentrations of both CK-BB and NSE in patients with various lung carcinoma have been determined by the enzyme immunoassay. Serum CK-BB levels were found to be significantly increased (less than 1.0 ng/ml) in patients with a small cell carcinoma (51 cases, 74.5%), adenocarcinoma (77 cases, 36.5%), and a squamous cell carcinoma (68 cases, 39.7%). The serum NSE levels also were increased (less than 6.0 ng/ml) in cases of small cell carcinoma (72.5%), adenocarcinoma (27.3%), and squamous cell carcinoma (26.5%). Since the serum concentrations of bos CK-BB and NSE changed in parallel with the clinical course, they may be useful biomarkers for monitoring the clinical course of patients with lung cancer, especially in cases of small cell carcinoma.  相似文献   
84.
The blocking effects of complement-dependent sperm immobilizingantibodies in the sera of infertile women and monoclonal antispermantibodies against humans and mice on fertilization were investigated.The hemizona assay (HZA) and sperm penetration assay (SPA) wereused to study the inhibitory effects of sera from 22 infertilepatients positive for sperm immobilizing antibodies. Use ofthese tests allowed us to differentiate whether the antibodyblocked sperm—zona pellucida tight binding and/or spermpenetration into the ooplasm. The zona pellucida penetrationassay (ZPA) was also used to study the effects of four monoclonalantibodies (mAbs) on human sperm penetration into the zona pellucida.Seven mAbs against murine spermatozoa were tested for theirinhibitory effects on in-vitro fertilization (IVF) and HZA inmice. Of 22 patient sera with sperm immobilizing antibodies,21 (95.5%) inhibited HZA attachment and penetration, whereasthis did not occur in any of 13 patient sera without these antibodies.However, 19 of 22 (86.4%) patient sera with sperm immobilizingantibodies and eight of 13 (61.5%) patient sera without theseantibodies inhibited the SPA. Two (2C6, 1G12) of four mAbs againsthuman spermatozoa showed strong inhibitory effects in all theassays (HZA, ZPA and SPA). One mAb (3B10) did not inhibit HZAbut blocked ZPA and SPA. Another mAb (H6-3C4) seemed to haveno inhibitory effects on fertilization. Two (Vx 5 and Vx 8)of seven mAbs against murine spermatozoa inhibited IVF in micebut did not block mouse HZA. These findings suggest that antispermantibodies block fertilization at specific stages. Some of themmay inhibit sperm capacitation and thus prevent all processesof fertilization that follow. Some other antibodies may notaffect capacitation and sperm binding to zona pellucida butinhibit the acrosome reaction, followed by the blocking of spermpenetration through zona pellucida and ooplasm.  相似文献   
85.
Sultamicillin fine granules were administered orally to 21 patients with impetigo contagiosa and 1 patient with erysipelas, and its clinical efficacy and safety were assessed. The dosage was 10-30 mg/kg daily. Clinical efficacies of impetigo contagiosa were "excellent" in 20 cases and "fair" in 1 case, with an overall efficacy rate of 95%. The result of treatment in erysipelas was "good". Out of 19 strains of Staphylococcus aureus isolated from foci, 17 strains had high beta-lactamase activities. In these 17 strains, sensitivity to the drug was 2-32-fold higher than to ampicillin, and in 14 out of these 17 strains 4-8-fold higher sensitivity was noted. As side effects, mild diarrhea was seen in 2 patients, but those recovered spontaneously in 3-4 days without particular treatment.  相似文献   
86.
