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   20516篇
  免费   1304篇
  国内免费   38篇
耳鼻咽喉   128篇
儿科学   689篇
妇产科学   709篇
基础医学   2749篇
口腔科学   269篇
临床医学   3392篇
内科学   3871篇
皮肤病学   212篇
神经病学   2042篇
特种医学   308篇
外科学   1574篇
综合类   271篇
一般理论   31篇
预防医学   2819篇
眼科学   151篇
药学   1207篇
中国医学   13篇
肿瘤学   1423篇
  2023年   88篇
  2022年   143篇
  2021年   337篇
  2020年   214篇
  2019年   378篇
  2018年   397篇
  2017年   282篇
  2016年   358篇
  2015年   412篇
  2014年   607篇
  2013年   971篇
  2012年   1399篇
  2011年   1404篇
  2010年   773篇
  2009年   763篇
  2008年   1379篇
  2007年   1350篇
  2006年   1359篇
  2005年   1389篇
  2004年   1321篇
  2003年   1298篇
  2002年   1260篇
  2001年   182篇
  2000年   166篇
  1999年   205篇
  1998年   255篇
  1997年   222篇
  1996年   182篇
  1995年   194篇
  1994年   171篇
  1993年   170篇
  1992年   161篇
  1991年   143篇
  1990年   133篇
  1989年   127篇
  1988年   127篇
  1987年   131篇
  1986年   106篇
  1985年   105篇
  1984年   143篇
  1983年   101篇
  1982年   129篇
  1981年   113篇
  1980年   111篇
  1979年   77篇
  1978年   73篇
  1977年   53篇
  1976年   53篇
  1975年   47篇
  1974年   50篇
排序方式: 共有10000条查询结果,搜索用时 968 毫秒
91.
This study investigated the effects of neurokinin A (NKA) on cholinergic neural responses in human bronchus. NKA (0.1 nM) did not alter the contractile response to submaximal electrical field stimulation. However, K+ channel blockade with 4-aminopyridine (4-AP) (0.1 mM) potentiated the response to electrical field stimulation (to 182 ± 25% of control, n = 4, P < 0.05) and subsequent addition of NKA in the presence of 4-AP produced further potentiation (to 123 ± 6% of the response to 4-AP n = 4, P < 0.05). Neither 4-AP (0.01 or 0.1 mM) nor NKA in the presence of 4-AP potentiated the actions of exogenous acetylcholine but in these experiments 4-AP itself produced a marked direct contractile response. Thus NKA in the presence of K+ channel blockade potentiates cholinergic neural response in human bronchus and this occurs at a prejunctional site.  相似文献   
92.
93.
Part II of a three-part report of the National Birth Center Study describes care provided to 11,814 women and their newborns during and after labor and delivery until they were transferred or discharged from the birth centers. There were few low birth weight or preterm or postterm births, but more macrosomic babies than among all U.S. births during the same time period. Certified nurse-midwives provided most of the intrapartum care, which is described in the context of medically recommended standards and data that describe care provided to low-risk women giving birth in U.S. hospitals. Birth center care deviated from typical hospital care in several ways. Birth center clients were much less likely to receive central nervous system depressants, anesthesia, continuous electronic fetal monitoring, induction and/or augmentation of labor, intravenous infusions, amniotomies, or episiotomies, and they had relatively few vaginal examinations. They were more likely to eat solid food during labor and to take showers and/or baths Nulliparity was strongly associated with longer first stage labors and longer labor was associated with more frequent use of many kinds of interventions. Infant birth weight, mother's position during delivery, and forceps- or vacuum-assisted deliveries are examined in relation to episiotomies and lacerations and tears.  相似文献   
94.
We have experienced a coagulation factor VIII-deficient patient whose plasma has normal protein S (PS) activity and masses of free PS and its bound form in complex with C4b-binding protein (C4BP). Although the patient's plasma showed a normal ratio of free PS to PS-C4BP complex in the presence of 5 mM EDTA, the plasma gave an abnormally retarding major C4BP peak together with a major PS peak in the crossed immunoelectrophoresis (CIE) in the presence of 2 mM CaCl2. It was revealed that the major peak was formed by a mixture of PS-C4BP complex and free form. The addition of normal human plasma (NHP) to the patient's plasma inhibited the retardation of the major PS-C4BP complex. These suggest that the patient's plasma lacks some component(s) to inhibit Ca2+-dependent association of PS with C4BP.  相似文献   
95.

Purpose  

A new job-specific test for fire fighters, the stair-climb test (FFstair-climb) was evaluated for reproducibility and validity for use in future workers’ health surveillance.  相似文献   
96.
BACKGROUND: We are interested in identifying susceptibility genes that predispose subjects to attempted suicide. METHODS: We conducted a secondary analysis of genome-wide linkage data from 162 bipolar pedigrees that incorporated attempted suicide as a clinical covariate. RESULTS: The strongest covariate-based linkage signal was seen on 2p12 at marker D2S1777. The logarithm of odds (LOD) score at marker D2S1777 rose from 1.56 to 3.82 after inclusion of the suicide covariate, resulting in significant chromosome-wide empirically derived p-values for the overall linkage finding (p = .01) and for the change in LOD score after the inclusion of the covariate (p = .02). CONCLUSIONS: The finding on chromosome 2 replicates results from two previous studies of attempted suicide in pedigrees with alcohol dependence and in pedigrees with recurrent early-onset depression. Combined, these three studies provide compelling evidence for a locus influencing attempted suicide on 2p12.  相似文献   
97.
98.
99.
100.
Background: The Farnsworth D15 test is designed to categorise colour vision deficiency as severe or moderate. The level of difficulty of the test was set so that those who passed it should be able to recognise surface colour codes, such as those used for electrical wiring. The test is widely used to provide advice to patients with abnormal colour vision and is often used for occupational selection when reliable recognition of surface colour codes is required. However, there has been only one previous study of the correlation between performance at the D15 test and the naming of surface colour codes and there has been no study of whether a person who passes the D15 can reliably name surface colours. Methods: One hundred and two people aged 11 to 65 years with abnormal colour vision were recruited from consecutively presenting optometric patients and were asked to name the colours of fabric, paint and cotton thread samples. There were 10 colours in each class of material and the samples were presented in a large (five to 10 degree angular subtense) and small size (2.5 deg and a single thread). The errors made were compared to those made by an age‐matched control group of equal size with normal colour vision. Results: The correlations between the Farnsworth D15 colour confusion index and colour naming errors were 0.62 for the large stimuli and 0.73 for the small stimuli. Its sensitivity and specificity identifymg those who made more errors than the worst performing colour normal person were 0.80 and 0.69 (large stimuli) and 0.75 and 0.71 (small stimuli). A Nagel anomaloscope range of less than 35 scale units provides essentially the same sensitivity and specificity. Conclusions: About 40 per cent of those with abnormal colour vision can name the main colours correctly under good visibility conditions. The D15 test is an imperfect predictor of those who can name surface colour codes correctly but it does provide useful information for general counselling. It is not suitable as a single test for occupational selection because it will pass 20 per cent who cannot name surface colours correctly and fail 30 per cent who can. In occupations in which recognition of surface colour codes is of critical importance, it may be best not to select people with abnormal colour vision because of the lack of a colour vision test that is a perfect predictor of the ability to recognise surface colours.  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