The radial forearm flap, or the forearm flap, is called "Chinese flap" for its development of the chinese doctors, and is originally designed for the correction to the post-burn contraction of the face and neck. The radial forearm flap is one of the fasciocutaneous flap, supplied by the radial artery, and transferred as a single-stage reconstruction micro-surgically. In oral and maxillofacial region, the deltopectral flap (D-P flap) and the pectralis major myocutaneous flap (P-M-M-C flap) are mainly used for the reconstruction. These flaps, however, are sometimes too bulky and limited to transfer, and more require two-stage operations. On the other hand, as the forearm flap being thin and pliable, some doctors use this flap micro-surgically at single-stage free flap reconstruction. Before two years, we have begun to transfer the radial forearm flap for the intra-oral reconstruction. The operation method is as follows. Design and Elevation of the Radial Forearm Flap 1. Using the ultrasonic doppler flow meter, the radial artery and the subcutaneous forearm veins are marked on the skin. 2. The flap is designed 20% larger according to the pattern to be reconstructed, with the distal section of the radial artery as an axis on the forearm and the median vein of forearm inclusively. 3. Before the operation, Allen test must be performed in order to determine whether the hand will survive without a radial arterial in-put. 4. The operation is performed with a arm tourniquet. The margin of the flap are incised down to the deep fascia, isolating and preserving the proximal subcutaneous veins as required.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
87.
The effect of aging on 11C-N-methylspiperone binding to living human striatum was demonstrated using positron emission tomography. The 11 normal volunteers (22 to 72 years old) participated in this study. The uptake of 11C-N-methylspiperone in the brain following intravenous injection was highest in the striatum in individual subject. And the uptake in the striatum only gradually increased until the end of the study. The uptake of 11C-N-methylspiperone in cerebellum peaked within 10 minutes following injection and then rapidly dropped. The association rate constant "k3" was calculated from the slope of the radioactivity-ratio of striatum to cerebellum versus the equivalent time. The equivalent time was calculated from the radioactivity of cerebellum as an input function. The exponential decrease of the k3 value with aging was observed. The k3 value of the youngest subject (22 years old, male) was 0.035/min, while that of the oldest one (72 years old, male) was found to be 0.020/min. These data suggested that the dopaminergic activity through D2 dopamine receptors reduces with aging in human striatum.  相似文献   
88.
89.
Traf6 is essential for murine tooth cusp morphogenesis.   总被引:5,自引:0,他引:5  
Ectodermal appendages such as skin, hair, teeth, and sweat glands are affected in patients with hypohidrotic (anhydrotic) ectodermal dysplasia (HED). It has been established that mutations in the tumor necrosis factor (TNF) superfamily of molecules, i.e., ectodysplasin (EDA), EDA receptor (EDAR), and EDAR-associated death domain (EDARADD; the intracellular adaptor for EDAR), are responsible for several forms of HED in humans and mice. We show here by in situ hybridisation that another TNF family (orphan) receptor, TROY (also known TAJ, TAJ-alpha, TRADE, and TNFRSF19), is strongly coexpressed with Edar in the epithelial enamel knot signalling centres that are believe to regulate cuspal morphogenesis during murine tooth development. Traf6 is known to function as an intracellular adaptor protein for Troy and examination of Traf6 mutant mice revealed abnormalities in molar teeth that are similar but more severe than those produced by mutations in Eda signalling molecules. This finding suggests that, in additional to ectodysplasin, another TNF pathway involving Troy/Traf6 is involved in molar tooth cusp formation and identifies an essential role for a Traf in tooth development. Developmental Dynamics 229:131-135, 2004.  相似文献   
90.
Hydroxyapatite (HAp) was synthesized in the presence of a variety of amino acids in order to investigate the effect of amino acid on the crystallinity and the solubility characteristics of HAp in the HAp-synthesizing condition. In the results of X-ray diffraction analysis, HAp synthesized in the presence of glycine (HAp-Gly), serine (HAp-Ser), aspartic acid (HAp-Asp) and glutamic acid (HAp-Glu) showed poor crystallinity compared with HAp synthesized in the absence of amino acid (HAp-con). The results of Fourier transform infrared spectroscopy suggested the adsorption of these amino acids on HAp. Scanning electron microphotographs showed that the size and morphology of HAp adsorbed amino acids changed significantly. Furthermore, the solubility of these HAps increased significantly compared to HAp-con, each differing in four amino acids. However, other amino acids did not affect the crystallinity and morphology of HAp and had no significant change in their solubility. Collectively, this study suggests that the crystallinity and the solubility of synthesized HAp are different owing to the variation of amino acids in the HAp synthesizing condition. It is expected that digestion-regulated HAp materials could be synthesized by using amino acid in their synthesizing condition.  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